01A03 Elementary Electronics 1967 03 04

HowTo

ELEMENTARY UA SÑÓTS

EL MARCH -APRIL 75C

PROJECTS FOR p RAINY DAY

$925 Line Failure e Alarm

$699 project Powe r Pack

Electronic Foot Stomper

$349 Electr

design notes

for a

HAM

CONTROL

CENTER

THE INSIDE

STORY ON

DETECTORS: AMIFMIVIDEO

FLIP- FLOPS-

THE TWO -CYLINDER ENGINES OF ELECTRONICS

By the Editors of RADIO -TV EXPERIMENTER

Add

TALK

POWER

to CB and

Ham rigs

iCr

Introducing EICO's New "Cortina Series "!

Today's electro- technology makes possible near -perfect

stereo at moderate manufacturing cost: that's the de-

sign concept behind the new EICO "Cortina" all solid -

state stereo components. All are 100% professional,

conveniently compact (31/8 "H, 12"W, 8 "D), in an

esthetically striking "low silhouette." Yes, you can pay

more for high quality stereo. But now there's no need

to. The refinements will be marginal and probably

inaudible. Each is $89.95 kit, $119.95 wired.

Model 3070 All- Silicon Solid -State 70 -Watt Stereo

Amplifier: Distortionless, natural sound with unre-

stricted bass and perfect transient response (no inter -

stage or output transformers); complete input, filter

and control facilities; failure -proof rugged all -silicon

transistor circuitry.

Model 3200 Solid -State FM /MPX Automatic Stereo

Tuner: Driftless, noiseless performance; 2.4µV for 30db

quieting; RF, IF, MX are pre -wired and pre -tuned on

printed circuit boards - you wire only non -critical power

supply.

7 New Ways to make Electronics more Fun!

Save up to 50% with EICO Kits and Wired Equipment.

!`

You hear all the action -packed capitals of the

world with the NEW EICO 711 "Space Ranger"

4 -Band Short Wave Communications Receiver -

plus ham operators, ship -to- shore, aircraft,

Coast Guard, and the full AM band. 550KC to

30MC In four bands. Selective, sensitive super -

het, modern printed circuit board construction.

Easy, -fast pinpoint tuning: Illuminated slide.

rule dials, logging scale; "S" meter, electrical

bandspread tuning, variable BFO for CW and

SSB reception, automatic noise limiter. 4"

speaker. Headphone jack. KIt 949.95. Wired

$69.95.

t

More "ham" for your dollar than ever - with

the one and only SSB /AM /CW 3 -Band Trans-

ceiver Kit, new Model 753 - "the best ham

transceiver buy for 1966" - Radio TV Experi-

menter Magazine. 200 watts PEP on 80, 40 and

20 meters. Receiver offset tuning, built -in VOX,

high level dynamic ALC, silicon solid -state VFO.

Unequaled performance, features and appear.

ance. Sensationally priced at $199.95 kit,

$299.95 wired.

Model 460 Wideband Direct- Coupled

5" Oscilloscope. DC -4.5mc for color

and B8W TV service and lab use. Push.

pull DC vertical amp., bal. or unbal.

snout. Automatic suer 'miter and amp.

$109.95 kit, $149.95 wired.

NEW EICO 888 Solid -State

Engine Analyzer

Now you can tune -up, trouble-

shoot and test your own car or

boat.

Keep your car or boat engine in

tip -top shape with this completely

portable, self- contained, self -

powered universal engine ana-

lyzer. Completely tests your total

ignition /electrical system. The

first time you use it - just to tune

for peak performance - it'll have

paid for itself. (No tune -up

charges, better gas consumption,

longer wear) 7 instruments in

one, the EICO 888 does all these

for 6V and 12V systems; 4, 6 &

8 cylinder engines.

The EICO 888 comes complete

with a comprehensive Tune -up

and Trouble- shooting Manual in-

cluding RPM and Dwell angle for

over 40 models of American and

Foreign cars. The Model 888 is

an outstanding value at $44.95

kit, $59.95 wired.

FREE 1967 CATALOG

EICO Electronic Instrument Co., Inc.

131 -01 39th Ave., Flushing, N. Y. 11352

Send me FREE catalog describing the tug EICO line of

200 best buys, and name of nearest dealer: I'm inter-

ested in:

D test equipment D ham radio

New EICOCRAFT'' easy -

to -build solid -state elec-

tronic TruKits: 4 great

for beginners and

sophisticates alike. As

professional as the

standard EICO line -

only the complexity Is

reduced to make kit.

building faster, easier,

lower cost. Features:

pre -drilled copper -

plated etched printed

circuit boards; finest parts; step -by -step in-

structions; no technical experience needed -

just soldering iron and pliers. Choose from: Fire

Alarm; Intercom; Burglar Alarm; Light Flasher;

"Mystifier "; Siren; Code Oscillator; Metronome;

Tremolo; Audio Power Amplifier; AC Power Sup-

ply. From $2.50 per kit.

There's more PUNCH in the new EICO "Sentinel.

Pro" 23- channel Dual Conversion 5 -watt CB

Transceiver. New advanced Big -Reach "Range

Plus" circuitry lengthens "talk- power" reach.

Automatic noise limiter super. sensitizes for weak

signals. "Finger Tip" antenna loading and trans-

mitter tuning controls. 23 crystal -controlled

transmit and receive channels - all crystals

supplied. Rear -illuminated S /RF meter. Tran-

sistorized 12VDC and 117VAC dual power supply.

Wired only, $169.95. Positive- Negative Ground/

Mobile Marine Modification kit (optional $5.95).

D stereo /hi -fi D Citizens Band radio

automotive electronics

Name

Address

City

State Zip

l J

Model 232 Peak -to -Peak VTVM. A must

for color or 88W TV and Industrial

use. 7 non -skip ranges on all 4 func-

tions. With exclusive UniProbe.W

$29.95 kit, $49.95 wired.

4,

Let I.C.S. equip

you for success

in radio-TV-

electronics

with professional equipment!

Brand -new "Electronic Laboratory," now

being offered for the first time, can help you

land in this big money- making field -FAST!

Here's an opportunity for you to turn spare time

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a field where the rewards have never been greater.

And you don't need previous experience to do it!

International Correspondence Schools has just

developed a new I. C. S. Electronic Laboratory you

can construct in your own home. Includes series of

training kits, plus the new I.C.S. VTVM -the pro-

fessional quality vacuum tube voltmeter shown

here. With it comes complete course instruction

combining all the fundamentals with practical

knowledge you can apply at once. And best of all,

you build your own professional test instrument!

I.C.S. instruction gets you going

with equipment you can really use!

A famous manufacturer of nationally known elec-

tronic testing equipment worked closely with

I.C. S. to develop the Electronic Laboratory and

the VTVM itself. Everything you get is geared to

increase your skill and knowledge step by step.

Until finally, you've completed a precision testing

unit you can use for practically any kind of experi-

mentation, design or servicing work.

Here's how I. C. S. instruction works. You begin

with basic study lessons. Texts are clearly worded

and easy to follow. At the same time, you "act

out" what you learn with simple experiments.

Then, in 3 easy stages, you assemble your own

precision testing unit. Throughout, your instructor

gives you expert, professional help. You learn at

home, in spare time, as fast as ability permits.

Coupon brings full details on your

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Make up your mind right now to find out how

I. C. S. training in Radio -TV- Electronics can pay

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sets, hi -fis, computers, automation systems and a

host of other space -age devices. Clip and mail

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Coupon brings 3 valuable FREE booklets.

MAIL IT TODAY!

INTERNATIONAL CORRESPONDENCE SCHOOLS I

II.

Dept. 34974A, Scranton, Penna. 18515 (In Hawaii: P.O. Box 418, Honolulu. In Canada: I.C.S. Canadian, Ltd.

in other countries: I.C.S. World, Ltd.)

Please rush me your new 64 -page booklet "ElectroniCS" which answers the most often- asked,guestions about preparing for an electronics

career. Also send me "How to Succeed," and a sample I.C.S. lesson. I have indicated my field of interest below.

Electronic Fundamentals Hi -Fi /Stereo & Sound Electronic Principles for Industrial Electronics Industrial Electronics

Electronic Instrumentation Systems Automation Engineering Telephony

Computer Fundamentals General Electronics Semiconductor- FCC Radiotelephone E Other (please specify)

Radio -TV Servicing Electronics Technician Transistor Circuits Licenses

Name Age

Address

City State Zip Code

Occupation Employed by

Working Hours A.M. te P.M. Convenient payment plan

I am a member of U.S. Armed Forces. Send me facts about special low rates.

Training Programs for Industry

J

MARCH- APRIL, 1967 1

ELEMENTARY "' " " " "R ,

ELECTRONICS

THEORY

* 29 Flip -Flops -The Two -cylinder Engines of Elec-

tronics

37 Those Electronic Diagrams

55 SSB Is In!

* 81 The Inside Story on Detectors

97 Power in Watts

CONSTRUCTION

- 43 Ham Shack with a Heart

' 49 Transmitter Speech Processor

* 61 Power Pack: Experimenter's Six or Niner

66 50¢ Transistor Tester

* 71 Line Failure Alarm

* 93 Electronic Foot Stomper

95 Tenna Blitz

FEATURES

16 Tips from a Technician's Notebook

28 Wide World of Electronics

46 Great Day for QSL

47 Lafayette RK -840 Stereo Tape Recorder

64 Space -age Showcase

' 68 Space Shots: Countdown for DX

79 Low Down on Way Down QSL

80 Arecibo Listening

DEPARTMENTS

NOW THERE ARE 138 RADIO

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ARIZONA - Phoenix

ARKANSAS - Little Rock

CALIFORNIA - Anaheim,

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Los Angeles, Mission Hills,

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Reseda, Sacramento, San

Bruno, San Diego, San

Francisco, Santa Ana, Santa

Monica, Torrance, West

Covina

COLORADO - Denver

CONNECTICUT- Hamden,

Manchester, New Britain, New

Haven, New London, Orange,

Stamford, West Hartford

FLORIDA - Orlando

GEORGIA - Atlanta

ILLINOIS - Chicago

KANSAS - Wichita

LOUISIANA - New Orleans

MAINE- Portland

MARYLAND - Langley Park

MASSACHUSETTS - Boston,

Braintree, Brockton, Brookline,

Cambridge, Dedham,

Framingham, Lowell, Medford,

Natick, Quincy, Saugus,

Springfield, Waltham, West

Springfield, Worcester

MICHIGAN - Detroit

MINNESOTA- Minneapolis,

St. Paul

MISSOURI - Kansas City, St.

Joseph, St. Louis

NEBRASKA - Omaha

NEW HAMPSHIRE -

Manchester

NEW JERSEY- Pennsauken

NEW MEXICO - Albuquerque

6 Newscan -Electronics in the News

18 Ask Me Another

24 e/e Etymology

25 En Passant -Chess Column

67 Imagineering

74 Home -Study Bluebook

75 FCCQ &A

108 Literature Library

' Cover Highlights

AUTHORS IN THIS ISSUE:

Len Buckwalter- K1ODH /KBA4480, John W.

Collins, James A. Fred, Herb Friedman -

W2ZLF/KB19457, Webb Garrison, Carl L.

Henry, Steve Karlsen, Tom Kneitel- K2AES/

KBG4303, Walter R. Levins, A.A. Mangieri,

Francois Markett, Howard S. Pyle -W70E,

Leo G. Sands- W7PH /KBG7906, E. Norbert

Smith- W5MQL, and the ELEMENTARY

ELECTRONICS' Editorial Staff.

Cover Photo by Leonard Heicklen

2

AAA

"ELEMENTARY o.,

EIECrAONICs

4AAM,'OiY

,4Mip Powx PveM

NEW YORK - Albany,

Binghamton, Buffalo, New

York, Schenectady, Syracuse

OHIO - Cincinnati, Cleveland

OKLAHOMA - Oklahoma City,

Tulsa

OREGON - Portland

PENNSYLVANIA -

Philadelphia, Pittsburgh

RHODE ISLAND - Providence,

East Providence

TENNESSEE - Chattanooga,

Memphis, Nashville

TEXAS - Abilene, Arlington,

Austin, Brownsville, Corpus

Christi, Dallas, Fort Worth,

Houston, Lubbock, Midland,

San Antonio, Sherman, Waco

UTAH -Salt Lake City

VIRGINIA - Arlington, Virginia

Beach

WASHINGTON - Everett,

Seattle

ELEMENTARY ELECTRONICS

RADIO

SHACK

SPECIAL GET - ACQUAINTED OFFER

FROM THE COUNTRY'S LEADING

PARTS 01 TRIBUT I ; I

1,000 OHMS /VOLT

POCKET AC /DC VOM

Measures o Mere 31/2" x 21/4" x 1"

Thumb -Set Zero Adjustment

With Test Leads and Battery

Lowest price ever! 2 -color scale;:

5 ranges. AC /DC volts: 0 -1000

in 3 ranges; 0 -150 ma DC; 0-

100 KU. 22 -4027.

HOBBYIST'S ONE TUBE RADIO KIT

Tunes AM Band

from 540 -1600 KC

Hi -Q Coil for

Top Sensitivity

2- TRANSISTOR AM RADIO KIT

With Crystal Earphone

Solid State Circuitry

Ideal for Beginners or

Do- lt- Yourselfers

28-001 3 49

Fun to use; easy enough for anyone to build.

ß8-002 398

Fine reception across the entire broadcast band!

WIRELESS MIKE /TRANSMITTER KIT

Broadcasts into Any

AM Radio at Ranges up

to 20 Feet!

28-003

Use as room -to -room intercom or "baby- sitter"!

298

SAVE $100

MARCH -APRIL, 1967

Your Choice of

Either $2 Book

at Half Price!

50 easy -to -build

solid state

projects ...

from a simple

radio to a 2 -way

intercom system.

Each book entirely

different: Book 1,

62 -1050; Book 2,

slightly more

advanced, 62 -2025

ELECTRONIC ORGAN KIT

Better than 1 Octave

Range! Easy to Play!

A Family Favorite!

28 -004

Play songs on an organ you built yourself!

5 95

FILL OUT COUPON AND MAIL TODAY TO:

L.

RADIO East: 730 Commonwealth Ave., Boston, Mass. 02215

SHACK West: 1515 So. University Dr., Ft. Worth, Tex. 76107

Please rush me the item I've checked below.

I enclose $ , plus 500 for postage and handling:

VOM, 22- 4027 Organ, 28.004

I -Tube Radio, 28 -001 Book # I, 62 -1050

2- Trans. Radio, 28-002 Book #2, 62 -2025

Wireless Mike, 28 -003 Please send me a FREE 1967 Rodio Shack Catalog

Name (print)

Street

City

State Zip EE -367 ..a

3

Now there's a full line of

Soldering Tools

for all soldering needs

Each model outperforms any other soldering

tool of comparable size and price. All have

replaceable tips of solid copper, instant heat,

long reach, and rugged construction that

means long -life, dependable performance.

