22 Radio Receiver

Projects for the Evil

Genius

Evil Genius Series

Bionics for the Evil Genius: 25 Build-it-Yourself Projects

Electronic Circuits for the Evil Genius: 57 Lessons with Projects Electronic Gadgets for the Evil Genius: 28 Build-it-Yourself Projects Electronic Games for the Evil Genius

Electronic Sensors for the Evil Genius: 54 Electrifying Projects 50 Awesome Auto Projects for the Evil Genius

50 Model Rocket Projects for the Evil Genius

Mechatronics for the Evil Genius: 25 Build-it-Yourself Projects MORE Electronic Gadgets for the Evil Genius: 40 NEW Build-it-Yourself Projects 101 Spy Gadgets for the Evil Genius

123 PIC® Microcontroller Experiments for the Evil Genius

123 Robotics Experiments for the Evil Genius

PC Mods for the Evil Genius

Solar Energy Projects for the Evil Genius

25 Home Automation Projects for the Evil Genius

51 High-Tech Practical Jokes for the Evil Genius

22 Radio Receiver

Projects for the

Evil Genius

TOM PETRUZZELLIS

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DOI: 10.1036/0071489290

About the Author

About the Author

Thomas Petruzzellis is an electronics engineer

including an earlier volume in this series,

currently working at the geophysical laboratory at

Electronic Sensors for the Evil Genius. He is also

the State University of New York, Binghamton.

the author of Create Your Own Electronics

Also an instructor at Binghamton, with 30 years’

Workshop; STAMP 2 Communications and Control

experience in electronics, he is a veteran author

Projects; Optoelectronics, Fiber Optics, and Laser

who has written extensively for industry

Cookbook; Alarm, Sensor, and Security Circuit

publications, including Electronics Now, Modern

Cookbook, all from McGraw-Hill. He lives in

Electronics, QST, Microcomputer Journal, and

Vestal, New York.

Nuts & Volts. Tom wrote five previous books,

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This page intentionally left blank

Acknowledgments

Acknowledgments

I would like to thank the following people and

Charles Higgins/Tennessee State University

companies listed below for their help in making

Fat Quarters Software

this book possible. I would also like to thank

Radio-Sky Publishing

senior editor Judy Bass and all the folks at

McGraw-Hill publications who had a part in

Ramsey Electronics

making this book possible. We hope the book will

Vectronics, Inc

inspire both radio and electronics enthusiasts to

Russell Clift

build and enjoy the radio projects in this book.

Todd Gale

Eric Vogel

Richard Flagg/RF Associates

Wes Greenman/University of Florida

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

This page intentionally left blank

For more information about this title, click here

Project 10 Experiments

Contents

Acknowledgments

vii

13 Active and Passive Aircraft Band

140

Introduction

xi

Receivers

14 VLF or Very Low Frequency

153

1 Radio Background and History

1

Radio Receiver

2 Identifying Components and Reading

12

15 Induction Loop Receiving System

165

Schematics

16 Lightning Storm Monitor

175

3 Electronic Parts Installation and

25

17 Ambient Power Receiver

186

Soldering

18 Earth Field Magnetometer Project

192

4 AM, FM, and Shortwave Crystal

39

Radio Projects

19 Sudden Ionospheric Disturbance

203

(SIDs) Receiver

5 TRF AM Radio Receiver

49

20 Aurora Monitor Project

212

6 Solid-State FM Broadcast Receiver

59

21 Ultra-Low Frequency (ULF) Receiver

224

7 Doerle Single Tube Super-Regenerative 70

Radio Receiver

22 Jupiter Radio Telescope Receiver

233

8 IC Shortwave Radio Receiver

81

23 Weather Satellite Receiver

246

9 80/40 Meter Code Practice Receiver

94

24 Analog to Digital Converters (ADCs)

262

10 WWV 10 MHz “Time-Code” Receiver

104

Appendix: Electronic Parts Suppliers

273

11 VHF Public Service Monitor

116

Index

277

(Action-Band) Receiver

12 6 & 2-Meter Band Amateur

127

Radio Receiver

ix

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Introduction

22 Radio Receiver Projects for the Evil Genius

In Chapter 5, you will learn how AM radio is

was created to inspire readers both young and old

broadcast, from a radio station to a receiver in your

to build and enjoy radio and receiver projects, and

home, and how to build your own TRF or Tuned

perhaps propel interested experimenters into a

Radio Frequency AM radio receiver. In Chapter 6,

career in radio, electronics or research. This book

we will discover how FM radio works and how to

is for people who are interested in radio and

build an FM radio with an SCA output for

electronics and those who enjoy building and

commercial free radio broadcasts.

experimenting as well as those who enjoy research.

Chapter 7 will present the exciting world of

Radio encompasses many different avenues for

shortwave radio. Shortwave radio listening has a

enthusiasts to explore, from simple crystal radios to

large following and encompasses an entire hobby

sophisticated radio telescopes. This book is an

in itself. You will be able to hear shortwave

attempt to show electronics and radio enthusiasts that

stations from around the world, including China,

there is a whole new world “out there” to explore.

Russia, Italy, on your new shortwave broadcast

Chapter 1 will present the history and

receiver. Old time radio buffs will be interested in

background and elements of radio, such as

the single tube Doerle super-regenerative

modulation techniques, etc. Chapter 2 will help the

shortwave radio.

newcomers to electronics, identifying components

If you are interested in a portable shortwave

and how to look and understand schematics vs.

receiver that you could take on a camping trip,

pictorial diagrams. Next, Chapter 3 will show the

then you may want to construct the multi-band

readers how to install electronic components onto

integrated circuit shortwave radio receiver

circuit boards and how to correctly solder before

described in Chapter 8.

embarking on their new radio building adventure.

If you are interested in Amateur Radio or are

We will start our adventure with the simple

thinking of learning Morse code or want to

“lowly” crystal radio in Chapter 4. Generally

increase your code speed, you may want to

crystal radios are only thought of as simple AM

consider building this 80 and 40-meter code

radios which can only pickup local broadcast

receiver. This small lightweight portable receiver

stations. But did you know that you can build

can be built in a small enclosure and taken on

crystal radios which can pickup long-distance

camping trips, etc.

stations as well as FM and shortwave broadcasts

In Chapter 10, you will learn how to build and

from around the world? You will learn how to

use a WWW time code receiver, which can be used

build an AM, FM and shortwave crystal radio, in

to pick up time signal broadcast from the National

this chapter.

Institute of Standards and Technology (NIST) or

xi

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

National Atomic Time Clock in Boulder CO. Time

your results by feeding your recorded signal into a

signal broadcasts present geophysical and

sound card running an FFT program. Use your

propagation forecasts as well as marine and sea

computer to record and analyze these interesting

conditions. They will also help you set the time on

signals. There are many free programs available

your best chronometer.

over the Internet. An FFT audio analyzer program

With the VHF Public service receiver featured in

can display the audio spectrum and show you

Chapter 11, you will discover the high frequency

where the signals plot out in respect to frequency.

“action bands” which cover the police, fire, taxis,

If you are interested in weather, then you will

highway departments and marine frequencies. You

appreciate the Lightening to Storm Receiver in

will be able to listen-in to all the exciting

Chapter 16, which will permit you to “see” the

communications in your hometown.

approaching storm berfore it actually arrives. This

The 6-meter and 2-meter dual VHF Amateur

receiver will permit you to have advanced warning

Radio receiver in Chapter 12 will permit to

up to 50 miles or more away; it will warn you well

discover the interesting hobby of Amateur Radio.

in advance of an electrical storm, so you can

The 6-meter and 2-meter ham radio bands are two

disconnect any outdoor antennas.

of the most popular VHF bands for technician

The Ambient Power Module receiver project

class licensees. You may discover that you might

illustrated in Chapter 17, will allow to you pickup

just want to get you own ham radio license and

a broad spectrum of radio waves which get

talk to ham radio operators through local VHF

converted to DC power, and which can be used to

repeaters or to the rest of the world.

power low current circuits around your home or

Why not build an aircraft radio and listen-in to

office. This is a great project for experimentation

airline pilots talking from 747s to the control tower

and research. You can use it to charge cell phones,

many miles away. You could also build the passive

emergency lights, etc.

Air-band radio which you use to listen-in to your

Our magnetometer project shown in Chapter 18

pilot during your own flight. Passive aircraft radios

can be used to see the diurnal or daily changes in

will not interfere with airborne radio so they are

the Earth’s magnetic field, and you can record the

permitted on airplanes, without restriction. Check

result to a data-logger or recording multi-meter.

out these two receivers in Chapter 13.

If you are an avid amateur radio operator or

Chapter 14 will also show you how to build an

shortwave listener, you many want to build a SIDs

induction communication system, which will allow

receiver shown in Chapter 19. A SIDs receiver can

you to broadcast a signal around home or office

be used to determine when radio signals and/or

using a loop of wire, to a special induction

propagation is disturbed by solar storms. This

receiver. The induction loop broadcast system is a

receiver will quickly alert you to unfavorable radio

great aid to the hearing impaired, since it can

conditions. You can collect the receiver to your

broadcast to hearing aids as well.

personal computer’s sound card and use the data

The VLF, or “whistler” radio in Chapter 15, will

recorded to correlate radio propagation against

pickup very very low frequency radio waves from

storm conditions.

around the world. You will be able to listen to low

The Aurora receiver project in Chapter 20 will

frequency beacon stations, submarine

alert you, with both sound and meter display, when

transmissions and “whistlers” or the radio waves

the Earth’s magnetic increases just before an

created from electrical storms on the other side of

Aurora display is about to take place. UFO and

the globe. This project is great for research

Alien contact buffs can use this receiver to know

projects where you can record and later analyze

when UFOs are close by.

Introduction

xii

Introduction

For those interested in more earthly research

computer, and can be used for a research project to

projects, why not build your own ULF or ultra low

record and analyze these radio storm signals.

frequently receiver, shown in Chapter 21, which

Why not construct your own weather satellite

can be utilized for detecting low frequency wave

receiving station, shown in Chapter 23. This

generated by earthquakes and fault lines. With this

receiver will allow you to receive APT polar

receiver you will be able to conduct your own

satellites broadcasting while passing overhead. You

research projects on monitoring the pulse of the

can display the satellite weather maps on the

Earth. You can connect your ELF receiver to a

computer’s screen or save them later to show

data-logger and record the signals over time to

friends and relatives.

correlate your research with that of others.

Chapter 24 discusses different analog to digital

You can explore the heavens by constructing

converters which you can use to collect and record

your own radio telescope to monitor the radio

data from the different receiver projects.

signals generated from the planet Jupiter. This

radio receiver, illustrated in Chapter 22, will pick

We hope you will find the 22 Radio Projects for

up radio signals which indicate electrical and or

the Evil Genius a fun and thought-provoking book,

magnetic storms on the Jovian planet. The Radio

that will find a permanent place on your

Jupiter receiver can be coupled to your personal

electronics or radio bookshelf. Enjoy!

xiii

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22 Radio Receiver

Projects for the Evil

Genius

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Chapter 1

Radio Background and History

Electromagnetic energy encompasses an extremely wide

Joseph Henry, a Princeton University professor, and

frequency range. Radio frequency energy, both natural

Michael Faraday, a British physicist, experimented

radio energy created by lightning and planetary storms

separately with electromagnets in the early 1800s. They

as well as radio frequencies generated by man for

each arrived at the same observation: the theory that a

communications, entertainment, radar, and television

current in one wire can produce a current in another

are the topic of this chapter. Radio frequency energy,

wire, even at a distance. This phenomenon is called

or RF energy, covers the frequency range from the low

electromagnetic induction, or just induction. That is,

end of the radio spectrum, around l0 to 25 kHz, which

one wire carrying a current induces a current in a

is used by high-power Navy stations that communicate

second wire. So far, scientists knew that electricity

with submerged nuclear submarines, through the

and magnetism always seemed to affect each other at

familiar AM broadcast band from 550 to 1600 kHz.

right angles. However, a major discovery lay hidden

Next on the radio frequency spectrum are the shortwave

just beneath this seemingly simple concept of related

bands from 2000 kHz to 30,000 kHz. The next band of

perpendicularity, and its unveiling was one of the

frequencies are the very high frequency television

pivotal moments in modern science.

channels covering 54 to 2l6 MHz, through the very

The man responsible for the next conceptual

popular frequency modulation FM band from 88 to

revolution was the Scottish physicist James Clerk

l08 MHz. Following the FM broadcast band are aircraft

Maxwell (1831–1879), who “unified” the study of

frequencies on up through UHF television channels and

electricity and magnetism in four relatively tidy

then up through the radar frequency band of 1000 to

equations. In essence, what he discovered was that

1500 MHz, and extending through approximately

electric and magnetic fields were intrinsically related

300 gHz. See frequency spectrum chart in Figure 1-1.

to one another, with or without the presence of a

The radio frequency spectrum actually extends almost

conductive path for electrons to flow. Stated more

up to the lower limit of visible light frequencies.

formally, Maxwell’s discovery was this: a changing

electric field produces a perpendicular magnetic field,

and a changing magnetic field produces a perpendicular

Radio history

electric field. All of this can take place in open space,

the alternating electric and magnetic fields supporting

each other as they travel through space at the speed of

One of the more fascinating applications of electricity is

light. This dynamic structure of electric and magnetic

in the generation of invisible ripples of energy called

fields propagating through space is better known as an

radio waves. Following Hans Oersted’s accidental

electromagnetic wave.

discovery of electromagnetism, it was realized that

electricity and magnetism were related to each other.

Later, Heinrich Hertz, a German physicist, who is

When an electric current was passed through a conductor,

honored by our replacing the expression “cycles per

a magnetic field was generated perpendicular to the axis

second” with hertz (Hz), proved Maxwell’s theory

of flow. Likewise, if a conductor was exposed to a

between the years 1886 and l888. Shortly after that, in

change in magnetic flux perpendicular to the conductor,

1892, Eouard Branly, a French physicist, invented a

a voltage was produced along the length of that

device that could receive radio waves (as we know them

conductor.

today) and could cause them to ring an electric bell.

1

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

RED

VIOLET

VISIBLE LIGHT

wavelength (λ) in metres

1 m

104

102

10−2

10−4

10−6

10−8

10−10

10−12

10−14

Gamma

LONG

Radio

rays

SHORT

Radar

Infrared

Ultraviolet

X-rays

WAVELENGTH

waves

WAVELENGTH

LOW

Microwaves

HIGH

FREQUENCY

FREQUENCY

104

106

108

1010

1012

1014

1016

1018

1020

1022

frequency (ν) in hertz

Figure 1-1

Electromagnetic spectrum

Note that at the time all the research being conducted in

Radio experimenters discovered that an amplitude-

what was to become radio and later radio-electronics,

modulated wave consists of a carrier and two identical

was done by physicists.

sidebands which are both above and below the carrier

wave. The Navy conducted experiments in which they

In 1895, the father of modem radio, Guglielmo

attempted to pass one sideband and attenuate the

Marconi, of Italy, put all this together and developed

other. These experiments indicated that one sideband

the first wireless telegraph and was the first to

contained all the necessary information for voice

commercially put radio into ships. The wire telegraph

transmission, and these discoveries paved the way for

had already been in commercial use for a number of

development of the concept of single-sideband or SSB

years in Europe. The potential of radio was finally

transmission and reception.

realized through one of the most memorable events

in history. With the sinking of the Titanic in 1912,

In 1923, a patent was granted to John R. Carson on

communications between operators on the sinking

his idea to suppress the carrier and one sideband.

ship and nearby vessels, and communications to shore

In that year the first trans-Atlantic radio telephone

stations listing the survivors brought radio to the public

demonstration used SSB with pilot carrier on a

in a big way.

frequency of 52 kc. Single sideband was used because of

limited power capacity of the equipment and the narrow

AM radio broadcasting began on November 2, 1920.

bandwidths of efficient antennas for those frequencies.

Four pioneers: announcer Leo Rosenberg, engineer

By 1927, trans-Atlantic SSB radiotelephony was open

William Thomas, telephone line operator John Frazier

for public service. In the following years, the use of SSB

and standby R.S. McClelland, made their way to a

was limited to low-frequency and wire applications.

makeshift studio—actually a shack atop the Westinghouse

Early developments in FM transmission suggested that

“K” Building in East Pittsburgh—flipped a switch and

this new mode might prove to be the ultimate in voice

began reporting election returns in the Harding vs. Cox

communication. The resulting slow development of SSB

Presidential race. At that moment, KDKA became the

technology precluded practical SSB transmission and

pioneer broadcasting station of the world.

reception at high frequencies. Amateur radio SSB

Radio spread like wildfire to the homes of everyone

activity followed very much the same pattern. It wasn’t

in America in the 1920s. In a few short years, over

until 1948 that amateurs began seriously experimenting

75 manufacturers began selling radio sets. Fledgling

with SSB, likely delayed by the wartime blackouts.

manufacturers literally came out of garages over-night.

The breakthroughs in the war years, and those

Many young radio enthusiasts rushed out to buy parts

following the war, were important to the development of

Chapter One: Radio Background and History and radio kits which soon became available.

HF-SSB communication. Continued advances in

2

Chapter One: Radio Background and History

technology made SSB the dominant mode of HF radio

and “gamma” ray radiation. The only difference

communication.

between these kinds of electromagnetic radiation is the

The radio-frequency spectrum, once thought to be

frequency of their oscillation (alternation of the electric

adequate for all needs, has become very crowded.

and magnetic fields back and forth in polarity).

As the world’s technical sophistication progresses,

By using a source of AC voltage and a device called

the requirements for rapid and dependable radio

an antenna, we can create electromagnetic waves.

communications increase. The competition for available

It was discovered that high frequency electromagnetic

radio spectrum space has increased dramatically.

currents in an antenna wire, which in turn result in a

Research and development in modern radio systems has

high frequency electromagnetic field around the

moved to digital compression and narrow bandwidth

antenna, will result in electromagnetic radiation

with highly developed modulation schemes and satellite

which will move away from the antenna into free

transmission.

space at the velocity of light, which is approximately

The inventor most responsible for the modern day

300,000,000 meters per second.

advances in radio systems was Edwin H. Armstrong.

In radio transmission, a radiating antenna is used

He was responsible for the Regenerative circuit in 1912,

to convert a time-varying electric current into an

the Superheterodyne radio circuit in 1918, the

electromagnetic wave, which freely propagates through

Superregenerative radio circuit design in 1922 and

a nonconducting medium such as air or space.

the complete FM radio system in 1933. His inventions

An antenna is nothing more than a device built to

and developments form the backbone of radio

produce a dispersing electric or magnetic field.

communications as we know it today. The majority of

An electromagnetic wave, with its electric and magnetic

all radio sets sold are FM radios, all microwave relay

components, is shown in Figure 1-2.

links are FM, and FM is the accepted system in all

When attached to a source of radio frequency signal

space communications. Unfortunately, Armstrong

generator, or transmitter, an antenna acts as a transmitting

committed suicide while still embittered in patent

device, converting AC voltage and current into

lawsuits: later vindicated, his widow received a windfall.

electromagnetic wave energy. Antennas also have the

Sony introduced their first transistorized radio in

ability to intercept electromagnetic waves and convert

1960, small enough to fit in a vest pocket, and able to

their energy into AC voltage and current. In this mode,

be powered by a small battery. It was durable, because

an antenna acts as a receiving device.

there were no tubes to burn out. Over the next 20 years,

transistors displaced tubes almost completely except for

very high power, or very high frequency, uses. In the

1970s; LORAN became the standard for radio navigation

Radio frequencies

system, and soon, the US Navy experimented with

spectrum

satellite navigation. Then in 1987, the GPS constellation

of satellites was launched and navigation by radio in the

Radio frequency energy is generated by man for

sky had a new dimension. Amateur radio operators began

communications, entertainment, radar, television,

experimenting with digital techniques and started to send

pictures, faxes and teletype via the personal computer

Electric

through radio. By the late 1990s, digital transmissions

λ=Wavelength

field

began to be applied to radio broadcasting.

Magnetic

Direction

field

Types of radio waves

There are many kinds of natural radiative energy

composed of electromagnetic waves. Even light is

electromagnetic in nature. So are shortwaves, X-rays

Figure 1-2

Magnetic vs. electric wave

3

navigation, etc. This radio frequency or (RF) energy

form of a wave. They are different from sound waves

covers quite a large range of radio frequencies from the

(which are pressure waves that travel through air or

low end of the radio spectrum from l0 to 25 kHz, which

water, as an example) or ocean waves (similar to sound

is the domain occupied by the high-power Navy stations

waves in water, but much lower in frequency and are

that communicate with submerged nuclear submarines:

much larger). The wave part is similar, but the energy

these frequencies are called Very Low Frequency waves

involved is electrical and magnetic, not mechanical.

or VLF. Above the VLF frequencies are the medium

Electromagnetic waves show up as many things.

wave frequencies or (MW), i.e. the AM radio broadcast

At certain frequencies, they show up as radio waves.

band from 550 to 1600 kHz. The shortwave bands or

At much higher frequencies, we call them infrared light.

High Frequency or (HF) bands cover from 2000 kHz to

Still higher frequencies make up the spectrum known as

30,000 kHz and make use of multiple reflections from

visible light. This goes on up into ultraviolet light, and

the ionosphere which surrounds the Earth, in order to

X-rays, things that radio engineers rarely have to worry

propagate the signals to all parts of the Earth. The Very

about. For our discussions, we’ll leave light to the

High Frequencies or VHF bands begin around 30 MHz;

physicists, and concentrate on radio waves.

these lower VHF frequencies are called low-band VHF.

Radio waves have two important characteristics that

Mid-band VHF frequencies begin around 50 MHz

change. One is the amplitude, or strength of the wave.

which cover the lowest TV channel 2. Low-band

This is similar to how high the waves are coming into

television channels 2 through 13 cover the 54 to 2l6 MHz

shore from the ocean. The bigger wave has a higher

range. The popular frequency modulation or (FM)

amplitude. The other thing is frequency. Frequency is

broadcast band covers the range from 88 to l08 MHz,

how often the wave occurs at any point. The faster the

which is followed by low-band Air-band frequencies

wave repeats itself, the higher the frequency. Frequency

from 118 to 136 MHz. High-band VHF frequencies

is measured by the number of times in a second that the

around 144 are reserved for amateur radio, public service

wave repeats itself. Old timers remember when frequency

around 150 MHz, with marine frequencies around

was described in units of cycles per second. In more

156 MHz. UHF frequencies begin around 300 MHz

recent times we have taken to using the simplified term

and go up through the radar frequency band of 1000 to

of hertz (named after the guy who discovered radio

1500 MHz, and extending through approximately

waves). Metric prefixes are often used, so that 1000 hertz

300 gHz. Television channels 14 through 70 are placed

is a kilohertz, one million hertz is a megahertz, and so on.

between 470 and 800 MHz. American cell phone

carriers have cell phone communications around

A typical radio transmitter, for example, takes an

850 MHz. Geosynchronous weather satellites signals

audio input signal, such as voice or music and amplifies

are placed around 1.6 GHz, and PCS phone devices

it. The amplified audio is in turn sent to a modulator

are centered around 1.8 GHz. The Super-high frequency

and an RF exciter which comprises the radio frequency

(SHF) bands range from 3 to 30 GHz, with C-band

transmitter. The exciter in the transmitter generates a

microwave frequencies around 3.8 GHz, then X-band,

main carrier wave. The RF signal from the exciter is

from 7.25 to 8.4 GHz, followed by the KA and

further amplified by a power amplifier and then the RF

KU-band microwave bands.

signal is sent out to an antenna which radiates the signal

into the sky and out into the ionosphere. Depending

Table 1-1 illustrates the division of radio frequencies.

upon the type of transmitter used the modulation

The radio frequency spectrum extends almost up to the

technique can be either AM, FM, SSB signal sideband,

lower limit of visible light frequencies, with just the

CW, or digital modulation, etc.

infrared frequencies lying in between it and visible light.

The radio frequency spectrum is a finite resource which

must be used and shared with many people and agencies

around the world, so cooperation is very important.

AM modulation

So how does a radio work? As previously mentioned,

radio waves are part of a general class of waves known

Amplitude modulation (AM) is a technique used in

as electromagnetic waves. In essence, they are electrical

electronic communication, most commonly for

Chapter One: Radio Background and History and magnetic energy which travels through space in the transmitting information via a carrier wave wirelessly.

4

Chapter One: Radio Background and History

Table 1-1

Radio frequency spectrum chart

Frequency range

Extremely Low Frequency (ELF)

0

to

3 kHz

Very Low Frequency (VLF)

3 kHz

to

30 kHz

Radio Navigation & maritime/aeronautical mobile

9 kHz

to

540 kHz

Low Frequency (LF)

30 kHz

to

300 kHz

Medium Frequency (MF)

300 kHz

to

3000 kHz

AM Radio Broadcast

540 kHz

to

1630 kHz

Travellers Information Service

1610 kHz

High Frequency (HF)

3 MHz

to

30 MHz

Shortwave Broadcast Radio

5.95 MHz

to

26.1 MHz

Very High Frequency (VHF)

30 MHz

to

300 MHz

Low Band: TV Band 1 - Channels 2-6

54 MHz

to

88 MHz

Mid Band: FM Radio Broadcast

88 MHz

to

174 MHz

High Band: TV Band 2 - Channels 7-13

174 MHz

to

216 MHz

Super Band (mobile/fixed radio & TV)

216 MHz

to

600 MHz

Ultra-High Frequency (UHF)

300 MHz

to

3000 MHz

Channels 14-70

470 MHz

to

806 MHz

L-band:

500 MHz

to

1500 MHz

Personal Communications Services (PCS)

1850 MHz

to

1990 MHz

Unlicensed PCS Devices

1910 MHz

to

1930 MHz

Superhigh Frequencies (SHF)

(Microwave)

3 GHz

to

30.0 GHz

C-band

3600 MHz

to

7025 MHz

X-band

7.25 GHz

to

8.4 GHz

Ku-band

10.7 GHz

to

14.5 GHz

Ka-band

17.3 GHz

to

31.0 GHz

Extremely High Frequencies (EHF)

(Millimeter Wave Signals)

30.0 GHz

to

300 GHz

Additional Fixed Satellite

38.6 GHz

to

275 GHz

Infrared Radiation

300 GHz

to

430 THz

Visible Light

430 THz

to

750 THz

Ultraviolet Radiation

1.62 PHz

to

30 PHz

X-Rays

0.30 PHz

to

30 EHz

Gamma Rays

0.30 EHz

to

3000 EHz

It works by varying the strength of the transmitted

radio transmissions, and remains in use by some forms

signal in relation to the information being sent.

of radio communication—“AM” is often used to refer

In the mid-1870s, a form of amplitude modulation

to the medium-wave broadcast band (see AM

was the first method to successfully produce quality

Radio–Chapter 5).

audio over telephone lines. Beginning in the early

Amplitude modulation (AM) is a type of modulation

1900s, it was also the original method used for audio

technique used in communication. It works by varying

5

Figure 1-3

Amplitude modulation waveform

the strength of the transmitted signal in relation to the

of the carrier is varied while its frequency remains

information being sent, for example, changes in the

constant. In analog applications, the carrier frequency is

signal strength can be used to reflect sounds being

varied in direct proportion to changes in the amplitude

reproduced in the speaker. This type of modulation

of an input signal. Digital data can be represented by

technique creates two sidebands with the carrier wave

shifting the carrier frequency among a set of discrete

signal placed in the center between the two sidebands.

values, a technique known as frequency-shift keying.

The transmission bandwidth of AM is twice the signal’s

The diagram in Figure 1-4, illustrates the FM modulation

original (baseband) bandwidth—since both the positive

scheme, the RF frequency is varied with the sound input

and negative sidebands are ‘copied’ up to the carrier

rather than the amplitude.

frequency, but only the positive sideband is present

FM is commonly used at VHF radio frequencies

originally. See Figure 1-3. Thus, double-sideband AM

for high-fidelity broadcasts of music and speech,

(DSB-AM) is spectrally inefficient. The power

as in FM broadcasting. Normal (analog) TV sound is

consumption of AM reveals that DSB-AM with its

also broadcast using FM. A narrowband form is used

carrier has an efficiency of about 33% which is too

for voice communications in commercial and amateur

efficient. The benefit of this system is that receivers are

radio settings. The type of FM used in broadcast is

cheaper to produce. The forms of AM with suppressed

generally called wide-FM, or W-FM. In two-way radio,

carriers are found to be 100% power efficient, since no

narrowband narrow-FM (N-FM) is used to conserve

power is wasted on the carrier signal which conveys no

bandwidth. In addition, it is used to send signals

information. Amplitude modulation is used primarily in

into space.

the medium wave band or AM radio band which covers

Wideband FM (W-FM) requires a wider bandwidth

520 to 1710 kHz. AM modulation is also used by

than amplitude modulation by an equivalent modulating

shortwave broadcasters in the SW bands from between

signal, but this also makes the signal more robust against

5 MHz and 24 MHz, and in the aircraft band which

noise and interference. Frequency modulation is also

covers 188 to 136 MHz.

more robust against simple signal amplitude fading

phenomena. As a result, FM was chosen as the

modulation standard for high frequency, high fidelity

FM modulation

radio transmission: hence the term “FM radio.”

FM broadcasting uses a well-known part of the VHF

Frequency modulation (FM) is a form of modulation

band between 88 and 108 MHz in the USA.

which represents information as variations in the

FM receivers inherently exhibit a phenomenon

instantaneous frequency of a carrier wave. Contrast this

called capture, where the tuner is able to clearly

Chapter One: Radio Background and History with amplitude modulation, in which the amplitude receive the stronger of two stations being broadcast on

6

Chapter One: Radio Background and History

Figure 1-4

FM modulation waveform

the same frequency. Problematically, however,

removed because it is the sidebands that provide the

frequency drift or lack of selectivity may cause one

actual meaningful content of material, within the

station or signal to be suddenly overtaken by another

modulation envelope. In order to make SSB even more

on an adjacent channel. Frequency drift typically

efficient, one of these two sidebands is removed by a

constituted a problem on very old or inexpensive

bandpass. So the intelligence is preserved with SSB

receivers, while inadequate selectivity may plague

and it becomes a more efficient use of radio spectrum

any tuner. Frequency modulation is used on the FM

energy. It provides almost 9 Decibels (dBs) of signal

broadcast band between 88 and 108 MHz as well as in

gain over an amplitude modulated signal that includes

the VHF and UHF bands for both public service and

an RF “carrier” of the same power level! As the final

amateur radio operators.

RF amplification is now concentrated in a single

sideband, the effective power output is greater than in

normal AM (the carrier and redundant sideband

Single sideband (SSB)

account for well over half of the power output of

an AM transmitter). Though SSB uses substantially

modulation

less bandwidth and power, it cannot be demodulated

by a simple envelope detector like standard AM.

Single sideband modulation (SSB) is a refinement upon

SSB was pioneered by telephone companies in the

amplitude modulation, which was designed to be more

1930s for use over long-distance lines, as part of a

efficient in its use of electrical power and spectrum

technique known as frequency-division multiplexing

bandwidth. Single sideband modulation avoids this

(FDM). This enabled many voice channels to be sent

bandwidth doubling, and the power wasted on a carrier,

down a single physical circuit. The use of SSB meant

but the cost of some added complexity.

that the channels could be spaced (usually) just 4000 Hz

The balanced modulator is the most popular method

apart, while offering a speech bandwidth of nominally

of producing a single sideband modulated signal. The

300–3400 Hz. Amateur radio operators began to

balanced modulator provides the “sidebands” of energy

experiment with the method seriously after World War II.

that exist on either side of the carrier frequency but

It has become a de facto standard for long-distance

eliminates the RF carrier, see Figure 1-5. The carrier is

voice radio transmissions since then.

7

Figure 1-5

Single sideband modulation waveform

Single Sideband Suppressed Carrier (SSB-SC)

Another factor which determines radio propagation is

modulation was the basis for all long-distance telephone

the time of the day; this is due to a particular transient

communications up until the last decade. It was

atmosphere ionized layer forming only during day when

called “L carrier.” It consisted of groups of telephone

atoms are broken up into ions by sun photons. This layer

conversations modulated on upper and/or lower

is responsible for partial or total absorption of particular

sidebands of contiguous suppressed carriers. The

frequencies. During the day, higher shortwave frequencies

groupings and sideband orientations (USB, LSB)

(i.e., above 10 MHz) can travel longer distances than

supported hundreds and thousands of individual

lower ones; at night, this property is reversed.

telephone conversations. Single sideband communications

Different types of modulation techniques are used on

are used by amateur radio operators and government,

the shortwave frequencies in addition to AM and FM.

and utility stations primarily in the shortwave bands for

AM, amplitude modulation, is generally used for

long-distance communications.

shortwave broadcasting, and some aeronautical

communications, while Narrow-band frequency

modulation (NFM) is used at the higher HF frequencies.

Single sideband or (SSB), is used for long-range

Shortwave radio

communications by ships and aircraft, for voice

transmissions by amateur radio operators. CW,

Shortwave radio operates between the frequencies of

Continuous Carrier Wave or (CW), is used for Morse

1.80 MHz and 30 MHz and came to be referred to as

code communications. Various other types of digital

such in the early days of radio because the wavelengths

communications such as radioteletype, fax, digital,

associated with this frequency range were shorter than

SSTV and other systems require special hardware and

those commonly in use at that time. An alternate name is

software to decode. A new broadcasting technique

HF or high frequency radio. Short wavelengths are

called Digital Radio Mondiale or (DRM) is a digital

associated with high frequencies because there is an

modulation scheme used on bands below 30 MHz.

inverse relationship between frequency and wavelength.

Shortwave frequencies are capable of reaching the other

side of the Earth, because these waves can be refracted by

the ionosphere, by a phenomenon known as Skywave

Shortwave listening

propagation. High-frequency propagation is dependent upon

a number of different factors, such as season of the year,

Many hobbyists listen to shortwave broadcasters and for

solar conditions, including the number of sunspots, solar

some listeners the goal is to hear as many stations from

flares, and overall solar activity. Solar flares can prevent the

as many countries as possible (DXing); others listen to

Chapter One: Radio Background and History ionosphere from reflecting or refracting radio waves.

specialized shortwave utility, or “UTE,” transmissions

8

Chapter One: Radio Background and History

such as maritime, naval, aviation, or military signals.

Speciality political, religious, and conspiracy

Others focus on intelligence signals. Many, though,

theory radio networks, individual commercial and

tune the shortwave bands for the program content of

non-commercial paid broadcasts for the north American

shortwave broadcast stations, aimed to a general

and other markets. Utility stations transmitting

audience (such as the Voice of America, BBC World

messages not intended for a general public, such as

Service, Radio Australia, etc.). Some even listen to

aircraft flying between continents, encoded or ciphered

two-way communications by amateur radio operators.

diplomatic messages, weather reporting, or ships at

Nowadays, as the Internet evolves, the hobbyist can

sea. Amateur radio operators have rights to use many

listen to shortwave signals via remotely controlled

frequencies in the shortwave bands; you can hear their

shortwave receivers around the world, even without

communications using different modulation techniques

owning a shortwave radio (see for example

and even obtain a license to communicate in these

http://www.dxtuners.com). Alternatively, many

bands yourself. Contact the Amateur Radio Relay

international broadcasters (such as the BBC) offer live

League for more information. Table 1-3 illustrates the

streaming audio on their web-sites. Table 1-2, lists some

amateur radio frequencies and how they are divided

of the popular shortwave broadcast bands.

between the different license classes. On the shortwave

Shortwave listeners, or SWLs, can obtain QSL cards

band you will also encounter time signal stations and

from broadcasters, utility stations or amateur radio

number stations, thought to be spy stations operating on

operators as trophies of the hobby. Some stations

the shortwave bands.

even give out special certificates, pennants, stickers

and other tokens and promotional materials to

shortwave listeners.

Types of receivers

Major users of the shortwave radio bands include

domestic broadcasting in countries with a widely

A radio signal is transmitted through the ionosphere

dispersed population with few long-wave, medium-wave,

and is picked up by the antenna in your radio receiver.

or FM stations serving them. International broadcasting

The antenna is fed to an RF amplifier and usually an

stations beamed radio broadcasts to foreign audiences.

intermediate amplifier or IF amplifier and then on to a

detector of some sort depending upon the type of

receiver you are using. From the detector, the resultant

Table 1-2

audio signal is amplified and sent to a loudspeaker for

Shortwave broadcast chart

listening. Figure 1-6 illustrates a block diagram of a

typical AM radio receiver. The antenna is sent to the RF

Megahertz

Band

Band (MHz)

Kilohertz (KHz)

amplifier. The mixer is fed by both the local oscillator

and the RF amplifier. The signal from the mixer is sent

120 Meter

2.3–2.5 MHz

2300–2500 KHz

to a bandpass filter and then on to the first IF amplifier.

90 Meter

3.2–3.40 MHZ

3200–3400 KHz

The first IF amplifier is next sent to the detector and

75 Meter

3.90–4.00 MHZ

3900–4000 KHz

then on to the final audio amplifier stage which drives

60 Meter

4.750–5.060 MHz

4750–5060 KHz

the speaker. The illustration depicted in Figure 1-7

49 Meter

5.950–6.20 MHz

5950–6200 KHz

shows a typical FM receiver block diagram. The antenna

41 Meter

7.10–7.60 MHz

7100–7600 KHz

feeds the RF amplifier stage. Both the RF amplifier and

31 Meter

9.20–9.90 MHz

9500–9900 KHz

local oscillator are fed into the mixer. The signal from

the mixer is next sent to the IF amplifier stage. From

25 Meter

11.60–12.200 MHz

11600–12200 KHz

the IF amplifier stage the signal is next sent to the FM

22 Meter

13.570–13.870 MHZ

13570–13870 KHz

demodulator section, which feeds the signal to the

19 Meter

15.10–15.800 MHz

15100–15800 KHz

voltage amplifier and then the signal is fed to the final

16 Meter

17.480–17.900 MHz

17480–17900 KHz

audio amplifier stage and on to the speaker. Note the

13 Meter

21.450–21.850 MHz

21450–21850 KHz

feedback path between, i.e. the AGC or automatic

11 Meter

25.60–26.100 MHz

25600–26100 KHz

frequency control from the FM demodulator back to

9

Table 1-3

US amateur radio bands

160 Meters

E,A,G

Novice, Advanced and Technician Plus Allocations

1800

1900

2000

kHz

New Novice, Advanced and Technician Plus licenses are no longer being issued, but existing Novice, Technician Plus and Advanced class licenses are unchanged. Amateurs can continue to renew these Amateur stations operating at 1900-2000 kHz must not cause

licenses. Technician who pass the 5 wpm Morse code exam after that date have Technician Plus harmful interference to the radiolocation service and are

privileges, although their license says Technician. They must retain the 5 wpm Certificate of Successful afforded no protection from radiolocation operations.

Completion of Examination (CSCE) as proof. The CSCE is valid indefinitely for operating authorization, 80 Meters

but is valid only for 365 days for upgrade credit.

3675

3725

3525

3850

US AMATEUR POWER LIMITS

N,P*

12 Meters

3775

At all times, transmitter power

G

E,A,G

should be kept down to that

A

necessary to carry out the

E

24,890

24,930

24,990

kHz.

desired communications. Power

is rated in watts PEP output.

3500

3750

4000

kHz

Unless otherwise stated, the

28,100

28,500

60 Meters

10 Meters

maximum power output is1500 W.

Power for all license classes

General, Advanced and Amateur Extra licensees may use the following N,P*

is limited to 200 W in the 10,100-

five channels on a secondary basis with a maximum effective radiated 10,150 kHz band and in all

E,A,G

power of 50 W PEP relative to a half wave dipole. Only upper sideband Novice subbands below 28,100 kHz.

suppressed carrier voice transmissions may be used.The frequencies Novices and Technicians are

28,000

28,300

are 5330.5, 5345.5, 5355.5, 5371.5 and 5403.5 kHz. The occupied

29,700

kHz.

restricted to 200 W in the

bandwidth is limited to 2.8 kHz centered on 5332, 5345, 5355, 5373

Novices and Technician Plus Licensees are limited to

28,100-28,500 kHz subbands. In

and 5405 kHz respectively.

200 watts PEP output on 10 meters.

addition, Novices are restricted to

40 Meters

25 W in the 222-225 MHz band

7100

7150

and 5 W in the 1270-1295 MHz

6 Meters

subband.

7025

7225

50.1

N,P*

†

KEY

G

E,A,G,P,T*

†

= CW, RTTY and data

A †

50.0

54.0

MHz.

E

= CW, RTTY, data MCW,

test, phone and image

7000

7150

7300

kHz

144.1

2 Meters

= CW, phone and image

† Phone and image modes are permitted between 7075 and 7100 kHz

for FCC licensed stations in ITU Regions 1 and 3 and by FCC

E,A,G,P,T*

= CW and SSB phone

licensed stations in ITU Region 2 West of 130 degrees West

= CW, RTTY, data, phone

longitude or South of 20 degrees North latitude. See sections 97.305 (c) 144.0

145.0

MHz.

and image

and 97.307 (f)(11). Novice and Technician Plus licensees outside ITU Region

= CW only

2 may use CW only between 7050 and 7075 kHz. See Section 97.301(e).

1.25 Meters ***

These exemptions do not apply to stations in the continental US.

E = AMATEUR EXTRA

30 Meters

A = ADVANCED

E,A,G,P,T,N*

G = GENERAL

E,A,G

P = TECHNICIAN PLUS

222.0

225.0

MHz.

T = TECHNICIAN

10,100

10,150

kHz

N = NOVICE

Novices are limitted to 25 watts PEP output from 222 to

Maximum power on 30 meters is 200 watts PEP output.

*Technicians who have passed the

225 MHz.

Amateurs must avoid interference to the fixed service outside the US.

5 wpm Morse code exam are

indicated as "P".

20 Meters

70 Centimeters **

**Geographical and power restrictions

14,025

14,150

14,225

apply to all bands with frequencies

E,A,G,P,T*

14,175

above

420 MHz.

G

See

The ARRL FCC Rule Book for

A

420.0

450.0

MHz.

more information about your area.

E

***219-220 MHz allocated to

14,000

14,150

14,350

kHz

33 Centimeters **

amateurs on a secondary basis for

fixed digital message forwarding

systems only and can be operated

E,A,G,P,T*

17 Meters

by all licensees except Novices.

E,A,G

902.0

928.0

MHz.

All licensees except Novices are

authorized all modes on the

18,068

18,110

18,168

kHz

following frequencies:

23 Centimeters **

15 Meters

2300-2310 MHz

2390-2450 MHz

1270

1295

3300-3500 MHz

21,100

21,200

5650-5925 MHz

21,025

21,300

N,P*

N

10.0-10.5 GHz

21,225

E,A,G,P,T*

24.0-24.25 GHz

G

47.0-47.2 GHz

A

76.0-81.0 GHz

1240

1300

MHz.

122.225-123.0 GHz

E

Novices are limited to 5 watts PEP output from 1270 to

134-141 GHz

1295 MHz.

241-250 GHz

21,000

21,200

21,450

kHz

All above 275 GHz

the local oscillator. Finally, the shortwave radio block

then on to the speaker. The receivers shown are the

diagram is illustrated in the diagram in Figure 1-8. The

most common types of receivers. There are in fact

antenna line is fed to the RF amplifier section. Both the

many different variations in receiver designs including

local oscillator and the RF amplifier are fed to a filter

receivers made to receive special digital signals, which

section, which is in turn sent to the IF amplifier section.

we will not discuss here.

The output signal from the IF amplifier section is next

Next, we will move our discussion to identifying

sent to the product detector. A BFO or beat frequency

electronics components and reading schematics

oscillator signal is sent to the product detector, this is

and learning how to solder before we forge

what permits SSB reception. The signal from the

ahead and begin building some fun radio receiver

Chapter One: Radio Background and History product detector is next sent to the audio amplifier and projects.

10

Chapter One: Radio Background and History

Figure 1-6

AM radio block diagram

Figure 1-7

FM radio block diagram

Figure 1-8

SSB shortwave receiver block diagram

11

Chapter 2

Identifying Components and

Reading Schematics

Identifying electronic

Types of resistors

components

Resistors are used to regulate the amount of current

flowing in a circuit. The higher the resistor’s value or

If you are a beginner to electronics or radio, you may

resistance, the less current flows and conversely a lower

want to take a few minutes to learn a little about

resistor value will permit more current to flow in a

identifying electronic components, reading schematics,

circuit. Resistors are measured in ohms (Ω) and are

and installing electronic components on a circuit board.

identified by color bands on the resistor body. The first

You will also learn how to solder, in order to make

band at one end is the resistor’s first digit, the second

long-lasting and reliable solder joints.

color band is the resistor’s second digit and the third

Electronic circuits comprise electronic components

band is the resistors’s multiplier value. A fourth color

such as resistors and capacitors, diodes, semiconductors

band on a resistor represents the resistor’s tolerance

and LEDs, etc. Each component has a specific purpose

value. A silver band denotes a 10% tolerance resistor,

that it accomplishes in a particular circuit. In order to

while a gold band denotes a 5% resistor tolerance. No

understand and construct electronic circuits it is

fourth band denotes that a resistor has a 20% tolerance.

necessary to be familiar with the different types of

As an example, a resistor with a brown, black, and red

components, and how they are used. You should also

band will represent the digit (1), the digit (0), with a

know how to read resistor and capacitor color codes,

multiplier value of (00) or 1000, so the resistor will

recognize physical components and their representative

have a value of 1k or 1000 ohms. There are a number of

diagrams and pin-outs. You will also want to know the

different styles and sizes of resistor. Small resistors can

difference between a schematic and a pictorial diagram.

be carbon, thin film or metal. Larger resistors are made

First, we will discuss the actual components and their

to dissipate more power and they generally have an

functions and then move on to reading schematics,

element wound from wire.

then we will help you to learn how to insert the

A potentiometer (or pot) is basically a variable

components into the circuit board. In the next chapter

resistor, generally having three terminals and fitted with

we will discuss how to solder the components to the

a rotary control shaft which varies the resistance as it is

circuit board.

rotated. A metal wiping contact rests against a circular

The diagrams shown in Figures 2-1, 2-2 and 2-3

carbon or wire wound resistance track. As the wiper

illustrate many of the electronic components that we

arm moves about the circular resistance, the resistance

will be using in the projects presented in this book.

to the output terminals changes. Potentiometers are

12

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Two: Identifying Components

Figure 2-1

Electronic components 1

commonly used as volume controls in amplifiers and

i.e. millions of ohms. When light falls on the LDR the

radio receivers.

resistance drops to a few hundred ohms.

A trimpot is a special type of potentiometer which,

while variable, is intended to be adjusted once or only

occasionally. For this reason a control shaft is not

Types of capacitors

provided but a small slot is provided in the center of the

control arm. Trimpots are generally used on printed

Capacitors block DC current while allowing varying or

circuit boards.

AC current signals to pass. They are commonly used for

A light-dependent resistor (LDR) is a special type of

coupling signals from part of a circuit to another part of

resistor that varies its resistance value according to the

a circuit, they are also used in timing circuits. There are

amount of light falling on it. When it is in the dark,

a number of different types of capacitor as described

an LDR will typically have a very high resistance,

below.

13

Figure 2-2

Electronic components 2

Polyester capacitors use polyester plastic film as their

MKT capacitors are another type of capacitor, but

insulating dielectric. Some polyester capacitors are

they are rectangular or (block) in shape and are usually

called greencaps because they are coated with a green

yellow in color. One of the major advantages of these

or brown color coating on the outside of the component.

capacitors is a more standardized lead spacing, making

Their values are specified in microfarads or (µF),

them more useful for PC board projects. The components

nanofarads, (nF), or picofarads (pF) and range from

can generally be substituted for polyester types.

1 nF up to about 10 µF. These capacitors do not have

Ceramic capacitors use a tiny disk of ceramic or

Chapter Two: Identifying Components polarity and have fixed values.

porcelain material in their construction for a dielectric

14

Chapter Two: Identifying Components

Figure 2-3

Electronic components 3

and they range in value from 1 pF up to 2.2 µF. Those

a large amount of capacitance in a very small volume.

with values above 1 nF are often made with multiple

They range in value from 100 nF up to hundreds and

layers of metal electrodes and dielectric, to allow higher

thousands of microfarads (µF). They are commonly

capacitance values in smaller bodies. These capacitors

used to filter power supply circuits, coupling audio

are usually called ‘multilayer monolithics’ and

circuits and in timing circuits. Electrolytic capacitors

distinguished from lower value disk ceramic types.

have polarity and must be installed with respect to

Ceramic capacitors are often used in RF radio circuits

these polarity marking. The capacitor will have

and filter circuits.

either a white or black band denoting polarity

Electrolytic capacitors use very thin film of metal

with a plus (+) or minus (−) marking next to the

oxide as their dielectric, which allows them to provide

color band.

15

Variable capacitors are used in circuits for (trimming)

These devices are usually bolted to the chassis and are

or adjustment, i.e. for setting a frequency. A variable

used for amplifying RF or audio energy.

capacitor has one set of fixed plates and one set of

plates which can be moved by turning a knob. The

dielectric between the plates is usually a thin plastic

Integrated circuits

film. Most variable capacitors have low values up to a

few tens of picofarads (pF) and a few hundreds of

Integrated circuits, or ICs, contain all, or most, of the

microfarads for larger variable capacitors.

components necessary for a particular circuit function,

in one package. Integrated circuits contain as few as

10 transistors or many millions of transistors, plus many

Diodes

resistors, diodes and other components. There are many

shapes, styles and sizes of integrated circuits: in this

A diode is a semiconductor device which can pass

book we will use the dual-in-line style IC, either 8, 14

current in one direction only. In order for current to

or 16 pin devices.

flow the anode (A) must be positive with respect to the

Three-terminal regulators are special types of

cathode (K). In this condition, the diode is said to be

integrated circuits, which supply a regulated or constant

forward biased and a voltage drop of about .6 volt

and accurate voltage from output regardless (within

appears across its terminals. If the anode is less than

limits) of the voltage applied to input. They are most

.6 volt positive with respect to the cathode, negligible

often used in power supplies. Most regulators are

current will flow and the diode behaves as an open

designed to give specific output voltages, i.e. a ‘LM7805”

circuit.

regulator provides a 5 volt output, but some IC regulators

can provide adjustable output based on an external

potentiometer which can vary the output voltage.

Types of transistors

Transistors are semiconductor devices that can be used

Heatsinks

either as electronic switches or to amplify signals. They

have three leads, called the Collector, Base, and Emitter.

Many electronic components generate heat when they

A small current flowing between base and emitter

are operating. Generally heatsinks are used on

(junction) causes a much larger current to flow between

semiconductors like transistors to remove heat.

the emitter and collector (junction). There a two basic

Overheating can damage a particular component or the

types of transistors, PNP and NPN styles.

entire circuit. The heatsink cools the transistor and

Field Effect Transistors, or FETs, are a different type

ensures a long circuit life by removing the excess heat

of transistor, which usually still have three terminals but

from the circuit area.

work in a different way. Here the control element is the

“gate” rather than the base, and it is the “gate” voltage

which controls the current flowing in the “channel”

Light-emitting diodes

between the other terminals—the “source” and the

“drain.” Like ordinary transistors FETs can be used

Light-emitting diodes, or LEDs, are special diodes

either as electronic switches or as amplifiers; they also

which have a plastic translucent body (usually clear,

come in P-channel and N-channel types, and are

red, yellow, green or blue in color) and a small

available in small signal types as well as power FETs.

semiconductor element which emits light when the

Power transistors are usually larger than the smaller

diode passes a small current. Unlike an incandescent

signal type transistors. Power transistors are capable of

lamp, an LED does not need to get hot to produce light.

handling larger currents and voltages. Often metal tabs

LEDs must always be forward biased to operate. Special

Chapter Two: Identifying Components and heatsinks are used to remove excess heat from the part.

LEDs can also produce infrared light.

16

Chapter Two: Identifying Components

LED displays consist of a number of LEDs together

diaphragm made from very thin plastic material which

in a single package. The most common type has seven

has a permanent charge in it. Metal films coated on each

elongated LEDs arranged in an “8” pattern. By choosing

side form a capacitor, which produces a very small

which combinations of LEDs are lit, any number of

AC voltage when the diaphragm vibrates. All electret

digits from “0” through “9” can be displayed. Most of

microphones also contains FET which amplifies the

these “7-segment” displays also contain another small

very small AC signals. To power an FET amplifier, the

round LED which is used as a decimal point.

microphone must be supplied with a small DC voltage.

Types of inductors

Loudspeakers

Inductors or “coils” are basically a length of wire,

A loudspeaker converts electrical signals into sound

wound into a cylindrical spiral (or layers of spirals) in

waves that we can hear. It has two terminals which go

order to increase their inductance. Inductance is the

to a voice coil, attached to a circular cone made of

ability to store energy in a magnetic field. Many coils

either cardboard or thin plastic. When electrical signals

are wound on a former of insulating material, which

are applied to the voice coil, its creates a varying

may also have connection pins to act as the coil’s

magnetic field from a permanent magnet at the back of

terminals. The former may also be internally threaded to

the speaker. As a result the cone vibrates in sympathy

accept a small core or “slug” of ferrite, which can be

with the applied signal to produce sound waves.

adjusted in position relative to the coil itself to vary the

coil inductance.

A transformer consists of a number of coils of

Relays

windings of wire wound on a common former, which is

also inside a core of iron alloy, ferrite of other magnetic

Many electronic components are not capable of

material. When an alternating current is passed through

switching higher currents or voltages, so a device called

one of the windings (primary), it produces an alternating

a relay is used. A relay has a coil which forms an

magnetic field in the core and this in turn induces AC

electromagnet, attracting a steel “armature” which itself

voltages in the other (secondary) windings. The voltages

pushes on one or more sets of switching contacts. When

produced in the other winding depend on the number of

a current is passed through the coil to energize it, the

turns in those windings, compared with the turns in the

moving contacts disconnect from one set of contacts to

primary winding. If a secondary winding has fewer

another, and when the coil is de-energized the contacts

turns than the primary, it will produce a lower voltage,

go back to their original position. In most cases, a relay

and be called a step-down transformer. If the secondary

needs a diode across the coil to prevent damage to the

winding has more windings than the primary, then the

semiconductor driving the coil.

transformer will produce a higher voltage and it will be

a step-up transformer. Transformers can be used to

change the voltage levels of AC power and they are

available in many different sizes and power handling

Switches

capabilities.

A switch is a device with one or more sets of switching

contacts, which are used to control the flow of current

in a circuit. The switch allows the contacts to be

Microphones

controlled by a physical actuator of some kind—such as

a press-button toggle lever, rotary or knob, etc. As the

A microphone converts audible sound waves into

name denotes, this type of switch has an actuator bar

electrical signals which can be then amplified. In an

which slides back and forth between the various contact

electret microphone, the sound waves vibrate a circular

positions. In a single-pole, double throw, or “SPDT”

17

slider switch, a moving contacte links the center contact

replacement, so the closest specifications of that

to either of the two end contacts. In contrast, a double-

component are attempted. In some instances we have

pole double throw (DPDT) slider switch has two of

specified replacement components with substitution

these sets of contacts, with their moving contacts

components from the NTE brand or replacements. Most

operating in tandem when the slider is actuated.

of the components for the projects used in this book are

quite common and easily located or substituted without

difficulty.

When substituting components in the circuit, make

Wire

sure that the pin-outs match the original components.

Sometimes, for example, a transistor may have bottom

A wire is simply a length of metal conductor, usually

view drawing, while the substituted value may have a

made from copper since its conductivity is good, which

drawing with a top view. Also be sure to check the pin-outs

means its resistance is low. When there is a risk of a wire

or the original components versus the replacement.

touching another wire and causing a short, the copper

As an example, some transistors will have EBC versus

wire is insulated or covered with a plastic coating which

ECB pin-outs, so be sure to look closely at possible

acts as an insulating material. Plain copper wire is not

differences which may occur.

usually used since it will quickly oxidize or tarnish in

the presence of air. A thin metal alloy coating is often

applied to the copper wire; usually an alloy of tin or

lead is used.

Reading electronic

Single or multi-strand wire is covered in colored PVC

schematics

plastic insulation and is used quite often in electronic

applications to connect circuits or components together.

The heart of all radio communication devices, both

This wire is often called “hooku” wire. On a circuit

transmitters and receivers, all revolve around some type

diagram, a solid dot indicates that the wires or PC

of oscillator. In this section we will take a look at what

board tracks are connected together or joined, while a

is perhaps the most important part of any receiver, and

“loop-over” indicates that they are not joined and must

that is the oscillator. Communication transmitters,

be insulated. A number of insulated wires enclosed

receivers, frequency standards and synthesizers all use

in an outer jacket is called an electrical cable. Some

some type of oscillators circuits. Transmitters need

electrical cables can have many insulated wires in them.

oscillators for their exciters, while receivers most often

use local oscillators to mix signals. In this section you

will see how specific electronics components are

Semiconductor

utilized to form oscillator circuits. Let’s examine a few

of the more common types of oscillator designs and

substitution

their building considerations. In this section, you will

also tell the difference between a schematic diagram

There are often times when building an electronic

and a pictorial diagram. A schematic diagram illustrates

circuit, it is difficult or impossible to find or locate the

the electronic symbols and how the components

original transistor or integrated circuit. There are a

connect to one another, it is the circuit blue-print and

number of circuits shown in this book which feature

pretty much universal among electronic enthusiasts.

transistors, SCRs, UJTs, and FETs that are specified but

A pictorial diagram, on the other hand, is a “picture” of

cannot easily be found. Where possible many of these

how the components might appear in an actual circuit

foreign components are converted to substitute values,

on a circuit board of one type or another. Take a close

either with a direct replacement or close substitution.

look at the difference between the two types of

Many foreign parts can be easily converted directly to a

diagram, and they will help you later when building

commonly used transistor or component. Occasionally

actual circuits. Our first type of oscillator shown below

Chapter Two: Identifying Components an outdated component has no direct common is The Hartley.

18

Chapter Two: Identifying Components

you could use a T50-6 toroid and wind say 37 turns of

Hartley oscillator

#24 wire (5.48 µH) tapping at 9 turns.

So to have the oscillator operate at around 5 MHz, we

The Hartley RF oscillator, illustrated in Figure 2-4, is

know the LC is 1013 and if L is say 5.7 µH then total C

centered around the commonly available 2N4416A FET

for resonance (just like LC Filters eh!) is about 177 pF.

transistor. This general purpose VFO oscillator operates

We want to be able to tune from 5000 to 5100 kHz, a

around 5100 kHz. The frequency determining

tuning ratio of 1.02, which means a capacitance ratio of

components are L1, C1, a 10 pF trimmer and capacitors

1.04 (min to max).

C2, C3, C4, C5 and C6. Note capacitor C6 is a

10-100 pF variable trimmer type. Capacitor C7 is to

reduce the loading on the tuned circuit components. Its

Colpitts oscillators

value can be small but be able to provide sufficient

drive to the succeeding buffer amplifier stage. You can

Colpitts oscillators are similar to the shunt fed Hartley

experiment using a small viable capacitor trimmer, such

oscillator circuit except the Colpitts oscillator, instead of

as a 5-25 pF.

having a tapped inductor, utilizes two series capacitors

in its LC circuit. With the Colpitts oscillator the

The other components, such as the two resistors, silicon

connection between these two capacitors is used as the

diode at D1 are standard types, nothing particularly

center tap for the circuit. A Colpitts oscillator circuit is

special. The Zener diode at D2 is a 6.2 volt type.

shown at Figure 2-5, and you will see some similarities

Capacitor C8 can be selected to give higher/lower output

with the Hartley oscillator.

to the buffer amplifier. Smaller C6 values give lower

output and conversely higher values give larger output.

The simplest Colpitts oscillator to construct and get

In order to get the circuit to work properly, you need

running is the “series tuned” version, more often

to have an inductive reactance for L1 of around about

referred to as the “Clapp Oscillator.” Because there is

180 ohms. At 5 MHz this works out at about 5.7 uH.

no load on the inductor, a high “Q” circuit results with

The important consideration, is that the feedback point

a high L/C ratio and of course much less circulating

from the source of the JFET connects to about 25%

current. This aids drift reduction. Because larger

of the windings of L1 from the ground end. An air

inductances are required, stray inductances do not

cored inductor is shown in the diagram. It could be,

have as much impact as perhaps in other circuits.

for example, 18-19 turns of #20 gauge wire on a

The total capacitive reactance of the parallel

25.4 mm (1′′) diameter form spread evenly over a

combination of capacitors depicted as series tuning

length of about 25.4 mm (1′′). The tap would be at about

below the inductor in a series tuned Colpitts oscillator

41⁄2 turns. Alternatively, with degraded performance,

or “Clapp oscillator” should have a total reactance of

Figure 2-4

Hartley oscillator circuit

19

Figure 2-5

Series tuned Colpitts oscillator circuit

around 200 ohms. Not all capacitors may be required in

HF and higher frequencies without resorting to some

your particular application. Effectively all the capacitors

sort of crystal control. Hence the reason for crystal

are in series in a Colpitts oscillator, i.e. they appear as

oscillators.

parallel connected but their actual values are in fact

The crystal oscillator depicted at Figure 2-6 is a

in series.

typical example of an RF or radio frequency crystal

Ideally, your frequency determining components L1

oscillators which may be used for exciters or RF

and the parallel capacitors should be in a grounded

converters. Transistor Q1, can be any transistor which

metal shield. The FET used in the Colpitts oscillator is

will operate up to 150 MHz, such as a 2N2222A.

the readily available 2N4416A. Note, the metal FET

The turns ratio on the tuned circuit depicts an

case is connected to the circuit ground. The output from

anticipated nominal load of 50 ohms. This allows a

the Colpitts oscillator is through output capacitor 47 pF;

theoretical 2.5k ohms on the collector, so typically a

this should be the smallest of values possible, consistent

7:1 turns ratio for T1 would be used. Use the: L * C =

with continued reliable operation into the next buffer

25330 / F02 formula for determining L and C in the

amplifier stage.

tuned circuits of crystal oscillator. Personally I would

make L a reactance of around 250 ohms. In this case,

Crystal oscillators

I’d make C1 a smaller trimmer capacitor. The crystal at

X1 could be an overtone type crystal for the crystal,

Crystal oscillators are oscillators where the primary

selecting a L * C for the odd particular multiple of

frequency determining element is a quartz crystal.

overtone wanted in your crystal oscillators. Typically

Because of the inherent characteristics of the quartz

the output of the crystal oscillator would be followed by

crystal the crystal oscillator may be held to extreme

a buffer circuit. A pictorial diagram of the crystal

accuracy of frequency stability.

controlled oscillator circuit is shown in Figure 2-7. Note

Crystal oscillators are, usually, fixed frequency

that the components in this diagram are illustrated as

oscillators where stability and accuracy are the primary

component blocks as they might actually look placed on

considerations. For example, it is almost impossible to

the circuit, rather than as electronic symbols in a circuit

design a stable and accurate LC oscillator for the upper

diagram or schematic.

Chapter Two: Identifying Components

20

Chapter Two: Identifying Components

Figure 2-6

Crystal oscillator circuit

Figure 2-7

Crystal oscillator pictorial diagram

21

The diagram shown in Figure 2-9 depicts the ceramic

Ceramic resonator VFO oscillator

resonator as a pictorial diagram, where the components

look as a components block that might be placed in a

The ceramic resonator VFO, or variable frequency

circuit rather than an actual schematic diagram.

oscillator circuit shown in Figure 2-8, illustrates a 7MH

oscillator with a variable crystal oscillator (VXO). The

Voltage controlled oscillator (VCO)

VXO oscillator is extremely stable, but allows only a

small variation in frequency, as compared with a

A voltage controlled oscillator, or VCO, is an oscillator

conventional VFO. In contrast, a VFO with an LC

where the main variable tuning capacitor is a varactor

resonant circuit can be tuned over a range of several

diode. The voltage controlled oscillator is tuned across

hundred kHz, but its frequency stability will depend

the “band” by a well regulated Dc voltage applied to the

upon its construction, and is never as good as a crystal

varactor diode, which varies the net capacitance applied

oscillator. The use of a ceramic resonator as a frequency

to the tuned circuit. The voltage controlled oscillator,

determining component fulfills both requirements.

shown in Figure 2-10, illustrates a VCO which operates

The VXO oscillator is very stable yet it can vary the

in the amateur radio band between 1.8 and 2.0 MHz.

frequency, so the oscillator can be tuned. The range of a

VXO oscillator circuit is not as wide as an LC oscillator

Buying quality variable capacitors today is often

but it offers a tuning range of 35 kHz with good

quite expensive, so VCOs are an extremely attractive

frequency stability. The somewhat unusual resonant

alternative. As an alternative, all you need is an

LC circuit at the collector of Q1 has two functions.

extremely stable and clean source of Dc power,

It improves the shape of the output signal and also

a varactor diode and a high quality potentiometer—

compensates for the amplitude drop starting at approx.

usually a 10 turn type. Note that circuit “Q” tends to be

7020 kHz. Transistor Q1 is a readily obtainable

somewhat degraded by using varactor diodes instead of

2N3904 and the ceramic resonator is a Murata SFE 7.02

variable capacitors.

M2C type or equivalent. Inductor L1 consists of two

When a reverse voltage is applied to a diode, it

coils on a T50-2 powered iron toroid. The primary

exhibits the characteristics of a capacitor. Altering the

coil is 8-turns, while the secondary coil is 2-turns.

voltage alters the capacitance. Common diodes such as

Chapter Two: Identifying Components Figure 2-8 Ceramic resonator VFO circuit 22

Chapter Two: Identifying Components

Figure 2-9

Ceramic resonator VFO pictorial circuit diagram

Figure 2-10

Voltage controlled oscillator (VCO) circuit

23

Figure 2-11

Voltage controlled oscillator (VCO) pictorial diagram

1N914 and 1N4004 can be used, but more commonly a

buffer amplifier stage. You can experiment using a small

special diode known as a varactor diode is specifically

viable capacitor trimmer, such as a 5-25 pF.

manufactured for VCO use, such as Motorola’s

The 10K potentiometer is a 10 turn “quality”

MVAM115.

potentiometer for tuning; the upper and lower trim pots

The variable capacitor in this circuit is replaced

(set and forget) allow you to adjust the voltage range of

by a varactor diode as a tuning diode, in series with

your choice that your tuning potentiometer will see. Use

capacitor C2. Note, the two, diodes back-to-back in

“quality” trimpots for these potentiometers, since they

series. Although this in effect divides total varactor

will affect the stability of the tuning of the circuit. The

diode capacitance by two, it eliminates RF energy

100K resistor and the two 0.1 µF capacitors are further

present in the tank circuit driving a single diode into

filtering. The diagram in Figure 2-11 depicts a pictorial

conduction on peaks which will increase the bias

diagram of the voltage controlled oscillator circuit.

voltage; this also gives rise to harmonics.

The circuit is shown as the components might appear

Inductor L is wound on a toroid, an Amidon T50-2

rather than as symbols in a schematic diagram. The

type which would require about 55 turns of #26 wire,

pictorial diagram often reflects an actual layout or

or even the T68-2 type requiring about 51 turns of #24

parts placement and how the parts may appear on a

wire. Both gauges mentioned are those which will

circuit board.

conveniently fit around the core. The inductor should

Now that you can identify electronics components

have a value of about 15 µH. Capacitor C2 should have

and you understand how they function in an electronics

around180 pF, and the total capacitance of C1 a/b

circuit, as well how electronics circuits are drawn, we

should be 390 pF. C4 is used to reduce the loading of

can move on to the how-to-soldering section. In the next

the tuned circuit components. Its value can be small

chapter, you will learn how to install components and

but be able to provide sufficient drive to the succeeding

how to solder the components onto a circuit board.

Chapter Two: Identifying Components

24

Chapter 3

Electronic parts installation

and soldering

Before we discuss mounting the components to the

easily identify the resistors and capacitor and proceed to

printed circuit board we should take a few minutes to

mount them on the printed circuit board.

discuss the resistor and capacitor codes which are used

Before we begin building actual electronic radio

to help identify and install these components. Table 3-1

receiver circuits, you will need to understand how to

lists the resistor color code information. Resistors

prepare the electronic components before installing them

generally have three or four color bands which help

onto the circuit board. First, you will need to know how

identify the resistor values. The color band will start

to “dress” or prepare resistor leads, which is shown in

from one edge of the resistor body; this is the first color

Figure 3-1. Resistor leads are first bent to fit the PC

code which represents the first digit, and the second

board component holes, then the resistor is mounted to

color band depicts the second digit value, while the

the circuit board. Figure 3-2 depicts how capacitor leads

third color band is the resistor’s multiplier value. The

are bent to fit the PC board holes. Once, the capacitor

fourth color band represents the resistor tolerance value.

leads are prepared, the capacitor can be installed onto

If there is no fourth band then the resistor has a 20%

the circuit board. The diagram shown in Figure 3-3

tolerance; if the fourth band is silver, then the resistor

illustrates how to prepare diode leads before mounting

has a 10% tolerance value, and if the fourth band is gold

them to the PB board. Finally, Figure 3-4 depicts

then the resistor has a 5% tolerance value. Therefore, if

transistor lead preparation, while Figure 3-5 shows how

you have a resistor with the first band having a brown

integrated circuit leads are prepared for installation.

color, the second band with a black color and a third

band with an orange color and a fourth with gold, then

one (1) times zero (0) multiplied by a value of (1000),

so the resistor will have a 10,000 ohm or 10k ohm value

Learning how to solder

with a 5% tolerance.

Now let’s move to identifying various capacitors.

Everyone working in electronics needs to know how to

When identifying and installing the ceramic, mylar or

solder well. Before you begin working on a circuit,

poly capacitors, you will need to refer to Table 3-2,

carefully read this chapter on soldering. In this section

which lists capacitor (code) values vs. actual capacitor

you will learn how to make good solder joints when

values. Most large capacitors, such as electrolytic types,

soldering point-to-point wiring connections as well as

will have their actual value printed on the body of the

for PC board soldering connections.

capacitor. But often with small capacitors they are just

In all electronics work, the wiring connections must

too small to have the actual capacitor values printed on

be absolutely secure. A loose connection in a radio

them. An abbreviated code was devised to mark the

results in noise, scratching sounds, or no sound at all.

capacitor, as shown in the table. A code marking of

In a TV, poor connections can disrupt the sound or

(104) would therefore denote a capacitor with a value of

picture. The safe operation of airplanes and the lives of

.1 µF (microfarads) or 100 nF (nanofarads). Once you

astronauts in flight depend on secure electronics

understand how these component codes work, you can

connections.

25

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Table 3-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

Figure 3-1

Preparing resistor leads for horizontal mounting

Chapter Three: Electronic Parts Installation

26

Chapter Three: Electronic Parts Installation

Table 3-2

Capacitor code identification information

This table is designed to provide the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules.

Most capacitors actually have the numeric values stamped on them; however, some are color coded and some have alphanumeric codes. The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

820 pF

Ceramic

821

2

Mylar

205

27

Figure 3-2

“Dressing” capacitor component leads

Figure 3-3

Preparing diode leads for horizontal mounting

(a) Grip outer lead near body and

(b) Grip about 2 mm down and

(c) Both leads cranked to match

bend out by 45°

bend down by 45°, parallel again

2.5 mm PC board hole spacing

Chapter Three: Electronic Parts Installation Figure 3-4 “Dressing” TO-92 transistor leads 28

Chapter Three: Electronic Parts Installation

Figure 3-5

DIL IC packages and preparing them for insertion

Soldering joins two pieces of metal, such as electrical

melting point of the solder (but below their own melting

wires, by melting them together with another metal to

point) with the soldering iron. When touched to the

form a strong, chemical bond. Done correctly, it unites

joint, this precise heating causes the solder to “flow” to

the metals so that electrically they act as one piece of

the place of highest temperature and makes a chemical

metal. Soldering is not just gluing metals together.

bond. The solder shouldn’t drip or blob, but spread

Soldering is tricky and intimidating in practice, but

smoothly, coating the entire joint. When the solder

easy to understand in theory. Basic supplies include a

cools, you should have a clean, sturdy connection.

soldering iron, which is a prong of metal that heats to a

Many people use soldering in their field, from

specific temperature through electricity, like a regular

electrical engineering and plumbing to jewelry and

iron. The solder, or soldering wire, often an alloy of

crafts. In a delicate procedure, a special material, called

aluminum and lead, needs a lower melting point than

solder, flows over two pre-heated pieces and attaches

the metal you’re joining. Finally, you need a cleaning

them through a process similar to welding or brazing.

resin called flux that ensures the joining pieces are

Various metals can be soldered together, such as gold

incredibly clean. Flux removes all the oxides on the

and sterling silver in jewelry, brass in watches and

surface of the metal that would interfere with the

clocks, copper in water pipes, or iron in leaded glass

molecular bonding, allowing the solder to flow into

stained windows. All these metals have different

the joint smoothly. You also need two things to solder

melting points, and therefore use different solder. Some

together.

“soft” solder, with a low melting point, is perfect for

The first step in soldering is cleaning the surfaces,

wiring a circuit board. Other “hard” solder, such as for

initially with sandpaper or steel wool and then by

making a bracelet, needs a torch rather than a soldering

melting flux onto the parts. Sometimes, flux is part of

iron to get a hot enough temperature. Electrical

the alloy of the soldering wire, in an easy-to-use

engineers and hobbyists alike can benefit from learning

mixture. Then, the pieces are both heated above the

the art and science of soldering.

29

For circuit construction, only use fluxes or

Solder

solder-flux combinations that are labeled for

electronic soldering.

The best solder for electronics work is 60/40 rosin-core

The rosin or the acid is a flux. Flux removes oxide by

solder. It is made of 60% tin and 40% lead. This mixture

suspending it in solution and floating it to the top. Flux

melts at a lower temperature than either lead or tin

is not a cleaning agent! Always clean the work before

alone. It makes soldering easy and provides good

soldering. Flux is not a part of a soldered connection—

connections. The rosin keeps the joint clean as it is

it merely aids the soldering process. After soldering,

being soldered. The heat of the iron often causes a

remove any remaining flux. Rosin flux can be removed

tarnish or oxide to form on the surface. The rosin

with isopropyl or denatured alcohol. A cotton swab is a

dissolves the tarnish to make the solder cling tightly.

good tool for applying the alcohol and scrubbing the

Solders have different melting points, depending on

excess flux away. Commercial flux-removal sprays are

the ratio of tin to lead. Tin melts at 450°F and lead at

available at most electronic-part distributors.

621°F. Solder made from 63% tin and 37% lead melts

at 361°F, the lowest melting point for a tin and lead

mixture. Called 63-37 (or eutectic), this type of solder

The soldering iron

also provides the most rapid solid-to-liquid transition

and the best stress resistance. Solders made with

Soldering is used in nearly every phase of electronic

different lead/tin ratios have a plastic state at some

construction so you’ll need soldering tools. A soldering

temperatures. If the solder is deformed while it is in the

tool must be hot enough to do the job and lightweight

plastic state, the deformation remains when the solder

enough for agility and comfort. A temperature controlled

freezes into the solid state. Any stress or motion applied

iron works well, although the cost is not justified for

to “plastic solder” causes a poor solder joint.

occasional projects. Get an iron with a small conical or

The 60-40 solder has the best wetting qualities.

chisel tip. Soldering is not like gluing; solder does more

Wetting is the ability to spread rapidly and bond

than bind metal together and provide an electrically

materials uniformly; 60-40 solder also has a low

conductive path between them. Soldered metals and

melting point. These factors make it the most commonly

the solder combine to form an alloy.

used solder in electronics.

You may need an assortment of soldering irons to

Some connections that carry high current can’t be

do a wide variety of soldering tasks. They range in size

made with ordinary tin-lead solder because the heat

from a small 25-watt iron for delicate printed-circuit

generated by the current would melt the solder.

work to larger 100 to 300-watt sizes used to solder large

Automotive starter brushes and transmitter tank

surfaces. If you could only afford a single soldering tool

circuits are two examples. Silver-bearing solders have

when initially setting up your electronics workbench

higher melting points, and so prevent this problem.

than, an inexpensive to moderately priced pencil-type

High-temperature silver alloys become liquid in the

soldering iron with between 25 and 40-watt capacity

1100°F to l200°F range, and a silver-manganese

is the best for PC board electronics work. A 100-watt

(85-15) alloy requires almost 1800°F.

soldering gun is overkill for printed-circuit work, since

Because silver dissolves easily in tin, tin bearing

it often gets too hot, cooking solder into a brittle mess

solders can leach silver plating from components. This

or damaging small parts of a circuit. Soldering guns are

problem can greatly reduced by partially saturating the

best used for point-to-point soldering jobs, for large

tin in the solder with silver or by eliminating the tin.

mass soldering joints or large components. Small

Tin-silver or tin-lead-silver alloys become liquid at

“pencil” butane torches are also available, with optional

temperatures from 430°F for 96.5-3.5 (tin-silver), to

soldering-iron tips. A small butane torch is available

588°F for 1.0-97.5-1.5 (tin-lead-silver). A 15.080.0-5.0

from the Solder-It Company. Butane soldering irons are

alloy of lead-indium-silver melts at 314°F.

ideal for field service problems and will allow you to

Never use acid-core solder for electrical work.

solder where there is no 110 volt power source. This

It should be used only for plumbing or chassis work.

company also sells a soldering kit that contains paste

Chapter Three: Electronic Parts Installation

30

Chapter Three: Electronic Parts Installation

solders (in syringes) for electronics, pot metal and

A soldering station usually consists of a temperature

plumbing. See the Appendix for the address

controlled soldering iron with an adjustable heat or

information.

temperature control and a soldering iron holder and

Keep soldering tools in good condition by keeping

cleaning pad. If you are serious about your electronics

the tips well tinned with solder. Do not run them at full

hobby or if you have been involved with electronics

temperature for long periods when not in use. After

building and repair for any length of time, you will

each period of use, remove the tip and clean off any

eventually want to invest in a soldering station at some

scale that may have accumulated. Clean an oxidized tip

point in time. There are real low cost soldering station

by dipping the hot tip in sal ammoniac (ammonium

for hobbyists, for under $30, but it makes more sense to

chloride) and then wiping it clean with a rag. Sal

purchase a moderately price soldering station such as

ammoniac is somewhat corrosive, so if you don’t

the quality Weller series. A typical soldering station is

wipe the tip thoroughly, it can contaminate electronic

shown in Figure 3-6.

soldering. You can also purchase a small jar of “Tip

Tinner,” a soldering iron tip dresser, from your local

Soldering gun

Radio Shack store. Place the tip of the soldering iron

into the “Tip Tinner” after every few solder joints.

An electronics workbench would not be complete

If a copper tip becomes pitted, file it smooth and

without a soldering gun. Soldering guns are useful for

bright and then tin it immediately with solder. Modern

soldering large components to terminal strips, or

soldering iron tips are nickel or iron clad and should

splicing wires together or when putting connectors on

not be filed. The secret of good soldering is to use the

coax cable. There are many instances where more heat

right amount of heat. Many people who will have not

is needed than a soldering iron can supply. For example,

soldered before use too little heat dabbing at the joint to

a large connector mass cannot be heated with a small

be soldered and making little solder blobs that cause

soldering iron, so you would never be able to “tin” a

unintended short circuits. Always use caution when

connector with a small wattage soldering iron. A

soldering. A hot soldering iron can burn your hand

soldering gun is a heavy duty soldering device which

badly or ruin a tabletop. It’s a good idea to buy or make

does in fact look like a gun. Numerous tips are available

a soldering iron holder.

for a soldering gun and they are easily replaceable using

two small nuts on the side arm of the soldering gun.

Soldering guns are available in two main heat ranges.

Soldering station

Often when building or repairing a circuit, your

soldering iron is kept switched “on” for unnecessarily

long periods, consuming energy and allowing the

soldering iron tip to burn and develop a buildup of

oxide. Using this soldering-iron temperature controller,

you will avoid destroying sensitive components when

soldering.

Buying a lower wattage iron may solve some of the

problems, but new problems arise when you want to

solder some heavy-duty component, setting the stage for

creating a “cold” connections. If you’ve ever tried to

troubleshoot some instrument in which a cold solder

joint was at the root of the problem, you know how

difficult such defects are to locate. Therefore, the best

way to satisfy all your needs is to buy a temperature

controller electronics workbench.

Figure 3-6

Temperature controlled soldering station

31

Most soldering guns have a two-step “trigger” switch

cool without movement at room temperature. It usually

which enable you to select two heat ranges for different

takes no more than a few seconds. If the joint is moved

soldering jobs. The most common soldering gun

before it is cool, it may take on a dull, satin look that is

provides both a 100 watt setting when the “trigger”

characteristic of a “cold” solder joint. Reheat cold joints

switch is pressed to its first setting, and as the “trigger”

until the solder flows freely and hold them still until

switch is advanced to the next step, the soldering gun

cool. When the iron is set aside, or if it loses its shiny

will provide 150 watts, when more heat is needed.

appearance, wipe away any dirt with a wet cloth or

A larger or heavy-duty soldering gun is also available,

sponge. If it remains dull after cleaning, tin it again.

but a little harder to locate is the 200 to 250 watt solder

Overheating a transistor or diode while soldering can

gun. The first “trigger” switch position provides 200 watts,

cause permanent damage. Use a small heatsink when

while the second switch position provides the 250 watt

you solder transistors, diodes or components with

heat setting. When splicing wires together either using

plastic parts that can melt. Grip the component lead

the “Western Union” or parallel splice or the end splice,

with a pair of pliers up close to the unit so that the heat

a soldering gun should be used especially if the wire

is conducted away. You will need to be careful, since it

gauge is below size 22 ga. Otherwise the solder may

is easy to damage delicate component leads. A small

not melt properly and the connections may reflect a

alligator clip also makes a good heatsink to dissipate

“cold” solder joint and therefore a poor or noisy splice.

from the component.

Soldering wires to binding post connections should be

Mechanical stress can damage components, too.

performed with a soldering gun to ensure proper heating

Mount components so there is no appreciable mechanical

to the connection. Most larger connectors should be

strain on the leads.

soldered or pre-tinned using a soldering gun for even

solder flow.

Soldering to the pins of coil forms male cable plugs

can be difficult. Use suitable small twist drill to clean

the inside of the pin and then tin it with resin-core

Preparing the soldering iron

solder. While it is still liquid, clear the surplus solder

from each pin with a whipping motion or by blowing

If your iron is new, read the instructions about preparing

through the pin from the inside of the form or plug.

it for use. If there are no instructions, use the following

Watch out for flying hot solder, you can get severe

procedure. It should be hot enough to melt solder

burns. Next, file the nickel tip. Then insert the wire and

applied to its tip quickly (half a second when dry,

solder it. After soldering, remove excess solder with a

instantly when wet with solder). Apply a little solder

file, if necessary. When soldering to the pins of plastic

directly to the tip so that the surface is shiny. This

coil-forms, hold the pin to be soldered with a pair of

process is called “tinning” the tool. The solder coating

heavy pliers to form a heatsink. Do not allow the pin to

helps conduct heat from the tip to the joint face, the tip

overheat; it will loosen and become misaligned.

is in contact with one side of the joint. If you can place

the tip on the underside of the joint, do so. With the tool

below the joint, convection helps transfer heat to the

Preparing work for soldering

joint. Place the solder against the joint directly opposite

the soldering tool. It should melt within a second for

If you use old junk parts, be sure to completely clean all

normal PC connections, within two seconds for most

wires or surfaces before applying solder. Remove all

other connections. If it takes longer to melt, there is not

enamel, dirt, scale, or oxidation by sanding or scraping

enough heat for the job at hand. Keep the tool against

the parts down to bare metal. Use fine sandpaper or

the joint until the solder flows freely throughout the

emery paper to clean flat surfaces or wire. (Note, no

joint. When it flows freely, solder tends to form concave

amount of cleaning will allow you to solder to aluminum.

shapes between the conductors. With insufficient heat

When making a connection to a sheet of aluminum, you

solder does not flow freely; it forms convex shapes-

must connect the wire by a solder lug or a screw.)

blobs. Once solder shape changes from convex to

When preparing wires, remove the insulation with

Chapter Three: Electronic Parts Installation concave, remove the tool from the joint. Let the joint wire strippers or a pocketknife. If using a knife, do not

32

Chapter Three: Electronic Parts Installation

cut straight into the insulation; you might nick the wire

Solder comes in gauges like wire. The two most

and weaken it. Instead, hold the knife as if you were

common types of solder, are 18 ga., used for general

sharpening a pencil, taking care not to nick the wire as

work, and the thinner 22 ga., used for fine work on

you remove the insulation. For enameled wire, use the

printed circuit boards.

back of the knife blade to scrape the wire until it is

clean and bright. Next, tin the clean end of the wire.

A well-soldered joint depends on

Now, hold the heated soldering-iron tip against the

under surface of the wire and place the end of the

1.

Soldering with a clean, well-tinned tip.

rosin-core solder against the upper surface. As the

solder melts, it flows on the clean end of the wire.

2.

Cleaning the wires or parts to be soldered.

Hold the hot tip of the soldering iron against the under

3.

Making a good mechanical joint before soldering.

surface of the tinned wire and remove the excess solder

4.

Allowing the joint to get hot enough before

by letting it flow down on the tip. When properly

applying solder.

tinned, the exposed surface of the wire should be

covered with a thin, even coating of solder.

5.

Allowing the solder to set before handling or

moving soldered parts.

How to solder

Making a good mechanical joint

The two key factors in quality soldering are time and

Unless you are creating a temporary joint, the next step

temperature. Generally, rapid heating is desired,

is to make a good mechanical connection between the

although most unsuccessful solder jobs fail because

parts to be soldered. For instance, wrap the wire

insufficient heat has been applied. Be careful; if heat is

carefully and tightly around a soldering terminal or

applied too long, the components or PC board can be

soldering lug, as shown in Figure 3-7. Bend wire and

damaged, the flux may be used up and surface oxidation

make connections with long-nosed pliers. When

can become a problem. The soldering-iron tips should be

connecting two wires together, make a tight splice

hot enough to readily melt the solder without burning,

before soldering. Once you have made a good

charring or discoloring components, PC boards or wires.

mechanical contact, you are ready for the actual

Usually, a tip temperature about 100°F above the solder

soldering.

melting point is about right for mounting components

on PC boards. Also, use solder that is sized appropriately

The next step is to apply the soldering iron to the

for the job. As the cross-section of the solder decreases,

connection, soldering the connection as shown.

so does the amount of heat required to melt it.