Weller Dual Heat Guns

Feature trigger -controlled dual

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light. Available in three wattage

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Weller MARKSMAN Irons

Best for intricate soldering or con-

tinuous -duty operation. Five sizes

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fLfMFN(gqY

ELECTNONICS

MARCH /APRIL 1967 Vol. 4 No. 1

Dedicated to America's Electronics Experimenters

JULIAN M. SIENKIEWICZ

WA2CQL/KMD4313

RICHARD A. FLANAGAN

ELMER C. CARLSON

KOD1752

Editor

Managing Editor

Technical Editor

JIM MEDLER Art Editor

HELEN PARKER Editorial Assistant

ANTHONY MACCARRONE Art Director

EUGENE F. LANDINO Associate Art Director

IRVING BERNSTEIN Cover Art Director

BARBARA GABRIEL Art Associate

JIM CAPPELLO Advertising Manager

LEONARD F. PINTO Production Director

CARL BARTEE Production Dianager

HELEN GOODSTEIN Assistant Production Manager

DAVID COHN

WILFRED M. BROWN

Promotion Director

Kit Division Manager

JOSEPH DAFFRON Group Executive Editor

President and Publisher

B. G. DAVIS

Executive Vice President and Assistant Publisher

JOEL DAVIS

Vice President and Editorial Director

HERB LEAVY, KMD4529

rs

ELEMENTARY ELECTRONICS, Vol. 4, No. 1 is published bi- monthly

by SCIENCE & MECHANICS PUBLISHING CO., a subsidiary of

Davis Publications, Inc. Editorial, business and subscription offices:

505 Park Ave., New York, N. Y. 10022. One -year subscription Isis

issuesl- $4.00; two -year subscription 112 issuesl- $7.00; and three -

year subscription 118 issuesl -$10.00. Add $1.00 per year for postage

outside the U.S.A. and Canada. Advertising offices: New York, 505

Park Ave., 212 -PL -2 -6200; Chicago: 520 N. Michigan Ave., 312-527-

0330; Los Angeles: 6253 Hollywood Blvd., 213 - 463 -5143; Atlanta: Pirnie

& Brown, 3108 Piedmont Rd., N.E., 404 -233 -6729; Long Island: Len Osten,

9 Garden Street, Great Neck, N. Y., 516. 487.3305; Southwestern ad-

vertising representative: Jim Wright, 4 N. Eight St., St. Louis, CH.1 -1965.

EDITORIAL CONTRIBUTIONS must be accompanied by return postage

and will be handled with reasonable core; however, publisher assumes

no responsibliity for return or safety of manuscripts, art work, or

photographs. All contributions should be addressed to the Editor,

ELEMENTARY ELECTRONICS, 505 Park Avenue, New York, N. Y. 10022.

Second -class postage paid at New York, New York and at additional

ELEMENTARY ELECTRONICS

vi?

A

Want a high -pay career in Electronics?

This

free book

may change

your life

It tells how to go about getting the key

to job success in the growing electronics

boom -a Government FCC License

THERE'S A BIG BOOM IN ELECTRONICS. And YOU can

he part of it. You don't need a college education or

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shown here tells you how.

In the last 15 years, the electronics manufacturing

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more than a million two -way mobile radio systems in

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entists developing and testing such electronics miracles

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hearing aids, rocket guidance and control systems.

Regardless of which you choose, the secret of "getting

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that you have passed a standard Federal exam on the

fundamentals of electronics - that you're not just an

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legally require it.

Now, because of the importance of getting your FCC

License, Cleveland Institute of Electronics has prepared

a valuable 24 -page book telling you how to go about it.

ENROLL UNDER NEW G.I. BILL

AU CIE courses are available under the new G.I. Bill.

If you served on active duty since January 31, 1955,

OR are in service now, check box in coupon for G.I.

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MARCH- APRIL, 1967

You will find out why the Commercial FCC License is

often called the "passport to success." You'll see how

and why the Government issues these licenses. You'll

learn how you can get your license ... and qualify for

top opportunities in Electronics.

With this book, you will receive a second free book,

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FCC Licenses, even though 2 out of 3 without this

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To receive both books without cost or obligation,

just mail the coupon below. If coupon has been removed,

write to: Cleveland Institute of Electronics, 1776 East

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it now -it may change your whole life.

r 1

MAIL COUPON FOR 2 FREE BOOKS

C.' Cleveland Institute of Electronics

E 1776 East 17th Street, Cleveland, Ohio 44114

Please send me, without cost or obligation, your 24 -page book,

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preparation courses.

Name (please print)

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Occupation Age

Check here for G.I. Bill information.

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5

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NEW MODEL

6

EWSCA

Laser TV

Scientists have developed an experimental TV

picture system using a laser beam scanned by

ultrasonic waves. The system produces large -

size pictures for projection with sharpness and

detail approaching that of a conventional TV

picture. Designed by Zenith scientists, the sys-

tem is one of a number of approaches to TV

picture displays of the future being investigated

in Zenith laboratories, The experimental laser

system demonstrates the feasibility of an all -

electronic approach to a TV picture display

using a laser light source. Their achievement

represents a step toward developing the tech-

nology necessary for new methods of TV pic-

ture display not dependent on the cathode -ray

tube.

Block diagram of Zenith's experimental laser TV

system shows four major components in processing of

picture and stages where TV signals from parts of

TV chassis are processed and fed into system.

Complete chassis is not necessary to system, but

is used to provide necessary electronic signals and

for monitoring.

Zenith's experimental laser display system

uses: a 50 milliwatt, helium -neon laser light

source; a first ultrasonic diffraction cell for in-

(Continued on page 10)

ELEMENTARY ELECTRONICS

Regardless Of What You Pay

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New Heathkit® "180"

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This new Heathkit GR -180 has exclusive built -in

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Simple -to- follow instructions and detailed color

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Results? Beautifully clean and sharp color pictures

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Exclusive Heath Magna -Shield ... surrounds the en-

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gaussing demagnetizes and "cleans" the picture

everytime you turn the set on from a "cold" start.

Choice Of Installation ... Another Exclusive! The

GR -180 is designed for mounting in a wall or your

own custom cabinet. Or you can install it in either

optional Heath factory -built Contemporary or Early

.American styled cabinets.

From Parts To Programs In Just 25 Hours. All criti-

cal circuits are preassembled, aligned and tested at

the factory. The GR -180 manual guides you the

rest of the way with simple, non -technical instruc-

tions and giant pictorials. You can't miss!

Plus A Host Of Advanced Features ... like the hi -fi

180 sq. inch rectangular tube with "rare earth phos-

phors", smaller dot size and 24,000 volt _picture

power for brighter, livelier colors and sharper defini-

tion ... Automatic Color Control and gated Auto-

matic Gain Control to reduce color fading and insure

jitter -free pictures at all times . deluxe VHF

Turret Tuner with "memory" fine tuning ... 2 -Speed

Transistor UHF Tuner ... Two Hi -Fi Sound Outputs

for play through your hi -fi system or connection to

the GR -180's 4" x 6" speaker ... Two VHF Antenna

Inputs -a 300 ohm balanced and a 75 ohm coax

... I -Year Warranty on the picture tube, 90 days

on other parts. For full details mail coupon on the

following page. Better yet, use it to order the best 19'

Color TV buy ... it's available now in limited quan-

tities.

*Kit GR -180, everything except cabinet,

102 lbs. $379.95

GRA- 180 -1, walnut cabinet (shown above),

30 lbs...183/4" D x 283/4" W x 29" H..... $49.95

GRA- 180 -2, Early American cabinet,

37lbs ...183/4" Dx28%. "Wx313/4" H...

Available February $75.00

NEW 12" Transistor Portable TV - First Kit With Integrated Circuit

Unusually sensitive performance. Plays any-

where ... runs on household 117 v. AC, any

12 v. battery, or optional rechargeable battery

pack ($39.95); receives all channels; new inte-

grated sound circuit replaces 39 components;

preassembled, prealigned tuners; high gain IF

strip; Gated AGC for steady, jitter -free pic-

tures; front -panel mounted speaker; assembles

in only 10 hours. Rugged high impact plastic

cabinet measures a compact 111/2" H x 15'/4" W

x 93A" D. 27 lbs.

Kit GR -104

$1 1 995

Turn Page For More New Kits From HEATH

MARCH -APRIL, 1967 7

How To Have Fun While You Save ..

Harmony -by- Heathkit Electric Guitars & Heathkit Guitar Amplifier

D

o $12995

Kit TA -16

NEW Heathkit Transistor Guitar Amplifier

o

Kit TG -46

$21995

(save $11111.55)

60 watts peak power; two channels - one for ac-

companiment, accordian, organ, or mike, - the

other for special effects ... with both variable reverb

and tremolo; 2 inputs each channel; two foot

switches for reverb & tremolo; two 12" heavy -duty

speakers; line bypass reversing switch for hum re-

duction; one easy -to -build circuit board with 13

transistors, 6 diodes; 28" W. x 9" D. x 19" H.

leather- textured black vinyl cabinet of 3 %" stock;

120 v. or 240 v. AC operation; extruded aluminum

front panel. 52 lbs.

American Made Harmony -By- Heathkit Guitars

All wood parts factory assembled, finished and

polished . .. you just mount the trim, pickups and

controls in predrilled holes and install the strings

... finish in one evening.

These Valuable Accessories

Included With

Every Guitar Kit

Each guitar includes vinylized chipboard carrying

case, cushioned red leather neck strap, connecting

cord, Vu- Tuner® visual tuning aid, tuning record,

instruction book and pick . . . worth $19.50 to

$31.50 depending on model.

0 Deluxe Guitar ... 3 Pickups ... Hollow Body

Double- cutaway for easy fingering of 16 frets;

ultra -slim fingerboard - 2434" scale; ultra -slim

"uniform feel" neck with adjustable Torque -Lok

Kit TG -26

$0095 Kit TG -36

0

(save $47) (save S40.55)

reinforcing rod; 3 pickups with individually adjust-

able pole -pieces under each string for emphasis and

balance; 3 silent switches select 7 pickup combina-

tions; 6 controls for pickup tone and volume; pro-

fessional Bigsby vibrato tail -piece; curly maple

arched body - 2" rim - shaded cherry red. 17 lbs.

D Silhouette Solid -Body Guitar ... 2 Pickups

Modified double cutaway leaves 15 frets clear of

body; ultra -slim fingerboard - 24'/4" scale; ultra -

slim neck for "uniform feel "; Torque -Lok adjustable

reinforcing rod; 2 pickups with individually adjust-

able pole -pieces under each string; 4 controls for

tone and volume; Harmony type `W' vibrato tail-

piece; hardwood solid body, 1'/2" rim, shaded

cherry red. 13 lbs.

0 "Rocket" Guitar ... 2 Pickups ... Hollow Body

Single cutaway style; ultra -slim fingerboard; ultra -

slim neck, steel rod reinforced; 2 pickups with in-

dividually adjustable pole -pieces for each string;

silent switch selects 3 combinations of pickups; 4

controls for tone and volume; Harmony type 'W'

vibrato tailpiece; laminated maple arched body,

2" rim; shaded cherry red. 17 lbs.

NEW! Deluxe Solid -State FM /FM Stereo Table Radio

Tuner and IF section same as used in deluxe

Heathkit transistor stereo components. Other

features include automatic switching to stereo;

fixed AFC; adjustable phase for best stereo;

Kit GR -36 two 5'/4" PM speakers; clutched volume con-

$6995 trol for individual channel adjustment; com-

pact 19" W x 61/2" D x 91/4" H size; preassem-

bled, prealigned "front- end "; walnut cabinet;

simple 10 -hour assembly. 17 lbs.

8 ELEMENTARY ELECTRONICS

Build Your Own Heathkif Electronics

NEW Heathkit® /Magnecord® 1020 4 -Track Stereo Recorder Kit

Kit AD -16

$39950

(less cabinet)

Save $170 by doing the easy assembly yourself.

Features solid -state circuitry; 4 -track stereo or

mono playback and record at 71/2 & 31/4 ips;

sound -on- sound, sound -with -sound and echo

capabilities; 3 separate motors; solenoid oper-

ation; die -cast top -plate, flywheel and capstan

shaft housing; all push- button controls; auto-

matic shut-off; plus a host of other professional

features. 45 lbs. Optional walnut base $19.95,

adapter ring $4.75

New! SB -101 80 -10 Meter SSB Transceiver -

Now With Improved CW Transceive Capability

Now features capability for front panel switch

selection of either the USB /LSB standard 2.1

kHz SSB filter or the optional SBA -30I -2 400

Hz CW filter ... plus simplified assembly at no

increase in price over the already famous

Heathkit SB -100. Also boasts 180 -watt P.E.P.

input, 170 watts input CW, PTT & VOX, CW

sidetone, Heath LMO for truly linear tuning

and 1 kHz dial calibrations. 23 lbs. SBA -301 -2,

400 Hz CW filter ... $20.95. Kit HP -13, mobile

power supply ... $59.95. Kit HP -23, fixed

station supply $39.95

Kit SB -101

$36000

(less speaker)

2 -Watt Walkie -Talkie

Assembled

GRS-65A

$9995

New ... Factory Assem-

bled. Up to 6 mile range;

rechargeable battery; 9 sili-

con transistors, 2 diodes;

superhet receiver; squelch;

ANL; aluminum case. 3

lbs. 117 v. AC battery

charger & cigarette lighter

charging cord $9.95. Crys-

tals $1.99 ea.

FREE

HEATHKIT 1967 World's Largest

Electronic Kit

Catalog!

108 pages ... many in

full color ... describe

these and over 250

easy -to -build Heathkits

for color TV, stereo/

hi -fi, CB, ham, marine,

shortwave, test, educa-

tional, home and hobby

items. Mail coupon for

your free copy.

MARCH -APRIL, 1967

r

NEW Portable Phonograph Kit

Kit GD -16

$3995

All Transistor. Assembles

in 1 to 2 hours. Preassem-

bled 4 -speed automatic

mono changer; 4" x 6"

speaker; dual Sapphire

styli; 45 rpm adaptor; olive

& beige preassembled cab-

inet; 117 v. AC. 23 lbs.

HEATH COMPANY, Dept. 139.3

Benton Harbor, Michigan 49022

Enclosed is $ , plus shipping.

Please send model (s)

Please send FREE 1967 Heathkit Catalog.

Name

Address

City State Zip

L Prices & specifications subject to change without notice. CL -269

9

When a Pioneer Speaks

...it's time to listen!

That's when you'll hear the optimum in tonal

quality ... sound reproduction at its faithful

best.

You can always count on Pioneer speakers and

speaker systems to deliver a quality perform-

ance. Every time. All the time.