Diameters from 0.025 to 0.040 inches are good for

nearly all circuit wiring.

Always use a good quality multi-core solder.

A standard 60% tin, 40% lead alloy solder with cores

of non-corrosive flux will be found easiest to use. The

flux contained in the longitudinal cores of multi-core

solder is a chemical designed to clean the surfaces to be

joined of deposited oxides, and to exclude air during the

soldering process, which would otherwise prevent these

metals coming together. Consequently, don’t expect to

be able to complete a joint by using the application of

the tip of the iron loaded with molten solder alone, as

this usually will not work. Having said that, there is a

process called tinning where conductors are first coated

in fresh, new solder prior to joining by a hot iron.

Figure 3-7

Wire to lug soldering joint

33

pitted, granular appearance as seen in Figure 3-8. reheat

the joint, scrape off the solder, and clean the connection.

Then start over again. After the solder is well set, pull

on the wire to see if it is a good, tight connection. If you

find that you made a poor soldering job don’t get upset,

be thankful you found it and do it over again. A quick

reference solder check list is shown in the listing in

Table 3-3.

Soldering printed circuit boards

Most electronic devices use one or more printed circuit

(PC) boards. A PC board is a thin sheet of fiberglass

or phenolic resin that has a pattern of foil conductors

Figure 3-8

Inferior wire to lug solder joint

“printed” on it. You insert component leads into holes

in the board and solder the leads to the foil pattern.

In soldering a wire splice, hold the iron below the splice

This method of assembly is widely used and you will

and apply solder to the top of the splice. If the tip of the

probably encounter it if you choose to build from a

iron has a bit of melted solder on the side held against

kit. Printed circuit boards make assembly easy. First,

the splice, heat is transferred more readily to the splice

insert component leads through the correct holes in the

and the soldering is done more easily. Don`t try to

circuit board. Mount parts tightly against the circuit

solder by applying solder to the joint and then pressing

board unless otherwise directed. After inserting a lead

down on it with the iron. Be sure not to disturb the

into the board, bend it slightly outward to hold the part

soldered joint until the solder has set. It may take a

in place.

few seconds for the solder to set, depending upon the

When the iron is hot, apply some solder to the

amount of solder used in making the joint. Now take a

flattened working end at the end of the bit, and wipe it

good look at the joint. It should have a shiny, smooth

on a piece of damp cloth or sponge so that the solder

appearance—not pitted or grainy. If it does have a

forms a thin film on the bit. This is tinning the bit.

Table 3-3

Soldering check list

1. Prepare the joint. Clean all surfaces and conductors thoroughly with fine steel wool. First, clean the circuit traces, then clean the component leads.

2. Prepare the soldering iron or gun. The soldering device should be hot enough to melt solder applied to the tip.

Apply a small amount of solder directly to the tip, so that the surface is shiny.

3. Place the tip in contact with one side of the joint, if possible place the tip below the joint.

4. Place the solder against the joint directly opposite the soldering tool. The solder should melt within two seconds; if it takes longer use a larger iron.

5. Keep the soldering tool against the joint until the solder flows freely throughout the joint. When it flows freely the joint should form a concave shape; insufficient heat will form a convex shape.

6. Let the joint cool without any movement, the joint should cool and set-up with in a few seconds. If the joint is moved before it cools the joint will look dull instead of shiny and you will likely have a cold solder joint. Re-heat the joint and begin anew.

7. Once the iron is set aside, or if it loses its shiny appearance, wipe away any dirt with a wet cloth or wet sponge.

Chapter Three: Electronic Parts Installation

When the iron is clean the tip should look clean and shiny. After cleaning the tip apply some solder.

34

Chapter Three: Electronic Parts Installation

Melt a little more solder on to the tip of the soldering

iron, and put the tip so it contacts both parts of the joint.

It is the molten solder on the tip of the iron that allows

the heat to flow quickly from the iron into both parts of

the joint. If the iron has the right amount of solder on it

and is positioned correctly, then the two parts to be

joined will reach the solder’s melting temperature in a

couple of seconds. Now apply the end of the solder to

the point where both parts of the joint and the soldering

iron are all touching one another. The solder will melt

immediately and flow around all the parts that are at, or

over, the melting part temperature. After a few seconds

remove the iron from the joint. Make sure that no parts

of the joint move after the soldering iron is removed

until the solder is completely hard. This can take quite a

Figure 3-9

Proper technique for soldering

few seconds with large joints. If the joint is disturbed

components on PC board

during this cooling period it may become seriously

weakened.

The most important point in soldering is that both

the joint properly in the first place. Anyone can learn to

parts of the joint to be made must be at the same

solder, it just takes practice.

temperature. The solder will flow evenly and make a

The diagram in Figure 3-9 shows how to solder a

good electrical and mechanical joint only if both parts

component lead to a PC board pad. The tip of the

of the joint are at an equal high temperature. Even

soldering iron heats both the lead and the copper pad,

though it appears that there is a metal-to-metal contact

so the end of the solder wire melts when it’s pushed

in a joint to be made, very often there exists a film of

into the contact. The diagram illustrated in Figure 3-10

oxide on the surface that insulates the two parts. For this

shows how a good solder joint is obtained. Notice that it

reason it is no good applying the soldering iron tip to

has a smooth and shiny “fillet” of solder metal, bonding

one half of the joint only and expecting this to heat the

all around to both the component lead and the copper

other half of the joint as well.

pad of the PC board. This joint provides a reliable

It is important to use the right amount of solder, both

electrical connection.

on the iron and on the joint. Too little solder on the iron

Try to make the solder joint as quickly as possible

will result in poor heat transfer to the joint, too much

because the longer you take, the higher the risk that the

and you will suffer from the solder forming strings as

component itself and the printed circuit board pad and

the iron is removed, causing splashes and bridges to

track will overheat and be damaged. But don’t work so

other contacts. Too little solder applied to the joint will

quickly that you cannot make a good solder joint.

give the joint a half finished appearance: a good bond

where the soldering iron has been, and no solder at all

on the other part of the joint.

The hard cold solder on a properly made joint should

have a smooth shiny appearance and if the wire is

pulled it should not pull out of the joint. In a properly

made joint the solder will bond the components very

strongly indeed, since the process of soldering is similar

to brazing, and to a lesser degree welding, in that the

solder actually forms a molecular bond with the

surfaces of the joint. Remember it is much more

difficult to correct a poorly made joint than it is to make

Figure 3-10

Excellent solder joint

35

The finished connection should be smooth and bright.

Reheat any cloudy or grainy-looking connections.

Finally, clip off the excess wire length, as shown in

Figure 3-13.

Occasionally a solder “bridge” will form between

two adjacent foil conductors. You must remove these

bridges; otherwise a short circuit will exist between the

two conductors. Remove a solder bridge by heating the

bridge and quickly wiping away the melted solder with

Figure 3-11

Inferior solder joint: Example 1

a soft cloth. Often you will find a hole on the board

plugged by solder from a previous connection. Clear the

hole by heating the solder while pushing a component

Having to solder the joint over again always increases

lead through the hole from the other side of the board.

the risk of applying too much heat to the PCB.

Good soldering is a skill that is learnt by practice.

As the solder solidifies, take a careful look at the

joint you have made, to make sure there’s a smooth

How to un-solder

and fairly shiny metal “fillet” around it. This should be

broadly concave in shape, showing that the solder has

In order to remove components, you need to learn the

formed a good bond to both metal surfaces. If it has a

art of de-soldering. You might accidentally make a

rough and dull surface or just forms a “ball” on the

wrong connection or have to move a component that

component lead, or a “volcano” on the PCB pad

you put in an incorrect location. Take great care while

with the lead emerging from the crater, you have a

un-soldering to avoid breaking or destroying good parts.

“dry joint.” If your solder joint looks like the picture

The leads on components such as resistors or transistors

shown in Figure 3-11, you will have to re-solder the

and the lugs on other parts may sometimes break off

joint over again. Figure 3-12 shows another type of dry

when you are un-soldering a good, tight joint. To avoid

solder joint which would have to be re-soldered. These

heat damage, you must use as much care in un-soldering

types of “dry” solder joints if now redone will cause the

delicate parts as you do in soldering them. There are

circuit to be unreliable and intermittent.

three basic ways of un-soldering. The first method is to

For projects that use one or more integrated circuits,

heat the joint and “flick” the wet solder off. The second

with their leads closely-spaced pins, you may find it

method is to use a metal wick or braid to remove the

easier to use a finer gauge solder, i.e. less than 1 mm in

melted solder. This braid is available at most electronics

diameter. This reduces the risk of applying too much

solder to each joint, and accidentaly forming “bridges”

between pads to PC “tracks.”

Chapter Three: Electronic Parts Installation Figure 3-12 Inferior solder joint: Example 2

Figure 3-13

Trimming excess component leads

36

Chapter Three: Electronic Parts Installation

parts stores; use commercially made wicking material

which are used to uniformly de-solder all IC pins

(braid). Place the braid against the joint that you want to

quickly and evenly, so as not to destroy the circuit

un-solder. Use the heated soldering iron to gently press

board. The specialized soldering tips are often used in

the braid against the joint. As the solder melts, it is

conjunction with vacuum systems to remove the solder

pulled into the braid. By repeating this process,

at the same time.

you can remove virtually all the solder from the joint.

Then re-heat the joint and lift off the component

Remember these things

leads. Another useful tool is an air-suction solder

remover.

when un-soldering:

Most electronics parts stores have these devices.

1.

Be sure there is a little melted solder on the tip of

Before using a de-solder squeeze bulb, use your

your iron so that the joint will heat quickly.

soldering iron to heat the joint you want to un-solder

until the solder melts. Then squeeze the bulb to create

2.

Work quickly and carefully to avoid heat damage to

a vacuum inside. Touch the tip of the bulb against the

parts. Use long-nosed pliers to hold the leads of

melted solder. Release the bulb to suck up the molten

components just as you did while soldering.

solder. Repeat the process until you’ve removed most

3.

When loosening a wire lead, be careful not to bend

of the solder from the joint. Then re-heat the joint and

the lug or tie point. Use pieces of wire or some old

gently pry off the wires. This third method is easy, and

radio parts and wire. Practice until you can solder

is the preferred method, since it is fast and clean. You

joints that are smooth, shiny, and tight. Then

can use a vacuum device to suck up molten solder.

practice un-soldering connections until you are

There are many new styles of solder vacuum devices

satisfied that you can do them quickly and without

on the market that are much better than the older

breaking wires or lugs.

squeeze bulb types. The new vacuum de-soldering tools

are about 8 to 12 inches long with a hollow Teflon tip.

Caring for your soldering iron

You draw the vacuum with a push handle and set it.

As you re-heat the solder around the component to be

To get the best service from your soldering iron, keep it

removed, you push a button on the device to suck the

cleaned and well tinned. Keep a damp cloth on the

solder into the chamber of the de-soldering tool.

bench as you work. Before soldering a connection, wipe

the tip of the iron across the cloth, then touch some

De-soldering station

fresh solder to the tip. The tip will eventually become

worn or pitted. You can repair minor wear by filing the

A de-soldering station is a very useful addition to an

tip back into shape. Be sure to tin the tip immediately

electronics workshop or workbench, but in many cases

after filing it. If the tip is badly worn or pitted, replace

they just cost too much for most hobbyists. De-soldering

it. Replacement tips can be found at most electronics

stations are often used in production environments or as

parts stores. Remember that oxidation develops more

re-work stations, when production changes warrant

rapidly when the iron is hot. Therefore, do not keep the

changes to many circuit boards in production. Some

iron heated for long periods unless you are using it.

repair shops used de-soldering stations to quickly and

Do not try to cool an iron rapidly with ice or water.

efficiently remove components.

If you do, the heating element may be damaged and

Another useful de-soldering tool is one made

need to be replaced or water might get into the barrel

specifically for removing integrated circuits. The

and cause rust. Take care of your soldering iron and it

specially designed de-soldering tip is made the same

will give you many years of useful service.

size as the integrated circuit, so that all IC pins can be

Remember, soldering equipment gets hot! Be careful.

de-soldered at once. This tool is often combined with a

Treat a soldering burn as you would any other. Handling

vacuum suction device to remove the solder as all the

lead or breathing soldering fumes is also hazardous.

IC pins are heated. The IC de-soldering tips are made in

Observe these precautions to protect yourself and

various sizes; there are 8 pin, 14 pin and 16 pin versions,

others!

37

fumes into the carbon filter to eliminate them. This is

Ventilation

the most simple method of reducing or eliminating

solder fumes from the immediate area. If there is a

Properly ventilate the work area where you will be

window near your soldering area, be sure to open the

soldering. If you can smell fumes, you are breathing

window to reduce the exposure to solder fumes. Another

them. Often when building a new circuit or repairing a

method of reducing or eliminating solder fumes is to buy

“vintage” circuit you may be soldering continuously

or build a solder smoke removal system. You can purchase

for a few hours at a time. This can mean you will be

one of these systems but they tend to be quite expensive.

breathing solder fumes for many hours and the fumes

You can create your own solder smoke removal system

can cause you to get dizzy or lightheaded. This is

by locating or purchasing an 8 to 10 foot piece of 2 inch

dangerous because you could fall down and possibly

diameter flexible hose, similar to your vacuum cleaner

hurt yourself in the process. Many people highly

hose. At the solder station end of the hose, you can affix

allergic are also allergic to the smell of solder fumes.

the hose to a wooden stand in front of your work area.

Solder fumes can cause sensitive people to get sinus

The other end of the hose is funneled into a small

infections. So ventilating solder fumes is an important

square “muffin” type fan placed near a window. Be sure

subject. There are a few different ways to handle this

to wash your hands after soldering, especially before

problem. One method is to purchase a small fan unit

handling food, since solder contains lead; also try to

housed with a carbon filter which sucks the solder

minimize direct contact with flux and flux solvents.

Chapter Three: Electronic Parts Installation

38

Chapter 4

AM, FM, and Shortwave

Crystal Radio Projects

D1

1N34 or rock crystal

Parts list

diode

L1

5 turns AWG #18

Simple Crystal Radio

bare copper or silver

L1

150 turns of 24 ga.

wire, 12 mm inside

enameled wire on

diameter, tapped at

4” × 2” dia tube

2.5 turns

C1

365 pF tuning

H1

high impedance

capacitor (old radio)

headphones (crystal

D1

1N34 germanium diode

type of 2k ohm type)

(not a silicon diode)

Ant

antenna- 7” of

C2

.005 µF, 35 volt

#18 bare copper wire

disk capacitor

Misc

wood block, wire,

H1

high impedance

hardware, clips, etc.

headphones (crystal

Supersensitive

or 2000k type)

AM/Shortwave Crystal

ANT

80–100 foot long

Radio

wire antenna

L1

11 turns, 22 ga.

GND

cold water pipe or

enameled wire on

ground rod

27/8” cardboard form

Misc

wood block, coil

L2 (AM)

54 turns,

tube, hardware,

22 ga. enameled wire

screws, clips,

on 3” air-core form

washers, Krylon spray,

Taps are brought

wire, etc.

out at 40T, 27T,

FM Crystal Radio Set

15T and 6T

R1

47k ohm 1/4 watt, 5%

L2 (SW)

15 turns,

resistor

22 ga. enameled wire

C1

82 pF capacitor

on 3” air-core form

C2

80 pF air variable

Taps are brought

capacitor

out at 12T, 9T, 6T

C3

18 pF capacitor

and 3T

39

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

D1

germanium diode or

wave that radiates from its transmitting antenna. The

galena crystal

AM transmitter sends out a fixed frequency carrier

w/”cat’s whisker”

wave. When sound is present in the program material,

C1

500 pF turning

the strength, or amplitude, of these waves is made to

capacitor

vary in response to the audio content of the program.

The resulting wave is called an amplitude modulated

C2

.001 µF, 35 volt

wave. See Figure 4-1.

disk capacitor

The purpose of a simple AM or crystal radio receiver

S1

single-pole –

is to pick up these AM waves and extract the audio signal

5-position rotary

so that it can be heard by the listener. It does this by a

switch

process called “detection.” The detection process utilizes

S2

single-pole -

a device called a detector which effectively strips off

6-position rotary

either the upper half or lower half of the AM wave.

switch

It only remains to filter out the carrier wave to leave the

H1

crystal headphone

audio signal and the job is done! The following diagram

or 2k headphones

shows how the detector and filter work together to

(Baldwin, Brandes)

“recover” the original audio signal. The strength of the

recovered audio signal is small but, given the right

ANT 80–100 foot long

conditions, it can be large enough to drive a pair of

wire antenna

headphones; all without any power source other than the

GND cold water pipe or

signal itself.

ground rod

The diagram shown in Figure 4-2 illustrates a basic

Misc wood block,

crystal radio. In its simplest form, a crystal radio is

hardware, wire, clips,

composed of just our main components. A good

screws, Krylon, etc.

antenna, a detector, a filter capacitor and pair of

A crystal radio is the simplest form of AM (amplitude

headphones. The basic diagram shows the input section

modulation) receiver ever invented. It has great potential

at (A), the rectifier section at (B), the filter section

for experimentation and usually requires no source of

at (C) and finally the headphones at section (D).

power for its operation other than the radio signal itself,

The antenna consists of a length of wire suspended

and costs little. Most people do not realize that crystal

above the ground, while the ground or earth connection

radios can be built to pickup shortwave as well as FM

could be a metal spike driven into the ground. When a

radio signals. Did you know that you can build very

sensitive and selective crystal radios far better than

most commercial AM radios! Ever thought of building

a crystal radio? Building a crystal radio will give you

Modulation Envelope

immense satisfaction, and the results are sure to please.

+

Carrier Wave

Crystal sets date back to the earliest days of wireless

(pre-W.W.I) and an enormous variety of circuit designs

have been produced over the years. Their popularity has

Time

been variable as developments in other more elaborate

0

forms of reception have taken place. However,

Amplitude

fascination with this crystal radio design, building and

experimentation, is still very strong today with national

Amplitude Modulation

−

and international organizations and clubs offering

of a Carrier Wave

competitions.

So how does a crystal radio work? An AM transmitter

Chapter Four: AM, FM, and Shortwave Crystal Radio Projects sends out its broadcast in the form of an electromagnetic Figure 4-1

Amplitude modulation

40

Chapter Four: AM, FM, and Shortwave Crystal Radio Projects

Figure 4-2

Basic crystal radio

capacitor is connected in parallel with an inductor and

to be particularly good at detection, and became very

an alternating voltage applied across the combination,

popular for building crystal radios. The detector consists

alternating current will flow. The amount of current that

of galena in a small cup or tin. A small coil of wire,

flows depends upon the frequency of the applied

with one free end was called the “cat’s whisker” which

voltage. At a particular frequency, called the resonant

was used to make contact with the crystal.

frequency, almost no current flows. For frequencies

The remaining uni-directional current is filtered by

above or below the resonant frequency, significant

the combined effect of the headphone impedance and

current will flow. In Figure 4-2, capacitor C1 plus the

the capacitor at C2 and only the desired audio signal

aerial capacitance forms the capacitor of our tuned

current passes on through to the headphones at H1.

circuit, while L1 forms the inductor. At the resonant

One drawback with the very simple circuit shown is

frequency of the tuned circuit, almost no current flows

that it has little selectivity. That is, it picks up all AM

to earth through L1 or C1, leaving virtually all of it free

broadcast signals with similar efficiency and often close

to flow through the detector. Alternating currents at

together. So as time passed more advanced, more

broadcast frequencies either above or below the

sensitive and more selective receivers were born.

resonant frequency will tend to flow through C1 or L1

Let’s construct a simple crystal radio. In order to build

to earth. Thus we have added selectivity to the receiver.

the crystal radio shown in Figure 4-3, you will need to

Notice that C1 is adjustable, as signified by the arrow.

secure some tools and supplies. First you will need to

By varying C1 we can tune the receiver to select

find a clean well lit work bench or table to spread out all

specific broadcast frequencies.

your tools, charts, diagrams and components. You will

The main requirement for a detector is that it should

also need to secure a soldering iron, some 60/40 rosin

act as a non-return “valve” or one-way “switch” to the

core solder and a small jar of “Tip Tinner,” a soldering

alternating currents of the AM wave. If you could look

iron tip cleaner/dresser, obtainable from your local

at the alternating current in a circuit you would see it

Radio Shack store. You will also want to locate some

flowing back and forth, first one way and then the other.

small tools such a pair of end-cutters, a pair of needle-

A detector placed in such a circuit allows the alternating

nose pliers, a magnifying glass and a set of Phillips and

current to flow easily in one direction but not in the

flat-blade screwdrivers for this project. Grab the crystal

other. Certain naturally occurring minerals were found

radio schematic, see Figure 4-2, and the resistor and

to have this property and these became some of the

capacitor identification charts, and place them in front

earliest forms of detectors. One such mineral, the

of you, so we can get started building the project. The

crystalline form of galena (lead sulphide), was found

resistor identification chart in Table 4-1 will help you

41

the resistor’s second digit of the value. The third colored

band is the resistor’s multiplier value. For example, a

resistor whose first color band is yellow represents a

digit four (4), while a second color band which is violet

is seven (7). If the third color band is orange, then the

multiplier would be (000) or one thousand, so the value

would be 47,000 or 47k ohms. Resistors usually have a

fourth colored band which represents the resistor’s

tolerance value. A silver band denotes a 10% tolerance

value, while a gold band denotes a 5% tolerance

resistor. No color band represents a tolerance

value of 20%.

Our crystal radio projects in this chapter all utilize

capacitors of some sort. Capacitors usually are available

in two major classifications, polarized and non-

polarized. The project in this chapter will utilize only

non-polarized capacitors. Non-polarized capacitors can

often be physically very small and not have their actual

Figure 4-3

AM crystal radio

value printed on the body of the capacitor, so a chart

was developed to help identify a capacitor using a

three-digit code. See Table 4-2.

identify resistors needed for the some of the projects in

this chapter. Each resistor will have three or four colored

As this project will not require a circuit board, we

bands on the body of the resistor. These colors identify

will build the crystal radio on a 6′′ × 6′′ × 3⁄4′′ wood

the resistor’s value. The color bands start at one end of

block base. You can elect to use an additional piece of

the resistor, the first colored band is the first digit of the

wood at a right angle to the base as a front panel to

resistor’s value, while the second resistor represents

secure the tuning capacitor as shown in Figure 4-3.

Table 4-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Four: AM, FM, and Shortwave Crystal Radio Projects

No color

20%

42

Chapter Four: AM, FM, and Shortwave Crystal Radio Projects

Table 4-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.001 5µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

820 pF

Ceramic

821

2

Mylar

205

43

Next, you will need to locate a plastic or cardboard tube

diode to give the radio an “old-time” look if desired:

approximately 31⁄2 to 4′′ long by 2′′ in diameter on which

see the Appendix for Antique Radio Supply.

to wind your coil. Punch a hole at both ends of the tube

Connect an antenna and a ground wire to rod in the

about 1⁄2′′ from the actual end of the tube. Start winding

ground or an electrical ground in your house and your

the coil at one end of the tube using #24 ga. enameled

crystal radio will be ready to test out. The ground wire

wire, leave about 6′′ of wire free at the first hole to

can be attached to a metal cold water pipe, or to a metal

allow connection to the circuit. Wind the coil with each

rod stuck a couple of feet into the earth. Do not attach it

winding touching the previous winding but not

to a line carrying gas or electricity. The crystal radio

overlapping the prior winding. Wind about

will operate forever without a power supply, but you do

150 turns of wire across the length of the tube. After

need a good antenna to make the radio work well. The

winding about 150 turns take the free end of the

simplest outdoor antenna for receiving signals is a

remaining wire and put it through the last punched hole,

horizontal wire with the lead-in wire to the set

leave about 6′′ of wire so you can connect the coil to the

connected on one end. An insulated wire 50 to 100 feet

circuit. When you are finished winding the coil, you

long placed as high and clear of surrounding objects as

can varnish the coil winding or just spray Krylon

possible works best: see Figure 4-4. Both ends of the

around the coil to keep the winding close to the coil,

antenna should have insulators and rigid support. Tree

so they won’t spread out or come loose. Fasten the coil

branches are not good because they sway in the wind.

to a 6′′ × 6′′ wood block; you can mount the coil upright

If you use a tree trunk, have slack in the wire so it can

as shown in Figure 4-3, or you can lay the coil down

move without pulling the wire. Keep the antenna wire

near one edge of the wood block and secure it to the

far away from chimneys, metal roofs, gutters, drain

block with some brackets or clips. You will have to use

pipes, telephone, and especially power lines. The

a knife and scrape off the enameled insulation of the

antenna and lead-in should be one continuous piece of

two coil wires before you can fasten or solder them to

wire. Use stranded copper wire, with only the lead-in

the tuning capacitor. Now fasten the tuning capacitor

extending beyond the insulator. A lightning arrestor and

to the wood block near the coil assembly, and wire the

ground wire should also be used to avoid a direct hit by

coil in parallel with the tuning capacitor. Next locate a

lightning.

germanium diode; make sure you use only a germanium

diode and not the more common silicon diode.

A crystal radio will generally be able to detect radio

Remember to observe the correct polarity when

signals within 25 to 35 miles, during the day and often

connecting the diode in the circuit, the black to white

much further at night. A simple crystal radio is not very

colored band is the cathode lead. The cathode end of the

selective, if there are many local AM radio stations that

diode points to the headphone in the circuit diagram.

are close in frequency, then you may have some trouble

The anode side of the diode connects to one end of the

tuning them in, and you may have to build a more

“tank” or coil/capacitor and the cathode side of the

selective radio, such as the All-Wave model below.

diode connects to capacitor C2 and one end of the high

The crystal radio project above is a great project for

impedance headphones. The free end of the headphones

demonstrating the principles of AM radio and the fun

connects to the remaining end of the capacitor at C2

and excitement of building a crystal radio or

which connects to the free end of the “tank” circuit.

“free-power” radio.

You can connect the headphones via a terminal strip,

a Fahnestock clip or headphone jack mounted on the

wood block. Crystal radios generally require high

impedance headphones, so you must use either a small

crystal headphone or a pair of older high impedance

(2000) ohm headphones; these are still available

through EBAY or from Antique Electronics.

You could elect to build the radio using a galena

crystal, with a “cat’s whisker” instead of the germanium

Chapter Four: AM, FM, and Shortwave Crystal Radio Projects

Figure 4-4

Basic long-wire antenna

44

Chapter Four: AM, FM, and Shortwave Crystal Radio Projects

used to slope detect will hear static. The only real

FM radio crystal radio

advantage to slope detection is that is can be cheap and

convenient. When tuning in an FM signal with an AM

receiver, the clearest sound occurs when the FM center

Believe it or not, you can actually create a simple FM

frequency is offset from the center frequency of the

radio crystal radio. An FM crystal receiver is depicted in

receiver’s tuned circuits. If the FM signal is at the

Figure 4-5. The key to understanding how this simple

receiver’s center frequency, then frequency deviations

circuit can decode FM signals is to understand what

both up and down produce downward amplitude

happens when an FM signal is coupled to a tuned circuit.

changes. When the FM signal is off center frequency,

A good tuned circuit (one with a high “Q factor”)

up and down frequency changes create up and down

will attenuate signals that are not near its resonant

amplitude changes in the receiver.

frequency. If you apply an FM signal to a good tuned

circuit, as the frequency of the FM signal moves away

The FM crystal receiver circuit, shown in Figure 4-6,

from the resonant frequency of the tuned circuit,

looks almost identical to a classic AM crystal circuit;

the tuned circuit will attenuate that signal. As the

but look closely, there are a few major changes.

frequency of the FM signal moves toward the resonant

The FM crystal radio is relatively easy to build and

frequency of the tuned circuit, the tuned circuit will let

can be built on a small block of wood as shown. The

more of the signal pass through. Thus, a tuned circuit

components values for the “tank” or resonant circuit

will impose amplitude changes on an FM radio signal

were reduced to resonate at higher frequencies in the

that match the frequency changes. A crystal diode is

FM band. This was done by experimenting with smaller

sensitive to amplitude changes, so it converts the

and smaller coils and capacitors values. The antenna is

amplitude changes into a signal that the listener can

also much reduced in size (from that of AM crystal radio)

hear through headphones.

to resonate at higher frequencies. The antenna is actually

a 7′′ long bare copper wire. The coil at L1 is just four

Using a tuned circuit to induce amplitude changes

turns #18 copper or silver wire, 12 mm inside diameter,

onto an FM signal, then converting the amplitude

tapped at 2.5 turns, The coil was wrapped around a

changes to sound frequencies, is called slope detection.

“magic marker,” then slipped off and expanded. As you

“Slope” refers to the slope of the tuned circuits’

can see, this is far different than the 150 turn coil for the

attenuation curve. If you have an AM receiver you can

AM crystal radio. The detector diode, once again, is a

listen to an FM signal by using the slope of the tuned

1N34 germanium diode and not a silicon diode, or you

circuits in the receiver. This slope tuning method gives could use a galena crystal as a detector if you desire.

you none of the real advantages of FM. For instance,

Capacitor C3 is 18 pF, but is not critical and can be 10 to

FM is noted for its immunity to static. An AM receiver

50 pF. Resistor R1 is a 47k ohm, 1⁄4 watt, 5% carbon

composition type. The air variable capacitor, used in the

prototype, was an 80 pF variable type and it had two

trimmers in it which should be adjusted for best reception.

Figure 4-5

FM crystal radio

Figure 4-6

Simple FM crystal radio

45

Commonly available vernier dial and knob will fit the

tuning capacitor and will work nicely. When building

the FM crystal radio it is important to keep the

components physically close together and the wiring

short as possible. You can build the FM crystal radio in

an open style format on a wood or Lucite plastic sheet.

You can make your receiver a work of art, and impress

your friends with an FM crystal radio built from scratch.

Note that you will have to use high impedance

headphones for this receiver. A detected FM signal is

converted to AM due to an effect called slope detection

that modulates amplitude.

Figure 4-7

Shortwave crystal radio

This FM crystal radio works best near the transmitter,

reception seems fine up to 15 miles away. Secondly,

tune from below the AM broadcast band to around the

the sound level is not very loud; a quiet room is best

40 meter band, so you will be able to pickup

for listening. One must be willing to move the set

international shortwave reception quite well. You will be

around to find a location for the best reception of signals.

surprised how well it performs with a good pair of high

If desired, you could connect the audio output of the

impedance headphones.

FM set directly to an audio amplifier’s fed to a small

The key to this efficient receiver’s design lies with

speaker.

the two coils, L1 and L2, which are shown in the

schematic at Figure 4-8. Coil L2 is a multi-tapped

plug-in coil based on the band selected. For the AM

radio band, L2 is the 54 turn multi-tapped coil, with

Supersensitive

tapped from the ground end at 6T, 15T, 27T and at 40T.

AM/Shortwave crystal

The shortwave version of the L2 coil is a 15 turn

multi-tapped coil with tapped at 3T, 6T, 9T, and 12 turns.

radio

Depending upon the band chosen, you simply plug in

the AM or shortwave coil. The AM and shortwave coils

There are several characteristics that make the

(L2) were wound on a 3′′ cardboard tube, but you could

difference between a good and a great receiver. One of

use a plastic form instead. The untuned primary coil (L1)

these characteristics is sensitivity. Great receivers can

was wound a slightly smaller 2 7⁄8 form, so that it can be

pick up weak signals and amplify them into a useful

slipped inside of the L2 coil at the ground side of the

output. A second characteristic is selectivity. Great

coil assembly. The interchangeable coils (L2) were

receivers can separate signals so that only one is heard

mounted on a non-metallic carrier, a piece of phenolic

at a time. The third and final thing that separates good

board with five pin-plugs secured to the carrier board.

receivers from great receivers is fidelity. Great receivers

The coil form for L2 was glued to the phenolic carrier

not only pick up weak signals but can reproduce a

board which forms the plug-in coil assembly. The wire

signal without distortion. The last project in this chapter

tapes are brought out to the five pin-plugs on the carrier

is the All-Wave, AM/Shortwave crystal radio. This

board, so that the coil (L2) assembly can be plugged into

All-Wave design takes the crystal radio concept a little

sockets on the radio’s wood base plate, see Figure 4-9.

further and provides a more sensitive and more selective

This will allow either the AM coil or the shortwave coil

radio for you to build and enjoy.

to be plugged into the crystal receiver. You could elect

The All-Wave Crystal Radio is a supersensitive and

to build a fixed coil version of the crystal radio for

selective AM and shortwave receiver; see Figure 4-7.

either AM or shortwave reception if you desire, making

The design of the All-Wave radio has been around since

the receiver a bit easier to build.

the early 1930s and is still a very efficient receiver

The detector for the All-Wave Crystal Radio can be

Chapter Four: AM, FM, and Shortwave Crystal Radio Projects design that is fun to build and use. The receiver will either a 1N34 germanium diode or you could elect to

46

Chapter Four: AM, FM, and Shortwave Crystal Radio Projects

Figure 4-8

Sensitive/selective AM/shortwave crystal radio. Courtesy of Midnight Science Figure 4-9

Shortwave coil assembly

47

build the radio more like the “original” version by using

rod pounded into the ground. The All-Wave receiver

a galena crystal with a “cat’s whisker.” The galena crystal

will perform best with an 80 to 100 foot insulated

and “cat’s whisker” are still available, see Appendix.

long-wire antenna placed up-in-the-air outdoors

Be careful to install the diode or galena crystal with the

away from metal objects. An alternate antenna

proper orientation.

might be a 50 to 60 foot insulated wire strung around

The original All-Wave receiver used a 500 pF tuning

your attic, away from any metal objects. You will be

capacitor at C1, but you could also use a 365 pF type

amazed at how well this receiver will work with a

which are easier to locate from sources such as Antique

good antenna and a good pair of high impedance

Radio Supply. Mount the tuning capacitor to the wood

headphones.

block base using standoff and screws. The ceramic disk

In the event that your new All-Wave Crystal Radio

capacitor at C2 acts as an audio filter, ahead of the high

fails to work, you will have to re-check a few details.

impedance headphones.

First check the diode and how it was oriented in the

The All-Wave receiver needs to be used with either a

circuit, you may have placed it backward and this will

crystal earphone or a pair of dual high impedance (2K)

prevent the receiver from functioning. You will also

headphones such as the old Baldwin or Brandes

need to check the coil connections and placement of L1

headphones which are still available via EBAY or

with respect to coil L2. There is no polarity regarding

from Antique Radio Supply, see Appendix.

coil L1, but its placement at the ground end of L2 is

Switches S1 and S2 are used to select the taps between

important in order for the receiver to work properly.

the antenna and the detector. The two switches are

Also check the connections to L2, you may have

labeled Right and Left as shown in the diagram. The reversed two end wires of the coil, and this will prevent

same station may come in on several taps, but use the one

the radio from working as well. Try the receiver once

which places the station lowest on the turning capacitor

more, hopefully all of the connections are right now

setting for the loudest signals. Move the Right (S2)

and the receiver should work fine. Reconnect up your

forward or clock-wise, one to three taps before advancing

ground and antenna, put on your high impedance

the Left switch (S1). The efficiency of this radio seems to headphones and you’ll be ready to listen to your new

lie partly in the low loss coils, but mostly in the one basic

All-Wave receiver. You may want to have a “log” book

change in the circuit, in which the detector is connected

close to your new radio to log down the far away

permanently to the last turn of L2 towards ground.

stations you will receive with this radio. During

The All-Wave Crystal radio is just about completed

nighttime hours, you will be able to receive stations

and you now have only to connect a good antenna and

much further away, and when the shortwave coil is

ground for the receiver to spring-to-life! The All-Wave

plugged in you will hear international shortwave

Crystal Radio should be connected to a good ground

stations from all around the world on your new All-Wave

such as a cold water pipe or 6 to 8 foot copper ground

receiver. Have fun with your new All-Wave crystal radio.

Chapter Four: AM, FM, and Shortwave Crystal Radio Projects

48

Chapter 5

TRF AM Radio Receiver

C7

220 µF, 35 volt

Parts list

electrolytic capacitor

C8

2200 µF, 35 volt

TRF AM Radio Project

electrolytic capacitor

R1

120k ohm, 1/4 watt,

L1

220 µH coil; see text

5% resistor

(Ocean State-LA-540)

R2

2.7k ohm, 1/4 watt,

D1,D2,D3,D4,D5,D6

5% resistor

1N4148 silicon diodes

R3

10k ohm

Q1

BC108B–NTE123A

potentiometer (volume)

transistor

R4

10k ohm

Q2

BC109C–NTE123AP

potentiometer (trim)

transistor

R5

820 ohm, 1/4 watt,

Q3

BC179C–NTE234

5% resistor

transistor

R6,R9,R13

10k ohm,

U1

ZN414 or MK484 –

1/4 watt, 5% resistor

TRF Radio IC

R7,R8

22k ohm, 1/4 watt,

U2

LM741 Op-amp IC

5% resistor

S1

SPST power switch

R10

150k ohm, 1/4 watt,

B1

9-volt transistor

5% resistor

radio battery

R11,R12

4.7k ohm,

SPK

8-ohm speaker or

1/4 watt, 5% resistor

headphone

C1

10 nF, 35 volt

polyester capacitor

Misc

PC board, chassis,

battery holder,

C2

500 pF tuning

battery clip, wire,

capacitor (variable)

hardware

C3

100 nF, 35 volt

AM radio is the name given for the type of radio

polyester capacitor

broadcasting used in the medium wave band in all parts

C4,C5

2.2 µF, 35 volt

of the world and in the long wave band in certain areas,

electrolytic capacitor

notably Europe. Medium wave frequencies in the US

C6

33 µF, 35 volt

range from 540 to 1710 kHz with 10 kHz spacing.

electrolytic capacitor

The letters AM stand for amplitude modulation,

49

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the technique by which speech and music are impressed

radio services began on AM in the 1920s (the first

on the radio waves. The sound waves from the studio

licensed American radio station was started by Frank

are converted into electrical signals by the microphones,

Conrad: KDKA in Pittsburgh, Pennsylvania). Radio

and these electrical signals are used to vary the

programming boomed during the “Golden Age of

amplitude, or the distance from ‘peak’ to ‘trough’ of the

Radio” (1920s–1950s). Dramas, comedy and all other

main constant frequency carrier wave generated at the

forms of entertainment were produced, as well as

transmitting station. As a result, the signal radiated by

broadcasts of news and music.

the station varies in amplitude in step with the

The quality of reproduction on AM radio is not

variations in the loudness and pitch of the sound in the

as good as FM radio because of limitations in the

studio. In the receiver, the amplitude variations of the

amplitude modulation technique itself and because

radio signal are separated from the carrier wave by a

of overcrowding and subsequent interference in the

process known as demodulation, and after further

medium wave band. Interference is particularly serious

amplification are fed to the loudspeaker.

at night because the nature of the ionosphere alters after

Amplitude modulation is also used by international

sunset, so that it can then reflect medium wave signals

broadcasting stations operating in the shortwave band,

back to Earth a long way beyond their normal service

and for some professional communications such as air

area. Here, they interfere with other stations, producing

traffic control, ship-to-shore traffic, and some mobile

whistles and other unwanted noises.

radio services.

The AM method is still used for most popular

AM radio stations in the medium wave or AM radio

broadcasting. Although the alternative FM radio system

band can provide a service over an area the size of a

gives better quality, it is more difficult to receive, and is

town or of a whole continent, depending upon the

less suitable than AM for use in inexpensive transistor

power of the transmitter which can vary from less than

portables and car radios.

a hundred watts to hundreds of kilowatts. Long wave

The most important concept in any communications

AM radio stations cover even larger areas. Normally,

system is the ability to send information from one place

all radio waves travel only in straight lines, which would

to another via a transmitter to a receiver, see Figure 5-1.

limit a radio station to an area of only about 40 miles

This means you have to find a way to impress the audio

(65 km) in diameter—as far as the horizon. Medium

signal information on the radio wave in such a way that

and long wave stations can actually cover much larger

it can be recovered at the other end. This process is

areas because their signals are bent round the curvature

known as modulation. In order to modulate a radio

of the Earth by the ionosphere (an electrically charged

wave, you have to change either or both of the two

layer in the upper atmosphere which can reflect radio

basic characteristics of the wave: the amplitude or the

waves). In the US, where AM radio stations are

frequency.

operated on a commercial basis, coverage is generally

If you change the amplitude, or strength, of the signal

and deliberately limited to one city and its environs.

in a way corresponding to the information you are

Major cities such as New York are served by large

trying to send, you are using a modulation system

numbers of stations, each radiating a different program.

called amplitude modulation, or AM. The earliest means

AM radio stations in the US generally operate with

of radio communications was by Morse code, and the

omni-direction patterns during the day. In the evening

code key would turn the transmitter on and off. The

many AM broadcasters switch to directional antenna

amplitude went from nothing to full power whenever

beam patterns, and their broadcasts go much further due

the key was pressed, a basic form of AM.

to ionospheric bending. This is why you can hear AM

Modern AM transmitters vary the signal level

broadcast stations more distant in the evening.

smoothly in direct proportion to the sound they are

AM radio first began with the experimental broadcast

transmitting. Positive peaks of the sound produce

in 1906 by Reginald Fessenden, and was used for

maximum radio energy, and negative peaks of the

small-scale voice and music broadcasts up until World

sound produce minimum energy.

War I. The great increase in the use of AM radio came

The main disadvantage of AM is that most natural

Chapter Five: TRF AM Radio Receiver the following decade. The first licensed commercial and man made radio noise is AM in nature, and

50

Chapter Five: TRF AM Radio Receiver

Figure 5-1

AM broadcast system block diagram

AM receivers have no means of rejecting that noise.

do is to rectify the signal, through a rectifier which

Also, weak signals are (because of their lower

removes the bottom half of every cycle. Essentially you

amplitude) quieter than strong ones, which requires the

are throwing away the high-frequency or carrier part,

receiver to have circuits to compensate for the signal

but keeping the low-frequency or audio part. At the

level differences.

output of the detector the original audio information is

An AM radio station takes a low-frequency audio

sent to the speaker in your radio. You then “hear”

signal such as people talking or music (2500 Hz) and

whatever was broadcast at the radio station.

mixes it or superimposes on a high-frequency carrier

The AM radio project that we are going to build in

wave (540 kHz), see Figure 5-2. It sends this radio

this chapter is called a TRF or tuned radio frequency

signal out into the air as electromagnetic waves using a

type AM radio, see Figure 5-3. The TRF AM Radio

tall antenna. The electromagnetic wave travels through

design was at the forefront of radio design in the early

the air, going in all directions. At home, your AM radio

1920s. It utilized a tuned front end which allowed only

takes this incoming signal, in a process called detection.

RF energy of interest to be amplified by the RF

With amplitude modulation it is simple. All you need to

amplifier, the signal was then passed on to the detector

Figure 5-2

AM carrier and modulation signals

51

frequency is magnified by resonance so that it stands

out at a very much higher level of signal strength.

The original ZN414 IC, has now been replaced by the

MK484, which is considerably easier to locate. The

integrated circuit is a 3-pin, tuned radio frequency

circuit, and incorporates several RF stages, automatic

gain control and an AM detector. The receiver

front-end is easily overloaded and the operating voltage

of the IC is somewhat critical to achieve good results,

but all-in-all the receiver is a great little radio for AM

reception. The TRF radios were some of the first radios

on the scene when the dawn of radio appeared in the

early 1920s.

Figure 5-3

AM TRF receiver

The front-end of the TRF receiver as mentioned

consists of a tuned circuit composed of the ferrite

followed by an audio amplifier to drive headphones.

inductor, a tuning capacitor and the TRF radio chip.

Early TRF radios had up to three controls for tuning the

A small square plastic 0-200 pF tuning capacitor was

receiver, but later all three controls were consolidated

used for this radio project, but you could locate any

into “tuning” control. Our modern day TRF receiver

suitable tuning capacitor within the range and it will

shown in the block diagram in Figure 5-4 illustrates the

work equally well. Often these small tuning capacitors

three major components of the AM TRF receiver. The

will have additional on-board trimmer capacitors, but

first block consists of the tuned RF front-end resonant

we used only the main tuning capacitor in the center

coil/capacitor, the second block consists of the MK484

of the device.

IC, an integrated circuit RF amplifier and detector, and

The second critical component of the TRF receiver

finally the third block, which is an audio amplifier.

is the coil at L1, which is wound on a ferrite bar. First,

The TRF AM radio project was designed around the

let’s begin winding the coil at L1. The coil needs

popular MK484 TRF integrated circuit module, shown

approximately 65 turns of #28 gauge enameled Litz

in Figure 5-5. This receiver covers the medium wave

wire on a 21⁄2′′ long ferrite rod. The windings should

band or (AM) radio band from approximately 540 to

measure approximately 25 mm wide. Start winding the

1700 kHz. The TRF front end consists of two

coil, close to one end, by securing the enameled wire by

components, the ferrite aerial coil and the tuning

a piece of insulating tape. Leave approximately 100 mm

capacitor and the MK484 TRF IC. The important word

for connection. The quality of reception is dependent

is tuned, since this AM radio is called a TRF, or tuned

upon the care taken in winding the antenna coil.

RF radio All the AM signals reaching the radio are

The signal reception will vary, dependent upon

very weak. Only that signal which matches the TRF

location, and is better away from large buildings that

can distort the signal. Wind the wire tightly around the

ferrite rod, taking care to keep the coil together and not

to overlap the windings. To help hold the windings in

place a piece of double-sided tape can be placed on the

ferrite rod. Before soldering the antenna coil to the

circuit board, you will need to scrape off the enamel

coating from the ends of the wire. The two components

L1 and C2 are connected in parallel to form an LC

network. The Litz wire coil and the ferrite bar give the

LC network a high “Q” or quality factor. This is

important to the selectivity of the receiver, that is the

Chapter Five: TRF AM Radio Receiver Figure 5-4 TRF AM radio block diagram ability to tune into one radio station at a time.

52

Chapter Five: TRF AM Radio Receiver

Figure 5-5

TRF AM receiver broadcast band receiver

The coil winding and the ferrite bar act as an efficient

battery operation. The output is typically 40–60 mV of

wire antenna, as no additional antenna is required. The

audio signal. It is important to realize that the radio IC

only disadvantage is that the tuned circuit is directional

does not create any sounds by itself. It can only take the

and depends on the orientation of the bar with respect

RF signal provided from the TRF circuit, amplify it,

to the originating broadcast station. The coil winding

separate the audio signal from the RF (called detection)

and the ferrite bar act as an efficient wire antenna.

and pass the audio signal on to be amplified. It has no

No additional external antenna is needed. The only

selective or rejection components contained in it. (This

disadvantage is that the tuned circuit is directional.

is in contrast to superhetrodyne receivers.)

Signal strength depends on the orientation of the bar

In this circuit, a small voltage regulator is built

with respect to the origin of the signal. The coil and

around the BC108B transistor, four 1N4148 diodes, the

tuning capacitor may be taken from an old AM radio

2.7k and 10k preset resistor and the 820 ohm resistor.

to save time, if desired.

The 10k pot acts as a selectivity control for the whole

The third main component of the TRF radio front-end

receiver, controlling the operating voltage for the

is the TRF integrated circuit. The MK484 is a Japanese

ZN414 (or MK484). If you live in an area that is

copy of the original ZN414. It contains an RF amplifier,

permeated with strong radio signals, then the voltage

active detector and automatic gain control (AGC to

may need to be decreased. I found optimum

improve sensitivity) all in a 3-pin package. The input

performance with a supply of around 1.2 volts.

impedance is typically 4 M ohm. It operates over

The audio amplifier is built around an inverting

a range of 150 kHz to 3 MHz. DC supply of 1.1 V to

741 op-amp amplifying circuit. Extra current boost is

1.8 V and 0.3 mA current drain makes it ideal for

provided using the BC109C/BC179 complementary

53

transistor pair to drive an 8 ohm loudspeaker. The

or point-to-point wiring on a perf-board as an

voltage gain of the complete audio amplifier is around

alternative.

15. The audio output of the complete receiver is really

Refer to the chart in resistor color chart in Table 5-1

quite good and free from distortion. I used a small

and the capacitor code chart in Table 5-2. Resistors used

wooden enclosure and the complete tuning assembly

in this project will be mostly carbon composition type

from an old radio.

resistors and potentiometers. Each resistor will have

Before we begin the AM radio project, you will want

three or four color bands on the body of the resistor.

to locate a well lit and well ventilated work space. You

The first band closest to one edge will be the first color

will want a large work table or work bench to spread

which represents the first value. For example, a brown

out all you components, diagrams and tools. Locate a

color band will signify the first digit as a one (1). The

small pencil tipped 27 to 33 watt soldering iron and a

second color band represents the second digit value. So

roll of 60/40, 22 ga. tin/lead rosin core solder. If you

if the second color is red, then the value of the second

don’t have a jar of “Tip Tinner,” a soldering iron tip

digit would be two (2). The third color band is the

conditioner/dresser, then you will want to go to a local

multiplier value. So, if the third color is orange then the

Radio Shack store and purchase one. Place all the

multiplier value would be (000), so the resistor value

component parts in front of you along with the

would be 12,000 or 12k ohms. Often there is a fourth

necessary project diagrams, so it will be easy to work

color band which represents the tolerance value. No

with everything in front of you. Grab a few small tools,

fourth band denotes a resistor with a 20% tolerance, a

such as a pair of end-cutters, a pair of needle-nose

silver band denotes a 10% tolerance value, and a gold

pliers, a pair of tweezers, a magnifying glass, a small

band represents a 5% tolerance value. Now refer the

flat-blade, and small Phillips screwdriver. Once

capacitor code chart. Many small capacitors are too

everything is right in front of you we can begin

small to have their full value marked on the body of the

building the AM radio project. Warm up your

capacitor, so a three-digit code is used to represent the

soldering iron and we will begin. It is a good idea

value.

to use a circuit board for this project, since circuit

boards provide a more reliable method used to build

Let’s begin installing the project resistors now; find

circuits: you could elect to use prototype construction

and identify a couple of resistors at a time. Once you are

Table 5-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Five: TRF AM Radio Receiver

No color

20%

54

Chapter Five: TRF AM Radio Receiver

Table 5-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

820 pF

Ceramic

821

2

Mylar

205

55

sure you have correctly identified each resistor, and you

Install the electrolytic capacitors on the circuit board

know where each resistor is placed on the PC board,

and solder them in place; remember to trim the excess

you can go ahead and install them on the circuit board.

component lead with your end-cutter.

Solder the resistors in place and then trim the excess

Let’s move on to installing the silicon diodes. The

component leads with your end-cutters. Cut the excess

AM radio project uses six silicon diodes, and they too

component leads flush to the edge of the circuit board.

have polarity which must be observed. Each diode will

Install the remaining resistors, solder them in place and

have either a white or black band at one end of the

remember to trim the excess leads from the board.

diode’s body. This band denotes the cathode lead of

Next we will move on to installing the capacitors.

the particular diode. Refer to the parts layout and

This project uses two types of capacitors, small mica or

schematic diagram when installing the six resistors.

polyester types and electrolytic types. The smaller

Place the diodes on the circuit board and solder them

capacitors may not have their actual value printed on

in place on the board. Don’t forget to cut the extra lead

them, but might have a three-digit code on them.

lengths.

Refer to the capacitor code chart to help identify

Locate the semiconductor pin-out diagram shown in

each capacitor before installing them on the PC board.

Figure 5-6. Now, go ahead and identify all three of the

Slowly identify each capacitor and place it in the correct

transistors for the project and install the transistors on

location on the circuit board. Solder these small

the circuit board. There are two NPN types and one PNP

capacitors in their respective locations after referring to

type transistors in the AM radio project. Transistors

the schematic and parts layout diagrams. This project

usually have three leads, a Base lead, a Collector lead

also utilizes larger electrolytic capacitors. Electrolytic

and an Emitter lead. The symbol for a transistor is a

capacitors have polarity and this must be observed if the

vertical line which is the Base lead and two lines

circuit is to work correctly. Take a look at one of the

running at 45°angles with respect to the Base lead.

larger electrolytic capacitors and you will notice that it

The angled lead with the arrow pointing towards or

may have a black or white color band or a plus (+) or

away from the Base lead is the Emitter lead and the

minus (−) marking on one side of the capacitor body.

remaining lead is the Collector lead. Be sure you can

When placing these types of capacitors on the circuit

identify each of the transistor leads before placing them

board, be sure you have oriented the capacitor correctly.

on the circuit board. Solder the transistors in place on

1

8

ZN414

1

8

2

7

3

6

4

5

LM741

ZN414

EBC

EBC

EBC

1

2

3

OUT

IN

GND

MK484

C

C

C

B

B

B

MK484

E

E

E

NPN

NPN

PNP

1

2

3

OUT

IN

GND

BC108B

BC109C

BC179C

ZN414

MK484

Figure 5-6

Semiconductor pin-outs

Chapter Five: TRF AM Radio Receiver

56

Chapter Five: TRF AM Radio Receiver

the circuit board; when finished remember to trim the

the remaining free wire end to the minus end of

excess component leads.

capacitor C8.

The ZN414 or MK484 TRF module looks very much

This completes the construction of the AM radio

like a common three-lead transistor. Carefully refer to

project. Let’s take a well deserved rest and when we

the pin-out diagram for the MK484 before installing, in

return we will check the circuit board for possible “cold”

order to prevent damaging it upon power-up. One lead

solder joints and possible “short” circuits. Pick up the

is the input lead from the tuned circuit. One lead is the

circuit board with the foil side facing upwards toward

ground lead and the remaining lead is the output lead

you. Look closely at the circuit board, first we will

which is directed to the actual circuit.

inspect the circuit board for possible “cold” solder joints.

The AM radio project uses a single dual in-line

The solder joints should all look clean, shiny and bright.

integrated circuit, an LM471. We elected to use an IC

If any of the solder joints look dull, dark or “blobby”

socket as insurance against a possible circuit failure

then you should remove the solder from that joint and

at some point in time. Integrated circuit sockets are

re-solder the joint over again. Now pick up the circuit

inexpensive and make life easier in the event of a circuit

board once again and we will look for possible “short”

problem, since it is much easier to unplug an IC rather

circuits. “Short” circuits are usually caused from one of

than attempting to unsolder a multi-pin integrated

two reasons. The first cause of “short” circuits are loose

circuit. Go ahead and solder-in a good quality IC socket

solder “blobs” or solder balls which can sometimes

for U2. Take a look at U2 and you will notice that at

stick to the circuit board. The second cause for

one end of the plastic package you will find a cut-out,

“short” circuits is to have “stray” component leads

notch or indented circle. Pin 1 of the IC will be just to

stick to the foil side of the board. Rosin core solder

the left of the notch or cut-out. Be sure to align pin of

residue can often be sticky and often solder “blobs” or

the IC to pin 1 of the IC socket, pin 1 of U2 is the null

“stray” component leads can bridge across circuit

offset pin which is not used in this circuit. Note that pin

traces causing a “short” circuit. Look over the board

2 of U2 is the inverting input which is connected to the

and remove anything that looks like it might be

junction of R6 and R8.

bridging any circuit traces. Once the circuit inspection

Next locate the ferrite inductor coil or L1; you will

has occurred, you can prepare the circuit for its

notice that it is in parallel with the tuning capacitor C2.

first test.

The parallel tuned circuit is placed between capacitor

Connect up a fresh 9 volt battery to the AM radio

C1 and the input of U1, the MK484 TRF IC. These

circuit. Once the battery is connected to the circuit, you

components are best placed at one end of the PC board

can “flip” the on-off switch to the on position and you

if possible, or can be placed off the PC board on the

should begin to hear some “hiss” from the speaker. If

front of your enclosure. Now, locate the volume control,

you do not hear anything, turn up the volume control to

the 10k ohm potentiometer; it is a chassis mounted

mid-position. At this point you should begin to hear some

control which can be mounted on the front panel of

sounds from the speaker. Move the tuning capacitor

your enclosure.

control across the AM radio band and if all goes well

Let’s wrap up the project. First you will want to

you should begin to hear some local stations. Move the

solder the battery clip; note that the black wire of the

ferrite core coil or the circuit board around in a 360°

battery clip will go to the circuit board minus

pattern to see where the station is loudest. Hopefully the

or ground bus and the red battery clip wire will go in

radio works fine without any further adjustments.

series with one post on the on-off switch at S1, the

In the event that the AM radio circuit does not work

remaining post of the SPST toggle switch will connect

at all, you will have to remove the battery from the

to the Collector of Q1. Finally locate two 4′′ pieces

circuit and inspect the circuit board one more time, but

of #22 ga. insulated hookup wire. Bare both ends of

this time you will be looking for components placed

the two wires, solder one end of each wire to the

incorrectly. Remember earlier, we talked about certain

speaker leads. Now take one free wire end and solder it

components have polarity such as diodes, electrolytic

to the common ground of the circuit and then solder

capacitors, transistors, etc. Now, you will need to

57

inspect the PC board closely to see if you might have

specification and/or pin-out information sheets along

placed a component incorrectly. Its easy to make a

with the circuit layout and schematic diagram to confirm

mistake and insert a capacitor or diode incorrectly; it

transistor pin-outs. Once you have inspected the circuit

happens to professionals too! Another possible cause

board for misplaced components and have corrected any

for failure is that you may have placed an IC incorrectly

mistakes, you can reapply power to the AM radio circuit

in the socket! Finally, it’s easy to incorrectly install

and check out the circuit once again. Have fun listening

one of the transistors. Look at each transistor carefully,

to your new AM radio, you will have the great

you may want to refer to the manufacturer’s

satisfaction of listening to the radio that you just built.

Chapter Five: TRF AM Radio Receiver

58

Chapter 6

Solid-State FM Broadcast

Receiver

C2,C3,C7,C8,C16,C18,

Parts list

.01 µF, 35v disk

capacitor (marked .01

FM Radio Receiver

or 103 or 10 nF)

R1,R15

4.7k ohm, 1/4w,

C4,5,15,27

.001 µF,

5% resistor (yellow-

35v disk capacitor

violet-red)

(marked .001 or 102

R2,R18

1K resistor,

or 1 nF)

1/4w, 5% resistor

C6,C14

100 pF, 35v disk

(brown-black-red)

capacitor (marked 100,

R3,R16,R17

270 ohm,

101, or 101K)

1/4w, 5% resistor

C9,C17,C22,C26

4.7 or

(red-violet-brown)

10 µF, 35v

R4,R11

47k ohm, 1/

electrolytic capacitor

4w,

5% resistor (yellow-

C10,C13,C19

100 to 220

violet-orange)

µF, 35v electrolytic

R5,R7,R8,R9,R14

10K,

capacitor

1/4w, 5% resistors

C11,C12

22 pF, 35v disk

(brown-black-orange)

capacitor (marked 22)

R6

470 ohm, 1/4w, 5%

C20,C21,C23,C24,C28,C29

resistor (yellow-

.01 µF, 35v disk

violet-brown)

capacitor (marked .01

R10

2.2k ohm,

or 103 or 10 nF)

1/4w, 5% resistor

C25

.1 µF, 35v disk

(red-red-red)

capacitor (marked .1

R12,R13

10k ohm,

or 104)

potentiometers

FL1

10.7 MHz ceramic

R19

2 ohm, 1

filter; Digi-Key

/4w,

5% resistor

Electronics

(red-black-gold)

L1

slug tuned plastic

C1

4.7 or 5 pF,

molded coil

35v disk capacitor

L2

10.7 MHz shielded

(marked 5

can style IF

or 5K)

transformer (421F122)

59

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

D1

varactor diode,

33 pF

D2

Zener diode,

6.2 volt

U1

ULN2111 or MC1357 IC

U2

LM386 IC

U3

SA602 IC

Q1,Q3

2N3904 NPN

transistor

Q2

2SC2498 or 2SC2570A

NPN transistor

B1

9 volt transistor

Figure 6-1

FM receiver

radio battery

Misc

PC board, battery

holder, battery clip,

output which can be fed into an SCA converter to allow

RCA jacks

this reception of these signals.

1/′′

8

earphone jack, wire,

The receiver tunes from 70 to 110 MHz, ideal for

antenna

tuning in out-of-band FM wireless mikes, “bugs” and

The FM broadcast receiver will permit you to listen to

other “hidden” transmitters. The FM receiver also

your favorite radio shows as well as allow you to tune

features plenty of audio output, and operates from a

outside of the standard FM broadcast band to “listen-in”

standard 9 volt battery for truly portable operation.

to FM room bugs, FM mikes and other interesting

hidden transmitters. The FM receiver could also be

connected to an SCA adapter, so that you may listen to

‘MUSAK’ radio show used in stores and restaurants.

FM modulation

The FM radio project is just plain fun and will teach

you about FM radio theory.

Frequency modulation (FM) is a form of modulation

which represents information as variations in the

The FM broadcast receiver demonstrates the basics

instantaneous frequency of a carrier wave. Contrast this

of FM radio theory in one compact, simple circuit!

with amplitude modulation, in which the amplitude

Separate circuits are “sections” of the receiver, making it

of the carrier is varied while its frequency remains

easy to visualize every function. The latest in IC circuitry

constant. In analog applications, the carrier frequency is

is used in the FM receiver, which allows high performance.

varied in direct proportion to changes in the amplitude

The FM receiver project is designed to receive

of an input signal. Digital data can be represented by

wide-band FM transmissions typical of FM broadcast

shifting the carrier frequency among a set of discrete

stations, wireless mikes, and telephone transmitters or

values, a technique known as frequency-shift keying.

“bugs,” rather than Narrow Band FM transmissions

The diagram in Figure 6-2 illustrates the FM

(NBFM) as used on police or public service radios.

modulation scheme, the RF frequency is varied with

Why not build your own FM Broadcast receiver like

the sound input rather than the amplitude.

the one shown in Figure 6-1. Not only will you learn

FM is commonly used at VHF radio frequencies for

how FM receiver works but you will be able to build

high-fidelity broadcasts of music and speech, as in FM

and utilize your new FM radio. The FM receiver is

broadcasting. Normal (analog) TV sound is also broadcast

great for listening to FM broadcasts and news as well as

using FM. A narrowband form is used for voice

listening-in to commercial SCA—free music, stock

communications in commercial and amateur radio

Chapter Six: Solid-State FM Broadcast Receiver quotes, sports, etc. The receiver has an SCA or sub-carrier settings. The type of FM used in broadcast is generally

60

Chapter Six: Solid-State FM Broadcast Receiver

Carrier wave

Frequency drift typically constituted a problem on

generated at

very old or inexpensive receivers, while inadequate

transmitter

selectivity may plague any tuner. Frequency modulation

Frequency

is used on the FM broadcast band between 88 and

modulator

108 MHz as well as in the VHF and UHF bands for

Frequency modulated

both public service and amateur radio operators.

carrier wave – the

Electrical image

FM radio signal that

of sound formed

is transmitted

by microphone

Sound signal

to microphone

FM receiver circuit

Figure 6-2

FM modulation

description

The FM receiver block diagram in Figure 6-3 illustrates

the fundamentals of FM reception. The schematic

called wide-FM, or W-FM. In two-way radio, narrowband

diagram of the FM broadcast receiver is depicted in

narrow-fm (N-FM) is used to conserve bandwidth.

Figure 6-4. FM broadcast signals captured by the whip

In addition, it is used to send signals into space.

antenna or from the input jack are applied to the RF

Wideband FM (W-FM) requires a wider bandwidth

amplifier Q2, a high gain, low noise microwave style

than amplitude modulation by an equivalent modulating

transistor. Input signals are amplified about 100 times

signal, but this also makes the signal more robust

or equivalent to 20 dB. After being boosted, these input

against noise and interference. Frequency modulation

signals are routed to the SA602 mixer-oscillator chip

is also more robust against simple signal amplitude

for conversion down to the 10.7 MHz Intermediate

fading phenomena. As a result, FM was chosen as the

Frequency (IF). The SA602 is a very popular chip used

modulation standard for high frequency, high fidelity

in a great variety of receivers from cellular telephones

radio transmission: hence the term “FM radio.” FM

to satellite receivers. The reason for its popularity is that

broadcasting uses a well-known part of the VHF band

it contains most of a receiver’s “front end” circuitry on

between 88 and 108 MHz in the USA.

a single, easy-to-use chip. Internal to the SA602 is an

FM receivers inherently exhibit a phenomenon called

oscillator tuned by an external tank circuit; C11, 12, L1

capture, where the tuner is able to clearly receive the

and varactor diode D1. A varactor diode acts like a

stronger of two stations being broadcast on the same

voltage variable capacitor and the voltage applied across

frequency. Problematically, however, frequency drift or

it comes from tuning pot R12. This IF signal is an exact

lack of selectivity may cause one station or signal to be

reproduction of the desired signal, but at 10.7 MHz.

suddenly overtaken by another on an adjacent channel.

We then band-pass filter it with ceramic filter FL-1.

Figure 6-3

FM broadcast receiver block diagram

61

C h a p t e r S i x : S o l i d - S t a t e F M B r o a d c a s t R e c e i v e r 62

Figure 6-4

FM broadcast receiver. Courtesy of Ramsey Electronics

Chapter Six: Solid-State FM Broadcast Receiver

The ceramic filter allows only the desired 10.7 MHz

to locate a small jar of “Tip Tinner” from your local

signal to pass, rejecting any adjacent channel signals.

Radio Shack store. “Tip Tinner” is a soldering iron tip

Transistor Q1 amplifies the IF signal before it is applied

cleaner/dresser which is invaluable when soldering

to the detector chip U1.

circuit board. Locate the schematic and layout diagrams

One of the primary advantages of FM is that the

and we will begin to construct your new shortwave

program information (modulation) is contained in carrier

receiver. Place the project circuit board in front of you

frequency variations and not in amplitude changes

and we will begin building the receiver.

like AM, which would be susceptible to noise and

Locate all of the resistors for the project and place

interference. This means that we can limit or clip the

them in front of you. Each resistor has a color code

signal, thus removing any noise and not affecting the

which describes its value. Check the color code against

desired information. The first section of U1 performs

the parts list and schematic before installing them onto

this limiting function, providing high gain and clipping

the circuit board. Refer to the resistor color chart in

any amplitude (noise) variations. FM is detected in the

Table 6-1. Place about four or five resistors on the

second section using a process known as quadrature

PC board and place these resistors in their respective

detection. We’ll not get into this too deeply because it

locations carefully making sure each on is in the correct

requires a knowledge of trigonometry identities—let’s

location. Let your soldering iron tip heat both the

just say it extracts the frequency modulated program

component lead wire and PC board trace enough so

information. Capacitor C1 and coil assembly L2

that the wire itself and the foil trace both become hot

comprise a phase shift network that is required by the

enough together to melt a bit of solder so that it flows

quadrature detector. Demodulated signals are amplified

smoothly from the component leads to the PC board

and sent out through pin 1 to the volume control, AFC

trace. Now, go ahead and solder each of the resistors

circuitry and the SCA buffer amp. The AFC circuitry is

onto the circuit board. Trim off the excess component

used to properly keep the receiver locked on to the

leads with and small pair of end-cutters. Pick up and

tuned-in radio station. Resistor R9 and capacitor C17

identify the next grouping of resistors and install them

filter out any audio voltage variations so that only major

on the circuit board, follow up by soldering this next

frequency changes will shift the tuning voltage to lock

batch of resistors to the circuit board, remember to trim

the frequency.

the extra lead lengths form the PC board.

Audio signals from the volume control are amplified

Once all the resistors have been installed on to the

to speaker levels by U2, an LM-386 audio amplifier

circuit board, we can move on to identifying all of the

chip. Transistor Q3 provides a buffer stage to external

capacitors for the project. Note that there will be

SCA devices you may connect up to the receiver.

different looking capacitors for this project, some will

SCA units decode (demodulate, actually) “hidden”

be small disks, while others will be larger body devices

audio and data services transmitted over standard

with minus and plus marking on them. These larger

FM broadcast channels. These services include stock

capacitors with polarity marking are electrolytic

quotes, sports scores, talk shows and even background

capacitors and they have polarity which must be

music—commercial free!

observed for the circuit to work correctly. Look through

the parts pile and locate the capacitors and place them

in front of you. You will notice a number of small disk

capacitors, we will install these first. Look closely at

Circuit assembly

each of the disk capacitors at their markings. Sometimes

the capacitors are very small and they may not have

Look for a clean well lit area in which to assembly your

their actual value printed on them but will instead

shortwave receiver. You will need a 27 to 30 watt pencil

have some sort of code. Refer to the parts list for these

tip soldering iron, some 60/40 tin/lead rosin core solder.

codes or the capacitor code chart Table 6-2. Locate

You will also need a few hand tools including a pair of

four or five of these small disk capacitors, identify

end-cutters, needle-nose pliers, a few screwdrivers and

them and install them on the circuit board, while

a pair of tweezers to pick up small parts. You will want

referring to the schematic and layout diagrams.

63

Table 6-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

After inserting the disk capacitors on to the circuit

At this time, locate diodes D1, the varactor “tuning”

board, you can go ahead and solder them to the circuit

diode and D2, a Zener diode from the parts pile. Install

board. Remember to cut the excess component leads.

D1, varactor diode. It has a black body with green and

Next, move on and install another grouping of small

red bands. Observe the correct positioning of the banded

disk capacitors, then solder them in place on the printed

end by following the silkscreen. The green band is

circuit board. Cut the extra component leads after

positioned as shown on the silkscreen. Now, install D2,

soldering in the capacitors. When you are finished

the Zener diode. It has a gray painted glass body with

installing the small capacitors we will move on to the

a black band. Orient the band as shown on the layout

larger electrolytic types.

diagram. A Zener diode acts as a voltage regulator,

Next, we will identify and install the electrolytic

keeping the voltage across it constant. This keeps

capacitors. Electrolytic capacitors each have polarity

frequency drift to a minimum. Once both of the diodes

markings on them in the form of a black band with

have been placed on the PC board you can solder them

either a plus or minus marking, which denotes the

in place and then trim the extra lead lengths flush to the

polarity of the device. You must pay particular attention

edge of the circuit board.

to these markings in order for the FM receiver to work

Next, we are going to locate and install the two

properly. Refer to the schematic and parts layout

inductors; see Table 6-3. Locate the slug tuned plastic

diagrams when installing C9, C17, C22 and C26, which

molded coil, which is coil L1. Once you have located it,

are all 4.7 to 10 µF electrolytic capacitors. Install these

you can place it on the PC; remember to check the

four capacitors and solder them to the circuit board.

schematic and parts layout diagram for placement

Remember to trim the excess component leads. Cut the

details. Now, locate L2, the 10.7 MHz shielded metal

excess leads flush to the edge of the PC board with a

quadrature coil. Notice that it will only go into the PC

pair of small end-cutters. Now locate and install

board one way. Place L2 on the board and now solder

electrolytic capacitors C10, C13 and C19, these are all

both L1 and L2 to the PC board. Trim the excess

100 to 200 µF electrolytic types. After placing them on

component leads from the board.

the PC board in their proper location and with respect to

polarity marking you can go ahead and solder them to

At this time, you can locate FL1, the 10.7 MHz

Chapter Six: Solid-State FM Broadcast Receiver the PC board.

ceramic IF filter. This part looks like a disk capacitor

64

Chapter Six: Solid-State FM Broadcast Receiver

Table 6-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

820 pF

Ceramic

821

2

Mylar

205

65

Table 6-3

schematic for proper placement. Install Q2, 2SC2498

Inductor coil winding information

or 2SC2570A NPN transistor. Transistors are VERY

critical of correct orientation of their leads. Be sure to

L1

21⁄2 turn coil #22 ga. insulated magnet wire on slug

pay close attention to the position of the flat side of the

tuned coil form. Unwind original coil and rewind.

transistor. Finally, install Q3, 2N3904 transistor. Be sure

21⁄2 turns onto Series 48 adjustable coil form

to observe flat side orientation of the transistors when

48A Series Coil (48A117MPC) Circuit Specialists.

mounting them. Now go ahead and solder the transistors

L2

10.7 MHz shielded can style IF transformer (red)

in place on the PC board.

Part # (421F122) Mouser Electronics.

Let’s take a short break and when we return we will

install the integrated circuits and the final components.

Before installing the integrated circuits, please consider

but has three leads. Amazingly, its function is equal to a

using integrated circuit sockets as an insurance policy

small handful of inductors and capacitors hooked up in

against having to try and un-solder a 14 pin IC from

a bandpass filter configuration. For those techno-types,

the circuit board which is a difficult task even for the

its bandwidth is 280 kHz centered at 10.7 MHz with

seasoned electronics technician. Integrated circuits

an insertion loss of only 6 dB. Go ahead and solder FL1

DO fail and if one ever does, you can simply unplug

in now.

it and replace it with a new one. Refer to the schematic

Let’s locate the transistors for the receiver now! Next,

and parts layout diagrams when installing the

refer to the semiconductor pin-out diagram shown in

integrated circuits. Solder in the IC sockets in their

Figure 6-5. Transistors are three semiconductors which

respective locations and then we will install the

generally have three leads: Base lead, a Collector lead

actual ICs.

and an Emitter lead. The transistor symbol shows that

Integrated circuit packages will generally have a cut-

the Base lead is a vertical line. Both the Collector and

out, notch or indented circle at the top end of the IC

Emitter leads are diagonal lines which point to the Base

package. The cut-out or notch will usually be at the top

lead. The Emitter lead has a small arrow which points

center while if there is an indented circle it will be at

toward or away from the Base lead. Try and locate

the top left of the IC package. Pin 1 of the IC will

transistor Q1, a 2N3904 type. Watch placement of its

always be left of the cut-out or notch, so you can easily

flat side, refer to the parts layout diagram and the

identify the pin-outs. Using your schematic and parts

1

8

1

14

1

8

1

14

2

7

2

13

3

6

4

5

3

12

EBC

EBC

BEC

4

11

LM386

5

10

6

9

7

8

ULN2111

MC1357

1

8

1

8

C

C

C

2

7

3

6

B

B

B

4

5

SA602

E

E

E

NPN

NPN

NPN

Chapter Six: Solid-State FM Broadcast Receiver Figure 6-5 Semiconductor pin-outs 66

Chapter Six: Solid-State FM Broadcast Receiver

layout diagrams observe the correct orientation of

Before we apply power to the FM receiver for the

the integrated circuits before inserting them into the

first time we should make one last inspection of our

sockets. First locate and install U1, the ULN2111 FM

work. First you will want to make sure that you have

demodulator chip. Since this chip has 14 pins, be

installed the diodes, electrolytic capacitors and the

especially careful not to bend any pins under as you

transistors with the correct orientation. Failure to do so

insert it into the PC board. When you solder the chip,

may result in a damaged circuit, when power is first

verify that you are soldering all 14 pins. Next, let’s

applied. Don’t forget to check the orientation of the

install U2, the LM386 audio amplifier IC chip. The

integrated circuits for proper location and orientation.

LM386 is a very popular part, and with good reason.

Now we will inspect the PC board for “cold” solder

Tucked inside that little plastic case are about 20

joints. Pick up the PC board with the foil side facing

transistors that take a feeble audio signal and amplify it

upwards towards you. Take a look at all of the solder

up to room-filling volume! Finally, go ahead and install

connections and make sure that they all look clean,

U3, the SA602 IC mixer-oscillator. The marked end of

smooth and shiny. If you find a solder joint that looks

the IC (band or dot) must face the edge of the PC board.

dirty, dark, dull or “blobby” then un-solder the connection,

If you wish, install an 8-pin DIP socket, still remembering

remove the solder and re-solder the connection once again

to orient and install the SA602 correctly. Remember to

until it looks good. Finally, we are going to inspect the

firmly press the integrated circuits into their sockets.

PC board for possible “short” circuits. Often “cut”

The receiver project has two potentiometers, R12 is

components leads can form “bridges” which can “short”

the “tuning” control, while R13 is the volume control.

out the circuit board traces, thus causing power to flow

Locate the two 10k ohm potentiometers and install them,

into the wrong places, and possibly damage the circuit.

being sure to refer to the schematic and parts layout

Also look carefully for any solder blobs that can form

diagrams. Note that both potentiometers are on the front

“bridges” between circuit traces. Now that you have

panel of the PC board. Install potentiometer R12, the

inspected the PC circuit board, we can move on to testing

tuning control. Insert it into the PC board so it seats

and aligning your new receiver.

firmly and is straight and even. Solder the three pins

and the two mounting tabs. Next, install potentiometer

R13, the volume control in the same manner.

Testing and alignment

Now locate S1, the on-off push button switch. Solder

all six pins firmly. We’ve installed some “landmark”

A hex head alignment tool is required to tune up

parts so far just to get us used to soldering our PC

your FM receiver. If you do not already have a set of

board. Finally, we are going to place the panel jacks on

plastic or nylon coil alignment tools and expect to

the rear portion of the circuit board. Locate and install

build other radio or transmitter type kits, such tools are

J1, the RCA antenna jack, solder all four points. Now

well worth having and can be found at any electronics

locate and install J2, the speaker jack, solder all three

store, including Radio Shack. While a hex style

pins. At last, install J3, the SCA output jack, solder all

Allen wrench will fit the coil slug, the metal itself

four points.

will drastically change the coil’s inductance while it is

There are only a few more components to go before

in the slug. For this reason you should not use an Allen

we finish our FM receiver project. Install the 9 volt

wrench unless you don’t mind the trial and error process

battery clamp. Use a scrap component lead wire looped

of turning the slug, withdrawing the tool, checking

through the holes in the clamp and into the holes in the

tuning, reinserting the tool, re-tuning, checking

PC board. Solder the wire to the clamp but don’t use too

and so on.

much solder as this will prevent you from seating the

You can fabricate your own non-metallic tuning tool

battery fully into the clamp. Now, go ahead and install

with some patience, a bit of sandpaper and a piece of

the 9 volt battery snap connector. Make sure you put the

plastic rod. Try a large wooden matchstick, kebab

right color wire into the proper hole on the PC board.

skewer, or small plastic crochet needle. Carefully sand

At long last, you are all done and ready to listen to

down the end to a hex shaped form and check for

tunes from your radio.

proper fit within the coil slug. It is better to have the

67

tool fit loosely rather than too tight, since a tight tool

Make sure the slug is about three turns from the top of

will cause stress on the delicate slug.

the coil form.

Connect up a fresh 9 volt battery (preferably heavy

Calibrating the receiver is easy. First tune in a station

duty alkaline type), a speaker or earphone, a short

known to operate at the low end (88 MHz) of the FM

length of wire (about two feet) to serve as antenna, or

broadcast band. Rotate the tune control almost fully

the telescopic whip if the optional matching case and

counter-clockwise to where that station should logically

knob set was purchased. Now, set the volume and the

be located on the dial. Turn L1’s slug until that same

tuning controls to the center of their range, then press

station is received. The tune control should now tune in

the power switch “ON,” you should hear some rushing

the entire FM broadcast band. An easy way of making

noise from your speaker. Next, rotate the volume

your own dial is to paste a small rectangle of paper

control and see if it does its job, then slowly turn L2’s

behind the tuning dial knob. Then as you tune in

slug back and forth for maximum noise. This noise

different frequencies, pencil in on the paper the received

should be similar to what you would hear when a

frequency.

regular FM radio is tuned between stations. L2 may

be tuned with a regular blade style screwdriver.

Try turning the tuning control, and see if you can

Additional receiver

receive any stations, but don’t be alarmed if nothing is

received since we haven’t adjusted the oscillator coil

considerations

yet. The oscillator coil, L1, is adjustable to receive

from 70 to 110 MHz. We have to adjust it to cover the

Your FM receiver was designed for clean, undistorted

frequency range of interest. For alignment purposes

audio from average FM broadcast stations, while

we’ll work with the understanding that the standard

keeping battery current drain low. You may significantly

FM 88-108 MHz band is what we wish to receive.

increase the FM radio’s audio output by adding a single

Using an insulated alignment tool, slowly rotate L1’s

10 uF electrolytic capacitor across pins 1 and 8 on the

slug gently so that the slug is even with the top of the

LM-386 audio amplifier IC. The “+” side should

coil form. (Do not force the slug; if it binds, rotate the

connect to pin 1. An easy way of adding this capacitor

slug back and gently “rock it” to-and-fro as you would a

is to simply “tack” solder it right on the IC pins on the

thread forming tap. Slugs are by nature very brittle and

solder side of the PC board. A 50-cent of speaker, lying

will crack easily.) Now carefully rotate the slug into the

naked on your workbench, will not give you a fair test

coil form seven turns. The slug will be in about 1⁄

of your FM receiver audio quality or volume. Speaker

4′′.

Rotate the tune control until you hear an FM broadcast

quality and well-designed enclosures have their clear

signal. Adjust L2 for best sound. Install R9, 10k ohm

purposes! A reasonable speaker in a box delivers a

(brown, black, orange). R9 adds in AFC voltage to

pleasant listening volume as well as significantly

stabilize against drift. Without it your radio may

improved fidelity.

“wander.” After a signal is received, rotate the tune

control to receive other stations. If the stations seem to

“jump away” as you try to tune one in, the coil L1 is

adjusted incorrectly and should be re-tuned. The reason

Out-of-band operation

for this odd phenomenon is that the AFC circuit is

pushing the signal away rather than pulling it in. This

Although many people use their receiver for

is caused by having the oscillator 10.7 MHz below the

comfortable FM broadcast reception, some James Bond

desired signal rather than 10.7 MHz above it. A similar

types will want to use it to receive clandestine

example of this is closing your eyes, hearing a sound,

transmissions from phone bugs, room transmitters, etc.

but not being able to determine if it is in front of, or

It’s a simple matter to re-tune coil L1 to receive the

behind you. Readjusting L1 will correct this situation.

frequency band of interest. First make sure you verify

Chapter Six: Solid-State FM Broadcast Receiver

68

Chapter Six: Solid-State FM Broadcast Receiver

that your receiver receives the FM broadcast band

forms of data. Some of the information carried on these

correctly before re-tuning.

sub-carrier data services include stock quotes, weather

reports, news, sports and even paging signals. There is

no limit to the variety of data that can be sent on a sub-

SCA output

carrier signal, and broadcasters are finding new things

to send all the time!

Many FM broadcast stations now transmit sub-carriers

The SCA output is a baseband demodulated

on their signals. Sub-carriers are signals that are

sub-carrier signal output before any low pass filtering

modulated on the carrier, just like the normal audio

or de-emphasis. It provides a handy connection point

signals, except that they are too high in frequency to be

for add-on SCA adapters such as the Ramsey SCA-1

heard. Normal audio signals range in frequency from

kit. You can also connect this output to a receiver

20 to 20,000 hertz. Most sub-carriers start at 56,000 hertz

capable of receiving 30 to 75 kHz FM signals, or a PLL

(56 kHz). These sub-carriers are themselves modulated,

demodulator you’ve built yourself. Check out the data

sometimes with audio signals, such as background

sheet from Signetics concerning the NE-565 PLL chip;

music, but more and more these days with various

an SCA demodulator is featured.

69

Chapter 7

Doerle Single Tube

Super-Regenerative

Radio Receiver

L2

“tickler” coil (see

Parts list

text)

L3

main tuning coil

Doerle Receiver –

(see text)

Original #19 Dual

T1

#19 triode tube –

Triode

2.5 volt filaments

R1

2.2 megohm 1⁄w, 10%

2

B1

Type A filament

resistor

batteries (6 volts)

R2

330k ohm 1⁄w, 10%

2

B2

Type B battery 90

resistor

volt battery pack

R3

47k ohm, 1⁄w, 10%

2

HP

200 ohm high

resistor

impedance headphones

R4

100k ohm,

Misc

chassis, tuning

potentiometer panel

dial, wire, sockets,

mount

standoffs, screws, etc.

R5

25 ohm reostat

Doerle Receiver – 6SN7

C1

5–18 pF antenna

Version

trimmer capacitor

R1

2.2 megohm 1⁄w, 10%

2

C2

140 pF main tuning

resistor

capacitor

R2

1000 ohm, 1⁄w, 10%

2

C3

.001 mF, 200 volt

resistor

disk capacitor

R3

470k ohm

C4

100 pF, 200 volt

potentiometer panel

disk capacitor

mount

C5

.1 mF, 200 volt disk

R4

100k ohm, 1⁄w 10%

2

capacitor

resistor

C6

.005 mF, 200 volt

R5

100k ohm

disk capacitor

potentiometer

L1

2.5 mH choke coil -

C1

8–18 pF trimmer

Digi-Key Electronics

capacitor

70

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Seven: Super-Regenerative Radio Receiver

C2

100 pF main tuning

capacitor

C3

50 pF variable tuning

control (fine tune)

C4,C5

470 pF, 200 volt

disk capacitor

C6

100 pF, 200 volt

disk capacitor

C7

.01 mF, 200 volt

disk capacitor

C8

.22 mF, 200 volt

capacitor

Figure 7-1

Doerle receiver

L1

2.5 mH choke coil

Digi-Key Electronics

In this chapter we will build a copy of the original

L2

“tickler” coil

Doerle radio and we will also show you how to build the

(see text)

Doerle radio receiver using a more modern tube such as

the 6SL7, which may be a lot easier to locate these days.

L3

main tuning coil

If you are a “purist” you may want to try and locate the

(see text)

original #19 triode tube, which is still actually available.

T1

6SN7 triode tube

You can build either version, which you can construct to

B1

type A battery -

look just like the original radio looked back in the 1930s.

6.3 volt power supply

This radio is a study in simplicity, the low parts count

or batteries

kept the original cost down. A single sheet of metal,

B2

type B battery - 150

probably steel, painted in black wrinkle finish became a

volt power supply or

chassis. The single #19 tube powered by batteries

batteries

eliminated unnecessary tubes and power supplies. The

result is a simple, high-performance shortwave radio

HP

200 ohm high

that beginners could afford to build and operate during

impedance headphones

the depths of the Great Depression.

Misc

chassis, tuning

First let’s examine the circuit diagram, shown in

dial, wire, standoffs,

Figure 7-3 for the original Doerle radio. The antenna is

screws, etc.

Old Time Radio lovers will enjoy building this single tube

regenerative AM/Shortwave receiver called the Doerle

Radio, shown in Figures 7-1 and 7-2. It is a classic radio

from around 1934, which was offered as a radio kit that a

radio enthusiast could build at home. This very sensitive

receiver is a fun-to-build radio which can be powered

from batteries as they did in the “old days” or you could

construct an AC power supply for it. The original Doerle

radio receiver was offered as a kit for $3.00. The early

Doerle receiver used a #19 dual triode receiving tube, one

section of the tube acted as a regenerative detector and the

second section of the tube acted as an audio amplifier.

Doerle perfected this receiver design in 1933 when the

new #19 tube became readily available.

Figure 7-2

Doerle receiver – inside view

71

Figure 7-3

Original #19 dual triode receiver

coupled through a small 15 pfd screwdriver adjusted

ground. Plate current in the detector flows through

variable capacitor to the main tuning coil wound on a

these two resistors. Variations in current creates a

four pin form. A 10 pfd variable capacitor across it

varying voltage drop across this pair. The varying

gives a fairly good trade-off between slow tuning rate

voltage is the audio signal that is applied to grid of the

and wide tuning range. The signal is fed through a grid

audio triode.

leak configuration to one of the grids of the #19 tube.

The B+ voltage source is fed through headphones to

From the plate, the signal goes to the tickler wound on

the second plate to complete the audio amplifier part of

the same four pin coil form. The top side of the tickler

the circuit. The sound that is heard in the headphones

coil connects to a 500 pfd capacitor and a 2.1 mH radio

comes from the variations in the audio plate current.

frequency choke (RF). The choke allows DC plate

A .006 mfd capacitor on the plate is large enough to

voltage into the tickler but prevents the radio frequency

take any stray RF to ground, but is not so large to take

(RF) alternating current from getting into the rest of the

audio frequency (AF) voltage to ground. This capacitor

circuit. The 500 pfd capacitor takes the RF to ground,

aids receiver stability and audio quality.

thereby allowing RF voltage to build up on the tickler

A 20 ohm rheostat in series with one of the filament

winding. Without this 500 pfd capacitor the receiver

legs allows adjustment of the voltage. A rheostat is a

would probably not regenerate properly.

low resistance, high wattage potentiometer. In the 1930s,

Variations in the DC voltage delivered to the detector

you would have used two No. 6 1.5 volt dry cells (they

plate feed through a .1 mfd capacitor to the second grid.

were about 6′′ tall and 2 3⁄4′′ diameter) as your filament

A 250K, 1⁄2 watt resistor pulls the grid to DC ground, to

power supply. The rheostat would cut the voltage down

provide the necessary zero bias for this class B amplifier

to two volts needed by the tube’s filament. As the

tube, yet the resistance is high enough so that the AC

voltage provided by the batteries dropped with use, you

avoids the ground and readily flows into the second grid.

would adjust the rheostat to maintain the proper voltage

Voltage on the detector plate is changed by a 50K

on the filament. In other words, the rheostat allowed

resistor attached to the wiper of a 50K regeneration

you to continue using the filament batteries as their

Chapter Seven: Super-Regenerative Radio Receiver potentiometer that is connected from the B+ battery to voltage dropped to the point of total failure. Since the

72

Chapter Seven: Super-Regenerative Radio Receiver

filament current for a #19 triode tube is just over 250

get something close. You’ll have to mix and match

mA, so a 20 ohm resistor would allow you to use

whatever you can find. Most of these components are

filament batteries up to 6 volts. And quite frequently

available at flea markets if you visit enough of them.

that 6 volts was the battery borrowed from the family

Many of the components are available new from

car.

dealers, such as Antique Radio Supply, see Appendix.

But often you’ll have to pay substantially higher yet fair

prices. The used #19 tube was purchased from a flea

market dealer for $5. Yet, that same tube can be

Building the original

obtained brand new from Antique Electronic Supply for

Doerle receiver

about $6, see Appendix. Again, you may have to

scrounge, make do, adapt, experiment, and make a few

mistakes. But the results are well worth it.

The first step in building this or any project is getting

the parts. In fact, this may be the most difficult step.

One idea is to build a prototype receiver with

When it comes to building a replica of an old radio like

whatever components you can find, no matter how new

this, you just cannot go out and buy everything you

or old, and get it working. Then, over the next few

need. You may have to adapt and use whatever you have

years, visit flea markets, antique radio meets, check out

on hand or can scavenge. For a project of this type you

dealers’ catalogs, and accumulate the older, more

may want to build the circuit using point-to-point wiring

authentic parts. After you accumulate some of those

between terminal and components rather than a circuit

rare, old, beautiful parts from the 20% and 30%, rebuild

board to give the radio an “old-time” look. You are

the receiver. And then a few years later rebuild it again.

probably going to need both a soldering iron and a

And every time you rebuild it, add older and more

soldering gun to build this radio. You will also want to

authentic parts, until you get an exact copy of the

consult with the resistor color code chart in Table 7-1

#19 Doerle receiver. The radio will become more and

and the capacitor code chart in Table 7-2 in order to

more of an authentic replica of a receiver from the early

identify the correct components.

days of radio. With patience, practice, and plenty of

enjoyment, you can build a fine radio.

Building this old radio can be lots of fun, but locating

all of these old components can be difficult, and in fact

Looking at the illustration of the Doerle-1 version,

you won’t be able to locate the exact same items. You’ll

we see in the center a large, slow-motion dial drive

Table 7-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

73

Table 7-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Seven: Super-Regenerative Radio Receiver 820pF

Ceramic

821

2

Mylar

205

74

Chapter Seven: Super-Regenerative Radio Receiver

Table 7-3

Short-wave band listening frequencies

Shortwave Band

Shortwave Band

120 meters = 2300–2495 kHz

25 meters = 11.500–12.160 MHz

90 meters = 3200–3400 kHz

22 meters = 13.570–13.870 MHz

75 meters = 3900–4000 kHz

19 meters = 15.030–15.800 MHz

60 meters = 4750–5060 kHz

17 meters = 17.480–17.900 MHz

49 meters = 5730–6295 kHz

16 meters = 18.900–19.020 MHz

41 meters = 6890–6990 kHz

13 meters = 21.450–21.750 MHz

41 meters = 7100–7600 kHz

11 meters = 25.670–26.100 MHz

31 meters = 9250–9990 kHz

friction-driven by a small knob at the bottom of the set.

Since a solid, rigid mount for the tuning capacitor is

This allows fine tuning of stations. To the upper left are

essential if you are to achieve frequency stability and

the antenna and ground terminals. Just to the right in a

eliminate microphonics, you must get this part of the

hole in the front panel is exposed the screw which

assembly correct. And since your components will need

adjusts the antenna coupling capacitor. Below left is the

their own custom mounting hardware, you’ll need to

filament rheostat knob. At the upper right are the

experiment until you get it right. That’s why the

headphone terminals with the regeneration control

breadboard prototype is so useful. Take your time.

located at the lower right. Although the receiver as

In continuing the capacitor assembly, I used a pair of 1⁄2′′

shown in the original drawings may appear complex, it

long 6-32 machine screws in the top and bottom pair of

really is not. This is one of simplest receivers that you

holes on the drive mechanism. In the left-right pair of

could build.

holes, I used a pair of 11⁄2′′ long 6-32 machine screws.

The original chassis for the Doerle receiver was an

The extra length became mounting studs to which an

L-shaped piece of sheet metal, most likely steel, and

aluminum cross-arm was attached. In the cross-arm was

painted with a black wrinkle finish. While the front

drilled a 3⁄8′′ hole to accommodate the mounting flange

panel was perfectly rectangular, the base was

of the capacitor.

trapezoidal. Dimples were embossed into the base plate

After the capacitor holes were drilled, the burrs

which served as feet.

removed, and edges of the panel were rounded and

For our replica Doerle receiver, you can start with an

smoothed, I roughed up the surface with fine sandpaper.

11′′ × 9′′ sheet of .063′′ (1⁄16′′) aluminum to construct the

chassis. The most complicated mechanical problems

that you may encounter in building the receiver is the

mounting #19 dual triode tube up on standoffs,

mounting the variable capacitors and building the coils

on the coil-form, see Figure 7-4.

The original Doerle model used a simple single

bearing variable capacitor. We elected to use a heavy

duty Hammarlund tuning capacitor; it is of significantly

higher quality and is much heavier, so you will have to

support the rear end of the capacitor with a bracket of

some type. Once a Z-bracket as fabricated and attached

to the breadboard, the prototype dial-drive-capacitor

assembly was solid, yet turned smoothly.

Figure 7-4

Doerle coil assembly

75

Next, the panel was bent into an L shape. You can use

than if you get in a hurry and paint the whole thing at

an old sheet metal brake, or you can could do the same

once, but the results will be more predictable. You can

by clamping the metal between a couple of 1 by 2’s or

bake it in an electric kitchen oven at the lowest possible

lengths of angle iron held tightly together in a vise or

heat. Nasty smelling solvents are baked out of the paint,

with C-clamps. Since only a single, simple bend is

so your wife or mother may not be too happy with you!

required, you might get by clamping the sheet metal to

After mounting the tuning capacitor, the only other

a table top and by bending the sheet over the edge.

assembly of any complexity is the coil socket and

In order to obtain smooth tuning with a large range,

antenna trimmer mount. Mounting the other

you should locate some sort of planetary drive

components was fairly easily done. You can use

mechanism in front of the main tuning capacitor, such

machine screws, spacers of wood, plastic, porcelain, and

as a used National Velvet Vernier dial drive, which can

metal. You can slice wood spacers from hardwood

be removed from an old radio. The first step was to

planks, but you’ll need a table saw to do a good job.

dismantle it into the drive mechanism, the knob, and the

Plastic spacers can be cut from plastic tubing, but just

dial plate. To mount the actual planetary drive

be sure to get the rigid stuff used by plumbers for water

mechanism, I had to cut a 5⁄8′′ hole in the plate with a

supply lines. Porcelain spacers are something, which

socket punch. Next, the drive collar was slipped through

can be scavenged at a local hamfest or radio flea market.

the 5⁄8′′ hole. With a marker I marked the location of the

A small trimmer capacitor is mounted on porcelain

four mounting holes.

standoffs in order to insulate both terminals from the

In moving the capacitor and dial drive to the finished

chassis. Between the standoffs is a drilled 3⁄8′′ hole in the

receiver, I chose to position the angle mounting bracket

front panel to allow screwdriver adjustment. That

vertically as shown in the photos. This made fabrication

sounds simple enough. But behind the trimmer is the

and installation of a new base bracket much easier, and

socket that accepts the four-pin lube socket coil form.

allowed more clearance for the tube and coil socket as

What I used here were a couple of 2′′ 6-32 machine

well as for the terminal strip below the dial drive.

screws cut to the appropriate length with heavy clippers.

When the components are “test” mounted, you can

They were then fed through the coil socket mounting

move from the prototype stage to the finished L-shaped

holes and through brake line spacers into the porcelain

panel, if you are happy with the final layout. Then you

standoffs. Two soldering lugs were sandwiched

can spray on a thick coat of fast drying metal primer.

between each metal spacer and porcelain standoff.

Once dry, I wet-sanded it under a stream of water until

One lug on each side was soldered to a capacitor lead.

smooth. Then came the black wrinkle paint. If you wish

The other lug on each side became connector for

to try and duplicate the original, you will want to try

the trimmer. Since the metal spacer pressed tightly

and create the wrinkle finish. If you are not that

against the capacitor lead, it was imperative that the

concerned about having the radio look exactly like the

four pin socket be made of insulating material. Here

original radio, you can just paint the chassis with a

I used an old phenolic wafer socket. A metal socket

single coat of black paint. Black Krylon paint is

would short out the capacitor. It sounds complicated but

available in a spray can in your local home

it should be fairly easily understood by studying the

improvement store. For best results in creating a wrinkle

photographs.

finish, you must put down a heavy layer of paint. It

Wiring was done with some modern plastic covered

must be heavy so that it can wrinkle up as it dries. If the

hookup wire, and with some genuinely old cloth-covered

coat is too light, or if you try to apply a second light

hookup wire salvaged from a piece of old tube gear.

coat over the existing layer, you won’t get the best

Watch for old tube gear with long lengths of cloth-covered

results. It might even be shiny where it is supposed to

wiring at flea markets. New old stock cloth covered wire

be flat black.

is around but it is not always easy to find. Sometimes you

It is recommended that you paint one surface at a

can look for old wire while scavenging at hamfests.

time and let it dry. Then reposition the chassis so that

The coils used in the original circuit were 11⁄2′′ dia. by

another surface is horizontal and then paint that. Of

3′′ tall phenolic coil forms. You can use phenolic bases

Chapter Seven: Super-Regenerative Radio Receiver course, it will take four times as long to paint the radio from four prong tubes for the coil forms and they can be

76

Chapter Seven: Super-Regenerative Radio Receiver

purchased from Antique Electronic Supply. The low

The original ten turns of tickler turned out to be too

frequency or main “short-wave” coil is close-wound

many, so you may have to improvise to get it right.

with about 30 turns of #26 wire. You wind the “tickler”

You’ll discover this problem very quickly if, when you

coil, which is 9 or10 turns of #24 ga. wire below the

advance the regeneration control, the receiver goes into

tuning coil, and both coils were covered with clear

a deafening howl. You may need to remove one turn of

fingernail polish. The coil covers approximately 2.5 to

tickler coil at a time until regeneration starts up

4.5 MHz. The exact number of turns you’ll need is

smoothly near the end of the control clockwise rotation.

going to depend on the tuning capacitor you use and the

You should adjust the tickler with the tuning capacitor

stray capacitance that results from your particular

open, that is, at the receiver’s highest frequency. Here,

component layout, among other things. You’ll have to

more regeneration is necessary than at lower

experiment to get the right number of turns.

frequencies. And you must adjust the antenna trimmer

The original Dorele receiver had plug-in coils for

control for the minimum capacity that gives excellent

different radio bands. In order to construct an AM radio

sensitivity. Adjusting the antenna trimmer “couples” or

coil, you will have to wind another main coil along with

“de-couples” the connection between the receiver and

another “tickler” coil on a second coil form. The main

the antenna, and can have a pronounced effect on

coil will need about 40 turns of #26 ga. wire, with a

regeneration adjustment and overall sensitivity.

9–10 turn “tickler” winding.

The #19 tube filaments can be powered by alkaline

Battery terminals can also be purchased at a radio flea

flashlight batteries. Alkaline batteries should be used

market. Using a table saw you could elect to slice a 1⁄4′′

rather than cheaper zinc-carbon types since alkaline can

strip from an oak 1×6. That gave me a mounting strip of

deliver higher currents, and because they’ll last much

3⁄4′′ × 5 1⁄2′′ × 1⁄41′′ thick, just right for this radio.

longer. Alkaline batteries will give many more hours of

use for your money. You can hook the filament batteries

up to the set with the rheostat set to maximum

resistance. You can then rotate the rheostat, with a

Firing up your original

voltmeter connected to the filament leads, in order to

Doerle receiver

allow the meter to show two volts. Then put a reference

dot on the panel with a marker pen. You can do

Now your #19 Doerle radio receiver is bolted together

something similar to the finished machine. As the

and wired up. It’s time to try it out. First, check the

batteries age, their voltage will drop making it

wiring, then check it again. It’s easy to make stupid

necessary to adjust the control to maintain the two volts

wiring errors, sometimes after checking the wiring once

on the filaments.

or twice! Have a friend look over the circuit before

If you do not want to use flashlight batteries, you

applying power to the circuit for the first time. The coils

may consider nickel-cadmium batteries. They’re

used in the original drawing look like 11⁄2′′ dia. by 3′′ tall

inexpensive, each cell delivers about 1.2 volts, so you

coil forms. You can use phenolic bases from four prong

will need two, three or even four in series, which will

tubes. They’re not from old tubes but from Antique

deliver as much as 4.8 volts. And when they run down,

Electronic Supply.

you can recharge them. But before you go to that

The low frequency coil is close-wound with

trouble: try flashlight batteries. You may be surprised by

about 30 turns of #26 wire. You can wind about 10 turns

how long they last. As for a 90 volt B+ battery, you will

of tickler below the tuning coil, and cover both coils

most likely not be able to find them and if you do they

with clear fingernail polish. The coil covers

will be expensive. Newark Electronics still had them,

approximately 2.5 to 4.5 MHz. The exact number of

the last time I checked their catalog. It is easy enough to

turns you’ll need is going to depend on the tuning

build a 90 volt “stack” of batteries. You can build a

capacitor you use and the stray capacitance that results

battery “pack” by buying ten 9 volt transistor radio

from your particular component layout among other

batteries, and taping them together with electrical tape.

things. You’ll have to experiment to get the right

When you do this, alternate their terminals so that you

number of turns.

can easily wire the batteries in series.

77

The tube manuals lists the filament current at 260 mA.

triode tubes, many of which were better suited for the

A voltmeter will show that the filament battery voltage

Doerle receiver circuit: see the 6SL7 Doerle receiver

drops about .2 volt over 15 to 20 minutes of operation.

schematic shown in Figure 7-5.

The batteries will last quite a long time. As for B+, a

If you elect to build this modified version of the

“stack” of 9 volt transistor radio batteries produced

Doerle, you will need to locate a 6SL7. The 6SL7 is a

about 97 volts. With the receiver fired up and properly

glass octal high-µ or (hi-gain) twin triode. The µ (mu)

adjusted, the current draw was only 4 mA, significantly

of a tube is the amplification factor, or voltage gain.

less than what a transistor radio battery is capable of

Although the value of what is considered “high µ” has

delivering. After several minutes, the B+ battery

increased over the years, today “high” means a µ of

dropped to 95.9 volts, so you can expect to get long life

from 60 to 100 or more. That means that the maximum

out of this battery pack. Several changes of filament

voltage gain possible is 60 to 100, but usually it is

batteries will be needed before the B+ battery dies.

significantly less.

So how does a Doerle radio receiver perform? For

High voltage gain tubes usually don’t develop very

such a simple radio, it performs very well. Just a quick

much power. High power tubes usually have lower

run through the band allowed me to copy amateur CW

voltage gain. You can get both in the same tube.

and marine Morse code. The foreign shortwave

The #19 is an audio power tube with a relatively low µ.

broadcasters came blasting-in.

The 6SL7, on the other hand, has a µ of 70, but delivers

Improvements? Yes, I can think of some. First, a

little power. If you build both the #19 and 6SL7

volume control would be useful. I suspect that radio

versions, you’ll immediately hear the increased

stations today run far more power than they did in the

headphone volume of the latter tube. Headphones don’t

30s. Therefore, the signals in the headphones are so

need much power, so high voltage gain tubes works

loud as to be painful. A volume control would be useful

well, although more gain is usually better. A medium-µ

to cut some signals down to size. I find the tuning a

tube like the #19 triode will give great performance.

little too fast. Tuning a single sideband signal in is

The 6SL7 was very common, and is still available. It is

touchy and difficult in some cases. This could be fixed

a higher-power, lower-voltage-gain tube with the same

by going to five pin coils forms where the tuning

pin-out arrangement as the 6SL7.

capacitor could be attached to a tap in the tuning coil.

The only major change introduced into this version of

Such a modification, however, changes the Doerle kit

the Doerle is the mechanical layout. In this version, the

which was built for shortwave listeners, not amateurs.

prototype used an old National ACN dial drive, found at

If you’re a ham, you’ll probably want to modify the

a local hamfest or flea-market, for a couple of dollars.

design so that a ham band is spread out along the whole

I mounted it on an aluminum face place wrapped

dial. And the last change that I would make is to

around a piece of 1 × 6 oak. The actual planetary drive is

improve the antenna trimmer adjustment. Adjusting the

identical to that under the phenolic dial plates of the

trimmer with a screwdriver can be painful after awhile.

Velvet Vernier used in the model 19 Doerle. The ACN is

You don’t do it very often, but when necessary it’s not a

much larger, 5′′ × 7′′ overall, and allows the user to mark

convenient thing.

a paper scale so that the dial becomes direct reading.

The antenna coupling trimmer was replaced by an

8-18 pF air variable stripped from an old radio.

The 6SL7 Doerle receiver

A custom bracket was snipped out of aluminum sheet

and quickly bent up. By mounting the bracket on the

In 1934, there was only one dual triode available for

wood base away from other meta components the

battery operation, the #19 dual triode! But the 1930s

capacitor electrically “floated” as needed. A knob

were years of explosive growth in the electronics

allows the operator to reach around the side and easily

industry. Just months after the #19 triode was released

adjust coupling when necessary. But you can take a

new metal tubes appeared, and in another ten years,

similar small capacitor and cannibalize it by removing

seven and nine pin miniature tubes became available.

one or more plates to reduce the capacity. Just try get

Chapter Seven: Super-Regenerative Radio Receiver These new series of tubes offered a variety of new dual something less than 50 pfd for antenna coupling.

78

Chapter Seven: Super-Regenerative Radio Receiver

Figure 7-5

New 6SL7 Doerle received

A half megohm potentiometer replaced the

since you have to supply 6.3 volts AC into the filaments.

330 kilohm grid resistor used in the audio side of the

Remember the original Doerle radio had 2.5 volt

original receiver, by connecting the panel-mounted pot

filaments, and you’ll need about 150 volts for the plates

to the rest of the circuit with miniature coaxial cable to

on the 6SL7.

reduce AC hum. In the original circuit, the audio grid

Does the 6SL7 version of the Doerle radio work?

was biased as before, but now has control over the

It sure does! You can use the same coils used in the

volume. With a high gain tube like the 6SL7, it is

original version of the Doerle radio for the 6SL7

important to reduce the audio output so that you don’t

version of the radio. When powering this version of the

destroy your hearing. A one kilohm resistor and a

Doerle receiver be sure to set the volume control all the

10 mfd capacitor in parallel are inserted in the cathode

way down before applying power, since the audio

lead of the audio triode to provide at least some

output is much greater than that of the original radio.

negative bias to help the tube amplify with less

Put on a pair of headphones and turn on the 150 volts

distortion. You may want to increase or decrease the

B+. Remember, you must use high impedance type

value of the resistor to achieve the necessary grid

headphones for this type of radio, not 8 ohm types. The

voltage specified in the tube manual. The voltage you

Internet is a good source of the old 2000 ohm high

measure across the cathode resistor is your grid bias.

impedance headphones. Bringing up the regeneration

If you compare the original circuit with this version,

and audio controls brought in stations immediately.

you’ll find that almost all the same components can be

Many stations appeared across the dial, and they were

used. The few differences are minor. And, again, don’t

surprisingly easy to tune in.

be afraid to substitute. Just about anything within reason

One important change in this circuit is the use of two

will work.

capacitors in the main tuning LC circuit. In the circuit

The biggest problem with this version of the Doerle

shown, you’ll see a 50 pF fixed capacitor is parallel

receiver is that you will likely need a power supply,

with a 100 pF variable capacitor. Since capacitance in

79

parallel adds, the combination of the two essentially

decrease the band of frequencies covered by the coil

creates a virtual variable capacitor with a range of 50 to

being used. You might want to replace the 50 pF fixed

150 pF. The net effect is to slow down the rate of

capacitor with a 140 pF for use as a band-set capacitor

tuning. The amount of band that can be covered by a

and a 35 pF for use as a band-spread capacitor.

single coil is reduced, but makes tuning far less

Both should be equipped with slow-motion dial drives.

“touchy.” This is important when tuning a sideband

You can use just about any dial drive that turns

signal because very slight changes in tuning are

up at a flea market or in a radio parts catalog. You can

needed to clear up the signal. You might want to

mix and match components. Many times you’ll need

replace the 50 pF with a 20–150 pF trimmer or

more mechanical skills than you will need electronic

something similar. By adjusting the trimmer, you can

skills for building old radios, so dig through

change the “speed” at which signals are tuned in. More

your junk box, visit a hamfest and have fun building an

capacitance reduces the speed, but it will also

old radio!

Chapter Seven: Super-Regenerative Radio Receiver

80

Chapter 8

IC Shortwave Radio Receiver

C2

330 pF, 35 vdc

Parts list

mylar capacitor

C4,C6,C8,C28

.01 µF

Shortwave Receiver

disk capacitors, 35

Project

vdc (marked .01, 103,

R1,R5,R20

100k ohm, 1/w

or 10nF)

4

5% resistor [brown-

C5,C17

100 pF disk

black-yellow]

capacitors, 35 vdc

(marked 100, 101,

R2,R4

22k ohm,1/w,

4

or 100K)

5% resistor

C7,C10,C12,C18,C19,C29

R3,R7,R9,R10

1k ohm,

1

1 µF ceramic disk

/w 5% resistor

4

capacitor, 35 vdc

[brown-black-red]

(marked .1 or 104)

R13,R17,R18,R24

1k ohm,

1

C9,C24

1 µF, 35 vdc

/w 5% resistor

4

electrolytic capacitor

[brown-black-red]

C11,C22,C23,C27

10 µF,

R6,R8,R11,R19,R23

35 vdc electrolytic

10k ohm, 1/w

4

capacitor

5% resistor

[brown-black-orange]

C13,C14

220 µF, 35 vdc

electrolytic capacitor

R12

1M ohm, 1/w

4

5% resistor

C15

(see text)

[brown-black-green]

C16

(see text)

R14,R21

10K

C26

1000 µF, 35 vdc

potentiometers, 103,

electrolytic capacitor

or 10nF

C30

10 pF, 35 vdc

R15

2 ohm, 1/w

mylar capacitor

4

5% resistor

L1,L2

1 µH molded type

[red-black-gold]

inductor

R16,R22,R25

270 ohm,

(brown-black-gold)-

1/w 5% resistor

Digi-Key

4

[red-violet-brown]

L3

12 µH molded type

R26

100 ohm, 1/w

inductor (brown-red-

4

5% resistor

black) -Digi-Key

[yellow-violet-orange]

T1,T2

shielded can

C1,C3,C20,C21,C25

inductor

.001 µF, 35 vdc disk

(42IF-103) Mouser

capacitor

Electronics

81

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

T3

shielded can

inductor (42IF-123)

Mouser Electronics

D1

1N270 diode, glass

bead style

D2

Red LED (RSSI)

D3

Varactor diode,

transistor style with

2-leads (MVAM108)

Q1,Q2,Q3

2N3904 NPN

Figure 8-1

Shortwave radio

transistors

U1

LM358 8-pin DIP IC

U2

LM386 8-pin DIP IC

familiar with the world of shortwave broadcasting,

you’ll be deciding on your own favorite band. You will

S1

DPDT PC-mount

hear a variety of other “interesting” sounds, but just

pushbutton switch

remember that this receiver is designed for AM only.

J1

RCA-type PC-mount

If a Morse code signal really sounds “good,” it is

jack

because it is being transmitted in AM tone-modulated

J2

subminiature 1/ inch

form, or perhaps the signal is so close to an AM

8

PC-mount jack

broadcast carrier that the carrier acts as a “beat-

B1

9 volt transistor

frequency-oscillator” (BFO). Even though this receiver

radio battery

will permit you to tune through several different ham

radio bands, the signals are not likely to be intelligible.

Misc

PC board, battery

Reception of CW and SSB signals on an AM receiver

holder, battery clip,

requires a BFO. This is not a complicated feature, but it

wire, hardware,

is not a feature of this receiver. Our companion

speaker

receivers designed for the ham bands will let you tune

Have you ever wanted to listen-in into the fascinating

into these SSB and CW broadcasts.

Shortwave Radio Receiver world of radio? The shortwave radio project will allow you to listen to international stations such as the BBC,

Radio Canada, Radio Moscow, Radio Sweden. Using

just a few feet of wire as you antenna you will be able

Shortwave listening

to reach out and hear the world. Shortwave listening is

as a hobby in itself

fun for folks of all ages from 8 to 80 years of age.

The shortwave radio project shown in Figure 8-1

Many people worldwide enjoy listening to shortwave

covers the shortwave bands from 4 to 10 MHz. The

broadcasts of all kinds, and they keep written records of

receiver uses varactor diode for smooth tuning across the

what they hear. Almost every nation on Earth has some

band. The superheterodyne shortwave receiver provides

sort of shortwave broadcast service, though many are

both great sensitivity and selectivity. The tuning control as

much more challenging to tune than the powerful signals

well as the volume and RF gain controls are all located on

of Radio Moscow and the BBC. In addition, these

the front panel for easy operation. The shortwave receiver

“SWLs” (Shortwave Listeners) listen to ham operators,

is powered from a common 9 volt transistor radio battery,

government and commercial stations and even clandestine

so the receiver can be taken virtually anywhere. The

operations. Some shortwave listeners enjoy collecting

receiver would make an ideal scout, school or club project.

QSL cards from stations which they have logged.

You’ll easily tune into broadcasts from many other

Shortwave listening is, for some, a step toward getting a

Chapter Eight: IC countries as well. As you become more and more ham radio license. For others, it is a great hobby in itself.

82

Chapter Eight: IC

The Shortwave Receiver is a good introductory

antenna are applied to the RF input and filtering allowing

receiver for this hobby. After you decide exactly what

only the signals of interest to pass through. The high pass

kinds of listening are of the most interest to you, you’ll

filter helps eliminate unwanted signals picked up by the

be in a better position to choose a more elaborate

antenna, so improving the overall reception quality of the

receiver.

radio. After the input signal is filtered, it moves to the

To learn more about this SWL hobby, look for a copy

mixer stage. Notice on the diagram that there are two

of Popular Communications at newsstands. An

inputs to the mixer. We have discussed one of these input

inexpensive and interesting general introduction to all

signals coming into the mixer but not the other. Now,

kinds of radio listening is the book, Shortwave Listening

look down at the local oscillator block. The local

Guide by William Barden, Jr. (1987; Radio Shack

oscillator (LO for short) acts as your tuning control for

Catalog Number 62-1084). To learn more about the

what frequencies you can receive by generating a signal

hobby of ham radio, write to ARRL (American Radio

on the board close in value to that which will be used by

Relay League), 225 Main Street, Newington,

the mixer. There is a direct relationship between the

CT 06111.

generated frequency of the local oscillator (LO) and the

exact receive frequency (Fc) you want to listen to. This

will become clear when we finish discussing the block

diagram. The LO section is a Colpitts oscillator that takes

Circuit description

advantage of smooth varactor diode tuning. The varactor

Shortwave Radio Receiver

(D3) forms an L/C (inductor/capacitor) tank circuit with

Take a moment and examine the shortwave receiver

T3. Increasing the voltage on the varactor diode with

block diagram in Figure 8-2. The simplified signal flow

R21 (tuning pot) increases the capacitance of D3, thus

of the block diagram shows the basic sections of the

increasing the frequency output of the LO section.

receiver. The corresponding components are noted

Now that we know the two signals coming into the

under each main block and can be cross-referenced to

mixer stage, both the Fc (receive carrier frequency)

the schematic.

and the LO (generated local oscillator), we can better

The main shortwave receiver diagram is illustrated in

cover its operation. The mixer takes these input

Figure 8-3. The receiver circuit begins at the antenna

signals and performs a few very basic operations. The

input at J1. RF signals (Fc = carrier frequency) from the

technical explanation of how the mixer combines these

Figure 8-2

Shortwave receiver block diagram

83

C h a p t e r E i g h t : I C

S h o r t w a v e R a d i o R e c e i v e r

84

Figure 8-3

Shortwave receiver schematic. Courtesy of Ramsey Electronics

Chapter Eight: IC

signals through Fourier Series is interesting but very

the LED will glow. This is great for help pulling in

drawn out. The point of using the block diagram,

those weak transglobal transmitter signals. The gain of

however, is to simplify matters. Therefore, the

the RSSI circuit is controlled by the value the

function of the mixer is to obtain the “product” and the

feedback resistor R17. If you are commonly using a

“sum” of the input signals. This means you take the

small whip antenna and listening to weak signals,

input signals and merely “add” and “subtract” their

you may need to increase the value of R17 to

values to determine what you get on the output.

customize the response indication of D2, the signal

The general formulas to use are quite simply,

strength LED.

“Fc + LO = Mixer Output” and “Fc – LO = Mixer

The final stage, and the real secret to the sensitivity

Output.”

of the receiver, is the Automatic Gain Control (AGC).

The output of the mixer stage unfortunately has other

The gain control looks at the amount of signal level

signals besides the ones we want. This brings us to the

present at the output of the demodulator and varies the

next stage, Intermediate Frequency Filtering. An

amount of gain the amplifier has accordingly. If there is

Intermediate Frequency (IF) is a signal somewhere

a strong signal coming through the demodulator the

between the RF signal Fc we started with and the final

AGC circuit lowers the gain of the amplifier.

audio message we are trying to get. The desired

If the received signal coming through the demodulator

IF we are dealing with is a fixed number, such as

is very weak, the AGC circuit increases the

Shortwave Radio Receiver

455 kHz. As long as the proper relationship between

gain of the amplifier (Q2) allowing us to receive

Fc and the LO exists, the IF value will stay constant.

signals from around the world and listen to them

Due to the fact that the IF frequency stays the

with clarity.

same all the time, the Intermediate Frequency Filter can

be very narrow. The filter will remove any other

signals coming from the mixer that are not in the proper

pass band and yield a clean signal for further

Receiver assembly

processing.

Look for a clean well lit area in which to assemble your

The next stage is an amplifier with an adjustable gain

shortwave receiver. You will need a 27 to 30 watt pencil

feedback loop. The gain control is dependent on the

tip soldering iron, some 60/40 tin/lead rosin core solder,

amount of signal being received (this Automatic Gain

a few hand tools including a pair of end-cutters, a

Control “AGC” will be covered in a moment). The

needle-nose pliers, a few screwdrivers and a pair of

amplifier boosts the signal level of the incoming IF and

tweezers to pick up small parts. Locate your schematic

gives us a stronger signal to work with. After the

and layout diagrams and we will begin to construct your

amplifier stage is another Intermediate Frequency Filter.

new shortwave receiver. Let your soldering iron tip heat

This helps remove any unwanted residual signals still

both the component lead wire and PC board trace

present and cleans up the amplified IF for a high quality

enough so that the wire itself AND the foil trace BOTH

signal. At this point the audio signal we are trying to

become hot enough TOGETHER to melt a bit of solder

obtain is riding on the IF signal.

so that it flows smoothly from the pin to the PC board

trace. Locate the printed circuit board and all the

The demodulator circuit finally extracts the

components and we will start.

message from the IF section through a process called

envelope detection. Now that we have our message

Before we begin constructing the shortwave receiver,

back in the audio realm, it is directed through the

refer to the resistor color code chart in Table 8-1 and the

audio circuitry to the speaker output. The demodulated

capacitor code chart in Table 8-2. Each resistor will

audio branches off before the audio circuitry and

have three or four color bands on them. The first color

is used to perform some useful functions. The RSSI

band will start close to one edge of the resistor body.

LED, Received Signal Strength Indicator Light

The first color band will represent the first digit of the

Emitting Diode, gives us a general signal level

resistor value. The second color band will represent the

feature. The stronger the signal we receive, the brighter

second digit value, while the third color band illustrates

85

Table 8-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

the resistor multiplier value. The fourth band, if there is

observed for the circuit to work correctly. Look through

one, will represent the resistor’s tolerance value.

the parts pile and locate the capacitors and place them

A silver band is a 10% tolerance, while a gold band

in front of you. You will notice a number of small disk

depicts a 5% tolerance value. No fourth color band

capacitors, we will install these first. Look closely at

notes a resistor with a 20% tolerance. Locate all of the

each of the disk capacitors at their markings. Sometimes

resistors for the project and place them in front of you.

the capacitors are very small and they may not have

Each resistor has a color code which describes its value.

their actual value printed on them but will instead have

Check the color code against the parts list and

some sort of code. Refer to the parts list for these codes.

schematic before installing them onto the circuit board.

Locate four or five of these small disk capacitors,

Shortwave Radio Receiver Place about four or five resistors on the PC board and identify them and install them on the circuit board,

place these resistors in their respective locations

while referring to the schematic and layout diagrams.

carefully making sure each one is in the correct

After inserting the disk capacitors onto the circuit

location. Next solder each of the resistors onto the

board, you can go ahead and solder them to the circuit

circuit board. Trim off the excess component leads with

board. Remember to cut the excess component leads.

a small pair of end-cutters. Pick up and identify the next

Next move on and install another grouping of small disk

grouping of resistors and install them on the circuit

capacitors, then solder them in place on the printed

board, follow up by soldering this next batch of resistors

circuit board. Cut the extra component leads after

to the circuit board, remember to trim the extra lead

soldering in the capacitors. When you are finished

lengths form the PC board.

installing the small capacitors we will move on to the

Once all the resistors have been installed onto the

larger electrolytic types.

circuit board we can move on to identifying all of the

Capacitors C9 and C24 are 1.0 µF electrolytic

capacitors for the project. Note that there will be

capacitors and capacitors, while C11, C22, C23, and

different-looking capacitors for this project, some will

C27 are 10 µF electrolytic capacitors. Capacitors C13

be small disks, while others will be larger body devices

and C14 are 220 µF, while C26 is a 1000 µF electrolytic

with minus and plus marking on them. These larger

capacitor. When installing these capacitors you must

capacitors with polarity marking are electrolytic

orient them with respect to their polarity. Each

Chapter Eight: IC capacitors and they have polarity which must be electrolytic will have either a plus or minus marking

86

Chapter Eight: IC

Table 8-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Shortwave Radio Receiver

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

820 pF

Ceramic

821

2

Mylar

205

87

EBC

EBC

1

8

1

8

1

8

1

8

MVAM108

2

7

2

7

3

6

3

6

4

5

4

5

LM358

LM386

1 2

C

C

B

B

E

E

NPN

NPN

2N3904

2N3904

Figure 8-4

Semiconductor pin-outs

on them. You must look at the schematic and layout

each will most likely have three leads, a Base lead, a

diagram and observe the polarity marking on the

Collector lead and an Emitter lead. The symbol for a

diagram match up with the markings on the capacitor

transistor is a vertical line, with two other leads, at 45°

when installing them to ensure that the circuit will

angles, pointing to this vertical line. One of these angled

work. Failure to observe polarity marking may result in

leads will have a small arrow pointing towards or away

damage to the circuit when it is first powered up.

from the vertical line, this lead is the Emitter lead. The

Identify these electrolytic capacitors and install on the

vertical lead is the Base lead and the remaining lead is

PC board. Solder them in place and then cut the extra

the Collector. Locate and identify these four transistors

lead lengths flush to the edge of the circuit board.

and install them on the PC board. Be sure you can

Take a short break and locate the semiconductor

identify each lead and that each lead goes to the correct

pin-out diagram, shown in Figure 8-4, which illustrates

PC hole on the board; refer to the layout diagram and

the output pins of the transistors and integrated circuits

schematic before soldering the transistors to the printed

in the receiver. Next, let’s move on to identifying and

circuit board. Don’t forget to trim the excess lead from

Shortwave Radio Receiver installing the two diodes; note that diode D2 is the the transistors after the transistors have been soldered to

varactor or tuning diode and D1 is a glass bead style

the board.

diode, while D3 is the red LED RSSI indicator. Diodes

Now, it’s time for a little “destruction”! (If you

have marking on them that denote polarity and it must

jumped ahead and installed T3, we’ve got bad news for

be observed for the circuit to work correctly. You will

you.) Before this, two shielded transformers can be

notice that a diode will have a small black or white

installed, and the internal capacitors need to be

colored band at one end of the diode body. This band

removed. Looking at the underside of these two

denotes the diode’s cathode. You will remember that a

transformers, you’ll see a tubular part, probably white

diode’s symbol looks like a triangle pointing to a line.

with a brown band, somewhat like a resistor. These are

Well, the triangle is the anode and the line corresponds

brittle and easily crushed with any sharp object that can

to the black or white band on the diode. Refer to the

be pressed against them with mild force (small nail,

schematic when installing the two diodes and make sure

small screwdriver). You’ll find these capacitors will

you have installed them in the correct PC locations

easily disintegrate into particles. DO NOT crush the

before soldering them in place. The RSSI LED is

capacitors in the other two inductors. After crushing the

mounted on the front of the PC board near the

capacitor, install T3. Next locate the remaining inductor

potentiometers.

cans, i.e. T1 and T2 and install them on the PC board;

Now locate the three NPN transistors and we will

remember orientation of the inductor cans is important.

Chapter Eight: IC install them on the PC board. Remember that transistors Now locate the small “resistor like” inductor, i.e. L1,

88

Chapter Eight: IC

L2 and L3. Solder the inductors to the circuit board and

Table 8-3

remember to trim the excess leads.

Band selection components

Finally we are going to install the integrated circuits

C16 = .001

T3 Slug In

T3 Slug out

to the circuit board. Consider installing IC sockets,

C15

6.5−13 MHz

9−18.3 MHz

instead of mounting the IC’s directly to the PC board.

C15

5.1−7.9 MHz

7.1−10.7 MHz

Integrated circuit sockets are good insurance in the

event of a possible circuit failure at some later date. It is

C15

4.3−5.3 MHz

6−8.3 MHz

much easier to unplug an IC rather than trying to un-

C16 = 100 pF

T3 Slug in

T3 Slug out

solder one from a PC board. Mount three IC sockets to

C15

8.4−14.2 MHz

11.5−19.5 MHz

the PC boards at the respective locations of U1 and U2.

C15

6−8.1 MHz

8.5−11 MHz

Before installing the ICs we will need to make sure that

C15

4.9−6.3 MHz

6.7−8.4 MHz

you can identify the pin-outs on each of the ICs. Have a

look at the eight pin integrated circuits, note that at the

top of each of them you will see a notch in the center of

the device or a small indented circle at the left side at

range you would like your receiver to tune, and then

the top of the package. The IC pin to the left of the

select the values for C15 and C16 from the chart, shown

notch or indented circle is pin one (1). Refer to the

in Table 8-3. A suggested configuration would be

schematic and layout diagram to observe where pin one

C15 = 47 pF and C16 = 100 pF. This will give you

Shortwave Radio Receiver

(1) is for each of the integrated circuits before installing

complete coverage from 6 to 11 MHz by adjusting T3

them to the PC board. Once you are sure of the pin-outs

in or out. This is a very active section of the shortwave

for each of the ICs and where they go on the PC board,

band and will provide you with hours of listening

you can insert them into the proper IC socket. If there

enjoyment any time of the day. Select and install C15

are any jumpers on the circuit board, you can go ahead

and C16.

and install them now.

Finally, you will need to locate an enclosure for the

Well, we have made quite a bit of progress on

receiver, and then install the circuit board into the

building your shortwave receiver. Take a short break and

enclosure. Place the knobs on the potentiometer shafts,

when we return we will mount the remaining final

locate a 9 volt transistor radio battery and connect it to

components. At this time look through the remaining

the receiver battery clips. Connect up an antenna and

parts and look for the two chassis mounted

you are ready to test out your new receiver.

potentiometers R1 and R2. Place the potentiometes at

Before turning on your receiver, double-check that

the front of the PC board and solder them in place.

you have correctly oriented all three of the ICs,

Now, locate and install the power on-off switch at S1,

that you have correctly oriented the transistors, that you

and solder it in place on the printed circuit board.

have installed the diodes correctly, and that you have

Finally locate and install J1, an RCA chassis jack and

installed the electrolytic capacitors correctly.

J2, the 1⁄8 ′′ phone jack onto the PC board. Locate the

Finally we will inspect the circuit board for “cold”

battery clip and solder it to the PC board, where you see

solder joints and possible “short” circuits. Pickup

the plus and minus markings. The red battery clip wire

the PC board with the foil side of the board facing

will go the plus marking on the board, while the

you and inspect the solder connections. You will

black wire will go to the minus marking on the board.

want to make sure that all of the solder connections

Install the battery clamp. Position battery and holder so

look clean, smooth and shiny. If any of the solder joints

as not to cover nearby PC board mounting holes. Use

look dull, dirty or “blobby” then you should un-solder

the method for securing the clamp that is most

that particular joint and re-solder it over again so that it

convenient for you, such as a (1) wire looped through

looks clean, smooth and shiny. Next, let’s inspect the

clamp and PC board holes and soldered, (2) small screws,

CP board for any possible “short” circuits. Often “stray”

(3) double-faced adhesive strips or (4) hot-melt glue.

cut component leads will “bridge” across between

Your shortwave broadcast receiver is now almost

circuit traces and “short” out a PC trace. Another

finished. Now, you will need to decide what frequency

possible source of “short” circuits is a solder blob which

89

can “bridge” across a circuit trace. Carefully inspect the

their frequencies, particularly at sign-on and

PC board for any solder blobs or “stray” wires before

sign-off times.

connecting up a 9 volt battery.

If you like precision, use a frequency counter or

calibrated receiver to find the SR2’s strong oscillator

signal, remembering that there is a 455 kHz IF

Initial testing and

difference (above or below) between the local

oscillator frequency and the broadcast signal you are

adjustment

hearing.

Now, connect up a speaker or headphones, connect up

some sort of antenna and install a fresh 9-volt battery

Shortwave antenna ideas

and we can begin testing the receiver. We have come to

the “moment-of-truth,” go ahead and turn the receiver

power switch to the “on” position. After adjusting the

The type of antenna you’ll want to use for your

volume to a pleasant level, you should hear some

shortwave receiver depends on the degree of interest

shortwave stations by turning the Tune Control, no

you have in shortwave listening, on whether you are

matter how any of the adjustable coils happen to be set.

limited to an indoor or balcony antenna. If you cannot

While listening to any kind of station, whether

use an outdoor antenna, you can make yourself a whip

broadcast or Teletype, etc., use a small screwdriver to

antenna from telescoping radio antenna from your local

adjust the slugs in transformers T1 and T2 for the best-

Radio Shack store. A better antenna would be to throw a

sounding reception. The Tuning Control covers varying

10 to 20 foot piece of insulated wire out the window,

segments of the bands selected by adjustment of

secured to a pole or tree away from your window.

oscillator coil T3. Adjustment of T3 anywhere between

You could also place a length of wire in your attic to act

the full In position to the full Out position will give the

as an antenna. An even better antenna would be a dipole

user full range between the minimum and maximum

antenna “cut” for the desired radio band of most

frequency coverage set by C15 and C16.

interest. In order to construct your own dipole antenna,

you can refer to the diagram depicted in Figure 8-5.

Both T1 and T2 must be adjusted with a non-metallic

Simply use the formula: 468 divided by the frequency

alignment tool such as is used in radio-TV service. If

in Megahertz for example. If you wanted to construct a

you do not have one, a suitable tool can be made by

Shortwave Radio Receiver

dipole for 7.410 MHz, you would divide 468 by 7.410.

patiently sanding a screwdriver-like blade on the end of

The results would be 63.157 feet, so one-half of that

a wooden match stick, kebab skewer or small plastic

number is 31.5 feet. Each leg of the dipole antenna

crochet needle. Again, please be aware that a metal

would then be 31.5 feet. If you do construct your own

screwdriver blade will drastically increase the coil

dipole antenna, you should keep the antenna away from

inductance and make adjustment quite difficult. T1 and

metal objects and use insulated wire and be sure to keep

T2 are simply adjusted for strongest reception of any

signal range that is tuned in.

If you do not have any sort of testing or frequency

reference equipment whatsoever, the easiest way to

begin using the receiver, is to set the Tune Control at its

midpoint, slowly tune T3 with your alignment tool as

though it were a tuning dial. Stop when you come

into the middle of a group or cluster of foreign

broadcast stations. Try tuning around these stations with

the Tune Control. If you like what you hear, readjust

both T1 and T2 for best reception. Eventually, you will

get a clue as to what general frequency band you are

Chapter Eight: IC hearing, because many stations periodically announce Figure 8-5

Shortwave dipole antenna

90

Chapter Eight: IC

away from all power lines. The lead-in wire for your

their hobby. So you will want to know which bands are

dipole antenna to your new receiver can be a length of

best for night time use, and who is broadcasting at that

RG8X min-coaxial cable.

time. Refer to the chart in Table 8-5, which illustrates

the broadcaster and their frequencies, etc. Usually the

best shortwave bands, for evening use are the lower

frequency bands such as the 40, 41 and 49 meter bands.

Shortwave listening

Use this chart or check on the Internet for the latest

shortwave listings. Have fun!

Shortwave listening is a fun hobby for young and old

alike. Once you have your antenna all set up, it is time

to begin listening to your new radio. The chart in

Troubleshooting tips

Table 8-4 illustrates the most common shortwave bands

and their shortwave frequency in Megahertz vs. their

If you experience difficulty, think of your receiver as

wavelength in meters. Many times the shortwave bands

consisting of several sections or stages: oscillator-mixer,

are referred to in meters, such as the 40 or 80 meter

IF audio and AGC, and final audio output (LM386). The

band, so this chart will help you see the relationship

first step in case of problems is to make sure that the

between the two. As a shortwave radio listener, you will

tunable oscillator is working, which can be done by

want to know what International broadcasters are

listening for its signal on another receiver. After the

Shortwave Radio Receiver

broadcasting when you have time to listen to your new

oscillator circuit is confirmed as working, standard

radio. Most people have spare time in the evening for

signal tracing procedures should isolate any problem,

which will be either an incorrectly installed part, a

defective part or a bad solder connection. Correct

orientation or polarity of all diodes, transistors,

Table 8-4

electrolytic capacitors and ICs is essential.

Popular shortwave bands

Problem:

Strong shortwave broadcast audible

Frequency vs. Meters

throughout tuning range.

Frequency in

Broadcast Frequency – kHz/MHz

Meters

Solution:

This can occur if your antenna is “too

2300−2495 kHz

120 Meters

good” or if the RF Gain control is turned up too high.

3200−3400 kHz

90 Meters

The high sensitivity of the front end is designed for

3900−4000 kHz

75 Meters

simple antennas, with most reception quite satisfactory

with only 25 feet or so of wire.

4750−5060 kHz

60 Meters

5850−6200 kHz

49 Meters

Problem:

7100−7350 kHz

41 Meters

Local AM radio station audible throughout

tuning range.

9400−9900 kHz

31 Meters

11600−12050 kHz

25 Meters

Solution:

Whether this will even happen depends on

13570−13800 kHz

22 Meters

how close you are to a local AM station. It is very

15100−15800 kHz

19 Meters

important that all component leads be as short as

17480−17900 kHz

16 Meters

possible, since just a bit of wire can help D1 and the

18900−19020 kHz

15 Meters

several stages of audio amplification give you a free,

21450−21850 kHz

13 Meters

unwanted “classic crystal radio.” A grounded metal case

25600−26100 kHz

11 Meters

for the SR2 is one possible solution.

91

Table 8-5

Evening shortwave broadcast listings

English shortwave broadcasts to the Americas sorted by time:

1700−1800 NA

U.S.A.

WYFR

13695, 17555

1700−1800 NA, LA

Japan

R. Japan

9535

1700−1900 Am

U.S.A.

WHRI

9840, 15285, 15650

1700−2200 NA

U.S.A.

WBCQ

18910

1705−1905 Am

Canada

R. Canada Int’l

9610

1705−1905 NA

Canada

R. Canada Int’l

9800 drm

1800−1900 NA

U.S.A.

WYFR

13695, 17535, 17555

1800−1900 NA, Su-F

U.S.A.

WBCQ

7415

1830−1845 NA, Eu

Israel

Israel B/C Auth.

6985, 7545, 9345

1900−2000 NA

U.S.A.

WYFR

13695, 17535, 17555

1900−2000 LA

U.S.A.

WYFR

6085

1900−2000 Am

U.S.A.

WHRI

9840, 13760, 15285

1900−2100 NA

U.S.A.

KJES

15385

1900−2100 NA, Sa-Su

Netherlands

R. Netherlands

15315bo, 15525bo, 17725ca

1900−2200 NA

U.S.A.

WWCR4

9975

1900−2400 NA

U.S.A.

WBCQ

7415

2000−2025 NA, Eu, Af

Israel

Israel B/C Auth.

6280, 7545, 15640

2000−2100 Am

U.S.A.

WHRI

11765, 15285

2000−2100 LA

U.S.A.

WYFR

17575

2000−2200 NA

U.S.A.

WYFR

17535, 17555

2000−2400 NA

Costa Rica Univ.

Network

13750

2030−2130 NA, Eu

Cuba

R. Havana Cuba

9505, 11760

2045−2130 Am

Vatican City

Vatican R.

9800 drm

Shortwave Radio Receiver 2100−2127 Eu, As, NA

Czech Republic

R. Prague

5930, 9430

2100−2130 NA, Sa

Canada

CBCNQ

9625

2100−2200 NA, Eu, Af

U.S.A.

WEWN

6890, 15785

2100−2200 NA

Japan

R. Japan

17825

2100−2200 LA

United Kingdom

BBC

9480sc, 11675gr

2100−2200 Am, Sa-Su

U.S.A.

WRMI

7385

2100−2200 Am

U.S.A.

WHRI

9660, 11765

2100−2300 NA

U.S.A.

WWCR1

7465

2100−2400 Am, M-F

U.S.A.

WRMI

7385

2130−2156 NA, Eu

Romania

R. Romania Int’l

6055, 6115, 7145, 9755

2130−2200 NA, M-Sa

Canada

CBCNQ

9625

2130−2200 NA

Netherlands

R. Netherlands

9800ca drm

2200−2257 NA

Netherlands

R. Netherlands

15425fg drm

2200−2300 NA, M-F

U.S.A.

WBCQ

5110

2200−2300 LA

United Kingdom

BBC

5975fg, 9480sc

2200−2300 NA

Canada

R. Canada Int’l

9800 drm

2200−2300 Am

U.S.A.

WHRI

7490, 9660

Chapter Eight: IC

92

Chapter Eight: IC

Table 8-5

Evening shortwave broadcast listings—cont’d

English shortwave broadcasts to the Americas sorted by time:

2200−2300 NA, M-F

U.S.A.

WBCQ

18910

2200−2300 NA, Sa-Su

U.S.A.

WWRB

3185

2200−2400 LA

Guyana

V. of Guyana

3290

2200−2400 NA, Su-F

Canada

CBCNQ

9625

2200−2400 Am

Anguilla

Wld Univ Network

6090

2200−2400 NA

U.S.A.

WWCR3

5070

2200−2400 NA

U.S.A.

WWCR4

9985

2200−2400 NA, Eu, Af

U.S.A.

WEWN

7560, 9975

2200−2400 NA

U.S.A.

WWRB Overcomer

6890

2230−2257 NA, Af

Czech Republic

R. Prague

5930, 9435

2300−2330 NA

Germany

Deutsche Welle

9800ca drm

2300−2350 NA

Turkey

V. of Turkey

5960

2300−2356 NA, Eu

Romania

R. Romania Int’l

6055, 6115, 7105, 9610

Shortwave Radio Receiver

2300−2400 NA

Egypt

R. Cairo

11885

2300−2400 NA

China

China R. Int’l

6040, 11970

2300−2400 NA

U.S.A.

WBCQ

5110

2300−2400 Am

U.S.A.

WINB

9265

2300−2400 NA

Cuba

R. Havana Cuba

9550

2300−2400 NA, LA

China

China R. Int’l

5990ca

2300−2400 NA

U.S.A.

WHRA

5850

2300−2400 Am

U.S.A.

WHRI

7315, 7490

2300−2400 LA

U.S.A.

WYFR

15170, 15400

2300−2400 NA

U.S.A.

WWCR1

3215

2300−2400 NA

U.S.A.

WWRB

3185, 5050

2300−2400 LA, Su-F

U.S.A.

WWRB

5745

2330−2357 NA

Czech Republic

R. Prague

5930, 7345

2330−2359 NA

Sweden

R. Sweden

9800ca drm

2330−2400 NA

Lithuania

R. Vilnius

7325

2330−2400 Am, Su

U.S.A.

WRMI

9955

2335−2400 LA, Su-M

Austria

Osterreich 1

9870

2343−2358 LA, Tu-Sa

Austria

Osterreich 1

9870

Relay site codes: ae-United Arab Emirates, al-Albania, an-Antigua, ar-Armenia, as-Ascension, au-Austria, bo-Bonaire Neth. Antilles, bu-Bulgaria, ca-Sackville Canada, ch-China, cl-Chile, cu-Cuba, cy-Cyprus, de-Delano USA, fg-French Guiana, fr-France, ga-Gabon, ge-Germany, gr-Greenville USA, it-Italy, ja-Japan, ka-Kazakhstan, ko-South Korea, la-Latvia, li-Lithuania, ma-Madagascar, ml-Mali, mo-Moldova, ne-Netherlands, om-Oman, po-Sines Portugal, ru-Russia, rw-Rwanda, sc-Cypress Creek SC, se-Seychelles, si-Singapore, sl-Sri Lanka, so-Slovakia, sp-Spain, sw-Sweden, ta-Taiwan, th-Thailand, uk-United Kingdom, uz-Uzbekistan, wb-WBCQ USA, wr-WRMI USA, wy-WYFR USA, za-South Africa.

Notes – Days of week: Su-Sunday, M-Monday, Tu-Tuesday, W-Wednesday, Th-Thursday, F-Friday, Sa-Saturday, exW-except Wednesday.

Target areas: Af-Africa, Am-America, As-Asia, Eu-Europe, LA-Latin America, ME-Middle East, NA-North America, Oc-Oceania/Australia; Other: alt-alternate frequency, drm-Digital Radio Mondiale, occ-occasional use, se-Special English.

Courtesy of Daniel Sampson; www.primetimeshortwave.com

93

Chapter 9

80/40 Meter Code

Practice Receiver

C19

15-50 pF variable

Parts list

capacitor (main

tuning) - see text

80/40 Meter Direct

C2,C6,C7

.1 µF

Conversion Receiver

monolithic (.1 or 104)

Specifications

C3

see chart below

Sensitivity

3-uV or

C4

not used

better

C5

see chart below

Modes

CW, RTTY (FSK),

C8,C9,C10

.1 µF

SSB, AM

monolithic (.1 or 104)

Audio output

50 mW

C20

.01 µF ceramic disk

typical

(.01 or 103)

Frequency coverage

C12,C13,C14

1 µF,

Portions of the 80,

35 volt electrolytic

75, and 40 meter

capacitor

bands

C16,C17

470 µF, 35 volt

Power Source

9 volt

electrolytic capacitor

transistor battery,

alkaline preferred

C11,C15

10 µF, 35 volt

electrolytic capacitor

PC Board

4.000” ×

4.700”

U1 SA602 RF Mixer IC,

8-pin DIP

80/40 Meter Direct

Conversion Receiver

U2

78L05 voltage

regulator

R2

15 ohm, 1/ w,

4

5% resistor (brown,

U3

LM386 audio

green, black)

amplifier, 8-pin DIP

R3,R8 100

ohm,

1

/ w,

S1

Power On-off

4

5% resistor (brown,

switch

black, brown)

J1

RCA antenna jack

R1

1000 ohm variable

J2

1

/ ′′ headphone jack

8

potentiometer

B1

9 volt transistor

C1

8.2 pF ceramic

radio battery

disk (8.2)

Misc

PC board, IC

C18

100 pF ceramic

sockets, chassis,

trimmer capacitor

knobs, wire, battery

94

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Nine: 80/40 Meter Code Practice Receiver

holder, battery clip,

hardware, etc.

80 Meter Band Tuning

components

C3,C5

470 monolithic

capacitor (471)

L1

6.8 µH variable

inductor, shielded

L2

3.3 µH molded choke

(orange-orange-gold)

L3

33 µH molded choke

(orange-orange-black)

40 Meter Band Turning

Components

Figure 9-1

80/40 meter code receiver

C3

470 pF monolithic

(471)

The 80/40 Meter Direct Conversion Receiver shown in

C5

680 pF monolithic

Figure 9-1, can easily be constructed by a radio neophyte

(681)

in a few hours with the easy-to-follow instructions.

L1

1.5 µH variable

inductor, shielded

L2

1 µH molded choke

(brown-black-gold)

Circuit description

L3

10 µH molded choke

The circuit diagram shown in Figure 9-2 illustrates the

(brown-black-black)

schematic for the 80/40 Meter Direct Conversion

* Inductors available

Receiver. A dipole or suitable antenna is fed directly to

from Digi-Key

input jack J1, which is coupled to potentiometer R1,

Electronics, see

which serves as a continuously variable RF attenuator

Appendix.

and also serves as the receiver’s gain control. Using the

Whether you’re a novice or an “old-timer,” you’ll be

RF gain control to set volume is advantageous as it also

pleasantly surprised at how this dual band Direct

reduces strong in-band signals that could otherwise

Conversion Receiver performs! The receiver can be

overload the receiver front end. Series inductors L2 and

constructed to receive either the 80 meter or 40 meter

L3, and trimmer capacitor C18, provide front-end

amateur radio bands. You will be able to receive AM,

bandpass filtering, and an impedance match to 50 to

CW and SSB, signals from hams around the world.

75-ohm antenna systems. IC U1 is an NE602/612 mixer

Far-away signals are easily copied; and the sensitivity

and Local Oscillator (LO) in an 8-pin dip package. The

of the 80/40 Meter Direct Conversion Receiver rivals

mixer section is an active Gilbert cell design for good

more expensive receivers. This receiver is ideal for

conversion gain and low noise figure. The LO section

practicing and increasing your CW or code efficiency or

uses heavy capacitive loading to minimize frequency

just having fun listening to shortwave broadcasts or ham

drift. Tuning is capacitive, using a modern Hi-Q

radio operators, at home or away. Build the receiver for

miniature plastic variable. The local oscillator (LO)

your favorite band, tuning options allow you to

stability is enhanced by a 78L05 voltage regulator.

customize the tuning range from full-band to 100 kHz or

Since this is a direct conversion receiver, the LO is

less. Powered by a common 9 volt transistor battery, it’s

tuned to the carrier frequency of Single Sideband

always ready for action on vacation and camping trips!

Signals, or to a difference of 300 to 800 Hz on CW

95

Figure 9-2

80/40 meter direct conversion amateur radio receiver. Courtesy of Vectronics signals, to produce an aural output that is differentially

diagram as well as the resistor and capacitor identifier

coupled to a LM386 audio IC. The audio amplifier IC is

charts and we will begin our project. Place all the project

coupled to the headphone jack at J2 by capacitor C16.

components on the table in front of you. The 80/40

The receiver circuit is power from a single 9 volt

direct conversion radio is an RF or radio frequency

transistor radio battery.

project and it is best constructed on a printed circuit

Let’s get started! Before we begin building the

board with large ground plane areas covering the board

80/40 meter receiver, you will need to locate a clean

for the best RF grounding techniques. Once you have all

well lit and well ventilated work area. A large table or

the parts and PC board in front of you, heat up the

workbench would be a suitable work surface for your

soldering iron and we’ll get started!

project. Next you will want to locate a small 27 to

First, find your resistor identifier chart in Table 9-1,

33 watt pencil tipped soldering iron, as well as a roll of

which will help you select the resistors from the parts

#22 gauge 60/40 tin/lead solder and a small jar of

pile. Resistors used in this project are mostly small

“Tip Tinner,” a soldering iron tip cleaner/dresser, from

1⁄4 watt carbon composition type resistors, which have

your local Radio Shack store. You will also want to

colored bands along the resistor body. The first color

secure a few hand tools for the project, such as a pair of

band should be closest to one end of the resistor body.

small end-cutters, a pair of tweezers and a pair of

This first color band represents the first digit of the

needle-nose pliers. Locate a small Phillips and a small

resistor value. For example, resistor R2 has four color

flat-blade screwdriver, as well as a magnifying glass to

bands, the first one is a brown band followed by a green

Chapter Nine: 80/40 Meter Code Practice Receiver round out your tool list. Grab the schematic, parts layout band followed by a black band. The fourth band is gold.

96

Chapter Nine: 80/40 Meter Code Practice Receiver

Table 9-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

The first band is brown, which denotes a digit one (1),

represent its true value. Use the chart to identify the

the second band is green, which represents a digit five

small capacitors in the project. Non-electrolytics have

(5), and the third band is black, which represents a

no polarity markings on them so they can be installed in

multiplier of zero (0), so the resistor value is 15 ohms

either direction on the PC board.

with a tolerance value of 5%. Identify the remaining

Electrolytic capacitors are usually larger in size and

resistors for the project and we can begin “populating”

value and they will have a white or black band on the

the PC board. Place a few resistors on the board at one

side of the capacitor body or a plus (+) or minus (−)

time, so as not to confuse the process. Make sure that

marking on the body of the capacitor near the leads.

you place the correct resistor into the correct PC

These markings are polarity markings and that indicate

location before soldering it in place. Once you solder a

the direction in which the capacitor must be mounted on

few resistors in place on the PC board you can use your

the PC board. Failure to observe polarity when

end-cutter to trim the excess component leads. Cut the

installing the capacitor may result in damage to the

excess leads flush to the edge of the circuit board. Then

capacitor or to the circuit itself, so pay particular

place a few more resistors on the PC board and solder

attention to capacitor polarity when placing the

them on to the board. Remember to trim the component

capacitors on the board. Note that the receiver can be

leads as necessary.

built for either the 80 meter ham band or the 40 meter

Next we will locate the capacitors for the 80/40 meter

ham band. You will need to look at the parts list when

receiver. Capacitors are listed as electrolytic and non-

deciding which band you want to receive. The inductors

electrolytic types. The non-electrolytic types are

L1, L2 and L3 as well as capacitors C3, C4 and C5

generally smaller in value and size as compared with

determine the band selection.

the electrolytic types. Non-electrolytic capacitors, in

Let’s go ahead and place some of the non-electrolytic

fact, can be so small that their actual value cannot be

capacitors on the PC board. Identify a few small

printed on them, so a special chart was devised as

capacitors at a time and place them on the PC board and

shown in Table 9-2. The chart illustrates the three digit

solder them in place. Trim the component leads after.

codes which are often used to represent capacitors. For

Go ahead and install the remaining non-electrolytic

example, a .001 µF capacitor will have (102), while

capacitors after choosing your desired band. Install the

a .01 µF capacitor will have (103) marked on it to

capacitors and solder them in place, remember to cut

97

Table 9-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Nine: 80/40 Meter Code Practice Receiver 820pF

Ceramic

821

2

Mylar

205

98

Chapter Nine: 80/40 Meter Code Practice Receiver

the extra leads flush to the edge of the circuit board.

Let’s finish the circuit board by mounting the

Now, you can go ahead and install the electrolytic

volume control and the adjustable capacitors. The

capacitors onto the circuit board. Go ahead and solder

volume control potentiometer at R1 is a right angle

them in place and trim the leads as necessary.

PC board mounted type, which is placed at the edge

This receiver project uses a number of small

of the PC board as is the main tuning capacitor.

inductors. These small inductors will generally have

Capacitor C18, which is connected at the junction of L3

color bands on them to help identify them. Molded

and C1, is an 8.2 pF trimmer type; go ahead and solder

chokes appear, at first glance, to be similar to resistors

it to the circuit board using two pieces of bare #22 ga.

in both shape and band marking. However, a closer look

stiff single conductor wire.

will enable you to differentiate between the

Locate main-tuning capacitor C19, now locate the

two––chokes are generally larger in diameter and fatter

mounting location for main tuning capacitor C19. The

at the ends than resistors. When doing your inventory,

tuning capacitor was mounted on its side using double-

separate out any chokes and consult the parts list for

sided sticky tape. Remove the protective cover from the

specific color-code information. Note, that inductor L1

double-sided tape, and firmly press the body of

is an adjustable slug tuned type. Remember that specific

capacitor C19 to mount it to the PC board. Firmly press

chokes are used for each band: see parts list before

the double-sided tape over the silk-screened outline for

mounting the chokes. Chokes do not have polarity so

the body of C19. You may decide to mount the tuning

they can be mounted in either direction on the PC

capacitor in a different way. At the rear of the capacitor:

board.

locate the four internal trimmer capacitors, and using a

The 80/40 meter receiver utilizes two integrated

small jeweler’s screwdriver or alignment tool, fully open

circuits and a regulator IC. Take a look at the diagram

(unmesh) all four trimmers. Note: tuning shaft faces

shown in Figure 9-3, which illustrates the

front of board. Bend the two rotor lugs so they are

semiconductor pin-outs. When constructing the project

parallel to the front face of the capacitor as shown

it is best to use IC sockets as an insurance against a

above. Connect the two rotor lugs to the PC board

possible circuit failure down-the-road. Its much easier to

ground points as shown using scraps of lead wire

unplug an IC rather than trying to un-solder it from the

trimmed from resistors as jumper wires. Cut a 6′′ length

PC board. IC sockets will have a notch or cut-out at one

of 24-AWG insulated hook-up wire in half. Remove

end of the plastic socket. Pin one (1) of the IC socket

about 1⁄4′′ of the insulation from each of the cut ends.

will be just to the left of the notch or cut-out. Note that

Solder the jumpers to the capacitor rotor lugs, and to the

pin 1 of U1 connects to C1, while pin one (1) of U2

ground foil run on the bottom of the PC board. Since

connects to C15. When inserting the IC into its

the tuning capacitor has four sections, you can increase

respective socket make sure you align pin one (1) of the

the tuning ranges by paralleling different sections to

IC with pin one (1) the socket. Failure to install the IC

give a greater tuning range: see Table 9-3. If you used

properly could result in damage to the IC as well as to

just the 140 pF section, your tuning range would be

the circuit when power is first applied.

190 kHz, but if you combined the 140 pF section

with the 40 pF section your tuning range would become

180 pF and so forth. Capacitor jumpers: 180 pF = use

140-pF and 40-pF sections paralleled; 222 pF = use

(TO-92)

140-pF and 82-pF sections paralleled; 262 pF = use

Plastic package (z)

140-pF, 82-pF and a 40-pF sections paralleled;

Output

Input

1

8

1

8

302 pF = use all four capacitor sections in parallel.

2

7

2

7

3

6

3

6

The 80/40 meter code practice receiver can be built for

4

5

4

5

either of your favorite ham bands. First you will need to

GND

SA602

LM386

00774433

decide which band you are interested in. Then you will

Bottom view

have to select the proper components from the chart in

78L05

Table 9-4, for the band of interest. Note that you will have

Figure 9-3

Semiconductor pin-outs

to select three capacitors and three coils for each band.

99

Table 9-3

looks good. Next, we will look the board over for any

Band tuning range

possible “short” circuits which are often caused by

“stray” component leads cut from the board or from

80 Meter Tuning

small solder blobs which may have bridged between

302 pF

350 kHz

circuit traces. Rosin core solder can often leave a sticky

262 pF

310 kHz

residue which will collect component leads and solder

222 pF

270 kHz

blobs, so look the PC board over carefully for any

180 pF

230 kHz

foreign objects on the foil side of the board.

140 pF

190 kHz

The 80/40 meter receiver radio prototype was

82 pF

110 kHz

mounted in a metal chassis box on plastic standoffs.

40 pF

55 kHz

The PC board was aligned in the enclosure so that the

volume control, and main tuning control and power

40 Meter Tuning Range

switch were all mounted at one side of the case. Alight

302 pF

N/A

the PC board along the edge of the chassis box, so that

262 pF

N/A

you drill holes in the chassis for the volume and tuning

222 pF

N/A

controls. The 1⁄8 ′′ switched headphone jack at J2 was

180 pF

310 kHz

mounted on the front of the chassis, while the antenna

140 pF

250 kHz

input jack at J1 was mounted on the rear of the case. The

9 volt transistor radio battery was mounted in a battery

82 pF

150 kHz

holder which was fastened to the bottom panel of the

40 pF

75 kHz

chassis box.

Your new 80/40 meter direct conversion receiver

project is almost completed. Apply the battery clip to

Let’s take a few minutes for a short well-deserved

the 9 volt battery. Connect up an antenna to the antenna

break, and when we return we will look over the circuit

jack, a dipole antenna cut for the band of interest would

board for any possible “cold” solder joints or “short”

be the best type of antenna. For test purposes, you could

circuits. Pick up the circuit board with the foil side

connect a long piece of wire to the antenna jack for a

facing upwards toward you. First, we will examine the

temporary antenna. Plug in an 8 ohm headphone and

circuit board for “cold” solder joints. Take a look at all

then, turn on the power switch to the “On” position.

of the solder joints on the board, they should look clean,

Now, adjust the volume control to the mid-position and

bright and shiny. If you see any solder joints which look

then turn the main tuning control. If all-goes-well, you

dark, dull or “blobby,” then you should remove the

should begin to hear some radio stations. You may want

solder with a solder-sucker and then reapply more

to test the radio in the early morning or evening when

solder and re-solder the joint all over again so that it

these two bands are most active for best results.

Hopefully you will hear some stations while you tune

across the band.

Table 9-4

If for some reason, your receiver is DEAD, then you

80/40 Band change components

will want to turn off the receiver and remove the battery

clip and do another inspection of the circuit board. This

40-Meter Components

80-Meter Components

inspection is best done by another pair of eyes, someone

who is skilled at electronics might be your best choice

C3 - 470 pF capacitor

C3 - 470 pF capacitor

for inspection. You will want to make sure that you

C4 - not used

C4 - not used

installed the electrolytic capacitors correctly with

C5 - 680 pF capacitor

C5 - 470 pF capacitor

respect to their polarity. You will also want to make sure

L1 - 1.5 µH molded coil

L1 - 6.8 µH molded coil

that the integrated circuits are aligned correctly in their

L2 - 1 µH molded coil

L2 - 3.3 µH molded coil

respective sockets: it’s easy to make a mistake. Check to

Chapter Nine: 80/40 Meter Code Practice Receiver L3 - 10 µH molded coil L3 - 33 µH molded coil

make sure that the regulator IC at U2 was correctly

100

Chapter Nine: 80/40 Meter Code Practice Receiver

installed with the input of the regulator going to

capacitor C12, and the output of the regulator going to

Receiver alignment

capacitor C11. Finally, make sure that you have the

battery clip polarity wired correctly. Once you have

method 2: using a signal

examined the circuit board once more, you can go

generator

ahead and reconnect the battery and antenna and try the

receiver again to see if it works now.

First, set the signal generator to the direct conversion

If your receiver is now working correctly, we can

receiver’s lowest operating frequency. Set the generator

move on to the alignment of your new receiver.

output level for a 30-µV CW signal. Next, connect the

There are two primary methods of aligning the

generator RF output to the VEC direct conversion

receiver’s local oscillator.

antenna jack (J1) using coax cable and the appropriate

mating connectors or adapters. Now, connect a speaker

or headphones to jack J2 on the receiver. At this point,

set the receiver gain fully CW (clockwise) and the

Receiver alignment

tuning knob fully CCW (counter clockwise). Next,

select a tuning tool that properly fits coil L1. The

method 1: using an

20 meter kit requires a hex type alignment tool. The

additional receiver

other kits require a small blade type tool that matches

the slot in the coil core. Or, a jeweler’s screwdriver may

Place your new 80/40 meter receiver next to an amateur

be used. Go ahead and set coil L1 tuning core to the top

or general coverage receiver that covers the band of

of the coil form. Now, connect a fresh 9 volt alkaline

interest. Connect a short 3 or 4 foot wire antenna to the

battery to the receiver, and turn it on using the

receiver, route the antenna wire so it passes near the

push-action power switch. Finally, carefully adjust the

direct conversion receiver PC board. Next, select a

core in coil L1 until the generator signal is heard. Set

tuning tool that properly fits coil L1. The 20 meter kit

the coil for zero beat. Note that metal alignment tools

requires a hex type alignment tool. The other kits

will cause some frequency shift, and interact with the

require a small blade type tool that matches the slot in

tuning when removed or inserted into the coil. You will

the coil core, or use a small jeweler’s screwdriver. Now,

have to adjust the coil in small increments, and observe

set coil L1 tuning core to the top of the coil form. At

the point where the proper frequency is reached when

this time, tune the receiver to the lowest operating

the tool is removed.

frequency by turning the tuning capacitor shaft fully

CCW (counter clockwise). Next, go ahead and set the

monitor receiver to the lowest frequency you wish to

Final alignment

receive on the direct conversion receiver. The receiver

should be set to a wide filter bandwidth, and if it has a

BFO, it should be on. Install a fresh 9 volt alkaline

Once the tuning range is set, the RF input stage must be

battery to the receiver, and turn it on by depressing the

peaked for best sensitivity. This can be done using a

push-action power switch.

signal generator, or on-the-air signals. Find an

alignment tool or jeweler’s screwdriver that fits trimmer

Finally, carefully adjust the core in coil L1 until it is

capacitor C18. Use one of the following three methods

heard sweeping across the monitor receiver frequency.

to peak C18.

Set the coil for zero beat, or strongest S-meter reading

on the receiver. Note that metal alignment tools will

1.

Using a signal generator, peak C18 for best

cause some frequency shift, and interact with the tuning

sensitivity. Reduce the signal generator output, or

when removed or inserted into the coil. You will have to

reduce the R1 Gain control setting, to prevent

adjust the coil in small increments, and observe the point

overload as C18 is brought into resonance.

where the proper frequency is reached when the tool is

2.

Using off-air signals, adjust C18 until signals are

removed.

loudest. Reduce the R1 Gain control as C18 is

101

brought into resonance to prevent overload. Verify

control at R1 for a comfortable listening level.

that C18 is properly peaked while monitoring a

Then, carefully adjust the tuning control until the

known on-air signal.

“beat note,” or tone, sounds best for you.

3.

With an outside antenna connected, peak C18 for

Most experienced CW operators prefer a lower beat

maximum atmospheric noise in the headphones or

note of about 300 or 400 Hz.

speaker. Verify that C18 is properly peaked while

When trying to tune-in single-side band (SSB) stations,

monitoring a known on-air signal.

you may need a little practice to tune-in the signal

properly. Direct conversion receivers offer no upper or

lower sideband rejection, so you will have to slowly

Antenna considerations

tune across the SSB signal until the voices become

natural sounding. Use the gain control to prevent

With your new receiver completed and aligned, you can

overload and to set a comfortable listening level.

attach a dipole antenna for the chosen band of

In order to tune-in AM stations, you will need to

operation. Direct conversion receivers need good

realize that, unlike SSB signals, AM signals have a

antennas. Using a random length of wire will give poor

carrier frequency. That means you will hear a beat note

results. Half-wave dipoles are very effective antennas

as you tune across an AM signal. Tune the signal so the

and are simple to construct. For low-power or QRP

beat note becomes lower in frequency and stop when

work, or for receive only applications, low-cost

“zero beat” (beat note disappears) is reached.

RG-58 52 ohm coax is fine. The formula for dipole

antennas: 234/(frequency in MHz) = 1⁄4-wavelength in feet

will give the length of wire needed for each leg of the

dipole. For example, if you wanted to build a 40-meter

Possible overload

dipole for the CW portion of the band you would divide

234 by 7.040 MHz and the result would be 33.238 feet per

problems

leg on either side of the center insulator: see Figure 9-4.

An unfortunate fact of life is that low-power amateur

signals are surrounded by high-power SW broadcast

signals, so there may be a possibility of overload

problems. In order to compensate for this possible

problem, you may need to lower the gain control.

Simply lowering the gain setting will resolve many

overload problems. Another approach to an overload

problem is to use a preselector. A preselector provides

protection from strong out-of-band signals. They are

most effective when the interfering signal is far from the

operating frequency.

A resonant antenna favors signals in the band it was

cut for, so when faced with a severe overload problem,

you elect to use a resonant antenna. The final approach

Figure 9-4

80/40 meter dipole antenna

to solving an overload problem is to change the

direction the dipole faces; this may lower unwanted

pickup of undesired SW signals. Lowering the

antenna will change its angle of pickup; a low antenna

Tuning notes

may favor local stations over the low-angle of

distant broadcast signals. A shorter antenna can also

While trying to tune CW stations, you should tune

be tried; it will be less efficient and signals will be

Chapter Nine: 80/40 Meter Code Practice Receiver across the band until a CW signal is heard. Set the gain weaker.

102

Chapter Nine: 80/40 Meter Code Practice Receiver

Table 9-5

W1AW on-air code practice sessions

Pacific

Mtn

Central

East

Mon

Tues

Weds

Thur

Fri

6 am

7 am

8 am

9 am

fast code

slow code

fast code

slow code

7-9 am

8-10 am

9-11 am

10-noon

visiting

operator

time

————

————

10 am-12:45 pm

11 am-1:45 pm

noon-2:45 pm

1-3:45 pm

1 pm

2 pm

3 pm

4 pm

fast

slow

fast

slow

fast

2 pm

3 pm

4 pm

5 pm

————

code

bulletin

————

————

3 pm

4 pm

5 pm

6 pm

————

teleprint

bulletin

————

————

4 pm

5 pm

6 pm

7 pm

slow

fast

slow

fast

slow

5 pm

6 pm

7 pm

8 pm

————

code

bulletin

————

————

6 pm

7 pm

8 pm

9 pm

————

teleprint

bulletin

————

————

6:45 pm

7:45

8:45

9:45

————

voice

bulletin

————

————

7 pm

8 pm

9 pm

10 pm

fast

slow

fast

slow

fast

8 pm

9 pm

10 pm

11 pm

————

code

bulletin

————

————

Frequencies are 1.8175, 3.5815, 7.0475, 14.0475, 18.0975, 21.0675, 28.0675 and 147.555 MHz.

Slow Code = practice sent at 5, 71⁄2, 10, 13 and 15 words per minute (wpm).

Fast Code = practice sent at 35, 30, 25, 20, 15, 13 and 10 wpm.

The chart shown in Table 9-5 illustrates the W1AW

help amateur radio enthusiasts increase their code

code practice sessions for Ham Radio operators or those

speed. The ARRL is a great resource for those

interested in obtaining a Ham Radio license. The

interested in Amateur Radio and offers many books,

80-meter frequency is 3.5815 MHz and the 40-meter

magazines and free literature in including videos to help

frequency is 7.0475. The Amateur Radio Relay League

you understand what Amateur Radio is all about. Take a

(ARRL) offers these code practice sessions every day to

few minutes and explore their web-site.

103

Chapter 10

WWV 10 MHz “Time-Code”

Receiver

R32

12k ohm, 1/ w,

4

Parts list

5% resistor

R35,R36

22 ohm, 1/ w,

WWV Time Receiver

4

5% resistor

R1

22k ohm, 1/ w,

4

R37

2.7k ohm, 1/ w,

5% resistor

4

5% resistor

R2,R6,R7,R10

100 ohm,

C1,C2,C6,C7,C15

.001 µF,

1/ w, 5% resistor

4

35v ceramic disk

R16,R18,R30

100 ohms,

capacitor

1/ w, 5% resistor

4

C3,C17,C19,C22

.01 µF,

R3,R21

1 megohm, 1/ w,

4

35v ceramic disk

5% resistor

capacitor

R4

3k ohm, 1/ w,

4

C4,C5,C8,C9,C14

.1 µF,

5% resistor

35v ceramic disk

R5,R11,R12

2k ohm, 1/ w,

capacitor

4

5% resistor

C16,C23,C28,C31

.1 µF,

R8,R13

47k ohm, 1/ w,

35v ceramic disk

4

5% resistor

capacitor

R9

220k ohm, 1/ w,

C10,C11,C12,C13

20 pF,

4

5% resistor

35v plastic capacitor

R14,R24,R29

100k ohm,

C18

1000 pF, 35v

1/ w, 5% resistor

plastic capacitor

4

R19,R22

5.6k ohm, 1/ w,

C20,C21

220 pF, 35v

4

5% resistor

plastic capacitor

R20

27k ohm, 1/ w,

C24,C27

1.0 µF, 35v

4

5% resistor

electrolytic capacitor

R17,R23,R28

4.7k ohm,

C25,C32

22 µF, 35v

1/ w, 5% resistor

electrolytic capacitor

4

R31,R33,R34

4.7k ohm,

C26

2.2 µF, 35v

1/ w, 5% resistor

electrolytic capacitor

4

R25,R26,R27

10k ohm,

C29,C30

390 pF, 35v

1/ w, 5% resistor

plastic capacitor

4

104

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Ten: WWV 10 MHz “Time-Code” Receiver

C33

100 µF, 35v

(F)

3-ferrite beads -

electrolytic capacitor

(see front-end)- run

wire through beads

C34

2200 µF, 35v

electrolytic capacitor

Q1,Q2,Q3

Dual Gate

MOSFET 40673 or ECG222

C35

10 µF, 35v

electrolytic capacitor

Q4,Q5

nJFET MPF102

C36,C37

1000 µF, 35v

Q6,Q7

2N3904 NPN

electrolytic capacitor

transistor

C38

330 µF, 35v

Q8

2N3906 PNP

electrolytic capacitor

transistor

C39

470 µF, 35 volt

U1

Signetics NE5532

electrolytic capacitor

Op-Amp

CV1

10-40 pF trimmer

J1

RCA jack - antenna

capacitor

J2

Coaxial power jack

CV2

10-70 pF trimmer

SPK

8-ohm 3′′ speaker

capacitor

S1

SPST power switch

VR1

10k ohm RF gain

Misc

PC board, wire,

potentiometer

hardware, sockets,

VR2

1M ohm Sensitivity

etc.

potentiometer

VR3

10k ohm volume

Does anybody really know what time it is? The WWV

control potentiometer

receiver, shown in Figures 10-1 and 10-2, is designed to

tune the National Institute of Standards and Technology

L1

4.1 µH coil - 27

(NIST) atomic clock for moment by moment time

turns on T-28-2

accuracy! This is a great receiver project that actually

ferrite core using 22

serves a dedicated purpose. Put one in the boat or on a

AWG wire tap 2-turns

desk and you’ll always know what time it is!

from ground side

The WWV receiver is quite sensitive, and with a good

L2,L4

12 turns on

antenna you should be able to receive time signals most

FT37-43 ferrite toroid

of the time! The receiver features easy tuning and

core

small size, it can be packed up and taken anywhere and

L3

3.0 µH - 25 turns

runs on a 12 volt DC power supply, or a 12 volt

#26 AWG wire on T50-2

battery for portable operation. An earphone jack is

ferrite core

provided for headset operation so you can use it

L5

12 turns on FT37-43

night or day.

ferrite toroid

core

L6

1000 µH coil

D1

1N5711 silicon

Schottky diode NTE 112

D2

optional LED - power

“on” indicator

Y1,Y2,Y3 10

MHz

crystal

Figure 10-1

WWV time code received

105

information is provided by the National Weather

Service. Storm warnings for the Atlantic and eastern

North Pacific are broadcast by voice on WWV at 8, 9,

and 10 minutes after the hour. An additional segment

(at 11 minutes after the hour on WWV) is used

occasionally if there are unusually widespread storm

conditions. The brief voice messages warn mariners of

storm threats present in their areas. The storm warnings

are based on the most recent forecasts. Updated

forecasts are issued by the National Weather Service at

0500, 1100, 1700, and 2300 UTC for WWV. Since

March 1990 the U.S. Coast Guard has sponsored two

Figure 10-2

WWV time code received – inside view

voice announcements per hour on WWV giving current

status information about the GPS satellites and related

People have always been fascinated with the

operations. The 45-s announcements begin at 14 and

measurement and properties of time. What happened to

15 minutes after each hour.

that last second that you just spent reading this sentence?

WWV radiates 10,000 watts on 5, 10, and 15 MHz.