Made by the world's largest manufacturer of

speakers, this premium audio equipment is avail-

able at popular prices.

And you can select from many fine models -from

the unique, handsome metal -grilled CS -24 Auxil-

iary Wall Speaker to the efficient, compact CS -20,

CS -52 and the Ultimate 5- speaker CS -61 Book-

shelf System. All carried only by franchised

dealers.

A word from you and we'll send literature and

the name of your nearest dealer.

(A) CS -62 Bookshelf 3 -way speaker system (3 speakers ).

Oiled walnut enclosure. Meas. 254 "x 15% 6 '" x 111 ,,

retail price: $142.00.

(B) CS -61 Bookshelf 3 -way speaker system (5 speakers).

Oiled walnut enclosure. Meas. 241/4" x 161 MG" x 131/4 ",

retail price: $175.00.

(C) CS -20 Compact 2-way speaker system. Oiled walnut

enclosure. Meas. 131/4" x 8" x 81/2", retail price: $35.00.

(D) CS-24 wall or enclosure. Meas. system.

4

x 105/. "x 43/4 ", retail price: $27.75.

(E) CS-52 Compact 2 -way speaker system. Oiled walnut

enclosure with gold metal trim. Meas. 131/2" 81/4" x 81/2",

retail price: $59.95.

PIONEER ELECTRONICS U.S.A.

CORPORATION

140 SMITH AVENUE, FARMINGDALE, LONG ISLAND, N.Y. 11735

(516) 6947720

10

NEWSCAN

tensity modulation; a second diffraction cell

that acts as a horizontal deflector which pro-

vides a high degree of resolution; and a ver-

tical deflector. They perform essentially the

same functions as parts of a conventional pic-

ture tube and deflection yoke. In addition there

are a number of optical components to shape

and focus the beam on a screen. Because a

helium -neon laser emits a red light beam, the

picture on the screen is black and red.

The principle of using ultrasonic waves to

interact with a light beam is one that has been

known for some 30 years. Previously it was

thought that ultrasound could only be applied

to intensity modulation or control of bright-

ness. TV signals for display by the system are

provided by portions of a regular TV chassis

and are processed before being fed into the

intensity modulation (video), horizontal deflec-

tion and vertical deflection stages of the system.

Honest Weight

A new portable electronic platform scale de-

veloped by Revere Corporation of America

determines the load imposed by the wheels of

a "front loader" with precise accuracies of

99.95% (better than Ivory soap). Battery -

powered and designed specifically for use in

A big ¡ob by a small bit of electronics is performed

by Revere's portable electronic scale.

remote areas, the unit's platforms and ramps

weigh only 800 lbs. A technician is shown

reading the instrument which indicates the load

put on each of the two platforms by the 70,000 -

lb. frontloader. Rear wheels can be measured

simply by driving the frontloader forward a

few feet. The combined load of the platforms,

each with a capacity of 100.000 lbs., is trans-

mitted through Revere electronic load cells in

(Continued on page 12)

ELEMENTARY ELECTRONICS

Build this famous knightkif

Star Roamer® 5 -Band Shortwave Receiver Kit

- YOUR SATISFACTION

GUARANTEED BY 4111(0

and have the whole wide world at your fingertips!

Think of it! -even if you know nothing at all about

electronics -in a few fun -filled evenings you can

assemble the Knight -Kit Star Roamer that lets you

listen to the four corners of the world!

You visit the famous cities of Europe, Asia, Africa

... get continuous 24- hour -a -day aviation weather -

casts ... zero -in on Coast Guard LORAN signals

. get the exact time from station W W V in

Washington, D. C.... listen in on the interesting

conversations of Hams, Citizens Banders and Radio

Telephoners -AND listen to your favorite programs

on the standard AM band, too.

Thousands of folks of all ages have assembled

the Star Roamer and have been amazed at how

easy it is. All you do is follow crystal -clear, non-

technical instructions and extra -large illustrations

that show where every part fits ... and almost

r

i..

04 ,

_ _ KNIGHT -KIT GUARANTEE vJVJ

Build a Knight -Kit in accordance with

our easy -to- follow instructions. When

you have completely assembled the

kit, you must be satisfied or we will re-

turn your money, less transportation

charges, under the Allied guarantee of

satisfaction. ALLIED RADIO

,

1 1

'.4 ,

r -,rnt%rIfnr-n u - i IIAlif iVilli Pn +lrrliiIMll ï

MARCH -APRII., 1967

before you know it you're listening to exciting

broadcasts from all over the world!

The Star Roamer covers 200 to 400 kc and

550 kc to 30 me in 5 bandswitched ranges, and

features a reliable superhet circuit... plus Auto-

matic Volume Control to prevent fading and blast-

ing, illuminated "5" meter for fine tuning, and

many other features found only in shortwave re-

ceivers that cost many times more.

Complete with all parts, handsome 51/2 x 121/2 x

8" charcoal gray and aluminum

case, and easy -to- follow assem-

bly instructions for only

Read the unique money -back guarantee ..

exclusive in the industry ... then rush coupon

for full details and Special Introductory Offer.

r ALLIED RADIO, Knight -Kit., Dept. S 1 CC

P.O. Box 4398, Chicago, III. 60680

Please rush full details and Special Introductory Offer

on the Knight -Kit Star Roamer 5 -Band Short-

wave Receiver.

Name

Address

City State lip

PLEASE PRINT

11

tom"

Fill in coupon for a FREE One Year Subscrip-

tion to OLSON ELECTRONICS' Fantastic Value

Packed Catalog- Unheard of LOW, LOW PRICES

on Brand Name Speakers, Changers, Tubes,

Tools, Stereo Amps, Tuners, CB, and other Val-

ues. Credit plan available.

NAME

ADDRESS

CITY STATE ZIP_

If you have a friend interested in electronics send

his name and address for a FREE subscription also.

OLSON ELECTRONICS

INCORPORATED

577 S. Forge Street Akron, Ohio 44308

Get Your

F.C.C. LICENSE

and

A.S.E.E. DEGREE

We offer the following courses - all

approved under the new G.I. Bill. Select

the course you are interested in, and write

or phone for free details.

Electronics Engineering Technology (resident

course, which leads to the A.S.E.E. degree) ;

Basic Electronics Engineering Technology

(correspondence course, which covers the first

1/3 of the EET course listed above, and credit

for which can be applied toward the A.S.E.E.

degree) ;

Communications Electronics (resident course

which leads to the FCC first class license and

trains you to be a communications technician) ;

F.C.C. License Course (correspondence course,

which prepares you for your FCC first class

radiotelephone license - after completing this

course, if you should fail to pass the FCC

exam for this license all your tuition payments

will be refunded).

For free brochure, write:

Desk 6 -R

Grantham School of Electronics

1505 N. Western Ave., Hollywood, Cal. 90027

Phone: (213) 469 -7878

818.18th St., NW, Washington, D.C. 20006

Phone: (202) 298 -7460

12

NEWSCAN

the ramps to the readout instrument, where the

signal is amplified and translated into a meter

reading giving the actual load. Device can be set

up alongside highways in minutes to check axle

loads on trucks. State police checking axle

loads of trucks will now be able to set up check

points almost anywhere.

Mini -Tools

The world, truly, is getting smaller. Ma-

chined parts that were thought to be tiny only

a few years ago are, by today's standards, big.

Pictured below on the small stand of a micro-

scope are dozens of different parts machined of

You can tell how small small is by comparing

machined parts to centimeter scale on

microscope stage platform.

stainless steel for the computer, electronics,

telephone, missile and communications indus-

tries. These machined parts of stainless steel

are made by laymax Precision Products, Inc.,

Subsidiary of Vernitron Corporation where

plus or minus .0002" is standard measurement.

The firm is using stainless steel in some top

secret jobs that will find their way to outer and

inner space.

Viet Tape

Television's familiar instant replay brought

three soldiers in Vietnam together with their

families in Chicago recently in the first test of

a proposed system of "video tape letters" home.

Videotape recordings of the three men were

made at the USO in Saigon and flown to Chi-

cago for the test. The parents of the soldiers

in the test tape were invited to the Chicago

USO to view the recordings and record return

audio and video messages to their sons. Lt.

Thomas C. Coll, Sp /4 Edward A. Bailey and

(Continued on page 14)

ELEMENTARY ELECTRONICS

LAFAYETTE HB -525 Solid State

Mobile 2 -Way Radio

All Crystals Supplied!

Size: 23/4" by 61/4" 99.3076WX*

All CB Cha

Crystal nnels

Controlled

Plus 2 Reserve Channels

19 Transistors, 7 Diodes, Thermistor

Dual Conversion Receiver for Extra Selectivity

and Sensitivity

Full 5-Watt Input

Range BoostTM Circuitry for Added Power

3- Position Delta Tune -Provides Accurate Fine

Tuning

Mechanical 455KC Filter for Superior

Selectivity

FREE

Over 500 Pages

MARCH-APRIL, 1967

Push -to -Talk Dynamic Microphone

Variable Squelch plus Series Gate Automatic

Noise Limiting

Public Address System (with external speaker)

12 -Volt DC Operation (pos. or neg. ground) 6-

Volt DC (with optional DC Power Supply)

Pi- Network for Optimum RF Output

117 Volt AC Operation with Optional Power

Supply `Imported

1967 CATALOG NO 670

Featuring Everything in Electronics for

HOME INDUSTRY LABORATORY

from the "World's HiFi & Electronics Center"

LAFAYETTE Radio ELECTRONICS

Dept. DEEC -1 P.O. Box 10

Syosset, L. I., N. Y. 11791

I I I Name

I

I City

Address

Send me the FREE 1967 LAFAYETTE Catalog 670

State Zip

()EEC-]

r- I McGEE RADIO CO..

1907 McGee St.

Kansas City 8, Missouri

SEND 1967 McGEE CATALOG

I NAME

I ADDRESS

p_ CITY ZONE.... STATE

NOW RI FOR M c G E E' S

1967 CATALOG

1001 BARGAINS IN

SPEAKERS -PARTS- TUBES -HIGH FIDELITY

COMPONENTS -RECORD CHANGERS -

TAPE RECORDERS -KITS-

EVERYTHING IN ELECTRONICS

J

Tape this ad to the back of your TV or Radio Set

ALL TV- RADIO $ 1

RECEIVING TUBES ra

ALL BRAND -NEW, First Quality. All

Types Available. Orders Shipped First

Class Same Day Rec'd. Unconditionally

Guaranteed. 24 Month Warranty.

Send $1 for ea. tube + 50e. postage &

handling of entire order. FREE: Write

for "do -it- yourself" TV Test Chart and

Tube List to Dept. EE -347. et%

UNIVERSAL TUBE CO. Ozone Park, N. V. 11417

Learn how to become a

GAME WARDEN

GOV'T HUNTER, FORESTER, WILDLIFE MANAGER

Exciting job openings now for qualified men who love

outdoor work. Protect forests and wildlife- arrest vio-

lators! Good poy, security, prestige and authority for

respected career Conservation Officers. Easy home -

study plan! Send for FREE Fact BOOK, aptitude QUIZ,

SUBSCRIPTION to Conservation magazine. State age.

NORTH AMERICAN SCHOOL OF CONSERVATION

Campus Drive, Dept. 1353, Newport, Calif. 92660

ALL BAND BATTERY SHORT WAVE RADIO KIT .12.95

Listen around the world-Thousands of miles

away! Ships -Aircraft -Voice of America -Rus-

sia- London- Australla- Amateurs -Police. Also

LSA Broadcast -5 Wave Bands Le to 43 MC!

Calibrated tuning dial. Wt. only 3 lbs. World

wide reception.

Send only gg g5 COO pstgnr sendp$12.95

$3 00 for PP del In USA. Basic Kit as

f shown Secludes plastic case and

BC cull FREE. Long Distance antenna. if you

order NOW. Available only from Midway Co.,

Dept. BE -3, Kearney, Nebr.

Learn of the many money making ideas

and low cost /high profit businesses you can

start in.

INCOME OPPORTUNITIES -750

on sale now

Take the guessing out of home buying.

Complete plans and specifications from

leading architects.

SMALL HOME PLANS -$1.25

on sale now or write Davis Publications,

Inc. /505 Park Ave. /New York, N. Y. 10022.

Add 25 each for postage & handling.

NEWSCAN

Ampex brings the boys home from Viet Nam for a

taped video chat with loved ones in the

Chicago area.

Pfc. Donald P. Kunzer, all from the Chicago

area, were the three servicemen who partici-

pated in the test.

Recorders used for the Vietnam USO test

are Ampex models costing substantially less

than recorders used by the broadcasting stations

and were available for the first time this year.

They are primarily designed for closed circuit

use in education, industrial training, medicine

and government applications.

Indigestible Goodies

There is nothing edible in these boxes unless,

of course, you're a goat! The "oranges and

plums," actually made of hard maple, and the

assorted ceramic triangles, and carpet tacks,

What can an editor write here other than,

"Look and enjoy."

carborundum nuggets and roofing nails are used

at the Scintilla Division plant of The Bendix

Corporation, Sidney, N. Y., to remove "flash-

ing" or rough edges from threads in electrical

connector parts for space and defense applica-

tions. The connectors are tumbled in huge bar-

rels containing any number of the materials

shown in front of the pretty Miss. The tumbling

"clean -up" insures that the threads will make

a tight seal. (Continued on nape 171

14 ELEMENTARY ELECTRONICS

BUILD 20 RADIO

CIRCUITS AT HOME

with the New Improved

PROGRESSIVE RADIO "EDU -KIT "®

A Practical Home Radio Course

Now Includes

* 12 RECEIVERS

* 3 TRANSMITTERS

* SQ. WAVE GENERATOR

* SIGNAL TRACER

* AMPLIFIER

* SIGNAL INJECTOR

* CODE OSCILLATOR

only

* No Knowledge of Radio Necessary

* No Additional Parts or Tools Needed

* EXCELLENT BACKGROUND FOR TV

* * Sold In 79 Countries

SCHOOL INQUIRIES INVITED

95

YOU DON'T HAVE TO SPEND

HUNDREDS OF DOLLARS FOR A RADIO COURSE

The "Edil -Kit" offers you an outstanding PRACTICAL HOME RADIO COURSE at a

rock - bottom price. Our Kit is designed to train Radio & Electronics Technicians, making

use Of the most modern methods Of home training. You will learn radio theory, Construc-

tion practice and servicing. THIS IS A COMPLETE RADIO COURSE IN EVERY DETAIL.

You will learn how to build radios, using regular schematics; how to wire and solden

In a professional manner; how to service radios- You will work with the standard type of

punched metal chassis as well as the latest development of Printed Circuit chassis.