Perhaps this is the reason that so many of us have tuned

The WWV antennas are half-wave dipoles that radiate

in over the years to the National Institute of Standards

omnidirectional patterns. The station uses double

and Technology (NIST) “clock” operating at a

sideband amplitude modulation. The modulation level is

transmitting frequency of 10 MHz. The cesium standard

50 percent for the steady tones, 25 percent for the

NIST-7 has an accuracy of 5 × 10-15 seconds. Now that’s

BCD time code, 100 percent for the seconds pulses

accurate! In fact, the definition of a “second” is the

and the minute and hour markers, and 75 percent for the

duration of 9,192,631,770 periods of the radiation

voice announcements. That’s a lot of information being

corresponding to the transition between the two hyperfine

broadcast, and you can easily pickup these signals with

levels of the ground state of the cesium-133 atom.

the high frequency 10 MHz Time Receiver shown in

We set our clocks, watches, and chronometers to the

this project. The WWV Time receiver has excellent

all-important “beep” of the radio signal that denotes the

sensitivity, selectivity, and dynamic range. (from the

correct time to the second. In addition; avid listeners of

NIST web site http://www.nist.gov/)

the NIST clock are also treated to the following

(from the NIST web site).

The OMEGA Navigation System status reports are

Circuit description

voice announcements broadcast on WWV at 16 minutes

after the hour. The OMEGA Navigation System consists

The 10 MHz WWV Receiver is shown in the block

of eight radio stations transmitting in the 10- to 14-kHz

diagram of Figure 10-3 and in the main schematic

frequency band. These stations serve as international

diagram in Figure 10-4. The WWV Time Code receiver

aids to navigation. The status reports are updated as

is an AM TRF or Tuned Radio Frequency or TRF type

necessary by the U.S. Coast Guard. Current geophysical

receiver. This receiver project is designed specifically

alerts (Geoalerts) are broadcast in voice from WWV at

for 10 MHz time signal operation. The block diagram of

18 minutes after the hour. The messages are less than

the WWV receiver illustrates the four major sections of

45 s in length and are updated every 3 hours (typically

the receiver. The receiver’s front-end, as shown in the

at 0000, 0300, 0600, 0900, 1200, 1500, 1800, and

schematic diagram, features two sensitive dual-gate

2100 UTC). Hourly updates are made when

MOSFETs in the front-end circuit with a single-pole

necessary.

filter. An RF gain control is shown at VR1 which

Marine storm warnings are broadcast for the marine

adjusts the input sensitivity, via a 10k ohm

areas that the United States has warning responsibility

potentiometer. Note inductor L1 is 4.1 µH coil, which

Chapter Ten: WWV 10 MHz “Time-Code” Receiver for under international agreement. The storm warning consists of 27 turns of 22 ga. AWG wire wound on a

106

Chapter Ten: WWV 10 MHz “Time-Code” Receiver

Figure 10-3

10 MHz WWV receiver block diagram

T-68 ferrite core. Inductors L2 and L4 consist of 12

The AM detector has three distinct advantages;

turns of 22 ga. AWG wire on an FT37-43 ferrite core,

it has high bandwidth, low distortion and incredible

and finally L3 consists of 25 turns of #26 ga. AWG wire

(and variable) sensitivity. The variable bias control

on a T50-2 ferrite core. For even greater selectivity (but

allows the listener to adjust the bias to maintain

greater insertion loss), you can consider moving the L1

detected audio fidelity even when the RF signal is weak.

tap to 1 turn from ground. Fine tuning the WWV

The detector uses a Schottky UHF mixer diode at D1.

receiver is accomplished by adjusting CV1 and CV2

Increasing the diode bias from zero volts to maximum

trimmer capacitors. The front-end MOSFETs are

causes three things to happen: increased sensitivity,

extremely sensitive to static electricity, so be very

increased audio high frequency response, and a slight

careful in handling them. Note the two ferrite beads,

increase in receiver noise.

one is placed in series with the Drain lead of Q1, while

The AM detector section matches the 2000 ohm

the second ferrite bead is in series with the Drain of Q2.

impedance of the crystal filter stage quite nicely.

These ferrite beads are important, so be sure to

A sensitivity control at VR2 is a 1 megohm

use them. The receiver front-end, at J1, should be

potentiometer, which feeds directly to L6, a 1000 µH

connected to a dipole antenna “cut” for 10 MHz. TRF

coil. Coil L6 is connected directly to a Schottky diode

receivers are especially sensitive and are subject to

at D1. The resultant signal is next sent through a 5.6k

overloading a BCB or Broadcast Band Interference, so

ohm resistor and on to a 1 µF capacitor which feeds the

internal lead lengths should be kept short between

nJFET at Q4. The Source lead of Q1 is connected to the

components and the front-end should be shielded and

Drain lead of Q5, and the Source lead of Q5 is

the receiver placed in a metal enclosure for best results.

connected to ground via a 5.6k ohm resistor. Note the

The output impedance of Q2 is 2000 ohms, which

two 22 µF electrolytic capacitors on each of the Drain

nicely matches the input impedance of the Cohn crystal

leads of the nJFETs.

filter, in the crystal filter section of the receiver. This

When the WWV RF signal is weak, turning the bias

filter utilizes three 10 MHz crystals. Choose 10 MHz

off may result in the detected WWV signal

crystals that are marked for a 20 pF or 32 pF load

disappearing. Increasing the bias will bring the WWV

capacitance if possible. Using a 10 MHz crystal

signal back in. You run the bias control pot about half

oscillator, find three that are closest to one another in

way and, of course, higher as WWV fades out. The

frequency. You may substitute 2.2k ohm resistors

fidelity that the bias adds even when the WWV signal is

instead of the specified 2k with a slight penalty in pass

strong is quite pleasing to the ear. For the 1 µF and

band shape. The crystal filter section utilizes a single

2.2 µF capacitors, I used polyester film types which

dual-gate MOSFET transistor at Q3. Coil L5 is 12 turns

sounded better than electrolytic capacitors.

on an FT37-43 ferrite core. The output of the Cohn

crystal filter is next fed to the input of the AM detector

The audio amplifier section features low noise audio

stage.

amplifier. Distortion is very low as long as the input is

107

C h a p t e r T e n : W W V 1 0 M H z “ T i m e - C o d e ” R e c e i v e r 108

Figure 10-4

WWV time code receiver schematic. Courtesy of VC7BFO – Todd Gale Chapter Ten: WWV 10 MHz “Time-Code” Receiver

not over driven. The audio amplifier section consists of a

Make sure you have a large work table in order to

dual NE5532 op-amp and three transistors. Transistors

spread out all the parts and diagrams. A printed circuit

Q6 and Q7 are NPN types, while transistor Q7 is a PNP

board is highly recommended for this project, so you

type. The input signal from the detector is fed directly to

should have your circuit board in front of you oriented

the volume control at VR3, a 10k ohm potentiometer.

correctly, in order to begin populating the PC board.

The input signal is first sent to the non-inverting stage of

Remember that the components will be mounted on the

the first op-amp at pin 3. The output of the first op-amp

“component” side of the circuit board and soldered on

section at pin 1 is next sent to the second stage of the

the “solder” side of the circuit board, the side with the

op-amp through a .1 µF capacitor in series with a 4.7k

printed circuit traces. Locate a spool of 60/40 tin/lead

ohm resistor to pin of U1:b. The output of U1, at pin 7 is

rosin core solder for this project.

then fed to the output transistor stage. The output of the

First we will begin by locating all of the resistors for

transistor pair is two 1000 µF capacitors which coupled

the project. Most all of the resistors are 1⁄

to a 330 µF capacitor which feeds the 8 ohm speaker.

4 watt carbon

composition type resistors except for the potentiometer.

The entire WWV receiver is powered from a 12 volt

Before we begin building the Time receiver, take a

“wall-wart” power or can be powered from a 12 volt

moment to refer to the resistor color chart shown in

battery for portable operation.

Table 10-1. Note that each resistor will have three or four

color bands beginning at one end of the resistor body.

The first color code represents the resistor’s first digit

Receiver assembly

value, while the second color band denotes the resistor’s

second digit value. The third color band represents the

You are probably quite anxious to begin the assembly of

multiplier value of the resistor and the fourth band denotes

the receiver project; it is best to follow the assembly

the tolerance value of the resistor. If the fourth color band

steps in order. Try to avoid the urge to “jump ahead”

is silver then the resistor has a tolerance of 10%, while a

installing components. Locate your layout and

gold band denotes a 5% tolerance. If there is no fourth

schematic diagram. Place all the components in front of

color band then the resistor has a tolerance of 20%. The

you and locate a 27-30 watt pencil tip soldering iron.

first color band of a 10,000 ohm resistor, for example,

Table 10-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

109

would be brown with a value of (1). The second color

the next group of components. This will keep things in

band would be black with a value of (0). The third color

an orderly fashion.

band would be orange with a value of (000). Read the

Next, go ahead and locate and install the

color codes on the resistors and compare them to the

Schottky diode at D1. Note that the diode has a polarity

parts list and layout diagram so that you place the correct

marking on the glass enclosure. At one end of the

resistor in the correct hole on the printed circuit board.

diode body you should see a black or white band; this

You can install the resistors in groups of four or five.

denotes the cathode side of the diode. Look at your

Solder the first group of resistors onto the circuit board,

schematic diagram to observe the direction of the

then cut the excess component leads flush to the edge of

cathode band in the circuit before you install

the PC board using a pair of small end-cutters. Then

the diodes.

move on to the next group of resistors until all of the

The WWV receiver incorporates six inductors; five of

resistors have been installed.

the inductors are wound on ferrite cores, while L6 is a

Next we will move on to installing the capacitors.

ready-made 1000 µH choke coil. Refer to the chart in

Most all of the capacitors will have some sort of

Table 10-3 for details on winding each of the coils.

marking on them, so compare the value or marking on

When winding the coil you will have to scrape the

the component with the parts list before installing the

insulation off each of the wire ends in order to solder

components on the PC board. Note that capacitors C24,

the coil to the circuit board. You will need to secure the

C25, C26, C27 are all electrolytic capacitors; these

coil to the circuit board using a couple of “dabs” of

capacitors will have additional polarity markings on

rubber cement. Once the coils have been secured to the

them and they must be installed with respect to these

PC board, you can solder the coil leads to the

polarity markings in order for the circuit to work

circuit board, and then remove the excess lead

properly. Each of these capacitors will have a white or

lengths.

black band with either a plus or minus marking on one

Locate the three crystals, Y1, Y2 and Y3 and place

side or edge of the component. You must orient the

them on the PC board. Now solder the crystals to the

capacitor correctly, so you should refer to the layout

PC board and then trim the excess leads flush to the

diagram and schematic diagram when installing these

edge of the circuit board.

parts. Also note that capacitors C32 through C38 are

also all electrolytic types. All the other capacitors have

Before we attempt to install the semiconductors, take

no polarity marking so they can be installed in either

a quick look at the semiconductor pin-out diagram

direction. Now, you will want to refer to the capacitor

shown in Figure 10-5. Now locate the MOSFETs Q1,

code chart shown in Table 10-2, which illustrates the

Q2 and Q3. These devices are very static sensitive and

codes used for small size capacitors. Often very small

must be handled very carefully using an anti-static

capacitors will not have their actual value printed on

wrist-band to avoid damage before they are soldered

them, because there may not be enough room, so a

into the circuit. Transistor sockets are highly

three-digit code was developed. Look at the chart and

recommended for all of the transistors, see the pin-out

compare the numbers on the chart with the actual

diagram for the MOSFETs and make sure you can

capacitors to help identify them. You can go ahead and

identify each of the leads before placing the MOSFETs

install all of the capacitors at this time. It is best to

on to the circuit board. The MOSFETs have two Gate

install the capacitors in groups of four or five at a time,

leads, G1 and G2, as well as a Source lead (S) and a

then solder them on to the circuit board before

Drain lead (D). Once you are sure of each of the leads,

moving on to the next group of capacitors; this helps

you can go ahead and install the MOSFETS onto

keep some order to the building process. It is also

the circuit board. The AM detector portion of the

advisable to check off each of the components

receiver utilizes two nJFETS at Q4 and Q5, these

against the parts list, so you can keep tabs on your

semiconductors are also static sensitive and must be

progress and make sure that all of the parts are

handled with extreme care to avoid damage. The

accounted for. Solder a group of four or five

nJFETS have three leads, like most conventional

components, cut the excess leads and then move on to

transistors, but they have a Gate, Source and Drain lead,

Chapter Ten: WWV 10 MHz “Time-Code” Receiver

110

Chapter Ten: WWV 10 MHz “Time-Code” Receiver

Table 10-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

820 pF

Ceramic

821

2

Mylar

205

111

Table 10-3

Inductor coil winding information

Coil

Value

Ferrite Core

Description

L1

4.1 µH

T-28 toroid (*)

27 turns #22 AWG wire on ferrite core

L2

FT-37-43 (**)

12 turns #22 AWG wire on ferrite core

L3

3.0 µH

T50-2 toroid *

25 turns #26 AWG wire on ferrite core

L4

FT37-43 (**)

12 turns #22 AWG wire on ferrite core

L5

FT37-43 (**)

12 turns #22 AWG wire on ferrite core

L6

1000 µH

pre-wound choke coil; Digi-Key

* Toroids can be obtained from Circuit Specialists; see Appendix.

** FT-37-43 toroid available from RP electronics; see Appendix.

unlike conventional transistors, with a Base, Emitter and

“flat” side with the writing imprinted on it. Be sure to

Collector. Once the nJFETS have been identified, they

follow the parts diagram for correct placement. To

can be installed on the circuit board. Finally, the audio

install, slide the center legs through the circuit board

amplifier section utilizes three conventional transistors.

and push the component as close to the board as

Transistors Q6 and Q7 are NPN types, while Q8 is a

possible without “straining” the leads. Identify the

PNP transistor. Transistors have three “legs” and must

transistor pin-outs and then go ahead and install the

be oriented correctly. Notice that the part contains a

transistors onto the circuit board. Remember to trim the

2N3904

2N3904

2N3906

EBC

EBC

EBC

ECG222

ECG222

ECG222

C

C

C

B

B

B

E

E

E

NPN

NPN

PNP

1

8

MPF102

MPF102

1

8

2

7

3

6

4

5

NE5532

TO-92

TO-92

G

G

S

S

D

D

Chapter Ten: WWV 10 MHz “Time-Code” Receiver Figure 10-5 Semiconductor pin-outs 112

Chapter Ten: WWV 10 MHz “Time-Code” Receiver

excess transistor leads after all of the transistors have

leads for each of the potentiometer leads, so you can

been installed on the PC board.

connect the potentiometer to the circuit board. All three

It is a good idea to use an IC socket for each of the

potentiometers can be mounted on the front panel of the

integrated circuits in the event of a component failure at

receiver enclosure. Using a length of speaker wire,

a possible later date.

connect the speaker to the circuit board. The speaker

can be mounted on the top or front of the enclosure.

If you desire you can customize your new receiver with

Leads length from

an LED power indicator. Install a red LED on the front

panel. Being a diode, this component is polarized and

the board

must be oriented correctly. Examine the LED and notice

how one lead is longer than the other. The longer of the

Now that your soldering skills are at their peak, we’ll

two leads is the anode, or (+) connection. Most diodes

install the integrated circuit. An integrated circuit socket

also have a flat side molded in the component body. This

is highly recommended in the event of a possible circuit

corresponds to the cathode or (−) side of the part. This flat

failure. It is much easier to simply unplug a “burnt” IC,

should face in the direction of the band marking of the

rather than trying to un-solder a defective IC from the

diode. Leave the diode’s leads as long as possible as this

circuit board. Most hobbyists have considerable trouble

component will also mount to the front panel as a power

trying to un-solder multi-pin integrated circuits from a

indicator. You can connect up the LED across the power

PC board successfully, so it is easier to install a socket

input of the circuit’s +12 volt lead and ground.

from the beginning. Most IC sockets will have a notch

You can also customize the receiver by installing a

or cut-out and one end of the plastic package. Pin 1

closed circuit earphone jack if desired, so that the jack

will be just to the left of the notch or cut-out. Make sure

will bypass the speaker when the headphones are

you orient the socket, so that pin 1 will be close to C29,

plugged into the jack.

C31 and R22. When installing the IC into the socket

Moving to the rear of the enclosure, install antenna

make sure you align pin of the IC with pin 1 of the IC

connector J1, you can use an RCA jack or a BNC

socket.

connector as desired. Next, go ahead and mount a

That’s a lot of parts! Take a short break and rest your

coaxial power plug on the rear panel of the chassis and

weary eyes. Before we start up again, we will check

then solder the connectors to the circuit board using a

your solder joints for “short” circuits and “cold” solder

length of insulated wire. Now you will need to decide

joints. First, pick up the circuit board with the foil side

how you will power your new WWV receiver. You elect

of the board facing upwards toward you. Take a close

to power the receiver from a 12 volt battery or

look at the solder joints in front of you. The solder

re-chargeable power pack or from a 12 volt DC “wall-

joints should all look clean, bright and shiny. If any of

wart” power supply.

the solder joints look dark, dull or “blobby,” then you

Congratulations, you have successfully completed

need to remove the solder from that particular joint, re-

your WWV receiver; now let’s move on to final testing

apply solder and re-solder the joint all over again. Next,

of the receiver!

we will inspect the circuit board for possible “short”

circuits. Look closely for small solder “blobs” that often

bridge circuit traces. Also look carefully for any “stray”

components leads which may have stuck to the foil side

Initial receiver testing

of the PC board. Sometimes sticky rosin from solder

can leave a residue that will “hold” pieces of wire on

This project was designed to be pretty much “plug and

the board, often causing “short” circuits between circuit

play,” with minimal testing upon completion. Turn all

traces.

three potentiometers to their mid-point position.

Identify and install the three potentiometer; they can

Connect up you power supply or battery and depress the

now be mounted on the metal enclosure that you chose

power switch. The power on LED should illuminate.

to use for the receiver. Make up three or four inches

Connect up your outdoor antenna via connector J1.

113

Now increase the RF gain control, more clockwise.

10 MHz dipole for your Time-Code receiver, you

You can also adjust the volume control for more gain as

would divide 234 by 10 MHz and the result would be

well. You should begin to hear the “beep” signal from

23.4 feet per leg on either side of the center insulator. The

the WWV Colorado transmitting station. You may have

diagram in Figure 10-6 illustrates a dipole antenna which

to adjust VR2 until the signal is sound best in the

can be used with the Time-Code receiver. Depending

speaker. If the signal is too strong, you may have to

upon your location, you will want to orient the antenna for

adjust the RF gain and volume control as needed.

best reception. The antenna should be placed broad-side

In the event that you do not hear any sounds from your

or parallel towards Colorado for best reception.

new receiver, you will have to turn off the receiver and

remove the battery and do a close inspection of the circuit.

The most common reasons for circuit problems is due to

Using your new WWV

placing the wrong component in a particular circuit board

location or possible reverse placement of a component.

receiver

Take a look at the Time-Code Receiver circuit board very

carefully. Sometimes it is better to get a pair of “fresh

You will have fun learning about other interesting things

eyes” or have a friend take a look at your circuit to find a

on WWV besides the time function feature, such as

possible error. Look at each of the resistors and make sure

accurate tone frequencies, geophysical alerts (solar

you have placed the correct resistor in each resistor

activity reports), marine storm warnings, the global

location; read the color code carefully. Check the

positioning system (GPS) and Omega navigation system

placement of the diodes and electrolytic capacitors to

status reports.

make sure you have installed them with respect to their

Table 10-4 shows the broadcast schedule for

polarity marking. Next, take a close look to make sure that

WWV in Fort Collins, CO. A similar schedule is

you have installed the transistors correctly, looking closely

available for WWVH in Hawaii. This diagram is

at the pin-outs with respect to the manufacturer’s pin-out

extracted from a National Institute of Standards and

diagram. Finally, examine the circuit to make sure that the

Technology (NIST) publication. If you want to order a

integrated circuit has been oriented properly in its IC

copy, it is available for a modest charge from the

socket, since this is a common cause for error. Once you

Government Printing Office, Washington DC 20402.

have fully inspected the circuit board and located your

Write and ask for a current list of available publications.

error, you can re-connect the battery and switch on the

The two features of most interest are precise frequency

receiver to test it once again.

of the carrier signal, to calibrate radio and test

equipment, and precise time information given each

minute as a voice transmission. But there are many

Antenna considerations

other interesting parts of their transmissions.

In order to obtain the best reception on your new WWV

Time-Code receiver you will want to construct an

optimum antenna. Using a random length of wire will

give poor results. A very efficient method to use with

the WWV Time-Code receiver is a dipole antenna

“cut” for the proper frequency of 10 MHz. Half-wave

dipoles are very effective antennas and are simple to

construct. For low-power work or receiver use, you can

use low-cost RG-58 52 ohm coax from the dipole

antenna to your new receiver. The formula for dipole

antennas: 234/(frequency in MHz) = 1⁄4-wavelength in

feet will give the length of wire needed for each leg of

Chapter Ten: WWV 10 MHz “Time-Code” Receiver the dipole. For example, if you wanted to build a Figure 10-6

MHz dipole antenna

114

Chapter Ten: WWV 10 MHz “Time-Code” Receiver

Table 10-4

WWV

Broadcast Format

Station ID

440 Hz 1-hour mark

0

Special

Special

Nist reserved

00

Special

No

55

announcement

announcement

announcement

or

audio

5

Storm

500 Hz tone

500 Hz tone

tone

500 Hz tone

information

sec 45

O N

1 0 0

H

o

Silent except tick

E

z

n

D

S

d

52.5

UTC voice

U

s

O

announcement

50

C

B

10

60

Location

00

E

C

40°40'49.0''N; 105°02'27.0'' W

M

A

I

R

Standard broadcast frequencies

T

R

600 Hz tone

600 Hz

600 Hz tone

tone

and radiated power

I

D

2.5 MHz - 2.5 kW

10 MHz - 10 kW

E

GPS reports

45

C

R

52.5

5 MHz - 2.5 kW

15 MHz - 10 kW

Silent exce

B

45

20 MHz - 2.5 kW

60

15

UTC voicept tick

announceme

UT1 corrections

Omega reports

nt

For additional information contact

Nist Radio Station WWV

Geoalerts

2000 East County Rd. 58

Fort Collins, CO 80524

(303) 484-2372

20

40

Beginning of each hour is identified by

0.8-second-long, 1500-Hz tone.

Beginning of each minute is identified by

0.8-second-long, 1000-Hz tone.

25

The 29th and 59th second pulses of each

35

minute are omitted.

30

440 Hz tone is omitted during first

minutes

Station ID

hour of each day.

There are various tones which can be used to check

information of interest to amateur radio operators, as

audio equipment or musical instruments and they can be

well to as various scientific organizations regarding

captured to detect the start of each hour or each minute.

solar activity, geomagnetic fields, solar flares, and other

At certain intervals, voice announcements are made for

geophysical statistics. This propagation information can

the benefit of other government agencies.

help you decide when the DX will be good.

The predominant ones are as follows:

●

Beginning of each hour is identified by

Marine storm warnings are prepared by the

0.8 second-long, 1500 Hz tone.

National Weather Service and broadcast for areas of the

●

Beginning of each minute is identified by

Atlantic and Pacific Oceans which are of interest to the

0.8 second-long, 1000 Hz tone.

US Government.

Global Positioning System status announcements are

●

The 29th and 59th second pulses of each minute are

prepared by the Coast Guard to give current status

omitted.

information about the GPS satellites.

●

440 Hz tone is omitted during the first hour of

Omega Navigation System reports are prepared by

each day.

the Coast Guard to give the status of the 8 Omega

You will have fun learning about other interesting things

transmitting stations in the 10–l4 kHz frequency range.

on WWV at certain times besides just the time function

These serve as navigation aids.

feature. Features such as accurate tone frequencies,

Geophysical alerts are prepared by the Space

geophysical alerts (solar activity reports), marine storm

Environment Service Center of NOAA. They are

warnings, and global positioning system (GPS) and

broadcast on the 18th minute of the hour and give

Omega navigation system status reports.

115

Chapter 11

VHF Public Service Monitor

(Action-Band) Receiver

Parts list

resistor

[brown-gray-orange]

VHF Public Service

R22

2 ohm, 1/w, 5%

4

Monitor Receiver:

resistor

[red-black-gold]

R1,R2,R3

10k ohm

potentiometer

C1,C6,C22

100 pF, 35 vdc

disk capacitor [marked

R4,R8,R13,R21

47k ohm,

1

100, 101, or 101K]

/w, 5% resistor

4

[yellow-violet-orange]

C2,C5

10 pF, 35 vdc

disk capacitor

R5

470 ohm, 1/w, 5%

4

resistor

C3,C4

56 pF, 35 vdc

[yellow-violet-brown]

disk capacitor

R6,R9,R20

270 ohm, 1/w,

C7,C8,C11,C20

.001 µF,

4

5% resistor

35 vdc disk capacitor

[red-violet-brown]

[.001 or 102 or 1 nF]

R7,R17,R19

10k ohm, 1/w,

C9,C10

15 pF, 35 vdc

4

5% resistor

disk capacitor

[brown-black-orange]

C13,C16,C17,C21

.01 µF,

R10

1 megohm, 1/w, 5%

35 vdc disk capacitor

4

resistor

[marked .01 or 103 or

[brown-black-green]

10 nF]

R11,R12

1k ohm, 1/w, 5%

C12

8.2 pF, 35 vdc disk

4

resistor

capacitor

[brown-black-red]

C14,C32,C33,C35

100 to

R14

33k ohm, 1/w, 5%

220 µF, 35 vdc

4

resistor

electrolytic capacitor

[orange-orange-orange]

C15,C30,C36

4.7 µF, 35

R15

470k ohm, 1/w, 5%

vdc electrolytic

4

resistor

capacitor

[yellow-violet-yellow]

C18

220 pF, 35 vdc disk

R16

100k ohm, 1/w, 5%

capacitor [marked 220

4

resistor

or 221]

[brown-black-yellow]

C19

22 pF, 35 vdc disk

R18

18k ohm, 1/w, 5%

capacitor

4

116

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Eleven: VHF Public Service Monitor

C23,C24,C25

.001 µF, 35

subminiature speaker

vdc disk capacitor

jack

[.001 or 102 or 1 nF]

B1

9 volt transistor

C26,C28,C29,C31

.01 µF,

radio battery

35 vdc disk capacitor

ANT

telescoping antenna

[marked .01 or 103

Misc

PC board, battery

or 10 nF]

holder, battery clip,

C34

.1 µF, 35 vdc disk

speaker, etc.

capacitor [marked .1

Keep an ear on the local action from your easy chair

or 104]

with the VHF Public Service Receiver project, shown in

C27

1.0 µF, 35 vdc

Figure 11-1. The VHF Public Service Radio will allow

electrolytic capacitor

you to tune the VHF high-band Police and Fire band,

L1,L2

2-turn coil 5/32”

marine band, weather band, as well as railroad

OD dia - #24 ga.

frequencies. The receiver tunes any 5 MHz portion of

Insulated magnet wire

the 136 to 175 MHz band. Excellent performance, less

than 1 uV sensitivity. The receiver features: tuned input,

L3

slug-tuned 3 1/ turn

2

low noise pre-amp stage with true dual-conversion

coil, see Table 11-3

superhet design with 2 pole Ceramic High Intermediate

L4

450 kHz shielded

Filter or I-F and 6 pole ceramic low I-F filters! The

quadrature coil, see

receiver also features front panel volume, squelch, and

Table 11-3

tuning controls. This is a great inexpensive receiver to

D1

Varactor diode,

put on your desk at home or to “watch” local radio

BB505 [orange body

activity while you are away from home on vacation or

marked BB505]

business trip.

D2

1N4148 signal diode

Q1

2SC2498 or 2SC2570A

transistor

Circuit description

Q2,Q3,Q4

2N3904

transistor

The heart of the VHF Public Service Receiver shown in

the block diagram of Figure 11-2 is the MC3359

U1

SA602 8-pin IC

U2

MC3359 18-pin FM

receiver IC

U3

LM386 8-pin audio

VHF Public Service Receiver

amplifier IC

Y1

10.24 MHz Crystal

FL1

10.7 MHz ceramic

filter [brown, molded,

3 leads]

FL2

450 kHz ceramic

filter [black, square]

S1

DPDT push switch

J1

PC mount RCA jack

J2

PC mount

Figure 11-1

VHF public service receiver

117

Figure 11-2

VHF monitor receiver block diagram

integrated circuit. The integrated circuit is a complete

is aligned to operate at 10.7 MHz higher than the signal

high gain low power FM IF sub-system which includes

fed and amplified by Q1. For example, to receive

an oscillator, a mixer, a limiting amplifier, AFC,

144-148 MHz signals, the oscillator must tune 154.7 to

quadrature discriminator, op-amp, squelch, scan control

158.7 MHz in order for the SA602’s mixing capability

and mute switch all combined in a single IC. The

to produce a steady 10.7 MHz output signal to the rest

MC3359 was designed to detect narrow-band FM

of the circuit. The oscillator frequency is determined by

signals using a 455 KHz ceramic filter.

L3 and its associated capacitors, and varied by the

varactor tuning network using D1 and varied by R1.

Let’s get into more details of the VHF Public Service

Receiver by examining the schematic diagram shown in

The output from pin 4 of the SA602 passes through a

Figure 11-3. VHF signals from the antenna are

ceramic 10.7 MHz filter, amplified by transistor Q2 and

amplified through the tuned input circuit (L1, C3 and

applied to input pin 18 of U2. Q3 provides AFC

L2, C4) by Q1, a microwave bipolar transistor. Q1’s

(Automatic Frequency Control) by keeping the local

output is fed to the input of the SA602 IC, an efficient

oscillator of U1 from drifting away from an incoming

single-package (8-pin DIP) mixer-product detector-

signal. This is accomplished by tuning the varactor

Chapter Eleven: VHF Public Service Monitor oscillator. The tuneable oscillator section of the SA602

circuit in the direction opposite the drift.

118

119

Figure 11-3

VHF public service block diagram

r

o

t

i

n

o

M

e

c

i

v

r

e

S

c

i

l

b

u

P

F

H

V

:

n

e

v

e

l

E

r

e

t

p

a

h

C

The MC3359 IC has an internal oscillator controlled

both the component lead wire and PC board trace

by the 10.24 MHz crystal. The 10.24 MHz signal is

enough so that the wire itself AND the foil trace BOTH

mixed with the 10.7 MHz input from U1 to convert

become hot enough TOGETHER to melt a bit of solder

down to the low IF of 450 kHz. The 450 kHz IF is

so that it flows smoothly from the pin to the PC board

filtered by FL2 and then amplified by a limiting

trace. Locate the printed circuit board and all the

amplifier in U2. Audio demodulation takes place in the

components and we will start.

quadrature detector, with L4 adjusting the detector. The

audio modulation is detected in U2, and the background

Locate all of the resistors for the project and place

noise is used to control the squelch. U3 amplifies the

them in front of you. Each resistor has a color code

audio output from pin 10 of U2 to a practical level for

which describes its value. The first color band at one

speaker or headphone operation. Pin 16 of U2 will

edge of the resistor body represents the resistor’s first

ground the input of U3 when the squelch is closed. L4,

digit value, while the second color band denotes the

a 450 kHz IF coil, permits adjustment of the 90 °

second digit of the resistor value. The third color band

voltage-current phasing (“quadrature”) of FL2’s output

represents the multiplier value of the resistor. A fourth

to the FM detector demodulator (pin 8 of the MC3359).

color band is the tolerance value. A silver band denotes

a 10% tolerance, while a gold band denotes a 5%

tolerance. The absence of a fourth color band denotes a

20% tolerance value. Check the color code against the

Circuit assembly

parts list and schematic before installing them onto the

circuit board. Refer to the resistor color chart in

Look for a clean well lit area in which to assembly your

Table 11-1. Place about four or five resistors on the PC

shortwave receiver. You will need a 27 to 30 watt pencil

board and place these resistors in their respective

tip soldering iron, some 60/40 tin/lead rosin core solder,

locations carefully making sure each one is in the

a few hand tools, including a pair of end-cutters, a

correct location. Next, solder each of the resistors onto

needle nose pliers, a few screwdrivers and a pair of

the circuit board. Trim off the excess component leads

tweezers to pick up small parts. Locate your schematic

with a small pair of end-cutters. Pick up and identify the

and layout diagrams and we will begin to construct your

next grouping of resistors and install them on the circuit

new shortwave receiver. Let your soldering iron tip heat

board, follow up by soldering this next batch of resistors

Table 11-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Eleven: VHF Public Service Monitor

No color

20%

120

Chapter Eleven: VHF Public Service Monitor

to the circuit board; remember to trim the extra lead

the excess component leads from the PC board after

lengths form the PC board.

soldering.

Once all the resistors have been installed onto the

Next we will move to installing the two diodes.

circuit board, we can move on to identifying all of the

Diode D1 is the varactor “tuning” diode while D2 is a

capacitors for the project. Note that there will be

1N4148 silicon diode. When mounting the diodes be

different looking capacitors for this project, some will

careful to observe polarity markings on the diodes.

be small disks, while others will be larger body devices

Usually each diode will have a black or white band at

with minus and plus marking on them. These larger

one end of the diode body. This color band denotes the

capacitors with polarity marking are electrolytic

cathode end of the diode. Refer to the schematic

capacitors and they have polarity which must be

diagram and layout diagrams in order to see how the

observed for the circuit to work correctly. Look through

diodes should be mounted with respect to polarity

the parts pile and locate the capacitors and place them

considerations.

in front of you. You will notice a number of small disk

Before we go ahead and install the semiconductors,

capacitors, we will install these first. Look closely at

take a look at the semiconductor pin-out diagram in

each of the disk capacitors at their markings. Sometimes

Figure 11-4 which will help you orient the components.

the capacitors are very small and they may not have

Now locate the transistors from the components.

their actual value printed on them but will instead have

Transistor Q1 is a 2SC2498 or 2SC2507A, while

some sort of code marked on them. Refer to the parts

transistors Q2, Q3 and Q4 are 2N3904 NPN types.

list for these codes or the capacitor code chart in

Transistors have three leads, a Base lead, a Collector

Table 11-2. Locate four or five of these small disk

lead and an Emitter lead. The symbol for the Base is a

capacitors, identify them and install them on the circuit

vertical line, while the Collector and Emitter are slanted

board, while referring to the schematic and layout

lines pointing to the Base lead. The Emitter lead is

diagrams. After inserting the disk capacitors onto the

shown with a small arrow pointing towards or away

circuit board, you can go ahead and solder them to the

from the Base lead. Refer to the schematic and layout

circuit board. Remember to cut the excess component

diagrams to determine the orientation of the transistors.

leads. Next, move on and install another grouping of

Clearly identify Q1, the 2SC2498 or 2SC2570A

small disk capacitors, then solder them in place on the

transistor. Do not confuse it with the other transistors

printed circuit board. Cut the extra component leads

supplied. Position Q1 as shown on the PC board layout,

after soldering in the capacitors. When you are finished

with the flat side facing to the right, toward the middle

installing the small capacitors we will move on to the

of the board. Press the transistor snugly into the PC

larger electrolytic types.

board so that only a minimum amount of wire lead is

exposed above the board. In soldering, don’t be afraid to

Capacitors C14, C32, C33 and C35 are all 100 uF to

use enough heat to make good clean connections.

200 µF electrolytic types. These capacitors will have

either a plus or minus marking and/or black band

Once the transistors are in place on the PC board,

denoting polarity. You must orient these capacitors with

you can go ahead and solder them to the foil side of the

respect to their polarity markings. Check both the layout

PC board. Don’t forget to trim the extra component

diagram and the schematic diagram for polarity

leads.

references. Note also that capacitors C15, C30 and C36

Now we are going to install FL1, the ceramic filter.

are also electrolytic capacitors with a 4.7 µF value.

This component looks like a capacitor with three leads

These too must be oriented correctly for the circuit to

and may be installed either way. Next go ahead and

operate correctly when power is applied. It is possible

locate FL2, the 450 kHz filter. Its three leads are

to actually damage the circuit upon power-up if these

delicate and fit in only one way. At this time you can

capacitors have been installed incorrectly, so pay careful

locate Y1, the 10.24 MHz crystal. No special procedure

attention when mounting these capacitors. Install the

is required. Simply press the crystal firmly into its holes

electrolytic capacitors in groups of two or three. Once

as far as it will go. Now go ahead and solder in the

they have been placed on the circuit board, you can

crystal and ceramic filters, remove the excess

move on to soldering them in place. Remember to trim

leads if any.

121

Table 11-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Eleven: VHF Public Service Monitor 820pF

Ceramic

821

2

Mylar

205

122

Chapter Eleven: VHF Public Service Monitor

1

8

1

8

1

8

2

7

10

9

3

6

4

5

MC3359

EBC

EBC

EBC

SA602

EBC

1

8

1

8

2

7

3

6

2N3904

2N3904

2SC2498

4

5

2N3904

LM386

Figure 11-4

Semiconductor pin-outs

Look through the remaining components and locate

please be aware that we have seen more service

the inductors L1 through L4. Coils L1 and L2 are small

problems with improper socket insertion than from

1 and 1⁄2 turn coils. Go ahead and install coils L1 and L2,

soldering heat damage to ICs. Even if this is your first

they are both the same. Now, locate and install L3, the

IC, don’t be afraid to use enough heat to make eight

slug tuned coil. It is important that the body of this coil

clean connections, but DO be sure to correctly orient

be snug against the PC board for mechanical stability,

the end marked by a band, dot, or notch. Before

which directly affects the frequency stability of the

soldering, make sure that the IC or socket is perfectly

receiver. Make good, solid solder connections, when

flat against the top of the PC board. Install U1, the

installing the above coils. Finally locate coil L4, the

SA602, in accord with the preceding directions.

455 kHz quadrature coil, soldering the two pins and the

Now, install MC3359 IC, U2. As in the case of the

two mounting tabs. Remove any excess lead lengths if

SA602 IC, you could choose to install an 18-pin IC

any; see Table 11-3 for coil winding information.

socket rather than soldering the IC directly. Re-read the

Let’s move on to installing the SA602 IC, you may

discussion of IC sockets offered for the installation

wish to use an 8-pin DIP socket rather than soldering

of U1. Larger ICs such as the MC3359 require

the IC directly to the board. Reasons for doing this

considerably more care in socket insertion. Notice that

might include the peace of mind of beginners afraid of

the end of the IC marked by a band, dot, or notch must

damaging the IC, or experienced builders testing the

be oriented correctly as shown on the parts layout

merits of the SA602’s cousin, the SE602. However,

diagram. Solder each of the 18 connections carefully.

Table 11-3

Coil winding information

L1,L2

2-turn coil - #24 ga. Insulated magnet wire - 5/32′′ OD dia.

Air-core coil.

L3

3 1⁄2 turn coil ferrite slug-tuned coil, unwind original coil from form and rewind 31⁄2 turns of #24 ga. insulated magnet wire on form - use series 49A coil

Circuit Specialists (49A127MPC).

L4

450 kHz shielded quadrature coil

TOKO America Coils (7MC-81282).

123

Make sure you have good lighting as well as good

solder joints, touching up any connection which appears

technique to make sure that no solder “bridges” flow

less than perfect. Make sure all excess leads have been

between the connections.

trimmed, and that one is not bent back flat against the

Finally locate and install U3, the LM386 IC audio

board, possibly causing a short. Brush the solder side of

amplifier integrated circuit. Once again use of an IC

the board with a stiff brush to make sure that no loose

socket is highly recommended. Solder the IC socket to

wire trimmings or solder drippings are lodged between

the PC board and insert the LM386 paying particular

connections. Connect up a suitable antenna and connect

attention to the small notch or indented circle on the top

up the 9 volt battery to the receiver and you are ready to

of the IC body. Pin 1 is to the left of the notch,

try out the receiver for the first time.

cut-out or indented circle.

After power is first applied and you have connected

up your antenna, you will need to adjust the gain

Take a short well-deserved break and when we return,

control to midrange. Next, you should adjust the

we will install the remaining components on the PC

squelch control just below the threshold point, so that

board and finish up building the receiver. Now locate

you can hear the normal background hiss. Now begin

power switch S1. Press S1 firmly into its six holes and

turning the tuning control and you should soon come

solder all six pins. The switch fits the board only one

across a public service transmission from a local police

way. Next, install J1, the RCA-style antenna jack and

or fire broadcast.

solder all four points. Now, install J2, the subminiature

headphone jack. Solder all three points. Be gentle

In the event that you do not hear any hiss coming

and patient in inserting, so as not to damage the

from the speaker or headphones, or you do not hear any

solder tabs.

stations after about 20 to 30 minutes, then you may have

to troubleshoot the receiver for any errors that may have

Locate all three potentiometers and we will install

occurred during the building process. First, disconnect

them now. Potentiometer controls R1, R2 and R3 are all

the battery and antenna and un-mount the receiver

mounted in a row next to switch S1. Insert the three PC

circuit board from the enclosure. Have a friend assist

mount potentiometers into their positions. Check that

you in inspecting the circuit board; a different set of

the controls are pressed in firmly and straight against

eyeballs can often help to find errors quickly.

the top of the board. Solder the three center pins and

then the two larger mechanical mounting tabs. Use

The most common causes for circuit failure are

enough solder for a solid connection.

resistors placed in the wrong locations, the second

possible cause for errors are improper installation of

The circuit board may require a few jumpers;

diodes and electrolytic capacitors. Make sure that you

“cut” component leads make good jumpers. Insert the

re-check the orientation of these components one more

jumpers and solder into place, remember to trim the

time and refer to the schematic, and parts layout

excess leads. We are now down to the home-stretch.

diagrams. Another possible cause for mistake is the

Install the battery snap terminal in the two holes below

improper installation of transistors and integrated

S1, making sure that the positive (red) lead is inserted

circuits. Be sure to recheck the orientation of

into the (+) hole on the PC board.

transistors. Each transistor has three leads, an Emitter, a

Finally, go ahead and mount the battery bracket, it

Collector and a Base lead. Closely inspect and compare

may be attached in a variety of ways. A wire jumper can

the schematic diagram along with the parts layout

be passed through the two holes on the PC board, then

diagram and manufacturer’s specifications sheets to

both ends soldered on the underside of the board. You

ensure that you have oriented the transistors correctly.

may prefer to use very small screws or even a double-

Lastly, integrated circuits are often placed backwards in

sided mounting adhesive strip or glue. In using such

their sockets. After you have checked all the above tips,

methods, make sure that the battery will not block the

make sure that the battery is connected correctly with

PC board’s mounting hole in its vicinity.

the black battery or minus lead (−) connected to the

Wiring of the PC board is now complete. If you have

circuit ground and the plus (+) or red battery lead

the patience, we suggest a short break. Then take a

connected to the power input regulator of the circuit.

Chapter Eleven: VHF Public Service Monitor magnifying lens and a bright light and examine all your Reconnect the battery and the antenna and then switch

124

Chapter Eleven: VHF Public Service Monitor

the receiver to the “On” position and retest the receiver

Now, you can turn the power switch to “On.” Now turn

once again to make sure that it is now working.

R2 (volume control) until you hear some noise. Finally,

adjust L4 for maximum noise from the speaker.

Further alignment now consists of adjusting the

Testing, alignment

oscillator coil L3 to permit the tuning control (R1) to

cover the 5 MHz segment between 135 and 175 MHz of

and adjustment

primary interest to you. Assuming you wish to adjust

for the 2-meter 144–148 MHz Amateur Band, adjust L3

In order to prepare the VHF FM Receiver for reliable

until you hear your intended test signal. If you are a

monitoring operation, you will need a few basic tools,

beginner with no license or other equipment, any ham

such as useful VHF signal source, a hexagonal, non-

operator with a 2-meter transceiver should be willing to

metallic coil slug alignment tool for L3, and a small

give you the test signal and extra help that you need.

screwdriver to adjust L4. To align your new receiver,

Your new VHF receiver is very sensitive, so operate the

you will need to locate some sort of a signal source.

transceiver on low power on a simplex frequency from a

This signal can be from your test bench equipment or

distance of at least across the room. An 8′′ piece of wire

from a “live” source such as a local repeater. The “live”

will be a sufficient receiving antenna for such tests. If

signals are best for fine-tuning, but they also have that

you don’t know any hams, visit a friendly two-way radio

VHF communications character of being fast and to the

service center to get close to the test signal you need!

point. Good test bench signal sources include your own

2-meter transceiver, if you are licensed to use it, a signal

generator or grid-dip oscillator. If you do not have a

Receiver sensitivity

steady test signal source for the band within

135–175 MHz of primary interest to you, and still wish

to verify immediately the proper operation of your

Your FM receiver features sensitivity under 1 uv.

receiver, a good and steady VHF signal source will be

Radio hams constantly marvel at how an FR146 displayed

your local NOAA Weather Service station, broadcasting

at hamfests tunes in dozens of hand-held QSOs on the

around 160 MHz. Once you have verified reliable

premises without an antenna connected! You can expect to

reception of your regional NOAA station, adjustment to

monitor local repeater and simplex transmissions easily,

your desired listening range will become easier.

using a simple ground-plane style antenna.

If you do not already have a set of plastic or nylon coil

alignment tools and do expect to try further ham radio or

electronic hobby projects, such tools are worth having

Customization

and can be found inexpensively at any electronics store

including Radio Shack. While a metal hex key wrench

For many people, a pilot lamp to indicate “power on” is

can fit the coil slug, the metal itself would damage the

more than a nice touch. They expect it and depend on it.

coil inductance drastically and therefore should not be

Adding a simple LED power-on indicator to your VHF

used. With patience and sandpaper, a useable tool might

receiver is easy. All you need is the LED itself and a

be formed from a wood or plastic rod.

small 1k to 2.2k resistor. Study the PC traces between

The alignment procedure should begin as follows:

the positive battery supply wire and the on-off switch.

first make sure the power switch is off. Next, connect

The unused connectors on top of your switch are an

the antenna, earphone or speaker and battery, then turn

ideal point to get the + DC voltage needed for the anode

the slug of L3 until it is even with the top of the coil

(longer lead) of the LED. Plan where and how you wish

form. Then turn the slug of L3 clockwise seven turns

to install the LED in your enclosure.

back into the form.

Locating the LED immediately above the on-off

Now, turn the slug of L4 until it is flush with the top of

switch is logical and ideal. The simplest way to make a

the coil and then turn it two turns back into the coil. Next

good installation is to drill a neat hole just slightly

turn all three controls to the left, fully counterclockwise.

smaller than the diameter of the LED. Then, enlarge the

125

hole a little bit at a time just enough to let the LED be

stations which are further away than just the local

pressed in and held firmly. The resistor may be

stations, you may want to install some sort of an

connected to either the anode or cathode of the LED,

outdoor antenna such a ground plane or Discone

but the anode MUST go to + DC, with the cathode

antenna for VHF operation. Since most of the

connected to the nearest common ground point.

transmissions in this band are of vertical polarization,

vertical antennas, ground plane and Discone

antennas will work best in this band. Various VHF

scanner type antennas from your local Radio Shack

Antenna considerations

store will work fine. The chart illustrated in Table 11-4

shows the utilization of the VHF Public Service band.

For local VHF reception, the VHF receiver will operate

Have fun and enjoy you new VHF “action” band

fine just using a whip antenna. If you wish to receive

receiver.

Table 11-4

VHF high-band frequency band utilization

150.995 MHz to 151.130 MHz

Highway maintenance

151.145 MHz to 151.475 MHz

Forestry conservation

152.030 MHz to 152.240 MHz

Mobile telephone

152.270 MHz to 152.450 MHz

Taxi services

152.510 MHz to 152.810 MHz

Mobile telephone

153.410 MHz to 154.115 MHz

Utilities/light/power/water and local gov’t

153.830/153.890/154.010/154.070 MHz

Fire

154.130 MHz to 154.445 MHz

Fire

154.650 MHz to 155.700 MHz

State & Local police

155.715 MHz to 156.255 MHz

Local Gov’t / police/ highway maintenance

156.275 MHz to 157.425 MHz

Marine Frequencies

157.530 MHz to 158.265 MHz

Taxi & Mobile telephones

158.280 MHz to 158.460 MHz

Utilities water/power/industrial

158.730 MHz to 159.210 MHz

Highway Maintenance & police

159.225 MHz to 159.465 MHz

Forestry

159.495 MHz to 160.200 MHz

Motor carrier trucks

160.215 MHz to 161.565 MHz

Railroad

161.640 MHz to 161.760 MHz

Broadcast pickups & Studio to Xmiter Links

161.800 MHz to 162.00 MHz

Maritime Shore Stations

162.400 MHz to 162.550 MHz

NOAA weather broadcasts

162.250 MHz to 173.500 MHz

Gov’t sonobuoys

169.00 MHz to 172.000 MHz

Low power wireless mikes

173.2037 MHz to 173.396 MHz

Fixed/mobile industrial & remote control

173.400 MHz to 173.5000 MHz

Remote control & telemetry

Chapter Eleven: VHF Public Service Monitor

126

Chapter 12

6 & 2-Meter Dual-Band

Amateur Radio Receiver

C5

3.9 pF, 50v disk

Parts list

capacitor

C6

33 pF, 50v, 10% disk

6N2 Meter Amateur Radio

capacitor

Receiver

C7

470 pF, 50v, 10%

R1

68 k, 1/w,

4

50 v disk

5% resistor

C8

7 pF, 25v, 20% disk

R2

47 k, 1/w,

4

capacitor

5% resistor

C10

1000 pF, 50v,

R3, R7

3.3k, 1/w,

4

10% disk capacitor

5% resistor

(102)

R5

20 k 5% 1/W

4

C11,C13,C16

.01 µF,

R8

8.2k, 5% 1/W

50 v, +80, –20%

4

R9

Jumper wire (use a

capacitor (103)

discarded resistor

C17

51 pF, 25v, 10%

lead)

capacitor (51K)

R10, R12

1k, 1/w,

C12

68 pF, 25v, 10%

4

5% resistor

capacitor (68K)

R11

10 k, 1/w,

C14, C21

4.7 µF, 50v

4

5% resistor

Radial capacitor

R15

10 ohm, 1/w,

C15

220 µF, 16v Radial

4

5% resistor

capacitor

VR1, VR3

100 k

C18,C19,C20

.1 µF, 50v,

potentiometer

+80, –20% capacitor

(chassis mount)

(104)

VR2

5k, 20% linear

C22

.047 µF, 50v,

potentiometer (chassis

+80, –20% capacitor

mount)

(473)

C1

120 pF, 25v

D1, D2 Diode

1N914

capacitor (121)

silicon diode

C2

.005 µF, 35v 20%

U1

IC MC3362P FM

capacitor (502)

Receiver IC

C3,C4,C9

.1 µF +80, –20%

U2

IC LM386N-1 Audio

50v capacitor (104)

Amp IC

127

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

U3

IC 78L05 Regulator

glimpse of the active world of VHF amateur radio. This

+5v 78L05

receiver combines both the 2-meter and the 6-meter

L1

Coil (4.5 turns

bands which are popular with radio enthusiasts around

coated wire- #24 ga.)

the country. The 2-meter band is probably the most

-air-core

active ham radio band especially for newcomers with a

technician class license. Two-meter band coverage is

L2, L3

Coil (on form

usually quite good in most parts of the country. The

with core)

2-meter band features many ham radio repeaters, and in

L4

Coil (1.5 turns

some have wide-area long-range repeaters in most US

coated wire- #24 ga.)

states and in many Canadian provinces. These ham

-air-core

radio repeaters allow amateur radio operators to

L5

.64 mH Coil (yellow)

communicate over long distances. The 6-meter band has

I-F Transformer

often been called the “magic band.” This amateur band

(42IF301)

is usually only used for fairly local coverage but when

the band is “open” you can often hear hams on the

F1

455 kHz Ceramic

opposite side of the US or in Cuba or the Caribbean,

Filter

which is really exciting!

F2

10.7 MHz Ceramic

You can listen-in to these exciting two ham radio

Filter

bands and hear all the action, day or night with the 6N2

Y1

10.245 MHz Crystal

portable receiver. You may just decide the action sounds

SW1, SW2

Switch Slide

like something you would like to be part of, and you

DPDT

can easily get your own ham radio “ticket” or license.

B1

9 volt transistor

Contact the Amateur Radio Relay League (ARRL) at

radio battery

http://www.arrl.org; they have many books, publications as well as introductory videos. They are a great resource

SPKR

8 ohm speaker

in locating local ham radio clubs, where you can make

J1

RCA jack - antenna

friends and learn a lot about ham radio and

Misc

PC Board, battery

communication.

2-Meter Dual-Band Amateur Radio

holder, battery clip,

The 6N2 radio is known as a narrow band FM VHF

The 6N2 receiver is a dual conversion, dual band

receiver. FM of course is a type of modulation

& amateur radio receiver; it combines the excitement of and is denoted as Frequency Modulation. Frequency

two very active amateur radio bands in one small

modulation means the data or voice changes the

receiver, see Figure 12-1. The 6N2 receiver will allow

frequency of the radio wave. The other popular

radio enthusiasts, both the young and old, to get a

forms of modulation are AM (Amplitude Modulation)

and PM (Phase Modulation). We also mentioned

narrow band, which notes that the selectivity of the

entire system is limited to only enough frequencies to

pass voice or low frequency data. A commercial

broadcast FM receiver would have a bandwidth large

enough to pass music and high frequency data

transmissions.

The 6N2 receiver is a dual conversion, two-band

radio receiver. In a dual conversion receiver, the original

radio frequency is converted first to a 10.7 MHz

intermediate frequency (I-F) and amplified in (Block 4).

The 10.7 MHz signal is then converted to 455 kHz and

Chapter Twelve: 6 Figure 12-1 6N2 meter amateur radio receiver amplified in (Block 3). Noise is removed and the

128

Chapter Twelve: 6

Antenna

Convert to

Convert to

Remove noise

Audio

10.7 MHz

455 kHz

and demodulate

amplify

and amplify

and amplify

Block 4

Block 3

Block 2

Block 1

Speaker

Figure 12-2

6⁄2 meter amateur radio receiver block diagram

modulated signal is recovered from the 455 kHz I-F

provides the selectivity to filter out the desired narrow

signal in (Block 2). The audio signal is amplified to

band transmission.

drive a speaker in (Block 1), see Figure 12-2. The 6N2

The 6N2 receiver operates on two of the most

receiver specifications are illustrated in Table 12-1.

&

popular VHF amateur radio bands. The 6N2 VHF

So you ask, why dual conversion? To answer this

amateur radio receiver receives both the 6-meter ham

2-Meter Dual-Band Amateur Radio

question, take a look at the diagram shown in

band and the 2-meter ham bands, and you can select the

Figure 12-3, and it may become more clear. In order to

band with a band-switch.

obtain the desired intermediate frequency (I-F) signal by

mixing the local oscillator with the desired radio

To help you visualize the relationship between

frequency, an unwanted output may result due to a

frequency and wavelength, take a look at the diagram

transmission spaced one intermediate frequency or (I-F)

shown in Figure 12-4. If the speed of a wave (meters

on the opposite side of the oscillator (image). By using

per second) is divided by the number of waves that pass

a large I-F frequency, this image is moved further out of

a given point (cycles per second), the seconds cancel

the band of desired frequencies. The second conversion

and you obtain the wavelength λ = meters per cycle.

The speed of radio waves is approximately 300,000,000

meters per second. If the frequency is 50 to 54 MHz,

the wavelength becomes 300,000,000/50,000,000 or

6 meters. So for the 2-meter band, which is

approximately 150 MHz, the wavelength becomes

Table 12-1

300,000,000/150,000,000 or 2 meters. The actual

The 6N2 amateur radio specifications

bands are: 2-meter band which covers 144 MHz to

2-meter band covers 144 MHz to 148 MHz

148 MHz, and the 6-meter band which covers 50 MHz

to 54 MHz.

6-meter band covers 50 MHz to 54 MHz

● Single supply voltage (4-12 v)

The 6N2 dual band VHF receiver is composed

● Idle current - 4 milliamps

of four major blocks, i.e. blocks 1 through 4. It is

● Inputs referenced to ground

a bit easier to follow how the receiver works if we

● Input resistance - 50 k

break it down into smaller defined blocks, see

● Self-centering output voltage

Figure 12-5. The heart of the receiver is the

integrated circuit at U1, an almost complete FM

● Total harmonic distortion less than 0.2%

receiver on-a-chip. The FM receiver chip only

● Output power with 9 volt supply voltage

requires timing components, a crystal and RF tuning

● Voltage gain with 10 µF from pin 1 to 8 - 200 or 46 dB

components, a filter. The output of the FM radio

● Voltage gain with pins 1 and 8 open - 20 or 26 dB

chip is sent to the audio amplifier chip at U2. Power for

● Bandwidth with pins 1 and 8 open - 300 kHz

the receiver is regulated via the regulator chip at U3.

129

Desired band

of frequencies

Local oscillator

Desired frequency

Image frequency

Single conversion with 455 kHz IF frequency

vs.

Second conversion

Desired band

to 455 kHz

of frequencies

Crystal oscillator

Desired

Local oscillator

at 10.245 MHz

frequency

Image frequency

10.7 MHz

10.7

MHz

Double conversion puts the image outside the desired band

and still allows narrow band output

Figure 12-3

Single vs. double conversion receiver

The receiver is relatively straightforward and can

therefore be constructed in stages, one through four.

The audio amplifier –

We will begin with Stage 1, which can be built and

tested separately. You can progress step by step and

block 1

build and test each stage before moving on to the next

stage. Let’s begin with Block 1, the audio amplifier

The audio section in this receiver is amplified by using

2-Meter Dual-Band Amateur Radio stage.

an integrated circuit audio power amplifier. The output

&

vs.

Frequency modulation

Amplitude modulation

2 meters

6 meters

50 MHz

144 MHz

2-meter band covers 144 to 148 MHz

6-meter band covers 50 to 54 MHz

Chapter Twelve: 6 Figure 12-4 Frequency coverage diagram 130

Antenna

R10

2 m

6 m

C8

C12

C9

L1

L2

VCC

VR2

C7

C10

R7

C16

C11

S2A

R9

2 m

6 m

D1

C13

R6

R4

D2

1

24

2

23

U1

S2B

VCC

C1

3

22

C5

L3

C17

4

21

9V DC

Y1

5

20

C6

L4

+

R3

6

19

F1

7

18

S1

F2

VCC

8

17

0

1

C19

U3

+

C18

9

16

C14

C4

C21

C20

10

15

C3

R11

11

14

6

3

C15

Speaker

R1

12

R8

VR3

13

+

5

+

+

U2

–

2

4

R15

R2

L5

C2

C22

131

VR1

Figure 12-5

VHF public service receiver schematic. Courtesy of Elenco Electronics 2-Meter Dual-Band Amateur Radio

&

6

:

e

v

l

e

w

T

r

e

t

p

a

h

C

impedance of the amplifier is low enough to drive an

unwanted amplitude variations in the received signal,

8 ohm speaker directly. The coupling capacitor value is

but minor frequency variations. Noise immunity is one

picked to pass audio signals down to 100 cycles by

of the great advantages of frequency modulation over

matching the reactance of the capacitor with the speaker

amplitude modulation. The remaining signal contains

impedance.

only the frequency modulation.

Due to the high input resistance of the amplifier

The 6N2 receiver uses a quadrature detector to

(50 k), the audio coupling capacitor C3 can be as

demodulate the FM signal. After the noise is

small as 0.1 µF. The equivalent resistance at the

removed by the limiter, the signal is internally

junction of R8 and VR3 is approximately 6.6 k (the

connected to the quadrature detector. A parallel

parallel combination of R8, VR3 and the 50 k input

tuned circuit must be connected from pin 12 to the

impedance of the LM-386). The capacitor C2 and this

power supply. This circuit produces the 90° phase

equivalent resistance sets the 3 dB corner used to

needed by the quadrature detector. A resistor shunting

attenuate any IF voltage at pin 13. A simple RC

this coil sets the peak separation of the detector. If the

filter attenuates at a rate of 6 dB per octave (an octave is

value of the resistor is lowered, it will increase the

the same as doubling the frequency). By using 6.6 k as

linearity, but decrease the amplitude of the recovered

the equivalent resistance and 0.005 µF as the

audio.

capacitance, we get a 3 dB corner at approximately

The quadrature detector combines two phases of the

4.8 kHz. To get to 455 kHz, you must double

I-F signal that are 90° apart, or in quadrature, to recover

4.8 kHz approximately 6.6 times. This equates to a

the modulation. The shifted signal is used to gate the

reduction of the IF voltage at the R8 - VR3 junction

non-shifted signal in a synchronous detector. When the

of 39.6 dB (6 dB per octave times 6.6 octaves), or

frequency increases above the carrier frequency

95 times.

(positive deviation), the phase shift increases causing a

decrease in the width of the gated impulse output. In a

similar manner, when negative deviation occurs, the

Recovering the

gated impulse output will widen. The gated output is

then filtered to remove the pulses and recover the

data – block 2

modulating signal.

2-Meter Dual-Band Amateur Radio In working with FM receivers, there are some terms that

& need to be defined. First, let’s determine the term

455 kHz conversion –

deviation as the frequency swing of the incoming

FM signal. When no modulation is present, the

blocks 3 & 4

incoming signal is a fixed frequency carrier wave (Fc).

Positive deviation (Fp) is the increase in Fc due to

The first local oscillator should be set at 133.3 MHz to

modulation, and negative deviation (Fn) is the decrease

137.3 MHz for the 2-meter band and 39.3 MHz to

in Fc due to the modulation. The detector must be linear

43.3 MHz for the 6-meter band. This oscillator is free-

over the maximum total deviation (Fp max. - Fn max.)

running varactor-tuned. The first mixer converts the RF

produced by the transmitter or distortion will occur.

input to an I-F frequency of 10.7 MHz. This I-F signal is

Before the second I-F signal reaches the detector, it is

then filtered through a ceramic filter and fed into the

applied to a limiting amplifier inside the integrated

second mixer. If the oscillator of the second mixer is

circuit. A limiting amplifier is designed to remove any

precisely set at 10.245 MHz, it will produce an output

amplitude variations in the signal by amplifying the

containing the sum (20.945 MHz) and the difference

signal well beyond the limit of the amplifier. The

(0.455 MHz or 455 kHz) frequencies. This 455 kHz

frequency variations (FM) are not affected by the

signal is then sent to the limiter, detector, and audio

limiter. The limiter removes the affects of fading

circuits. The mixers are doubly balanced to reduce

(driving through a tunnel) and impulse noise (lightning

spurious (unwanted) responses. The first and second

Chapter Twelve: 6 and ignition). These affects produce significant mixers have conversion gains of 18 to 22 dB respectively.

132

Chapter Twelve: 6

Conversion gain is the increase in a signal after the

project with integrated circuits it is wise to consider

signal has been converted to a new frequency and

installing integrated circuit sockets on the PC board, as

amplified. For both converters, the mixers are designed

a form of insurance in the event of a possible circuit

to allow the use of pre-tuned ceramic filters. After the

failure somewhere down the road. It is much more easy

first mixer, a 10.7 MHz ceramic bypass filter is used.

to simply unplug a damaged IC and simply replace it by

This eliminates the need for special test equipment for

plugging in a new one.

aligning I-F circuits. The ceramic filter also has a better

Before we get some momentum on the project, you

aging and temperature characteristic than conventional

may also want to refer to the chart in Table 12-2.

LC tuned circuits.

This table lists the color codes for the resistors, and will

greatly aide you in constructing the receiver. Go ahead

and locate resistor R1, a 68 k resistor, its color code is

Assembling the 6N2

(blue-gray-orange). Now locate resistor R2, a 47 k ohm

resistor with (yellow-violet-orange) color code. Place

receiver

these resistors on the circuit board in their respective

locations and solder them in place. Now you can

Before constructing your new 6N2 receiver, you will

identify the remaining resistors and place them on the

need to locate a clean well lit, well ventilated work

circuit board and solder them in their proper locations.

space. Locate a small pencil tipped 27 to 33 watt

&

Use your end-cutters to trim the excess component

soldering iron. You should also locate a spool of 22 ga.

leads. Cut the extra component leads flush to the edge

2-Meter Dual-Band Amateur Radio

rosin core solder, a small container of “Tip Tinner”

of the circuit board.

from your local Radio Shack store. “Tip Tinner” helps

to clean and dress the soldering iron tip. Place the

Now locate and install capacitors; first locate and

schematics and parts layout diagram in front of you

identify capacitors C1 and C2. Capacitor C1 is a small

along with all of the project components. A few small

disk capacitor marked (121) or120 pF. Small capacitors

tools would be helpful to constructing your project, so

often do not have their actual values printed on them but

find a small pair of end-cutters, a pair of tweezers, a

use a three-digit code to represent their value. Refer to

magnifying glass, a small Phillips and flat-blade

the chart in Table 12-3 to help you identify the small

screwdrivers, and we can begin. When building a

capacitors. Now look for capacitor C2, its value

Table 12-2

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

133

Table 12-3

Capacitance code information

This table is designed to provide the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules.

Some capacitors actually have the numeric values stamped on them; however, some are color coded and some have alphanumeric codes. The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

2-Meter Dual-Band Amateur Radio 47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

& 56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Twelve: 6 820 pF

Ceramic

821

2

Mylar

205

134

Chapter Twelve: 6

is .005 µF, but may be marked (502). Go ahead and

the PC board, and coil L4, a 11⁄2 turn air-wound coil, will

install these capacitors in their respective locations on

be mounted at the bottom center of the board. Coils

the circuit board. Remember to trim the excess

L2 and L3 are 9 turn coils wound on a coil form with a

component lead lengths with your end-cutters. Next,

ferrite tunable slug in the center of the form. Coil L5 is a

locate the remaining small capacitors and install them

0.64 mH coil in a small metal can with five leads. Coil

on the circuit board.

L5 is a tunable slug tuned coil with a yellow ferrite core,

Next, we are going to locate and install the

see Table 12-4 for coil winding details.

electrolytic capacitors. Electrolytic capacitors are

The 6N2 receiver utilizes three integrated circuits.

generally larger in size and higher in value than the

Before we go ahead and install the integrated circuits,

small value capacitors and usually they are vertical or

let’s take a brief look at the semiconductor pin-out

horizontally mounted. Remember, electrolytic

diagram shown in Figure 12-6. The main receiver chip

capacitors have polarity and must be installed with

U1 is the Motorola MC3362, a 24 pin dual conversion

respect to this polarity if the circuit is going to work

FM receiver on-a-chip which contains oscillators,

properly. The capacitor’s value will be printed on the

mixers, quadrature discriminator, and meter drive/carrier

body of the capacitor along with a white or black

detect circuitry all in one chip. The audio amplifier at

polarity marking, either a plus or minus marking.

U2 is an LM386 chip, while U3 is 5 volt regulator, an

Pay attention to this plus or minus marking and

LM78L05. When installing the integrated circuits, you

&

align it with the proper holes on the PC board, you

will need to identify the pin-outs of each of the

will have to refer to the schematic and or parts

integrated circuits. It is advisable to install IC sockets

2-Meter Dual-Band Amateur Radio

layout diagram when placing the electrolytic

prior to installing the ICs on the circuit board, to avoid the

capacitors. Locate and install the remaining

rare event of circuit failure at a late date. It is much easier

electrolytic capacitors onto the circuit board.

to simply unplug an IC and insert another without

Remember to trim the excess electrolytic

un-soldering a 24 pin chip from the circuit board.

capacitor leads after they are soldered in place.

Integrated circuits will generally have a small cut-out at

In this project there are two silicon diodes. Diodes

one end of the IC package or a small indented circle at

are generally rectangular in shape like a resistor but

one end of the chip. Pin one (1) of the integrated circuit

they are often clear glass or painted black. You will see

will be to the left of these markings. Be sure to orient the

a black or white band at one edge of the diode body,

IC before placing into its proper socket. Note that pin 1 of

this marking denotes the diode’s polarity. The colored

U1 will connect to the junction of capacitors C7

band is the diode’s cathode lead. When installing the

and C16.

diode make sure that you observe the polarity marking

by referring to the parts layout and the schematic

diagram. Polarity is important and must be observed in

order for the circuit to work properly.

Table 12-4

The 6N2 receiver has two crystal filters, a 455 kHz

Coil Winding Information

one and a 10.7 MHz one. These devices are small

three-lead devices and look much like a small capacitor

L1

4.5 turns insulated magnet wire - #22 ga. Air-core

with three leads. Make sure that you can identify them

coil wound on 1⁄4′′ form then remove coil.

properly before installing them on the circuit board. The

L2, L3 81⁄2 turns #24 ga. insulated magnet wire coil-wound 455 kHz unit connects to U1 at pins 5, 6 and 7, while

on 49A Series form - ferrite slug adjustable

the 10.7 MHz crystal filter is connected to pins 17, 18

(49A127MPC) Circuit Specialists.

and 19. The receiver also employs a single 10.24 MHz

Remove original coil from form and rewind 81⁄2 turns.

crystal which is connected between pins 4 and 6.

L4

1.5 turns insulated magnet wire - #22 ga. Air-core

This is a two-lead device and is usually a small

wound on 1⁄

metal can.

4 ′′ form then remove coil.

L5

.64 mH Coil (yellow) 455 kHz I-F Transformer

Now locate the air-wound coils L1 and L4. Coil L1 is

Circuit Specialists - (42IF301).

41⁄2 turns of wire, it will be placed on the right edge of

135

1

24

dark, dull or “blobby,” then you should un-solder that

2

23

particular joint and clean it and then re-solder the joint

3

22

so that it looks clean, shiny and bright. Next we will

(TO-92)

4

21

Plastic package (Z)

examine the circuit board for possible “short”

5

20

Output

Input

1

8

MC3362

circuits.

6

19

2

7

3

6

7

18

4

5

8

17

CAD

LM386-1

9

16

Bottom view

10

15

The front panel

LM78L05

11

14

12

13

assembly

MC3362P

The speaker was mounted on the receiver’s front panel.

Figure 12-6

Semiconductor pin-outs

Using the three black 4-40 screws, 4-40 nuts and #4

internal tooth washers, mount the three small right-

angle brackets to the speaker mounting holes. The short

side of the brackets should be against the panel. Use a

blunt tool to bend the brackets over the speaker. Using

Finishing the PC board

the hardware shown, mount the phono jack. Using the

hardware shown, mount the On-Off switch, 2M/6M

assembly

switch, squelch pot, volume pot, and tuning pot to the

front panel.

Now cut three 3′′ pieces of wire from the roll of 22

Orient the speaker terminals, so they don’t interfere

gauge solid wire and strip 1⁄4′′ of insulation off each end.

with the nearby battery mounting. Solder the loose end

Using these wires, solder the 5k potentiometer (VR2) to

of the shielded cable to the phono jack, center

the PC board. Be sure to mechanically attach each wire.

conductor to the phono jack terminal and shield to the

Note that VR3 is the tuning control potentiometer, the

GND terminal. Peel the backing off one side of the 1⁄2′′

center lead is connected to the PC board hole marked

wide, double-sided tape and stick it to the battery

(D), while the left-most pot terminal gets connected to

clamp. Peel the backing off the other side of the

2-Meter Dual-Band Amateur Radio the hole marked (N). The final potentiometer wire on double-sided tape and stick it to the inside bottom of the

the right side of the potentiometer goes to the hole

&

plastic case. With the power switch OFF, connect a 9V

marked (P).

alkaline battery to the battery snap and put the battery

Finally, connect up a short piece of coax to the

into the battery clamp. When the final test and

terminals on the PC board marked ANT and GND.

alignment (next section of manual) is completed,

The center wire of the coax goes to the terminal

place the front plate on the plastic case and insert the

marked antenna (ANT) and shield wire from the coax

four nylon plugs into the holes in each corner of

goes to the terminal marked ground or (GND). The

the plate.

other free end of the coax goes to RCA antenna jack

which gets mounted on the front panel of the

chassis box.

After completing the circuit board, take a short break

Connecting the front

and when we return, we will examine the circuit board

panel parts to the

for possible “cold” solder joints and “short” circuits.

Pick up the circuit board with the foil side of the circuit

PC board

board facing upwards toward you. First, we will look at

the circuit board for possible “cold” solder joints. Take

To wire the speaker, pot and switch, cut the indicated

a close look at the solder joints, they should all look

length of wire from the roll of 22 gauge solid wire and

Chapter Twelve: 6 clean, shiny and bright. If any of the solder joints look strip 1⁄4′′ of insulation off each end. Next, go ahead

136

Chapter Twelve: 6

and mount the phono jack at J1. Finally mount the

goes to the hole marked (E) on the circuit board.

On/Off switch, the 2 meter/6 meter band switch, the

Finally locate the 9 volt snap battery terminal stip

squelch potentiometer, the volume potentiometer, and

and connect it to the battery terminals on the far left

tuning potentiometer to the front panel as shown

marked BATT.

in Figure 12–7. For the jumper wire, cut 2′′ of 22 gauge

Now that your 6N2 receiver has been completed,

solid wire, strip 1⁄4′′ of insulation off each end and solder

it is time to test out your receiver to see if it is

to the points indicated. Attach two 4′′ long pieces of

going to work. Connect up the 9 volt battery clip

insulated wire to the speaker terminals and solder them.

to the 9 volt battery. Connect an antenna to the

Now solder two 4′′ pieces of insulated wire

antenna terminal. For testing purposes you can

to the On-Off switch, use the center terminal and

simply connect a 19′′ piece of wire to the antenna

one of the outside terminals on the switch. Next attach

terminals, or if you have an outdoor antenna you

three 3′′ long insulated wires to the volume control

can connect it up to the receiver. Position the band

on VR3.

switch to the 2-meter band position. Now adjust the

Next locate the Squelch control (VR1) and solder two

volume control to the mid-way position, and adjust the

3′′ long insulated wires to the potentiometer. Take the

squelch control counterclockwise so that you just

two free wires and connect them to the PC board. The

break the squelch and you should hear the receiver

center terminal from the potentiometer goes to the PC

noise coming from the speaker. If all is well, you

&

board hole marked (Q), while the other potentiometer

should hear a hissing sound or receiver noise. Adjust

lead goes to the hole marked (R).

the tuning control around the band, back and forth, and

2-Meter Dual-Band Amateur Radio

you should eventually hear a ham radio operator calling

Take the free ends of the two speaker wires and

another friend.

solder them to the circuit board at their respective

terminal strip on the bottom left side of the PC board.

In the event that you hear no receiver noise and

Now take the two free ends of the On-Off switch

the receiver appears “dead,” you will have to disconnect

leads and solder them to the terminals on the left

the antenna and battery clip and examine the receiver’s

side of the PC board. Next take the three potentiometer

circuit board for any errors which might have occurred

leads and solder them to the PC board. The center

during construction. Some of the most common causes

terminal of VR3 goes to the terminal marked (D)

for construction errors include installing diodes and

on the circuit board. The left-most potentiometer

electrolytic capacitors backwards in the circuit;

terminal goes to the hole marked (C) on the PC

remember that these components have polarity and it

board, while the right-most potentiometer terminal

must be observed in order for the circuit to work

properly. Another common problem is having resistors

installed in the wrong place on the circuit board.

Finally, when installing semiconductors such as

transistors and FETs, you must refer to the

manufacturer’s pin-out diagram and the parts layout

diagram along with the schematic when constructing

the circuit. Often times transistors are installed

incorrectly; also check the orientation of all integrated

circuits to make sure that you have oriented them

correctly with respect to their marking and pin

numbers. Hopefully you have found your error by

now and are ready to reassemble the circuit in order to

test once again.

Reconnect the antenna and battery leads and turn the

On-Off switch to the “On” position. Turn up the volume

control to the midway position, and set the BAND

Figure 12-7

6N2 meters

switch to the 2-meter position. The 2-meter band will

137

generally be much more active than the 6-meter band

input. Turn the tuning control on the receiver to the full

unless there is a 6-meter band “opening.” Now, you will

counterclockwise position (lowest frequency). With the

need to adjust the squelch control. The correct

squelch control tuned fully counterclockwise (OFF), a

adjustment of the squelch control is to advance the

“rushing” noise will be heard. Tune the RF generator

control until the receiver noise is silenced. When the

until the receiver noise disappears and note the

receiver is tuned across the band and a signal is found,

frequency on the generator dial. Next, rotate the receiver

the squelch will release and the transmission will be

tuning control to the full clockwise position (higher

heard. As you continue tuning away from this signal,

frequencies). Repeat the above procedure to determine

the squelch should again come into effect and “squelch”

the upper frequency of your tuning range. If the range is

the receiver noise. Remember that the function of the

too low, decrease L4 by spreading the turns. If the

squelch control is to eliminate static when there is no

range is too high, substitute the 39 pF capacitor

signal present. This control sets the level of passable

with the 33 pF capacitor in C6. Then, repeat both

signals. The squelch control works by raising the

procedures to determine the upper and lower frequency

voltage to the (–) input to the audio amplifier and thus

limits. With a little perseverance, you should arrive at a

disabling the amplifier output. Turn the squelch control

range covering the 2-meter band (144 to 148 MHz). Set

fully counterclockwise. The audio should produce a

the generator at different points (144, 145, 146, etc.)

hissing sound. Turning the squelch control clockwise

and tune the radio for quieting at each setting. Mark the

should quiet the audio. Check the leads going to the

dial with the appropriate values. Using the plastic

control.

alignment tool to adjust L3, follow the same procedure

for the 6-meter band (50 to 54 MHz). Note: Before the

Now that the receiver seems to be functioning, you

receiver is properly adjusted, you may receive a

will need to calibrate the receiver using an RF

broadcast from an FM station or TV station. These

frequency generator. You will need to borrow an RF

signals will be distorted because they are wide band

signal generator from a friend or local radio enthusiast

FM transmissions and the 6N2 is a narrow band

in order to calibrate your receiver for best

amateur receiver.

operation.

If a frequency counter is available, it can be

used to measure the frequency of the local oscillator

at pin 20 of U1. On the 2-meter band, the counter

2-Meter Dual-Band Amateur Radio Frequency measurements

should read 133.3 MHz to 137 MHz, and on the

6-meter band, it should read 39.3 MHz to

& Attach a two foot or longer length of wire to the

43.3 MHz.

male RCA plug and connect it to the radio antenna

jack. Install a fresh battery and turn the power

ON. Make sure that the squelch control is fully

Antenna considerations

counterclockwise and the volume control is set at

mid-position. A “rushing” noise should be heard

For local VHF reception, the VHF receiver will

from the speaker when no signal is present, which

operate fine just using a whip antenna. If you wish

is normal. Slowly tune the radio on each band and

to receive stations which are further away than just

listen for activity. Reception will only be possible

the local stations, you may want to install some sort

if someone is transmitting. If you know someone with

of outdoor antenna such as a ground plane or

a 2M or 6M transmitter, you should test your receiver

discone antenna for VHF operation. Since most

with known frequencies of transmission and adjust

of the transmissions in this band are of vertical

the high frequency oscillator for proper tuning of

polarization, vertical antennas, ground plane and

desired bands.

discone antennas will work very well in this

A calibrated RF generator may also be used to adjust

band. Various VHF scanner type antennas from

the oscillators. Start with the 2-meter band. Loosely

your local Radio Shack store will work fine

Chapter Twelve: 6 couple the output of the RF generator to the receiver as well.

138

Chapter Twelve: 6

Connect up a whip antenna or an outdoor Discone

popular ham radio VHF bands. Note the SSB satellite

antenna and you can now begin to listen-in to the

and long-range portion of the 2-meter band from

exciting world of VHF ham radio communication. The

144.1 MHz to 144.3 MHz and the 6-meter DX windows

charts in Table 12-5 illustrate the band plan for the two

around 51.1 and 52.05 MHz.

Table 12-5

2- Meter & 6-Meter Amateur Radio BandS

144

.1

.3

.5 .6 .9

.1

145

.2

.5 .8 146 .4 .6 .61 147 .39 .42 .6

148 MHz

2

METERS

SSB

SATELLITE ONLY(NO FM)

DX WINDOW

DX WINDOW

50.1

51 .1

52.05

53

54 MHz

6

R.C

R.C

METERS

& 2-Meter Dual-Band Amateur Radio

139

Chapter 13

Active and Passive Aircraft

Band Receivers

C9,17,19,20,28,30

.01 µF

Parts list

disk capacitor

(marked .01 or 103 or

Active Aircraft Receiver

10 nf)

R1,R2,R3

10k

C23,C24

.1 µF disk

potentiometers

capacitor (marked .1

or 104)

R5,7,11,18,25,27

1k ohm

[brown-black-red]

C22

.47 µF electrolytic

capacitor

R6,R28

270 ohm

[red-violet-brown]

C10,15,21,25,26,31

4.7

to 10 µF electrolytic

R8,12,17,23

10k ohm

capacitor

[brown-black-orange]

C18,27,29

100 to 220 µF

R26

22k ohm

electrolytic capacitor

[red-red-orange]

Q1

2SC2498 or 2SC2570A

R13,R22

33k ohm

NPN UHF transistor

[orange-orange-orange]

Q2

2N3904 NPN

R4,9,15,16,20,21,24

transistor

47k ohm

[yellow-violet-orange]

U1

SA602 8 pin IC

R19

100k ohm

U2

MC1350 8 pin IC

[brown-black-yellow]

U3

LM324 14 pin IC

R10,R14

1 megohm

U4

LM386 8 pin IC

[brown-black-green]

D1

BB505 varactor diode

C3,C5

3.9 pF ceramic

(marked BB505)

capacitor

D2

1N270 germanium diode

C11

10 pF ceramic

D3

1N4148 silicon diode

capacitor

L1,L3,L5

See Table 13-3

C12,C14

27 pF ceramic

capacitor

L2,L4

See Table 13-3

C2,C4,C6

82 pF ceramic

L6

See Table 13-3

capacitor

L7

See Table 13-3

C1,7,8,13,16

.001 µF

FL1

10.7 MHz ceramic

disk capacitor

filter - (Murata/

(marked.001 or 102)

Digi-Key)

140

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Thirteen: Aircraft Band Receivers

PH

high-impedance

S1

PC mount DPDT switch

(2 k ohm) headphone

J1

PC mount RCA jack

Misc

battery clip,

J2

subminiature phone

battery holder, wire,

jack

enclosure, etc.

B1

9 volt battery

Eavesdroping in on the pilots as they trace their way

across the sky can be very fascinating and exciting

Misc

PC board, battery

listening for aircraft enthusiasts of all ages. An aircraft

clip, battery holder

receiver will allow you to listen-in to high flying

*** Ramsey Electronics

commercial aircraft from jumbos to pipers, as well as

Inc.

control towers passing instructions to the airplanes

Passive Aircraft Monitor

overhead. It will provide many hours of interesting

R1,R2

10 megohm, 1/ watt,

listening.

4

5% resistor

In this chapter, we will present two different types of

R3

100k ohm

aircraft receivers: a passive aircraft receiver and an

potentiometer - volume

active aircraft receiver. A passive aircraft receiver is a

(chassis mount)

more simple receiver with no local oscillator to interfere

with the on-board aircraft electronics. A passive aircraft

R4,R5

3.3k ohm, 1/ watt,

4

receiver is defined as a tuned detector with an amplifier

5% resistor

which can be carried aboard an airplane in order to

R6

100 k ohm, 1/ watt,

4

listen-in to the pilot while you are on a flight. You will

5% resistor

be able to listen-in to the pilot in flight as well as the

R7

100 ohm 1/ watt,

control tower when in fairly close range. This type of

4

5% resistor

receiver does not interfere with the airplane’s

electronics and in most instances you will be permitted

C1

1.5 pF, 35 volt

to use this type of receiver on-board your aircraft. The

mica/poly capacitor

active receiver is a more sensitive active receiver which

C2

5-18 pF trimmer

can be used at home to listen-in to high-flying aircraft

capacitor (tuning)

as well as control towers over longer distances.

C3

.01 µF, 35 volt

Listening to aircraft communications can be very

ceramic disk capacitor

interesting but very cryptic, with lots of bursts of

C4

330 pF, 35 volt

information passing in a short period of time.

polyester capacitor

C5,C8

100 µF, 35 volt

electrolytic

Active aircraft band

capacitor

receiver

C6,C7

1 µF, 35 volt

electrolytic capacitor

Ideal for arm-chair pilots, student pilots and the

D1

1N34 germanium diode

seasoned pilots, this sensitive receiver will pick up

L1

.15 µH choke coil -

planes up to 100 miles away. The active aircraft band

(Digi-Key)

receiver tunes the aircraft band between 118 and

136 MHz and will allow you to listen to control towers,

U1

LM358 dual op-amp

centers, and planes en-route to their destination. The

S1

SPST toggle switch

active aircraft band receiver, shown in Figure 13-1 has

B1

9 volt transistor

good sensitivity, image rejection, signal-to-noise ratio

radio battery

and stability. It is designed for casual “listening in” both

141

pilots communicate is the control tower, ground control,

clearance delivery and ATIS or “Automatic Terminal

Information System.”

At most metropolitan airports, a pilot communicates

with the FAA on a frequency called “Clearance

Delivery” to obtain approval or clearance of the

intended flight plan. This communication is done before

contacting ground control for taxi instructions. From the

control tower, ground movements on ramps and

taxiways are handled on the “Ground Control”

frequency, while runway and in-flight maneuvers near

the airport (takeoffs, local traffic patterns, final

Figure 13-1

Active aircraft band receiver

approaches and landings) are on the “Control Tower”

frequency. ATIS, or “Automatic Terminal Information

System” is a repeated broadcast about basic weather

ground and air communication, for both commercial

information, runways in use, and any special

airlines and general aviation, and it will provide you

information such as closed taxiways or runways. Such a

with many years of easy sky-monitoring enjoyment.

broadcast offers an excellent steady signal source for

This project is especially good for people with an

initial adjustment of your receiver. If you are close

interest in learning more about aviation and electronics

enough to the airport to receive ATIS, you will hear the

and radio. The active aircraft receiver can be built by

Approach Control and the Departure Control

folks of all ages and skill levels.

transmissions. These air traffic radar controllers

coordinate all flight operations in the vicinity of busy

metropolitan airport areas, and are called the ATC

Center.