You will learn the basic principles of radio. You will construct, study and work with

RF and AF amplifiers and oscillators, detectors, r ctifiers, test equipment. You will learn

and practice code, using the Progressive Code Oscillator. You will learn and practice

trouble -shooting, using the Progressive Signal Tracer, Progressive Signal Injector, Pro -

gressive Dynamic Radio & Electronics Tester, Square Wave Generator and the accompany-

ing Instructional material.

You will receive training for the Novice, Technician and General s of F.C.C. Radio

Amateur Licenses. You will build Receiver, Transmitter, Square Wave Generator, Code

Oscillator, Signal Tracer and Signal Injector circuits, and learn how to operate them. You

will receive an excellent background for television, Hi-Fi and Electronics.

Absolutely no prevìou knowledge of radio or science is required. The "Edu -Kit" is

teaching

product of many years of teaching nd engineering experience. The 'Edu -Kit" will

provide you with basic education in Electronics and Radio worth many times the low

price you .pay. The i more

Tracer alone is worth m e than the rice

e of the kit.

THE KIT FOR EVERYONE

You do not need the slightest background

In radio or science. Whether you are Inter-

ested in Radio & Electronics because you

want an interesting hobby. a well aying

business or a job with a future, you will find

the any0uthousandsw ofh Individuals

Investment.

of all

ages and backgrounds have successfully

used the "EduKit'' in more than 79 coon.

tries of the world. The "Edu -Kit" has been

carefully designed, step by tep, so that

you cannot make a mistake. The Edu -Kit"

allows you to teach yourself at your own

rate. NO instructor is necessary.

PROGRESSIVE TEACHING METHOD

The Progressive Radio "EduKit" Is the foremost educational radio kit in the world.

and is universally accepted as the standard in the field of electronics training. The "Edu -

Kit" uses the modern educational principle of "Learn by Doing -" Therefore you construct,

learn schematics, study theory, practice trouble shooting -all In a closely Integrated pro-

gram designed to provide an asilYlearned, thorough and Interesting background in radio.

You begin by examining the various radio parts of the Edu-Kit." You then learn the

function. theory and iring of these parts. Then you build a simple radio- With this first

set You will goy listening to regular broadcast stations, learn theory. practice testing

and trouble-shooting. Then you build a more advanced radio, learn more advanced theory

and techniques. Gradually, in a progressive manner. and at your own rate. you will

find yourself constructing more advanced multi -tube radio circuits. and doing work like a

Professional Radio Technician.

Included in the 'Edu -Kit" course are Receiver, Transmitter, Code Oscillator, Signal

Tracer. Square Wave Generator and Signal Injector Circuits. These are not unprofessional l

"breadboard" experiments, but genuine rags the rats,

circuits, constructed by

of of pro^e siown

wiring and soldering on metal chassis. p

as "Printed Circuitry." These circuits operate on our re ,ular AC or construction

house current.

THE "EDU -KIT" IS COMPLETE

You will receive all parts and instructions necessary to build twenty different radio and

electronics circuits, each aranteed to operate. Our Kits contain tubes, tube sockets. vari-

able, electrolytic, mica, ceramic and paper dielectric condensers, resistors, tie strips,

hardware, tubing, punched metal chassis, Instruction Manuals, hook -up wire, solder,

selenium ectifiers, coils, volume controls and switches, etc.

In addirtion, you receive Printed Circuit materials, including Printed Circuit chassis,

special tube sockets, hardware and instructions. You also receive a useful set of tools, a

professional electric soldering iron, and a self -powered Dynamic Radio and Electronics

Tester. The "Edu -Kit" also includes Code Instructions and the Progressive Code Oscillator,

in addition to F.C.C. Radio Amateur License training. You will also receive lessons for

servicing

with the Progressive Signal Tracer and the Progressive Signal Injector, a High

Guide and a Quiz Book. You r a eeive Membership in Radio -TV Club, Free Consulta-

tion Service, Certificate f Merit and Discount Privileges. You receive all parts, tools,

instructions, etc. Everything is yours to keep.

PRINTED CIRCUITRY

At no increase in price, the "Edu -Kit"

now includes Printed Circuitry. You build

a Printed Circuit Signal Injector, a unique

servicing instrument that can detect many

Radio and TV troubles. This revolutionary

new technique of radio construction is now

becoming popular in commercial radio and

TV sets.

A Printed Circuit is a special insulated

chassis on which has been deposited a con-

ducting material which takes the place of

wiring. The various parts are merely plugged

in and soldered to terminals.

Printed Circuitry is the basis of modern

Automation Electronics. A knowledge of this

subject is a necessity today for anyone in-

terested in Electronics.

MARCH -APRIL, 1967

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15

Tips from a

Technician's

Notebook

Shortcuts -developed, and used,

by our readers -to make your

servicing and troubleshooting

easier and more professional.

11111111111111!

MIDGET EXTENSION LIGHT

Almost daily there is a need for a tiny

extension light for seeing in close quarters.

Such a light can be easily made that will be

self- supporting in two ways if this is desir-

able. Fasten a miniature lamp socket to one

side of a spring -type clothespin. To the other

side of the clothespin attach the magnet ele-

ment from an automatic can opener. The

light is complete for connecting to a battery

power source. Connect alligator clips to the

long lamp leads so they may connect to bat-

tery or 6.3 -volt AC filament transformer.

The magnet will cling to iron tools for extra

reach.

1111111111111111111111I11111111111111111111111111111111111111111111111111111111111111111111111111111111111111ÌI

EMERGENCY COUPLER breadboards. A 3- to 4 -inch length of hose

HAS ZERO BACKLASH makes a good flexible coupler for connect-

ing the shaft of a variable component to a

A one -inch length of automobile wind- knob shaft when the two shafts are out of

shield wiper hose can be used as a quick, in- line up to 45 degrees from each other -back-

expensive 1/4 "- to -1/4" shat coupler for radio lash is practically nil.

and other electronic gadgets. While not in- Other uses for the hose include couplers

tended to replace conventional couplers for small electric motors, Veeder -Root coun-

which employ set screws, the hose does grip ters -in fact, anywhere 1/4 -inch shafts are

the shafts with surprising tenacity, making used, and the load requirements are mod -

it handy in an emergency or in experimental erate.

!1! 1111111! 11111111111 !IIIIIIIi11111111I11111!IIIII

DISCARDED PORTABLE BECOMES TEST SPEAKER

OUTPUT OUTPUT VOICE COIL

TRANS. JACK TRANS. JACK

V

If you own an old tube -type radio portable

that's ready for the garbage can, you're in

for a windfall by simply converting it to a

portable test speaker. Scrap all of the set's

guts except the PM speaker and output trans-

former. Now scrounge up open- circuit and

closed circuit phone jacks (see schematic dia-

gram), phone plug, wire, and two alligator

clips with rubber sleeve insulators. Wire up

the portable case as shown in the schematic

diagram and label the cabinet's front panel

so you will know which jack is which. Now

wire up a patch cord using 3 feet of rubber

test lead lengths to the phone jack and install

the alligator clips to the wire's free ends.

Now you can connect the test set to speaker

terminals nr into andin nlata r.,rr,,;t.

16 ELEMENTARY ELECTRONICS

s

NEWSCAN

First Neon Sign

The glass tube shown in the photo below is

believed to be the world's first neon sign. In

1904 Dr. Perley G. Nutting, a pioneer electrical

scientist at the National Bureau of Standards,

devised illuminating glass tubes which were

LONG NOSE AND

DIAGONAL PLIERS

look 10

Icelile for

me best in

p1Ì¢15 & SÑps, 100

CHAIN NOSE ELECTRICIANS

PLIERS

Most people will say, "So what!" But take a good

look. That bent tube of glass and gas was one of

the first neon signs ever to go on display.

filled with gas and lighted by passing an electri-

cal discharge through them. The signs were used

in an NBS exhibit in the Louisiana Purchase

Exposition in St. Louis in 1904. Commercial

application followed some 26 years later. The

first neon sign said, appropriately enough,

"neon."

This tube and several others from Nutting's

laboratory are on display at the museum of the

U. S. Department of Commerce's National

Bureau of Standards in Gaithersburg, Mary-

land. Come on down next vacation time.

Rolling Switchboard

Here's a switchboard with an ocean going roll

aboard a luxury cruise ship. When completed it

will supply the passengers with 400 lines, 6

trunk circuits, and direct connections with any

telephone in the world through the vessel's

VIVZ,.: RADIO AND TV PLIERS

COMBINATION

SIIP JOINT PLIERS

SIDE CUTTING PLIERS

TRANSVERSE

CUTTING PLIERS

UTILITY PLIERS

Sea -going switchboard contacts the world

by telephone.

radio room. Installer Arne Brenden, of the

Norwegian subsidiary of ITT, installs the mod-

ern "Pentaconta" crossbar telephone equipment

on the high seas. The automatic exchange is

being installed while the vessel is enroute and

will be completed about the time the boat docks

in Scandinavia at the end of cruise.

Same professional quality as famous Xcelite screw

drivers and nutdrivers. Forged alloy steel construc-

tion. Precision machined. Scientifically proportioned.

Variety of sizes. All available with permanent. plastic

coated Cushion Grip handles for extra working com

fort (except slip joint models).

r-- --1

XCELITE INC. 80 BANK ST., ORCHARD PARK, N. Y.

Send Catalog Sheet N664 on pliers and snips.

name

address

city state & zone

MARCH -APRIL, 1967 17

ASK

ME

ANOTHER.

Elementary Electronics brings the know -how of an

electronics expert to its readers. Leo G. Sands,

columnist for Radio -TV Experimenter, will be

happy to answer your question. Just type or print

your unsolved problem on the back of a 40 postal

card and send it to "Ask Me Another," Elementary

Electronics, 505 Park Avenue, New York, New

York 10022. Leo will try to answer all your ques-

tions in the available space in upcoming issues of

Elementary Electronics. Sorry, Leo will be unable

to answer your questions by mail.

Can't Have One

Why is a dry cell tested for life in volts in-

stead of amps when it's amperage that counts?

Cells I have tested whose voltage is normal, but

amperage is low, don't light a lamp as well as

one whose amperage is higher.

-D. H., Peterborough, Ontario

The old- fashioned way to test dry cells was

with an ammeter. The current way is to measure

the voltage of the cell while under load, as shown

in the diagram. Checking voltage with no load

can lead to erroneous conclusions. Each size of

dry cell has its own load to meet manufacturers

specifications -best test is to use the regular op-

erating load when measuring voltage.

1 115v

+ VOLTMETER

LOAD

Needs a Map

I bought a used telephone -answering recorder,

Carroll Electronics Model RCI. I am having

trouble getting a suitable interconnecting plug.

Can you give me a schematic? I can't seem to

find Carroll Electronics. What is their address?

How About That!

Where can I get a schematic of a Tonefunk

Model W 6056W AM, FM and SW radio and

record player? Eleven servicemen in Winston -

Salem say that nothing can be done without a

diagram. The German manufacturer no longer

makes radios. Sams and Supreme don't have the

diagram. -1. E. M., Rural Hall, North Carolina

An expert should be able to fix any radio with

or without a diagram. The schematic just makes

it easier. Perhaps a reader has a diagram. If so,

please contact J. E. M. at P.O. Box 94, Rural

Hall, North Carolina.

Change to PM Speakers

How can I modernize old radios? 1 would

like to replace electromagnetic speakers with PM

types. -W. W., (Address not given)

Hope you aren't confusing electromagnetic

with electrodynamic speakers -they're quite dif-

ferent. Magnetic speakers weren't much more

than glorified earphones -a high- impedance

(2,000 to 5,000 ohms) coil that vibrated a paper

cone. No output transformer was used.

Electrodynamic speakers are quite modern by

comparison -a low- impedance coil moving in a

field generated by an electromagnet. Electro-

dynamic units have at least four leads to the

speaker proper -two for the voice coil; two for

the field coil.

For magnetic speaker replacement use a uni-

versal output transformer. Connect the primary

to the speaker terminals and the speaker across

the transformer secondary taps that give maxi-

mum volume and best sound quality.

Field coils for the electrodynamic speakers

are of two types -high resistance (5000 to

15,000 ohms) and low resistance (under 2000

ohms). The high resistance field coils are con-

nected across the DC supply and are used as a

bleeder resistance and if you leave it out of the

circuit it won't matter usually -if it is part of a

resistance network you can replace it with a

high- wattage resistor. The low- resistance field

coils are used as filter chokes and either must

be left in the circuit, replaced with a choke or

with a resistor. (Better install new filter capaci-

tors too -ones with 40 to 60 mf rating for better

DC filtering since the hum -buck circuitry will

not be in the PM circuitry.)

-R. J., Palos Park, Illinois PRI

Don't have a schematic available. But, you ,®

probably can get one from the manufacturer iwrJ

whose address is listed as 1205 West Roscoe MAGNETIC

Street in Chicago. SPEAKER

TERMINALS

OUTPUT

TRANSFORMER

18

PM

SPEAKER

ELEMENTARY ELECTRONICS

Mike Low -Down

1 have a low -impedance mike and several

high- impedance amplifiers and 1 would like to

connect the mike to the amplifiers without re-

wiring them. How can 1 do it?

-D. B., Eldorado, Texas

Use a matching transformer as shown in the

diagram and adjust the primary transformer

taps to match your mike.

SHIELDED

CABLE

LOW-IMPEDANCE

MICROPHONE

SHIELDED

CABLE

LOW-IMPEDANCE MICROPHONE -

TO - GRID TRANSFORMER

MICROPHONE

PLUG

400 Hz Supply

1 would like to get a power supply delivering

115 -volt, 400 -cycle AC for a radar set. Can you

tell me where 1 can buy one or how to build one?

-R. B., Swedesboro, New Jersey

Bogue Electric, 100 California Avenue, Pater-

son, New Jersey, makes 400 -cycle power sup-

plies, but they aren't cheap. Don't forget that

you can't operate a radar lawfully unless you

have a station license to cover it.

Color -TV Service Info

What is the correct procedure for adjusting

the color in my Zenith TV set? It has gain con-

trols for red, blue and green but I am at a loss

to know what to do with them.

-N. P. P., East Tawas, Michigan

Get a Sams Photofacts kit for your set at a

radio parts distributor. It should contain the

information you need. Don't overlook the serv-

ice manual published by the manufacturer -send

model and serial number for exact information.

Off Calibration

1 have a communications receiver which con-

tains a 100 -kc crystal calibrator. The dial mark-

ings are away out of line. Using the calibrate

re -set control, 1 can't get them into line. 1 have

tried connecting a trimmer capacitor across the

calibrate re -set capacitor but this put it off more.

Can you suggest anything?

-J. W. G., Oakville, Ontario

First, check the dial calibration -tune in

known- frequency stations like WWV and any

others that you might be able to find that are

listed in White's Radio Log. Check all bands

-if calibrations are "off" by the same amount

it would seem most likely that your tuning dial

is not positioned properly on the tuning- capacitor

shaft. If calibrations are "off" only on some

bands (or more on some than others) it would

seem that realignment and recalibration are

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MARCH- APRIL, 1967 19

ASK ME ANOTHER

needed. Once the dial is calibrated properly

tune to WWV on 2.5, 5, 10 or 15 MHz (mc)

and adjust to 100 -kHz (kc) crystal calibrator

to zero -beat with the WWV carrier.

Adding Bandspread

I have an ancient Emerson Model 524 re-

ceiver and 1 would like to know if I can band -

spread the ham bands over a longer portion of

the shortwave bands. I am planning to use it

as a novice receiver and would like, if possible

to spread the 40 and 80 meter bands.

-N. G., Flemingsburg, Kentucky

Add an auxilliary local- oscillator- tuning ca-

pacitor as shown in the diagram. Mount it close

to the present tuning capacitor gang -use a shaft

extender, if necessary, to couple the bandspread

capacitor to its own tuning dial. Maximum ca-

pacitance of the bandspread capacitor probably

won't be as high as 50 uuf and may be as low

as 25 uuf if you want to keep the oscillator

within the bandpass of the RF circuits. The

relatively -broad tuning of the IF amplifier may

not give you the selectivity you will probably

need for clear reception.

ADDED

BANDSPREAD-

TUNING TUNING

CAPACITOR

CAPACITOR 50MMF MAX.

4

Simple But Expensive

Is there a simple way of varying the speed of

a phonograph motor by electronic means?

-M. M. L., Port Jefferson, N. Y.

It depends upon the type of motor. If it is

frequency sensitive, you could use the set -up

shown in the diagram. But, why vary the motor

speed? While doing so, it might speed up or

slow down the music, it would also vary its

pitch.

000

40-100 Hz

VARIABLE FREQUENCY

AUDIO OSCILLATOR

AUDIO POWER

A

40 TO 100 WATTS

LINE

SIDE

0 0 O (J II 4 TO MOTOR

TAPPED VOICE COIL

TO 500 /1000 /1500 OHM

LINE TRANSFORMER

(ADJUST TAPS FOR 115 VOLTS

TO MOTOR )

Trapping TV Signals

Is it possible to block out the signals of a sta-

tion in our local area broadcasting on TV Chan-

nel 6 so I can pick up a station 162 miles away.

If so, how? -D. W., Jamestown, N. Y.

20

Not if the station you want is also on Channel

6. Even a good antenna will pick up some signal

for the rear if the station you want should be in

the opposite direction. To reduce effects of an

adjacent -channel TV station you can make a

simple wave trap with a small capacitor and a

short length of twin lead. If a small -value fixed

capacitor is used the twin lead will have to be

adjusted in length for maximum effect. If a com-

pression -type trimmer is used it is adjusted for

maximum effect.

The twin -lead trap is just taped loosely to the

lead -in -there is no direct connection. Certain

spots on the lead -in will give more effect than

others.

CONDUCTORS TWISTED

AND SOLDERED

TWIN LEAD?

2.7 TO 30MMF

TRIMMER

4 "T08.

RAZOR BLADE

SHORTING BAR

ANTENNA

IOMMF

MICA

CAPACITOR

12° TWIN LEAD

TWIN

LEAD TAPE

POSITION TRAP

ON LEAD -IN FOR

MAXIMUM EFFECT

A Little Light

I have an old Powell repeater flash and a re-

chargeable power supply, Model W.C. 20, both

of which after nearly 20 years, are now giving

me trouble. As Powell has gone out of business,

I am hoping that you might know where I could

get schematic diagrams of both units.

-W. J. M., Pocatello, Idaho

Never heard of either. If any reader has the

schematics, send them in, please.

Information vs. EDP

I have been told there is a big future in "infor-

mation" systems. What are they and where can

I get basic information?

-D. R., Hollywood, California

That's just another definition of computer sys-

tems and EDP (electronic data processing). Get

a copy of the September 1966 issue of Scientific

ELEMENTARY ELECTRONIça

i

1

American. For 60 cents you can get around 30

huge magazine pages of the latest information

about "information" and computers. If your

newsstand can't get you a copy order one from

the publisher at 415 Madison Avenue in New

York City. If you want to dig more deeply, get

a copy of "Computer Dictionary and Handbook"

by Charles J. Sippl, published by Sams. It costs

$12.95. Your local book store or radio parts

distributor should be able to get you a copy.

Are You for Real?

Where can I get a catalog listing schematics

of radio and TV sets which I repair.

-T. F. B., Springfield, Massachusetts

Write to Howard W. Sams & Co., Inc., 4300

West 62nd Street, Indianapolis, Indiana, and ask

for a Photof acts catalog.

Missed Aerobander

Can you give me a circuit for a transistor con-

verter covering from 108 to 132 me (MHz) for

use with a BCB transistor radio?

-B. R., Hunlock Creek, Pennsylvania

See the December 1965- January 1966 issue of

RADIO -TV EXPERIMENTER. On page 45 you will

find a construction article -the Aerobander.

Send us 75' and we'll send you a copy of that

issue if you don't have it- include 25Ç for post-

age and handling.

New Speaker Is Problem

Where can I get a field coil speaker for a small

table radio? Or, can I use a 4 -ohm PM speaker?

The black speaker lead runs to pin 6 of 12SK7,

the green one to the output transformer and the

yellow lead to pin 8 of a 35Z5.

-A. E. F., Phoenix, Arizona

Connect a PM speaker as shown in the dia-

gram, adding a filter choke to take the place of

the field coil.

ST ANC OR

C1002

OR EQUAL

Parts Problem!

In one of your construction articles an NE -77

neon lamp and a cadmium- sulphide photocell

are listed. I can't find such a neon lamp and

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Begin my subscription to INCOME OPPOR-

TUNITIES with the next issue. Enclosed is

me.o(Fo (Foreign: (cash

dd 75c a money-order). Bill

Name please print

Address

City

State Zip

MARCH- APRIL, 1967 21

Now, better than ever, the

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supersensitive photo meter

Here is a precision instrument that meets

the highest standards of any meter available.

It offers consistently accurate readings at

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The S &M Supersensitive Photo Meter uses

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22

ASK ME ANOTHER

don't know which type of photocell to use. Can

you tell me? -L. B., Macon, Georgia

The NE -77 is a one -watt lamp with wire ter-

minals, priced at $0.55 net. Newark Electronics

Corp. in Chicago lists it in its catalog. Try a

Clairex CL5M2 photocell priced at $1.75. This

cell will handle two watts.

Phones Replace Old Speaker

My old radio has four speaker wires. How

can I disconnect the speaker and permanently

install headphones? -l. A., Des Moines, Iowa

Leave the speaker connected because the

speaker field coil is usually the power supply

filter choke. To mute the speaker and use head-

phones, short circuit the voice coil terminals at

the speaker and connect the earphones through

a terminal strip in series with one of the voice

coil leads as shown in the diagram. If you use

high impedance earphones, connect a 10 -ohm

resistor across them as shown. If you use 8-

ohm headphones (Superex, etc.,), you can omit

the resistor. High- impedance headphones may

also be connected in place of the primary of the

driver transformer or the primary of the output

transformer unless you have push -pull output.

/// SHORT WIRES

HIGH- TOGETHER

IMPEDANCE

HEADPHONES

10n

RESISTOR

FIELD- COIL

LEADS

C T.

HIGH - IMPEDANCE

PHONES

SPEAKER

PUSH PULL

AMPLIFIER

Aid From Oldtimer

Your answer to the question about the circuit

of an old Atwater Kent radio was correct as far

as your knowledge goes. But, did you ever stop

to think that someone might have these circuits?

I have the circuit of the Atwater Kent plus a

thousand others including American Mohawk,

Acme, Amrad, Browning Drake, Gilfillan, Ko!-

ELEMENTARY ELECTRONICS

a

ster, Ozark, Silver Marshall, Wells Gardner, etc.

In the future I suggest you ask through your

pages if someone else may have what you are

looking for. Maybe we old radio men could help.

-S. E. S., Chatham, Ontario

So we're asking you. Those names are still

familiar and bring fond memories. How about

Fada, Sparton, Stewart Warner, Remler and

Bremer Tully? Readers, S. E. S. is Syd Sutton

whose address is 325 St. Clair Street in Chatham.

Syd, we'll keep you in mind and are delighted

to know someone had sense enough to save those

old schematics.

Add An S -Meter

How can 1 hook up an "S" meter to my short-

wave receiver? -S. H., Stillwater, Minn.

Easy. Simply add two potentiometers and

connect a 0 -1 DC milliammeter between the

cathode of an 'IF amplifier which is controlled

by AVC and the cathode of the AF power am-

plifier as shown in heavy lines in the diagram.

Replace the AF power amplifier cathode re-

sistor with a 2 -watt potentiometer (Rl) having

approximately the same resistance as the orig-

inal resistor. Adjust this pot for meter zero

with no signal received and pot R2 to meter

full -scale when receiving the strongest signals.

AFAhPOWER

P

BREAK CIRCUIT HERE

10 -Code for CBing

I am planning to have some CB QSL cards

printed and want to list the 10 -code (104, etc.).

I have seen several 10 -code charts but some

numbers are not listed. Where do I get the whole

list from 10 -1 to 10 -100?

-S. D. G., Fort Stockton, Texas

All of the possible numbers are not used. The

official police and fire 10 -code has been enriched

by CBers and new numbers are not necessarily

used by everyone. Why not settle for the num-

bers you have? If you embellish it, recipients

may not know what you are trying to say.

Seeking Schematic

Where can I get a schematic of a Lear RM-

402C receiver? -B, C., Tullahoma, Tennessee

Try writing to Lear Jet Corp., 13131 Lyndon

Avenue, Detroit, Michigan or Motorola, Inc.,

4501 West Augusta Blvd., Chicago, Illinois,

°ch bought up Ianr'c evinnicc business.

Color TV `Acting -up "?

Learn How To Adjust Your

New Color TV Set!

Save money too!

Avoid the expense of calling a repairman

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recorder, kiddie phono, fm tune, stereo

system and ac /dc radio. These and many

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MARCH- APRIL, 1967 23

ELEMENTARY

EI,ECTRONICS

ETYMOLOGY

By Webb Garrison

t7 ©O ©O G ®O

Magnet

A Magnesia ad Maeandrum -or Magnesia on

the Maeander -was built near the mouth of a

famous river in Asia Minor. Until its destruc-

tion by the Cimmerians about 700 B.C. the city

was an important center of commerce and art.

But it was best known as the source of a

queer type of heavy mineral that ancients found

to be endowed with special power. Known to

the Greeks as Magnetis, from the city of its

origin, the potent stuff could draw iron to itself.

There was no practical use for it until, cen-

turies later, someone discovered that the nature

of a- needle was changed when it was rubbed

with stone from Magnesia. Arranged so that

it could swing freely, such a needle always

pointed to the north.

Makers and users of the compass found that

magnete, as they called the power -conferring

mineral, occurred not only in Turkey but also

in many other regions. It was long taken for

granted by seamen that a huge mass of the stuff

formed an "Ilande of Magnete" located under

or near the north pole and responsible for the

tug on a compass needle. In one of his bursts

of fancy Milton wrote of an imaginary white

city surmounted by a castle built of magnet.

Natural magnets varied greatly in power and

quality, so had few applications other than in

making crude navigational instruments. But

with the development of the electromagnet sci-

ence and industry found a versatile and reliable

tool. Today magnets are made in shops and

plants all over the world -but none come from

the site of ancient Magnesia.

Geiger Counter

A After a brilliant career as a student Hans

Geiger became an assistant to the great Sir

Ernest Rutherford. Together the men made

early experiments with alpha particles. Ruther-

ford developed the theory of the atom and won

a Nobel prize; Geiger concentrated on perfect-

ing a radiation counter.

By 1908 he was successful with alpha par-

ticles. He then turned to study of beta -ray

24

activity. This work was done in close collabo-

ration with W. Müller. Together the scientists

succeeded in making a gas -filled tube with cylin-

drical cathode and axial wire anode. Ionized

particles that penetrated the envelope of the

device set up momentary current pulsations in

its gas. This Geiger -Müller tube found numer-

ous important uses. Linked with other com-

ponents it proved capable of measuring radia-

tion intensity with great accuracy.

Though Müller spent years on the project

and made vital contributions to it, the combi-

nation of two German names was too much.

A few authorities still prefer abbreviation and

speak of the GM counter, but in living speech

such tribute to the scientific partnership has

vanished. Specialists and beginners ignore Mül-

ler's role and speak of the Geiger counter.

Battery

A In the language of medieval France battre

was used as a verb of action to name the proc-

ess of beating repeatedly with hard blows. Mil-

itary leaders were positively ecstatic when the

development of cannon gave them a new and

powerful means of beating down the walls of

an enemy city or fortress. So from the old

term for such action they called an artillery

unit a batterie.

Many a batterie played a decisive role in

battle. Since such a unit included from 2 to 6

guns, fired in sequence, its name attached to

various kinds of coordinated groups of things

and persons. Among these was a favorite toy

of early electrical experimenters: panes of sash

glass armed with thin lead plates and arranged

in precise order. Properly wired and activated

by acid, such a device would yield a steady flow

of electricity.

He probably borrowed the name from other

amateurs who used it earlier, but Benjamin

Franklin was one of the first to write about

work with an electric battery. His crude one

actually preserved the pattern of ordered se-

quence that marked an artillery unit. But many

of today's batteries have little if anything in

common with a row of cannon trained on a

target and set to fire in order.

11111.1,111 11

JEW

o tii3>

-_

: 111111111111111111,:

ELEMENTARY ELECTRONICS

E\ PASSANT

BY JOHN W. COLLINS

17OO=1l7C-OOOI]

Chess, like ancient Gaul. is divided into

three parts -the opening, the middle game and

the ending. And the proper method of studying

it is to consider each of these parts separately.

James Mason, author of "The Art of Chess,"

wrote in 1898 that "For want of method -right

method -even much study may prove vain."

He observed that chronologically the opening

comes first, but logically, in study, it must come

last and he posed the question: "If you do not

know what to do with three pieces, what about

thirty- two ?" So it is that most modern books

which cover the three parts, as well as those

devoted exclusively with the ending, begin with

a discussion of the ending and the elementary

mates.

A Royal Pair. The most common and the

easiest of the elementary mates is that of King

and Queen against King. The stronger side can

always force checkmate, from any position, in

ten moves at most. From the diagram position

below White wraps it up with-

Black

White

1. K-N2 K-Q4 4. K-04 K-B6

2. K-B3 K-K4 5. Q-N5 K-B7

3. Q-KN6 K-B5 6. Q-N4 K-K8

How Bad Is

Highway

Hi -Fi?