What you can hear

When you hear a pilot talking with “Jacksonville

Center” or “Indianapolis Center,” you know the aircraft

A basic fact about the VHF Aviation Band which even

is really enroute on a flight rather than just leaving or

licensed pilots can overlook or forget is that

just approaching a destination. A pilot will be in touch

communications are in the AM mode, not FM, as in the

with several different “Regional Centers” during a

case of the FM broadcast band immediately below it,

cross-country flight. These smaller centers are called

and the VHF public service and ham bands immediately

“Unicom” centers.

above it. No matter where you live, you will be able to

receive at least the airborne side of many air traffic

Airports without control towers rely on the local

communications. If you know where to tune, you’ll hear

“Unicom” frequency dedicated only to advisory

any aircraft you can see, PLUS planes a hundred miles

communications between pilots and ground personnel

away and more, since VHF signals travel “line of sight”.

such as fuel service operators. The people on the ground

An airliner at 35,000 feet altitude in the next state is

can advise the pilot on the status of incoming or

still line of sight to your antenna. Similarly, whatever

outgoing aircraft, but the pilot remains responsible for

ground stations you may hear are also determined by

landing and takeoff decisions. Typical Unicom

this “line of sight” character of VHF communication. If

frequencies are 122.8 and 123.0 MHz.

there are no major obstacles between your antenna and

The FAA’s network of Flight Service Stations keeps

an airport (tall buildings, hills, etc.), you’ll be able to

track of flight plans, provides weather briefings and

hear both sides of many kinds of aviation

other services to pilots. Some advisory radio

communication. Be prepared for them to be fast and to

communication takes place between pilots and a

the point, and for the same airplane to move to several

regional “FSS.” If there is an FSS in your local area, but

different frequencies in the span of a few minutes! The

no airport control towers, the FSS radio frequency will

Chapter Thirteen: Aircraft Band Receivers most common types of ground services with which stay interesting.

142

Chapter Thirteen: Aircraft Band Receivers

“United 330, traffic at 9 o’clock,

Fast talking pilot

4 miles, altitude unknown.”

and controllers

The controller alerts United Airlines flight #330 of radar

contact with some other aircraft off to the pilot’s left at

Aviation communication is brief, but it is clear and

a 9 o’clock position. Since the unknown plane’s altitude

full of meaning. Usually, pilots repeat back exactly

is also unknown, both controller and pilot realize that it

what they hear from a controller so that both know

is a smaller private plane not equipped with

that the message or instructions were correctly

altitude-reporting equipment.

interpreted. If you are listening in, it is hard to track

everything said from a cockpit, particularly in big city

areas. Just to taxi, take off and fly a few miles, a pilot

Active receiver circuit

may talk with six or eight different air traffic control

operations, all on different frequencies, all within a few

description

minutes! Here are the meanings of a few typical

communications:

Now, take a look at the schematic diagram shown in

Figure 13-2. The aircraft band antenna is first coupled

through C1 to a three-section tuned LC filter input

“Miami center, delta 545 heavy

network. The aircraft band signals ranging from 118 to

out of three-zero for two-five.”

135 MHz signals are amplified by VHF transistor Q1

and fed to the input of U1, the SA602 mixer-oscillator.

Delta Flight 545 acknowledges Miami Center’s

Inductor L6 and its associated capacitor network

clearance to descend from 30,000 feet to 25,000 feet

establish the LO (local oscillator) frequency at

altitude. The word “heavy” means that the plane is a

10.7 MHz higher than the incoming 118–135 MHz

jumbo jet such as 747, DC-10, etc.

signals. The local oscillator frequency may be tuned

across about 15 MHz by the varactor tuning network

“Seneca 432 lima cleared

formed by diode D1 and resistor R1. The 10.7 MHz

to outer marker. contact

difference between the local oscillator and the received

Tower 118.7.”

signal is fed through the 10.7 MHz ceramic filter FL1,

and then amplified by Q2 and the signal is then applied

The local Approach Control is saying that the

to U2, the MC1350 IF amplifier IC with AGC input.

Piper Seneca with the N-number (tail number)

The 10.7 MHz IF is peaked by inductor L7, and the

ending in “432L” is cleared to continue flying an

AM audio signal is then demodulated by diode D2

instrument approach to the outer marker (a precision

and fed through the four op-amps of U3, the LM324,

radio beacon located near the airport) and should

where volume control, AGC output, audio filtering

immediately call the airport radio control tower at

and squelch functions are managed. The LM386 (U4)

118.7 MHz. This message also implies that the

is the audio amplifier, and is capable of driving

controller does not expect to talk again with that

simple communications speakers to excellent volume

aircraft.

levels.

“Cessna 723, squawk

6750, climb and maintain

Circuit construction

five thousand.”

The aircraft band receiver is best constructed on a

A controller is telling the Cessna pilot to set the

printed circuit board for best results. Place your

airplane’s radar transponder to code 6750, climb to and

schematic diagram in front of you, heat up your 27 to

fly level at an altitude of 5000 feet.

30 watt pencil tipped soldering iron and prepare to insert

143

C h a p t e r T h i r t e e n : A i r c r a f t B a n d R e c e i v e r s 144

S1

+

+

C10

R7

R11

R28

C31

C18

R5

+

+

C8

B1

R4

C16

8

R10

1

FL-1

4

4

2

C17

1

3

Q1

R6

U1

2

3

1

Q2

U2

2

7

8

D2

5

C9

3

6

7

6

R26

C6

C19

C7

R8

C11

T1

R12

L5

C13

L4

C4

L6

C12

C20

+9 V

R25

C5

C30

C14

C23

C3

L3

C24

R9

R1

R16

R17

K

L2

D1

R22

C2

C21

+9 V

A

+9 V

R21

+

10

C1

C15

+

4

2

–

L1

R119

8

12

5

C27

+9 V

U3c

+

U3a

1

R15

3

7

+

J1

–

U3d

R18

+

U3b

C26

9

14

13

11

6

3

D3

–

+

–

6

C22

+

+ 5

+

R23

+9 V

U4

J2

2

R14

C29

7

–

R20

4

R27

C28

R24

R3

R2

R13

C25

Ground

Figure 13-2

Active aircraft receiver schematic. Courtesy of Ramsey Electronics Chapter Thirteen: Aircraft Band Receivers

Table 13-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

the components into the circuit board. You can fabricate

end-cutters. Cut the excess leads flush to the

your own circuit board from scratch if you are an

PC board.

experienced builder or you could elect to build the

Next we are going to install the capacitors for the

receiver from the kit supplier, Ramsey Electronics,

project. Capacitors are described as electrolytic and

listed in the Appendix. We will build the receiver in

non-electrolytic types. Electrolytic types are large sized

sections and will begin first with the antenna and input

and larger in value than non-electrolytic types.

pre-amplifier section.

Electrolytic type capacitors have polarity, i.e. both a

Before we go ahead and build the aircraft receiver,

positive and negative terminal, often with color band

let’s take a few moments to look at Table 13-1, which

and/or (+) or minus (−) marking on them. These

illustrates the resistor color chart. Resistors have three

electrolytic capacitors must be installed with respect to

or four color bands, which begin at one edge of the

these polarity markings if you expect the circuit to work

resistor body. The first color band represents the

correctly. Take your time installing them and refer

resistor’s first digit value, while the second color band

regularly to both the schematic and parts layout

denotes the second digit of the resistor value. The third

diagrams. Non-electrolytic capacitors can sometimes be

color band represents the multiplier value of the resistor.

very small in size, and often their actual value will NOT

The fourth color band denotes the tolerance value of the

be printed on them. A three-digit code is used to help

resistor. A silver band represents a 10% tolerance, while

identify these capacitors; refer to Table 13-2. For

a gold band notes a 5% tolerance value. The absence of

example, a .001 µF capacitor would be marked with (102),

a fourth color band states that the resistor has a

while a .01 µF capacitor would be marked with (103).

20% tolerance value. Therefore, a 10,000 ohm or

Go ahead and install capacitors C1 through C8 into

10 k ohm resistor would have a brown band (1) a

their respective PC holes on the PC board, being sure to

black band (0) and a multiplier of (000), and an orange

observe polarity on the capacitors before installing them

band.

on the PC board. Most electrolytics will have a black

Go ahead and install resistors R4, R5 and R6, then

band or a plus or minus marking next to a pin. Solder

solder them in place on the PC board. Then cut the

the capacitors to the PC board, then remove the excess

excess leads from the PC board with a pair of

leads. Next install inductors L1, L2, L3 and L4 into

145

Table 13-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Thirteen: Aircraft Band Receivers 820pF

Ceramic

821

2

Mylar

205

146

Chapter Thirteen: Aircraft Band Receivers

Table 13-3

C10, C11 and C12 followed by capacitors C13, C16,

Coil winding information

C17, C19 and C20 followed by C30 and C31. Be sure

to observe the polarity of the capacitors when installing

L1,L3,L5

1.5 turns #28 ga. magnet wire, 5 mm inner

them on the board to prevent circuit damage when

diameter air core - about 1 mm spacing

power is first applied. Install the capacitors into their

(2-turns works fine)

respective location on the PC board. Once inserted,

L2,L4

.33 µH, molded inductor (Digi-Key M9R33-ND)

solder the capacitors to the circuit board and then

L6

.1 µH, 3.5 turns, slug tuned coil (Digi-Key

remove the excess leads.

TK2816-ND)

Now locate diode D1 and D2, and note that the

L7

10.7 MHz shielded I-F transformer (Mouser

cathode or black band side of the diode points to the

42FIF122) or Circuit Specialists

battery. Diode D1 is the varactor “tuning” diode. Go

ahead and install these diodes, then solder them to the

board. Remove the excess leads. Locate transistor Q2

and install it on the PC, once you have identified all the

their respective holes, followed by L5; see Table 13-3

leads. Solder Q2 to the board, and then remove the

for winding instructions. When you have inserted the

excess leads with your end-cutter. Now locate and

inductors, you can solder them in place and then cut the

install inductor L6, the 3.5-turn slug tuned coil and L7,

excess component leads flush to the edge of the circuit

the 10.7 I-F transformer. Remember to trim the extra

board.

lead lengths as needed. Locate the FL1, the 10.7 MHz

Before you go ahead and install the transistors and

ceramic filter, it will have three leads and is usually a

integrated circuits, refer to the semiconductor pin-out

small square component. Solder it in place and remove

diagram shown in Figure 13-3, which will help you

the excess leads. Finally install the 8-pin SA602 local

orient the components. Now locate and install

oscillator-mixer at U1. It is advisable to install an IC

transistor Q1, being sure you have the correct

socket into place in the proper location and then insert

component before installing it on the PC board. Be sure

the IC into the socket. This is good insurance in the

you can identify all three leads as to their correct

event of a possible component failure at some later

pin-outs before inserting it into the circuit board to

point. When inserting the IC into the socket be sure to

avoid damage to the circuit once power is later applied.

first identify which pin is #1. Usually each IC will have

Solder Q1 to the board and then remove the excess

a small circle or cut-out on the top or top left side of the

leads.

IC. Usually the pin is just to the right of this indented

Next we are going to move on to installing the Local

circle.

Oscillator components. First install resistors R1, R7,

Next we will install the LM324 IC circuit

R8, and R9 followed by resistors R10, R11, R12 and

components. First locate resistors R13, R14, R15, R16,

then resistors R25, R26 and R28. Solder the resistors

R17, R18 and R19 followed by resistors R20, R21, R22,

into their respective locations and be sure to remove the

R23 and R24. Install these resistors in their respective

excess lead lengths. Next we will install capacitors C9,

locations and then solder them in place on the

1

14

1

14

1

1

1

2

13

1

8

1

8

1

8

2

7

2

7

2

3

12

7

3

6

3

6

3

6

4

11

EBC

EBC

4

5

4

5

4

5

5

10

6

9

SA602

LM386

MC1350

7

8

2SC2498

2N3904

NTE746

LM324

Figure 13-3

Semiconductor pin-outs

147

PC board. Remember to cut the extra leads. Now locate

Next we will inspect the PC board for “short”

diode D3, remember to observe the polarity when

circuits. Often “stray” or “cut” component leads will

installing D3. Solder the diode in place, then remove the

“bridge” across or between circuit traces on the PC

excess lead lengths. Now locate and install capacitors

board. These possible “shorts” can cause damage to the

C18, C21, C22 followed by capacitors C23, C24 and

circuit when power is first applied, so it is best to

C25. Remember electrolytic capacitors have polarity

remove any “bridging” leads or solder blobs or “shorts”

markings and they must be observed for the circuit to

before power is sent to the circuit board. Look over the

operate correctly. You will see either a plus or minus

board carefully for any signs of “bridging” wires or

marking at one end of the capacitor. Once installed,

blobs of solder. Once you are comfortable with your

solder the capacitors in place and then remove the extra

inspection, you can lay the circuit board back down on

leads by cutting them flush to the circuit board. Finally

the table.

install an integrated circuit socket for U3 and then place

U3 into the socket, but be sure to install it correctly,

observing the indented circle as near pin 1 on the IC.

Enclosure

Finally we are going to install the audio amplifier

components. First locate resistor R27 and install it on

recommendations

the PC board. Next solder it in place and cut the extra

leads. Now, locate and install capacitors C26, C27, C28,

If your first goal is economy and rugged portability, you

and C29. Remember C26 and C27 are electrolytic

will find that the circuit board can be nicely mounted in

types, so polarity must be observed before installing

a standard VHS videotape storage box, which also gives

them. Finally install an IC socket for U4 the LM386

room for a speaker or earphone storage, and even a roll

amplifier IC. When installing U4 be sure to observe the

of antenna wire. The controls are easily mounted at one

correct orientation before inserting it into the socket to

end of such a box. It may be necessary to cut away the

prevent damage when power is applied.

molded posts which secure the tape cassette itself.

Now you finish up the circuit by installing the 9 volt

These storage boxes come in several styles, so pick one

battery holder, the 9 volt battery clip, followed by

which truly looks practical as a project

switch S1. Once these components have been installed

enclosure.

you can locate and install jacks J1 and J2 onto the

The most economical metal enclosure nicely suited

circuit board.

for Ramsey PC board kits is the Radio Shack

If you haven’t already installed the potentiometers,

270-253A. This metal utility cabinet can accommodate

R1, R2 and R3, go ahead and install them and solder

one or two different receiver boards plus a speaker, with

the controls firmly in place. Be sure the mounting tabs

room for various refinements you might want to add,

are completely soldered for a good mechanical

such as a bigger battery pack, fine tuning control, and

connection.

so forth. When you have selected your enclosure, you

Let’s take a short break and when we return we will

can place the circuit board into the case and mount it.

inspect the PC board for poor solder joints and “short”

Be sure to allow the extension of the squelch control,

circuits before applying power to the circuit board. Pick

the volume control and the tuning control on the front

up the circuit board and bring the foil side of the board

panel of the chassis. The speaker can be mounted on the

up towards you to inspect the board. First, we will look

top of the case, and the earphone and antenna jack can

for “cold” or poor solder joints on the PC board. Take a

be mounted on the rear of the receiver.

look at each of the solder joints. You want to make sure

Congratulations, you have successfully completed

each of the solder joints appears to look clean, smooth

your active aircraft band receiver. Now you are ready to

and shiny. If you see any solder joints that look dull or

test and adjust the receiver before setting down and

“blobby” then you will need to remove the solder from

enjoying it. Now, you can attach a speaker or pair of

the joint with a solder-sucker or wick and then re-solder

headphones to jack J2. Next, attach a whip antenna to

the joint, so that it appears to be clean, shiny and

jack J1, and then connect a 9 volt battery to the battery

Chapter Thirteen: Aircraft Band Receivers smooth.

clip leads and we can go ahead and test the active

148

Chapter Thirteen: Aircraft Band Receivers

aircraft receiver. Now, turn the On-Off switch to the

“ON” position. Be sure to turn down the squelch control

Adjustment and alignment

to below the threshold point, so you can hear a hissing

sound coming from the speaker or headphone. Now,

Alignment of the air-band receiver consists of simply

turn up the volume control to about midway. Take a few

adjusting L6 for the desired tuning range and peaking

minutes to tune up and down the band with the

the IF transformer (L7). If you are using a signal

main tuning control. If after about 15 minutes, you do

generator, frequency counter or other VHF receiver for

not hear any transmissions on your radio or if you do

calibration, remember that you want to set the local

not hear any hissing sounds from the speaker,

oscillator frequency 10.7 MHz higher than the desired

then you know there could be a problem with your

signal or range to be received. Adjustment of the L6

receiver.

oscillator coil MUST be made with a non-metallic

In the event of a problem with your new aircraft band

alignment tool. The use of a metal tool of any kind will

receiver, you will have to disconnect the speaker,

detune the coil drastically, making alignment almost

antenna and battery and visually inspect the circuit

impossible. Also, if you’re receiving FM broadcast

board for any errors. Often a second or new pair of eyes

stations, you have the slug tuned too far down in the

is very helpful in locating problems on circuit boards.

coil form. Turn it until it is higher in the form and try

The most likely causes of circuit failure are misplaced

again. One other thing that you can do to improve the

components or components such as diodes and

operation of your kit is to spread out the three 2-turn

electrolytic capacitors installed backwards. The second

coils at the antenna input, L1, L3, and L5. Stretching

most likely cause for problems are semiconductors,

these out will give you greater sensitivity.

such as transistors installed backwards. Be sure to

Once you know you are receiving aircraft or airport

re-check the manufacturer data sheets for proper pin-out

transmissions, adjust the IF transformer (L7) for best

information when installing the transistors. Finally,

reception. Typically, L7 is adjusted 2–3 turns from the

check the orientation of the integrated circuits in their

top of the shield can. If you don’t have any signal

respective sockets; sometimes the ICs can be put in

reference equipment at home, and are not yet hearing

backwards in their sockets causing the circuit to

airplanes, your best bet is to pack up your AR1C and

malfunction. Once you have fully inspected and

needed tools and head for the nearest airport! If there is

hopefully located your problem, you can reconnect the

no control tower, don’t hesitate to visit a general

battery, headphones and antenna and then retest the

aviation service center on the airport grounds. If

receiver once again.

you’ve never done this before, you will probably

find it to be a fun and interesting experience. Ask

which are the most active frequencies and adjust L6

and your front panel tuning control until you hear the

Antenna

action. A ground service operator or private pilot may

considerations

be willing to give you a brief test transmission on the

122.8 Unicom frequency. Remember, also, that if

An antenna for your new aircraft receiver can be as

your airport has ATIS transmissions, you can get a

simple as a 21′′ piece of wire, an extendable whip

steady test signal as soon as you are line-of-sight with

antenna or a roof-mounted ground-plane aviation

its antenna.

antenna. Most folks near an airport will get plenty of in-

The aircraft receiver does not produce a loud hiss

the-air action from a wire or whip antenna, but if you’re

when no signal is being received (unlike an FM receiver

more than a few miles away, a decent roof-mount

or expensive AM receiver); this is due to the somewhat

antenna is the way to go. Radio Shack sells an ideal

limited amount of IF or Intermediate Frequency gain.

antenna designed for scanners which covers the aircraft

Increasing the IF gain would produce a hiss and

band nicely and it costs around $30. A low cost TV

marginally better sensitivity (about a microvolt) but also

antenna works well, even better if rotated 90 degrees

require much more alignment, AGC circuitry, and

(remember aircraft antennas are vertically polarized).

builder ability—far beyond the intention of this kit.

149

the control tower. The passive aircraft receiver is shown

Tuning the aircraft

in Figure 13-4. The passive aircraft receiver can be built

small enough to place inside your vest pocket and it

receiver

operates from an ordinary 9 volt battery.

The passive aircraft receiver is basically an amplified

With the varactor tuning control capable of going across

type of “crystal radio” designed to receive AM aircraft

10–15 MHz, and with pilots and controllers talking so

transmissions. The “passive” design uses no oscillators

briefly, you will need to get used to tuning your

or other RF circuitry capable of interfering with aircraft

receiver! You’ll find that ANY knob gives smoother

communications. This receiver utilizes a coil/capacitor

tuning than the bare control shaft, and that a “vernier”

tuned “front-end,” which feeds an RF signal to a detector

dial will make the procedure even easier—but at the

diode. The tuning capacitor may be any small variable

expense of being able to check up and down the band

with a range from about 5 pF to about 15 or 20 pF. The

quickly, which you might like to do if you’re tracking

0.15 µH inductor may be a molded choke or a few turns

the same airplane. The air-band receiver is designed to

wound with a small diameter. Experiment with the coil

let you explore the entire communications section of the

to get the desired tuning range. The aircraft frequencies

aviation band. If you become really interested only in

are directly above the FM band so a proper inductor will

being able to check a certain frequency such as a nearby

tune FM stations with the capacitor set near maximum

FAA control tower, or Unicom, it will be helpful to

capacity. (The FM stations will sound distorted since

mark that spot on a dial template such as is reproduced

they are being slope detected.) A 1N34 germanium

for your convenience below.

detector diode or a Schottky diode like the 1N5711 or

HP2835 should be used as the detector diode in this

receiver circuit. The 10 megohm resistors provide a small

“VOR” or “OMNI”

diode bias current for better detector efficiency.

transmissions

The LM358 dual op-amp amplifier draws under 1 ma

so the battery life should be quite long. Potentiometer

While driving around the countryside you may have come

R3 is used to adjust the gain to the second stage of the

across a tall white “cone” structure near your airport or in

dual op-amp. The second op-amp stage drives a

the middle of a big farming field; it is useful for you to

100 ohm resistor in series with a 100 µF capacitor. You

know that these are VHF navigational aids operating in

must use a high impedance “crystal” headphone, since

the 118–135 MHz frequency range, just below the air-

the op-amp output will not drive a speaker directly.

ground communications range, sending a steady signal

A speaker amplifier may be added to drive a speaker or

which may be helpful in initial alignment. If you tune in

low-z earphone, if desired, but the power consumption

such a signal on your receiver, remember that you will

will increase sharply, as will the size of the receiver.

have to increase the local oscillator frequency later in

The passive aircraft receiver is powered from an

order to listen to air traffic communications.

ordinary 9 volt transistor radio battery. The entire

aircraft band receiver can be built inside a small

plastic box. Simply mount an SPST slide switch on the

Passive aircraft

side of the case to apply power to the circuit. If you

elect, you can install a 1⁄8′′ phone jack for the “crystal”

receiver

headphone.

The passive air-band receiver is a type of “crystal” radio

which contains no local oscillator which might

interferes with the on-board aircraft’s sensitive

Construction

electronics. The passive aircraft receiver broadly tunes

from 118 MHz to 136 MHz, and was designed to listen-

The passive air-band receiver can be constructed on

Chapter Thirteen: Aircraft Band Receivers in to in-flight communications between your pilot and a regular circuit board or it could be built on a

150

Chapter Thirteen: Aircraft Band Receivers

Antenna

B1

S1

+

+

9 V

C1

C5

R2

D1

8

5 +

R7

C8

3 +

1

7

U1:A

U1:B

6

+

2

–

–

4

Phones

C2

L1

R3

C4

R6

R1

C3

R4

R5

+

+

C6

C7

Figure 13-4

Passive aircraft receiver schematic

“quick-board” which contains ready-made circuit traces,

power source. Note that pin 4 of the IC is connected to

these are available at Radio Shack stores.

the circuit ground.

You may want to lay out the circuit so that the tuning

You can elect to use a small speaker in this circuit,

control is at one edge of the board, which will make

but in order to make a miniature receiver you may want

things a little easier when installing the circuit in an

to simply use a small 1⁄8′′ mini jack and just plug into a

enclosure. Building the circuit is pretty straightforward

pair of small earphones. The circuit is powered from a

and should only take a few hours to build. Refer to

standard 9 volt battery; remember the black or minus (−)

Table 13-1 for identifying the resistors and Table 13-2

battery clip is connected to ground, while the plus (+) or

for identifying the small capacitors in the circuit.

red battery clip lead is connected to capacitor C5 at the

Remember it is very important to install the diode

plus (+) end.

correctly with respect to its polarity in order for the

You will want to have the tuning capacitor C2

circuit to work properly. The passive air-band receiver

near the edge of the circuit board, so that you can

also contains a few electrolytic capacitors, and you will

allow the tuning knob to protrude through the case

remember that these devices have polarity and it must

so you can easily tune the receiver. Once the

be observed for the circuit to work. The aircraft receiver

receiver has been completed, you should take a few

uses a dual op-amp to amplify the signals and you will

minutes rest.

have to ensure that it is installed correctly. An integrated

circuit is highly recommended for the op-amp. In the

After the break, you should inspect the foil side of

event of a circuit failure at some later date, it is much

the circuit board for any “cold” solder joints. Cold

easier to simply unplug an IC rather than trying to un-

solder joints often look dark, dull or “blobby.” If you

solder one from a PC board to replace it with a new

see any solder joints that look this way, you should re-

one. When installing the IC into its socket, you will

solder the connections. You should also take a moment

have to make sure that you orient it correctly. An IC

to examine the circuit board for any “short-circuits”

will typically have a notch or small cut-out at one end

which may be the result of a “stray” component lead

of the IC case. Pin one (1) will be to the left of the

shorting between circuit traces.

cut-out of notch when viewed from the top of the IC.

You can make yourself an antenna from a piece of

In this project pin 1 of the IC connects to potentiometer

stiff 20 ga. wire as a whip antenna to capacitor C1, or

R3, while pin 8 of the IC is connected to the

install a miniature jack in order to plug in a

151

whip antenna. The antenna can be a 6′′ piece of #20 ga.

To test the passive aircraft receiver, park near

stiff solid copper wire or a small telescoping aluminum

your local airport. Turn on the passive air-band

antenna connected to capacitor C1. Radio Shack has a

receiver, attach your wire antenna or pull up your

good selection of whip antennas. You could elect to

telescoping antenna and tune the receiver. You should

solder the wire antenna directly to C1 and just bring the

try to listen when you see an aircraft take-off or land or

antenna out the top of the enclosure, or you could install

when you see an aircraft taxiing along the runway. If

a small 1⁄2′′ mini jack for the antenna on the rear of the

you can get close to the tower in a small airport, that

enclosure. The selectivity is reduce as the antenna

should ensure that you will be able to test your

length is increased so best performance is achieved with

receiver adequately. As you see a plane arrive or leave,

the shortest acceptable antenna. Try increasing the

“tune” around the band and you should hear either the

1.8 pF capacitor value when using very short antennas

pilot or the control tower. If you plan on taking the

and decreasing it for long antennas. In order to “tune”

passive aircraft receiver on-board an aircraft to

the passive aircraft receiver you can either leave a small

listen-in to the pilot during your flight, you should ask

hole on the side of the plastic enclosure to adjust the

the pilot or stewardess if it is permitted aboard your

frequency using a plastic tuning tool, or you need to

aircraft. Generally you are given permission without a

find a way to attach a plastic knob onto the tuning

problem. Enjoy building and using your new aircraft

screw; you will have to drill a larger hole in the case to

receivers!

bring the knob outside the case for easy tuning.

Chapter Thirteen: Aircraft Band Receivers

152

Chapter 14

VLF or Very Low Frequency

Radio Receiver

C1,C3

47 pF, 35 volt

Parts list

mica capacitor

C2

100 pF, 35 volt

VLF Whistler

mica capacitor

Receiver

C4,C5,C6

3.3 nF,

R1,R4

10k ohm 1/4w,

35 volt mylar capacitor

5% resistor

C7,C15

.01 µF, 35 volt

R2,R3

22k ohm 1/4w,

ceramic disk capacitor

5% resistor

C8

27 pF, 35 volt mica

R5

6.2 megohm, 1/4w

capacitor

5% resistor

C9

1 µF, 35 volt

R6

1 meg ohm

electrolytic capacitor

potentiometer

(trimpot) - single

C10

.18 µF, 35 volt

turn

tantalum capacitor

R7

10 megohm, 1/

C11

.12 µF, 35 volt

4w

5% resistor

tantalum capacitor

R8

1k ohm, 1/

C12

1.8 µF, 35 volt

4w

5% resistor

tantalum capacitor

R9

1k ohm, 1/

C13

.68 µF, 35 volt

4w

5% resistor

tantalum capacitor

R10

3.3k ohm, 1/

C14

.22 µF, 35 volt

4w

5% resistor

tantalum capacitor

R11,R12

820 ohm, 1/

C16

.068 µF, 35 volt

4w

5% resistor

tantalum capacitor

R13

10k ohm

C17,C18

.22 µF, 35 volt

potentiometer

tantalum capacitor

(panel)

C19

.05 µF, 35 volt

R14,R17

10 ohm, 1/

ceramic disk capacitor

4w,

5% resistor

C20,C22,C24

100 µF,

R15,R16

2.2k ohm, 1/

35 volt electrolytic

4w,

5% resistor

capacitor

153

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

C21,C23

.1 µF,35 volt

modifications along the way. The frequencies of the

ceramic disk capacitor

original pulse can be spread out in time (a process

called “dispersion”) since the higher frequencies travel

L1

120 mH coil (Mouser

a little faster than the lower. The result is that the short

electronics)

impulse from a lightning strike in South America can

L2

150 mH coil (Mouser

sound like a chirp in Texas. Slower sweeping tones are

electronics)

called “whistlers” and they are a bit of a mystery. The

L3

18 mH coil (Mouser

energy from a lightning bolt streams out into space into

electronics)

a region called the “magnetosphere,” magnetized

plasma created by the interaction of solar wind with the

L4

56 mH coil (Mouser

Earth’s magnetic field. The lightning pulse is reflected

electronics)

or “ducted” back down to Earth after a very long trip

Q1a,Q1b

U401 Siliconix

during which time the frequencies are spread out by a

Dual matched N-Channel

dispersion-like process. Short whistlers might be due to

FETs

dispersion, but some whistlers last five seconds so

Q2

MPSA56 transistor

ordinary dispersion is probably inadequate an

explanation. A radio wave can travel a million miles in

U1

LM386 op-amp

five seconds, so to accumulate that much difference in

S1

DPDT toggle switch

arrival times, the signal would have to travel hundreds

(trap)

of millions of miles, assuming a pretty steep dispersion

S2

DPDT toggle switch

curve. More likely, the whistler is an emission from the

(high-pass)

magnetosphere triggered by the lightning pulse. When

conditions are just right, numerous lightning strikes

S3

DPDT toggle switch

combine with numerous reflections to give an eerie

(low-pass)

chorus that sounds a bit like a flock of geese.

B1

9 volt transistor

radio battery

Most people have never heard of Natural Radio

produced by several of natures’s processes, including

J1,J2

1/8 mini phone

lightning storms and aurora, aided by events occurring

jack w/switch

on the Sun. The majority of Earth’s natural radio

J3

SO-238 UHF chassis

emissions occur in the extremely-low-frequency and

jack

very-low-frequency (ELF/VLF) radio spectrum. Whistlers,

P1

PL259 UHF plug

one of the more frequent natural radio emissions to be

heard, are just one of many natural radio “sounds” the

P2

binding post

Earth produces at all times in one form or another, and

(ground)

these signals have caught the interest and fascination of

Misc

PC board, IC

a small but growing number of hobby listeners and

socket, solder, wire,

professional researchers for the past four decades.

antenna, battery

Whistlers are amazing sounding bursts of ELF/VLF

holder

radio energy initiated by lightning strikes which “fall”

Battery clip, hardware,

in pitch. A whistler, as heard in the audio output from a

chassis

VLF or “whistler” receiver, generally falls lower in pitch,

“Natural Radio” is a name sometimes used for describing

from as high as the middle-to-upper frequency range of

radio noise with natural origins, mainly due to but not

our hearing downward to a low pitch of a couple hundred

confined to lightning. At first suggestion, you may think

cycles-per-second (Hz). Measured in frequency terms, a

that listening to lightning crackles would be dull or

whistler can begin at over 10,000 Hz and fall to less than

uninteresting, but electromagnetic radiation from

200 Hz, though the majority are heard from 6000 down

Chapter Fourteen: VLF Radio Receiver lightning can travel great distances and undergo strange to 500 Hz. Whistlers can tell scientists a great deal of

154

Chapter Fourteen: VLF Radio Receiver

the space environment between the Sun and the Earth

(or not-so-near) the lightning storm from which it

and also about Earth’s magnetosphere.

was born!

The causes of whistlers are generally well known

Whistlers are descending tones. Their duration can

today though not yet completely understood. What is

range from a fraction of a second to several seconds,

clear is that whistlers owe their existence to lightning

with the rate of frequency shift steadily decreasing as

storms. Lightning stroke energy happens at all

the frequency decreases. A whistler’s note may be pure,

electromagnetic frequencies simultaneously. The Earth

sounding almost as if it was produced using a laboratory

is literally bathed in lightning-stroke radio energy from

audio signal generator; other whistlers are more diffuse,

an estimated 1500 to 2000 lightning storms in progress

sounding like a breathy “swoosh” or composed of

at any given time, triggering over a million lightning

multiple tones. On occasion, some whistlers produce

strikes daily. The total energy output of lightning storms

echoes or long progressions of echoes, known as “echo

far exceeds the combined power output of all man-made

trains,” that can continue for many minutes.

radio signals and electric power generated from power

Whistlers can occur in any season. Some types are

plants.

more likely to be heard in summer than winter and

Whistlers also owe their existence to Earth’s

vice-versa. Statistically, the odds are especially high

magnetic field (magnetosphere), which surrounds the

for good whistler activity between mid-March and

planet like an enormous glove, and also to the Sun.

mid-April.

Streaming from the Sun is the Solar Wind, which

Whistlers and the sounds of the dawn chorus are not

consists of energy and charged particles, called ions.

heard equally well everywhere in the world. Reception

And so, the combination of the Sun’s Solar Wind, the

of these are poor in equatorial regions, with best

Earth’s magnetosphere surrounding the entire planet,

reception at geomagnetic latitudes above 50°. Fortunately

and lightning storms all interact to create the intriguing

the continental United States and Canada are well

sounds and great varieties of whistlers.

positioned for reception of whistlers and other signals

How do whistlers occur from this combination of

of natural radio.

natural solar-terrestrial forces? Some of the radio energy

Considered by many listeners to be the “Music of

bursts from lightning strokes travel into space beyond

Earth”, whistlers are among the accidental discoveries of

Earth’s ionosphere layers and into the magnetosphere,

science. In the late 19th century, European long-distance

where they follow approximately the lines-of-force of

telegraph and telephone operators were the first people

the Earth’s magnetic field to the opposite polar

to hear whistlers. The long telegraph wires often picked

hemisphere along “ducts” formed by ions streaming

up the snapping and crackling of lightning storms,

toward Earth from the Sun’s Solar Wind. Solar-Wind

which was mixed with the Morse code “buzzes” or

ions get trapped in and aligned with Earth’s magnetic

voice audio from the sending station. Sometimes, the

field. As the lightning energy travels along a field-

telephone operators also heard strange whistling tones

aligned duct, its radio frequencies become spread out

in the background. They were attributed to problems in

(dispersed) in a similar fashion to light shining into a

the wires and connections of the telegraph system and

glass prism. The higher radio frequencies arrive before

disregarded.

the lower frequencies, resulting in a downward falling

The first written report of this phenomenon dates

tone of varying purity.

back to 1886 in Austria, when whistlers were heard on a

A whistler will often be heard many thousands of

22-km (14 mile) telephone wire without amplification.

miles from its initiating lightning stroke—and in the

The German scientist, H. Barkhausen, was eavesdropping

opposite polar hemisphere! Lightning storms in British

on Allied telephone conversations during World War I.

Columbia and Alaska may produce whistlers that are

In order to pick up the telephone conversations, he

heard in New Zealand. Likewise, lightning storms in

inserted two metal probes in the ground some distance

eastern North America may produce whistlers that are

apart and connected these to the input of a sensitive

heard in southern Argentina or even Antarctica.

audio amplifier. He was surprised to hear whistling

Even more remarkably, whistler energy can also be

tones which lasted for one or two seconds and which

“bounced back” through the magnetosphere near

glided from a high frequency in the audio range to a

155

lower frequency where they disappeared into the

seals barking. In fact, it varies constantly. “Hooks,”

amplifier or background noise level. On occasion, the

“risers,” and “hiss” are all part of the dawn chorus, but

whistlers were so numerous and loud that he could not

sometimes these sounds are also heard as solitary

detect any type of telephone.

events. A hook starts out like a whistler but then

abruptly turns into a rising tone. Risers increase in

Later, three researchers from the Marconi Company

frequency from beginning to end. And hiss sounds just

in England reported in 1928 on the work they had done

like its name. Appropriately enough, dawn chorus is

in whistler research. Eckersley, Smith, and Tremellen

best heard around dawn, but it may occur at any time of

established a positive correlation between whistler

the day or night. The dawn chorus is most likely to be

occurrence and solar activity, and they found that whistlers

heard during and shortly after geomagnetic storms.

frequently occur in groups preceded by a loud click.

The time between the click and the whistlers was about

three seconds. They concluded that there must have been

two paths of propagation involved; one for the click

A whistler receiver

which preceded the whistler, and a second, much longer

path, over which the whistler and its echoes propagated.

You cannot easily buy a radio capable of tuning 1 to

Eckersley was able to show in 1931 that Earth’s

10 kHz, but it is possible to build a sensitive receiver to

magnetic field permits a suitably polarized wave to pass

permit you to hear the sounds of natural radio. We will

completely through the ionosphere. This was in

explore what causes these sounds and see how you can

accordance with the magneto-ionic theory. Tremellen

study them yourself.

had on one occasion observed that during a summer

A whistler receiver, even though whistlers and related

thunderstorm at night every visible flash was followed

emissions occur at acoustical frequencies, is a receiver

by a whistler. This served as the first definite evidence

of radio signals. To hear whistlers, you must intercept

of the relationship between lightning discharges and

their electromagnetic energy with an antenna and

whistlers—the click being the lightning discharged

transform it to the mechanical vibrations to which our

which caused the whistler. As the Marconi workers

ears respond.

continued their research, they also discover a new type

of atmospheric which sounded somewhat like the

The “classic” whistler receiving system consists of an

warbling of birds. Since the sound tended to occur

antenna for signal collection, an amplifier to boost the

most frequently at dawn, they gave it the name dawn

signal level, and headphones or a speaker to transform

chorus.

the signal to sound waves. (A magnetic tape recorder

can be substituted for the headphones or speaker.)

L.R.O. Storey of Cambridge University began an

A whistler receiver can simply be an audio amplifier

intensive study of whistlers in 1951. He confirmed

connected to an antenna system. However, powerful

Eckersley’s law which showed that most whistlers

man-made interference immediately above and below

originate in ordinary lightning discharges, and found the

the frequencies of interest tend to seriously overload

path of propagation of the whistler to be along the lines

receivers of this sort and make reception of whistlers

of the Earth’s magnetic field.

and related phenomena difficult.

Other interesting sounds include “tweeks,” which have

To overcome these problems, a good whistler receiver

been described by one listener as a cross between chirping

circuit includes a circuit called a low-pass filter that

birds and a hundred little men hitting iron bars with

attenuates all signals above 7 kHz. This greatly reduces

hammers. The ephemeral “dawn chorus,” is a cacophony

interference from such sources. To escape interference

of sounds that resembles nothing else on Earth.

from AC power lines and other forms of non-natural

Tweeks are abrupt descending notes that resemble

radio noise, the receiver is designed for portable operation

“pings.” They are usually heard at night during the

“in the field” away from such interference sources.

winter and early spring.

A sensitive dual FET whistler receiver is shown in

The dawn chorus has been variously described as

the photo in Figure 14-1, and in the schematic diagram

Chapter Fourteen: VLF Radio Receiver sounding like birds at sunrise, a swamp full of frogs, or in Figure 14-2. The antenna is first fed to an RF filter

156

Chapter Fourteen: VLF Radio Receiver

Front end

Building a whistler

receiver

Before we start building the Whistler receiver,

you will need to locate a clean, well lit and well

ventilated area. A workbench or large table top to

spread out all you diagrams, components and tools for

the project. First, you will need a small pencil tipped

27 to 33 watt soldering iron, a spool of 22 ga. 60/40

tin/lead solder, and a small jar of “Tip Tinner.” “Tip

Tinner” is a soldering iron tip cleaner/dresser and is

available at your local Radio Shack store. You will

also want to locate a few small tools such as a pair of

Headphone amp

Filters

end-cutters, a pair of needle-nose pliers, a pair of tweezers

and a magnifying glass. Look for a small flat-blade

Figure 14-1

VLF whistler receiver

screwdriver as well as a small Phillips screwdriver to

round out your tools for the project. Next locate all the

components for the Whistler project as well as all of the

which is composed of resistors R1 through R4 and

diagrams including the schematic, parts layout diagram

capacitors C1 through C3. This filter only allows the

and the necessary charts and tables and we will begin.

desired frequencies to be sent to the next section of the

In order to construct a stable well performing radio

receiver. The RF filter is next fed to the 60 Hz filter or

receiver, it is recommended practice to build the

“trap” which filters out 60 Hz power line frequencies

Whistler receiver on a printed circuit board, with large

before the RF signals are amplified. The 60 Hz filter

ground plane areas. You will need to use good RF

can be switched in and out of the circuit with switch

building practices, such as keeping leads as short as

S1:a. The dual matched FET transistor Q1 along with

possible, clean solder joints, etc. With your circuit board

transistor Q2 are used to amplify the RF signals of the

in hand we will begin building the circuit.

desired band of frequencies. The amplified signals are

then fed to the input of a set of selectable filters which

Take a look at the schematic diagram and you will

can be switched in and out of the circuit. Toggle switch

notice that there are dotted or dashed lines. These dashed

S2 is used to switch in the high-pass filter circuit, while

lines represent shielded compartments on the circuit

switch S3 is used to switch-in the low-pass filter. You

board. These shielded areas are used to separate different

can select either or both filters if desired.

portions of the circuit from one another. You can create a

shielded area by soldering a vertical piece of scrap

The output of the low-pass filter circuit is coupled to

circuit board material onto the circuit board ground

the final audio amplifier stage via capacitor C17.

plane areas on the circuit board. You could also

Potentiometer R12 controls the audio level entering the

modularize the circuit building three small circuit

LM386 audio amplifier at U1; also note that R12 also

boards, one for the RF filter and “trap” circuit, one for

contains a switch S5, which is used to supply power to

the high-pass and low-pass filter, and a third board for

the LM386 audio amplifier. The output of the LM386 is

the audio amplifier and power circuit. Small metal shield

coupled to an audio output jack via capacitor C20. Note

covers could be built using scrap circuit board material.

that capacitor C18 is coupled to a recorder output jack

to allow a chart recorder or analog to digital converter

First, you will need to locate the resistors for the

to be used to monitor and record the output from the

project, and you will also want to refer to the resistor

whistler receiver. The whistler receiver is powered from

color code chart in Table 14-1, which will help you to

a 9 volt battery for both stationary and field receiving

identify each of the resistors. Resistors generally have

applications.

three or four color bands which are used to denote the

157

C h a p t e r F o u r t e e n : V L F R a d i o R e c e i v e r 158

Antenna

R1

R2

R3

R4

Ground

R17

P1

+

S4

C1

C2

C3

9 V

+

+

C21

C23

C22

C24

60 Hz trap

R5

S1:a

S1:b

C6

C5

C7

2

High pass

Low pass

R15

R10

3

C15

C18

C19

J1

S2:a

L4

S3:b

R6

1

S2:b

S2:a

S5

R14

Record

R9

Q1:A

Q2

a

R11

C16

Phone

b

R12

power

2

C11

1 8

C13

C8

c

6

U1

3

C20

2

5

J2

Q1b

C12

L5

R13

+

1

C14

3

7

4

C21

Phones

R7

C9

C17

+

L2

L3

R16

C10

R8

Figure 14-2

FET VLF receiver schematic. Courtesy of Eric Vobel

Chapter Fourteen: VLF Radio Receiver

Table 14-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

resistor’s value. The first color band will be closest to

non-electrolytic capacitors are the small types such as

one edge of the resistor. The first color band represents

ceramic disks, mylar or polyester types. These small

the first digit of the value. Resistor R1, for example, is a

capacitors may have their actual value printed on them,

10k ohm resistor. Its first color band would be brown (1),

or if the capacitors are very small may instead have a

the second color band would be black (0) and the third

three-digit code printed on them. Refer to the chart in

color band which denotes the resistor’s multiplier value

Table 14-2, which will help you identify these capacitors.

would be orange or (000), so 10,000 or ten thousand

A .001 µF capacitor, for example, would have (102)

ohms. A fourth color band represents the resistor’s

marked on the body of the device to denote its value

tolerance value. The absence of a fourth color band

of .001 µF. Electrolytic capacitors are generally the

denotes a 20% tolerance, while a silver band represents

larger capacitors with polarity marking on them.

a 10% tolerance and a gold denotes a 5% tolerance

You will find either a black or white color band on them

resistor. Use the color code chart to identify resistors

or a plus (+) or minus (−) marking on them. Electrolytic

R1, R2 and R3. When you are confident that you know

capacitors have polarity, so this means that you have to

the color codes and can identify these resistors, you can

orient them correctly while installing them in order for

go ahead and solder these resistors onto the circuit

the circuit to work properly. Reversing electrolytic

board. Use your end-cutters to cut the excess

capacitors can often cause the circuit to malfunction,

component leads flush to the edge of the circuit board.

and it can destroy the component and/or the circuit

Now locate another grouping of resistors and install

itself, so be careful when installing them. Refer to the

them to the circuit board, then solder them in place on

schematic and the parts layout diagram when installing

the PC board. Remember to trim the extra component

electrolytic capacitors.

lead lengths from the PC board. Install the remaining

Let’s begin installing the capacitors now. Try and

resistors onto the circuit board, until all have been

separate the electrolytic capacitors from the other types

mounted to the board, solder them in place and trim the

of capacitors. Locate a few of the non-electrolytic

leads as necessary.

capacitors, identify them and install a few of the

Next, we are going to install the capacitors for the

capacitors on the circuit board. Go ahead and solder

Whistler receiver. Capacitors come in two major

these capacitors onto the PC board, once you are sure

types, i.e. electrolytic and non-electrolytic. Generally the

you have correctly identified them. Trim the excess

159

Table 14-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 Pf

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Fourteen: VLF Radio Receiver 820 pF

Ceramic

821

2

Mylar

205

160

Chapter Fourteen: VLF Radio Receiver

component leads from the PC board. Install a few more

diagrams when installing the transistor and FET.

non-electrolytic capacitors and solder them to the board,

Installing the FET and transistor incorrectly will prevent

remember to cut the extra leads from the board. Install

the circuit from working correctly and may damage the

the remaining non-electrolytic capacitors to the circuit

component as well, so be careful when installing the

board and solder them in place.

FET and transistor.

Next, locate the electrolytic capacitors and we will

The receiver has a single integrated circuit at U1, an

install them on the PC board. Refer to the schematic

LM386 audio amplifier IC. As an insurance policy

and parts layout diagrams to make sure you can orient

against a possible circuit failure in the present or

the capacitors correctly before soldering them. Place a

possible future date, it is recommended that you use an

few electrolytic capacitors on the board and solder them

integrated circuit socket. Integrated circuit sockets will

in, trim the excess leads as necessary. Add the

usually have a notch or cut-out at one end of the socket;

remaining electrolytic capacitors on to the PC board and

this is supposed to represent pin 1 of the IC socket. You

solder them in place.

will have to align the socket correctly so that pin 2 of

The Whistler receiver also has a number of coils in

the IC socket connects to the ground bus. Note that

the circuit, most of them are low cost and readily

pin 1 is not used in this application. When installing the

available from Mouser Electronics, see Appendix.

IC into the socket, you will note that the IC itself will

Identify the coils for the project and place them in their

have either a small indented circle, a cut-out or a notch

respective locations on the PC board. Now, solder them

at one end of the plastic IC body. Pin 1 of the IC is just

in place and remember to trim the excess component

to the left of the notch. Insert the IC into the socket

leads flush to the edge of the circuit board.

making sure pin of the IC is aligned with pin of the

socket.

Looking at the circuit you will notice three transistors,

more correctly one dual FETs and one conventional

Take a short break and when we return we will check

transistor. Before we go ahead and install the

over the printed circuit board for “cold” solder joints

semiconductors, take a quick look at the semiconductor

and possible “short” circuits. Pick up the PC board with

pin-out diagram shown in Figure 14-3. The FETs are

the foil side facing upwards toward you. First we will

very sensitive to static electricity damage, so be

inspect the PC board for possible “cold” solder joints.

extremely careful when handling them, use a grounded

Take a look at all of the solder joints. All the solder joints

anti-static wrist-band. The FETs have three leads much

should appear to look clean, shiny and bright, with well

like a regular transistor but their pin-outs are a bit

formed solder connections. If any of the solder joints

different. An FET will usually have a Drain, Source and

appear dull, dark or “blobby,” then you should un-solder

Gate lead; see pin-out diagram for each particular FET,

and remove the solder from the joint and re-solder the

when installing them on the PC board. The conventional

joint all over again, so that it looks good. Next, we will

transistor at Q2 is a PNP type which has a Base, Collector

inspect the PC board for possible “short” circuits. “Short”

and Emitter lead, once again refer to the transistor

circuits can be caused by small solder balls or blobs

pin-out diagram, the schematic and parts layout

which stick to the underside of the board. Many times

rosin core solder leaves a sticky residue on the PC

board. Sometimes “stray” component leads will

adhere to the underside of the board and often they can

1

8

1

8

1

8

1

8

form a bridge across the PC traces on the PC board

2

7

2

7

3

6

3

6

causing a “short” circuit, which can damage the circuit

4

5

4

5

upon power-up, so be careful to remove any

LM386

SiliconixU401

EBC

component leads or solder blobs from the underside of

the board.

The VLF Whistler receiver was housed in a metal

MPSA56

chassis box to prevent “stray” RF from affecting the

NTE159

circuit operation. The main circuit board can be

Figure 14-3

Semiconductor pin-outs

mounted to the bottom of the enclosure with 1/8′′

161

plastic standoffs. The 60 Hz “trap” filter switch, the

in length connected instead of the vertical antenna. Wire

high-pass filter and low-pass filter switches, along with

antennas should be insulated and supported off the

the power on-off switch, were mounted on the front

ground as high as you can place them. The performance

panel of the chassis box. The headphone power

of a wire antenna improves the more you can get it in

amplifier power switch, the headphone jack and volume

the clear and the more vertically it can be positioned. If

control at R13 were also mounted on the front panel of

you do use a wire antenna, you may have to reduce the

the chassis box. The SO-238 antenna jack, the 1/8′′

value of the input resistor R1 for best results.

record jack and the ground binding post were all

The whistler receiver also needs a ground connection,

mounted on the rear panel of the chassis box. A 9 volt

also called a counterpoise. A simple but often effective

battery holder was used to secure the battery to the left

ground can be provided by your body in contact with

rear corner of the chassis box. Once the circuit has been

the ground terminal (BP2). I have used an improvised

mounted in the selected chassis, you can move on to

finger ring attached to a wire connected to the ground

applying power and testing the VLF receiver. Connect a

terminal. Other places to make a ground connection

fresh 9 volt battery to the VLF receiver, connect a pair

include car bodies, wire fences, or other large metal

of headphones and a whip antenna to the antenna

objects not connected in any way to an AC power

terminals. Turn the power switch to the “ON” position

circuit. Another approach is to use short sections of

and you should hear a hissing sound from the

copper tubing as ground stakes which can be driven

headphones. If the receiver is totally quiet and you hear

into the ground and connected to your receiver. Try

nothing, you have a problem! First, you will need to

several different grounding schemes to see which one

disconnect the battery, the headphones and the antenna,

provides the quietest reception. Don’t be too surprised,

and you will need to carefully examine the circuit

however, to discover that you wind up having to still

board. The most common cause for circuit failure is

make body contact with the ground terminal for quietest

improper installation of electrolytic capacitors and

reception!

diodes. Remember that these components have polarity

and it must be observed for the circuit to work correctly.

The prototype receiver, with a whip antenna, was

Look over the circuit very carefully. It is often advisable

mounted on a piece of wood approximately 2′′ × 60′′.

to have a second pair of eyes. Have a knowledgeable

You can install the antenna at one end of the long

electronics friend help you examine the circuit board for

rectangular piece of wood (it can be mounted on a

mistakes. Another cause for possible errors are the

bracket or just taped on) and the receiver can be

incorrect placement of resistors. Often colors are

mounted at the other end of the piece of wood, about

mistaken and resistors are installed in the wrong

one foot down from the antenna using duct tape, two-

location. Another possible problem can be the

sided foam tape or a mounting bracket. A length of wire

installation of the semiconductors, namely in this circuit

was run from the receiver’s ground terminal down the

the transistors or FETs. Check the manufacturer’s pin-out

wood and taped in place at several places. Now I had a

diagrams for the particular device and carefully

handy walking stick that was easy to carry and use!

re-examine the installation. Hopefully at this point you

The base can be stuck into any convenient hole, jammed

have found your error and corrected it and you can then

into a rock pile, clamped onto a fence or vehicle, or

re-connect the battery, antenna and headphones and

even held by hand.

re-test the VLF receiver to make sure it is now working.

For the best chance of hearing whistlers and related

phenomena, you will have to put some distance between

the whistler receiver and the AC power grid. The bare

minimum distance is about one quarter mile from any

Using your VLF receiver

AC power line; the more distance you can put between

the receiver and AC power lines, the better. You’ll need

The whistler receiver works best out doors in open

to do some exploration to discover quiet sites near you.

areas, with a vertical antenna of roughly 3 to 12 feet in

Once you arrive at a potential listening site, set up your

height. It can also be used in wooded or obstructed

receiver, put in a ground connection, and see what

Chapter Fourteen: VLF Radio Receiver areas with wire antennas between roughly 50 to 200 feet happens. What you will hear depends to some extent

162

Chapter Fourteen: VLF Radio Receiver

on the time of day, but you can always expect some

their electrical and ignition systems. And if you have a

sharp, crackling static. The intensity and volume of this

digital watch, keep it away from the antenna or you’ll

static will depend on propagation conditions and where

be listening to it instead of whistlers!

thunderstorms are in relation to your location. Chances

Anything you hear other than whistlers and

are that you’ll also hear some power line hum, but

related phenomena or OMEGA signals are likely to be

hopefully it won’t be very loud. If your listening site is

the result of extraneous signals “overloading” your

too noisy, you need to try another listening site.

receiver. Burbling sounds (possibly mixed with OMEGA

If your ears have good high frequency response, you

tones) are caused by military signals in the 15 to 30 kHz

will probably hear a continuing sequence of one-second

range, perhaps overloading the receiver. A “ticking”

tones. These are from the OMEGA radio-navigation

sound at a 10 Hz rate is from Loran-C radio-navigation

system. OMEGA is transmitted from 10 to 14 kHz, and

signals at 100 kHz. In general, don’t be surprised if you

OMEGA transmitters are very powerful. You may also

experience “overloading” from transmitters operating

hear anything that can produce an electrostatic discharge,

on any frequency if they are within sight of the

particularly if the humidity is low. These miscellaneous

location where you’re using your whistler receiver!

noise sources can include wind noise, the buzz of insects

Table 14-3 illustrates some very low frequency stations

flying near the antenna, dry leaves or grass moving, and

around the world that broadcast low frequency signals,

even the electrostatic charges that build up on your

these signals are located at the upper edge of the VLF

clothing. Passing vehicles will often produce noise from

receiver’s range.

Table 14-3

Very low frequency radio stations

Site

ID

Frequency kHz

Power KW

Cutler, ME

NAA

24.0

1000

Jim Creek, WA

NLK

24.8

250

Lualualei, HI

NPM

21.4

566

LaMoure, ND

NML4

25.2

Aquada, Puerto Rico

NAU

40.75

100

Keflavik, Iceland

NRK

37.5

100

Niscemi, Italy

39.9

25

Harold E. Holt, Australia

NWC

19.8

1000

Rhauderfehn, Germany

18.5

500

Rosnay, France

HWU

15.1

400

St. Assie, France

FTA

16.8

23

Bombay, India

15.1

Tavolara, Italy

ICV

20.27

43

Ebino Huyshu, Japan

23.4

Noviken, Norway

JXN

16.4

45

Arkhanghelsk, Russia

UGE

19.4

150* input pwr

Batumi, Russia

UVA

14.6

100* input pwr

Kaliningrad, Russia

UGKZ

30.3

100* input pwr

Matotchkinchar, Russia

UFQE

18.1

100* input pwr

Vladivostok, Russia

UIK

15.0

100* input pwr

Anthorn, United Kingdom

GQD

.019

42

163

recorder away from the receiver to avoid picking up

Time of listening

motor noise.

After returning home with your recording, if your

Most of the VLF signals, such as clicks, pops, and tweeks,

receiver was out in the field, you can “play” your

can be heard almost at any time of the day or night.

recording back into the sound card of your personal

Whistler occurrence is a function of both thunderstorm

computer using an FFT or DSP sound recording program

occurrence and propagation conditions through the

to analyze the recording. For those who are going to use

ionosphere. The rate is higher at night than during the

their whistler receiver as a stationary receiver at home,

day because of the diurnal variation in the D-region

you could use your PC to record on a continuous basis.

absorption, which is highest when the Sun is above the

Audio recording and FFT programs are available on the

horizon. At night, the D-layer does not exist since it is

Internet for free. Good luck and happy exploring!

ionized by solar ultraviolet rays. The whistler rate, or

the number of whistlers heard per minute, has a marked

Additional notes

dependence on sunspot activity, the rate increasing with

the sunspot number. Whistlers are heard only when

You can view spectrograms of whistlers as well as hear

sufficient ionization exists along the path to guide the

excellent recordings of many more whistlers than

waves along the Earth’s magnetic field. This ionization

we used in generating the audio clip for this article,

is assumed to be supplied from the Sun during a solar.

courtesy of NASA: http://image.gsfc.nasa.gov/

To hear a whistler or other signals such as dawn chorus,

poetry/inspire/advanced.html

you will no doubt have to get away from the power

A free Fast Fourier Transform (FFT) Waveform

line and industrial noise. The listening time for these

Analyzer program and an Audio Waveform

signals will be from near local midnight to early

Generator program can be downloaded for use on

morning hours.

your own computer at:

FFT discussion:

http://www.dataq.com/applicat/articles/an11.htm

Observing and

Some US Government agencies doing whistler

recording hints

research are:

NASA’s Godard Space Flight center invites participation

Remember the best location to observe VLF signals is

in a program called “INSPIRE” (an acronym for

out in the countryside, in an area where few cars or

Interactive NASA Space Physics Ionosphere Radio

trucks are likely to pass. You will want to get as far

Experiments) http://image.gsfc/poetry/inspire

away from power lines as possible for optimum results.

NOAA: http://ngdc.noaa.gov/stp/stp.html

The lower the power line noise is, the stronger the VLF

http://www.ngdc.noaa.gov/stp/stp.htm

emission signals will be.

gopher://proton.sec.noaa.gov

Some whistlers are related phenomena and so

Some of the university labs involved with

short-lived and impossible to predict that you might

whistlers are:

want to consider using a tape recorder to record the

University of Alaska Geological Institute

signals in the field unattended. Take a portable,

University of Iowa: http://www-w.physics.uiowa.edu/

battery-operated, cassette tape recorder with you and

~/jsp/polar/sounds/whistlers.html

use a long audio cable to run to the tape recorder from

Stanford University: http://www.stanford.edu/~vlf/

the audio output of the VLF receiver. Any tape recorder

Science/Science.html

with an external microphone input can be used. Best

[An excellent site, but I could only access it via the

results are obtained with a recorder which has no ALC

“Google” search engine]

or automatic level control. The VLF receiver shown has

UCLA: http://www.physics.edu/plasma-

an output jack which can be coupled to a recorder input

exp/Research/TransportWhistlers

Chapter Fourteen: VLF Radio Receiver for field recording. You may have to place the tape Kyoto University, Kyoto, Japan

164

Chapter 15

Induction Loop Receiving System

C6

2200 µF, 35 volt

Parts list

electrolytic capacitor

U1

TDA2002/3 6 to

Induction Loop

10 watt audio

Transmitter I

amplifier module

TX

Mono amplifier or

HS

heatsink for U1

receiver – 5–10 watts

L1

loop coil (see text)

output

Misc

PC board, wire,

R1

10 ohm 10 watt

hardware, chassis, etc.

10% resistor

Induction Loop

L1

loop coil around

Receiver

room (see text)

R1

1 megohm 1/

Induction Loop

4

watt,

5% resistor

Transmitter II

R2

10k ohm 1/

R1

10k ohm

4

watt,

5% resistor

potentiometer chassis

mount

R3

1000 ohm

potentiometer (tone)

R2

220 ohm 1/4 watt

resistor, 5%

R4

470 ohm 1/4 watt,

(red-red-brown)

5% resistor

R3

2.2k ohm 1/

R5

10k ohm

4

watt,

5% resistor

potentiometer (volume)

(red-red-gold)

R6

10 ohm, 1/4 watt,

R4

1 ohm 1/

5% resistor

2

watt,

5% resistor

C1

39 nF, 35 volt

(brown-black-gold)

mylar capacitor

R5

10 ohm 10 watt,

C2

1 µF, 35 volt

10% resistor

electrolytic capacitor

C1

10 µf, 25 volt

C3,C7

.1 µF, 35 volt

electrolytic capacitor

disk capacitor

C2,C5

100 nF, 35 volt

C4

4.7 nF, 35 volt

poly capacitor

poly capacitor

C3

100 µF, 35 volt

C5

10 µF, 35 volt

electrolytic capacitor

electrolytic capacitor

C4

470 µF, 35 volt

C6

220 µF, 35 volt

electrolytic capacitor

electrolytic capacitor

165

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Q1

BC548 transistor

is connected to a sound source such as a TV, a radio, a

public address system or a dedicated microphone. It

U1

LM386 audio

then amplifies this sound signal and sends it out, in the

amplifier IC

form of an alternating current, through the loop. The

L1

800 turns on a

loop itself consists of insulated wire, one turn of which

9 × 70 mm ferrite rod

is placed around the perimeter of the room in a simple

(see text)

loop system. When the alternating current from the

S1

SPST on-off switch

amplifier flows through the loop, a magnetic field is

B1

9volt transistor

created within the room. The magnetic field “induces”

radio battery

the signal into the Induction loop coil in the induction

receiver unit.

PH

8 ohm headphones

In the portable induction receiver, the induction coil

Misc

PC board, wire,

picks up the induced signal from the transmitting loop

1/8” phone jacks,

coil. The fluctuations in the magnetic field are converted

battery clip, case

into alternating currents once more. These are in turn

Induction loop technology has been around for many

amplified and converted by the induction loop receiver

years, for use with the hearing impaired. Induction loop

into sound. The magnetic field within the loop area is

communication systems were originally designed to

strong enough to allow the person with the hearing aid

provide assistance in the school classrooms for the deaf,

or Induction Loop Receiver to move around freely in

but today induction loop communications technology is

the room and still receive the sound at a comfortable

now used for many other applications, such as museum

listening level.

displays, theater communications, mine and cave

Many modern day hearing aids incorporate a

communication systems, and signal tracing. Induction

telecoil into the hearing device. So if a hearing aid user

loop systems have been installed in churches, public

switches to the T or MT position on their hearing aid,

halls and auditoriums, schools, lecture halls, cinemas,

the telecoil in the hearing aid picks up the induced

service counter windows, drive-thru order and pick up

signal from an induction loop transmitter and amplifies

windows, information kiosks, offices, airports, train

the signal for the hearing aid user to hear. This is a

stations, parks, tour and guide buses, automobiles,

convenient feature for hearing aid users, in classrooms,

boats, riding academies, and homes.

churches, and museums with induction coil

Induction loop amplification operates on the basic

transmitters.

principle of electronics called magnetic induction.

The listener can receive an audio signal without being

When an electrical current is amplified and passes

physically or electrically connected to the loop, so in

through a loop of wire, a magnetic field is generated

effect induction loop transmission is a form of wireless

around the wire. The field varies in direct proportion to

telephony. The listener receives the sound in one of two

the strength and frequency of the signal being

ways; either through the use of the T-coil or telephone

transmitted. When another wire is placed close to the

switch on a hearing aid instrument or through an

field of the first wire, an identical electrical current is

induction receiver that can work with earphone, which

induced within it. The second current can be amplified

we will discuss in our project.

and converted into an exact duplicate of the original

The basic induction loop system consists of a

sound signal.

“transmitter” section and a “receiver” section, as shown

In technical language, a current is said to be

in Figure 15-1. The “transmitter” section consists of a

“induced” in the second wire. Hence the term

microphone or signal source, an audio amplifier to

“induction.” In an induction loop system, the induction

boost the signal, and a large loop or wire around the

loop coil in the transmitter sends an electromagnetic

room or listening area. The “receiver” section

signal, which is “induced” to the receiver’s induction

consists of a smaller loop coil, an audio amplifier

loop coil in the receiving unit. An Induction Loop

which boost the incoming audio and a pair of

Chapter Fifteen: Induction Loop Receiving System System consists of an amplifier and a loop, the amplifier headphones.

166

Chapter Fifteen: Induction Loop Receiving System

Tx

Rx

Transmitter

Receiver

Audio

Audio

amplifier

amplifier

Microphone

Large loop

Small loop

coil

coil

Figure 15-1

Induction loop communications system block diagram

If you wanted to construct your own amplifier

specifically for an induction loop audio system, you

“Transmitter” loop unit

could utilize the 6 to 10 watt audio amplifier shown in

Figure 15-3. In order to drive an induction loop, you

You can easily build your own induction loop

would need an amplifier with at least about 5 watts of

communication system. First we will begin by

power or more to have a workable system. The

describing the “transmitter” section of the system, as

amplifier shown in this diagram would work just fine

shown in Figure 15-2. In its simplest form an induction

for driving a large loop coil. An audio input signal is fed

loop “transmitter” can consist of a mono or stereo Hi-Fi

into the audio input section at the point marked (A) on

receiver, a resistor and a large loop coil placed around

the schematic. Your audio source could be adjusted via

the perimeter of a house, room, or your easy chair. If

the potentiometer at R1. Note, that you may need an

you have a stereo receiver with a speaker output A-B

additional pre-amp ahead of the amplifier if you use a

switch, you can select the (B) output for your induction

low output microphone. You can feed a radio or TV

loop system. You would place an 8 ohm, 10 watt

signal directly into the potentiometer at R1 to drive the

resistor across the output of the left channel’s output

induction loop “transmitter.” The audio amplifier

and then place an 8 ohm, 10 watt resistor in series with

module shown is an 8 watt National Semiconductor

a large loop coil as shown. When you wanted to use the

LM2002 module, but you could also use a higher power

induction loop system, you would switch to the (B)

module such as their LM2005. The output of the audio

speaker output; it’s that simple.

amplifier is wired in series with an 8 to 10 ohm, 10 watt

L1

Tx

5–18 watt

R1

audio amplifier

or

Loop coil

stereo receiver

1-channel

Figure 15-2

Induction loop transmitter I

167

L1

+6 –12 V DC

Audio

+

input

C2

C3

5

(A)

C1

+

R1

+

C6

R5

1

4

+

U1

Loop coil

–

R2

C4

C5

+

2

3

R3

R4

Figure 15-3

Induction loop transmitter II

resistor in order to drive the coil. This resistor also

at 10 watt minimum. There’s another and simpler

protects the output of the audio amplifier.

approach: I have a coil built into my favorite chair. It’s

The inductive loop is a winding of wire through

only 18′′ in diameter, but includes 120′ of 28 gauge wire

which an audio signal passes, which creates a field

(0.071 ohms per foot). That’s about 25 turns of that

within which the audio signal can be detected by

relatively thin wire.

appropriate equipment, either a telecoil in a hearing aid

Another approach to constructing a large loop is to

or an induction loop receiver. The loop coil is basically a

take a long length of 25 pair telephone cable ‘Inside

simple 4 or 5 turn loop placed around the room fed from

Wire’ that’s long enough to go around the perimeter of a

an audio amplifier. The loop then converts the sound to a

room. Then get a 66 block (or some other kind of punch

magnetic field that can be received by a second loop coil

down block) and punch down the wires so they connect

and amplified. Note that more turns in the transmission

in a multiple turn loop. In this way you can add or

coil result in a stronger transmitted signal. The loop

subtract turns as you wish if you need that later. You

should have a DC impedance of at least 8 ohms, or you

could tack this “telephone” cable to the ceiling of the

can add a resistor in series with the coil to reach 8 ohms.

basement underneath the room you choose.

Pick a path around the room on the ceiling, or under

Connect either end of the loop coil wire to

the carpet. A room measuring 15′ × 20′ will have a

the plus (+) or red terminal and the other end to the

perimeter of 70′, which will require a minimum of four

minus (−) black terminal, on the audio amplifier’s

complete turns of 22 gauge wire, six turns of 20 gauge

speaker terminals. Most amplifiers or stereo receivers

wire, or nine turns of 18 gauge wire. Pick a path around

have SPEAKER A and B switches; put your coil circuit

the room near the ceiling, and wind (or hang) your

on the unused output (B). Remember to place an 8 to

“coil,” or loop, starting and ending at the amplifier. If

10 ohm, 10 watt resistor in series with the speaker

the back of your amplifier says something like “8 ohms

output and the coil loop windings.

minimum,” double the required wire length (load). Buy

120% of the wire you’ll need to ensure that you can

complete the loop. You should add a power resistor to

ensure an appropriate load and reduce wire length, but

“Receiver” loop unit

the amplifier output will be divided between the loop

and the resistor, proportionately, which means less

The induction loop receiver, shown in the photo

radiated energy. This solution requires a lot of energy

Figure 15-4 and the schematic diagram in Figure 15-5,

Chapter Fifteen: Induction Loop Receiving System so try not to compromise. If required, get 4 ohms is very sensitive and can be the basis for a monaural

168

Chapter Fifteen: Induction Loop Receiving System

induction loop wireless headphone system. The

core coil with superb results but the 2′′ diameter was

induction coil receiver is used inside the area of

just too big for this application. The induction receiver

transmission loop. The receiver coil at L1 consists of

develops a 1–2 mV signal across its internal coil from

800 turns of #26 ga. enamel wire wound on a

the fluctuating magnetic field. Transistor Q1 provides

9 × 70 mm ferrite core.

pre-amplification to drive a headphone amplifier. The

tone at R3 control varies the amount of gain in the high

Another approach to constructing a small loop coil

frequencies. Capacitors C1 and C2 block AC hum

for your inductive loop receiving coil is to obtain a

(C2 also blocks DC to the amplifier input). C3 functions

“telephone pickup coil” if available or a suitable coil

as a low-pass filter to prevent oscillation. The output of

from some other device. The coil in the prototype was

the volume control at R5 is fed to the input of an LM

salvaged from a surplus 24 volt relay. Actually, two

386 audio amplifier IC. In this configuration the

relays were needed since the first was destroyed in the

amplifier has a gain of 200. Capacitor C7 and R6 form

attempt to remove the surrounding metal so that a single

the output “boost” circuit which drives the output to the

solenoid remained. Epoxy putty was used to secure the

speaker through C6. The output of the LM385 at pin is

thin wires and the whole operation was a bit of a

used to drive an 8 ohm headphone. The induction loop

challenge. A reed relay coil will give reduced sensitivity

receiver circuit can be powered from a 9 volt DC power

but would be much easier to use. The experimentally

supplies or batteries.

inclined might try increasing the inductance of a reed

relay by replacing the reed switch with soft iron. Avoid

Are you ready to begin constructing the induction

shielded inductors or inductors with iron pole pieces

receiver circuit? First you will need to locate a clean,

designed to concentrate the magnetic field in a small

well lit work table or work bench. You will want a

area or confine it completely (as in a relay or

large table so you can spread out all the components,

transformer) unless you can remove the iron. The

the diagrams and tools that you will need to build the

resulting coil should be a simple solenoid like wire

project. Next you will need to locate a small pencil

wrapped around a nail. Don’t try to wind your own—it

tipped 27 to 33 watt soldering iron and some

takes too many turns. Evaluate several coils simply by

60/40 tin/lead rosin core solder for the project.

listening. Coils with too little inductance will sound

Try and locate a small container of “Tip Tinner,” a

“tinny” with poor low frequency response, and other

soldering iron tip cleaner/dresser which conditions the

coils will sound muffled, especially larger iron core

soldering iron tip; this is available from your local

coils. This prototype was tested with a large 100 mH air

Radio Shack store. You should also locate a

few small hand tools such as a pair of end-cutters,

a pair of needle-nose pliers, a pair of tweezers,

a small flat-blade and a Phillips screwdriver and a

magnifying glass.

The induction loop receiver prototype was

constructed on a small glass-epoxy circuit board which

measured 21/4′′ × 3′′. A circuit board makes for a more

reliable and professional circuit. Place all the diagrams

in front of you on the work table along with all of the

components for the induction loop receiver and we will

begin building the project.

The induction loop receiver project contains about

four resistors and two potentiometers. Locate the

resistors using the color chart in Table 15-1, this will

help you identify each of the resistors. Place the

resistors into their respective locations on the circuit

board, then solder them in place on the PC board.

Figure 15-4

Induction receiver

Locate your end-cutters and trim the excess component

169

B1

–

+

+9 V

S1

R2

R1

C3

C1

Q1

C5

+

L1

6

C4

1

+

C6

R5

8

+

C2

3

5

U1

+

–

R4

2

4

C7

R6

R3

Phones

Figure 15-5

Induction loop receiver schematic

leads, by cutting them flush to the edge of the circuit

installed correctly the circuit will not work properly and

board. Potentiometer R3 is a CP board mounted type,

may be damaged upon power-up. So you will want to

you can go ahead and install it on the board and then

install them correctly the first time through.

solder it in place; you can remove any excess leads if

Note, there are a number of capacitors in this

necessary.

project, and in looking over the schematic, you will

Next we are going to move to installing the capacitors

notice that a few of the capacitors will have polarity

for the project. There a two distinct types of capacitors—

marking on them. These capacitors are electrolytic

small ceramic, mylar or polyester capacitors and larger

types and you must observe the polarity when installing

electrolytic types. The small capacitors will most likely

them on the circuit board in order for the circuit to

have a three-digit code stamped on them and not their

work properly. Electrolytic capacitors will have either a

actual value, since often the capacitor body is

white or black band at one side of the capacitor body or

very small. Refer to the chart shown in Table 15-2,

they may be marked with a plus (+) or minus (−)

which illustrates the capacitor codes. You can search

marking on the capacitor body and this denotes the

through the parts pile and try and identify the capacitors

polarity. Refer to the schematic and parts layout

against the code chart and place the correct value into its

diagrams when installing electrolytic capacitors in order

respective location on the circuit board. After all of the

to install them correctly with respect to their polarity

small capacitors have been placed on the PC board, you

markings.

can solder them in place. Remember to cut the excess

Before we go ahead and install the semiconductors,

leads from the components. Now, locate the larger

take a brief look at the diagram depicted in Figure 15-6.

electrolytic capacitors and place them in front of you and

The semiconductor pin-out diagrams will help you

determine where they will go on the circuit board. Once

orient the semiconductors when building the induction

you are certain where the capacitors should be placed on

receiver. The induction loop receiver also incorporates

the board, you should take another look to make sure

one transistor at Q1 which is connected to R1/R2 and

that you have installed the capacitors correctly with

R4 and C2. Transistors generally have three leads

Chapter Fifteen: Induction Loop Receiving System respect to its polarity. If an electrolytic capacitor is not protruding from the bottom of the body. A Base lead,

170

Chapter Fifteen: Induction Loop Receiving System

Table 15-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

a Collector lead and and an Emitter lead. Referring to

Orient the IC correctly into the socket, while referring

the schematic you will note that the vertical line on the

to the schematic and layout diagrams. Place the IC into

transistor symbol is the Base lead, while the Collector

the socket.

lead is connected to the junction of R1 and R2.

The receiver loop coil at L1 can be either the

The Emitter lead has the small arrow pointing

800 turn coil wound on a plastic form, an old “high”

downwards which connects to the junction of C2 and

impedance relay, or one of the black plastic suction

R4. Refer to the actual transistor pin-out diagram to

cup-telephone pickup devices. Solder the coil in place

see where each lead exits the transistor case. Generally

between the circuit ground and the capacitor at C1. You

small plastic TO-92 transistor case bodies will have all

could also elect to use a second 1/8′′ phone jack to allow

three leads in-a-row with the Emitter at one end, the

the coil to be plugged into the circuit using a 6′′ to

Base lead in the center, and the Collector lead at the

8′′ length of coax cable.

opposite end of the device.

The volume control used for the prototype was a

The induction loop receiver has one integrated circuit

chassis mounted miniature 10k ohm potentiometer.

at U1, this is an LM386 audio amplifier chip, which has

We used a mini 1/8′′ PC style phone jack on the

eight leads in a dual in-line package. Prior to installing

circuit board at the output of the audio amplifier at C6;

the IC, you should install a good quality IC socket. An

this will allow you to plug in a headphone for

IC socket is good insurance in the event of a possible

listening.

circuit failure at some point in time. Since most people

cannot successfully un-solder an integrated circuit

Take a short well deserved rest and when we return

without damaging the PC board, an IC socket makes

we will check the circuit board for possible “short”

good sense. Place the IC socket on the circuit board and

circuits and “cold” solder joints. Pickup the circuit

solder it in place on the PC board. Locate the LM386

board with the foil side of the circuit board facing

and take a look at the chip. You will note that the IC

upwards toward you. Look the circuit board over

package will have either a cut-out, a notch or small

carefully to see if there are any “cold” solder joints. The

indented circle at one end of the IC package. Pin 1 of

solder joints should look clean, smooth and shiny. If any

the IC will be just to the left of the notch or cut-out.

of the solder joints look dull, or “blobby,” then you

171

Table 15-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Fifteen: Induction Loop Receiving System 820 pF

Ceramic

821

2

Mylar

205

172

Chapter Fifteen: Induction Loop Receiving System

“transmitter” is ready, with your music or audio source

connected, we can move on to testing the induction loop

1

8

receiver.

1

8

2

7

Switch the induction receiver to the “On” position.

3

6

Vs

4

5

When you first turn on the unit you will probably hear a

+IN

LM386

Vout

lot of buzzing from the wiring in the room. Rotate the

EBC

−IN

end

receiver in a horizontal plane to find a “null” where the

hum is minimal. If you can get a reasonable null, you

should be able to hear the source material from the

BC548

“transmitter” loop or at least some hum coming from

NTE123AP

the earphone. If your “transmitter” loop is “broadcasting”

then you should hear the source music or speech on the

LM2002

headphone of your induction loop receiver. If all goes

Figure 15-6

Semiconductor pin-outs

well, both your transmitter and receiver section will be

working and you will be hearing the source material in

your remote headphones.

should remove the solder from the joint and re-solder

In the event that the induction receiver does not work

the connection point over again until it looks good. Next

when first power-up, you will have to remove the

we will inspect the PC board for any possible “short”

battery and carefully examine the circuit board for any

circuits which may be the result of “stray” component

errors. The most common cause for failure are improper

leads which may have stuck to the foil side of the PC

placement of resistors, electrolytic capacitors and diodes

board. These “stray” components leads often “stick” to

installed backwards, and semiconductors such as

the board by solder residue. Solder blobs are often a

transistors installed incorrectly. Have a knowledgeable

cause of “short” circuits, so look the board over

electronics friend provide a second pair-of-eyes to help

carefully for any solder blobs as well. Once the circuit

you examine the circuit for errors. It is very easy to

board has been inspected, we can move on to installing

miss a problem since, as the builder, you will continue

the circuit board into a case or enclosure.

to see the same circuit, the same way over and over.

We mounted the induction loop receiver in a 3′′ × 6′′

Once the error has been found and corrected, you can

by 11/2′′ metal chassis box. We placed one 1/8′′ jack at

re-connect the battery and test the circuit once

the rear of the case for coil L1, then we placed the

again.

second 1/4′′ phone jack, power on-off switch and volume

As mentioned earlier, you can use the system for

control on the front side of the chassis box. Locate a

hard of hearing people, for museum displays and

9 volt battery clip and solder the black or minus (−) lead

demonstrations, for theater personnel, late night TV

to the circuit ground. Next you will want to wire the red

listening, etc. You could wind a transmitter loop around

or positive (+) battery clip in series with the On-Off

your easy chair and use the system to “broadcast” TV

switch to the two power junction points on the PC

sound to your earphones for late night listening. This is

board, one at R2 and the other at pin 6 of the LM386

a great Boy Scout project for helping old folks

IC. Once the circuit is inside the enclosure, you can

who live in nursing homes to better enjoy TV, radio and

begin testing the induction loop system. First you will

music.

want to make sure that the “transmitter” portion of the

system is up and running. If you elected to use an

You can also use the induction loop receiver by itself

existing stereo receiver or amplifier, make sure that the

without the transmitter loop, to trace power wires

large coil is connected through a series resistor to the

behind a wall or ceiling by listening for a sharp increase

speaker terminals of the amplifier. Set the receiver or

in hum as the coil passes near the wire. Make sure that

amplifier to MONO. If you elected to build your own

current is flowing in the wires to be traced by turning

audio amplifier to drive the large loop, again connect up

on a lamp or other appliance. Other wires can be traced

the coil via an 8 ohm 10 watt series resistor. Once the

if they are carrying alternating current in the audio

173

range or a signal generator can be connected to

the wire. This ground connection can also just be a

produce the current. Connect the generator to the wire

temporary wire laying on the floor running from the

to be traced and connect the generator’s “ground”

generator ground to the far end of the wire you wish to

to the house wiring ground. Also ground the far end of

trace. Have fun using your new induction loop

the wire you are tracing so that current flows in

receiver!

Chapter Fifteen: Induction Loop Receiving System

174

Chapter 16

Lightning Storm Monitor

VR7

25k ohm

Parts list

potentiometer(trimmer)

VR8

10 megohm

Lightning Storm Monitor

potentiometer

R1

47k ohm 1/4w,

(chassis mount)

5% resistor

VR10

10 megohm

R2,R4,R7

10k ohm 1/4w,

potentiometer

5% resistor

(trimmer)

R3

5.6k ohm 1/4w,

C1,C9

2.2 pF, 50 volt

5% resistor

mica capacitor

R5

470k ohm 1/4w,

C2,C10

180 pF, 50 volt

5% resistor

mica capacitor

R6,R10,R11

22k ohm 1/4w,

C3,C4,C6,C8,C11,C12,C22,

5% resistor

C23

10µF, 50 volt

R8

390 ohm 1/4w,

electrolytic capacitor

5% resistor

C5

.01µF, 50 volt disk

R9

4000megohm or

capacitor

greater (see text)

C7,C21

100 pF, 50 volt

R12

220k ohm 1/4w,

mica capacitor

5% resistor

C13

.22µF, 50 volt disk

R13

1 megohm 1/4w,

capacitor

5% resistor

C14,C15,C16,C19,C24

R14

100k ohm 1/4w,

.1µF, 50 volt disk

5% resistor

capacitor

R15

10 ohm

C17

.47µF, 50 volt disk

VR1

500k ohm

capacitor

potentiometer

C18

220µF, 50 volt

(chassis mount)

electrolytic capacitor

VR2,VR9

1 megohm

C20

470µF, 50 volt

potentiometer

electrolytic capacitor

(trimmer)

D1,D2

1N914 silicon

VR3

3k ohm

diode

potentiometer

(trimmer)

L1

coil optional -

3000 turns on 2’ × 6”

VR4,VR5,VR6

10k ohm

PVC form

potentiometer

(chassis mount)

Q1

J176 P-Channel JFET

175

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

U1

LF355 (JFET)

U2

LM7805 - (+) voltage

regulator

U2,U3,U5

LM741N op-amp

U3

LM7905 - (−) voltage

U4

LM380 audio amplifier

regulator

S1

SPDT switch (Hi/Lo)

T1

24-VCT transformer

S2

SPST switch (load)

2-amp-center tapped

ceramic high voltage

S1

SPST toggle switch -

type

On-Off

M1

500 ua meter

F1

2-amp fast blow fuse

(RM1200 ohm)

Misc

PC board, wire,

M2

250-0-250 FS meter

connectors, etc.

(RM450 ohm)

Intense electrical storms created by unstable weather

J1

1

/8” switches jack

conditions frequently occur all around the world. At any

J2

RCA jack - signal

given point in time there is likely to be an electrical

output jack for data

storm occurring somewhere in the world. Most people

collection

would really appreciate having an advance warning of

J3

SO-239 - Antenna-2

an approaching electrical storm, especially hikers,

input jack

boaters or backyard party goers. Why not construct your

own lightning monitor to obtain an advance warning of

J4

Antenna-1 - RCA jack

an approaching storm before it arrives, thus giving you

for whip or outdoor

ample time to seek shelter from the elements. The

Ant.

lightning detector will give you ample warning of an

CT

Capacitive Hat

approaching electrical storm before you see and hear the

(see text)

lightning. The sensitive lightning detector project will

Misc

IC and transistor

alert you to an oncoming storm over 50 miles away,

sockets, wire,

giving you time to take cover or to go inside to safety.

PC board.

During a lightning strike, is the Earth considered

Multi-voltage Power

positive or negative, is a question often asked. In an

Supply

electrical storm, the storm cloud is charged like a giant

R1

5 k

potentiometer -

capacitor. The upper portion of the cloud is positive

(trimmer)

and the lower portion is negative. Like all capacitors,

Lightning Storm Monitor

an electrical field gradient exists between the upper

R2

240 ohm, 1/4watt,

positive and lower negative regions. The strength or

5% resistor

intensity of the electric field is directly related to the

C1,C4,C7

4700µF, 50 volt

amount of charge build-up in the cloud. This cloud

electrolytic capacitor

charging is created by a colliding water droplets.

C2,C5,C8

.1 µF, 50 volt

As the collisions continue and the charges at the top

ceramic disk capacitor

and bottom of the cloud increase, the electric field

C6,C6,C9

10 µF, 50 volt

becomes more intense—so intense, in fact, that the

electrolytic capacitor

electrons at the Earth’s surface are repelled deeper into

BR1

4-diode bridge

the Earth by the strong negative charge at the lower

rectifier – 3 amp,

portion of the cloud. This repulsion of electron causes

100 volt

the Earth’s surface to acquire a strong, positive charge.

U1

LM317 - (+) voltage

The strong electric field also causes the air around the

Chapter Sixteen:

adjustable regulator

cloud to break down and become ionized (a plasma).