Car cartridge tape players are rapidly becoming the

hottest item to hit Detroit since the compact car. Yet,

how effective can they actually be? For a surprising

and informative answer read the Feb /Mar issue of

RADIO -TV EXPERIMENTER.

EASY TO LEARN ELECTRONICS

If you're at all interested in electronics -whether you

take it seriously or not -RADIO -TV EXPERIMENTER

is bound to make this fascinating subject a lot easier

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MARCH -APRIL, 1967 25

EN PASSANT

7. K -K3 K -B8

8. 0-N7 K -K8

9. 0-N1 Mate

Usually it is accomplished in fewer moves.

White's only problem is to avoid stalemates

(draws).

One More. The next easiest of the elementary

mates is that of King and Rook against King.

And the mating process is similar and as follows:

Black

White

1. K-N2 K-05 8. R-N5# K-R5

2. K-B2 K-K5 9. K-B4 K-R6

3. R-N5I K-05 10. K-B3I K-R7!

4. K-N3 K-K5 11. R-N8 K-R8!

5. K-B3 K-85 12. K-B2 K-R7

6. K-Q3 K-N5 13. R-R8 Mate

7. K-K3 K-N6!

In both these endings the dominant idea is

to gradually force the helpless King to the edge

of the board.

French Defense. In my previous column I

presented four miniature games and mentioned

"The 1,000 Best Short Games of Chess" by

Irving Chernev. On page 396 of that book is a

short short I won. I played Black and my oppo-

nent was Frutsaert of Belgium. It occurred in

the 1948 World Correspondence Chess Cham-

pionship and the opening was a French Defense.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

P-K4 P-K3

P-04 P-04

N-02 N-0B3

KN-B3 N-B3

P-K5 N-02

P-B4 P-B3

BPxP KPxP

B-N5 PxP

NxP 0-B3

N/2-83 B-N5#

B-02 BxB#

QxB 0-0

BxN PxB

14. R-0B1 P-B4!

115. NxN BxN

16. RxP? Q-KN3!

17. K-B1 RxN!

18. PxR B-R6#

19. K-K2 R-K1 #

20. K-01 B-N7!

Resigns

Position after 20 . . . B -N7!

1 I I

í

,VA

/%,

' "'.

/ / g

Why did White resign? Because he cannot

defend against Black's mating attack, combina-

tion to win the Queen and threats to the King

Rook and King Bishop Pawn. Here is the

analysis - A. If 21 R -NI (the King Rook cannot be

abandoned) BxP# 22 K -B1, QxR# 23 K -B2,

R -K7 wins the Queen.

B. If 21 R -K1, Q -N8# 22 R -B1, BxP# 23

R -K2, Q -K5! 24 R -B2, BxR# 25 QxB (or 25

K -B1, Q -R8# 26 Q -K1, QxQ mate) Q -R8# 26

K -Q2, RxQ# 27 KxR, Q -K5# 28 K -Q2, QxP#

and wins with a Queen and Pawn against a

Rook.

C. If 21 R -K1, Q -N8 #! 22 Q -B1, Q -Q6#

23 Q -Q2, RxR# 24 KxR, Q -B8 mate.

With no time -clock ticking away at your el-

bow, as it does in over- the -board tournament

chess, one has plenty of time to work out every

last detail in this branch of the game.

This one fitted my "Why did White resign ?"

format. And every once in a while a writer

feels justified in publishing one of his own

games -if for no other reason than to let the

reader see he can play as well as edit.

Problem. The problem this month is an orig-

inal one, never published before. It is composed

by Master Sidney Bernstein of Brooklyn, N. Y.,

Problem 5.

By S. N. Bernstein

Black

' j i-i "e

,, } ,,,,. }

%*..fiii S '.%i1f,"..

j

j j j j

j j j White

White to move and mate in two.

Solution in next issue.

4

26 ELEMENTARY ELECTRONICS

former champion of the Manhattan and

Marshall Chess Clubs. He quips it is his

"sole and immortal masterpiece." It has an as-

tonishing key move and a rich variety of mating

variations.

Solution to Problem 4: 1 Q -08.

More on this later.

After the signal has been reduced to the

required level it goes to another voltage am-

plifier (Q3) followed by an emitter -follower

(common -collector) stage. (Q4) used to

provide low output impedance. Here a

small part of the signal is used as an AGC

voltage -it is rectified by two more diodes,

(D5, D6) and filtered so the AGC stage re-

sponds to average (not instantaneous) voice

levels. Following the filter is the DC ampli-

(4)1N207

D8

fier which controls the current flow through

the diode attenuator -thus controlling the

signal attenuation.

With a very weak audio signal, very little

signal voltage is present to be rectified and

passed to Q5 (the DC amplifier) so it is al-

most cut off and very little current flows

through the diodes. This increases their ef-

fective resistance so the weak signal into the

diode attenuator passes through with very

little attenuation.

On the other hand when a large signal is

present more voltage is rectified and the

DC amplifier (Q5) conducts and much more

current flows through the diodes greatly low-

ering their effective impedance. Now this

large signal entering the diode attenuator is

greatly reduced in level. So the average out-

put level of the Speech Processor going on

12a V

4 C16

500MF

EVAC N.C.

Power supply circuit diagram can fool you. It looks like a normal transistor power supply but voltage from col-

lector of Q6 is 150 volts. Unit can be hooked to mobile rig if you can get 150 volts somewhere.

,,,.,,, ,.:.,,I,IIII111111,11111111111111111111111111111,1111111111111111,1111IIIIIIIIII.III1111111111111111$11111111 011111011111g

SPEECH PROCESSOR PARTS LIST

Cl, C9, C10- ,02 -mf, 150 -volt disc capacitor

C2- .005 -mf, 150 -volt disc capacitor

C3, CI1, C12 -5 -mf, 25 -volt electrolytic ca-

pacitor

C4- ,05 -mf, 150 -volt disc capacitor

C5- ,1 -mf, 150 -volt disc capacitor

C6-1 0-mf, 25 -volt electrolytic capacitor

C7, C8- ,1 -mf, 75 -volt disc capacitor

Cl 3-100-mf, 3 -volt electrolytic capacitor

C14, C15- 16 -mf, 150 -volt electrolytic

Cl6- 500 -mf, 50 -volt electrolytic capacitor

D1, D2, D3, D4, D5, D6, D7 -1N461 silicon

diode

D8, D9, D10, D11- Silicon diode, 1N207,

1N1694 or equiv.

J1, J2 -Jack, 2- conductor shielded (to suit

builder)

01, 03, Q4, Q5 -npn transistor, 2N1304,

GE -5, SK3011, or equiv.

02, 06-npn transistor, 2N3712, or equiv.

R1- 330,000 -ohm, 1/2 -watt resistor

R2, R15- 100,000 -ohm, 1/2 -watt resistor

R3, R13, R16, R17, R20, R27- 10,000 -ohm,

1/2 -watt resistor

R4, R26 -100 -ohm, 1/2 -watt resistor

R5, R23, R30 -4,700 -ohm, 1/2 -watt resistor

R6- 50,000 -ohm, 2 -watt potentiometer

R7- 680,000 -ohm, 1/2-waft resistor

R8, R9- 22,000 -ohm, 1/2 -watt resistor

RIO, R12, R24- 1,000 -ohm, 1/2 -watt resistor

Rl 1- 47,000 -ohm, 1/2 -watt resistor

RI 4-2,200,000-ohm, 1/2 -watt resistor

RI 8-I0,000-ohm, 2 -watt potentiometer with

s.p.s.t. switch (52)

R19 -1,500 -ohm, 1/2 -watt resistor

R21- 100,000 -ohm, 2 -watt potentiometer

R22- 100,000 -ohm, 2 -waft potentiometer

R25- 1,000,000 -ohm, 1/2 -watt resistor

R28- 82,000 -ohm, 1/2 -watt resistor

R29- 8,200 -ohm, 1 -waft resistor

R31 -270 -ohm, 1/2 -watt resistor

S1- S.p.s.t. slide switch

S2- S.p.s.t. switch (part of Rl 8)

53- D.p.s.t. slide switch

T1- 125 -volt, 15 -ma secondary, power trans-

former (Stancor 8415, Knight 612410 or

equiv.)

1 -3 x 4 x 5 -in. utility cabinet -see text (Bud

AU1028 or equiv.)

Misc. -Pilot light assembly (optional) perfo-

rated phenolic board, machine screws, nuts,

knobs, line cord and AC plug, wire, solder,

etc.

Estimated cost: $22.00

Construction time: 6 hours

52 ELEMENTARY ELECTRONICS

to the transmitter remains almost constant

regardless of input variations.

From the emitter follower the remainder

of the signal goes to the speech clipper (D3,

D4) which, with S2 closed, clips off the un-

desirable, low- energy speech peaks. From

here the signal goes to the treble cut con-

trol (R21) which removes the speech -fre-

quency harmonics produced in the clipper

and controls the high- frequency response

from 5 kHz down to about 2 kHz. The

signal then continues to the level or modula-

tion control (R22) which sets the correct

level or amplitude to suit the particular

speech amplifier and modulator used.

Construction. The Speech Processor can

be built quite easily on two pieces of per-

forated- phenolic circuit board, the power

INPUT

This simplified partial schematic of diode attenua-

tor uses some part ca//outs as in main schematic dia-

gram. Voltage across diodes is controlled by Re. C15

supply on one and the audio circuits on the

other. Due to the high gain, the input and

output leads and all signal leads going to

controls should be shielded with the shield

grounded on one end. The input stage should

be well separated from the output stage and

all signal leads must be as short as possible.

To avoid overcrowding, place components

on both sides of the board. After completion

of both boards "hay wire" in required con-

trols and check for proper operation. First

check both power supply voltages. Be sure

of power supply, electrolytic capacitor and

diode polarities. The voltage measured at

each transistor collector (except emitter fol-

lower and DC amp) should be approximate-

ly half that measured between ground and

supply -voltage point. If any stage is corn-

C16

Bottom view of the power supply shows location of

most of the components. If more expensive, smaller

filter capacitors are used there will be more room.

MARCH -APFIL, 1967

Reverse side of power supply shows single transis-

tor, Q6. Transistor socket is not really needed;

Q6 could be soldered right into circuit by leads.

pletely on (collector at ground) , or ofi,

(collector at supply voltage), recheck wiring

and capacitor polarities. If all DC potentials

seem normal connect a microphone or audio -

signal generator to the input (J1) and follow

the AC voltage through each stage. It should

reach its highest peak -to -peak level in the

second or high -level amplifier stage, and fi-

nally the output level at J2 should be slightly

53

54

(gg SPEECH PROCESSOR

larger than the audio input level at J 1.

Change the level at the input (by shouting

into the microphone or upping the signal -

generator output voltage). The output should

increase momentarily then fall quickly to

the original value. if not, check closely the

circuits associated with the DC amp and

rectifying diodes.

When all seems well, mount the two circuit

.

AGC

MAN

AGC

PATE

MAN JAI

GAIN

HIGH

GAIN

LOW

Packaging can be o problem if

you use standard -sized parts to

wire the Speech Processor. Use

miniature components wherever

possible. Since current is no

problem use AWG -22 or AWG -24

wire -use stranded wire for all

connections between subchassis

and panel mounted controls, etc.

Miniature components will boost

the price considerably unless you

shop carefully. All five of the

transistors on the other side

of this subchassis can be wired

directly into the circuit. The

main reason for the sockets was

to make substitution easier -to

test many transistors in circuit.

boards in a suitable metal box. Builder's skill

and amount of money spent for electrolytic

capacitors will determine the final size (small

capacitors are more expensive). The author's

was installed in a 3 x 4 x 5 -inch cabinet, how-

ever, a somewhat larger box, such as a 5 x

7 x 3 -inch would have less crowding and a

bit easier final construction.

(Continued on page 114)

Rear panel of Speech Processor (left) shows location of the least used circuit adjustments. Use miniature

switches and controls wherever possible. Actually all controls, including those on front panel (right) could

be screwdriver adjustments or locking -type potentiometers since none of the controls are varied constantly

-once set they need not be changed again.

ELEMENTARY ELECTRONICS

SSB is ins

By

Len Buckwalter

KIODH /KBA4480

eliminating the nonessential, power -

omponents in the AM signal, range is

sed- making efficiency much higher.

A sk a CBer what he wants most. "More

range," might be the reply. Or query

a Ham on his secret wish. "Bigger band, less

QRM," could be the answer. And you might

ask a communications engineer, "What's

your innermost craving ?" His possible an-

swer, "More efficient radio -frequency pow-

er." Put together those wishes for slim, but

booming signals and they'd all be answered

by SSB ... single sideband.

This single -sideband system of radio trans-

mission does all those things and then some.

Surprisingly, it wasn't ushered in by the

space age, solid -state or some last- minute

breakthrough. SSB is nearly as old as high -

button shoes and, until recent years, con-

sidered too mysterious for all but commercial

communications. Today, single sideband has

been snapped up by the military, is em-

braced by Ham radio and soon may invade

the Citizens Band.

Single sideband is to AM, or amplitude

modulation, what the car is to the horse and

buggy. Both get you there but one is quaint,

the other cool and efficient. As we'll see,

single sideband is actually a sophisticated

form of AM, but one that squeezes each

watt for all it's worth. Sideband can whip a

conventional AM signal of 100 watts into

sounding like 800.

Conditioning by Carrier. As far back

as 1914 it was suspected that a radio wave,

when modulated by voice, was not one but

three distinct signals. The regular AM signal

had been shown as a single signal; a radio

carrier whose strength changes with audio

information. That conventional "envelope"

pattern is in Fig. 1. An audio signal from the

MARCH-APRIL, 1967

microphone is strengthened in the audio am-

plifier, then is applied to the RF amplifier

(in the transmitter) where it meets the steady

carrier.

At this common meeting point, the modu-

lator, audio voltages aid or oppose the car-

rier during modulation with the result shown.

It's a convenient picture that provides a re-

assuring explanation of what happens during

amplitude modulation. If the audio signal is

1 kHz (kc) (a high -pitched tone) then carrier

strength varies 1000 times per second.

But a patent issued in 1923 destroyed the

one -signal concept. As the first practical SSB

system, it contended that an AM signal

should really be considered in three parts.

And the claim was backed up by the first

successful SSB transmission between the

United States and England -about 22 years

after Marconi made the first transatlantic hop

between the same countries. Here's what the

new image of AM looked like.

In Fig. 2 is the triple signal, based on a

radio carrier of 600 kHz modulated by an

audio tone of 1 kHz. (This would be roughly

equal to conditions existing at the moment

AM

TRANSMITTER

AMPLIFIER

RF

(MIC

LJ"

t

AUDIO

AMP

STEADY RF AMPLITUDE CHANGE

CARRIER DUE TO AUDIO

1111111111i11111111111111 1 1111111 I

IIIIIIT11111111I1 II 11111111

Fig. Conventional picture of AM signal shows

modulated RF output as varying envelope pattern. Buf

output from transmitter is actually in three parts.