176

Chapter Sixteen:

A point is reached (usually when the gradient exceeds

Tucson, AZ, is a network of more than 130 magnetic

tens of thousands of volts per inch) where the ionized air

direction finders that covers the entire USA—more than

begins to act like a conductor. At this point, the ground

twice the coverage of existing weather radar networks.

sends out feelers to the cloud, searching for a path of least

Each direction finder determines the location of a

resistance. Once that path is established, the cloud-to-earth

lightning discharge using triangulation and is capable of

capacitor discharges in a bright flash of lightning.

detecting cloud-to-ground lightning flashes at distances

Because there is an enormous amount of current in a

of up to 250 miles and more. Processed information is

lightning strike, there’s also an enormous amount of

transmitted to the Network Control Center where it’s

heat (in fact, a bolt of lightning is hotter than the

displayed in the form of a grid map showing lightning

surface of the sun). The air around the strike becomes

across the USA: (www.lightningstorm.com/tux/jsp/gpg/

super heated, hot enough in fact that the air immediately

lex1/mapdisplay_free.jsp).

close to the strike actually explodes. The explosion

Recently, NASA has improved the resolution of the

creates a sound wave that we call thunder. A typical

system by adding acoustical measurements to the mix.

high energy lightning strike is shown in Figure 16-1.

Lightning Storm Monitor

Although the flash and resulting thunder occur at

Cloud-to-ground strikes are not the only form of

essentially the same time, light travels at 186,000 miles

lightning though. There are also ground-to-cloud

per second, whereas sound travels at the relative snail

(usually originating from a tail structure) and cloud-

pace of one-fifth of a mile in the same time. Thus,

to-cloud strikes. These strikes are further defined into

the flash—if not obscured by clouds—is seen before the

normal lightning, sheet lightning, heat lightning, ball

thunder is heard. By counting the seconds between the

lightning, red sprite, blue jet, and others that are lesser

flash and the thunder and dividing by 5, an estimate of

defined. For more information on lightning, see:

the distance to the strike (in miles) can be made.

http://science.howstuffworks.com/lightning.htm.

In the NASA lightning sensor, a low frequency

Satellites are more often used to follow lightning

receiver detects the lightning strike. The leading edge

strikes around the world but haven’t advanced to the

of the electric-field pulse is used to start a timer and

point where they can accurately map local areas. There

the leading edge of the thunder pulse is used to stop the

are two major types of sensors commonly used—

timer. A microcontroller in each receiver transmits the

magnetic direction finders and VHF Interferometery.

time measured to a processing station, where the times

The National Lightning Detection (NLDN), which is

are converted to distances that are used to compute the

operated by Global Atmospherics, Inc., (GAI) in

location of the lightning strike to within l2 inches.

However, the NASA sensors have to be located within a

30 mile radius of the strike to be accurate.

If you are interested in monitoring static levels

around you in stormy weather, and the ability to have

some advance warning of an impending storm, then this

circuit will be of great interest to you especially if you

are involved in the radio hobby and have antennas high

in the air. The Lightning Storm Monitor has proven to

be very reliable and useful for advanced storm warning

activities.

The Lightning Monitor circuit is shown in the

schematic in Figure 16-2. The Lightning Monitor is

actually two receivers in one, a spheric monitor and a

static electricity monitor. The static monitor portion of

the circuit begins at the outdoor Antenna-2, a capacitive

hat type antenna which is fed with coax from the

Figure 16-1

Lightning

antenna to the receiver. The gate of the P JFET is tied

177

Chapter Sixteen: L i g h t n i n g S t o r m M o n i t o r 178

C7

C10

Antenna

VR1

R2

R5

VR2

+5 V

+

+5 V

L1

C1

C3

7

+5 V

+

S1

H:

2

Spheric

–

C5

R3

7

C6

+

C11

meter

C2

U1

C9

–

R6

7

VR3

6

2

2

+

U2

–

D1

M1

R8

3

4

Low

+

6

U3

–

+

3

4

R1

+

3

C4

C13

D2

R4

+

–5 V

+

C8

–5 V

R7

–5 V

C12

+

VR4

C20

J1

+

C14

C19

+12 V

C15

VR5

R15

+ 14

12

11 10

8

C18

6

VR6

C16

U4

Speaker

1 2 3 4 5 7

+

C17

VR7

M2

J2

C24

–

+

Static

C21

meter

Antenna

Capacitive

VR8

2

hat

+5 V

+5 V

R22

+

Q1

C22

S

2

7

G

–

6

U5

D

3

S2

5

+

1

R9

+5 V

4

R11

R13

R12

C23

VR10

VR9

+

–6 V

R14

–5 V

Figure 16-2

Lightning monitor. Courtesy of Russell Clit

Chapter Sixteen:

to ground since a dual polarity supply is used, through

In the Spheric, or RF section of the Lightning

a very high resistance. In the original prototype, I

Monitor, the whip antenna at Antenna-1 was fed to a

experimented with an 11,000 megohm resistor. These

coil consisting of a 4′ foot long 6′′ inch diameter PVC

high value resistors are hard to find; you may notice

pipe, the coil consists of about 3000 turns of insulated

that it is a moot point if there is too much leakage in

wire on it. You will find that just a straight whip antenna

your circuit. In that light, it is best to standoff the gate

works fine, so it was found that the large coil is not

and use a high quality new coax to your outside

mandatory. The original thought for using the coil at the

antenna, usually a capacitive hat type. You must also

antenna was to have a lot of signal at low frequencies

come up with a mount design which keeps rain from the

with a high Q inductor, to give more signal while trying

point on the mount where current could flow to ground,

to reduce the overall gain of the circuit, to minimize

or you will notice that your meter becomes very

60 cycle hum. On that note, long whips or especially

insensitive as it starts raining.

long wires are not very desirable here, so stay with a

5′ to 6′ vertical whip antenna.

The prototype used a 22′′ shaft from an amateur radio

antenna in a mobile antenna mount, with two nuts on top

The input signal is amplified with a JFET input

Lightning Storm Monitor

to hold the capacitive hat and a plastic umbrella to protect

op-amp at U1, with selectable input range through a small

the mount from moisture. Likewise the coax connection

value capacitor to allow high gain to be achieved with

must be well sealed from moisture, an SO-239 type

minimum 60 cycle hum. A LM741 op-amp gives gain to

connectors at the antenna and on the chassis for the meter

provide audio signal and then another LM741 is used

inside the house. As far as the resistance load goes, if you

to drive a 500 µA single ended meter for a reading of

cannot locate a high value for R9, you can fabricate a high

RF levels. You may find it easier to make the series

value type if need be, for the strong field load. A 10 meg

resistance control for the meter to be a front mounted

potentiometer which could be switched out of circuit was

control as well as the gain control for the meter driver,

used in the prototype. For the switch at S2, you could use

i.e. the 741 op-amp, as it give much more flexibility

a ceramic high voltage type to minimize leakage. The

under differing weather conditions. This meter is very

FET type is not critical; in the prototype a J176 came

helpful in determining the number of lightning strokes

from All Electronics, also the meter and the 10 meg

per unit time in severe weather.

potentiometer came from them as well.

The audio output from the Spheric monitor section

Through experimentation it was found that controlling

is derived form an LM380 IC circuit; you will notice

the offset of an op-amp gave a very sensitive way to

interaction between controls if you build it as shown.

control meter balance, far superior to trying to shift the

A buffer and mixer circuit might be helpful here, but in

meter itself. If you cannot locate a zero center meter you

the original design we decided to keep the parts count

might ground the end, or put it on a trimmer tap where the

low. Also, an equalizer circuit for the signal out is a very

ends of the pot are on the plus and minus of the supply, say

good addition, so you can tailor the output response

a 5 or 10 K pot. If you can find it, a 250-0-250 µA meter is

and reduce unwanted signals such as line power noise.

suggested. In the maximum gain mode you can notice field

A signal output is provided so the output can be fed to a

gradient changes in clear weather from morning to night,

digital multi-meter with PC interface, if desired to log

as well as detect storms more than a state away. One

readings of the Lightning Monitor over time.

problem you will notice with this circuit, especially at high

gain settings, is that you have to re-zero the meter often as

the polarity changes overhead in stormy weather.

Building the lightning

The higher the gain of the op-amp or the higher the

input impedance of the FET gate, the more this becomes a

monitor

problem, which is why a provision was made to lower the

impedance of the gate circuit and reduce the op-amp gain

Prior to constructing the Lightning Monitor, you will

in strong fields. Note the provision for audio to be taken

want to locate a well lit and well ventilated work area.

from the op-amp, and mixed with separate levels for the

A large clean work bench or work table would be

static and RF signals, as well as a master volume.

suitable for building the project. Grab a 27 to 33 watt

179

pencil tipped soldering iron, a roll of 22 gauge

represents a multiplier value of 1000, so 47 times

60/40 tin/lead rosin core solder. You should also have

1000 is 47,000 ohms or 47k ohms. The fourth color band

a small jar of “Tip Tinner,” a soldering iron tip dresser

on resistors represents the resistor’s tolerance. A silver

which is available from your local Radio Shack store.

band denotes a 10% tolerance, a gold band represents a

You’ll probably want to gather a few tools, such as a

5% tolerance resistor and no color band denotes a

pair of end-cutters, a small pair of needle-nose pliers,

20% tolerance resistor. Once you have found R1, you

a pair of tweezers, a magnifying glass, a small Phillips

can try and locate resistor R2 and so on. You can place

screwdriver as well as a small flat-blade screwdriver.

the resistors on the circuit board in groups of four or so

Place your schematic diagram along with your circuit

in their respective locations on the circuit board. Once

layout diagram and various charts and tables in front of

you have the first four resistors placed on the PC board,

you on your work table. Place your project components

you can go ahead and solder them in place on the board.

and circuit board in front of you and we can begin

After the resistors have been soldered onto the circuit

constructing the Lightning Monitor. A printed circuit is

board, you can cut the excess component leads flush

highly recommended for building this project rather

to the edge of the circuit board using your end-cutters.

than trying to use perf-board construction to permit

Now, you can locate the next batch of four resistors

more reliable operation from your circuit. Warm up

and place them in their respective locations on the

your soldering iron and we will begin construction!

circuit board, then go ahead and solder them in place.

Let’s begin building the monitor by first identifying

Remember to trim the excess component leads. Finish

the project resistors. Locate the resistors from the parts

up installing the resistors and then we will move on to

pile. Refer to the chart in Table 16-1, which illustrates

installing the two silicon diodes.

the resistor color codes and their values. Resistor R1,

There are two silicon diodes in this project, and

for example, is a 47k ohm 1⁄4 watt 5% resistor. Try and

they are located in the meter range and display circuit.

locate it from the parts pile. The first color band at one

Diodes have two leads, a cathode lead and an anode

edge of the resistor body should be yellow, which

lead. Take a look at the resistors and you will notice that

is the number (4). The second color band should be

there will be either a black or white color band at one

violet or number (7) on the chart. The third color band

edge of the diode’s body. The color band denotes the

is the multiplier and should be orange in color and

cathode lead of the diode. It is important that you install

Table 16-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Lightning Storm Monitor

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000(M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Sixteen:

No color

20%

180

Chapter Sixteen:

the diode correctly with respect to this polarity. One you

solder them in place, follow up by removing the excess

have installed the two diodes in their proper place, you

lead lengths. Install the remaining electrolytic capacitors

can solder them in place on the circuit board. Don’t

and solder them in place. Use your end-cutters to remove

forget to cut the extra component lead lengths.

the extra lead lengths by cutting them flush to the edge

Next, we will try and locate the capacitors for the

of the circuit board.

Lightning Monitor project. This project uses two types

The Lightning Monitor uses a single FET transistor

of capacitors, small ceramic disk types and the larger

at Q1, which is connected to antenna-2. The P channel

electrolytic types which have polarity. The small

J-FET at Q1 is a J176 FET, which must be handled with

capacitors come in many different styles and shapes and

care using an anti-static wrist band to avoid damage.

sometimes they are so small that there is not enough

This component is very sensitive to static electricity and

room to print their actual value on the component, so

can be easily damaged in handling. The three leads of

a three-digit code is used. Refer to the chart shown in

the transistor Q1 are all in a single row with the Drain

Table 16-2 when installing the small capacitors. For

lead at one end and the Gate lead in the center and the

example, a .1 µF capacitor would have a code value

Source lead at the opposite end of the plastic case of

Lightning Storm Monitor

of (104). The Lightning Monitor also utilizes larger

the transistor. Refer to Figure 16-3, which illustrates the

value electrolytic capacitors, these capacitors are

semiconductor pin-outs.

usually large and have polarity marking on them, such

Before we install the integrated circuits in this project,

as a black or white color band or a plus (+) or minus (−)

we would highly recommend using IC sockets. Integrated

marking on them. These polarity markings must be

circuit sockets are good insurance in the event of a

observed when installing the capacitors on the circuit

possible circuit failure at some possible distant point in

board. Failure to observe the correct polarity could

time. It is much easier to simply unplug a defective IC,

result in either a damaged component or a damaged

rather than trying to un-solder a 14-pin IC from the

circuit when first power-up.

circuit board. Integrated circuit sockets are inexpensive

and easy to locate. There a number of integrated circuits

Look through your component parts pile and let’s try

in this project, from 8-pin to 14-pin dual in-line types.

and identify some capacitors. Let’s begin with some of

In order to install the integrated circuits correctly, you

the small types such as C1 and C2. Capacitor C1 may be

must observe the correct orientation. Failure to install

marked 2.2 or 2n2, while Capacitor C2 will most likely

the integrated circuits correctly can cause serious

be labeled 181. Try and locate the lower value capacitor

damage to the IC and to the circuit itself, so you must

from the parts stock and place about four components at

get it right the first time! Each plastic IC package will

a time on the PC board in their respective locations. After

have either a cut-out, a notch or small indented circle at

placing four or so of the first lot of capacitors, you can

one end of the plastic package. Looking just to the left

go ahead and solder them in place. Remember to trim

of the notch or cut-out you will find pin 1 of the IC.

the excess component leads from the board. Take the

You must align pin 1 of the IC to pin 1 of the IC socket

next grouping of four capacitors and install them on the

when installing the chip on the PC board. Take a look at

PC board while referring to the schematic and parts

U1, this is an 8-pin dual in-line IC. Since we will not be

layout diagrams. Go ahead and solder the next group of

using pin 1 on this IC, you will have to make sure that

four capacitors and trim the excess lead lengths. Install

pin 2 or the minus (−) input is connected or aligns with

the remaining smaller capacitors and then we will move

C1 and R2, while pin 3 of U1 is connected to resistor

on to installing the larger value electrolytic capacitors.

R1 and so on. Now, go ahead and insert the integrated

As mentioned, electrolytic capacitors will have polarity

circuit into their respective sockets.

markings on them and they must be installed correctly in

order for the circuit to work properly. Take your time

There are a number of potentiometers in this project,

when identifying the electrolytic capacitors. Observe

some of which are chassis mounted controls, while

their polarity marking and then make sure you orient

other potentiometers will be circuit board mounted

them correctly and in their proper location on the PC

types. Refer to the parts list below and Table 16-3. You

board. Refer to the schematic and parts layout diagram.

can locate the circuit board trimmer type potentiometer

Install a few electrolytic capacitors at one time, and them

and install them at their respective locations on the

181

Table 16-2

Capacitor code information

This table is designed to provide the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules.

Most capacitors actually have the numeric values stamped on them; however, some are color coded and some have alphanumeric codes. The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

Lightning Storm Monitor 82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Sixteen: 820 pF

Ceramic

821

2

Mylar

205

182

Chapter Sixteen:

1

8

1

8

1

8

1

8

2

7

2

7

3

6

3

6

4

5

4

5

LM741N

LM741N

TO-92

1

8

SG

1

8

D

2

7

3

6

J176 jFET

4

5

1

8

1

8

LM380

2

7

3

6

1

8

4

5

1

8

2

7

LM741N

3

6

4

5

Lightning Storm Monitor

LF355

Figure 16-3

Semiconductor pin-outs

circuit board. Solder them in place and then trim the

we can move on to inspecting the PC board for possible

excess leads if necessary.

“short” circuits. There are two main causes for “short”

circuits, small round solder blobs laying across a PC

Let’s take a well deserved break and when we return

“trace” can cause a circuit to “short-out.” The second

we will inspect the circuit board for possible “short”

cause of “short” circuits is a “stray” component lead.

circuits and “cold” solder joints. Pick up the Lightning

Often when cutting excess component leads,

Monitor circuit board with the foil side of the board

they will “stick” to the circuit board from rosin core

facing upwards towards you. First we will inspect the

solder residue. Make sure that there are no “stray” leads

PC board for possible “cold” solder joints. Take a look

bridging between the circuit board traces. Once you

at the solder joints, they should all look clean, shiny and

are confident that there are no “shorts,” we can move

bright. If you see any solder joints that appear dull, dark

on to finishing the project.

or “blobby,” then you should remove the solder from

the joint and re-solder the joint all over again until it

Now, let’s move on to mounting the larger components

looks good. Once you are confident that all looks well,

and hardware on the chassis box. The chassis mounted

Table 16-3

Potentiometer functions

Potentiometer

Function

Type

VR1

Spheric Gain Control

500k chassis mount

VR2

Meter Gain Control

1 megohm trimmer

VR3

Meter Range Control

3k trimmer

VR4

Spheric Volume Control

10k chassis mount

VR5

Static Volume Control

10k chassis mount

VR6

Main Volume Control

10k chassis mount

VR7

Static Range Control

25k trimmer

VR8

Static Gain Control

10M chassis mount

VR9

Static Meter Balance Control

1 megohm trimmer

VR10

Load Control

10 megohm trimmer

183

potentiometers were all mounted on the front of the

If you wish to experiment, you can try an indoor 5′

metal chassis used to house the project, and wired to the

whip without the coil and see how the circuit performs.

circuit board with 20 ga. insulated wire. The two toggle

You could also experiment with an outdoor whip

switches, S1 and S2, were also mounted on the front

antenna without the coil and you could build the coil

panel of the chassis and were wired to the circuit board

and place it in series with an outdoor whip antenna if

using 22 ga. insulated wire.

desired.

The Lightning Monitor utilizes two analog meters,

The Lightning Monitor needs a power supply which

one for each monitoring circuit. The meter for the

can provide a 12 volt source for the audio amplifier

Spheric circuit at M1, was a 500 µA meter, while the

circuit as well as a plus and minus power supply for

Static meter circuit uses a 250-0-250 µA center reading

the op-amps. The diagram in Figure 16-5 illustrates a

meter at M2. Both of these meters were found surplus

12 volt and dual plus/minus 5 volt power supply which

and were mounted on the front panel of the metal

can be used to power the Lightning Monitor. The

chassis.

prototype Lightning Monitor incorporated the power

The speaker was mounted on the rear panel of the

supply in the same chassis as the actual monitor. You

chassis and wired to the circuit board using two 6′′

will need to locate a 12 volt, 250 mA center-tapped

lengths or #22 ga. insulated wire. A 1⁄

transformer ahead of the rectifier circuit. The rectifier

8′′ switched mini

audio panel jack for headphone use was mounted on the

circuit is fed directly to the regulator integrated circuits

front panel. An RCA jack was provided for antenna-1;

as shown. You will need to connect the dual voltage

you can use a whip antenna or an outdoor whip antenna.

power supply to the Lightning Monitor. The plus voltage

An SO-239 antenna connector was mounted at the rear

is connected to pins 7 on both the LM741 and the

panel to allow the Capacitive Hat antenna-2 to connect

LF355 op-amp as well as to the J-FET at Q1. The

to the circuit board, via a small piece of coax cable.

negative voltage supply is connected to pin 4 of both

The Capacitive Hat antenna is shown in Figure 16-4,

the LM741 and the LF355 op-amp, as well as to the

it can be built with an antenna bracket mounted on a

JFET at Q1. The 12 volt power supply is used to power

pole outdoors. An SO-239 jack was mounted on the

the LM380 audio amplifier.

small antenna bracket. A threaded shaft was silver

Once the power supply and Lightning Monitor have

soldered to the center terminal of the connector with a

been completed, you connect the whip antenna-1 and

small rain guard on it. At the top of the threaded shaft

the Capacitive Hat antenna-2 and prepare for testing the

a metal coffee can lid is held in place with two nuts.

Lightning Monitor. To best test the circuit you will need

The antenna can be placed outdoor on a pole near the

to wait for a thunderstorm. However, you can do some

house with a length of coax cable leading from the

testing of the circuit. First, apply power to the Lightning

antenna to the antenna jack on the Lightning

Monitor circuit, turn the Off-On switch to the “On”

Monitor.

position. Make sure both antennas are connected. Turn

Lightning Storm Monitor

up the main volume and the Static Volume controls past

the 1⁄2 position and adjust VR7 to past 1⁄2. You will need

to generate some static electricity by rubbing a lucite

Metal coffee

rod with some animal fur to create a static charge. Bring

Nuts

can lid

the lucite rod near the Capacitive Hat antenna and you

should see the Static Meter at M2 swing into action.

Threaded shaft

This will give you a good indication that the Static

Antenna

Rainguard

portion of the meter is working. You may be able to test

mount

(plastic umbrella)

the Spheric Meter portion of the circuit if you have an

RF broadband noise generator.

If the Lightning Monitor doesn’t seem to work at all

or appears DEAD, then you will want to turn “Off ” the

SO239

circuit and remove the power and inspect the circuit

Chapter Sixteen: Figure 16-4 Antenna-2 – Capacitive hat antenna board once again. While inspecting the circuit board

184

Chapter Sixteen:

R1

C1

C2

C3

+

+

+

R2

2

1

3

U1

+12 V DC

PL1

S1

C6

+

F1

24 V CT

1

3

+5 V DC output

Lightning Storm Monitor

T1

U2

BR1

+

+

AC +

C4

2

C5

Common

117 V AC

AC –

ground

1

3

U3

– 5 V DC output

2

C7

C8

C9

+

+

+

Figure 16-5

Multi-voltage power supply

you will be looking to make sure that the electrolytic

supplies are connected to the correct points and that the

capacitors have been installed correctly, to be sure that

op-amps have been installed correctly. Once you are

the diodes and the JFET have been installed correctly as

confident of your inspection and hopefully you found

well. Have a knowledgeable electronic hobbyist inspect

your error, you can re-apply power and re-test the circuit

the circuit, since it is easy to overlook something and

again. Good luck and be safe when experimenting with

not catch it the second time. Make sure that your power

outdoor antennas, keeping them away from power lines.

185

Chapter 17

Ambient Power Receiver

In 1979, Joe Tate began experimenting with methods

Parts list

of turning radio energy in the air into usable electric

power. He first developed a clock which drew its power

Original Ambient Power

from an antenna that was just a long piece of wire

Module I

stretched out horizontally about 20 feet above the

ground. The power supply for the clock worked

C2,C3

.047 µF, 50 volt

something like an old-style crystal radio, except that

capacitor

it did not have a tuning circuit. Because of this, the

C1,C4

40 µF, 50 volt

“Crystal Clock” was able to absorb a wide spectrum of

electrolytic capacitor

radio noise from the antenna and yield electric power.

D1,D2

1N34 diodes

The power supply was able to deliver much more

current than was developed in a crystal radio, although

D3,D4

1N34 diodes

its output was just still just a few millivolts.

ANT

50+ foot broadband

Joe began recording the power supply’s output over

monopole antenna

a long period of time to determine its dependability.

GND

Earth ground stake

After all, the device relied completely on whatever

Misc

PC board, wire,

stray signals happened to be in the air. Using an Atari

hardware, enclosure

computer, the output of the clock’s power supply was

Ambient Power Module II

measured continuously and recorded on floppy disk.

This was done by feeding the unregulated voltage

D1,D2,D3,D4,D5,D6

1N60

output directly into the computer’s joystick port.

germanium diodes

Joe began calling this power supply the “Ambient

D7,D8,D9,D10,D11,D12

Power Module” (APM) because it extracted power from

1N60 germanium diodes

ambient background radio noise. This small circuit,

C1,C2,C3,C4,C5,C6

when connected to antenna and ground, used the

470 µF, 50 volt

potential difference between air and ground to generate

electrolytic

a small direct current continuously. Joe’s original claims

capacitors

stated that the APM could produce up to 36 volt/9 watts.

C7,C8,C9,C10,C11,C12

Joe applied for a US Patent and was later granted patent

470 µF, 50 volt

#4,628,299. As he studied the recorded data, mild

electrolytic capacitors

fluctuations were noted in a daily cycle. The patterns

were consistent over long periods of time, though they

L1

480 turns #22 wire

differed in different locations. Aside from that, the

on 3” plastic tube

APM looked like a very dependable source of power.

ANT

50+ foot broadband

In the spring of 1984, he discovered an interesting

monopole antenna

correlation between voltage fluctuations from the APM

GND

earth ground stake

and a local earthquake event; this point will be

Misc

printed circuit

discussed later.

board, wire, hardware,

The APM operates, as a broadband receiver of energy

case

in the lower portion of the radio spectrum, receiving

186

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Seventeen: Ambient Power Receiver

to the signal path and rectifier D1 is connected in series,

in the well-known voltage multiplier arrangement.

Capacitor C1 is connected in parallel across the output of

Ambient power

module

the APM to smooth the rectified output. The right or

positive side of the circuit is similar, except for the

polarity of the diodes.

In operation, an RF voltage is developed across the

antenna; this voltage is voltage multiplied by the two

rectifiers on each side of the circuit. The resultant

voltage output is smoothed or filtered by capacitors

Figure 17-1

Ambient power module

C2 and C4. The circuit is very symmetrical with the

plus side mirroring the minus side of the circuit. The

output of the APM is ideal for low voltage, high

most of its power from below 1 MHz. The basic circuit

impedance devices, like digital clocks, calculators,

may be combined with a variety of voltage regulation

radios and smoke alarms, which are the most likely

schemes.

applications for this power source.

The original Ambient Power Module is shown

One possible application for the APM is to

in Figure 17-1 and the schematic diagram circuit in

charge small NiCad batteries which provide effective

Figure 17-2 is used to convert the ambient RF energy

voltage regulation as well as convenient electrical

to a direct voltage which can be used and handled by

storage. Charging lead acid batteries is not practical

data processing equipment. This design makes use of

because their internal leakage is too high for the

doubler, splitter and rectifier circuit configurations.

APM to keep up with. Similarly, this system will not

Designated as an ambient power module (APM), the

provide enough power for incandescent lights

circuit is connected to an antenna, preferably a 50 foot

except in areas of very high radio noise. The APM

or greater broadband monopole antenna. The antenna is

could also be used to power small electronic devices

connected to the APM circuit via two capacitors C2 and

with CMOS circuitry, like clocks and calculators.

C3, each being in series with the antenna input line for

Smoke alarms and low voltage LEDs, and small

coupling and each having a value of 0.047 microfarad.

emergency power/lighting circuits can also be powered

Taking the left or negative side of the circuit first,

by the APM. Use your imagination to devise an

it comprises two rectifiers (diodes) D3 and D4

application for the APM.

(1N34 type) and a filter capacitor C4

(40 microfarads). Rectifier D2 is connected in parallel

Building the APM circuit

The builder has a choice of wiring techniques which

Antenna

may be used to construct the module. It may be hand

wired onto a terminal strip, laid out on a bread board,

experiment board, or printed circuit. We chose to build

C2

C3

the original circuit on a small printed circuit board.

–V

D1

D3

+V

Locate a clean well lit work table to build the APM.

Find a small 27 to 33 watt pencil-tipped soldering iron,

as well as some “Tip Tinner.” “Tip Tinner” is a

D2

D4

soldering iron tip cleaner/dressing compound which

C1

C4

helps to clean the soldering tip after use and can be

obtained at your local Radio Shack store. Try and

locate a pair of end-cutters, a pair of small needle-nose

Figure 17-2

Ambient power module 1

pliers and a set of screwdrivers. Grab your schematic

187

diagram and look closely at it, before we begin

construction.

Antenna requirements

The APM power receiver consists mainly of diodes

and capacitors and you will recall that both of these type

The antenna needs to be of sufficient size to supply the

of components have polarity which must be observed for

APM with enough RF current to cause conduction in

the circuit to function correctly. The diodes used in the

the germanium diodes and charge the ground coupling

APM circuit are germanium diodes and NOT silicon

capacitors. It has been found that a long horizontal

diodes which have a voltage drop. Diodes will have

antenna wire works best. A fifty foot monopole, or

either a white or black band at one side of the diode’s

long-wire antenna will work well, but a small antenna

body. This colored band denotes the cathode end of the

should work, and of course you can experiment with

diode. When installing the diodes on the PC board

your own antenna ideas. The antenna will work best

make sure you observe the correct placement of all the

when elevated to 20–30 feet. Lower elevations will

diodes.

work, but a longer wire may be necessary for best

The APM circuit utilizes various capacitors, both

results.

electrolytic and non-electrolytic types. Electrolytic

In most locations, possible supporting structures

capacitors are often larger size capacitors with larger

already exist. The wire may be stretched between the top

values. Electrolytic capacitors have polarity and

of a building and some nearby tree or telephone pole,

may have either a black or white color bands with plus

see Figure 17-3. If live wires are present on the building

or minus marking at one end of the capacitor body.

or pole, care should be taken to keep your antenna and

When installing the electrolytic capacitors make

body well clear of these hazards. To mount the wire,

sure that you orient the capacitors correctly with

standard commercial insulators may be used as well as

respect to the circuit diagram. The chart in Table 17-1

homemade devices. Plastic pipe makes an excellent

may help you to identify the small value capacitors.

antenna insulator. Synthetic rope also works very well,

In many instances, small value/size capacitors

and has the advantage of being secured simply by tying

often use a three-digit code to represent a capacitor

a knot. It is convenient to mount a pulley at some

value.

elevated point so the antenna wire may be pulled up to it

Once all the components have been placed on the

using the rope which doubles as an insulator.

PC board, you can take a short break and when we

return we will inspect the circuit board for possible

“short” circuits and “cold” solder joints. Pick up the

Grounding the APM

circuit board with the foil side facing upwards toward

you. Look over the board carefully and inspect the solder

The APM requires a good ground circuit in order to

connections. The solder joints should all look clean,

operate efficiently. Usually a good ground can be

smooth and shiny. If any of the solder joints look dull,

established by connecting a wire to the water or gas

dirty or “blobby” then remove the solder from the joint

pipes of a building. Solder or screw the wire to the

and re-solder the connection over again so that it

APM ground terminal. In buildings with plastic pipes

looks good.

or joints, some other hookup must be used. A metal

Next we will inspect the circuit board for any “short”

rod or pipe may be driven into the ground in a shady

circuit which could result from solder blobs or remaining

location where the earth usually is damper. Special

component leads left from the building process.

copper coated steel rods are made for grounds, which

A component lead resting across a PC trace can result

have the advantage of good bonding to copper wire.

in a “short” circuit which could cause the circuit

A ground of this type is usually found within the electrical

to fail.

system of most buildings. Conduit is a convenient

Once you are satisfied that your circuit looks good,

ground provided that the conduit is properly grounded.

you can move on to testing the APM receiver. First you

This may be checked with an ohmmeter by testing

will need to attach a good antenna ground connection to

continuity between the conduit and system ground

Chapter Seventeen: Ambient Power Receiver the APM receiver module.

(ground rod). Just as with the antenna, keep the ground

188

Chapter Seventeen: Ambient Power Receiver

Table 17-1

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Most capacitors actually have the numeric values stamped on them; however, some are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

820 pF

Ceramic

821

2

Mylar

205

189

Over time experimenters have improved upon the

original APM design and claim increased output from

the original design, so the reader is free to experiment

and build both versions of the APM if desired. The

second APM receiver, shown in Figure 17-4, illustrates

the newer version of the APM with increased output

voltage and current. The APM-II has quite a few more

stages and has many more diodes and capacitors. You

will note that the APM-II also uses germanium diodes

Figure 17-3

Horizontal long-wire antenna

which have more output than trying to use silicon diodes.

Also note the higher capacitance values in the second

design which were used to increase the output

considerably. When constructing the APM-II be sure

wire away form the hot wires. The APM’s ground wire

to pay careful attention to mounting the diode and

may pass through conduit with other wires but should

capacitors; since there are many more components and

only be installed by qualified personnel. Grounding in

they all have polarity marking on them, it is much more

extremely dry ground can be enhanced by burying some

possible to make a mistake in orientation. Take your

salt around the rod. The salt will increase the conductivity

time when constructing the circuit. The APM-II also

of the soil and also help retain water content around the

uses an input coil, which is said to improve the output.

ground rod. Some researchers have found that it is much

Some experimenters claim that the antenna can be

better to get the largest surface area of metal in contact

eliminated and that the antenna connection can be

with the ground as possible, and have tried digging a hole

connected to another separate ground, but this has not

and planting aluminum foil sheets in the ground.

been verified. The APM-II is also sensitive to light

Once you have tested the operation of the APM, you

which can increase the output if used outside. Some

can disconnect the antenna and decide how you wish to

users claim that the power produced by the APM also

enclose the APM circuit. You may want to experiment

seems to improve near bridges, ships and anything

with the housing, since researchers have discovered that

containing a great deal of metal.

the germanium diodes are sensitive to sunlight and the

voltage output is increased when the circuit is in

Over time many scientists and researchers have

sunlight. If you want to experiment along these lines,

reported bright flashes in the sky during strong

then you may wish to enclose the circuit in a clear

earthquakes, as well as computer breakdowns during

plastic box. You can drill holes for two terminals posts

severe tremors. Scientists have long suspected that

for the plus and minus output connections, an RCA jack

seismic activity is associated with a variety of electrical

for the antenna input connection, a terminal for the

effects. Researchers have been taking a careful look

ground connection, and your APM is complete and

at this link, with an eye toward using it to predict

ready for operation.

earthquakes.

Joseph Tate and William Daily of Lawrence

Livermore National Laboratory in Livermore, CA.

The APM-II

created a system of radio wave monitors distributed

along California’s San Andreas fault using the

The original APM is a great circuit for experimentation.

APM design. Tate and Daily recorded two kinds of

It has been found that the germanium diodes are also

changes in atmospheric radio waves prior to

sensitive to light, so if you house the APM in a clear

earthquakes that occurred between 1983 and 1986. Joe

plastic box and have it exposed to sunlight it will

was able to witness and record the output of the APM

produce more output. Have fun experimenting with the

during the earthquakes that followed, since he

APM receiver and you may find the perfect application

continuously monitored the output of the APM on a

for it, such as powering another receiver or night light,

computer, so he could go back and look at the output on

Chapter Seventeen: Ambient Power Receiver clock, emergency radio/lighting, etc.

any given day.

190

Chapter Seventeen: Ambient Power Receiver

Antenna

L1

+V

D1

C6

C7

D12

–V

C1

D2

D11

C12

D3

C5

C8

D10

C2

D4

D9

C11

D5

C4

C9

D8

C3

D6

D7

C10

Load

+V

–V

A

+

–

B

30 V

Figure 17-4

Ambient power module II

The most common change is a drop in the radio signals

The researchers have also found, in addition to these

that normally pervade the air as a result of lightning and

drops, another pre-quake phenomenon in which short

human sources such as car ignition systems and electric

pulses of increased radio wave activity are emitted. For

power grids. This reduction typically occurs one to

example, five days before the magnitude 6.5 earthquake

six days before an earthquake and can last for many

hit palm Springs, CA, in July 1986, a station 15 miles

hours. For example, a magnitude 6.2 earthquake that

from the epicenter detected a rise in radio signals. This

shook Hollister, CA, in April 1984 was preceded

sort of emission is consistent with laboratory work

six days earlier by a 24-hour drop in radio signals

showing that cracking rocks release electromagnetic

being monitored 30 miles from the quake’s epicenter.

signals.

Tate and Daily have found that the larger the earthquake,

Tate says that in their first attempts at predicting

the longer the time between the radio wave depression

earthquakes, they did not miss a single event, so he

and the quake.

is optimistic about using this technique for short-term

Laboratory studies have shown that the electrical

forecasting of San Andreas quakes.

conductivity of rocks increases as they are stressed.

If you live in an earthquake prone area such as

Based on this and their electrical modeling of the

California, you could use you APM not only for small

ground, Tate and Daily think the increased conductivity

low voltage emergency power/lighting system but you

of stressed rocks near the fault causes more radio waves

could connect the APM to an analog to digital converter

to be absorbed by the ground rather than their traveling

card in a personal computer and record the fluctuations

through the air. They also plan to test a possible link

during earthquakes. The APM will provide many

between radio wave drops and the emission of radon

avenues for the builder and/or researcher. Disconnect

gas, which itself is thought to be a quake precursor. The

your APM during thunderstorm activity to avoid

radon may ionize the air, making it temporarily more

damage to the APM and other household devices. Have

absorptive than the detector antenna.

fun and be safe.

191

Chapter 18

Earth Field Magnetometer Project

Parts list

S1

4-position rotary

gain switch

Earth Field Magnetometer

S2

normally open

R1,R3,R4,R5

4.7 k ohm,

pushbutton switch

1

/ w, 5% resistor

S3

SPST toggle power

4

switch

R2

100 ohms, 1/ w,

4

5% resistor

Logger

HOBO H08-002-02

(ONSET)

R6

10k ohm 1/ w,

4

Misc

PC board, wire,

5% resistor

IC sockets, chassis,

C1,C2

15 pF, 35

volt

etc.

capacitor

Optional Field

C3,C4

47 nF, 35 volt

Magnetometer Power

electrolytic

Supply

capacitor

C1

470 µF, 50 volt

C5

10 µF, 35 volt

electrolytic capacitor

capacitor

C2

1 µf, 50 volt

C6,C8

1 µF, 35 volt

ceramic capacitor

capacitor

C3

15 µf, 50 volt

C7

22 µF, 35 volt

electrolytic capacitor

electrolytic capacitor

BR1

diode bridge

C9

10 µF, 35 volt

rectifier 100v/2-amp

Tantalum capacitor

T1

24 volt center

D1,D2

1N914 silicon

tapped transformer -.5 A

diode

U1

LM7809 IC regulator

D3

1N4001 silicon diode

9 volts

X1

10 MHz crystal

S1

SPST power switch

U1

SCL006A -

PL1

115 VAC power plug

magnetometer output IC

MISC

PC board, wire,

U2

AD-557 - digital

hardware, etc.

to analog converter

1. Speake & Co. Ltd.

chip

(Elvicta Estate,

U3,U4

LM7805, 5 volt

Crickhowell, Powys.

regulator

Wales, UK; http://

J1,J2

wire jumpers

www.speakesensors.com).

192

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Eighteen: Earth Field Magnetometer Project

2. Fat Quarters Software

with two coils. One coil is used as the excitation coil,

(24774 Shoshonee

while the other is used as the output or sensing coil.

Drive, Murieta, CA

The excitation coil is driven with a square-wave signal

92562; Tel: 909-698-

with an amplitude high enough to saturate the core. The

7950; Fax: 909-698-

current in the output coil will increase in a linear

7913; Web: http://

manner so long as the core is not saturated. But when

www.fatquarterssoftware

the saturation point is reached, the inductance of the

.com)

coil drops and the current rises to a level limited only

3. ONSET Computers, PO

by the coil’s other circuit resistances.

Box 3450 Pocasset, MA

If the simple flux-gate sensor was in a magnetically

02559-3450 (1-800-564-

pure environment, then the field produced by the

4377) http://www.

excitation coil would be the end of the story. But there

onsetcomp.com

are magnetic fields all around us, and these either add

to or subtract from the magnetic field in the core of the

Magnetic fields are all around us. The Earth itself

flux-gate sensor. Magnetic field lines along the axis of

produces a magnetic field, which is why compasses

the core have the most effect on the total magnetic field

work. Anytime an electrical current flows in a conductor,

inside the core. As a result of the external magnetic

a magnetic field is generated. That is why transformers,

fields, the saturation condition occurs either earlier or

inductors, and radio antennas work. There are several

later than would occur if we were only dealing with the

different devices that could be used to sense a magnetic

magnetic field of interest. Whether the saturation occurs

field. One of the most familiar to electronics hobbyists

early or later depends on whether the external field

is the Hall-effect device. However, in this chapter

opposes or reinforces the intended field.

we’ll take a look at a magnetic sensor that is as easy

to use, but is more sensitive, more linear, and more

temperature stable than typical Hall-effect devices.

And just like Hall-effect devices, it can be used to make

a variety of instruments, including magnetometers

Flux-gate magnetometer

and gradiometers.

The Earth Field Magnetometer project is illustrated in

For those unfamiliar with them, magnetometers

Figure 18-1 and the remotely located FM-3 flux-gate

are used in a variety of applications in science and

sensor is depicted in Figure 18-2.

engineering. One high-tech magnetometer is used by

Navy aircraft to locate submarines. Radio scientists use

The heart of the magnetometer is of course the

magnetometers to monitor solar activity. Earth scientists

flux-gate sensor. A compact low-cost line of flux-gate

use magnetometers to study diurnal changes in the

sensors are manufactured by Speake & Co. Ltd. and

Earth’s magnetic field. Archeologists use magnetometers

distributed in the United States by Fat Quarters

to locate buried artifacts, while marine archeologists

Software. The FGM-3 sensor is the device used in

and treasure hunters use the devices to locate sunken

wrecks and sunken treasure.

The Earth Field Magnetometer that we will be exploring

uses a “flux-gate magnetic sensor.” The device, in

essence, is basically an over-driven magnetic-core

transformer which the “transducible” event is the

saturation of the magnetic material. These devices

can be made very small and compact, yet will still

provide reasonable accuracy.

In its most simple form the flux-gate magnetic sensor

consists of a nickel-iron rod used as a core, wound,

Figure 18-1

Magnetometer

193

change, with a dynamic range of +/− 0.15 oersted

(about one-third the Earth’s magnetic field strength).

The output signal in all the devices in the FGM series

is +5 volt (TTL-compatible) pulse whose period is

directly proportional to the applied magnetic field

strength. This relationship makes the frequency of the

output signal directly proportional to the magnetic field

strength. The period varies typically from 8.5 µs to

25 µs or a frequency of about l20 kHz to 50 kHz. For

the FGM-3 the linearity is about 5.5% over its +/− 0.5

Figure 18-2

FGM-3 Magnetometer sensor

oersted range.

The response pattern of the FGM-x series sensors is

shown in Figure 18-3. It is a “figure-8” pattern that has

major lobes (maxima) along the axis of the sensor, and

this project. It is a 62 mm-long by 16 mm-diameter

nulls (minima) at right angles to the sensor axis. This

(2.44 by 0.63 inch) device. Like all the devices in the line,

pattern suggests that for any given situation there is a

it converts the magnetic field strength to a signal

preferred direction for sensor alignment. The long axis

with a proportional frequency. The FGM-3 sensor

of the sensor should be pointed towards the target

has only three leads: Red: +5 VDC (power), Black:

source. When calibrating or aligning sensor circuits, it is

0 volts (ground), and White: output signal (a square-

common practice to align the sensor along the east-west

wave whose frequency varies with the applied field).

direction in order to minimize the effects of the Earth’s

The output signal is a train of TTL compatible pulses

magnetic field.

with a period that ranges from 8 to 25 mS, or a

The flux-gate sensor is coupled directly to a special

frequency range of 40 to 125 kHz. The detection

interface chip, manufactured by Speake. This special

sensitivity of the FGM-3 device is +/− 0.5 oersted

SCL006A integrated circuit is shown in the main

(+50 utesla). That range covers the Earth’s magnetic

schematic diagram shown in Figure 18-4. It provides

field, making it possible to use the sensor in

the circuitry needed to perform the Earth field

Earth-field magnetometers. Using two or three sensors

magnetometry sensing. It integrates field fluctuations

in conjunction with each other provides functions such

in one-second intervals, producing very sensitive output

as compass orientation, three-dimensional orientation

variations in response to small field variations. The

measurement systems, and three-dimensional

magnetometer is of special interest to people doing

gimbaled devices such as virtual-reality helmet display

radio-propagation studies, and those who want to monitor

devices. It can also be used in applications such as

for solar flares. It also works as a laboratory magnetometer

ferrous metal detectors, underwater shipwreck

for various purposes. The SCL006A is housed in an

finders, and in factories as conveyer-belt sensors or

18-pin DIP IC package and is shown at U1. The FGM-3

counters. There are a host of other applications where a

small change in a magnetic field needs to be

detected.

The FGM series also includes two other devices, the

North

A

FGM-2 and the FGM-3h. The FGM-2 is an orthogonal

Maximum

Maximum

sensitivity

sensitivity

sensor that has two FGM-1 devices on a circular

B

platform at right angles to one another. That orthogonal

South

arrangement permits easier implementation of orientation

F/B

measurement, compass, and other applications. The

Ground (black)

FGM-3

16 mm

Out (white)

FGM-3h is the same size and shape as the FGM-3, but

+5 V (red)

62 mm

is about 2.5 times more sensitive. Its output frequency

Chapter Eighteen: Earth Field Magnetometer Project changes approximately 2 to 3 Hz per gamma of field Figure 18-3

FGM-3 Magnetometer sensor

194

+

+

R5

C7

C8

J1

A

O

I

3

Red

U4

R4

B

White

D1

White

Red

+

Sensor

R1

C

C9

Black

1

FGM-3

D2

Black

R3

1

18

Reset

2

17

S2

2

3

16

S3

C1

R2

X1

4

15

+9 –12 V

5

14

Gnd

U1

C2

Power

6

13

C3 +

7

12

2

3

Max

8

11

1

4

D3

9

10

Min

S1

Gain

O

I

U3

+

+

C6

C5

1

2

3

4 5

6

7

8

12

11

13

+

C4

10

9

14 15 16

R6

J2

Output

Output

195

Closed

Figure 18-4

Main magnetometer circuit

t

c

e

j

o

r

P

r

e

t

e

m

o

t

e

n

g

a

M

d

l

e

i

F

h

t

r

a

E

:

n

e

e

t

h

g

i

E

r

e

t

p

a

h

C

flux-gate sensor is coupled to the input pin at pin 17 of U1.

which can be fed to a computer’s serial port for

The reference oscillator of the SCL0006A is controlled

data-logging.

by components X1, C1, C2 and R2. A sensitivity

switch, S1, provides four positions, each with a

different overall sensitivity range. Switch S2 is used to

reset the SCL0006A, when applied for about two

Construction

seconds.

The second op-amp at U2, is an Analog Devices

The Earth-field magnetometer project was built on two

AD557 D/A converter. The magnetometer circuit is

printed circuit boards. The main circuit board is shown

designed so that it could be run from a 9 to 15 volt

in Figure 18-5, was constructed on a 31⁄2′′ × 41⁄2′′ PC

battery for use in the field. Power supplied from the

board, while the remotely located FGM-3 sensor was

battery is controlled by power switch S3 which

paired with a second 5-volt regulator shown in Figure

supplies 9 volts to the regulator. For stationary

18-6. Regulator U4 was mounted on a 2′′ × 3′′ PC

research, the magnetometer should be powered from an

board, which was attached to a sheet of flexible

110 volt AC to 9–15 volt DC power supply. The

plastic using plastic screws. The FGM-3 sensor probe

regulator U3 drops the 9 volt input supply power down

was then mounted on the 2′′ × 41⁄2′′ plastic sheet. The

to 5-volts to power the magneto-meter circuit. The

plastic sheet was used to mount the probe, ahead of the

output signal is a DC voltage that can be monitored by a

regulator in order to give the flux-gate probe some

strip-chart or X-Y paper recorder, a voltmeter or the

isolation from surrounding metal. The flux-gate probe is

signal can be fed into a computer using an

mounted length-wise and parallel to the length of the

A-to-D converter. In the prototype we used the output

PVC pipe. The FGM-3 sensor and remote regulator were

to drive a portable mini data-logger such as the

then housed in a 21⁄2′′ diameter × 12′′ long PVC pipe,

ONSET corporation HOBO H08-002-02. You will

which is separated by a length of three-conductor cable.

want to select the 2.5 volt model logger. You could also

Note that you could also elect to purchase a flux-

elect to use a digital multi-meter with RS-232 output

magnetometer kit including PC board, the FGM-3

3-conductor

cable

C7

C8

In

+

+

Main board

U4

Out

1

Red

A

Sensor

Red

White

2

White

B

FGM-3

+

C9

Gain

3

Sensor

Black

C

Min

Max

Black

1 2 3 4

Ground

Output

Output

S1

Gain

P1

S3

+9 –12 V DC

To meter

Power

or

A/D logger

Reset

Reset

S2

Recorder

Power

ground

ground

Chapter Eighteen: Earth Field Magnetometer Project Figure 18-5 Magnetometer connection diagram 196

Chapter Eighteen: Earth Field Magnetometer Project

Main

3-conductor

board

cable

White

B

P1

Power

Flux-gate

In

Out

Red

U4

sensor

+

+

White

Black

C

C7

C8

Ground

FGM-3

+

C9

Black

Figure 18-6

Flux-gate sensor board

sensor, ICs, and most other parts, but less the gain

First, refer to the chart in Table 18-1, which

switch, can be from Fat Quarters Software for about

illustrates the resistor color code. The resistor for this

$80.00.

project will have three or four color bands on them.

The first color band is closest to one end of the resistor

Are you ready to begin constructing the flux-gate

body. The first color band represents the first digit of

magnetometer? Before we begin you will want to secure

the resistor’s value, the second color represents the

a well lit and well ventilated work area, as well as a

second digit of the resistor value, the third color band

bench or large table for assembling your magnetometer

represents the resistor’s multiplier value, and the fourth

project. Locate a small pencil-tipped 27 to 33 watt

band denotes the resistor’s tolerance value. A silver

soldering iron, as well as a roll of 22 ga. 60/40 tin/lead

fourth band denotes a 10% tolerance value, while a gold

rosin core solder. Go to your local Radio Shack store

band represents a 5% tolerance value; no fourth color

and purchase a small jar of “Tip Tinner”; this is a

band denotes a resistor with 20% tolerance. Resistors

soldering iron tip cleaner/dresser compound, which

R1, R3, R4 and R5, for example, are 4.7k ohm types.

works wonders. You will also need a few hand tools for

The first color band is yellow, which represents a four

the project. You will need a pair of small end-cutters,

(4), while the second color band is violet or seven (7),

a pair of needle-nose pliers, a pair of tweezers, and a

and the third color band is red denoting a multiplier

magnifying glass. A small flat-blade screwdriver and a

of (100), so you see (4) (7) times (100) equals 4700 or

small Phillips screwdriver should round out your tool

4.7k ohms. Identify all of the 4.7k ohm resistors and

requirements.

place them on the circuit board at their correct location.

While you could build the magnetometer project on

Next, solder these resistors to the circuit board. Then

a perf-board or you could use point-point wiring it is

follow-up by cutting the excess component leads flush

recommended that you build the circuit on a printed

to the edge of the circuit board with your end-cutters.

circuit board for most reliable circuit operation and long

Now locate R2 and R6 and install them in their proper

life. Prepare your circuit board, and then we will be

locations, then solder them in place on the PC board.

able to go ahead and build the magnetometer receiver

Remember to trim the excess resistor leads with your

project.

end-cutter.

Locate all of the project diagram, such as the

Next we will move to identifying and installing the

schematic, parts layout diagrams and the

capacitors for the project. Capacitors are available in two

component pin-out sheets as well as the resistor and

major categories—electrolytic and non-electrolytic types.

capacitor identification tables and we will be almost

Electrolytic capacitors are generally both larger in size

ready to begin. Place all of the magnetometer project

and larger in value than non-electrolytic types.

components on the work bench in front of you,

Electrolytic capacitors have polarity and hence, they

warm up your soldering iron and let’s get going.

will have polarity marking on them to identify

197

Table 18-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

their leads. You will usually find a black or white

parts layout diagram and capacitor code chart before

colored band or a plus (+) or minus (−) marking near

installing them on the circuit board. Go ahead and place

one of the capacitor leads; this denotes the polarity. You

a few of the capacitors at their respective locations on the

will have to orient an electrolytic capacitor onto the

PC board and solder them in place. Remember to trim the

circuit board with respect to the capacitor’s polarity.

extra component lead length with your end-cutters.

When you mount electrolytic capacitors on the circuit

The magnetometer main circuit board utilizes three

board, you will have to refer to both the circuit

silicon diodes. Diodes have polarity and they must be

schematic and the parts layout diagrams in order to

installed correctly for the circuit to operate correctly.

install the capacitor properly. Failure to install

Each diode will have either a black or white colored

electrolytic capacitors correctly may result in damage to

band at one end of the diode body. The colored band

the capacitor itself and perhaps damage to the circuit as

represents the diode’s cathode lead, the opposite lead is

well. Non-electrolytic capacitors will generally be

the anode. Remember the diode’s electronic symbol is

smaller in value and physical size. Sometimes the non-

an arrow or triangle pointing to a vertical line. The

electrolytic capacitors will have their value printed on

vertical line is the cathode of the diode. Refer to the

them, and at other times the capacitor may be physically

schematic and parts layout diagram when mounting

very small when a three-digit code is used to identify

the diodes onto the circuit board. Place the diodes on

the capacitor. The chart in Table 18-2, helps to identify

the circuit board and solder them in place. Trim the

capacitors based on this code. Use the chart to help

excess leads as necessary.

identify the capacitors. You will want to make sure that

you install the correct value capacitor into the right

The magnetometer project employs a 10 MHz crystal

location on the circuit board in order for the circuit to

which is connected to pin 16 of U1. The crystal has no

work correctly. For example, a capacitor marked with

polarity so it can be placed in either direction on the

(102) denotes a value of .001 µF, while a capacitor with

board. Handle the crystal carefully so as to not break off

a marking of (103) denotes a capacitor value of .01 µF.

the leads from the crystal body.

Look through the component pile and identify the

Before we begin placing the semiconductors on the

Chapter Eighteen: Earth Field Magnetometer Project capacitors and what type they are and then refer to the PC board, you will want to refer to the semiconductor

198

Chapter Eighteen: Earth Field Magnetometer Project

Table 18-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Most capacitors actually have the numeric values stamped on them; however, some are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

820 pF

Ceramic

821

2

Mylar

205

199

(Top View)

(Top View)

•1

18

1 •

16

Output

Output

2

17

Common

Common

2

15

Input

Input

3

16

3

14

The common terminal is in electrical

The common terminal is in electrical

AD557

4

15

contact with the mounting base.

contact with the mounting base.

4

13

5

14

5

12

O

O

6

13

C

C

6

11

I

I

7

12

7

10

8

11

8

9

AD557

9

10

SCL006A

LM7805

LM7809

Figure 18-7

Semiconductor pin-outs

pin-out diagram shown in Figure 8-7, which will assist

PC board for possible “short” circuits. Often “short”

you in orienting the ICs. The magnetometer project

circuits can be caused by “stray” component leads or

utilizes two main integrated circuits which are rather

solder “blobs” which may have stuck to the underside

expensive, so we recommend using IC sockets. As a

of the PC board from solder residue. Look for solder

good insurance policy locate two IC sockets and solder

blobs or solder bridges which may be “shorting” or

them in place for U1 and U2. If an IC fails at some later

bridging between circuit traces on the PC board. With

date ‘down the road’, you can simply unplug the

the PC board free from any defect, we can continue on

defective one and replace it with a new one. Note that

and prepare for connecting the sensor and power-up the

the IC sockets will usually have a notch or cut-out at

circuit.

one end of the plastic package. The lead just to the left

The main magnetometer board was mounted on

of the notch is pin. You will have to make sure that

standoffs in a metal chassis box, as seen in Figure 18-8.

pin one (1) of each socket is connected to the correct

The on-off power switch and sensitivity rotary switch

components; refer to the schematic and parts layout

were mounted on the front panel of the chassis box,

diagrams. Note pin one (1) of U1 goes to the anode of

along with the meter binding posts. A 3-position screw

diodes D1 and D2, while pin one (1) of U2 is connected

terminal block or 3-circuit connector can be mounted on

to pin six (6) of U1. When installing the ICs into their

the side of the chassis box to allow the main circuit to

respective sockets, you will have to make sure pin one

connect to the remote sensor board.

(1) of the IC is placed into pin one (1) of the socket to

prevent damage to the integrated circuits.

It is a good time to take a short, well deserved rest

and when we return we will examine the main circuit

board for any possible “cold” solder joints or “short”

circuits. Pick up the main circuit board with the foil

side facing upwards towards you. Look over the main

circuit board, we will be looking at the solder joints for

possible “cold” solder joints. The solder joints should

all look clean, bright and shiny, if you see any solder

joints that look dull, dark or “blobby,” you will need to

un-solder the joint and remove the solder with a solder-

sucker and then re-solder the connection, so that the

Chapter Eighteen: Earth Field Magnetometer Project new solder joint looks good. Next we will examine the Figure 18-8

Magnetometer – inside view

200

Chapter Eighteen: Earth Field Magnetometer Project

Now refer to the sensor power supply circuit diagram

from line-voltage. A 24 volt center tapped transformer

shown in Figure 18-6. This diagram illustrates the

feeds AC to the 4-diode bridge rectifier package at BR1.

remote flux-gate sensor and power regulator PC board.

The DC output from the rectifier is filtered via C1 and

The sensor and regulator were placed on a small circuit

C2 and then sent to a 9 volt IC regulator chip at U1.

board, and in a water proof PVC cylinder so it can be

The output of the regulator chip is filtered at its output.

buried below the frost-line at about 4 feet underground.

This optional power supply will provide 9 volts which

The sensor should be placed well away from your

can be used to power the magnetometer circuit, if you

house, buried level in the ground with the ends of the

choose not to use a 9 to 12 “wall wart” power supply.

sensor facing East-West. The remote sensor is powered

The main circuit board was mounted on standoffs

from the main circuit board. You will want to place the

inside the bottom of the chassis box. Once you have

remote sensor and power supply in a non-metallic PVC

mounted the main circuit board and the controls, you

case and waterproof the case so water cannot leak inside

can locate a length of 20 to 24 gauge, three or four

the case. The sensor will need to be facing the outside

conductor cables and connect the sensor board to the

of the PVC cylinder away from the other electronics

main circuit board. Connect a digital voltmeter to the

inside the package. Use no metal fasteners to secure

output terminal binding posts and set the meter to read

the circuit to the PVC enclosure. You will have to

5 volts to 10 volts. Connect up your power supply to the

make provisions to allow the three conductor to exit

main circuit board and we can now test the

the opposite end of the PVC case away from the

magnetometer to see if it is working. Turn the power

sensor end.

switch to on, and set the meter range or gain switch to

The main magnetometer circuit board was placed in a

maximum sensitivity. With the sensor away from the

metal chassis which measures 6′′ × 3′′ × 2′′ as shown in

main circuit board and chassis, bring a small magnet

the photo. The power switch, power LED, gain switch

within rage of the sensor to say about 2 feet away.

and reset switch along with the output binding posts,

After about eight or ten seconds, you should see the

were mounted on the front of the chassis box. A four

effects of bringing the magnet near to the sensor. The

position terminal strip was mounted along the side of

reading will NOT be instantaneous, but you should see

the chassis box to allow the remote sensor to be

the meter read up to 2 volts or so. Move the magnet

connected to the main circuit. A coaxial power jack was

away and you should see the meter respond in 8 or

also mounted on the side of the chassis box to allow a

10 seconds. If all is well you will have a working

12 volt “wall wart” power supply to plug-in and power

portable flux-gate magnetometer, which can be

the circuit.

used for many applications such as monitoring diurnal

If you wish to construct your own power supply

magnetic Earth variations or solar storms. You can even

for the magnetometer project, refer to the diagram in

use the magnetometer as a UFO detector or driveway

Figure 18-9, which illustrates a 12 volt power supply

monitor.

PL1

117 V AC

24 V CT

S1

In

Out

T1

+V

U1

BR1

AC

+

+

+

+

C1

C2

C3

_

AC

Ground

Figure 18-9

Magnetometer power supply

201

If your magnetometer did not “spring-to-life” then

end cap. Try to use as little metal as possible when

you will have to turn off the circuit and remove the

mounting the sensor in the PVC pipe, use brass or

power supply, and look the circuit over carefully to

plastic screws where possible. A brass nipple fitting

make sure you didn’t install a component incorrectly.

cemented in the tapped hole allows the three conductor

Grab your schematic, parts layout diagrams and charts

cables to exit the probe assembly in the PVC pipe.

and let’s take a closer look at the circuit board.

Before cementing the final end cap to the PVC pipe

Remember we talked about certain components, like

you will want to test the Earth-Field magnetometer

capacitors and diodes having polarity. Make sure that

before burying the sensor probe assembly. Since the

you installed the electrolytic capacitors and diodes with

sensor is NOT an expensive temperature referenced

respect to their proper polarity; this is common cause

or compensated type sensor it is subject to extreme

for error. If need be, have another person, such as a

temperature variations, so if you live in the northern

parent or skilled technician or engineer or knowledgeable

climate zones, it will be necessary to mount the

friend, look over the circuit for you. The same person

sensor underground, below the frost-line, to prevent

looking over the same circuit numerous times often

temperature swings from affecting the reading of the

prevents you from finding your errors; you need a fresh

meter. In most frost-prone areas, you will need to

look from another person to catch mistakes. Another

mount the water-proof sensor assembly about 4′ to 41⁄2′

cause for error is placing the integrated circuits in the

underground. The sensor should be mounted as far away

wrong socket or in the wrong direction in the socket.

from metal objects and traffic as possible to ensure the

After looking the board over carefully, you can re-apply

best results. The sensor package should be mounted so

the sensor and power supply connections and test the

that it will face North-South as shown in Figure 18-3.

circuit once again, hopefully it will work fine this time

The output of the magnetometer can be connected to

around.

a logging digital multi-meter, so the imported data can

Once you know the magnetometer and sensor

be later analyzed by your personal computer. You could

circuits are working properly, you can make provisions

also use an inexpensive portable data-logger such as the

for mounting the sensor in a water-tight PVC case.

HOBO series from Onset Computers, or you could use

The remote flux-gate sensor probe was mounted in a

an analog to digital converter card in your PC to collect

21⁄2′′ × 12′′ length of PVC pipe. Circuit board guides

the data sample over time. If your meter is set to the

were epoxied to the inside of the PVC pipe to

most sensitive position, and everything is in working

allow the circuit board to be slid into the PVC pipe.

order, you should easily be able to monitor the Earth’s

One 21⁄2′′ end cap was cleaned and cemented to the

diurnal variations twice a day. You should also be able

outside probe end of the PVC pipe. A 1⁄2′′ hole was

to detect strong magnetic storms on the Sun, with your

drilled and tapped in the center of the second PVC

new magnetometer.

Chapter Eighteen: Earth Field Magnetometer Project

202

Chapter 19

Sudden Ionospheric Disturbance

(SIDs) Receiver

C8,C9

0.1 µF, 35 v

Parts list

ceramic capacitor

C10,C11

1000 µF, 35 v

SIDs Receiver

electrolytic capacitor

R1,R2,R3,R4

3.3 k ohm

D1,D2

1N914 silicon

1/4 w resistor

diode

R5

10k ohm potentiometer

D3,D4

1N34 germanium

(chassis mount)

diode

R6

1k ohm 1/

U1

LM353 op-amp

4 w resistor

(National

R7

100k

potentiometer

Semiconductor)

(PC mount)

U2

RC4136 op-amp (Texas

R8

100 ohm 1/4 w resistor

Instruments)

R9

10k ohm 1/4 w resistor

U3

79L09 - 5 volt

R10

470k ohm 1/4 w

regulator (− volts)

resistor

U4

78L09 - 5 volt

R11

56k ohm 1/4 w resistor

regulator (+ volts)

R12

22k ohm 1/4 w resistor

T1

600 to 600 ohm

R13

5k ohm

inter-stage/ matching

potentiometer

transformer

(PC mount)

L1

Loop antenna

C1

100 pF, 35 v ceramic

(see text)

capacitor

S1

DPST toggle switch

C2

1500 pF, 35 v mylar

(on-off)

capacitor

F1

.50 amp fast-blow

C3

.001 µF, 35 v ceramic

fuse

capacitor

BR1

bridge rectifier -

C4

1 µF, 35 v tantalum

50 v DC/2 amp

capacitor

PL1

117 VAC plug

C5

10 µF 35 v tantalum

Misc

PC board, IC

capacitor

sockets, wire, solder,

C6,C7

10 µF, 35 v

solder lugs, chassis

electrolytic

hardware, screws,

capacitor

standoffs, etc.

203

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

A sudden ionospheric disturbance (SID) is an

abnormally high plasma density in the ionosphere

VLF signal propagation

caused by an occasional sudden solar flare, which often

interrupts or interferes with telecommunications

Why do VLF signals strengthen at night instead of

systems. The SID results in a sudden increase in radio-

getting weaker? If propagation is basically via the

wave absorption that is most severe in the upper

waveguide effect, why doesn’t the signal drop DOWN

medium-frequency (MF) and lower high-frequency

at night when the waveguide disappears with the D

(HF) ranges.

layer? Is there some kind of reduced absorption at

When a solar flare occurs on the Sun, a blast of

night? If so, where is it taking place and why? Also,

ultraviolet and X-ray radiation hits the day-side of the

what accounts for the big fluctuations in signal strength

Earth after 8 minutes. This high energy radiation is

at night, apparently more or less at random?

absorbed by atmospheric particles raising them to

The strength of the received signal depends on the

excited states and knocking electrons free in the

effective reflection coefficient of the region from which

process of photo-ionization. The low altitude

the radio wave reflects in its multi-hop path between

ionospheric layers (D region and E region) immediately

Earth and the ionosphere. In daytime the reflecting region

increase in density over the entire day-side. The

is lower, the air density is higher, and the free electron

Earth’s ionosphere reacts to the intense X-ray and

density is controlled strongly by the solar radiation, etc.

ultraviolet radiation released during a solar flare and

At night time the reflecting region is higher, the air

often produces shortwave radio fadeout on the day-side

density is lower, and the free electron density is

of the Earth as the result of enhanced X-rays from a

controlled by variable ambient conditions as well as

solar flare.

variable influences from electron “precipitation” from

Shortwave radio waves (in the HF range) are

above, etc.

absorbed by the increased particles in the low

At noon the electron density is about 10 electrons/cm3

altitude ionosphere causing a complete blackout

at an altitude of 40 km, 100 electrons/cm3 at an altitude

of radio communications. This is called a Short Wave

of 60 km, 1000 electrons/cm3 at an altitude of 80 km

Fadeout. These fadeouts last for a few minutes to a few

and 10,000 electrons/cm3 at an altitude of 85 km.

hours and are most severe in the equatorial regions

where the Sun is most directly overhead. The

At night these figures become 10 electrons

ionospheric disturbance enhances long wave (VLF)

electrons/cm3 at 85 km, 100 electrons/cm3 at 88 km

radio propagation. SIDs are observed and recorded by

and 1000 electrons/cm3 at 95 km and then remains

monitoring the signal strength of a distant VLF

somewhat the same up to at least 140 km. At night the

transmitter. As the fadeouts occur, reception of the

electron density in the lower part of the D region pretty

SIDs Receiver station strength varies thus creating a fluctuating voltage much disappears. At 40 km the electron collision

output at the receiver which can be recorded and

frequency is about 1,000,000,000 collisions per second

observed using a computer with a chart recorder

whereas at 80 km the collision frequency drops to

program.

1,000,000 collision per second. The reflection coefficient

depends on (among other things) the number density of

You can build and investigate the phenomena of

free electrons, the collision frequency, and the frequency

SIDs with a special receiver and a low cost

of the radio signal. It is found by a mathematical

data-logger setup. You can not only observe when

integration throughout the entire D-region and of course

solar flares are occurring but you can collect and

the result depends on what time of the 24 hour day one

analyze the data and display it on your computer. The

performs the integration.

SIDs receiver is a great opportunity to observe first-

hand when a solar event occurs, but you can use it to

We can think of the E-Layer propagating the signal at

predict when radio blackouts will affect radio

night. Then the prominent sunrise pattern we see is a

propagation, which is extremely useful for amateur

shift from E-Layer propagation back to D-Layer as

radio operators.

the sun rises and forms the daytime D-Layer.

Chapter Nineteen:

204

Chapter Nineteen:

You can build your own Sudden Ionospheric

Disturbances (SIDs) receiver, shown in Figure 19-1, and

begin your own investigation of solar flares and their

effects on radio propagation. The SIDs receiver is a

simple VLF receiver designed to be used with a loop

antenna which can be placed either inside or outside.

The receiver monitors the strong VLF signal from the

US Navy NAA 24 kHz transmitter in Cutler Maine.

The Sudden Ionospheric Disturbance (SID) receiver

is a modified Stokes’ Gyrator tuned VLF receiver based

on the circuit from Communications Quarterly Spring

1994 pp. 24–26. The main circuit diagram shown is

Figure 19-2, it illustrates SIDs receiver which consists

of two integrated circuits, a Texas Instruments RC4136

and a National LF353 operation amplifier. The SIDs

SIDs Receiver

Figure 19-1

Sudden ionospheric disturbance receiver

receiver is fed from a loop antenna at L1. The antenna

is coupled to the SIDs receiver via a miniature 600 to

600 ohm matching transformer at T1. The output from

The sunset pattern is the reverse. An interesting feature

the secondary of T1 is fed to two protection diodes at

of waveguide mode propagation was that the signal was

D1 and D2 at the front end of the receiver. The output

split into two components which can form an

of the diode network is then coupled to a 100 pF

interference pattern.

capacitor at C1. Capacitor C2 is connected from the

U2:D

+V

C4

13

11

R9

12

+V

+V

U2:B

U2:A

14

7

C2

R3

T1

C1

5

11

–V

+

2

11

–V

–

+

4

9

8

D2

–

L1

6

7

3

1

7

+–

+V

11

7

D4

D3

R7

C3

R1

R13

–V

10

–V

R2

R5

U2:C

D1

R4

+V

U1:A

R10

Output

1 8

3

(A)

+

–

R6

4

2

+ C5

–V

R12

R11

R8

M1

Figure 19-2

Sudden ionospheric disturbance receiver

205

output of C1 to ground at the input of the first op-amp

Once you have gathered all the tools, locate all the

stage U2:B. Integrated circuit sections U2:A and U2:B

circuit diagrams, such as the schematics, the parts layout

form an amplifier/filter and tuning. The “tuning” is

diagram, the resistor and capacitor code charts, etc.

controlled via R6, which is placed in a shielded

Place all the component parts, along with all your tools

enclosure to prevent circuit oscillation. The potentiometer

and diagrams, in front of you, warm up your solder iron

is kept separate in a small shielded box formed by some

and we will start building the SIDs receiver project.

scrap pieces of thin circuit board soldered together.

First we will identify the resistors for the project.

The output from U2:A is next fed to IC:D and U2:C

Refer to the chart shown in Table 19-1, which will help

which forms an amplifier/integrator section. A final

you to identify the resistor color codes. Resistors

buffer amplifier section at U1 is used to drive the

usually have three or four color bands on the body of

0-1 mA meter at the output. The output of the SIDs

the resistor which denotes the resistor value. The color

receiver at (A) can be coupled a low cost data-logger

bands begin at one end of the resistor body close to the

in order to record signals over time.

edge. The first color band on resistor R1 is orange, this

The SIDs receiver was built on a circuit board circuit

denotes the digit three (3). The second color band is

board, for most reliable operation, but other types of RF

also orange, which is the digit number three (3), and the

building techniques could be used. The circuit board is

third color band is the resistor’s multiplier value which

available from FAR Circuits—see Appendix. Before we

is red, and this suggests a multiplier value of 100. So

begin building the circuit take a few minutes to locate a

the resistor value for R1 is (3) times (3) times (100) or

clean well lit work table or work bench. You will want

3.3k or 3300 ohms. The tolerance value of a resistor is

to locate a small 27 to 33 watt pencil-tipped soldering

noted in the four color band. A fourth color band which

iron, a roll of 60/40 tin/lead rosin core solder, and a

is silver is a 10% tolerance resistor, while a gold fourth

small jar of “Tip Tinner,” a soldering iron tip

band denotes a 5% tolerance value. If there is no fourth

cleaner/dresser. “Tip Tinner” is available at a local

color band then the resistor will have a 20% tolerance

Radio Shack store. You will also need some small hand

value. Once you have identified resistor R1, you will

tools, such as a small flat-blade screwdriver, a Phillips

note that resistors R1, R2, R3 and R4 all have the same

screwdriver, a pair of small needle-nose pliers, a pair of

color codes, therefore they all have the same value.

tweezers, a magnifying glass and a pair of end-cutters.

Check your parts layout diagram and the schematic to

Table 19-1

Resistor color code chart

SIDs Receiver

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Nineteen:

No color

20%

206

Chapter Nineteen:

see where these resistors are to be placed on the circuit

Let’s go ahead and identify the non-polarized

board. Once you verify where the resistors are placed,

capacitors first. Check the capacitor code chart and make

you can install all four resistors on the circuit board and

sure that you can identify each of the non-polarized

solder them in place on the board. Now locate your

capacitors. In groups of two or three capacitors install

end-cutter and trim the excess component leads. Cut the

them on the PC board. When you have determined that

extra component lead lengths flush to the edge of the

you have installed the correct values into their respective

circuit board. Now go ahead and identify another group

location on the circuit board, you can solder the

of three or four resistors and place them on the circuit

capacitors in place on the board. Remember to trim the

board. Once you are sure of their respective locations

excess capacitor leads from the circuit board. Once you

you can solder the next grouping of resistors onto the

have the first grouping of capacitors installed you can

circuit board, remember to trim the excess component

move on to installing another group of non-polarized

leads from the board. Place all the remaining resistors

capacitors, until you have installed all of the

on the circuit board and solder them all in place, trim

non-polarized capacitors.

the extra leads as necessary.

Next, find the electrolytic capacitors from the parts

SIDs Receiver

Now we will move on to installing the capacitors for

pile and we will install them in their proper locations.

the SIDs receiver project. Capacitors come in two major

Refer now to the schematic and parts layout diagrams

flavors, non-polarized and polarized types. First, we will

so that you can orient the capacitors correctly when

talk about non-polarized capacitors. Usually non-polarized

mounting them on the PC board. Install two or three

capacitors are smaller value types which could take form

electrolytic capacitors and then solder them in place on

as ceramic disks, mica, tantalum or polyester types.

the PC board. Remember to cut the extra lead lengths

Often the capacitors are small in size and frequently the

flush to the PC board. Identify and install the

capacitor values are printed as three-digit codes rather

remaining electrolytic capacitors on the board and

than their actual values, since this code system takes

solder them in place. Trim the component leads as

less space to print. We have included a chart in

necessary.

Table 19-2, which lists the actual capacitor values and

The SIDs receiver employs two silicon diodes at the

their respective codes. For example, a capacitor with a

“front-end” and two germanium diodes near the final

value of .001 µF will have a code designation of 102,

output stage. Diodes have polarity so they must be

a .01 µF capacitor will have 103, and a 0.1 µF capacitor

installed in the proper orientation for the circuit to

will have a code of 104 marked on it. The SIDs project

function properly. Diodes will generally have either a

has a number of non-polarized type capacitors which

white or black band on the side of the diode’s body.

you will need to install. Take a look through the

The colored band denotes the cathode of the diode.

component pile and see if you can identify the small

Remember that a symbol for a diode is a triangle

non-polar capacitors before attempting to install them

pointing to a vertical line. The vertical line is the

on the PC board.

cathode of the diode. Make sure you install the proper

diodes in their proper locations with respect to polarity:

Polarized capacitors are called electrolytic capacitors,

you will need to refer to the schematic and parts layout

and they are often larger in physical size. Electrolytic

diagrams.

capacitors will always have some sort of polarity marking

on them. You will see either a black or white band or a

The SIDs receiver uses two integrated circuits at U1

plus (+) or minus (−) marking somewhere on the capacitor

and U2. Integrated circuit sockets are highly recommended

body. It is very important that you install these types of

as an insurance policy against any possible failure in the

capacitors with respect to their polarity in order for the

distant future. Before we go ahead and install the

circuit to work properly and to not be damaged upon

semiconductors, take a quick look at the semiconductor

power-up. You will need to refer to the schematic and

pin-out diagram shown in Figure 19-3. The pin-out

parts layout diagrams when installing electrolytic

diagram will assist you install the integrated circuits.

capacitors to make sure that you have installed them

IC sockets are inexpensive and will greatly be appreciated

correctly. The plus (+) marking on the capacitor will point

in the event of a circuit failure, since most people

to the most positive portion of the circuit.

cannot un-solder a 14 or 16 pin integrated circuit

207

Table 19-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Most capacitors actually have the numeric values stamped on them; however, some are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

SIDs Receiver 82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Nineteen: 820 pF

Ceramic

821

2

Mylar

205

208

Chapter Nineteen:

(TO-92)

1

14

(TO-92)

Plastic Package (Z)

1

8

1

14

Plastic Package (Z)

1

8

GND

OUTPUT

2

13

OUTPUT

INPUT

2

7

3

6

3

12

4

5

4

11

LM353

5

10

6

9

GND

INPUT

00774400

00774802

7

8

Bottom view

Bottom view

RM4136

LM78L05

LM79L05

Figure 19-3

Semiconductor pin-outs

without damage to the circuit board. Integrated circuits

of time the use of a dual voltage AC power supply is

must be installed correctly for the circuit to work

recommended. The diagram shown in Figure 19-4

SIDs Receiver

properly. Looking at the IC, you will notice a small

illustrates a simple dual plus and minus voltage power

notch or cut-out or small indented circle at one end of

supply which can be used to power the SIDs receiver.

the IC body. Pin one (1) of the IC will be just to the

A 9 volt 500 mA center tapped transformer was used to

left of this cut-out or notch. The IC socket will often

drive a bridge rectifier, which provides both a plus and

appear the same way with a notch or cut-out with pin

minus voltage that is sent to a 9 volt plus regulator.

one (1) to the left of the notch or cut-out. You must

An LM78L09 regulator and the minus leg of the bridge

orient pin of the IC with pin 1 of the IC socket, and

is sent to an LM79L09 minus 9 volt regulator. The

you must them be sure to orient pin of the IC socket

power supply could be built on perf-board or on a

to match up with the proper components on the circuit

printed circuit board if desired. The power supply and

board. For example, pin one (1) of U1 is connected to

SIDs receiver could be mounted alongside one another

the output of the circuit at the junction of R8 and R11.

in the same chassis.

Note that pin 8 is the plus power supply input, while pin

Take a short break and when we return we will

4 is the ground on U1. Pin one (1) of U2 corresponds to

inspect the circuit board for any possible “cold” solder

the minus (−) INPUT #1 at U2:A, which is connected to

joints or “short” circuits. Pick up the circuit board so

the junction of R1 and R2.

that the foil side of the PC board faces upwards toward

A small metal compartment should be placed around

you. Look over the foil side of the board very carefully.

the main tuning potentiometer R6 in order to shielded

The solder joints should all look clean, bright and shiny.

this control. This can be done with the use of some

If you see any solder joints that look dull, dark, dirty

scrap circuit board material which can be soldered

or “blobby” then you should remove the solder and

together to form a small box. You will have to use a

re-solder the joint so that it looks clean, bright and

soldering gun or a higher temperature soldering

shiny. Next we are going to inspect the PC board for

iron, in order to solder large areas of circuit board

any possible “short” circuits. Sometimes “cut”

material.

component leads will “stick” to the board from solder

The output of the SIDs receiver is fed to the 0-1 mA

residue left on the board. These “stray” wires can often

analog meter at M1. The output of the SIDs monitor can

cause a “short” between the solder traces. Also look

also be fed to the input of an analog to digital converter

closely for any solder “blob” or “solder balls,”

place in a personal computer, for recording over long

which may have stuck to the underside of the

lengths of time.

PC board.

Since the SIDs receiver utilizes integrated circuits

The SIDs receiver and power supply can both be

which require the use of a dual power supply providing

installed in a metal chassis box enclosure. The

both a plus and minus voltage to the circuit, and since

prototype receiver was mounted in a sloping cabinet as

the circuit is meant to be left on for long periods

in Figure 19-1. The power supply was mounted alongside

209

PL1

S1

C6

+

F1

24 V CT

1

3

T1

+

BR1

U3

+

+

C10

C8

AC +

2

117 V AC

Ground

AC –

1

3

–

U4

C11

C9

C7

2

+

+

+

Figure 19-4

Dual voltage power supply

the SIDs receiver. The tuning control as well as the

loop antenna should form a loose twisted pair.

power on-off switch and meter were all mounted

This balanced lead-in is routed as far away from

on the front panel of the enclosure. The power cord was

metal as possible to the 600 to 600 ohm matching

led out of the rear panel through a stain-relief. A power

transformer at T1. This transformer arrangement

fuse was installed inside a chassis mounted fuse

reduces 60 Hz hum interference from entering the SIDs

holder on the rear of the panel. A dual binding

receiver.

post/banana chassis jack was mounted on the top of the

The output of the SIDs receiver can be coupled to a

chassis to connect the antenna loop to the SIDs receiver.

solid state data-logger from the output of the receiver at

An RCA jack was placed on the rear of the chassis to

point (A) at the receiver output terminals. In order to

allow the receiver to connect to an analog to digital

save and later view and correlate your recorded data

converter.

you will need to acquire some form of data-logger.

The SIDs receiver requires a rather large loop

There are three good options for saving your data. The

antenna, which can be placed inside your attic or placed

first option is the Onset Computer HOBO series of

outside away from large metal structures or aluminum

data-loggers. Onset offers a number of different

SIDs Receiver siding, in a sheltered area. The coil at L1 is a diamond models from 8-bit to 12-bit models which are

shaped loop antenna as shown in Figure 19-5. The loop

reasonably priced from around $60.00. The data-loggers

consisting of 50 turns of solid #24 enameled or plastic

are powered by a small button battery which will last

coated wire, on a PVC pipe square or diamond form.

for a long time. Onset also offers low cost software for

The loop has an enclosed area of about 9 square feet.

up/downloading information to the data-logger.

Locate four 21⁄2′′ diameter × 24′′ long pieces of

Starting times and dates can be preset as well as

PVC pipe and form a square or diamond shape coil

voltage parameters and timing between samples. These

form as shown. A PVC elbow was placed on top and

are a great alternative. Another data-logger option is the

both sides of the loop form as shown, while a PVC

new introductory “starter package” from Dataq DI-

“T” was used at the bottom of the loop form to allow

194RS 10-bit resolution PC data-logger kit for $24.95.

winding of the coil around the four protrusions at each

This data-logger option is a real bargain, providing both

leg of the loop. The four hole center hub holds the loop

hardware and software and it can get you started

form together. The main vertical PVC pipe was secured

recording data in just a short time. The company

into a flange which was fastened to a wooden block at

offers many other data recorder options as well.

Chapter Nineteen: the base of the loop antenna. The lead-in from the

Check their website for details http://www.dataq.com.

210

Chapter Nineteen:

on the circuit board. Ask a knowledgeable

electronics enthusiast to help you inspect the circuit

board for errors. Having completed the inspection, and

hopefully an error was found, you can reconnect the

antenna and power supply and then re-test the

receiver.

SIDs research

opportunities

You can join the foremost group involved with SIDs

research. The AAVSO or American Association of

SIDs Receiver

Variable Start Observers SID Program consists of solar

observers who monitor very low frequency (VLF) radio

stations for sudden enhancements of their signals.

Earth’s ionosphere reacts to the intense X-ray and

ultraviolet radiation released during a solar flare. The

Figure 19-5

Loop antenna

ionospheric disturbance enhances VLF radio propagation.

By monitoring the signal strength of a distant VLF

In normal operation, the SIDs receiver would be

transmitter, sudden ionospheric disturbances (SIDs) are

permanently tuned to a powerful VLF station such as

recorded and indicate a recent solar flare event. All SID

(NAA), the powerful US Navy 24 kHz VLF transmitter

monitoring stations are home built by the observers.

station in the state of Maine, and your data-logger or

The SID station operates unattended until the end of

A/D converter would constantly monitor the signal

each month. Recordings are then analyzed for the

from NAA to record propagation changes on your

beginning, end, and duration of SID events. A simple

personal computer for study. Once the receiver has

A/D converter design for specific use with the VLF

been completed, you can attach the antenna, power

receivers is available by contacting the chairman. SID

supply and data recorder. Connect the output of the data

observers submit strip-charts or computer plots to the

recorder to your personal computer and you are ready

SID coordinator for visual inspection at the end of each

to begin recording. Now turn on the receiver and you

month. Many observers analyze their own stripcharts

should see a signal on your computer chart recorder

and computer plots. Analyzed results are submitted via

display. If you remove the antenna from the circuit the

e-mail to the SID Analyst for correlation with other

output should go to zero or base-line. If your SIDs

observers’ results. The final SID report combines

receiver does not appear to work, then you will need

individual observers’ reports with the SID Coordinator

to disconnect the power supply and data recorder and

visual analysis. SID event results are sent monthly to

antenna and inspect the circuit board for possible

the National Geophysical Data Center (NGDC) for

errors. The most common cause for circuit failure after

publication in the Solar-Geophysical Data Report where

building a new circuit is the improper installation of

they are accessed by researchers worldwide. The

components, such as electrolytic capacitors, diodes and

reduced SIDs data and particularly interesting plots are

semiconductors such as transistors or integrated circuits.

reproduced in the monthly AAVSO Solar Bulletin

You may also want to check the placement of resistors

mailed to all contributing members.

211

Chapter 20

Aurora Monitor Project

R11

50k ohms, panel-

Parts list

mount potentiometer

R13

200k ohms, 1/ watt,

Aurora Monitor:

4

5% resistor

Sensor Head Unit

R14

3 megohm, 1/

watt,

R1,R2

1.5 megohm 1/ watt,

4

4

5% resistor

5% resistor

R15

1 megohm, PCB

R3

5.6 megohm, 1/ watt,

4

trimmer potentiometer

5% resistor

R16

1 megohm, 1/ watt,

R4

100 k potentiometer

4

5% resistor

PCB trimmer

R17

1 megohm,

R5

10 megohm 1/ watt,

4

panel-mount

5% resistor

potentiometer

C1,C2,C3

.1 µF, 35 volt

R18,R19

5k ohm

disk capacitor

panel-mount

D1

1N914 silicon

potentiometer

diode

R21

1k ohm, 1/ watt,

4

LM4250

low noise/high

5% resistor

gain op-amp

R22

100 ohms, 1/ W,

2

L1

sensing coil, see

5% resistor

text

R23

4.7k ohms, 1/ watt,

4

B1,B2

1.5 volt “C” cell

5% resistor

battery

C4

0.005 µF, 25 volt

J1

RCA input jack

ceramic disk capacitor

Misc

PC board, coil

C5,C7,C9,C10

0.1 µF,

form, wire, coax, etc.