55

SSB IS IN!

you're hearing a time signal sounded by a

station in the standard broadcast band.)

Most shattering feature in the waveforms of

Fig. 2 is how the carrier in the middle ap-

pears. It bears not the least trace of modula-

tion! The carrier is as smooth as a bag of

mortar left out in the rain. It never changes

amplitude by one whit. The audio signal can

be found in two sidebands which lie just

above and below the carrier frequency. These

RF

AMPLIFIER

(600 kHz)

AUDIO

AMP

(1kHz)

AINFAVAIVAIII/

VARYAVAIRV

UPPER SIDEBAND

601 kHz

Typical SSB rig (this is an E /CO Ham trans-

mitter) incorporates Mode switch to enable

operator to select CW, AM, or SSB operation at

will. Finger points to knob labeled "Carrier

Bal which serves as fine- tuning adjustment

of modulator stage to eliminate RF carrier.

CARRIER

600 kHz

LOWER SIDEBAND

599 kHz

sidebands deserve close inspection.

When the audio tone (1 kHz) combined

with the carrier (600 kHz) in the transmitter,

a mixing process occurred in the RF ampli-

fier. As audio and radio frequencies beat

against each other, they formed carrier -plus-

audio and carrier -minus -audio frequencies.

That creates the two sidebands, an upper one

at 601 kHz, a lower sideband on 599 kHz.

This may also be recognized as the hetero-

dyne process, where mixing signals add and

subtract. Thus sidebands are always spaced

from the carrier by a frequency a number

of Hz or kHz determined by the audio signal.

Modulate with voice or music and sidebands

spring further from the carrier as tones grow

higher in frequency -or move in close to the

carrier for low -pitch sounds. Again, it's due

to the frequency -mixing process.

Another View. The 3 -piece signal can

also be viewed as a collection of frequencies

strung out along a receiver dial, as shown in

Fig. 3. Let's say the dial pointer is at 600

kHz, tuned to the carrier. Since a receiver

has bandwidth -it accepts a group of close -

spaced frequencies -we pick up sidebands

just above and below 600. Each of those

sidebands represents the whole band of

modulating frequencies that might occur dur-

ing a voice transmission.

56

Fig. 2. Correct depiction of AM signal

reveals three distinct components: the original

600 kHz carrier in addition to carrier -

plus -audio and carrier- minus -audio sidebands.

Since carrier contains no information, its

transmission serves no useful purpose.

If an audio tone reaches up to 3 kHz it

generates an upper sideband on 603 kHz

(3 +600). Too, there's a mirror-image ap-

pearing at 597 kHz, the lower sideband. The

intermediate lines in Fig. 3 indicate the

product of other audio tones. One precaution

when interpreting the image is this: sidebands

are not in themselves audio tones. They are

RF signals whose frequencies are determined

by the original audio. RF remains the medi-

um which carries signals, via the antenna,

out "over the air."

If upper and lower sidebands repeat the

same intelligence, why transmit both? There

is one good reason. On arriving at the receiv-

LOWER

SIDEBAND

,SII

CARRIER

UPPER

SIDEBAND

Iil,

597 598

FREQUENCY

599 600 t 601 602 603

DIAL

POINTER

Fig. 3. Some idea of conventional AM's spectrum -

wasting properties is evident in this diagram. Note

that a 3 kHz signal fills an area fully 6 kHz wide.

ELEMENTARY ELECTRONICS

er, power from sidebands add, so two are bet-

ter than one. But there's a strong argument

against transmitting duplicates. It's available

room on the bands -which now groan under

heavy communications traffic. Wouldn't it be

better to recover the power in one sideband

and inject it into the other? This would effec-

tively halve the signal band width -and al-

most double available space in the radio spec-

trum. As we'll see, this is one significant

advantage of single sideband. There's a sec-

ond one -just as important -and it's given

in Fig. 4.

Power Down the Drain. Now you can

see how a conventional carrier wastes energy.

CARRIER = 200 WATTS

LOWER

SIDEBAND = 50 WATTS

UPPER SIDEBAND

50 WATTS

Fig. 4. A conventional AM transmitter also is

extremely inefficient with the power at its disposal,

as this diagram suggests. In the case of a 300 -

watt rig, roughly 662/3% of the total power is poured

into the carrier, which, as already noted, carries no

information whatever. Balance of power -a mere 100

watts -is split between upper and lower sidebands.

Fig. 4 illustrates how a regular 300 -watt AM

transmitter divides its power: the carrier con-

tains 200 watts, while each sideband has 50.

That's a colossal waste since carriers, as

we've noted, contain no modulation. Total

useful power -in two sidebands -is a mere

100 watts, or one -third the carrier level.

If a carrier spills two- thirds of the trans-

mitter power down the drain, why is it pro-

duced in the first place? The reason is that

an RF signal is a necessary ingredient in the

recipe for cooking up sidebands. Audio must

mix with RF, and during the conventional

modulating process watts divide into that un-

even, 3 -way split. This underlies the first step

toward the single sideband transmitter. The

SSB rig generates a carrier but a negligible

Fig. 6. One type of SSB rig

delivers two sidebands but no

carrier in what is known as

a double -sideband suppressed -

carrier hookup. As explained in

text, output signal consists solely

of a lower sideband (LSB) and

an upper sideband (USB), since

carrier cancels out in modulator.

one -at most a few watts. Once sidebands

are produced, the carrier will be rejected be-

fore it gulps RF watts further along in high -

level stages. First part of the process is done

in the balanced modulator.

Before plunging into the circuit, consider

the push -pull amplifier shown in Fig. 5. In a

normal amplifier of this type, an input signal

is applied in push -pull (the top tube grid is

driven positive as the lower goes negative).

But the input signal in Fig. 5 is being applied

equally to both grids, or in a parallel connec-

tion. Both amplifier tubes commence to con-

duct. Since the output transformer is split by

a centertap, two magnetic fields are created.

SIGNAL APPLIED

IN PARALLEL + NO SIGNAL

OUTPUT

Fig. 5. Properly balanced push -pull amplifier

cancels in -phase (or parallel) signals, which explains

need for phase inversion in push -pull circuits.

SSB rigs utilize this property to cancel out carrier.

The interacting fields, however, are opposite

and cancel each other. The upshot is this:

whenever you feed in parallel, but extract in

push -pull, there'll be no output signal since

it's phased out. But feed and extract in push -

pull (as done in a hi -fi output stage) and full

amplification occurs. Both parallel and push -

pull can be used in the balanced modulator to

produce a sideband signal.

Begin with an audio signal and apply it to

the input side, as in Fig. 6. This signal will

enter in push -pull since it rides through an

input transformer whose secondary winding

is center -tapped. Since the output side is

similarly arranged for push -pull operation, it

can be assumed that audio input will not

cancel. (Turn page)

AUDIO INPUT

TRANSFORMER

BALANCED

MODULATOR

RF INPUT

- TRANSFORMER

AUDIO APPLIED

IN PUSH -PULL

RF APPLIED

IN PARALLEL

OUTPUT

ILSB USI

J ,

CANCELLED

OUTPUT CARRIER

TRANSFORMER

MARCH -APRIL, 1967 57

58

SSB IS IN!

Meanwhile, a steady carrier signal is also

applied to the tube grids. But since the RF

input transformer has no centertap, an equal

(parallel) signal drives the tube grids. Steady

RF, therefore, always cancels on the output

side. Now start talking into the microphone.

As the audio signal drives the top grid posi-

tive, it drives the lower grid negative. During

this moment, the RF signal doesn't encounter

the same conditions (tubes balanced), as

when no audio was present. Audio voltage

has unbalanced the tubes and RF can flow

during this time with no cancellation at the

output. A similar condition also exists when

audio reverses and drives the lower grid neg-

ative. Thus the audio signal continuously varies

bias and upsets tube balance. The net result is

an RF signal at the output side which varies at

an audio rate -the familiar modulation en-

velope pattern. And since there has been a

mixing process between RF and audio, the

RF output signal consists of upper and lower

sidebands.

Note in Fig. 6 that the carrier (steady RF)

doesn't appear at the output. The output

signal, consisting of upper and lower side -

bands), is known as double sideband sup-

pressed carrier.

Eliminate One Sideband. A system for

slicing off a sideband utilizes the crystal

filter (see Fig. 7). The crystal forms an ex-

tremely selective tuned circuit just a few

- 601

DOUBLE SIDEBAND SIGNAL OUTPUT

(FROM BAL,MODULATOR)0 1.11 SSB SIGNAL

CRYSTAL ON 601 kHz

601

599

PHASING

.CAPACITOR

Fig. 7. Crystal filter affords one method of dumping

one sideband, passing the other. Here, crystal passes

signal on 601 kHz, rejects signal on 599 kHz. Once

adjusted, crystal performs function indefinitely.

kHz wide. Placed in the path of the double -

sideband signal, it acts as a sharp, series -

resonant circuit with little opposition to one

of the sidebands. The unwanted signal is

attenuated.

Another popular method uses the me-

chanical filter. It is a series of mechanically

resonant metal disks, as shown in Fig. 8.

4,011.1 N s

MrNANIC4t FILTER

Fig. 8. Mechanical filter also is found in many SSB

rigs, since its ability to pass only one of two side -

bands can be as good as (if not better than)

that of quartz crystal. Principle is that of tuning fork.

Both sidebands are applied to the mechanical

filter and their voltages converted to me-

chanical movement (via an electromagnetic

coil and rod). This spurs the disks into ac-

tion. Since resonant motion can occur only

over an extremely narrow range of frequen-

cies, the undesired sideband signal cannot

slither through. At the output end of the

mechanical filter is a second coil -and -rod

assembly to convert the mechanical signal

back into electrical energy. Both crystal and

mechanical filters are not only far sharper

than coil- capacitor (L -C) combinations, but

are smaller, very stable and require virtually

no adjustment.

Phasing. There are other sideband tech-

niques. We've been describing the filter sys-

tem but there's the phasing system, too. Since

it is somewhat more critical to set up and

keep in adjustment, the phasing approach

seems to be less popular than the filter in

much of the presently used circuitry. The

phasing technique takes audio and RF signals

then splits each into two parts in suitable

phasing networks. The four signals are then

recombined in two balanced modulators

where they add and subtract. All undesired

mixed signals cancel; the wanted sideband

emerges.

Another variation is the type of balanced

modulator circuitry selected by the single -

sideband transmitter designer. As we've

described it, a double -sideband signal is pro-

duced by a type of push -pull amplifier.

There's also a "bridge" balanced modulator,

seen in Fig. 9. Again, there are two inputs-

one for the RF carrier and one for audio.

The carrier, however, is suppressed when no

audio signal is present since it produces equal

RF voltage across bridge points A and B.

(For current to flow there must be a voltage

nLEMENTARY ELECTRONICS

AUDIO IN

RF CARRIER IN

DOUBLE

SIDEBAND

OUTPUT

Fig. 9. Still another technique for suppressing a

carrier relies on a bridge balanced modulator. Both

AF and RF are fed into bridge, but circuit cancels

carrier, allowing only two sidebands to emerge.

difference between "hot" and ground sides of

the circuit.) At this time the bridge is in

balance.

When audio is applied across top and bot-

tom, the bridge becomes unbalanced. For

example: when the audio cycle is positive,

diodes 2 and 3 are biased to conduct, while

diodes 1 and 4 are reverse biased (no cur-

rent flows). This upset in the bridge enables

RF voltage to develop at the output -at an

audio rate. Thus the double sideband signal

results.

Still another technique is the balanced

modulator which produces signal mixing in

the multigrid structure of a tube. Here audio

and RF combine within the tube's electron

stream, but the underlying concepts are the

same. Consider the status of the single sideband

generated by the balanced modulator and

filter. It is superior to the conventional AM

signal since it occupies half normal band-

width; it's about 3 kHz wide instead of 6 kHz.

And if the SSB signal is now applied to an

RF amplifier, only pure intelligence -not

useless carrier -is boosted to desired output

wattage. But there are further steps before

that efficient signal can ride off an antenna.

SIDEBAND

SELECTOR

SWITCH

LOWER

CARRIER

OSCILLATOR

455 kHz

UPPER

1

II

BALANCED

MODULATOR

LSB USB

1) 455kHz 455

CARRIER kHz

OSC

COIL

8+

AUDIO

The SSB signal is developed at low power

levels in the transmitter, not more than a few

watts. In fact, it is usually handled in tubes

commonly found in receivers. But there's

another low -level feature in sideband genera-

tion. It's frequency. For a sideband filter -

crystal or mechanical -to operate with high

sharpness and selectivity, operating frequency

must be low. Usually filtering process occurs

at less than about 6 mHz. Thus a sideband

signal must undergo a shift to the desired

final frequency. In a Ham rig, for example,

single sideband output may be needed on one

of the popular bands in the 3.5, 7, 14, or 28-

mHz range.

Conventional transmitters increase fre-

quency with multiplier stages. An RF ampli-

fier tube is strongly driven by an input signal

until it produces distortion in the form of

harmonics, or frequency multiples. That ap-

proach works well in regular AM transmit-

ters since only the RF carrier signal is

distorted. This doesn't matter since it bears

no intelligence during the frequency- multi-

plying step. The audio modulation is tacked

on at the final RF amplifier and thus escapes

distortion. Multipliers, however, would de-

stroy a sideband signal. To preserve its audio

envelope, the sideband signal must be hetero-

dyned up or down to the final operating fre-

quency. The mixing step will appear as we

trace the simplified diagram of a complete

SSB transmitter.

The Transmitter. In Fig. 10 there is a

block diagram of a transmitter which in-

cludes operating features like selectable side -

bands and continuous tuning. Tracing the

signal paths begins at the left, where the

carrier is initially generated. It's simply an

2ND MIXER

1ST MIXER \ LINEAR _TNT

LSB 1 \i AMP

1 S ; + 3800- 4000 kHz - - - - --

MECHANICAL

FILTER

TUNING

3345-

3545 kHz

T

VFO

Fig. 10. Block diagram of a basic SSB transmitter. Unlike conventional AM transmitters where audio is

injected at the final, SSB rigs insert audio comparatively early. Mixers therefore replace multipliers in circuit.

MARCH- APRIL, 1967 59

(/ssB IS IN!

oscillator which generates a low -level RF

signal at 455 kHz -a popular frequency

since it can use the IF transformers manu-

factured for standard AM receivers. Found

in this stage is the sideband switch. By

selecting either of two capacitors, oscil-

lator frequency can be changed a small

amount. Further along the circuit, this shift

will determine which sideband is picked up

by the mechanical filter.

Next major stage is the balanced modu-

lator which receives carrier and audio signals.

As already described (Fig. 6), its output is a

double -sideband signal with the carrier sup-

pressed. The single -sideband signal appears

after the next stage -the mechanical filter.