25 volt ceramic disk

Control/Display Unit

capacitor

R6

18 k ohms, 1/ watt,

C6

0.02 µF, 25 volt

4

5% resistor

ceramic disk capacitor

R7

12k ohms, 1/ watt,

C8

4.7 µF, 25 volt

4

5% resistor

aluminum electrolytic

R8,R9,R12,R20

capacitor

10k ohms, 1/ watt,

C11

.010 µF, 25 volt

4

5% resistor

disk capacitor

R10

30k ohms, 1/ watt,

(optional)

4

5% resistor

C12

1 µF, 35 volt

212

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Twenty:

aluminum electrolytic

The Aurora Borealis is one of nature’s most spectacular

capacitor

nighttime displays. Shimmering curtains of green,

D1,D2,D3,D4

1N914

white, and even red light dance in the northern skies.

silicon diodes

Visible effects of charged particles from the Sun raining

down on the Earth’s ionosphere, northern lights or

Q1

2N2907 PNP

auroras, are visible in the northern night sky during high

transistor

sunspot activity. The Aurora Australis, the southern

Q2,Q3

2N394, NPN

hemisphere’s counterpart of the Aurora Borealis, can be

transistor

seen at night by looking toward the south pole.

U1

LM4250 low noise

These displays of undulating light are formed when

op-amp (National

flares from the Sun’s surface (sunspots) launch showers

Semiconductor),

of high-energy ionized particles and X-rays into space.

U2

LTC1062 (Linear

Mostly electrons, the showers stream out from the sun

Technology)

and are attracted by the Earth’s magnetosphere, an

invisible magnetic field around the Earth.

U3

LM201A dual op-amp

Aurora Monitor Project

(National

Shaped like a pumpkin, the magnetosphere terminates

Semiconductor)

at both magnetic poles but is many miles thick above

the equator. Dimples at both poles form “sinks” that

U4

LM747 op-amp

funnel the particles toward the poles where they ionize

(National

the gas in the ionosphere. Those collisions induce the

Semiconductor)

gases to emit their characteristic light wavelengths—as

S1

DPDT toggle power

in neon signs and fluorescent lamps.

switch

The charged particle bombardment of the

S2,S4

SPST toggle

magnetosphere initially compresses it, temporarily

switches

increasing the strength of the Earth’s geomagnetic field.

S3

3-position rotary

The aurora monitor described here is sensitive enough

switch, break before

to detect changes in the field caused by those “magnetic

make

storms.” Thus it can indirectly sense sunspots and

M1

100-micro-ampere

predict the presence of auroras in the night sky.

moving-coil panel-

The monitor also senses changes or anomalies in the

mounted meter

magnetic field caused by large metal objects such as

SPKR1

8 ohm speaker,

cars or trucks moving near the monitor. This permits it

2” dia.

to act as an intrusion detection monitor able to detect

the approach of vehicles at night in restricted areas. The

B1,B2,B3,B4

1.5v (AA)

monitor can also detect the presence of permanent

or (C) cells (+) plus

magnets (such as those in speakers), and stray fields

voltage supply

from AC-power lines.

B5,B6,B7,B8

1.5v (AA)

Early warning of auroras will both permit you to

or (C) cells (-)

observe them in the night sky or use them for boosting

minus voltage supply

the range of your amateur radio transmissions. Auroras

J2,J3

RCA jack

and their accompanying magnetic storms generally

Misc

PC board, chassis,

block or scramble the lower radio frequencies, but the

wire, coax, hardware,

higher frequencies can overcome this interference.

standoffs, RTV

Radio amateurs aim their antennas north during those

compound,

storms, thus taking advantage of the phenomena to

washers, etc.

reach other hams on the opposite side of the Earth that

213

of one meter, which corresponds to one milligauss.

(The Earth’s magnetic field is about 0.5 ga.)

The control/display unit contains an active filter,

additional amplification circuitry, a moving-coil

ammeter, and an audio oscillator with speaker.

Figure 20-1 shows the front-panel controls and indicators

of the monitor: moving-coil ammeter, SENSITIVITY,

RATE, and ALARM ADJUST potentiometers as well as

power (OFF), filter-in and RANGE switches.

Figure 20-1

Aurora monitor

The sensor head unit

could not be contacted during periods of low sunspot

activity.

The sensor head schematic circuit is illustrated in

In addition to scrambling low-frequency radio

Figure 20-3. Gain is provided by U1, a National

communications, the magnetic storms caused by auroras

Semiconductor LM4250 programmable operational

can induce large currents in power transmission lines.

amplifier. It is protected from over voltage and

Those currents can cause overload, plunging large

transients by diode D1 and D2, and its overall gain is

regions of the country into darkness. Auroras and

set by resistors R1 and R2. The output of U1 is driven

related magnetic storms are quite common during the

to zero or balanced by network R3 and R4. Its output

decreasing parts of the 11-year sunspot cycle such as

should remain at zero as long as no changes occur in the

the period we are now in.

ambient magnetic field.

The Aurora Monitor consists of two main

Bypass capacitors C2 and C3 are placed across

components, a sensing head and the control/display unit

the positive and negative power supply. Power for the

which are connected by a coaxial cable. The sensing

sensing amplifier is obtained from two “C” cells.

head contains a sensing coil, a DC nano amplifier

The sensor circuit draws very little current, so it can be

capable of current amplification of 500, and a separate

left on at all times, thus eliminating the power switch.

power pack, all enclosed in the tubular case shown on

the right side of Figure 20-1. Figure 20-2 illustrates the

interior of the Aurora Monitor prototype. The Aurora

Monitor is sensitive to a pulse of one ampere at distance

The control/display unit

Aurora Monitor Project

The control/display circuit schematic is depicted in the

schematic in Figure 20-4. It provides an additional gain

of 200 over that of the sensor circuit. The

control/display circuit includes an adjustable low-pass

notch filter, U2, a Linear Technology LTC 1062. By

adjusting the clock frequency of the filter with resistor

RI1 and the capacitors C4, C5 and C6, the filter cancels

interference frequencies and noise in the 2 Hz to 10 kHz

band. The notch filter can also screen out 60 Hz noise.

Switch S2 inserts or removes the filter. U3, an LM201A

general purpose op-amp, filters out the clock noise

generated within the filter chip. The output of U3 is fed

into the non-inverting input of U4-A, half of a dual 747

general purpose op-amp. The overall gain of U4-A is

Chapter Twenty: Figure 20-2 Aurora monitor console and sensor adjusted by resistor R16. Trimmer potentiometer R15

214

Chapter Twenty:

+1.5 V

C3

R3

R2

L1

2

7

Soft

6

iron

D1

D2

U1

J1

core

8

3

4

1

5

R4

+1.5 V

–1.5 V

R1

C1

R5

C2

1.5 V

1.5 V

Aurora Monitor Project

B1 –

+ B2

–1.5 V

Figure 20-3

Aurora monitor sensor head

adjusts the offset or balance. PULSE SHAPE

Transistor Q1 controls the audible alarm by clamping

potentiometer R17 and capacitor C5 form an optional

the negative voltage returning through the ground path.

pulse-shaping network for coupling the Aurora Monitor

When a magnetic event occurs, the speaker emits an

to a chart recorder or an analog-to-digital conversion

audible alarm, and the meter gives a visual indication of

board of a personal computer.

a changing magnetic field. The adjustment of ALARM

ADJUST potentiometer R24 can remove distortion from

The output of U4-A is coupled to a voltage follower

the sound of the speaker.

at U4-B. The output of U4-B is divided into two

channels. One channel is fed through 5000-ohm

The author’s prototype control/display unit is

SENSITIVITY potentiometer R18, which adjusts the

powered by eight AA cells: four cells provide positive

output level of the signal fed to the 100-microampere

voltage and four cells provide negative voltage. As an

panel meter MI. Movement of the meter’s needle shows

alternative, the monitor can be powered by rechargeable

changes in the local magnetic field. Potentiometer R18

nickel-cadmium cells.

also adjusts the output signal that can be fed to a chart

recorder for data-logging.

The other channel is fed through ALARM ADJUST

Construction

5000-ohm potentiometer, R19, which sets the

threshold or set-point for the reflex oscillator circuit

In order to begin constructing the Aurora Monitor, you

that follows it. The oscillator consists of transistors Q1,

will need to secure a clean will lit work table or work

Q2, and Q3 and associated components. Speaker

bench so you can spread out all the tools, project

SPKR1 gives an audible indication of changes in the

components, charts and diagrams. You will need to

local magnetic field. The network of diode D3 and

locate a small 27 to 33 watt pencil-tipped soldering iron,

aluminum electrolytic capacitor C8 performs additional

a small roll of 60/40 rosin core solder, a small jar of

filtering for the input signal to the reflex oscillator

“Tip Tinner,” soldering iron tip cleaner/dresser, from

section.

your local Radio Shack store. A few small hand tools

215

C h a p t e r T w e n t y : A u r o r a M o n i t o r P r o j e c t 216

+6 V

R24

+6 V

R14

Out In

R8

R12

b

Q1

c

R20

R21

C7

c

S2

R6

R13

T1

R15

R22

C9

c

R7

R10

J2

+6 V

b

9

–6 V

1

R16

Q2

+6 V

–

13

e

4

R9

8

12

2

7

U4:A

6

c

U2

U3

+

4

2

D3

R23

6

3

3

R19

3

–

4

Q3

10

b

+6 V

C10

5

2

U4:B

c

6

+

–6 V

+

C8

R11

–6 V

S1

D4

R17

S4

R18

C4

C5

C6

+

–

B1

B2

M1

–6 V

C11

Recorder

C12

S3

–

+

J3

Figure 20-4

Aurora monitor display/control unit

Chapter Twenty:

are also required to construct the project. You should

color band would be brown or one (1), the second color

locate a small pair or end-cutters, a pair of needle-nose

band would be green or five (5), and the third color or

pliers, a pair of tweezers, a magnifying glass a small

multiplier would be green or (100,000). Go ahead and

flat-blade screwdriver and a small Phillips screwdriver.

locate resistors R1 and R2 which are used in the sensor

The Aurora Monitor project was constructed on two

head unit and place them on the sensor head PC board

circuit boards, one for the sensor head unit and a second

in their respective locations. Solder them in place and

PC board for the control display unit. We will begin

then trim the excess component leads with your

constructing the sensor head unit first, see the schematic

end-cutter. Cut the excess leads flush to the edge of

in Figure 20-3. The sensor head board measured 2 1⁄

the circuit board. Next locate the remaining resistors on

16

by 2 9⁄

the sensor head unit and populate the board. Solder the

16, it was housed along with the sensor head coil in

a suitable PVC pipe housing.

resistors to the board and trim the excess leads.

Place the project components in front of you on the

Next we are going to install the capacitors on the

table, locate the resistor and capacitor identifier charts

sensor head unit of the Aurora monitor. Capacitors are

in Tables 20-1 and 20-2, heat up your soldering iron and

listed as electrolytic or non-electrolytic types.

we will begin. First refer to the resistor identifier chart,

Non-electrolytic types are usually small capacitors, often

Aurora Monitor Project

it illustrates the resistor color codes and their

they are so small that their actual value is not printed on

representative values. Most resistors will have three or

the body of the capacitor but a three-digit code is used,

four color codes on the body of the resistor. The color

see Table 20-2. For example, a .01 µF capacitor would

codes begin at one end of the resistor’s body. The first

be marked (103) while a .1 µF capacitor would be

color band denotes the first digit of the resistor value,

marked (104). Locate capacitors C1, C2 and C3 which

while the second color band represents the second digit

are .1 µf values. Place them on the sensor head PC

of the resistor code. The third color band on the resistor

board and solder them in place on the board, remember

denotes the multiplier value of the resistor, and the

to trim the excess component leads with your end-

fourth color code represents the tolerance of the resistor.

cutters. There are no electrolytic type capacitors on the

A silver band notes a 10% tolerance value, while a gold

sensor head unit but there are some on the

band denotes a 5% resistor, and the absence of a fourth

control/display PC board. Electrolytic capacitors are

band implies a 20% tolerance for the resistor. For

usually larger in size and value, and usually they will

example, resistor R1 has a 1.5 megohm value. The first

have a polarity marking of some kind on the body

Table 20-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

217

Table 20-2

Capacitor code identification information

This table is designed to provide the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules.

Most capacitors actually have the numeric values stamped on them; however, some are color coded and some have alphanumeric codes. The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

Aurora Monitor Project 75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Twenty: 820 pF

Ceramic

821

2

Mylar

205

218

Chapter Twenty:

1

8

1

8

1

8

1

14

1

8

1

8

1

8

1

14

2

7

2

7

2

7

2

13

3

6

3

6

3

6

4

5

4

5

4

5

3

12

LM4250

LM1062

LM201A

4

11

5

10

6

9

7

8

LM747

Figure 20-5

Semiconductor pin-outs

of the capacitor. You will find either a plus (+) or minus

core 1⁄2′′ in diameter and 10′′. (The iron core

(−) marking near one of the leads on the capacitor body.

concentrates the flux lines by offering a lower

Both the sensor head and control/display board utilize

reluctance path than air.)

silicon diodes. Diodes also have polarity, so they must

Wind the fine insulated magnet wire carefully on the

be installed correctly in order for the circuit to work

Aurora Monitor Project

iron core to avoid kinks and breakage. Tape the ends of

properly. Look closely at a diode and you will see either

the winding temporarily to the core and carefully solder

a white or black color band near one end of the diode

hook-up wire at each end to form permanent

body. The colored band indicates the cathode end of the

terminals. The terminals can be secured to the core

diode. Go ahead and install D1 on the sensor head board.

with room-temperature vulcanizing (RTV) adhesive to

The sensor head and the display boards both have

relieve any strains that might develop in the fine

integrated circuits on them, so before we begin installing

magnet wire.

the ICs, take a quick look at the pin-out diagram depicted

In the prototype, the sensing circuit board, coil, and

in Figure 20-5, which will help you orient the integrated

battery pack, consisting of two “C” cells were housed in

circuits. Integrated circuits are highly recommended as an

a case made from standard diameter PVC water pipe cut

insurance against possible circuit failure at some later

to a length that will accommodate all of those elements

date. It is much easier to simply unplug an IC and place a

as shown in Figures 20-6.

new one in the socket rather than trying to un-solder a

The covers for the sensing head housing are PCV

14 or 16 pin IC from a circuit board. Integrated circuit

end-caps that press-fit over the 23⁄8′′ outside diameter of

sockets will usually have a notch or cut-out at one end of

the pipe. The upper cap is a simple cup, but the lower

the plastic IC socket. To the immediate left of the notch or

cap is a sleeve with a threaded insert at its end. Drill a

cut-out you will see pin one (1) of the socket. Pin (1) of

hole in the square base of the threaded insert for jack J1

U1 is connected to one end of potentiometer R4. The IC

and fasten it with a ring nut. Then close the cover on the

package itself will also have a notch or cut-out at the top

empty pipe and drill two pilot holes 180° apart in the

end of the IC. When placing the IC into its respective

sleeve for self-tapping screws to clamp the cap in

socket make sure you align pin one (1) of the IC with pin

position after the sensor head is assembled.

one (1) of the socket. The integrated circuits must be

inserted into the socket properly aligned or the circuit will

Cut about a 6′′ length of RG-174/U coaxial cable,

not work and may damage the components. Go ahead and

strip both ends and solder the inner conductor of one

place U1 into its socket on the sensor head PC board.

end to the jack terminal and its shield to the jack lug.

Solder the inner conductor and shield of the other end to

the sensor circuit board.

Attach the coil to the sensor circuit board with about

Sensor coil assembly

a 6′′ length of RG-174/U coaxial cable as shown.

Connect the inner conductor to one terminal and the

The sensor coil at L1 detects changes in the local

shield to the other and solder both in position. The

magnetic field. You will need to wind approximately

prototype includes a twin “C” cell holder that, with

50,000 turns of 28 AWG magnet wire over a soft iron

cells in position, has a maximum width dimension of

219

less than 2′′ permitting it to slide easily into the sensor

PVC end cap

head pipe section.

Cut three lengths of hook-up wire to extend the

lengths of the positive, negative and ground leads of the

battery pack. Solder one end of those wires to the

holder leads and the other ends to the sensor circuit

board.

Bond the upper cap to the PVC pipe section with

PVC cement. Then position U1 in its socket,

Plastic

making certain that pin 1 is located correctly. Finally,

foam

insert the “C” cells in the holder. Wrap a layer of

polyurethane foam around coil L1 to center it within

Coil

the pipe section and insert both in the pipe section with

assembly

the cover at the end. Then assemble the completed

circuit board and battery pack to make sure that all of

these parts will fit in the pipe section. Set the

assembly aside until you are ready to perform the

PVC pipe

checkout steps.

Sensor

circuit

board

Control/display unit

(slide fit)

The control/display prototype circuit board measured

Twin cell

27⁄8′′ × 5′′ to fit inside the instrument case selected. The

holder

schematic for the control/display board is shown in

Figure 20-4. The dimensions of the circuit boards can

be modified for packaging in the instrument and sensor

head cases of your choice. Place the control/display

circuit board in front of you, along with all its

Two

respective components, and we will begin constructing

C cells

the control/display board.

Aurora Monitor Project

First we will begin by placing the resistors on the

Pvc

end cap

PC board; locate R6, an 18k ohm resistor, and R7 a

12k ohm resistor, and place them on the board and

solder them in place in their respective locations on the

Threaded

board. Next locate and install resistors R8, R9, R12, and

insert

R20; these are all 10k ohm resistors, solder them in

place and cut the excess component leads with your

end-cutter. Locate and install the remaining resistors,

Jack

solder them in place and trim the excess component

leads afterward.

Plug

Next, you can locate the capacitors C4, a .005 µF disk

Coaxial cable

capacitor, and it may be marked (502). Install C4 on the

to control unit

PC board and solder it in place, remember to cut the

Figure 20-6

Sensor

excess lead lengths. Now, locate capacitors C5, C7, C9

Chapter Twenty:

and C10; these are all .1 µF capacitors and may be

220

Chapter Twenty:

marked (104). Install these capacitors and solder them

The control/display assembly is housed in a standard

in place and then trim the extra leads. Now, locate C8, a

7′′ × 5′′ × 3′′ aluminum electronics instrument case with

4.7 µF electrolytic capacitor. Capacitor C8 has polarity,

a removable cover. Drill the holes in the front panel of

so it must be installed with respect to these marking.

the case for power ON switch S1, FILTER IN switch

Look at the schematic, and you will see that the plus (+)

S2, RANGE switch S3 and (if used) optional recorder

side of C8 is connected to the junction of resistor R23

switch S4. Also drill the holes for SENSITIVITY,

and diode D3. Install C8, and then solder it place, trim

ALARM ADJUST, and RATE potentiometers (R18,

the excess leads as necessary. Go ahead and install the

R19, and R11 respectively). Cut out the hole for

remaining capacitors and solder them in place on the

mounting meter M1. Note: If you want to use the

PC board.

monitor strictly as a security monitoring system the

The control/display section of the Aurora Monitor

meter can be omitted.

employs two silicon diodes, and they must be installed

Drill the holes in the back panel for jacks J2 and J3,

with respect to their polarity. The colored band denotes

and PULSE SHAPE potentiometer R17. Drill a series of

the cathode end of the diode. The cathode end of D3 is

holes in a circular pattern for the speaker SPKR1. Drill

fed to R23, while the cathode end of D4 is sent to C12

holes in the bottom of the case for mounting the

Aurora Monitor Project

and M1.

control/display circuit board and two quad “C” cell

Transistors are generally three-lead devices, with a

holders. Remember the circuit uses both a plus

Base lead, a Collector lead, and an Emitter lead. The

(+) 6 volt supply and a minus (−) 6 volt supply. We

Base lead is depicted as a straight vertical line with two

chose to power the circuit from batteries, but you could

arrows pointing to it. The Emitter lead will have a small

use a dual 6 volt power supply to power the control/

arrow pointing towards or away from it. When the arrow

display unit.

points toward the Base lead the transistor is a PNP type.

Assemble the panel-mounted switches, jacks,

If the arrow is pointing away from the Base lead then

potentiometers, meter and speaker to the front and back

the transistor is an NPN type. Transistor Q1 is a

panels of the case as shown in Figure 20-2. (You might

PNP type, while Q2 and Q3 are NPN types. Identify

prefer to bond the face of the speaker to the inside of the

the transistor leads and install them in their

back panel with RTV adhesive rather than bolts and nuts.)

respective locations on the PC board, trim the leads as

necessary.

Determine the length of speaker wires needed to

permit assembly of the circuit board in the instrument

The control/display portion of the Aurora Monitor

case, cut the wires to length and solder them to the

utilizes three integrated circuits. Integrated circuits are

board. Cut and solder all leads from panel-mounted

highly recommended in the event of a circuit failure at a

components to the circuit board, allowing sufficient

later date. Be sure to install the ICs correctly: pin one

lengths to permit unimpeded circuit board assembly, yet

(1) of U2 is connected to R7, while pin one (1) of U3 is

not allowing too much slack.

not used, pin two (2) is jointed with R9 and R8 and

R12. Integrated circuit U4 has pin one (1) connected to

Cut about a 6′′ length of RG-174/U coaxial cable to

the junction of R13 and R14. Failure to install the

connect INPUT jack J2 and the FILTER IN Switch S2

integrated circuits correctly may result in damage to the

and two other lengths about 6′′ long to connect S2 to

IC or to other components as well.

the FILTER-IN and FILTER-OUT pads on the

Finally you will need to connect the small audio

control/display board. Strip all cable ends and solder

transformer to the circuit. The higher impedance (1K)

and trim all connections.

end of the transformer is connected to the junction of

Assemble the control/display board to the base of the

Q1 and R22, and the other 1k lead is connected to the

case with screws and 1⁄2′′ insulating standoffs, lock

collector of Q3. The secondary or 8 ohm winding of T1

washers and nuts. Bolt the two quad AA cell holders to

is sent to the small 8 ohm speaker. The transformer can

the base of the case. Position the ICs in their sockets on

be mounted on the circuit board or on the bottom of the

the control-display board, making sure that all pin 1’s

chassis box. The 100 uA panel meter is wired between

are in their correct positions. Insert the eight AA cells in

the Emitter of Q3 and ground.

the spring-loaded holders, observing the correct polarity.

221

Cut a length of RG-174/U coaxial cable to the length

Then turn it back slightly so that no sound is heard to

that will suit your installation. Strip the wire ends and

obtain the maximum sensitivity setting. Next, turn

attach phono plugs PL1 and PL2 to cable ends and

potentiometer R19 full clockwise. There should be no

solder or crimp them in position.

sound from the speaker.

Before applying power to the Aurora Monitor, you

Position a small magnet or piece of metal next to coil

may want to inspect the two circuit boards for “cold”

L1 in the sensor head and the unit should now be

solder joints and “short” circuits. Look carefully at the

activated: the speaker should emit sound, and the meter

foil side of the sensor head unit and examine the solder

should read full scale. If everything checks out, you can

joints. The solder joints should all look clean, bright and

now start observing magnetic field disturbances or

shiny. If any of the solder joints look dark, dull, or

anomalies.

“blobby” then remove the solder from the joint and

In a quiet magnetic environment it might be

re-solder the connection. Next examine the

necessary to adjust potentiometer R4 in the sensor head

control/display board for “cold” solder joints. Now, we

to the threshold of the meter movement. This fine

will inspect the two boards for possible “short” circuits.

adjustment eliminates any small dead zones in

“Short” circuits are usually caused by “stray”

sensitivity. Test the instrument’s ability to detect the

component leads which get stuck to the board from the

Earth’s magnetic field by rotating the sensing head with

sticky residue left from rosin core solder or from small

short, quick, snapping motions in a counter-clockwise

solder balls which may “short” across the circuit traces.

direction. The meter movement should jump off scale.

Examine both circuit boards for “stray” leads and solder

As rotation is continued, a direction will be found

balls and remove them if you see any. Now, you are

where the meter will have its lowest response. This

ready to apply power to the circuits in order to “test”

nulling point is the north-south direction. Any objects

the circuits.

containing permanent magnets such as speakers or

meters that are brought into close proximity to the

Aurora Monitor’s sensing head coil L1 will affect the

Test and checkout

accuracy of the instrument’s readings.

In the event that the Aurora Monitor does not work

Test the sensing circuit first. Connect a general purpose

upon power-up, you will need to disconnect the power

oscilloscope or multi-meter to the output of U1.

supply and sensor head unit and inspect the circuit

Position a permanent magnet near coil L1 and the

board for possible errors which might have occurred

oscilloscope display should show a pronounced pulse.

while building the Aurora Monitor. The most common

If a multi-meter is used, its readout should jump.

cause for error when constructing the circuit is the

Aurora Monitor Project

incorrect installation of the electrolytic capacitors, the

Next, move L1 away from the magnet and the

diodes and semiconductors such as transistors and

reading on the multi-meter should fall to zero. If the

integrated circuits. You may have installed one of these

reading does not go to zero, adjust trimmer

components backwards, so you will need to carefully

potentiometer R4 in the sensor circuit. When the

inspect the circuit board. A second pair of eyes could be

sensing head is adjusted and working correctly, close

very helpful in locating potential errors of this sort.

the lower cap and fasten it with two non-magnetic

Have a knowledgeable electronic enthusiast help you

stainless steel self-tapping screws to complete the

inspect the circuit for errors. Another cause for error is

assembly. Connect one end of the plug-terminated

mis-locating resistors. You may have placed the wrong

coaxial cable to the sensor head jack 1 and the other end

value of resistor in a particular location, this would

to the control/ display unit jack J2.

cause the circuit to malfunction. After carefully

Turn on the power toggle switch of the

inspecting the Aurora Monitor circuit boards, you may

control/display unit and turn SENSITIVITY

quickly find your error and correct it. Once the error has

potentiometer R18 full clockwise. The meter should

been located, you reconnect the sensor head unit, and

remain at zero. Rotate ALARM ADJUST potentiometer

then re-apply power and then you can test the Aurora

Chapter Twenty: R19 clockwise until the alarm just begins to sound.

Monitor once again.

222

Chapter Twenty:

The Aurora Monitor can be connected to a chart

If you want a permanent installation, mount the

recorder or it can pass signals to a personal computer with

sensing head assembly so that it is directed away from

an analog-to-digital converter board. The recorder or PC

any large metal obstructions, oriented on a north-south

can collect data for the study of magnetic fields, magnetic

axis, and pointed slightly upwards. It’s a good idea to

storms, and sunspot activity over long periods of time for

fasten it to a heavy wooden post to prevent wind-

further analysis. A set of high-impedance (greater than

induced vibrations.

1 kilohm) headphones can be plugged into jack J3 if you

wish to “hear” the changes in magnetic fields.

Aurora Monitor Project

223

Chapter 21

Ultra-Low Frequency

(ULF) Receiver

Parts list

U3,U4

TL074 op-amp IC

U5

INA114 Differential

ULF Receiver

amplifier IC

R1,R4

50k ohm trim

J1,J2,J3

3-terminal

potentiometer

screw terminal strips

R2

50k ohm - 20 turn pot

S1

SPST power switch

R3

100k ohm trim pot

F1

1-amp fast-blow fuse

R5,R6,R10

10 k ohm, 1/ w,

4

Misc

PC board, chassis,

5% resistor

wire, hardware, power

R7,R8,R9,R12,R21

33 k

cord, etc.

ohm, 1/ w, 5% resistor

4

ULF Receiver Power

R11,R16

1 k ohm, 1/ w,

Supply

4

5% resistor

C1,C4

2200 µF, 35 volt

R13,R20

22 k ohm, 1/ w,

electrolytic

4

5% resistor

capacitor

R14,R15,R18,R19

47 k

C2,C5

.33 µF, 35 volt

ohm, 1/ w, 5% resistor

ceramic capacitor

4

R17

50 k ohm pot

C3,C6

.1 µF, 35 volt

ceramic capacitor

R22

2.2k ohm, 1/ w,

4

5% resistor

U1

LM7805 - fixed

positive voltage

C1,C2,C3,C4,C5,C6

.1 µF,

regulator

35 volt disk capacitor

U2

LM7905 - fixed

C11,C12,C13,C14

.1 µF,

negative voltage

35 volt disk capacitor

regulator

C8,C9

1 µF tantalum,

D1,D2,D3,D4

50 volt,

35 volt electrolytic

2 amp silicon

capacitor

diode

C10

.01 µF, 35 volt

T1

110v-12 v center

disk capacitor

tapped transformer -

C7

.05 µF, 35 volt disk

2amp

capacitor

Misc

circuit board,

D1

Zener diode

wire, terminals, plug,

U1,U2

LTC1063 IC

fuse, etc.

224

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Twenty-one: Ultra-Low Frequency (ULF)

If you are interested in monitoring the ultra-low

frequency spectrum from .001 Hz to 30 Hz, the ULF

receiver will allow you to do some serious research into

earthquake monitor and Earth field studies. This project

is intended for curious individuals who want to

participate in the research and experimentation of the

study of extremely low frequency signals which

Figure 21-1

ULF receiver

travel through the interior of our Earth. This project will

allow you to construct a ULF receive station to be

used to collect data for later analysis and compare it

At any time it is possible to take any period of data

with others who belong to the ELFRAD group

previously recorded, generate a file and display the data

and those researchers involved with the Public

for analysis. You are also able to post filter the data,

Seismic Network.

with band pass, notch, low pass, and high pass

The ELFRAD low frequency group coordinates a

capability.

research group which studies the low frequency

The Ultra Low Frequency Receiver project is shown

spectrum and reports to one another the research that

in Figure 21-1. This ULF receiver circuit was designed

individual members do and makes available the

as an all purpose ULF and ELF receiver with a

information for comparison through their central

frequency range from DC to 30 hertz. The signals from

website. In order to achieve their goal, it is necessary to

both leads of the non-polarized antenna array are

have most of the equipment and construction parameters

connected to J3, as seen in the schematic diagram in

standardized as much as possible, so the ELFRAD

Figure 21-2 and 21-3, a two sheet diagram The antenna

Group will furnish software and support.

input signal travels to pins 2 and 3 on U5, which is a

A complete standardized ELFRAD monitoring

high impedance differential instrumentation amplifier.

station consists of a ULF receiver, an antenna array, and

This chip’s gain is controlled by a single variable

interface card and a personal computer, and in this

resistor at R3.

project we will discuss how to put a receive station

The combined signals then travel from pin 6 of U5 on

together in your home workshop.

to U3:A which is a buffer amplifier, followed by a 2

The Ultra-Low Frequency Receiver allows the

pole low pass filter at U3:B and U3:C and signal

desired ultra-low frequency signals to be recovered from

amplifier at U3:D. From pin 14 on U3, the partially

the Earth. The signals are directed to a conditioning

filtered signal travels on to integrated circuit U2 and U1

circuit which not only protects the receiver equipment

which are 5 pole Butterworth low pass filters in cascade.

from transients caused by lightning and other sources

The LTC1063 ICs at U1 and U2 are clock controlled and

but attenuates the ambient 60 or 50 Hz frequency

the frequency is set at 3000 hertz by R9. This configures

caused by commercial power, with the receiver’s

the two LTC1063 chips to have a cut-off frequency of

power-line notch line filter. The signals then pass

about 30 hertz. The clock ratio is 1/100.

through a circuit which removes any ground loop

The integrated circuit at U4 consists of a X5 gain

problems which may occur at your computer interface.

amplifier at U4:D, a buffer at U4:C and another 2 pole

The low frequencies of interest are then passed through

analog low pass filter at U4:B and U4:A. Trim

a series of filters to remove most of the noise and

potentiometer R17 is the final gain control for the

Receiver

unwanted signals above 25 Hz. This desired band of

desired output voltage at U4:A. IC section U4B is a

signals is then coupled to the analog-to-digital interface

2 pole low pass filter which removes any residual

in your personal computer to be recorded on the hard

clocking pulses from the signal which may have

drive. The interface used in the prototype accepted up to

been caused by U1 and U2. The amplified output

eight channels of data samples and was able to collect

signal at J1 can be routed to your analog-to-digital

200 samples per second, record them and then display

converter card in your PC. Power is supplied to the

them on the computer screen in either real time or

ULF receiver at the terminals of J2. The output from the

compressed time format.

ULF receiver can be routed to an analog-to-digital

225

Antenna

input

R6

J3

A

D2

B

R3

U5

R7

Receiver

Ground

P1

P8

C4

P2

P7

P3

P6

P4

P5

C3

R6

C7

R2

R16

R1

R5

R11

R12

R13

U3:A

U3:C

4 U3:B

+

–

6

13

4

–

7

9

–

14

R14

R15

8

–

+

2

5 +

10

11

+

+

11

12

11

3

11

C6

U3:D

–

C11

C12

C5

P1 P2

P3

P4

Figure 21-2

ULF receiver schematic – Part I

converter card in a personal computer for recording and

A 110 to 12 volt center tapped transformer is fed

displaying the receiver’s output in real time or for later

directly to a four diode bridge rectifier. The resultant

viewing.

DC signal is then coupled to two 2200 µF filter

The ULF receiver circuit is powered from a dual

capacitors at C1 and C4. The plus voltage output from

plus/minus 5 volt power supply, shown in the schematic

C1 is then fed to the input of an LM7805. The output of

at Figure 21-4. The power supply will furnish plus and

U1 is then sent to a .1 µF capacitor at the positive output

Chapter Twenty-one: Ultra-Low Frequency (ULF) minus 5 volts DC for all of the op-amps in the receiver.

terminals. The minus voltage output from C4 is sent to a

226

Chapter Twenty-one: Ultra-Low Frequency (ULF)

J1

J2

J3

J4

C9

U2

U1

P1

P8

P1

P8

P2

P7

P2

P7

P3

P6

P3

P6

P4

P5

P4

P5

J2

–5 V

R9

C10

C8

+5 V

Power

C1

R17

R4

R21

R20

U4:A

4

4

–

8

–

14

9

4

2

13

U4:B

+

6

–

1

+

10

–

7

12

11

11

R18

R19

U4:D U4:C

5

+

+

3

11

11

+

C2

C13

C14

R22

J1

–

Output

signal

Figure 21-3

ULF receiver schematic – Part II

negative voltage regulator at U2, an LM7905. The

locate a clean well lit and well ventilated work area.

output from U2 is then sent to capacitor C6, at the

A large table or workbench would be a suitable work

minus voltage output terminals.

surface for your project. Next you will want to locate a

Let’s get started building the ULF receiver! Before

small 27 to 33 watt pencil-tipped soldering iron, as well

we begin building the ULF receiver, you will need to

as a roll of #22 ga. 60/40 tin/lead solder and a small jar

D1 – D4

In

Out

U1

+5 V DC

C3

110 V AC

T1

C1

C2

+

+

Ground

F1

Receiver

S1

In

Out

U2

-5 V DC

C4

C5

C6

+

+

Figure 21-4

ULF receiver power supply

227

of “Tip Tinner,” a soldering iron tip cleaner/dresser from

digit one (1), the second band is black which represents

your local Radio Shack store. You will also want to

a digit five (0) and the third band is orange, which

secure a few hand tools for the project, such as a pair of

represents a multiplier of zero (000), so the resistor

small end-cutters, a pair of tweezers and a pair of

value is 10,000 or 10k ohms with a tolerance value of

needle-nose pliers. Locate a small Phillips and a small

5%. Identify the remaining resistors for the project and

flat-blade screwdriver, as well as a magnifying glass to

we can begin “populating” the PC board. Place a few

round out your tool list. Grab the schematic, parts

resistors on the board at one time, so as not to confuse

layout diagram as well as the resistor and capacitor

the process. Make sure that you place the correct resistor

Receiver

identifier charts and we will begin our project. Place all

into the correct PC location before soldering it in place.

the project components on the table in front of you.

Once you solder a few resistors in place on the PC

The ultra-low frequency receiver is an RF or radio

board, you can use your end-cutter to trim the excess

frequency project and it is best constructed on a printed

component leads. Cut the excess leads flush to the edge

circuit board with large ground plane areas covering the

of the circuit board. Then place a few more resistors on

board for the best RF grounding techniques. Once you

the PC board and solder them on to the board.

have all the parts and PC board in front of you, heat up

Remember to trim the component leads as necessary.

the soldering iron and we’ll get started!

Next we will locate the capacitors for the ULF

First, find your resistor identifier chart in Table 21-1,

receiver. Capacitors are listed as electrolytic and

which will help you select the resistors from the

non-electrolytic types. The non-electrolytic types are

parts pile. Resistors used in this project are mostly small

generally smaller in value and size as compared with

1⁄4 watt carbon composition type resistors, which have

the electrolytic types. Non-electrolytic capacitors in fact

colored bands along the resistor body. The first color

can be so small that their actual value cannot be printed

band should be closest to one end of the resistor body.

on them, so a special chart was devised as shown in

This first color band represents the first digit of the

Table 21-2. The chart illustrates the three-digit codes

resistor value. For example, resistor R5, R6 and R10 has

which are often used to represent capacitors. For

four color bands, the first one is a brown band followed

example a .001 µF capacitor will have (102), while a

by a black band followed by an orange band. The fourth

.01 µF capacitor will have (103) marked on it to

band is gold. The first band is brown which denotes a

represent its true value. Use the chart to identify the

Table 21-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

Chapter Twenty-one: Ultra-Low Frequency (ULF)

No color

20%

228

Chapter Twenty-one: Ultra-Low Frequency (ULF)

small capacitors in the project. Non-electrolytic have no

end of the resistor body. The lead closest to the colored

polarity markings on them so they can be installed in

band is the cathode lead of the diode.

either direction on the PC board.

The main ULF schematic diagram is broken into two

Electrolytic capacitors are usually larger in size and

diagrams, since the schematic is rather large. You have

value and they will have a white or black band on the

most likely noted that along the bottom of diagram

side of the capacitor body or a plus (+) or minus (−)

(A), you will see designations of P1, P2, P3 and P4.

marking on the body of the capacitor near the leads.

These are not connectors as such but merely to help

These markings are polarity markings and that indicate

separate the two diagrams for illustration purposes. The

the direction in which the capacitor must be mounted on

receiver was constructed on a single printed circuit

the PC board. Failure to observe polarity when

board. In the original prototype, the antenna input

installing the capacitor may result in damage to the

shown at J3 was a screw terminal strip, but this could be

capacitor or to the circuit itself, so pay particular

changed to an SO-238 antenna jack mounted on the

attention to capacitor polarity when placing the

chassis enclosure. The power connection was made at a

capacitors on the board.

second screw terminal jack at J2, which had three

Let’s go ahead and place some of the non-electrolytic

terminal posts for plus/minus and ground connections.

capacitors on the PC board. Identify a few small

The output of the ULF receiver was connected to a third

capacitors at a time and place them on the PC board and

screw terminal jack at J3, this could be changed to an

solder them in place. Trim the component leads after.

RCA jack if desired.

Go ahead and install the remaining non-electrolytic

The ULF receiver contains a number of variable

capacitors after choosing your desired band.

resistors or potentiometers in the circuit. Potentiometer

Install the capacitors and solder them in place,

R1, R3 are PC board trimmer types, while R2, which is

remember to cut the extra leads flush to the edge of the

a 20 turn precision chassis mounted potentiometer, and

circuit board. Now, you can go ahead and install the

R4 is a conventional chassis mounted linear taper

electrolytic capacitors onto the circuit board. Go ahead

potentiometer.

and solder them in place and trim the leads as

The ULF receiver is now almost completed, so take a

necessary.

short well deserved break, and when we return we will

The ULF receiver utilizes five integrated circuits and

inspect the circuit board for any possible “cold” solder

two regulators integrated circuits. Locate the

joints and “short” circuits before we apply power to the

semiconductor pin-out diagram illustrated in

circuit. Pick up the PC board with the foil side of the

Figure 21-5, which will help you install the ICs. When

board facing upwards toward you. Examine the foil side

constructing the project it is best to use IC sockets as an

of the board carefully, take a look at the solder joints.

insurance against a possible circuit failure down-the-

All of the solder joints should look clean, bright, shiny

road; it’s much easier to unplug an IC rather than trying

and smooth; if any of the solder joints look dark, dull or

to un-solder an IC from the PC board. IC sockets will

“blobby” then you should remove the solder from the

have a notch or cut-out at one end of the plastic socket.

joint with a solder-sucker and then completely re-solder

Pin one (1) of the IC socket will be just to the left of the

the joint all over again so that the solder joints all look

notch or cut-out. Note, pin 1 U1 connects to pin 7 of

good. Next we will examine the PC board for any

U2, while pin 1 of U2 connects to the output of U3:D.

possible “short” circuits, which may be caused from

Now take a look at U3, pin 1 of U3 is connected to

“stray” component leads which were cut from the

Receiver

R14, while pin 1 of U4 is fed to the output through R22.

board. Another possible cause of short circuits are

Finally, pin 1 of U5 is connected to potentiometer R3.

solder blobs which may have stuck to the foil side of

Now place each of the integrated circuits into their

the board. Rosin core solder often leaves a sticky

respective sockets.

residue which can cause leads and solder blobs to stick

A protection Zener diode is placed across the antenna

to the board and possibly “bridge” across circuit traces.

input pins between resistors R6 and R7. Note that all

Next we will need to build the dual voltage power

diodes have polarity, including Zener diodes. Diodes

supply circuit board. The power supply was built on the

will have either a black or white colored band at one

circuit board as well. The transformer was mounted off

229

Table 21-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, Receiver followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Twenty-one: Ultra-Low Frequency (ULF) 820pF

Ceramic

821

2

Mylar

205

230

Chapter Twenty-one: Ultra-Low Frequency (ULF)

1

8

1

8

1

14

1

8

1

8

1

14

2

7

2

7

2

13

3

6

3

6

4

5

4

5

3

12

4

11

LTC1063

INA114

5

10

6

9

7

8

TL074

Ground A B

To J3

Figure 21-5

Semiconductor pin-outs

Figure 21-6

ULF receiver antenna circuit

the circuit board and on the bottom of the chassis. The

diode bridge was placed on the circuit board, paying

you are going to need a little space. As long as you have

careful attention to the polarity of the diodes. You could

a strip of property at least one 100 or more feet in

elect to individual diodes or one of those four diode

length you will be able to detect the signals. There are

bridge rectifiers all in one package. If you choose the

several items of interest in determining your location.

second option again you must observe the polarity of

You will be building two arrays widely separated from

the plastic package. The AC input section will be

each other. The further apart the better. Also if you have

marked with two wavy lines, the AC side has no

a choice, a damp location is better than dry rocky soil.

polarity. The DC side of the bridge will have a plus (+)

The first step in constructing your antenna/detector is

and a minus (−) marking. When installing the six

to determine the magnetic orientation. Take an ordinary

capacitors be sure to observe polarity since four of them

pocket compass and locate magnetic North. The line of

are electrolytic types. Note that there are two power

sight between the two points should be aligned with

supplies and the polarity placement orientation is

North-South. The next step is to obtain some copper

different for the two power supply sections. The

clad ground rods at least eight feet in length, put on

LM7805 is the plus voltage regulator, while the

some gloves and start driving one into the ground. We

LM7905 regulator is the minus voltage regulator; don’t

found that a standard metal fence post driver purchased

mix them up, and take your time to install them at the

from the local farm store was ideal for the job. It helps

correct locations to avoid damage to the circuit. A fuse

also to take a pair of post diggers and dig out a hole

was placed in series with the power switch to the

about 18′′ deep. Then drive the rod down into the

transformer input leads. A power line-cord with a

ground below the surface of the hole leaving enough

110 volt plug was used to supply power to the

room to make a connection.

transformer. Once the power supply circuit has been

Next measure out a distance as far as possible, at

completed, you can carefully inspect the circuit board

least 30 meters (98 ft) in a North or South direction and

for any “cold” solder joints and “short” circuits before

repeat the procedure above, driving a copper clad eight

applying power for the first time.

foot ground rod into the soil. Then connect the two

The Ultra-Low Frequency Receiver requires an

widely spaced rods together using a length of wire.

antenna “site” for proper operation. This is not the usual

Obtain an ohmmeter, and open the wire conductor and

Receiver

conventional type of antenna that you encounter with

measure the resistance. Make a note of the reading,

most receivers, since this is a special type of receiver

then reverse the ohmmeter leads and measure again.

project. The array is designed to be built completely

Then take this reading, average it with the other reading

underground. Space for construction is necessary and

and you will have a close indication of the DC

may be anywhere from 100 to 1000 linear feet, see

resistance between the two probes (ground rods). Very

Figure 21-6.

likely, unless you have excellent soil conductivity in

Due to the fact that we will be dealing with extremely

your area, the reading will be several thousand ohms.

long wavelengths on the order of miles rather than feet,

The point is to lower this reading as much as possible.

231

The lower the better. A workable resistance is 50 to 500

and make sure the ground connection is at least 20 feet

ohms but the ideal resistance would be around 5 to 10

from power ground.

ohms. In most cases, however, this would be

With the ULF receiver, power supply and antenna

unobtainable unless you used many ground rods or

constructed and ready to go, we just have one more

copper strapping at each end.

detail left to complete our ELFRAD ULF monitoring

Keep adding rods at each probe site, spaced 20 feet

station. The most expensive components will be the

apart from one another connected together with #6

computer and analog-to-digital interface device. A PC

Receiver copper bare wire, until the resistance gets down to type of computer is recommended using Windows 98,

between 25 and 500 ohms. Keep in mind two items.

NT, Win2000, or XP software will work nicely. Since

The further apart the probe sites, the lower the

most of everyone owns a computer or laptop these days,

resistance, and the more rods driven into the ground, the

the only thing left to be purchased is the A/D interface.

lower the resistance. We have found that on the average,

The software for the A/D converter is available from the

five grounds at each end of the site are sufficient to

supplier of the A/D interface listed below. You will need

obtain this reading.

at least a two channel A/D board, since it is

Another option rather than using ground rods, in

recommended that you also record a short wave radio

rocky or extremely hard soil, you may use a ditch

tuned to WWV, which keeps computer synched to within

trencher and bury #6 or #4 copper wire at least 24

plus or minus 2 milliseconds. Also if desired, a GPS type

inches deep. The copper wire should be placed in an

of time standard is available. The A/D converter is

“X” fashion with a length of at least 25 feet. The lead

available at http://seismicnet.com/ serialatod.html.

cable will then be connected to the center point of

For more information on Earthquake monitoring you

the “X.”

may finds these sites helpful.

Now obtain a length of CATV lead in wire such as

ELFRAD Research Group

RG-11 or RG-59, from your local electronic parts store.

The low frequency radio research group, which provides

A good source to try is the local Cable TV company.

support to interested researchers.

Sometimes they have lengths of scrap lying around their

Helps researchers in correlating and comparing data.

warehouse and will be happy to get rid of it. Connect

the center conductor only (not the outside shield) to

http://www.elfrad.com/

each antenna array using copper clamps. Take each

Public Seismic Network

piece of co-ax to the location of your receiver. Then

A seismic research group dedicated to earthquake

install a suitable connector to the two ends. These two

monitoring.

cables will be the input leads to the receiver. The shield

Helps researchers in correlating and comparing data.

should be connected to earth ground using a single

copper clad ground rod. Do not use the power ground

http://psn.quake.net/

Chapter Twenty-one: Ultra-Low Frequency (ULF)

232

Chapter 22

Jupiter Radio Telescope Receiver

C3

56 pF, 35v disk

Parts list

ceramic

C4

22 pF, 35v disk

Jupiter Radio Telescope

ceramic

R1

68 ohm

C5,C8,C11,C14

.01 mF,

R2

294 ohm

35v dipped ceramic

R3

17.4 ohm

C6

4-40 pF, variable

capacitor

R4

294 ohm

C7

not used

R5

100 ohm

C9,C12,C13

47 pF, 35v

R6

2.2k ohm

disk ceramic

R7

10k ohm linear

C10

270 pF, 35v disk

potentiometer

ceramic

R8

2.2k ohm

C15

10 pF, disk

R9, R19

100k ohm

ceramic

R10

220 ohm

C16,C24,C25

10 mF, 35

R11

1.5k ohm

vdc, electrolytic

R12,R20,R21,R27

1k ohm

C17,C18,C21,C23,C26C29

R13,R18

27k ohm

.1 mF, 35v dipped

ceramic

R14

100k ohm

C19

1 mF, 35v metal

R15

10k ohm

polyester

potentiometer/

switch

C20,C22

0.068 mF, 35v

5% metal film

R16

10k ohm

C27

10 mF, 35 vdc,

R17

1.5k ohm

tantalum, stripe,

R22,R23

2 ohm

C28

220 pF, 35v disk

R24

1 ohm

ceramic

R25

220 ohm

C30,C31,C33

10 mF, 35

R26

47 ohm

vdc, electrolytic

R28,R29,R30,R31,R32

C32

330 mF, 35 vdc,

10 ohm

electrolytic

C1

39 pF, 35v disk

C34,C35,C36

0.1 mF, 35v

ceramic

dipped ceramic

C2

4-40 pF, variable

C37

10 pF, 35v disk

capacitor

ceramic

233

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

C38

10 mF, 35 vdc,

J2

F female chassis

electrolytic

connector

C39

100 mF, 35 vdc,

J3,J4

3.5 mm stereo

electrolytic

jack, open ckt

C40,C41,C42,C43

0.1 mF,

Misc

PC Board,

35v dipped

enclosure, knobs,

ceramic

solder lugs, wire

C44

10 mF, 35 vdc,

Jupiter is the fifth planet from the Sun and is the largest

electrolytic

one in the solar system. If Jupiter were hollow, more

D1

1N4001

than one thousand Earths could fit inside. It also

contains more matter than all of the other planets

D2,D3

1N914

combined. It has a mass of 1.9 × 1027 kg and is

LED

Red LED

142,800 kilometers (88,736 miles) across the equator.

VD1

MV209, varactor

Jupiter possesses 28 known satellites, four of which—

diode

Callisto, Europa, Ganymede and Io—were observed by

Galileo as long ago as 1610. Another 12 satellites have

ZD1

1N753, 6.2v, Zener

been recently discovered and given provisional

diode, 400 mw

designators until they are officially confirmed and

ZD2

1N5231, 5.1v, Zener

named. There is a ring system, but it is very faint

diode, 500mw

and is totally invisible from the Earth. (The rings

L1

0.47 mH, (gold,

were discovered in 1979 by Voyager 1.) The atmosphere

yellow, violet,

is very deep, perhaps comprising the whole

silver)

planet, and is somewhat like the Sun. It is composed

L2

1 mH, (brown, gold,

mainly of hydrogen and helium, with small amounts

black, silver)

of methane, ammonia, water vapor and other

compounds.

L3

3.9 mH, (orange,

gold, white, gold)

Colorful latitudinal bands, atmospheric clouds and

storms illustrate Jupiter’s dynamic weather systems, see

L4,L5

1.5 mH,

Figure 22-1. The cloud patterns change within hours or

adjustable inductor

days. The Great Red Spot is a complex storm moving in

L6,L7

82 mH, fixed

a counter-clockwise direction. At the outer edge,

inductor

material appears to rotate in four to six days; near the

Q1

J-310, junction

center, motions are small and nearly random in

field effect (JFET)

direction. An array of other smaller storms and eddies

Q2

2N-3904, bipolar,

can be found throughout the banded clouds.

NPN

Auroral emissions, similar to Earth’s northern lights,

Q3

2N-3906, bipolar,

were observed in the polar regions of Jupiter. The

PNP

auroral emissions appear to be related to material from

Io that spirals along magnetic field lines to fall into

U1

SA602AN,

Jupiter’s atmosphere. Cloud-top lightning bolts, similar

mixer/oscillator IC

to super-bolts in Earth’s high atmosphere, were also

U2,U3

LM387 or NTE824 -

observed.

audio pre-amplifier IC

The Jupiter Radio Telescope is a special shortwave

OSC1

20 MHz crystal

receiver which will pick up radio signals from the

oscillator module

planet Jupiter and also from the Sun, and it is a very

Chapter Twenty-two: Jupiter Radio Telescope Receiver

J1

Power jack, 2.1 mm

exciting project, see Figure 22-2. This project will allow

234

Chapter Twenty-two: Jupiter Radio Telescope Receiver

must be amplified by the receiver and converted to

audio signals of sufficient strength to drive headphones

or a loudspeaker. The receiver also serves as a narrow

filter, tuned to a specific frequency to hear Jupiter while

at the same time blocking out strong Earth based radio

stations on other frequencies. The receiver and its

accompanying antenna are designed to operate over a

narrow range of shortwave frequencies centered on 20.1

MHz (megahertz). This frequency range is optimum for

hearing Jupiter signals.

The block diagram shown in Figure 22-3 illustrates

the various components of the Jupiter Radio Telescope.

First shown the antenna intercepts weak electromagnetic

waves which have traveled some 500 million miles from

Jupiter to the Earth. When these electromagnetic waves

strike the wire antenna, a tiny RF voltage is developed

at the antenna terminals. Signals from the antenna are

delivered to the antenna terminals of the receiver by a

Figure 22-1

Jupiter

coaxial transmission line. Next the signals are delivered

to the RF Bandpass Filter and Preamplifier, they are

filtered to reject strong out-of-band interference and are

you to do amateur research into radio astronomy in your

then amplified using a junction field effect transistor

own back yard.

(JFET). This transistor and its associated circuitry

Radio signals from Jupiter are very weak—they produce

provide additional filtering and amplify incoming

less than a millionth of a volt at the antenna terminals of

signals by a factor of 10. The receiver input circuit is

the receiver. These weak radio frequency (RF) signals

designed to efficiently transfer power from the antenna

Figure 22-2

Radio Jupiter receiver project

235

Antenna

RF

20.00 MHz

bandpass

test

filter

oscillator

RF

preamp

J310

Lo/mixer

WE602

Tuning

20.1 MHz

5-pole

+/– 150 kHz

lowpass

filter

Audio

preamp

WIE824

Volume

Audio

amp

Audio out

Audio out

1

2

External

amplified

speaker

Figure 22-3

Jupiter radio block diagram

to the receiver while developing a minimum of noise

vicinity of 20.1 MHz. The exact frequency is set by the

within the receiver itself.

front panel tuning control. Both the amplified RF signal

Next the signals move to the local oscillator (LO) and

from the antenna and the LO frequency are fed into

mixer to perform the important task of converting the

the mixer. The mixer develops a new signal which is the

desired radio frequency signals down to the range of

arithmetic difference between the LO and the incoming

audio frequencies. The local oscillator generates a

signal frequency. Suppose the desired signal is at

Chapter Twenty-two: Jupiter Radio Telescope Receiver sinusoidal voltage wave form at a frequency in the 20.101 MHz and the LO is tuned to 20.100 MHz.

236

Chapter Twenty-two: Jupiter Radio Telescope Receiver

The difference in frequency is therefore 20.101–20.100

is amplified. The output of the J-310 goes through

=.001 MHz, which is the audio frequency of 1 kilohertz.

another resonant filter (L3, C6) before being applied to

If a signal were at 20.110 MHz, it would be converted to

the resonant input circuit (L4, C9, C10) of the SA602

an audio frequency of 10 kHz. Since the RF signal is

integrated circuit (U1), which serves as the local

converted directly to audio, the radio is known as a

oscillator and mixer. The center frequency of the local

direct conversion receiver.

oscillator is set by inductor L5 and adjusted by the

To eliminate interfering stations at nearby

tuning control R7. The audio output from U1 passes

frequencies, a low pass filter is next used, which is like

through the lowpass audio filter (L6, L7, C20, C21, and

a window, a few kilohertz wide through which Jupiter

C22). The audio signal is next amplified by U2 (an

signals can enter. When listening for Jupiter or the Sun,

NTE824) before going to the volume control R15. The

the radio will be tuned to find a “clear channel.” Since

final audio amplifier stages comprise U3 (another

frequencies more than a few kilohertz away from the

NTE824), and the output transistors Q2 (2N-3904) and

center frequency may contain interfering signals, these

Q3 (2N-3906). After the receiver has been assembled,

higher frequencies must be eliminated. This is the

the variable capacitors C2 and C6 and variable

purpose of the low pass filter following the mixer. It

inductors L4 and L5 will be adjusted to tune the

passes low (audio) frequencies up to about 3.5 kHz and

receiver for operation at 20.1 MHz.

attenuates higher frequencies.

Finally the low pass filter feeds an audio amplifier

stage which takes the very weak audio signal from the

PC board assembly

mixer and amplifies it enough to drive headphones

directly, or to drive an external amplified speaker

assembly.

Before we begin building the circuit, take a few minutes

to locate a clean well lit work table or work bench. You

will want to locate a small 27 to 33 watt pencil-tipped

soldering iron, a roll of 60/40 tin/lead rosin core solder,

Circuit diagram

and a small jar of “Tip Tinner,” a soldering iron tip

cleaner/dresser. “Tip Tinner” is available at a local

We have already seen a block diagram of the Jupiter

Radio Shack store. You will also need some small hand

radio receiver which shows the radio as a group of

tools, such as a small flat-blade screwdriver, a Phillips

functional blocks connected together. While this type of

screwdriver, a pair of small needle-nose pliers, a

diagram does not show individual components like

pair of tweezers, a magnifying glass and pair of

resistors and capacitors, it is useful in understanding

end-cutters.

signal flow and the various functions performed within

the radio. The next level of detail is the schematic

Once you have gathered all the tools, locate all the

diagram. A schematic is used to represent the

circuit diagrams, such as the schematics, the parts

wiring connections between all of the components

layout diagram, the resistor and capacitor code charts,

which make up a circuit. The schematic diagram uses

etc. Place all the component parts along with all your

symbols for each of the different components

tools and diagrams in front of you, warm up your solder

rather than pictures of what the components actually

iron and we will start building the Radio Jupiter receiver

look like.

project.

A schematic diagram of the complete receiver is seen

First we will identify the resistors for the project.

in Figure 22-4. On this schematic, the part types are

Refer to the chart shown in Table 22-1, which will help

numbered sequentially. For example, inductors are

you to identify the resistor color codes. Resistors

denoted L1 through L7, and resistors are denoted R1

usually have three or four color bands on the body of

through R31. Signal flow as shown in the schematic is

the resistor which denotes the resistor value. The color

as follows. The signal from the antenna connector (J2)

bands begin at one end of the resistor body close

is coupled to a resonant circuit (bandpass filter L1, C2,

to the edge. The first color band on resistor R1 is blue,

C3) and then to the J-310 transistor (Q1), where it

this denotes the digit six (6). The second color band is

237

C h a p t e r T w e n t y - t w o : J u p i t e r R a d i o T e l e s c o p e R e c e i v e r 238

Power

D1

S1

J1

DC in

R27

+

+

C42

C43

R10

C44

C39

C40

C41

R5

+

ZD1

C8

C16

C25

D1

C17

+

A

L3

C7

C18

Antenna

C26

C1

C4

Q1

C9

1 8

R3

3

L6

L7

C23

J2

S

D

L4

4

U1

5

8

6

RF

6

C2

C6

C19

2 7

U2

5

input

L2

R2

R4

C10

R11

3

C3

L1

C13

C20

C21

C22

7

G

C11

C5

R1

C12

R14

R6

C14

A

R9

C15

+

R12

R13

C38

R7

VD1

+

+

L5

C24

C27

R8

TP1

OSC-1

C37

R25

8

14

7

+

Avoid

C31

c

Record

R21

Q2

C33

R28

R26

C36

ZD2

C35

gain

b

+

C29

J3

R29

R15

8

D2

R22

e

C32

6

+

U3

5

R16

C28

R23

3

R30

7

D3

e

J4

b

R31

R20

R24

c

R17

R19

Audio

R18

out

C34

+

C30

Figure 22-4

Radio Jupiter receiver schematic

Chapter Twenty-two: Jupiter Radio Telescope Receiver

Table 22-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

gray, which is the digit number eight (8) and the third

two major flavors, non-polarized and polarized types.

color band is the resistor’s multiplier value which is

First, we will talk about non-polarized capacitors.

black and this suggests a multiplier value of 1. So the

Usually non-polarized capacitors are smaller value types

resistor value for R1 is (6) times (8) times (1) or

which could take form as ceramic disks, mica, tantalum

68 ohms. The tolerance value of a resistor is noted in the

or polyester types. Often the capacitors are small in size

fourth color band. A fourth color band which is silver is

and frequently the capacitor values are printed as three-

a 10% tolerance resistor, while a gold fourth band

digit codes rather than their actual values, since this

denotes a 5% tolerance value. If there is no fourth color

code system takes less space to print. We have included

band then the resistor will have a 20% tolerance value.

a chart in Table 22-2, which lists the actual capacitor

Next, locate R2, R3 and R4, then check your parts

values and their respective codes. For example, a

layout diagram and the schematic to see where these

capacitor with a value of .001 µF will have a code

resistors are to be placed on the circuit board. Once you

designation of 102, a .01 µF capacitor will have 103 and

verify where the resistors are placed, you can install

a 0.1 µF capacitor will have a code of 104 marked on it.

these resistors on the circuit board and solder them in

The Radio Jupiter project has a number of non-

place on the board. Now locate your end-cutter and trim

polarized type capacitors which you will need to install.

the excess component leads. Cut the extra component

Take a look through the component pile and see if you

lead lengths flush to the edge of the circuit board. Now

can identify the small non-polar capacitors before

go ahead and identify another group of three or four

attempting to install them on the PC board.

resistors and place them on the circuit board. Once you

Polarized capacitors are called electrolytic capacitors,

are sure of their respective locations you can solder the

they are often larger in physical size. Electrolytic

next grouping of resistors onto the circuit board,

capacitors will always have some sort of polarity

remember to trim the excess component leads from the

marking on them. You will see either a black or white

board. Place all the remaining resistors on the circuit

band or a plus (+) or minus (−) marking somewhere on

board and solder them all in place, trim the extra leads

the capacitor body. It is very important that you install

as necessary.

these types of capacitors with respect to their polarity in

Now we will move on to installing the capacitors for

order for the circuit to work properly and to not be

the Radio Jupiter receiver project. Capacitors come in

damaged upon power-up. You will need to refer to the

239

Table 22-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

Chapter Twenty-two: Jupiter Radio Telescope Receiver 820pF

Ceramic

821

2

Mylar

205

240

Chapter Twenty-two: Jupiter Radio Telescope Receiver

schematic and parts layout diagrams when installing

semiconductors with respect to proper polarity marking

electrolytic capacitors to make sure that you have

on each of the components. Electrolytic capacitors have

installed them correctly. The plus (+) marking on the

either a plus or minus marking on them and must be

capacitor will point to the most positive portion of the

installed correctly by observing the polarity of the

circuit.

capacitor with respect to the PC board.

Let’s go ahead and identify the non-polarized

Next, we will install the semiconductors. Locate the

capacitors first. Check the capacitor code chart and

semiconductor pin-out diagram shown in Figure 22-5,

make sure that you can identify each of the non-

which will help you install the semiconductor devices

polarized capacitors. In groups of two or three

properly. There are a number of diodes in the Radio

capacitors install them on the PC board. When you have

Jupiter project, including Zener and varactor diodes and

determined that you have the installed the correct values

they all have polarity. In order for the circuit to work

into their respective location on the circuit board, you

properly, these devices must be installed with respect to

can solder the capacitors in place on the board.

their polarity. Diodes will generally have a white or

Remember to trim the excess capacitor leads from

black colored band at one edge of the diode body. The

the circuit board. Once you have the first grouping of

band usually denotes the cathode end of the diode.

capacitors installed you can move on to installing

Transistors generally have three leads—a Base,

another group of non-polarized capacitors, until

Collector and Emitter; pay particular attention to these

you have installed all of the non-polarized

leads when installing the transistors. Integrated circuits

capacitors.

always have some type of markings which indicate their

Next, find the electrolytic capacitors from the parts

orientation. You will find either a plastic cut-out on the

pile and we will install them in their proper locations.

top of the integrated circuit package or an indented

Refer now to the schematic and parts layout diagrams

circle next to pin 1 of the IC. Be sure to use these

so that you can orient the capacitors correctly when

markings when installing the integrated circuits. It is a

mounting them on the PC board. Install two or three

good idea to incorporate integrated circuit sockets as a

electrolytic capacitors and then solder them in place on

low cost insurance policy, in the event of a circuit

the PC board. Remember to cut the extra lead lengths

failure, if it ever happens. It is much easier to remove

flush to the PC board. Identify and install the remaining

an old dead IC, and simply insert a new one rather

electrolytic capacitors on the board and solder them in

than trying to undo many pins and risk damage to the

place. Trim the component leads as necessary.

circuit board.

In order to avoid damaging the receiver, it is

There are a number of coils in this project, and

important to install the capacitors, diodes as well as the

although there is no polarity to the coils, you will need

C

C

B

B

E

E

NPN

PNP

1

8

1

8

1

8

1

8

2

7

2

7

3

6

3

6

4

5

4

5

LM387

G

TO-92

SA602AN

S

NTE824

D

EBC

EBC

J310 JFET

2N3904

2N3906

Figure 22-5

Semiconductor pin-outs

241

to pay attention to the values of the coils as well as

The power cable supplied with the kit has a female

which ones are adjustable and which are fixed before

power plug on one end and stripped leads on the other.

installing them on the PC board. Note, on the schematic

Notice that the power cable has a black stripe, or tracer,

there are two points marked (A), one is at R6 and the

along one of the wires. This is the wire that is

other at C16, both of these points are connected

connected to the center conductor of the plug and must

together. Note, there is a test point marked (TP1) at the

be connected to the (+) side of the power source. The

OSC-1 module which can be used to ensure that the

Radio Shack RS 23-007 (Eveready) 12 volt battery or

oscillator module is working correctly.

equivalent is suitable.

Power is brought to the circuit via the coaxial power

Next, turn the Jupiter receiver’s power switch to OFF.

input jack at J1. The antenna connection is shown at J2.

Connect either headphones or an amplified speaker

This connector can be either a BNC or an “F” type

(Radio Shack 277-1008C or equivalent) to the receiver

chassis mounted connector. The receiver circuit

audio output (J3 or J4). These jacks accept 3.5 mm (1⁄8′′)

has two audio output jacks both at J3 and J4.

monaural or stereo plugs.

Two circuits of mini 1⁄8′′ stereo jacks were used in

If you are using a Radio Shack amplified

the prototype.

speaker, turn it ON and adjust the volume control

Once the printed circuit has been assembled, you will

on the speaker up about 1⁄8 turn. If you are using

need to recheck the solder joints to make sure they are

headphones, hold them several inches from your

smooth and that there are no cold solder joints. Also

ear as there may be a loud whistle due to the internal

observe the PC circuit lines to ensure that there are no

test oscillator. Turn the receiver ON. The LED should

bridges or “shorts” formed by cut component leads.

light. Set the volume control to the 12 o’clock

Once the circuit has been checked, you are ready to

position. Allow the receiver to “warm-up” for several

install the circuit board in the chassis.

minutes.

A metal enclosure was chosen, since this is a

Set the TUNING control to the 10 o’clock position.

sensitive RF receiver and you will want to keep outside

Carefully adjust inductor L5 with the white tuning stick interference from affecting the circuit operation, see

until a loud low frequency tone is heard in the speaker

Figure 22-2. You will have to wire the four jacks J1

(set volume control as desired). Caution: Do not screw

through J4 to the circuit board. We elected to mount the

down the inductor slugs too far, as the ferrite material

power and antenna jacks on the rear panel of the chassis

could crack. By adjusting L5 to hear the tone, you are

box. One audio jack was mounted on the front panel,

tuning the receiver to 20.00 MHz. The signal which you

while the second audio jack was mounted on the rear

hear is generated in OSC1, a crystal controlled test

chassis panel. The power switch S1 was wired to the PC

oscillator built into the receiver. Once L5 has been set,

and mounted on the front panel of the receiver along

DO NOT readjust it during the remainder of the

with the power indicating LED. The tuning control R7

alignment procedure. (When the receiver tunes

and volume control R15 were both mounted on the front

20.00 MHz with the nob set to the 10 o’clock position it

panel of the chassis box.

will tune 20.1 MHz with the knob centered on the

Once you are satisfied that your circuit board is

12 o’clock position.) The following steps involve

wired correctly. You are ready to apply power to the

adjusting variable capacitors (C2 and C6) and a variable

circuit and begin testing the circuit for proper

inductor (L4) to obtain the maximum signal strength

operation.

(loudest tone) at the audio output. For some, it is

difficult to discern slight changes in the strength of an

audio tone simply by ear. For this reason three different

methods are described, each using a form of test

Testing and alignment

instrument. In the event that no test equipment is

available, then a fourth method—simply relying on the

The receiver requires 12 volts DC (vdc) which may be

ear—is possible. In all cases, adjust the receiver tuning

obtained from a well regulated power supply or from a

knob so that the audio tone is in the range of about

Chapter Twenty-two: Jupiter Radio Telescope Receiver battery. Current drain is approximately 60 milliamps (ma).

500 to 2000 Hz. Use procedure A as a method to use in

242

Chapter Twenty-two: Jupiter Radio Telescope Receiver

tuning up your receiver. Procedures B-D are optional

tuning methods.

The jupiter radio

If no test equipment is available, then simply tune

telescope antenna

by ear for the loudest audio signal. Listen to the

tone and carefully adjust the tuning knob to keep the

The antenna intercepts weak electromagnetic waves that

pitch constant. If the pitch changes during the alignment,

have traveled some 500 million miles from Jupiter to

it indicates that the receiver has drifted

the Earth or 93 million miles from the Sun. When these

off frequency. As you make adjustments, the signal will

electromagnetic waves strike the wire antenna, a tiny

get louder. Reduce the receiver volume control as

radio frequency (RF) voltage is developed at the

necessary to keep the tone from sounding distorted or

antenna terminals. A basic dipole antenna is shown in

clipped.

Figure 22-6. The recommended antenna for the Jupiter

To test the receiver on the air, simply connect the

Radio Telescope is the dual dipole shown in Figure 22-7.

antenna. For best performance, use a 50 ohm antenna

Signals from each single dipole antenna are brought

designed to operate in the frequency range of

together with a power combiner via two pieces of

19.9–20.2 MHz. At certain times of the day, you should

coaxial cable. The output of the power combiner is

be able to hear WWV or WWVH on 20.000 MHz.

delivered to the receiver by another section of coaxial

These are standard time and frequency stations, located

transmission line. The antenna system requires a fair-

in Colorado and Hawaii, which broadcast the time of

sized area for setup: minimum requirements are a

day as well as other information related to propagation

25 × 35 ft. flat area that has soil suitable for putting

and solar-terrestrial conditions. The Jupiter Radio

stakes into the ground. As the antenna system is

Telescope direct conversion receiver design does not

sensitive to noise it is best not to set it up near any

allow clear reception of amplitude modulated (AM)

high tension power lines or close to buildings. Also for

stations like WWV, so the voice will probably be

safety reasons, please keep the antenna away from

garbled, unless you tune very precisely. The receiver

power lines during construction and operation.

does work well on single sideband (SSB) signals and

The best locations are in rural settings where the

code (CW).

interference is minor. Since many of the observations

In the event that the Jupiter receiver does not appear

occur at night it is wise to practice setting up the

to work, you will need to disconnect the power supply

antenna during the day to make sure the site is safe and

and antenna and examine the circuit board for errors.

easily accessible.

The most common cause for building errors are the

If you want to locate your receiver indoors and your

incorrect installation of the electrolytic capacitors and

antenna is outside or on the rooftop, and your

diodes which may have been installed backwards, since

antenna lead will not reach, you must use a longer

the components have polarity which must be observed.

Another possible cause for errors are the incorrect

placement of resistors. Often color codes are read

Antenna #14

Insulator

copper wire

wrong and the wrong resistor may be installed at a

particular location. Finally one of the most common

Eye bolt

3 ferrites

Eye bolt

causes for errors is the incorrect installation of

Coaxial λ/2

transistors and integrated circuits. Make sure that you

Support

of RG-59

Support

can identify the manufacturer’s pin-out diagrams and

mast

rope

pay particular attention to if the pin-outs are for top or

Connector

bottom views. Have a knowledgeable electronics

enthusiast help you scan the circuit for possible

mistakes; a second pair of eyes always helps to find

Stakes

errors you may have missed as the builder. Once you

have located and fixed the problem, you can apply

Figure 22-6

Basic dipole antenna diagram. Courtesy

power and re-test the circuit for proper operation.

Wes Greenman, Charles Higgins

243

1'

23' 3"

11' 6"

11' 6"

3"

25'

B

A

guy rope

λ of RG-59

coaxial

F

F

F power

combiner

To

receiver

λ/2 of RG-59 coaxial 16.3 ft

B'

A'

Figure 22-7

Antenna combiner diagram. Courtesy Wes Greenman, Charles Higgins coax cable. Do not use just any length of coax for the

need to maximize your chances of receiving the Jovian

combiner assembly. The cable going from the power

storms by picking the best opportunities, selecting a

combiner harness assembly to the receiver should be a

good observing site, and using good observing

multiple half wavelength long. The cable supplied with

techniques.

the kit is one wavelength—that is 9.85 meters long

During the daytime, the Earth’s Ionosphere blocks

(taking into account the 66% velocity factor of the RG-

Jupiter’s radio emissions, so therefore you will have to

59/U cable). The maximum recommended cable length

confine your investigations to night time listening.

is 5 wavelengths. There are many different

Radio noise from electrical sources, such as power

manufacturers and qualities of coaxial cable. The

lines, fluorescent lights, computers, and motors, can

75 ohm cable supplied with the kit is manufactured by

mask the signals from Jovian storms.

Belden and has a solid center conductor and velocity

factor of 66%. Radio Shack does not carry RG-59/U cable

If possible, try to select an observing sight away from

but they do have RG- 6 and the higher grade RG-6QS

buildings and power lines, also try to use portable power

(quad shield), which is also 75 ohm cable. Both of these

supplies such as a battery power supply. Note that Jovian

cables have a velocity factor of 78%. One wavelength at

radio storms may be short in duration, so persistence and

20.1 MHz in RG-6 cable is 11.64 meters. If you are going

luck are needed to capture Jupiter’s radio signals.

to put in a longer feedline we recommend that you

Night time observing from a temporary field setup can

completely replace the existing one wavelength piece—

be dangerous, so PLAN CAREFULLY!! Get permission

rather than splicing another length of cable onto the end.

in advance to use the site, set up before dark, and use

caution when walking around the site at night. The

Jupiter Radio Telescope has two audio outputs, one

Observing tips—jupiter’s

channel can be used for ordinary listening and the

second output jack can be used for recording. You can

radio emissions

elect to use a portable audio tape recorder, however,

note that nearly all common portable tape recorders use

Most Jovian radio storms, received with the Jupiter

an automatic recording level control circuit (ALC).

Chapter Twenty-two: Jupiter Radio Telescope Receiver radio telescope, will likely not be very strong. You will The ALC can mask the variations in the Jovian L bursts.

244

Chapter Twenty-two: Jupiter Radio Telescope Receiver

Use a tape recorder that allows you to SWITCH OFF

Note you could also elect to use an audio tape

the ALC. Keep the ALC turned off.

recorder to record the Jovian signals in the field and

Another alternative for recording Jovian storms is the

later when you return home play the tape recording into

use of a computer or laptop to record the signals from

your laptop or personal desktop computers. There are

your Jupiter radio telescope. Using a laptop computer to

many audio analyzing software programs out there on

record the Jovian storms has the distinct advantage that

the Internet, many are free. Many programs allow FTT

you can analyze the audio recording with special

and frequency division analysis.

spectral software which can help you make sense of the

complex signals received.

245

Chapter 23

Weather Satellite Receiver

R20,R31

2.2 k ohm,

1

Parts list

/watt, 5% resistor

4

R22

100 k ohm, 1/watt,

4

Weather Satellite

5% resistor

Receiver

R23

220 ohm, 1/watt,

4

R1

22 ohm, 1/watt,

5% resistor

4

5% resistor

R24

390 k ohm, 1/watt,

4

R2

150 k ohm, 1/watt,

5% resistor

4

5% resistor

R25

10 ohm, 1/watt,

4

R3

110 k ohm, 1/watt,

5% resistor

4

5% resistor

R26

1.5 k ohm, 1/watt,

4

R4,R10,R11

22 k ohm,

5% resistor

1

/watt, 5% resistor

4

R28

4.7 k ohm, 1/watt,

4

R5

47 k ohm, 1/watt,

5% resistor

4

5% resistor

R29

300 ohm, 1/watt,

4

R6

1.8 k ohm, 1/watt,

5% resistor

4

5% resistor

R30

47 ohm, 14watt,

R7

360 ohm, 1/watt,

5% resistor

4

5% resistor

VR1

50 k linear pot,

R8

100 ohm, 1/watt,

16mm PC board mount

4

5% resistor

VR2

25 k linear pot,

R9

470k ohm, 1/watt,

16mm PC board mount

4

5% resistor

VR3

50k log pot, 16mm

R12,R13,R16,R27

1 k

PC board mount

ohm, 1/watt,

4

VR4,VR5

50 k 10-turn

5% resistor

trimpots, PC board

R14

240 ohm, 1/watt,

mount

4

5% resistor

C1,C2,C3,C5

2.2 nF,

R15

1.2 k ohm, 1/watt,

16v, disk ceramic

4

5% resistor

capacitor

R17

5.6 k ohm, 1/watt,

C6,C7,C8,C12

2.2 nF,

4

5% resistor

16v, disk ceramic

R18

39 k ohm, 1/watt,

capacitor

4

5% resistor

C4,C10

3-10 pF trimcaps

R19,R21

10 k ohm,

C9

1 nF, 16v, disk

1

/watt, 5% resistor

ceramic capacitor

4

246

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Twenty-three: Weather Satellite Receiver

C11,C34,C35

10 µF, 16v

L2

see Table 23-3

tantalum capacitor

L3

see Table 23-3

C13,C27

10 pF, 16v, NPO

L4

see Table 23-3

ceramic capacitor

D2

5.1V 400 mW Zener

C14,C19,C21,C23,C25

diode

10 nF, 16v, mono

D3,D4

3 mm red LED

ceramic capacitor

D1

ZMV833ATA varicap

C15,C16

15 pF, 16v, NPO

ceramic capacitor

X1,X2

5.5 MHz ceramic

filters, Murata

C17

10 µF, 35v Tantalum

SFTRD5M50AF00-B0

capacitor

Q1

BF998 dual-gate

C18a,C18b,C20,C22

MOSFET

100 nF, 16v, mono

ceramic capacitor

Q2

PN100 NPN transistor

C24,C26,C28,C32

100 nF,

U1

SA605D mixer/IF

16v, mono ceramic

amplifier/FM detector

capacitor

U2

TL072 dual op-amp

C29

390 pF, 16v, NPO

U3

LM386 audio amp

ceramic capacitor

U4

78L05 +5V regulator

C30

4,7 nF,16v, metal

J1,J2

BNC type

polyester capacitor

jacks

C31

1 nF, 16v, metal

J3

1

/, 3.5 mm stereo

8

polyester capacitor

headphone jack

C33

470 nF, 16v, metal

J4

1 2.5 mm concentric

polyester capacitor

power socket, PC-mount

C36

330 µF, 16v,

S1

SPDT miniature

electrolytic capacitor

toggle switch

C37

47 nF, 16v, metal

Misc

PC board

polyester capacitor

(double-sided, not

C38

22 nF,16v, metal

plated through)

polyester capacitor

TO-220 heatsink,

C39

2200 µF, 25v,

1 coil former,

electrolytic capacitor

4.83 mm OD with F16

C40

470 µF, 35v,

ferrite slug

electrolytic capacitor

1 F29 ferrite bead

RFC1

4.3 µH slug tuned

(for RFC1)

coil – see Table 23-3

1 short length of

RFC2

10 µH slug tuned

0.8 mm tinned copper

coil – prewound

wire for L1

RFC3

68 µH slug tuned

1 length of 0.8 mm

coil – prewound

enameled copper wire

L1

see Table 23-3

for L2, L3

247

the ground at a frequency just above 137 MHz. The

satellite will be in range for up to 12 minutes as the

satellite passes from horizon to horizon.

The broadcast uses the APT (Automatic Picture

Transmission) analog format for the imagery. (A digital

format High Resolution Picture Transmission (HRPT)

signal is also transmitted but it is more difficult to

receive and decode and we did not try to receive it in

this project.) Currently, there are six operational NOAA

polar orbiters but usually only two or three have the

APT activated at a given time. (In this report, only

images from NOAA-14 and NOAA-15 were received.)

See NOAA satellite status.

The Russian METEOR series of satellites also

broadcast with the APT format. In addition, the remote

Figure 23-1

Satellite view – USA

sensing SICH and OKEAN radar satellites occasionally

broadcast images but only over Russia (scanners in

The days of guessing the weather by looking at the

nearby countries have picked up some of these images).

clouds overhead have just ended. Now you can look at

the clouds from above! This satellite receiver/decoding

project will allow you to receive pictures from satellites

600 km overhead, see Figure 23-1. A typical NOAA

The APT system

satellite can cover nearly one-sixteenth of the Earth in a

single pass! Living in New York, for example, we can

The APT satellites give about 12 good images a day,

clearly capture images from mid-Hudson bay (where

wherever you are in the world. The resolution is 4 km

there was still ice in late spring), all the way down past

per pixel and there are visible and infrared sensors. This

Cuba, as well as spanning from Wisconsin to far out in

is a simple system where the satellite is in low Earth

the Atlantic Ocean. The clarity of the image was enough

orbit and very easily received at 137 MHz. The two

to see the individual Finger Lakes (in New York), and

frequencies in main use are 136.50 for NOAA 12 and

shadows on the underside of thunderstorms. With the

15 and 137.62 MHz for NOAA 14. A simple crossed

weather satellite receiver and a personal computer, you

dipole antenna can be used, or for marine use a

can easily receive and decode weather satellite pictures

stainless steel quadrifilar helix antenna. These simple

from overhead satellites.

omni-directional antennas do not need moving or

The US National Oceanographic and Atmospheric

tracking to receive the satellite. The satellite is so

Administration (NOAA) operates both GEO and LEO

strong that when is about 20° above the horizon

polar satellites. Here we concentrate primarily on the

perfect results will be obtained. The APT signal is

polar orbiters. The NOAA polar satellites orbit at 850 km

easily recognizable by its modulated frequency (FM)

and pass within view of all areas on Earth at least twice

and carrier tonality ranging between 1500 and 2500 Hz.

day. The satellite carries a number of instruments

New satellites have a 2400 Hz carrier like this NOAA

including cameras for both visible and infrared light.

14 APT signal.

The cameras scan back and forth at right angles to the

In APT mode, satellites transmit at the rate of

ground path, like a broom sweeping side-to-side as you

120 LPM (lines per minute) alternating two channels,

walk forward, taking picture strips that cover an area

one for the visible image, the other for the infrared

3000 km wide. The satellite thus makes a continuous

image. This is through the decoding software that you

picture as if it were a tape reeling out from an endless

select one or another channel.

roll. The image, however, is not recorded on the

Russian weather satellites only transmit infrared

Chapter Twenty-three: Weather Satellite Receiver satellite. Each image strip is immediately broadcast to images at 120 LPM. The sound of their transmission is

248

Chapter Twenty-three: Weather Satellite Receiver

thus slightly different from the other weather satellites

receiver at the same time they are taking in the view.

like on this record of a RESURS 01-N4 signal with an

Meanwhile during the same part of the scan, they are

IOC of 382. On their side, METEOR 3-05 uses a

recording the infrared view. During the second half of

higher carrier closer to 2500 Hz with an IOC of 382

the scan, while the sensors are facing away from the

as well.

Earth, it sends the infrared data. The user then sees

the data as two images side by side, on the left the

The WX satellite receiver project will allow you to

visible light data is seen, and on the right, infrared data

receive weather satellite transmissions on the VHF

is seen. In between the images are synchronization

band, where most of the polar-orbiting satellites are

pulses that help computers to align the individual lines

located. You will recognize these transmissions on the

precisely.

news when you see the time lapse of the clouds darting

across the countryside. The weather man in this case

These particular satellites continuously transmit an

has taken multiple images on the computer, aligned and

FM signal modulated with a 2400 Hz tone. This tone is

pieced them together, and then run through one image

very precise in frequency so the image seen is aligned

after the other. It is possible to do this same thing with

properly. The 2400 Hz tone is AM modulated with the

this kit and the proper software.

intensity of the current view of the Earth. The brighter

or colder the point on the Earth, the higher in amplitude

The way in which a weather satellite works is fairly

the 2400 Hz signal is.

simple. Just think of your office fax machine as an

The receiver demodulates the FM signal and

example. The satellites circle the Earth going north to

retrieves the 2400 Hz tone. The detector board in the

south back to north again almost directly over the poles,

computer will then find the peak amplitude of each

which is why they call it a polar orbit. This means that

wave of the 2400 Hz tone, and each peak, upper and

the satellite will cover every location on the Earth at

lower, now represents a single pixel on the screen. For

least twice per day. With a good antenna, and partly

the NOAA/TIROS satellites, each horizontal line

because of overlap of consecutive orbits, you can

represents 2400 pixels, since the incoming frequency is

conceivably receive the same satellite up to six

2400 Hz, and the scanning radiometer rotates twice

times a day! Notice though that the image received

per second. The full 12 minute pass of a NOAA

from polar orbits will be upside down on every

satellite requires approximately 3.5 MB (3.5 million 8

other pass.

bit pixels) of storage! This is much more data (pixels)

The satellite retrieves the data in a linear fashion,

than can be seen on a super VGA screen at any

one line at a time using a scanning radiometer.

one time.

The scanning radiometer transmits the equivalent of a

Many people mistakenly think that they can easily

single television horizontal line as the satellite circles

utilize a conventional VHF scanner as an APT satellite

the earth. The system uses a series of optics and a motor

picture receiver. Most scanners and communications

driven rotating mirror system to receive a very narrow

receivers usually only provide a choice of two

line of the image of the Earth. Each line is received at a

bandwidth settings for VHF FM reception: “narrow”

right angle to the satellite’s orbital track, so as the

and “wide.” The narrow setting gives a bandwidth of

satellite circles the Earth, a line is received from west to

±15 kHz or less, which is fine for NBFM reception, and

east or east to west depending on the orbit of the

the wide bandwidth setting usually gives a bandwidth of

satellite. The total image is received from north to south

about ±100 kHz, so this is the setting that must be used.

or south to north, depending on the orbit also, and this

Unfortunately, this “wide” bandwidth is actually too

motion is what relays the equivalent of the vertical scan

wide for weather satellite signals and, as a result, the

in a television. You can continue receiving this satellite

demodulated audio level is relatively low. At the same

as long as it is within the line of sight.

time, the wider reception bandwidth allows more noise

Since all of the receivable satellites are similar, we

through, so the signal-to-noise ratio can become quite

will describe the ones you will most commonly

poor. Only a few scanners have the correct bandwidth

receive. The NOAA/TIROS satellites, during the first

and these currently include the AOR5000 and Icom

half of the transmission, send visible light data to the

IC-PCR1000. The second problem with all scanners,

249

This type of specialized VHF receiver is available

but fairly pricey. Hence the motivation for

developing the low-cost weather satellite receiver

described here.

The weather satellite receiver project in this chapter

features good sensitivity, at about 0.7V for 12 dB of

quieting. At the same time, the effective bandwidth is

approximately ±35 kHz, which is quite suitable for

weather satellite reception. The satellite receiver is built

into a very compact plastic instrument box, as shown in

Figure 23-2. All of the circuitry is mounted on a

double-sided PC board, so it’s quite easy to build. It has

switch tuning between two preset frequency channels,

for ease of use. There are RF Gain, Audio Muting and

Figure 23-2

Weather satellite receiver

Audio Gain controls and the receiver can drive a small

monitor speaker or headphones, as well as providing a

including the ones mentioned, is that a weather satellite

line level signal to feed into your PC for recording and

system needs a very good performance receiver, one

decoding.

that provides high sensitivity, good signal to noise and

The heart of the receiver is a Philips SA605D IC

high immunity to other adjacent transmissions. So, you

high-performance low-power FM mixer and IF system

may get a scanner to work, but it will not provide the

on a single chip. As you can see from the block diagram

optimum results.

of Figure 23-3, it contains a local oscillator transistor

Ideally, in order to obtain the best results you really

and balanced mixer, plus a high-gain IF amplifier and

need to have a receiver with a ±30 kHz bandwidth.

IF limiter, a received signal strength (RSSI) detector, an

IF filter

IF filter

X1

X2

20

19

18

16

12

14

16

V CC

IF amplifier

1

Mixer

IF limiter

RF

11

input

2

10

Quad

detector

Local

RSSI

oscillator

detector

B

E

4

3

15

7

8

5

9

Mute

To oscillator

RSSI

Muted

90° phase

Audio

tuned circuit

out

audio

shift

out

Chapter Twenty-three: Weather Satellite Receiver Figure 23-3 Weather satellite receiver block diagram 250

Chapter Twenty-three: Weather Satellite Receiver

FM quadrature detector and finally an audio muting

circuit is then fed directly to gate 1 of Q1, while gate

circuit. The local oscillator transistor can operate at

2 is bypassed to ground but also fed with an adjustable

frequencies up to about 500 MHz in an LC circuit, or

DC voltage via VR1 for RF gain control. The amplified

up to 150 MHz with a suitable crystal. The mixer can

VHF signal on Q1’s drain is fed to pin 1 of U1 via a

operate up to 500 MHz as well, while the IF amplifier

1 nF coupling capacitor. Additional RF selectivity is

and limiter can operate up to about 25 MHz with a

provided by coil L2 and trimmer capacitor VC2, which

combined gain of about 90 dB.

are again tuned to about 137.55 MHz. The 100 ohm

resistor and 10 µH RF choke form an untuned high-

The main receiver diagram illustrated in Figure 23-4

impedance load for Q1.

depicts the complete weather satellite receiver circuit

details. In this receiver project, we’re using the SA605D

Notice that as well as being coupled to the tap on

in a fairly conventional single-conversion superhet

L1 via a 2.2 nF capacitor, the antenna input is also

configuration, with the IF amplifier and limiter working

connected to the +12V supply line via RFC1 and a

at 5.5 MHz. This allows us to take advantage of high

series 22 ohm resistor. As you may have guessed, these

selectivity 5.5 MHz TV sound IF ceramic filters to

components are there to provide “phantom” DC power

provide most of our bandwidth shaping. The two filters

for the masthead pre-amplifier. At the output end of U1,

in question are X1 and X2, which are both Murata

we take the demodulated APT signals from the “muted

SFT5.5MA devices.

audio” output at pin 8. This allows us to take advantage

of the SA605’s built-in muting circuit, which works by

As shown in the receiver schematic, X1 is connected

using comparator stage U2b to compare U1’s RSSI

between the mixer output and the IF amplifier input,

output from pin 7 (proportional to the logarithm of

while X2 is connected between the IF amplifier output

signal strength) with an adjustable DC control voltage

and the limiter input. The resistors connected to the

from muting pot VR2. When the RSSI voltage rises

filter inputs and outputs are mainly for impedance

above the voltage from VR2, U2b’s output switches

matching, while the 10 nF capacitors are for DC

high and this is fed to pin 5 of U1 via a 2.2 k ohm series

blocking. The 90° phase shift required for U1’s

resistor to un-mute the audio. D2, a 5.1V Zener diode,

quadrature FM detector is provided by coil L4 and its

limits the swing on pin 5 of U1 to less than 6V.

parallel 390 pF capacitor, which are tuned to 5.5 MHz.

Transistor Q2 and LED1 form a simple signal

The local oscillator transistor inside U11 is connected

strength indicator. This also uses the RSSI output from

in a Colpitts circuit. This includes coil L3, together with

U1. In operation, the voltage across the 390 k ohm

the two 15 pF capacitors (which provide the emitter tap)

resistor and 100 nF capacitor rises from about +0.26V

and a 10 pF capacitor in series with the Varicap

under no-signal conditions to about +5V with a very

diode D1.

strong input signal. So with Q2 connected as an emitter

The Varicap diode D1 is the receiver’s tuning

follower and LED1 in its emitter load, the LED current

capacitor. Its tuning voltage for each of the two

and brightness are made to vary quite usefully with

channels is set by 10-turn trimpots VR4 and VR5, with

signal strength.

switch S1 selecting between them. We can tune the

The demodulated APT signal from pin 8 of U1 is first

receiver simply by changing the local oscillator

fed through op-amp U2a, which is configured as an

frequency because we only need to tune over a

active low-pass filter. This has a turnover frequency of

relatively small range (i.e. 137.3–137.85 MHz

5 kHz and is used for final de-emphasis and noise

maximum), which is within the selectivity curve of the

reduction. From there, the signal is fed to audio gain

“front end” tuned circuits.

control VR3 and then to audio amplifier stage U3. This

The satellite receiver’s front end uses a BF998 dual-

is a standard LM386 audio amplifier IC, configured for

gate MOSFET (Q1) connected in a standard cascode

a gain of about 40 times. Its output is fed to both the

amplifier configuration. The incoming VHF signals are

monitor speaker socket and to a line output socket for

fed into a tap (for impedance matching) on antenna coil

connection to your PC’s sound card.

L1, which is tuned to about 137.55 MHz using trimmer

Most of the receiver’s circuitry operates from +12V,

capacitor VC1. The signal from the top of this tuned

with the exception of U1 which needs +6V. As a result,

251

C h a p t e r T w e n t y - t h r e e : W e a t h e r S a t e l l i t e R e c e i v e r 252

X1

RfC2

+12 V

R12

R13 R14 R15

+

C6

R16

C1

R4

C11

R1

C19

C21

C23

C25

VR1

C20

C22

C24

C26

R6

R8

C7

C9

20

19

18 17

16

15

13 14

12

1

R5

11

C27

R2

L2

C28

RfC1

G1

U1

G2

D

L4

C10

10

2

4

3

5

6

7

8

C12

C29

S

G1

R17

C30

J1

L1

C14

+12 V

C8

C4

C17 +

C18

C2

R7

C5

R9

R18

C13

C15

RfC3

J2

C33

C3

R3

3

1

R27

L3

C31

U2:A

C16

2

D1

+6 V

R11

R26

+6 V

+12 V

B

+12 V

+

VR4

VR5

c

+

6

C34

R20

R19

R22

8

3

5

b

Q2

1

C36

S1

7

8

J3

A

5

+

D2

U2:B

U3

6

C32

c

7

2

4

R24

4

R10

+

R25

R23

C35

C37

A

D3

R21

K

+6 V

+12 V

J4

R28

Out

In

Out

In

U4

U5

VR2

R29

R31

+

+

+

C38

C39

C40

P4

R30

Figure 23-4

Weather satellite receiver schematic. Courtesy of Silicon Chip Magazine Chapter Twenty-three: Weather Satellite Receiver

the power supply circuitry includes U5 to provide a

Construction of the weather satellite receiver is

regulated and smoothed +12 V supply from an external

straightforward with virtually all of the parts mounted

supply such as a 14.5–18 V “wall-wart.” This is

on a small PC board. The board is double-sided but the

followed by 5V regulator U4 which has its output

top copper pattern is used mainly as a ground-plane.

“jacked up” using 300 ohm and 47 ohm resistors to

This means that the board doesn’t need to have plated-

provide close to +6 V for the SA605D (U1). Note that if

through holes but there are quite a few component leads

you want to run the receiver from a 12 V battery, this

which do have to be soldered on both sides of the board.

can be quite easily done by replacing REG1 with a wire

There are also a number of “pin-through” or “hole-

link. In addition, the 2200 µF capacitor should be

through” wires which have to be soldered to both sides

replaced with a 16 V Zener diode (ZD2) for

of the PC board around U1. These connect the Earth

over-voltage protection.

patterns on both sides of the board and ensure that this

high-gain chip operates in a stable manner.

The various input and output connectors are mounted

Construction

along the rear edge of the circuit board, while the

controls and indicator LEDs mount along the front

Before beginning the project make sure that you have a

edge. The only component not actually mounted on the

clean well lit and well ventilated work space for

board is S1, the channel select toggle switch. This

constructing your satellite receiver. Locate all the

mounts on the front panel, with its three connection lugs

diagrams and place them in front of you on the table or

wired to PC board terminal pins directly underneath

work bench. Locate a 27 to 30 watt pencil-tip soldering

using very short lengths of insulated hookup wire.

iron, along with some “Tip Tinner,” which is used to

Start the assembly by mounting these three terminal

prepare and clean your soldering iron tip. Locate a roll

pins first, they are the only pins used in the receiver

of 60/40 tin/lead rosin core solder as well as a few small

project. Next, mount the four connectors CON1-CON4

hand tools such as a pair of small end-cutters, a

along the rear edge, followed by the resistors. Table 23-1

needle-nose pliers, a pair of tweezers, and some small

shows the resistor color codes but it’s also a good idea

screwdrivers.

to check each value using a digital multi-meter before

Table 23-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

253

soldering it in position. All resistors are mounted to the

don’t forget to fit its “tap” connection lead as well. This

top of the PC board but note that some of them have

can be made from a resistor lead off-cut, since it’s very

one lead soldered to the top copper as well as the

short. It connects to a point 1⁄3 of a turn up from the

bottom copper. Once the resistors are in place, you can

“cold” (earth) end of the coil, i.e. just above half-way

use excess resistor leads to allow connection from one

up the side of the first turn.

side of the board to the other side, since this project

The final coil to wind is quad detector coil L4. Unlike

uses a two-sided circuit board. Each “pin-through or

the others, this is wound on a 4.83 mm OD former with

through-hole” is fitted by simply passing a wire through

a base and a copper shield can. It’s wound from 20

the hole in the board, then soldering it on both sides and

turns of 0.25 mm enameled copper wire and tuned with

trimming off the excess lead lengths.

an F16 ferrite slug. Coil formers with ferrite slugs are

The small ceramic capacitors can now all be installed

difficult to locate, check the Appendix. You could

on the left-hand side of the board. Note that some of these

also experiment with a small “junk” IF transformer

also have their “cold” leads soldered on both sides of the

can. You could try and unwind the existing coil and

board, as indicated by the red dots. Once they’re in,

re-winding your own coil over the plastic former.

install the MKT capacitors and the electrolytic capacitors,

You must make sure that there is a ferrite slug in the

making sure that the latter are all correctly orientated.

center of the coil former. Once L4 is wound, and

Use the chart shown in Table 23-2 to help locate the small

installed onto the board, cover it with its shield can.

capacitors from the parts pile. Often small capacitors do

You can next mount the two ceramic filters X1 and X2.

not have their actual value printed on them but instead use

These devices can be fitted either way around but make

a three-digit code to represent the actual value.

sure that their pins are pushed through the board holes

as far as they’ll go before you solder them

Finally go ahead and mount the trimmer capacitors

underneath.

VC1 and VC2. These should be mounted so that their

adjustment rotors are connected to earth (this makes it

The next step is to construct and install the small

much easier to align the receiver later). It’s simply a

metal shield around coil L2, C10 and most of the

matter of orientating them on the board.

components in the drain circuit of Q1. This shield is

U-shaped and measures 20 mm high, with the front and

Next, we will move on to installing the RF chokes.

back “arms” 36 mm long and the side section 20 mm

RFC2 and RFC3 are both pre-wound (10 µH and 68 µH

long. The bottom edges of all three sides are soldered to

respectively) but RFC1 needs to be wound on an F29

the board’s ground-plane in a number of places, to hold

ferrite bead. It’s very easy to wind though, because it

it firmly in position and to ensure it stays at earth

requires only three turns of 0.25 mm enameled

potential.

copper wire.

The two 10-turn trimpots (VR4 and VR5) can now be

soldered in position at the front-center of the board.

They can then be followed by the three main control

Winding coils

pots, which are all 16 mm diameter types. Trim each

pot’s spindle length to about 9 mm before fitting it and

At this point in time, it’s a good idea to wind and mount

make sure you fit each one in its correct position as they

the remaining coils. Table 23-3 gives the winding

are all different. In particular, note that VR1 and VR3

details of the coils. As shown, L1–L3 are air-cored

both have a value of 50 k ohm but VR1 is a linear pot

types, each consisting of five turns of 0.8 mm diameter

while VR3 is a log type.

wire wound on a 5 mm mandrel. Note, however, that L1

After installing the potentiometers, it’s a good

is wound using tinned copper wire, while L2 and L3 are

idea to connect their metal shield cans together

both wound using enameled copper wire. Don’t forget

and then run a lead to the board’s top copper to earth

to scrape off the enamel at each end, so they can be

them. This is done using a length of tinned copper

soldered to the board pads.

wire, with a short length of insulated hookup

Coils L1–L3 should all be mounted so that their turns

wire then connecting them to the board copper at

Chapter Twenty-three: Weather Satellite Receiver are about 2 mm above the board. After you’ve fitted L1, front right.

254

Chapter Twenty-three: Weather Satellite Receiver

Table 23-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

820 pF

Ceramic

821

2

Mylar

205

255

Table 23-3

Note that U5’s center pin should be soldered on both

Coil winding details

sides of the board but take care not to touch either of

the two large adjacent electrolytic capacitors with the

L1

5 turns of 0.8 mm (20 ga.) tinned copper wire, 7 mm

barrel of your soldering iron.

long (wound on 5 mm diameter mandrel). Tap at

Go ahead and mount regulator U4, followed by U22

0.3 turns. Air core, mounted 2 mm above board.

(TL072) and U3 (LM386). Note that pin 4 on both these

L2

5 turns of 0.8 mm (20 ga.) enameled copper wire,

devices should be soldered to the copper on the top of

9 mm long (wound on 5 mm diameter mandrel).

the board as well as the bottom. The two D3 and D4 are

Air core, mounted 2 mm above board.

both mounted horizontally, so that they later protrude

L3

5 turns of 0.8 mm (20 ga.) enameled copper wire,

through matching 3 mm holes in the front panel. Note

8 mm long (wound on 5 mm diameter mandrel).

that they are both fitted with their cathode leads towards

Air core, mounted 2 mm above board.

the left. Bend their leads down through 90° about 5 mm

L4

20 turns of 0.25 mm (30 ga.) enameled copper wire,

from the LED bodies, then solder them in position so

that the axis of each LED is 5 mm above the board.

tight wound on 4.83 mm OD former with F16

tuning slug and shield can.

The final components to be mounted on the PC board

RFC1

3 turns of 0.25 mm (30 ga.) enameled copper wire

include the Dual-Gate MOSFET at Q1 and the SA605D

wound on an F29 ferrite bead.

IC at (U1), U2 and transistor Q2. These components

should be handled very carefully, using an anti-static

wrist-band to avoid static charges building up on the

components. The two integrated circuits should be

Mounting the

mounted in IC sockets. IC sockets are an insurance

policy against circuit failure at a later date. It is much

semiconductors

easier to simply unplug a faulty IC, rather than trying to

un-solder 14 or 16 pins from the circuit. Most people

Before we go ahead and install the semiconductors, let’s

cannot un-solder 16 pins without damaging a circuit

take a brief look at the semiconductor pin-out diagram

board. When mounting the IC sockets, observe a small

illustrated in Figure 23-5, which will assist you in

cut-out at one edge of the socket. The cut-out will

orienting the integrated circuits. Now you can go ahead

identify the top of the socket. Usually pin of the IC will

and mount the semiconductors. Begin by installing the

be located to the left of the cut-out. Solder the sockets

Varicap diode at D1, and the 5.1V Zener diode at D2

in their respective locations. Finally insert the ICs into

and transistor Q2. Next, install regulator U5 and its

their respective sockets, noting pin 1 is to the left of the

associated heatsink. These parts are secured to the board

small indented circle or cut-out on the top of the IC

using a 6 mm-long M3 screw, nut and lock-washer.

package. When handling the MOSFET be extremely

(TO-92)

Plastic Package (Z)

1

20

1

8

1

8

OUTPUT

INPUT

2

19

1

8

1

8

3

18

2

7

2

7

4

3

6

3

6

17

4

5

4

5

5

16

DAO

6

15

TL072

LM386

00774400

7

14

Bottom View

8

13

9

12

10

11

78L05

SA605

Chapter Twenty-three: Weather Satellite Receiver Figure 23-5 Semiconductor pin-outs 256

Chapter Twenty-three: Weather Satellite Receiver

careful to avoid damage from static electricity. Do not

move around when installing these static sensitive

Circuit test

components and be sure to use an anti-static wrist band

to avoid damage.

First, turn all three front-panel pots fully anticlockwise,

The completed PC board is housed in a suitable

connect up your antenna to the antenna input connector,

low-profile plastic instrument case.

and then apply power from a suitable 14–18V DC

“wall-wart” power supply or a 12V battery. Check that

First, you can mount switch S1 on the front panel and

the green power LED immediately begins glowing.

connect three 30 mm lengths of insulated hookup wire

to the three pins on the PC board. That done, the front

If it does, check the voltage on REG1’s output lead

panel can be mated with the PC board by positioning

(i.e. the right-hand lead) with your multi-meter, it

it on the three pot ferrules and doing up the nuts.

should read close to +12V with respect to ground.

The three leads from the PC board pins can then be

Similarly, the voltage at REG2’s (right-hand) output pin

soldered to the switch lugs.

should measure very close to +6V.

The rear panel is not attached to the board assembly.

If you now plug an 8 ohm speaker into CON3

Instead, it simply slips over connectors CON1 and CON2

terminals, and then turn up audio gain control VR3, you

and is then slid into the rear slot when the assembly is

should hear a small amount of hiss and noise. When you

fitted into the bottom half of the case. Now go ahead and

turn up the RF gain control VR1 as well, this noise

mount the antenna connector onto the rear panel. Finally,

should increase a little further but LED1 shouldn’t

the completed assembly is fastened in place using eight

begin glowing except only very faintly when VR1 is

6 mm-long 4-gauge self-tapping screws.

turned fully clockwise.

Now turn VR1 fully anticlockwise again and use your

After completing the circuit board assembly, you

multi-meter to measure the DC voltage at the top of the

should take a short rest and when we return we will

390k resistor located just behind transistor Q2 (i.e. to

inspect the circuit board for any possible “short” circuits

the right of 5.1V Zener diode). The voltage across this

or “cold” solder joints. Pick up the circuit board with

resistor should be less than 0.30V and preferably about

the foil side of the circuit facing upwards toward you.

0.26V. If it’s any higher than 0.30V, the IF amplifier in

First inspect the circuit board for possible “cold” solder

IC1 may be unstable. Assuming that your receiver has

joints. All of the solder joints should look clean, bright

passed all these tests, it should be working correctly and

and shiny. If any of the solder joints look dark, dull or

is now ready for alignment.

“blobby,” then you should un-solder that particular joint,

remove the solder then re-apply some solder and re-

solder the joint all over again. After inspecting all of the

solder joints, we can move on to looking for “short”

Receiver alignment

circuits. Often sticky rosin core solder will leave a

residue on a circuit board. When excess component

The final alignment of the weather satellite receiver is

leads are cut from the board during assembly, many

best done with a satellite signal. However, you need to

times the “cut” leads will stick to the circuit board and

give it a basic alignment first so that you can at least

they can “bridge” across the circuit pads and cause a

find the signal from a satellite when it’s within range.

“short” circuit which could damage the circuit when

For the basic alignment, you’ll need access to a

first powered-up. Another potential cause for a

frequency counter capable of measuring up to 150 MHz

“short” circuit is a small solder ball which may

and an RF signal generator which can be set to give an

have stuck to the circuit board, this too can cause a

output at 137.50 MHz and at 137.62 MHz. It should be

“short” circuit.

able to provide either unmodulated (CW) output or

Once you have inspected the circuit board to your

frequency modulation, with a modulating frequency of

satisfaction, you can connect up the power supply leads

2.4 kHz and a deviation of ±25 kHz or thereabouts. If

to the power input jack and you will be ready to test the

the generator can’t be accurately set to the above

weather satellite receiver.

frequencies, you’ll need to use the frequency counter to

257

help set its frequency. You’ll also need your multi-meter

Now turn up RF gain control VR1 to about midway and

during the “tuning-up” process, to monitor received

use an alignment tool or a very small screwdriver to

signal level.

adjust trimmer cap C10 until you find a peak in the

voltage reading on a multi-meter. If you can’t find a

The first step is to set the local oscillator frequencies

peak, you may have to pull the turns on coil L2 slightly

for the two reception channels. This is done by

further apart to reduce its inductance. Once the peak is

adjusting trimpots VR4 and VR5 respectively, while

found, adjust VC2 carefully to maximize the meter

measuring the oscillator’s frequency with the frequency

reading (the multi-meter is reading the RSSI voltage

counter. The oscillator signal is coupled to the counter

from IC1, so it’s essentially showing the received signal

via a “sniffer” coil which is connected to the end of a

strength).

coaxial cable. The other end of this cable is then

connected to the counter’s input. Note that there is no

When you’re certain that the L2/C10 circuit is tuned

direct physical connection between the oscillator coil

to 137.5 MHz, check the actual voltage reading of the

and the counter’s sniffer coil. Instead, the sniffer

meter. If it’s more than 2.5V, reduce the output level

coil is placed about 9 mm in front of oscillator coil (L3)

from the RF generator until the multi-meter reading

and roughly on-axis (i.e. just in front of the 10 pF

drops to about 2.0V. Now you’re ready to peak the

capacitor).

receiver’s input tuned circuit—i.e. L1 and VC1. This is

The sniffer coil can be made by winding four

done in exactly the same way as for L2 and C10. Just

turns of 0.8 mm enameled copper wire on a 5 mm drill

adjust C4 slowly until the multi-meter indicates

shank. Its ends can then be soldered to a BNC socket

a peak and then carefully set C4 for the maximum

which is then connected to the end of the counter input

peak reading. If you can’t find another peak, you

cable. This arrangement picks up enough oscillator

may need to pull the turns of L1 slightly further apart

energy to give reliable counter readings, without

as before.

needing to be any closer to L3 (to avoid “pulling” the

The final alignment step is to set the slug in

frequency).

quadrature detector coil L4 to the correct position for

Assuming you want to receive the NOAA satellites,

optimum FM demodulation of the 5.5 MHz IF signals.

set the oscillator frequency for channel A to 132.0 MHz

This is done by first switching the signal generator so

(using VR4), and the frequency for channel B to

that it’s still producing a 137.5 MHz signal but this

132.12 MHz (using VR5). These correspond to

should now be frequency modulated—preferably with a

reception frequencies of 137.5 MHz for NOAAs 12 and

2.4 kHz tone and a deviation of about ±25 kHz.

15 and 137.62 MHz for NOAA 17. If you want to try

Now, connect an 8 ohm speaker to the receiver’s

for other satellites, you’ll need to find out their APT

speaker socket (CON3) and turn up the audio gain

frequency and set the oscillator frequency to

control (VR3) to about the 10 o’clock position. You may

5.5 MHz below that figure instead, and adjust the

not be able to hear the 2.4 kHz modulating signal at this

tuning controls.

stage but in any case, slowly and carefully adjust the

Once the oscillator frequencies have been set, the

slug in L4 using a non-magnetic alignment tool. Sooner

next step is to peak up the RF stage tuned circuits. This

or later you’ll start to hear the 2.4 kHz tone and you

is done by setting your RF signal generator to produce

should also be able to tune the coil for maximum audio

an unmodulated (CW) signal at 137.5 MHz, initially

level and minimum distortion and noise.

with a level of about 30 mV. That done, connect the

Once this has been done, the basic alignment of your

generator’s output to the antenna input of the receiver,

weather satellite receiver is finished and it’s ready for

using a series DC blocking capacitor if the generator

final alignment using the signals from a weather

doesn’t have one (so that the generator doesn’t short out

satellite. But before you’ll be able to do this, you’ll

the +12V phantom power for the masthead amplifier).

need to build or buy a suitable antenna and perhaps a

Next, connect your multi-meter (set to the 5V DC

small masthead pre-amplifier to boost the signal if

range) across the 390k ohm resistor just behind Q2 and

necessary. The best antenna for APT weather satellite

Chapter Twenty-three: Weather Satellite Receiver make sure switch S1 is set to the channel A position.

reception is either a turnstile or quadrifillar antenna.

258

Chapter Twenty-three: Weather Satellite Receiver

Figure 23-6

VHF turnstile antenna

Figure 23-7

Quadrifillar antenna

the receiver. If you are using large diameter coax,

it may be necessary to use a UHF-BNC adapter.

APT antenna

Another alternative is to use a short length of smaller

considerations

diameter, more flexible, coax between the main cable

and the receiver. That cable can have a BNC plug on

one end and a UHF plug and double female adapter on

The crossed dipole or turnstile antenna is shown in

the other. If you use a 137 MHz pre-amplifier, you can

Figure 23-6; it is recommended for nearly all APT

overcome some cable losses by installing the pre-amp

weather satellite applications. It is made from aluminum

right up at the antenna. This establishes a low noise

and is strong and durable. It can be fixed onto a vertical

figure before going through the loss of the cable. If you

mast and should be positioned as high as possible. The

find you do need a 137 MHz mast-head pre-amplifier,

satellite signal will not go through trees or buildings and

you can build one or buy one from Hamtronics or

to get the best possible continuous signal it needs to be

Ramsey Electronics. We do not recommend trying to

mounted onto a mast as high as possible. On the end or

feed B+ to power the pre-amp through the coax as some

top of a building is preferred although, for test purposes,

enthusiasts do. It doesn’t pay to try to save the small

it can simply be stuck into the grass at ground level.

cost of lightweight hook-up wire and de-grade the

Another good choice for APT satellite reception is

performance of the pre-amp in the process.

the quadrifilar helix antenna, see Figure 23-7. It offers

Run a separate wire pair to power the pre-amplifier

slightly better performance than the crossed dipole but it

if needed.

is considerably more costly.

The success of weather satellite reception is very

much dependent on having a good antenna. The ARRL

Weather Satellite Handbook, is a good source of

Receiver operation

information on building antennas and low-cost antenna

pre-amplifiers. You can either build a good antenna or

Operation of the receiver is fairly obvious, but we will

readily purchase one from one of the vendors listed in

comment on several features of interest. Normally,

the Appendix. Good quality, low-loss 50. coax should

when used to drive a computer’s sound card, you will

be used between the antenna and the satellite receiver,

want to listen on a speaker to hear what the signal

since satellite signals are generally weak. The coax

sounds like. The VOLUME control can be adjusted to

should be plugged into the BNC jack on the rear of

whatever level is comfortable for listening and proper

259

for the computer’s sound card. This is especially true

Antenna

during the initial acquisition period. However, most

times you probably want the ability to mute the speaker;

so installing a switch in line with the receiver output to

the speaker is handy.

Pre-amplifier

Sound

To adjust the SQUELCH control, turn it clockwise

Satellite receiver

decoder

card

just a little beyond the point where the squelch closes

Personal

computer

with no signal (just noise). The squelch circuit has

adjustable sensitivity—the further clockwise you set

the control, the stronger the signal must be to open

the squelch. This is handy to set how strong you want

Power

Speaker

the satellite signal to be before the tape recorder turns

supply

on. Be careful not to set it too far clockwise, though,

Figure 23-8

Weather satellite receiving system

because the squelch might not open even with a strong

diagram

signal. The weather satellite receiver will allow you to

select two different channels. Channel selection is done

with switch S1. Use the selector switch to choose

channel A or B, then use potentiometer VR4 or VR5 to

NOAA-15 and pick off the AM signal that carries

“tune-in” the desired satellite frequency. The satellite

the image data. The 2400 Hz AM sub-carrier signal

receiver’s audio is fed to the speaker output at J3 and

will produce a distinctive “tick-tock” sound from

also to a low-level output at J2 which can be fed to

the speakers.

either a tape recorder or decoder card in a personal

3.

Receive the signal for as much of the satellite pass

computer.

as possible.

4.

Decode the signal into the image. (Depending on

the system, this is done in real-time or the signal is

Setting up you APT

saved to file that is decoded later.) Most new

computers (i.e. running at 800 MHz to 3 GHz with

receive station

WIN2000 or XP software) with a good sound card

can be used to decode the software directly from

In order to set up your own weather satellite receiving

the satellite receiver audio.

station you will have to acquire a few more items, as

With your 137-138 MHz turnstile or quadifillar

seen in Figure 23-8. In addition to the satellite receiver

satellite antenna connected to your weather satellite

and antenna, you will need a personal computer, some

receiver, and your WX receiver connected to your sound

sort of interface and a software package to display the

card in your PC, via a shielded audio cable, you will be

satellite picture and a satellite tracking program if

able to get stunning color images directly from weather

desired. A tracking program is not required, but it is fun

satellites.

to be able to know in advance when the satellite is

overhead.

In order to decode an APT weather satellite signal

from your WX satellite receiver, you will need to load

How to see satellite weather pictures on your

some WX decoding software into your personal

personal computer, you must follow the steps below:

computer.

1.

Track the desired satellite to find when it will appear

There are number of choices for APT satellite

and how long it will be in view (i.e. how high in

decoding software, some of which are free for the

elevation it will rise). (See NASA’s online J-Track

download, such as WXtoImg which is a fully automated

program for an example of NOAA satellite tracking.)

APT and WEFAX weather satellite (wxsat) decoder.

2.

Tune the receiver to the right frequency, e.g.

The software supports recording, decoding, editing, and

Chapter Twenty-three: Weather Satellite Receiver

137.620 MHz for NOAA-14 and 137.500 for

viewing on all versions of Windows, Linux, and

260

Chapter Twenty-three: Weather Satellite Receiver

Table 23-4

137 MHz Weather satellite receiver frequencies

Country

Satellite

Format

Frequency

USA

NOAA - 12

APT

137.500 MHz

USA

NOAA - 14

APT

137.620 MHz

USA

NOAA - 15

APT

137.500 MHz

USA

NOAA - 17

APT

137.620 MHz

USA - 2008 launch

NOAA - 18

APT

137.9125 MHz

Russia

METEOR

APT

137.300 MHz

Russia

METEOR

APT

137.400 MHz

Russia

METEOR

APT

137.850 MHz

Russia

OKEAN

APT

137.400 MHz

MacOS X. The WXtoImg software supports real-time

Additional APT weather satellite source information

decoding, map overlays, advanced color enhancements,

137 MHz quadrifillar antenna construction info:

3-D images, animations, multi-pass images, projection

http://www.askrlc.co.uk/

transformation (e.g. Mercator), text overlays, automated

137 MHz turnstile antenna construction info:

web page creation, temperature display, GPS interfacing,

http://www.qslnet.de/member/pa1pj/turnstile.pdf

and control for many weather satellite receivers,

communications receivers, and scanners. Check the

TimeStep – http://www.time-step.com

download site at: http://www.wxtoimg.com/downloads/.

Hamtronics – http://www.hamtronics.com/

Another good source for the WXSAT satellite

Ramsey Electronics –

decoding software is the HF-FAX web-site located at

http://www.ramseyelectronics.com/

http://www.hffax.de/html/hauptteil_wxsat.htm. Once

Dartcom – http://www.dartcom.co.uk

your software is loaded and your system check

completed, you can refer to the chart in Table 23-4, for

Swagur Enterprises, USA www.swagur.com

the most popular satellite frequencies.

Vanguard Electronic Labs, USA www.cyberpad.com

261

Chapter 24

Analog To Digital

Converters (ADCs)

Misc

PC board, wire,

Parts list

enclosure, terminal

strip, etc.

ADC - 1

A number of radio receiver projects in this book are

C1

.1 µF, 35 volt

based on collecting data from receivers rather than

capacitor

listening to sound coming from a radio. In this chapter

C2

10 µF, 35 volt

we will discuss four different approaches to buying

electrolytic capacitor

and/or building analog to digital converters which you

can use to collect or save data for analyzing at a later

C3

5 µF, 35 volt

time. By using an analog to digital converter, you can

electrolytic capacitor

collect, save and later playback and analyze signals that

U1

LM78L05 5 volt

were recorded over days or over weeks and then, using

regulator IC

special software, you can analyze the signals to

U2

MAX187 A/D

determine trends of specific signals. We will present

converter IC

two different A/D or analog to digital converter projects

ADC - 2

which you can build with inexpensive integrated circuits

and connect to your personal computer’s parallel port.

R1-R8

100 k ohm,

Next, we will show you how you can purchase a low cost

1/ watt, 5% resistor

4

commercial analog to digital converter with software and

C1

1 µF, 35 volt

finally we will describe a high quality A/D system which

electrolytic capacitor

is used by members of the Public Seismic Network to

C2,C5

.1 µF, 35 volt

record earthquake signals around the country. The PSN

disk capacitor

A/D converter is a true 16-bit multi-channel assembled

A/D system which connects to your personal computer’s

C3

47 µF, 35 volt

serial port. These four A/D systems are great choices for

electrolytic capacitor

collecting radio signals over an extended period of time.

C4

4.7 µF, 35 volt

Examine each of these A/D solutions and see which one

electrolytic capacitor

is best for your particular applications. Most of the A/D

D1

1N4001 silicon diode

collections systems described below come with free

software for recording data.

U1

MAX186 A/D converter

IC (Maxim

Semiconductor)

U2

LM7805 – 5 volt

ADC – 1: single channel

regulator IC

analog to digital converter

P1

DB-25 – 25-pin

parallel port

This single channel 12-bit analog to digital converter,

connector

shown in Figure 24-1, can be built with the minimum of

262

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Chapter Twenty-four: Analog To Digital Converters

A/D

U2

input

MAX187

1

8

2

7

LM98LOS

3

6

3

1

+

U1

4

5

2

+

+

C1

C2

C3

2

3

12

P1

24

25

Figure 24-1

Single channel A/D converter – ADC 1. Courtesy of Radio-Sky Publishing components and the software for it is free. The single

you could make your own circuit board for the project.

channel A/D converter is built around the $14 low cost

The circuit only utilizes capacitors, both polar and non-

MAX187 A/D converter from MAXIM Semiconductors.

polar types. Non-polarized capacitors are usually

The circuit consists of the A/D converter chip, a

smaller capacitor and sometimes they do not have their

regulator chip, and a few capacitors; it can’t get more

actual value printed on them. Often a three-digit code is

simple than this! The single channel A/D converter

used to represent their value. For example, a . 001 µF

readily connects to your computer’s parallel port

capacitor will have (102), while a .01 µF capacitor will

through a BD-25 connector. The analog input voltage

have a (103) marked on it. This project also uses large

can be from zero (0) to 4.095 volts as a maximum

polarized or electrolytic capacitors, these capacitors

signal level. A 9 volt battery or small 9 to 12 volt DC

have polarity markings on them which must be

“wall-wart” power supply can be used to power the A/D

observed if you want the circuit to work properly. Use

circuit, which can be housed in a small plastic case.

the chart in Table 24-2 to help identify the project

The A/D input from your signal source is fed to pin 2

capacitors. Identify all of the capacitors before

of the MAX187 chip. The 5 volt regulator’s output

installing them on the circuit board. Once you have

powers the MAX187 chip via pin 1. The MAX817

identified all of the capacitors, you can go ahead and

outputs to your personal computer are on pins 6, 7 and 8.

install them on the circuit board. Trim the excess

Only three capacitors are needed for this A/D, two of

component leads flush to the edge of the circuit board

which are used in the regulated power supply section of

with your end-cutters.

the circuit.

Take a quick look at the semiconductor pin-out

You will need a small 30 watt soldering iron, some

diagram shown in Figure 24-2. This diagram will help

60/40 rosin core solder for building this project. A small

you install the integrated circuits in the A/D projects.

jar of “Tip Tinner” from your local Radio Shack is used

An integrated circuit socket for this project is highly

to clean and dress the soldering tip. Locate a few small

recommended, as an insurance from a possible circuit

hand tools, including a pair of small end-cutters and a

failure if it ever happens. It is much easier to simply

needle-nose pliers and a flat-blade and Phillips

replace the IC rather than trying to un-solder the IC

screwdriver and we will begin building the A/D

from the circuit board. The IC socket will have a

converter.

cut-out or notch at one end of the package. Solder the

Heat up your soldering iron and let’s get building.

IC socket onto the PC board. Pin one (1) will be

The ADC-1 circuit can be built on a small perf-board or

assigned to the pin just to the left of the notch or cut-

direct prototyping board available at Radio Shack or

out. Pin one (1) of the IC socket is connected to the

263

ADC-1

ADC-2

1

CH0 1

20 VDD

2

19

(TO-92)

1

CH1

SCLK

(TO-92)

Plastic Package (Z)

VDD 1

8 SCLK

1

Plastic Package (Z)

CH2 3

MAXIM

18 CS

OUTPUT

INPUT

AIN

MAXIM

2

7 CS

OUTPUT

INPUT

1

CH3 4

17

MAX187

DIN

MAX186

SHDN 3

6 DOUT

MAX189

1

CH4 5

MAX188

16 SSTRB

RFF 4

5 GND

1

CH5 6

15 DOUT

DAO

DAO

00774400

1

00774400

CH6 7

14 DGND

Bottom View

Bottom View

1

CH7 8

13 AGND

MAX187

78L05

1

V

9

12 REFADJ

SS

SHDN 10

11 VREF

1

78L05

1

1

MAX186

1

1

1

1

1

1

Figure 24-2

Semiconductor pin-outs

output of the regulator U1. When inserting the IC into

shiny and bright. If any of the solder joints look dark,

its socket pay particular attention to the orientation. Pin

dull or “blobby” then remove the solder from the joint

one (1) of the IC must be inserted into pin one (1) of the

and then re-solder the joint all over again. Next, we will

IC socket. Note that there will be a notch or cut-out or

examine the PC board for possible “short” circuits

small indented circle on the top of the IC package. Pin

which are often caused by the sticky rosin residue left

one (1) of the IC will be just to the left of the cut-out

on the circuit board from the solder. Often “cut”

or notch.

components or small solder balls can adhere to the foil

One neat way to package the units is inside a two

side of the board and “short” between the circuit traces.

way parallel port manual switch box. These can be

Once you have examined the PC board carefully, you

bought for about $10 at computer shows. One of the

can go ahead and power-up the circuit for the first time.

DB25 connectors is removed from the back of the

Install the free A/D collection software, either Data

switch and replaced with a power and a analog input

Collect Lite or Radio-Sky Pipe from the Radio-Sky

jack. Leads 2, 3, 12, 24 and 25 from the removed DB25

web-site, or see Appendix, and start collecting data

are soldered directly to the appropriate places on the

from one of your new receivers. In the event the circuit

A to D board. The switch can then be used to pass

does not work, check over the installation of the

through to the printer when the A to D is not in use. You

electrolytic capacitors and the polarity of the power

could also elect to mount the A/D converter in a small

supply connections. The MAX87 chip should be

plastic box if desired with a 25 pin connector on the

available from Digi-Key Corporation, see Appendix.

rear of the enclosure.

Before applying power to the A/D circuit, take a

moment to inspect the foil side of the PC board. Pick up

ADC – 2: 8 channel analog

the PC board with the foil side of the board facing

upwards towards you. We are going to examine the PC

to digital converter

board for possible “cold” solder joints and “short”

circuits before applying power for the first time. Look

An 8 channel 12-bit analog to digital converter (ADC)

Chapter Twenty-four: Analog To Digital Converters carefully at the solder joints, they should all look clean, project is shown in Figure 24-3, and connects to the

264

Chapter Twenty-four: Analog To Digital Converters

order the MAX186 IC from Radio-Sky Publishing, or

parallel port of your personal computer. This second

from Digi-Key or Mouser Electronics, see Appendix.)

low cost analog to digital converter circuit is one you

can readily build yourself in a few hours from scratch.

The A/D circuit can be built on a small breadboard or

This A/D converter works with free software from a

on a printed circuit board. A circuit board and partial kit

company known as Radio-Sky, which specializes in

of parts (no case, connectors, or power supply) is

products for Radio Astronomy. Their free software,

available from Radio-Sky. Before we begin building the

which works with the low cost ADC, is called Radio-

single channel A/D converter you will need to secure a

Sky Pipe. The ADC is based on a single low cost

clean well lit work area. You will need to locate a small

integrated circuit from MAXIM Semiconductors. Pins 1

27 to 33 watt pencil-tipped soldering iron, a roll of

through 8 on the MAX186 A/D converted chip

60/40 rosin core solder and small jar of “Tip Tinner,” a

correspond to Channels 1 through 8. A 100 kilo-ohm

soldering iron tip cleaner/dresser. Collect together a few

resistor is placed across each input channel pin and is

small hand tools such as a pair of end-cutters, a pair of

connected to ground. The A/D converter circuit

needle-nose pliers, a flat-blade and a Phillips screw-

connects to a personal computer via the parallel port.

driver and a magnifying glass. Grab the schematic, parts

You will need to choose the appropriate parallel port

layout diagram and the resistor and capacitor

address which is selected in the free Radio-Sky Pipe

identifications charts below, and we will begin.

software. Note that all of the .1 µF (microfarad)

This project employs eight 100,000 ohm resistors at

capacitors are non-polarized types, typically disk

the input to each of the A/D channels. Take a look at the

ceramic capacitors. They should be rated for at least

resistor identification chart in Table 24-1. Each resistor

15 volts. The A/D circuit may be powered by a battery or

will have three or four color bands on the body of the

any well filtered external DC power supply. (You may

resistor, which start at one end of the resistor body.

+

7805

C2

D1

3

1

U2

+

+

+8 to 15 V DC

C1

2

C3

R1 – R4

P1

1

20

IN1

2

19

14

2

IN2

3

18

15

IN3

4

U1

17

3

IN4

5

16

IN5

MAX186

NC

6

15

IN6

7

14

IN7

8

13

IN8

9

12

10

11

NC

R5 – R8

24

+

25

C4

C5

Figure 24-3

8 channel A/D converter – ADC 2. Courtesy of Radio-Sky Publishing 265

Table 24-1

Resistor color code chart

Color Band

1st Digit

2nd Digit

Multiplier

Tolerance

Black

0

0

1

Brown

1

1

10

1%

Red

2

2

100

2%

Orange

3

3

1,000 (K)

3%

Yellow

4

4

10,000

4%

Green

5

5

100,000

Blue

6

6

1,000,000 (M)

Violet

7

7

10,000,000

Gray

8

8

100,000,000

White

9

9

1,000,000,000

Gold

0.1

5%

Silver

0.01

10%

No color

20%

The first color band will represent the first digit of the

For example, a .001 µF is labeled (102), while a .01 µF

resistor code, the second color band denotes the second

capacitor is labeled as (103). Identify all of the

digit of the code, and finally the third color code

capacitors in the ADC-2 project and separate them into

represents the resistor’s multiplier value. Resistors will

piles polarized vs. non-polarized and place them in front

generally have a tolerance code which is the fourth

of you. Once identified you can go ahead and install the

color band. The absence of a fourth color band indicates

capacitors on the PC board in their respective locations.

a 20% tolerance value, while a silver color band denotes

Pay particular attention to installing the electrolytic

a 10% tolerance and a gold band represents a 5%

capacitors correctly. Once you have placed the

tolerance resistor. A 100k ohm resistor’s first band

capacitors on the board, you can solder them in place,

should be brown (1), its second color band is black (0)

then cut the extra component leads flush to the edge of

and its third band will be yellow (0000), so (1)(0) times

the board.

(0000) = 100,000 ohms or 100k ohms. Place the eight

The analog to digital converter contains a single

resistors on the circuit board and solder them in place.

silicon diode at D1. Remember that diodes have polarity

Next, trim the excess component leads flush to the edge

and they must be mounted correctly for the circuit to

of the PC board with your end-cutters.

work. Diodes will generally have an anode and cathode

Capacitors are generally identified as polar and non-

lead, they will have a white or black band closer to one

polar types. The polarized capacitors are also called

end of the diode. The end closest to the colored band is

electrolytic capacitors and they have polarity, as each of

the cathode lead, look at the schematic or part layout

the two leads are labeled as plus (+) or minus (−) and

diagram and then install the diode.

this polarity must be observed when installing these

capacitors in order for the circuit to work correctly.

This circuit employs two integrated circuits, the main

Non-polarized capacitors are usually small in physical

A/D converter chip and a regulator chip. An integrated

size and in their actual value. Take a look at the

circuit socket for U1 is highly recommended, so in the

capacitor identifier chart in Table 24-2, it illustrates the

event of a possible IC failure, you can simply plug-in a

capacitor codes used to identify smaller sized

new chip without having to un-solder 20 pins or more

capacitors. Many times small capacitors do not have

from the foil side of the PC board. Integrated circuit

room to print their entire details on the body of the

sockets will usually have a notch or cut-out at one end

Chapter Twenty-four: Analog To Digital Converters capacitor, so a three-digit code is utilized to label them.

of the package. The pin just to the left of the notch or

266

Chapter Twenty-four: Analog To Digital Converters

Table 24-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes.

The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

1st Significant Figure

2nd Significant Figure

Multiplier

Tolerance

104 k

0.1 µF 10%

CSGNetwork.Com 6/4/92

Value

Type

Code

Value

Type

Code

1.5 pF

Ceramic

1,000 pF /.001 µF

Ceramic / Mylar

102

3.3 pF

Ceramic

1,500 pF /.0015 µF

Ceramic / Mylar

152

10 pF

Ceramic

2,000 pF /.002 µF

Ceramic / Mylar

202

15 pF

Ceramic

2,200 pF /.0022 µF

Ceramic / Mylar

222

20 pF

Ceramic

4,700 pF /.0047 µF

Ceramic / Mylar

472

30 pF

Ceramic

5,000 pF /.005 µF

Ceramic / Mylar

502

33 pF

Ceramic

5,600 pF /.0056 µF

Ceramic / Mylar

562

47 pF

Ceramic

6,800 pF /.0068 µF

Ceramic / Mylar

682

56 pF

Ceramic

.01

Ceramic / Mylar

103

68 pF

Ceramic

.015

Mylar

75 pF

Ceramic

.02

Mylar

203

82 pF

Ceramic

.022

Mylar

223

91 pF

Ceramic

.033

Mylar

333

100 pF

Ceramic

101

.047

Mylar

473

120 pF

Ceramic

121

.05

Mylar

503

130 pF

Ceramic

131

.056

Mylar

563

150 pF

Ceramic

151

.068

Mylar

683

180 pF

Ceramic

181

.1

Mylar

104

220 pF

Ceramic

221

.2

Mylar

204

330 pF

Ceramic

331

.22

Mylar

224

470 pF

Ceramic

471

.33

Mylar

334

560 pF

Ceramic

561

.47

Mylar

474

680 pF

Ceramic

681

.56

Mylar

564

750 pF

Ceramic

751

1

Mylar

105

820 pF

Ceramic

821

2

Mylar

205

267

cut-out will be designated as pin 1. Be sure to align pin

the circuit. Most common errors are installing the

one (1) of the IC socket with IN1 and pin twenty (20)

capacitor and diodes incorrectly. Also take note of the

with the output of the regulator at U2. The actual IC

IC installation if the circuit does not initially work.

itself will also have a notch or cut-out and pin one

(1) will also be just to the left of the notch. Make sure

that when you place the IC into its socket that you align

pin one (1) of the IC with pin one (1) of the socket.

ADC – 3: Dataq

Failure to observe the correct orientation of the IC will

DI-194RS/ DI-154RS

result in damage to the IC and perhaps damage to the

circuit when power is first applied.

starter kits

Once the circuit board is built, you can wire a DB-25

The Dataq DI-194RS is a low cost ready-made 10-bit

connector to the A/D chip and ground and your analog

ADC starter kit available for the low price of $24.00,

to digital converter will be just about finished. Find a

while the DI154RS is a 12-bit ADC system priced at

suitable small plastic or metal enclosure for the circuit

$39.00, see Figure 24-4. This A/D system has many

board. The 10 inputs can be wired to a 10-position

features and includes a copy of WinDaq/Lite chart

screw terminal strip or you could use the second

recorder software. This is a great budget ADC system

25 pin connector as the input connector to the circuit.

for readers who want to begin collecting data

Use whatever is convenient.

immediately. These ADCs would go well with any of

Before applying power to the circuit for the first time,

the receiver projects in this book.

you will need to inspect the circuit board for possible

“cold” solder joints and “short” circuits. Pick up the

4-Channel, 10-Bit, data acquisition

circuit board, with the foil side facing upwards towards

starter kit - DI194RS

you. Examine the solder joints carefully. Each of the

solder joints should look clean, shiny and bright. If any

4-Channel, 12-Bit, data acquisition

of the solder joints look dark, dull or “blobby”, then

starter kit - DI154RS

remove the solder from the joint and then re-solder the

joint over again so that it looks good. Next, we will

•

Compact Data Acquisition Starter Kit

inspect the board for possible “short” circuits.

•

4-Channel, 10-Bit, ±10V ADC

Many times sticky residue from the rosin core solder

•

Provided with a Serial Port Interface Cable

will cause “cut” component leads and small solder balls

to adhere to the foil side of the board, thus “shorting-

out” circuit traces. Remove anything that looks foreign.

Now you can connect the A/D circuit to the parallel

port of your computer and apply power to the circuit.

You can power the A/D converter from a small DC

“wall-wart” power supply. Install the free Radio-Sky

software and you are ready to begin collecting data.

The A/D circuit will work in the Standard version of

Radio-Sky Pipe, but only Channel 1 will be available.

The Pro-Upgrade allows you to use any number of

channels up to 8. The channels used must be

sequential. Analog inputs should be restricted to the

0 to 4.095V range.

If the circuit doesn’t work on power-up, disconnect

power and re-examine the circuit board to make sure

Chapter Twenty-four: Analog To Digital Converters that you didn’t make an error when constructing Figure 24-4

Dataq data-logger

268

Chapter Twenty-four: Analog To Digital Converters

•

Two Digital Inputs for Remote Start/Stop and

Windows environment. Their real time display can

Remote Event Marker Control

operate in a smooth scroll or triggered sweep mode of

•

Includes WinDaq/Lite Chart Recorder Software,

operation, and can be scaled into any unit of measure.

WinDaq Waveform Browser Playback and Analysis

Event markers with comments allow you to annotate

Software, and Documentation

your data acquisition session with descriptive

information as you’re recording to disk. Raise your

•

Provided Active X Controls allow you to program

productivity to new heights with WINDAQ’s unique

the DI-194 from any Windows programming

multi-tasking feature. Record waveform data to disk in

environment

the background while running any combination of

•

Kids - Get a free Data Acquisition Starter Kit for

programs in the foreground—even WINDAQ Waveform

your Science Fair Project.

Browser playback software to review and analyze the

The DI-194RS and DI-154RS, DATAQ’s four-channel

waveform data as it’s being stored! The DI-194RS

data acquisition starter kits, are a low-cost way to

Module with the WINDAQ Resource CD, screwdriver,

experience WINDAQ software, now with more features

and cable—all included with each starter kit. DI-154RS

and capabilities than ever before. With these starter kits,

module case is identical.

you can digitize virtually any transducer’s analog output

signal and record it to your PC’s hard disk. At the same

DI-194RS Starter Kit:

time, view the transducer’s output on your PCs monitor

http://www.dataq.com/products/startkit/di194rs.htm

in a triggered sweep (oscilloscope-like) or scrolling

(chart recorder-like) display format. The starter kits

DI-154RS Starter Kit:

provide a taste of the exceptional power and speed

possible with WINDAQ software. They provide 12-bit

http://www.dataq.com/products/startkit/di154rs.htm

(DI-154RS) and 10-bit (DI-194RS) measurement

accuracy, a ±10V analog measurement range, up to

ADC – 4: PSN true 16-bit

240 samples/second throughput, and four analog input

serial output analog

channels. A CD demonstrates WINDAQ Waveform

to digital converter

Browser (WWB), our playback and analysis software,

but to get a hands-on illustration of the data recording

The Public Seismic Network analog to digital board is a

and display capabilities of WINDAQ/Lite, you need a

true 16-bit analog to digital converter for serious

DI-154RS or DI-194RS starter kit. When connected to

researchers who want high speed and high accuracy and

your PC’s serial port, these starter kits allow you to

excellent resolution. This ADC is used by the Public

record, display, and analyze data using your own

Seismic Network, a group of dedicated researchers

signals. The kits ship with WINDAQ/Lite

based in California who collect earthquake events.

(Recording Software and Playback and Analysis

Many researchers world-wide use this equipment to

software). Data acquisition rates up to 240 samples per

collect data. PSN ADC’s are used to collect seismic,

second are supported for Windows 2000 and XP.

magnetic, radio and weather information. A free data

The DI-154RS and DI-194RS derive their power

collection software package is also available. The PSN

directly from the RS-232 serial port to which it is

board costs about $180, see Figure 24-5.

connected. So there are no batteries to replace or

external power supplies to connect. The DI-154RS and

True 16-bit PSN A/D board

DI-194RS starter kits are equipped with two digital

inputs for remote start/stop and remote event marker

16-Bit ADC board features:

control. Both starter kits are provided with an ActiveX

Control Library that allows you to program the starter

•

Low Cost Analog to Digital Card for Seismic and

kits from any Windows programming environment.

Other Low Frequency Data Recording

The included WINDAQ/Lite data acquisition software

•

True 16-Bit Resolution with Oversampling (more

offers real time display and disk streaming for the

information)

269

Figure 24-5

16-bit analog to digital converter

•

Standalone ADC Board with RS-232 Serial Output

•

Resolution: 16-Bit Successive Approximation

•

8 Single-Ended Analog Input Channels

•

Accuracy: 16 Bits

•

Compatible with WinSDR Datalogging Software

•

Dynamic Range: 96 dB

•

Time Accuracy < 3 Millisecond with GPS Timing

•

Input Range: ± 5 or ±10 Volts, Jumper

System

Selectable

•

Uses GPS, WWV, WWVB and Other Time

•

A/D Converter Chip: Linear Technology

References for Accurate Time Keeping

LTC1605CN

•

Low power Requirement: < 1 Watt without Timing

•

Input Impedance: 4.7k or 100k (Note 1)

Reference; < 1.5 Watts with GPS Timing

•

Sample Rates:

•

Uses Low Power High Speed PIC18F452

Microprocessor

•

200, 100, 50, 20 and 10 Samples Per Second

•

WWV Time Correction Option:

Specifications

•

Tone Detector and Bandpass Filter to Detect

800 ms Top of the Minute Tone Mark

•

Analog Inputs:

•

±20 Millisecond Time Accuracy when Locked

Chapter Twenty-four: Analog To Digital Converters

•

Channels: 8 Single-Ended Inputs

to WWV Time Signal

270

Chapter Twenty-four: Analog To Digital Converters

•

GPS Support:

(96 dB) dynamic range. The amount of oversampling

•

Supports these GPS Receivers: Garmin GPS

depends on the sample rate. The number of samples that

16/18 Sensor or the Motorola ONCORE series

are averaged together at 200 samples per second is 16

of GPS receivers

and at sample rate below 200 sps the number of samples

averaged together is 32.

•

±3 Millisecond Time Accuracy when Receiver

is Locked to GPS Time

•

Board Size:

Board differences

•

6.500 × 5.750 inches or 16.51 × 14.605

centimeters

There are two versions of this ADC board. The boards

are identical except for the Analog Input connector and

•

Power Supply Requirements:

location on the board. The board with the DB25 right

•

16 to 28 VDC or 11 to 18 VAC at 100 MA or

angle connector is for customers who only need the

more

ADC board. This version allows access to all of the

•

PSN-ADC-SERIAL Version II Board without

connectors at the edge of the board. The board

WWV Timing Circuitry and Power Supply - Cost:

with the 26 pin ribbon connector header can be

$185.00

used with the PSN-ADC-EQAMP Amplifier/Filter

board with mating 26 pin header connector. This

•

WWV Timing Option - Cost: $25.00

arrangement produces a module that can be mounted in

•

Garmin GPS 18 Timing System - Cost: $98.00

an off-the-self box.

•

Power Supply Options:

•

110 VAC 60 Hz Wall Mounted Power Supply -

Software

Cost: $10.00

•

Universal 110 VAC to 220 VAC 50 / 60 Hz

WinSDR (Download) can be used to record data using

Power Supply with one Adapter Plug - Cost:

the PSN-ADC-SERIAL Version I or II ADC boards.

$25.00

This program is included with the purchase of the

•

Six foot 9-pin Male / Female RS-232 Cable - Cost:

board. This Windows DLL Driver (pdf version) can be

$5.00

used by programmers who would like to write their own

•

Enclosures for the PSN-ADC-SERIAL Board.

data-logger program or add the A/D board to an existing

program. The DLL Driver zip file includes an example,

•

Plastic Box with Metal Front/Rear Panels - Cost:

written in VC++ 6.0, showing how to use the PSN A/D

$15.00

Board DLL file.

Box Size: L: 8.0 W: 7.8 H: 2.5 inches. This box can

be used to hold the A/D and Amp/Filter boards.

Earthworm, a powerful seismic software package that

Note: This is just the box, you will need to drill any

can run under various operating systems, can now

front/rear panel and mounting holes.

receive data using the PSN-ADC-SERIAL board or

WinSDR. See this link for more information. A device

driver for the Windows version of Seislog is now

True 16-bit performance

available. Contact me for more information.

To order a board contact Larry at: 1.650.365.7162

The Analog to Digital converter chip on the PSN-ADC-

SERIAL board has an internal noise level of ± 3 counts.

16-Bit ADC system board: http://psn.quake.net/

With the use of over-sampling, the internal noise level

serialatod.html#16-Bit%20Performance

of the chip can be averaged out to produce a true 16-bit

WinSDR software: http://psn.quake.net/winsdr/

271

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Appendix

Electronic Parts Suppliers

We have listed some electronic parts suppliers. We

Circuit Specialist Inc. - Good parts selection, test

cannot guarantee any particular level of service from

equipment, kits

these companies and supply this list only as a

220 South Country Club Drive #2

convenience to our readers.

Mesa, AZ 85210

Phone: (800) 528-1417 +1-480-464-2485

Allegro Electronic Systems - Semiconductor

http://www.cir.com/

manufacturer

3 Mine Mountain Rd. Cornwall

C & S Sales - Some kits and test equipment

Bridge, CT. 06754

Wheeling, IL 60090

Phone: 1-203-672-0123

Phone: 1-800-292-7711

http://www.allegromicro.com/

http://www.cs-sales.com/

sales@cs-sales.com

AmaSeis Seismic Software - Free seismic software

available from: Alan Jones

Dan’s Small Parts and Kits - Low tech site, but nice

www.binghamton.edu/faculty/jones/AmaSeis.html

parts selection

PO Box 3634

Amidon Associates Inc. - Toroidal cores

Missoula, Montana. 59806-3634

240 Briggs Ave

Phone: 406 258 2782

Costa Mesa, CA 92626

http://www.danssmallpartsandkits.net/

Phone: 714-850-4660 1-800-898-1883

http://www.amidoncorp.com/

DATAQ Instruments, Inc. - A/D data-loggers

Email: sales@amidoncorp.com

241 Springside Drive

Akron, OH 44333

Analog Devices Inc. - Now selling their parts to

Phone: 330-668-1444

individual semiconductors on the Internet

http://www.dataq.com/

3 Technology Way

E-mail: info@dataq.com

Norwood, MA - 02062

http://www.analog.com/

Debco Electronics Inc. - Sometimes has some good

bargains

Centerpointe Electronics, Inc. - I-F can type

4025 Edwards Road

inductors/transformers

Cincinnati, Ohio, USA, 45209

5241 Lincoln Ave. Unit #A-7

Phone: (513) 531-4499

Cypress, CA 90630

http://www.debco.com/

Email: cpcares@sbcglobal.net

http://www.cpcares.com/

273

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

Digi-Key Corporation - Extensive selection of

Fat Quarters Software - FM-1, FM-3 magnetometer

electronic parts on-line

sensors

PO Box 677

24774 Shoshonee Dr.

Thief River Falls, Minnesota 56701

Murieta, CA 92562

http://www.digikey.com/

Phone: 909-698-7950

http://www.fatquarterssoftware.com

Downeast Microwave Inc - Microwave components

and kits for amateurs

FAR Circuits - Circuit boards for many projects.

954 Rt. 519 Frenchtown

18N640 Field Court

NJ 08825 USA

Dundee, Illinois 60118

Phone: 908-996-3584 (Voice)

Phone: (847) 836-9148 Voice/Fax

http://www.downeastmicrowave.com/

http://www.farcircuits.net/

Freescale Semiconductor - Semiconductor manufacturer

Edmund Scientific Company - Science items, parts

7700 West Parmer Lane

and kits

Mailstop PL-02

101 E. Gloucester Pike

Austin, TX 78729

Barrington, New Jersey 08007

http://www.freescale.com/

Phone: 800-728-6999

http://scientificsonline.com/

Hamtronics - Radio kits and parts

65 Moul Road

Electronic Goldmine - Many unique surplus parts

Hilton, NY 14468-9535

9322 N. 94th Way

http://www.hamtronics.com/

Suite 104

Scottsdale, AZ 85258

Kits and Parts - Semiconductors and Toroids

http://www.goldmine-elec.com/

http://partsandkits.com/

Linear Technology Corporate Headquarters -

Electronix Express - Parts and kits

Manufacturer of high quality op-amps

365 Blair Road

1630 McCarthy Blvd.

Avenel, New Jersey 07001

Milpitas, CA 95035-7417

Phone: 1-800-972-2225

Phone: 408-432-1900

http://www.elexp.com/

http://www.linear.com/index.jsp

Electus Distribution - Ferrite coil formers

Loadstone Pacific - Ferrite coil formers, inductors

100 Silverwater Road, Silverwater

4769 East Wesley Drive

Sydney, Australia

Anaheim, CA 92807

http://www.electusdistribution.com.au/productResults.

Phone: 800-694-8089 714-970-0900

asp?form=CAT&CATID=34&SUBCATID=83

http://www.lodestonepacific.com/coilforms

Elenco Electronics Inc. - Radio and electronic kits

Maplin Electronics - AM Radio chip ZN414/MK484

150 Carpenter Avenue

Maplin Electronics Ltd

Wheeling, IL 60090 USA

National Distribution Center

http://www.elenco.com

Valley Road

email: sales@elenco.com

Wombwell

(847) 541-3800

Barnsley

(800) 533-2441

South Yorkshire

S73 0BS

www.maplin.co.uk

Appendix: Electronic Parts Suppliers

274

Appendix: Electronic Parts Suppliers

Maxim Integrated Circuits - IC manufacturer - great

Public Seismic Network - 16-bit Analog to Digital

documentation samples

converter

120 San Gabriel Drive

Larry Cochrane

Sunnyvale, CA 94086

http://psn.quake.net/serialatod.html

Phone: 408-737-7600

email: lcochrane@webtronicsc.oom

http://www.maxim-ic.com/

Radio Jove Project - Radio Jupiter project

Mincircuits - RF parts, MMICs, mixers, etc.

c/o Dr. James Thieman

PO Box 350166,

Code 633

Brooklyn, NY 11235 U.S.A.

NASA’s GSFC

Phone: (718) 934-4500

Greenbelt, MD 20771

http://www.mini-circuits.com/

Phone: 1-301-286-9790

Mouser Electronics - Extensive electronics

Radio Shack - The Internet version of the omnipresent

components, no minimum order

store

1000 North Main Street

Riverfront Campus World Headquarters

Mansfield, TX 76063-1514

300 Radio Shack Circle

http://www.mouser.com/

Fort Worth, TX 76102-1964

Phone: (817) 415-3700

National Semiconductor - Semiconductor manufacturer

http://www.radioshack.com/home/index.jsp

2900 Semiconductor Dr.

PO Box 58090

Radio-Sky Publishing - Amateur radio astronomy,

Santa Clara, California

parts and publications

USA 95052-8090

PMB 242

Phone: (408) 721-5000

PO Box 7063

http://www.national.com/

Ocean View, Hawaii 96737

http://www.radiosky.com/

Newark Electronics - Extensive inventory of

electronic parts

Ramsey Electronics - Electronic kit supplier

4801 North Ravenswood Avenue

590 Fishers Station Dr.

Chicago, Illinois 60640-4496

Victor, NY 14564 USA

Phone: 1-800-342-1445

Phone: 800-446-2295

http://www.newark.com/

http://www.ramseyelectronics.com/

Ocean State Electronics - AM Radio chip

RF Parts Company - Small RF parts

ZN414/MK484

435 South Pacific Street

PO Box 1458

San Marcos, California 92078

6 Industrial Drive

http://www.rfparts.com/

Westerly, RI 02891

Phone: 1-401-596-3080

RP Electronics

http://www.oselectronics.com

2060 Rosser Ave.

Burnaby B.C.

Onset Computers - HOBO Data Loggers

Canada V5C 5Y

PO Box 3450

Phone: (604) 738-6722

Pocasset, MA 02559

http://www.rpelectronics.com

Phone: 800-564-4377

www.onsetcomp.com

275

Speake & Co Limited - Manufacturer of FM1, FM-3

Vishay Intertechnology, Inc. - Dual matched

magnetometer Elvicta Estate

N-Channel FETs

Crickhowell

63 Lincoln Highway

Powys NP8 1DF

Malvern, PA 19355-2143

United Kingdom

http://www.vishay.com/

Texas Instruments Inc. - Semiconductor manufacturer

Interesting Web-sites

12500 TI Boulevard

Dallas, TX 75243-4136

Amateur Radio Relay League - Ham radio organization

Phone: 800-336-5236

225 Main Street

http://www.ti.com/

Newington, CT, 06111-1494 USA

Phone: 860-594-0200

Toko America, Inc.

email: http://www.arrl.org/

1250 Feehanville Drive

Mt. Prospect, IL 60056

ELFRAD Group - Low frequency research group

Phone: (847) 297-0070

114 Artist Ln

1-800-PIK-TOKO

Statesville, NC 28677

http://www.tokoam.com/

http://www.elfrad.com/

email: cplyler@elfrad.com

Vectronics - Radio kits

300 Industrial Park Road

Radio Waves Below 22 kHz -Interesting low frequency

Starkville, MS 39759

web-site

http://www.vectronics.com/

http://www.vlf.it/

Appendix: Electronic Parts Suppliers

276

Index

Headings in italics indicate projects. Page numbers in italics indicate illustrations.

3-terminal regulators 14, 16

AM Simple Crystal Radio (Continued)

6N2-meter Band Amateur Radio receiver 127–39

antenna 40, 44, 44

6N2 meters 137

appearance 42

antenna 138–39

coil winding 44

appearance 128

detector 41

band plan 139

diagram 41

coil winding information 135

amateur radio receiver 127–39

diagram (block) 129

bands 10

diagram (schematic) 131

Amateur Radio Relay Ligue (ARRL) 103, 128

frequency coverage (diagram) 130

Ambient Power Receiver 186–91

receiver specifications 129

antenna 188, 190

semiconductor pin-outs 136

appearance 187

single vs. dual conversion 130

diagram (schematic) module I 187

80/40 Meter Direct Conversion Receiver 94–103

diagram (schematic) module II 191

antenna 102, 102

earthquakes 191

appearance 95

grounding 188, 190

band change components 100

amplifier 9–10

band tuning range 100

amplitude modulation see AM

diagram (schematic) 96

Analog to Digital Converters (ADCs) 262–71

overload problems 102

16-bit converter 269–71

semiconductor pin-outs 99

16-bit converter (appearance) 270

tuning 102

8 channel converter 264–68

W1AW code practice sessions 103

8 channel converter diagram 265

Dataq kit (appearance) 268

Dataq kits 268–69

A

semiconductor pin-outs 264

Aircraft Band Receiver (active) 140–50

single channel converter 262–64

antenna 149

single channel converter diagram 263

appearance 142

software 271

audible communications 141–43

antennas 3, 9–10

coil winding information 147

APM-II 190–91

diagram (schematic) 144

basic long-wire 44

semiconductor pin-outs 147

capacitive hat 184

tuning 150

capacitive hat antenna 177, 179

Aircraft Band Receiver (passive) 150–52

dipole 90, 102, 114, 243, 243

antenna 151–52

Discone 126, 138

diagram (schematic) 151

dual-dipole 244

aircraft frequencies 150

ground rods 231–32

AM (amplitude) modulation 4–6

horizontal long-wire 188, 190

wave-form 6

loop 210

AM radio broadcasting 1, 2, 4, 49–51

loop antenna 211

carrier and modulation signals 51

power supply 184

diagram (block) 51

power supply schematic 185

AM radio receiver 49–58

quadrifillar 259, 259, 261

AM/Shortwave Crystal Radio 39–40, 46–48

VHF scanner 138, 149

appearance 46

VHF turnstile 259, 259, 261

diagram (block) 47

whip 126, 138, 149, 151–52

shortwave coil assembly 47

Armstrong, Edwin H. 3

AM Simple Crystal Radio 39–44

ARRL (Amateur Radio Relay Ligue) 103, 128

amplitude modulation 40

atomic clock 105–06

277

Copyright © 2008 by The McGraw-Hill Companies, Inc. Click here for terms of use.

aurora borealis 213–14

detector 41

Aurora Monitor 212–23

deviation 132

appearance 214

diagrams, reading 18–24

coil winding information 219–20

Digital Radio Mondiale (DRM) 8

control/display schematic circuit 216

digital transmission 3

control/display unit 214–15

diodes 16

semiconductor pin-outs 219

germanium 44

sensor 220

LEDs (light-emitting diodes) 14

sensor head schematic circuit 215

preparing leads 28

sensor head unit 214

silicon 14, 44

zener 14

disk capacitors 63–64

B

Doerle Receiver - 6SL7 70–71, 78–80

Barkhausen, H. 155

6SL7 tube 78

Branly, Edouard 1

diagram (schematic) 79

bugs (FM) 60, 68–69

history 78

Doerle Receiver - Original 70–78

appearance 71

C

coil winding 75, 76–77

cable 15

diagram (schematic) 72

capacitance code 25, 27

history 71

capacitors 13–16, 42

original parts 73

ceramic 13, 14–15

short-wave band frequencies 75

code chart 27

double-sideband (DSB) AM 6

disk 63–64

electrolytic 13, 15, 64

E

identification 12, 25

MKT polyester 13, 14

Earth Field Magnetometer 192–202

non-electrolytic 97

appearance 193, 200

polarization 42

connection diagram 196

polyester (greencap) 13, 14

diagram (schematic) 195

preparing leads 28

flux-gate sensor 194

trimmer 13

flux-gate sensor board 197

variable 13, 16

flux-gate sensor diagram (block) 194

variable (alternative) 22–24

magnetic fields 193

circuits

power supply schematic 201

integrated 14

semiconductor pin-outs 200

printed 34–36

earthquakes, predicting 191

Clapp Oscillator see Colpitts oscillator

Eckersley, Smith, Tremellen 156

coils 44 see also inductors

electret microphone 15

soldering to the pins 32

electric cables 18

color code chart 26

electromagnetism 1–4

Colpitts oscillator 19

electronic components 12–24, 13, 14, 15

circuit 20

installation 25–38

Conrad, Frank 50

preparing leads 25, 26, 28, 29

converters, analog to digital 262–71

ELFRAD group 225, 232

cristal oscillator 20

extremely low frequency (ELF) see ELFRAD

circuit 21

pictorial diagram 21

Cristal radio projects 39–48

F

AM/Shortwave Crystal Radio 39–40

Faraday, Michael 1

AM Simple Crystal Radio 39

ferrite bead (slug) 17

FM Crystal Radio 39

Fessenden, Reginald 50

cycles per second see Hertz

FET see transistors

firefighters VHF 117

flux 29, 30

D

FM broadcast receiver 59–69

Daily, William 190–91

FM Crystal Radio 39, 45–46

dawn chorus 156

appearance 45

de-solder 36–37

circuit 45

Index

278

Index

FM (frequency modulation) 6–7, 61

ionospheric disturbance receiver 203–11

radios 3

wave-form 7

FM radio 3

J

Frazier, John 2

Jupiter 234, 235

frequence modulation see FM

Jupiter Radio Telescope 233–45

frequencies (spectrum) 2, 4

antenna 243–44, 243, 244

frequency drift 61

appearance 235

diagram (block) 236

diagram (schematic) 238

G

planet 234, 235

galena crystal 41, 44

radio storms 244–45

geophysical alerts 115

semiconductor pin-outs 241

GPS (Global Positioning System) 3, 115

greencaps 13, 14

grounding 188, 190

L

LDR (light-dependent resistor) 13, 13

leads, preparing 25

H

LEDs (light-emitting diodes) 14, 16–17

Ham Radio licence 9, 103, 128

power indicator light 125–26

Hartley oscillator 19, 19

licenses 9, 103, 128

headphones 44

US amateur radio bands 10

health and safety 38

light-dependent resistor (LDR) 13, 13

heatsinks 15, 16

light-emitting diodes see LEDs

Henry, Joseph 1

lightning 176–77, 177

Hertz, Heinrich 1

Lightning Storm Monitor 175–85

High Frequency (HF) bands 4

antenna 177, 179, 184

history, radio 1–3

diagram (schematic) 178

lightning 176–77, 177

semiconductor pin-outs 183

I

listening-in

IC (integrated circuits) 16

aircraft communication 141–43

3-terminal regulators 16

public service VHF 117

IC Shortwave Radio Receiver 81–93

loop antenna 210, 211

appearance 82

loudspeakers 15, 17

diagram (block) 83

diagram (schematic) 84

M

evening broadcast listings 92–93

frequency range selection 89

magnetic

popular shortwave bands 91

fields 193

semiconductor pin-outs 88

induction 166

shortwave antennas 90–91

storms 213–14

shortwave listening (SWL) 82–83,

magnetometers 193

91–93

Marconi, Guglielmo 2

Induction Loop Receiving System 165–74

marine storm warnings 115

appearance 169

marine VHF 117

coil winding information 171

Maxwell, James Clerk 1

diagram (block) 167

McClelland, R.S. 2

induction loop technology 166

medium wave (MV) see AM

receiver 168–74

microphones 15, 17

receiver schematic 170

MKT capacitor 13, 14

semiconductor pin-outs 173

MOSFETs see transistors

transmitter 167–68

transmitter I schematic 167

transmitter II schematic 168

N

use 173–74

narrow-band FM transmission 60–61

induction loop technology 166

National Institute of Standards and Technology (NIST)

inductors (coils) 15, 16–17

105–06

integrated circuits (IC) 14, 16

Natural Radio see whistlers

preparing leads 29

NPN see transistors

279

soldering 25, 29–38

O

check list soldering 34

check list un-soldering 37

ohm (Ω) 12

flux 29

OMEGA Navigation System 106, 115

guns 30, 31–32

oscillation 3

irons 30–31, 37

oscillators 9–10, 18–24

joint quality 35, 36

mechanical joints 33–34, 33, 34

P

overheating 32

preparation (iron) 32

parts suppliers 272–75

preparation (material) 32–33

PNP see transistors

printed circuit (PC) boards 34–36

police VHF 117

remove solder 36–37

potentiometer (pot) 12–13, 13

solder 30, 33

power indicator LED 125–26

station 31, 31

power transistors 14, 16

temperature 33

printed circuit (PC) boards 34–36

trimming leads 36

public service VHF 116–26, 126

ventilation 38

to wire 32–33

wire gauges 33

R

Solid-state FM Broadcast Receiver 59–69

radar frequency band 1

diagram (block) 61

radio frequency (RF) spectrum 1, 3–4

diagram (schematic) 62

chart 5

inductor coil winding information 66

radio storms (Jupiter) 244–45

semiconductor pin-outs 66

radio telescope 233–45

speakers 15, 17

radio waves 4, 6, 7

SSB technology 2–3

railroad VHF 117

modulation 7–8

receivers 9–10

wave-form 8

diagrams 11

Storey, L.R.O. 156

relays 15, 17

storms, electrical 176–77

resistors 12–13, 13, 42

sub-carriers 69

codes 25

Sudden Ionospheric Disturbance Receiver 203–11

color code chart 26

antenna 210, 211

light-dependent 13, 13

appearance 205

preparing leads 26

diagram (schematic) 205

tolerance 12

power supply schematic 210

variable 12

semiconductor pin-outs 209

Rosenberg, Leo 2

short wave fadeout 204

rosin flux 30

use 211

VLF signal propagation 204–05

Super High Frequency (SHF) 4

S

switches 17–18

satellite navigation see GPS

electronic 16

schematics, electronic 18–24

slider 15

seismic network, public (PSN) 232

semiconductors 16 see also capacitors; diodes; resistors; transistors

T

substitution 18

Tate, Joseph 186, 190–91

SHF (Super High Frequency) 4

temperature (soldering) 33, 35

shortwave

Thomas, William 2

bands 1, 91

thunderstorms 176–77

broadcast chart 9, 92–93

time code receiver 104–15

fadeout 204

tinning 33, 34, 41

shortwave listening (SWL) 8–9, 82–83, 91–93

tools and supply 41

shortwave radio 8

hexagonal plastic tool 67–68

receiver 81–93

transformers 15

silicon diodes 14

transistorized radio 3

single-sideband see SSB

transistors 16

sniffer coil 258

FET 14

Index solder 30, 33

MOSFET 14

280

Index

transistors (Continued)

VLF (Very Low Frequency) 4

NPN 14

VLF Very Low Frequency Radio Receiver 153–64

PNP 14

appearance 157

power transistors 14

dawn chorus 156

preparing leads 28

diagram (schematic) 158

TRF AM Radio Receiver 49–58

recording 164

appearance 52

semiconductor pin-outs 161

diagram (block) 52

times of listening 164

diagram (schematic) 53

using the receiver 162–63

semiconductor pin-outs 56

VLF radio stations 163

trimpot see potentiometer (pot)

whistlers 154–56

tube #19 71–73

voltage controlled oscillator see VCO

volume control see potentiometer (pot)

U

UHF (Ultra High Frequency) 4

W

ultra-low frequency spectrum 225

W1AW on air code practice sessions 103

Ultra-Low Frequency (ULF) Receiver 224–32

Weather Satellite Receiver 246–61

antenna 231–32

antenna 259, 259, 261

antenna circuit 231

appearance 250

appearance 225

coil winding information 254, 256, 258

diagram I (schematic) 226

diagram (block) 250

diagram II (schematic) 227

diagram (schematic) 252

ELFRAD group 225, 232

frequencies 261

power supply schematic 227

operation 259–60

semiconductor pin-outs 231

satellite view (USA) 248

ULF-spectrum 225

semiconductor pin-outs 256

un-solder 36–37

set-up 260–61

check list 37

set-up diagram (block) 260

weather VHF 117

whistler receiver 156–64

V

whistlers 154–56

Variable Frequency Oscillator (VFO) see VFO

wide-band FM transmission 60–61

VCO (Voltage Controlled Oscillator) 22–24, 23

wire 15, 18

circuit 23

soldering to 32–33

pictorial diagram 24

WWV broadcast schedule 115

ventilation 38

WWV Time Code Receiver 104–16

Very High Frequency see VHF

antenna 114, 114

Very Low Frequency see VLF

appearance (inside) 106

VFO (Variable Frequency Oscillator) 22

appearance (outside) 105

circuit 22

atomic clock 105–06

pictorial diagram 23

coil winding information 112

VHF Public Service Receiver 116–26

diagram (block) 107

antenna 126

diagram (schematic) 108

appearance 117

LED power indicator 113

coil winding information 123

NIST (Nat.Inst.Standards and Technology) 106

diagram (block) 118

semiconductor pin-outs 112

diagram (schematic) 119

WWV broadcast schedule 115

power LED 125

semiconductor pin-outs 123

VHF public service frequency bands 126

Z

VHF (Very High Frequency) 1, 4

zener diodes 14, 64

281

Table of Contents

Chapter 1

Chapter One: Radio Background and History

Chapter One: Radio Background and History

Chapter One: Radio Background and History

Chapter One: Radio Background and History

Chapter One: Radio Background and History

Chapter 2

Chapter Two: Identifying Components

Chapter Two: Identifying Components

Chapter Two: Identifying Components

Chapter Two: Identifying Components

Chapter Two: Identifying Components

Chapter Two: Identifying Components

Chapter Two: Identifying Components

Chapter Two: Identifying Components

Chapter 3

Chapter Three: Electronic Parts Installation

Chapter Three: Electronic Parts Installation

Chapter Three: Electronic Parts Installation

Chapter Three: Electronic Parts Installation

Chapter Three: Electronic Parts Installation

Chapter Three: Electronic Parts Installation

Chapter Three: Electronic Parts Installation

Chapter Three: Electronic Parts Installation

Chapter Three: Electronic Parts Installation

Chapter 4

Chapter 5

Chapter Five: TRF AM Radio Receiver

Chapter Five: TRF AM Radio Receiver

Chapter Five: TRF AM Radio Receiver

Chapter Five: TRF AM Radio Receiver

Chapter Five: TRF AM Radio Receiver

Chapter Five: TRF AM Radio Receiver

Chapter Five: TRF AM Radio Receiver

Chapter 6

Chapter Six: Solid-State FM Broadcast Receiver

Chapter Six: Solid-State FM Broadcast Receiver

Chapter Six: Solid-State FM Broadcast Receiver

Chapter Six: Solid-State FM Broadcast Receiver

Chapter Six: Solid-State FM Broadcast Receiver

Chapter Six: Solid-State FM Broadcast Receiver

Chapter 7

Chapter Seven: Super-Regenerative Radio Receiver

Chapter Seven: Super-Regenerative Radio Receiver

Chapter Seven: Super-Regenerative Radio Receiver

Chapter Seven: Super-Regenerative Radio Receiver

Chapter Seven: Super-Regenerative Radio Receiver

Chapter Seven: Super-Regenerative Radio Receiver

Chapter 8

Chapter Eight: IC

Chapter Eight: IC

Chapter Eight: IC

Chapter Eight: IC

Chapter Eight: IC

Chapter Eight: IC

Chapter Eight: IC

Chapter 9

Chapter 10

Chapter 11

Chapter Eleven: VHF Public Service Monitor

Chapter Eleven: VHF Public Service Monitor

Chapter Eleven: VHF Public Service Monitor

Chapter Eleven: VHF Public Service Monitor

Chapter Eleven: VHF Public Service Monitor

Chapter Eleven: VHF Public Service Monitor

Chapter 12

Chapter Twelve: 6

Chapter Twelve: 6

Chapter Twelve: 6

Chapter Twelve: 6

Chapter Twelve: 6

Chapter 13

Chapter Thirteen: Aircraft Band Receivers

Chapter Thirteen: Aircraft Band Receivers

Chapter Thirteen: Aircraft Band Receivers

Chapter Thirteen: Aircraft Band Receivers

Chapter Thirteen: Aircraft Band Receivers

Chapter Thirteen: Aircraft Band Receivers

Chapter 14

Chapter Fourteen: VLF Radio Receiver

Chapter Fourteen: VLF Radio Receiver

Chapter Fourteen: VLF Radio Receiver

Chapter Fourteen: VLF Radio Receiver

Chapter Fourteen: VLF Radio Receiver

Chapter 15

Chapter Fifteen: Induction Loop Receiving System

Chapter Fifteen: Induction Loop Receiving System

Chapter Fifteen: Induction Loop Receiving System

Chapter Fifteen: Induction Loop Receiving System

Chapter Fifteen: Induction Loop Receiving System

Chapter 16

Chapter Sixteen:

Chapter Sixteen:

Chapter Sixteen:

Chapter Sixteen:

Chapter Sixteen:

Chapter Sixteen:

Chapter Sixteen:

Chapter 17

Chapter Seventeen: Ambient Power Receiver

Chapter Seventeen: Ambient Power Receiver

Chapter Seventeen: Ambient Power Receiver

Chapter 18

Chapter Eighteen: Earth Field Magnetometer Project

Chapter Eighteen: Earth Field Magnetometer Project

Chapter Eighteen: Earth Field Magnetometer Project

Chapter Eighteen: Earth Field Magnetometer Project

Chapter Eighteen: Earth Field Magnetometer Project

Chapter 19

Chapter Nineteen:

Chapter Nineteen:

Chapter Nineteen:

Chapter Nineteen:

Chapter Nineteen:

Chapter Nineteen:

Chapter 20

Chapter Twenty:

Chapter Twenty:

Chapter Twenty:

Chapter Twenty:

Chapter Twenty:

Chapter Twenty:

Chapter Twenty:

Chapter 21

Chapter 22

Chapter Twenty-two: Jupiter Radio Telescope Receiver

Chapter Twenty-two: Jupiter Radio Telescope Receiver

Chapter Twenty-two: Jupiter Radio Telescope Receiver

Chapter Twenty-two: Jupiter Radio Telescope Receiver

Chapter Twenty-two: Jupiter Radio Telescope Receiver

Chapter Twenty-two: Jupiter Radio Telescope Receiver

Chapter Twenty-two: Jupiter Radio Telescope Receiver

Chapter 23

Chapter Twenty-three: Weather Satellite Receiver

Chapter Twenty-three: Weather Satellite Receiver

Chapter Twenty-three: Weather Satellite Receiver

Chapter Twenty-three: Weather Satellite Receiver

Chapter Twenty-three: Weather Satellite Receiver

Chapter Twenty-three: Weather Satellite Receiver

Chapter Twenty-three: Weather Satellite Receiver

Chapter Twenty-three: Weather Satellite Receiver

Chapter 24

Chapter Twenty-four: Analog To Digital Converters

Chapter Twenty-four: Analog To Digital Converters

Chapter Twenty-four: Analog To Digital Converters