Although the filter is nominally rated for 455

kHz, the important figure is its bandwidth.

In this case, the filter's "opening" is stated as

3.1 kHz by the manufacturer, equivalent to

the span of frequencies contained in one side-

band. Back in the carrier oscillator, the side-

band selector shifts the carrier just enough so

the desired sideband lines up in the passband

of the filter. Thus the operator may choose

upper or lower sideband. Output of the me-

chanical filter is a lower sideband signal nomi-

nally on 455 kHz.

Next is the mixing process. We'll trace how

the 455 -kHz sideband is heterodyned up to

the 75 -meter amateur phone band (3.8 -4

mHz). The mixer receives the 455 kHz side-

band signal at its control grid, and a mixing

(RF) signal on its screen. That second RF

signal arrives from the VFO (variable fre-

Practical example of crystal filter is seen on

subassembly in SSB rig. Four crystals (in center)

insure sharp response at desired bandwidth, two

IF -type transformers (one at either end of board)

serve to match filter to associated circuitry.

60

quency oscillator) stage. The two signals add

in the mixer and output is on the desired

operating frequency, as shown. Note that

the operator can change output frequency by

tuning the VFO. Shown, too, in Fig. 10 is a

second mixer stage. By subjecting the signal

to further mixing, output on other bands is

obtainable.

To beef up the single -sideband signal, it is

fed to a final RF amplifier. Here again circuit-

ry differs from that of a conventional AM rig.

Regular CW and AM transmitters utilize a

Class -C output amplifier, the type that's most

efficient, but one that creates greatest distor-

tion. Distortion is no problem in regular AM

Many sideband rigs employ fixed crystal oscillator

for heterodyning signal to desired frequency (rod

points to crystal associated with mixer in this unit).

since modulating audio is applied only at the

plate of the output stage, and doesn't ride

from grid to plate. But in SSB, a final ampli-

fier must preserve the envelope pattern since

the grid signal contains audio intelligence.

For that reason, the final stage for single

sideband is a linear amplifier. By reducing

grid bias on an RF amplifier it operates at

somewhat less efficiency (Class B) but im-

parts little distortion to the modulated signal.

When you first see specs on a linear ampli-

fier for Ham or CB radio, you may be in for

a surprise. It's often rated at twice the legal

wattage (2000 for Ham, 10 for CB). That's

because linear amplifiers are not measured in

the same fashion as their conventional Class

C cousins. In the regular AM rig, wattage is

determined by measuring steady carrier pow-

er. Since the sideband signal has no carrier -

signals are always rising and falling in step

with modulation- ratings are given as PEP,

or (Peak Envelope Power) . This describes

power developed when a steady tone drives

the amplifier to its maximum rated output.

Since this only happens during modulation

(Continued on page 116)

ELEMENTARY ELECTRONICS

Simple regulated power supply can be wired for either 6- or 9 -volt

output that's more stable than common transistor batteries.

Six -volt output can be obtained by simply

changing two components, R2 and D1,

though you may also make this a dual volt-

age supply by switching between the 6- and

9 -volt R2 -D 1 components.

Ripple. If you're working with a high -

level audio amplifier most of the power -

supply filtering you'll need is built into the

Six -or- Niner. Maximum AC ripple -the AC

component of the output DC -is 4 milli-

volts. About 100 mf connected across the

supply's output or built into the project will

give you no -hum, practically pure DC -but

generally you won't need the extra filtering

as 4 millivolts ripple is quite low.

Since the Six -or -Niner is intended for ex-

perimenters -and things do go wrong with

experimental projects -there is full protec-

tion against short circuits. Resistor R1 acts

both as a fuse (protecting against long -term

overload) and as a voltage limiter against

shorts. The normal output of the supply is

intended for up to 500 ma. Current in excess

of 500 ma will cause the resistor to burn up,

thereby protecting the transistor, diode D1

and Ti. In addition, in the event of a short

circuit somewhere in the project connected

to this DC supply, the entire output voltage

will be dropped across R1, thereby protect-

ing the experimental project in addition to

the power supply.

How It Works. Transistor Ql, which is in

'n this solid -state age, most moderate- to

high- current experimenter projects use 6

or 9 volts as the power source. Projects run-

ning above 9 volts usually are low- current

devices and a battery will last months and

months. Down on the other end, the very-

low- current itsy -bitsy projects, so favored by

elementary and junior high science teachers,

operate for what seems like months and

months on a flashlight or Number 2 dry cell.

It's six and nine volts that break the ex-

perimenter's back. A 20 ma device will get

by on a Z4 battery, but you can't squeeze

out l ampere into a 3 -watt amplifier -it

takes but minutes to kill a buck- and -a-

quarter battery.

Regulation. If you're an experimenter,

why not avoid the whole battery problem

with the Six- or -Niner regulated power sup-

ply? This inexpensive job (see schematic

diagram and parts list) will supply about

9.4 volts (the voltage of a fresh battery) at

currents from 0 to 100 ma. with a regula-

tion of 0.2 volt. This means that whether

your project draws 1 microampere or 100

milliamperes, the maximum variation of the

Six -or- Niner's output voltage will be 0.2 volt.

Maximum output is 500 ma (0.5 ampere),

and the regulation from 0 to 500 ma is, at

worst, 0.4 volt. That's better regulation than

you can get from transistor batteries rated

at 6 or 9 volts.

MARCH -APRIL, 1967 61

®I® EXPERIMENTER'S SIX -

OR-NINER

series with the power source, functions as a

variable resistor whose value is determined

by the base bias -in relation to the collector

and emitter voltages. The base bias is

clamped at about 9.1 volts by Zener diode

Dl. If the voltage at the emitter of Q1 at-

tempts to fall (go more positive), which may

be caused by a sudden surge in the load on

the power supply, the base -to- emitter voltage

becomes more negative and the collector

current increases. An increase in collector

current through Q2 is caused by the reduc-

tion in collector -to- emitter "resistance."

When emitter -to-collector resistance is re-

duced, the voltage drop across Q1 is also

reduced and the emitter voltage rises to the

rated value of the Zener diode (D1) in the

PARTS LIST

IC1- 500 -mf, 25 -volt electrolytic capacitor

C2- 100 -mf, 12 -volt electrolytic capacitor. See

text.

D1 -Zener diode, 6.2 -volt (Motorola HEP103

or equiv.).

9.1 -volt (Motorola HEP104 or equiv I. See

_ text.

Q1 -Power transistor, pnp (Motorola HEP230

or equiv.). See text.

R1-4.7-ohm, 1 -watt resistor, 10 %

R2- Select value to match D1. 1200 ohms for

6.2 Zener diode or 560 ohms for 9.1 volt

Zener diode. See text.

T1- Filament transformer, 12.6 -volt (Knight

54A -1420 or equiv.) i

Z1- Bridge rectifier, encapsulated (Motorola

HEP175). See text.

Misc.- Perforated phenolic hoard, push -in ter-

minais, machine screws and nuts, wire, sol- t

der, aluminum for heat sink /mounting broc- 3

+i

ket, etc.

i

117

Estimated cost: $6.99

Construction time: 2 hours

VAC

o

62

R1

Bracket to mount Q/ is also a heat sink fo keep down

cose temperature of the power transistor. Actually

no heat sink is needed since maximum current is only

S00 milliamperes -a voltage drop of 6 volts, maximum.

base circuit. The same effect takes place

when the collector voltage falls below that

across the Zener diode.

If the emitter or collector voltages attempt

to increase, the effective base bias appears

more positive (less negative) and the effec-

tive resistance of Q1 increases until the volt-

age drop from emitter -to-collector has re-

stored the output voltage to the rated value

of the Zener diode.

Construction. The model shown in the

photos is assembled on a section of perforat-

ed circuit board approximately 334 x 43/4

inches; use the closest size you can cut from

a stock size perforated phenolic board.

Push -in terminals or flea clips are used for

tie points. Assemble the power supply in the

order it's laid out on the board, starting with

diode Dl. Resistor R1 is in-

stalled under Cl, so it must be

e 95V mounted before CI is sol-

01 -_ dered into place.

C2

+ 100MF

COMMON

Z1

* SEE TEXT

Just about any regulated

output voltage can be had by

changing D1 and R2.

Increase R2 for lower- voltage

Zener diodes -decrease it

for higher -voltage diodes.

ELEMENTARY ELECTRONICS

Transistor Q 1 is mounted on a heat sink

fashioned from a piece of scrap aluminum

or a tin can. Actually no heat sink is needed

for normal service and the bracket simply

provides a mounting. Only when relatively

high current is used does Q I get even slight-

ly warm. Do not insulate Q1 from the heat

sink as the collector connection for Q1 will

be made through a solder lug at one of the

heat sink mounting screws. You get better

heat sink operation when the mica washer

is not used -it's not needed. The connections

to base and emitter leads of Q1 are soldered

directly to the transistor leads, so don't use

excessive heat. Hit the joint with a wet cloth

or damp tissue as the joint cools to remove

heat quickly.

For a 9 -volt output, R2 is 560 ohms

(10 %) and D2 is the 9.1 -volt Zener diode.

Try the Motorola HEP104 Zener diode. For

a 6 -volt output R2 is 1200 ohms (10 %) and

D2 is a 6.2 -volt Zener diode -Motorola

HEP 104. If Motorola HEP diodes cannot be

obtained locally they are readily available,

as standard stock, from Allied Radio. For

9 -volt operation C 1 must be rated, at the

least, 25 VDC and C2 is rated, at the least,

12 VDC. For 6 -volt output C2 may be re-

duced to a 6 -volt rating.

Parts Substitution. Except for the Zener

diode, and possibly bridge rectifier Z1, all

components are strictly junk -box salvage.

The exact specified Zener diodes must be

used to obtain the exact voltage. Box -type

bridge recifier Z1 is actually four diodes in

Rl

Encapsulated bridge rectifier is easily supported

by its ribbon -like leads -connections are marked.

a minature case and can be replaced with

four diodes with a 50-PIV 1 -amp rating (or

higher). The two connections from T1 are

made to the two Z1 tab terminals opposite

the mark; the (+) and ( -) DC- output

tab terminals are similarly marked. Trans-

former T1 is a 12 -volt filament type -rated

at least 1 ampere. The center tap is not used.

The filament transformer (T1) specified in

the parts list is about the lowest priced unit

we could locate. "Scrounge" if you want a

lower price. Transistor Q1 can be any me-

dium or high -power transistor -use the low-

est priced type you can obtain or whatever's

in the junk box. The Six -or -Niner uses the

Motorola HEP230 -use any equivalent.

Other than observing correct polarities

there are no special wiring precautions. Just

make certain that the positive leads of CI

and C2 and cathode of Dl -the end marked

with a white band -are connected to the

common (positive) power sup-

ply buss.

Only the basic power supply

t1 has been shown, but you can

enclose the unit in any cabinet

you choose, adding an output

meter for current and a power

on-off switch if desired. We

suggest that if a metal cabinet

is used both the positive and

negative output terminals be in-

sulated from the cabinet to pre-

vent possible short circuits to

the experimental equipment.

Dl

MARCH- APRIL, 1967

Completed unit shown here is

about half actual size. Reposition

parts for more compact layout

and you can fit power supply into

any corner of project chassis.

63

With lunch in hand and eagerness in their faces,

school children throng Hall of Science Museum. Be-

low, science enthusiasts gaze at towering rocket.

SPACE -AGE

SHOWCASE

By Ron Mitchefi

The New York World's Fair is only a mem-

ory now, but one of its very best exhibits

is still playing host to hundreds of visitors

each week. It is the Hall of Science Museum,

acclaimed from the very first days of the Fair

for its exciting appearance and outstanding

exhibits. Having escaped the wreckers, the

museum has since reopened, with an even

greater wealth of exhibits.

Admission is free, and, as our photos

show, the museum is especially thronged on

school days. The reason isn't hard to find,

for many a teacher views the museum as a

veritable space -age showcase, opening win-

dow after window on the world of today -

and tomorrow.

Even astronauts' spacesuits are available for c lose scrutiny in

this museum that touches on the whole of modern technology.

There's also a diagram to explain what each element is for.

64 ELEMENTARY ELECTRONICS

The many laws which gov-

ern our solar system are

colorfully and interestingly

exhibited in still an-

other section of the mu-

seum. Given proper prep-

aration and orientation,

science- minded youngsters

can hardly fall to profit

from their hours at

the museum.

w

too- , mate eaVS

Materials in enclosure are harmless, but

youngster carp still manipulate mechanical

hands of same type used in atomic- energy labs.

Lunch break finds boys full of talk about

the many scientific wonders they've already

observed and of others that are still to come.

MARCH -APRIL, 1967 65

Shorts, open junctions, collector -to -base leakage,

even amplification can be charted for almost any

transistor using little more than a reliable VTVM

and a little something you might call "know- how."

50 CENTTRANSISTOR

TESTER

By A. A. Mangieri

While it's nice to have a fancy transistor

checker to indicate gain and leakage, you

don't have to pass over a pile of dollars to

just find out if that transistor is usable or

dead. Much information on the condition of

a transistor can be had using nothing more

than a VTVM and a resistor. One simple

amplification test shows whether the transis-

tor can amplify, and also reveals shorted and

open transistor junctions. Another collector -

to -base leakage test spots leaky and drifting

transistors. These tests are used when the

transistor tester is not on hand or when a

quick test bench check of transistor condi-

tion is needed.

Those Tests. Amplification and leakage

tests use an ohms range -giving resistance

readings well up on the scale to insure that

the test voltage is not too low. To avoid

calculations, resistance readings are used as

guidelines to transistor condition although

leakage currents can be calculated from an

Ohm's law formula.

Current flow in the ohms test lead of the

typical VTVM (for any indicated resistance

on any range) may be calculated using the

formula

1= Vb /(Rx Rc)

where Vb is the ohmmeter -circuit battery

voltage, Rx is the measured or indicated re-

sistance, and Rc is the center -scale resistance

reading of the selected ohms range.

Voltage across the ohms test leads, which

is also across the transistor under test, varies

from Vb (usually 1.5 volts with the test leads

66

open) down to zero with the test leads

shorted. This voltage varies uniformly with

meter- pointer position, not indicated resis-

tance. It is exactly Vb /2 (half of Vb), or .75

volt, when the meter pointer is at mid -scale.

Amplification. For the amplification test,

connect the circuit as shown, but less S1 (or

the clip lead) . Set the ohms -range selector

on the VTVM to R x 10 ohms. This range

passes up to 15 milliamperes current with

test leads shorted. The indicated resistance

s1 VTVM

AC

COMM OHMS

Just two components -a 2.2k resistor (shown here as

2000 ohms) and a s.p.s.t. switch (shown here as a

clip lead) -suffice for transistor amplification tests.

should be above 5000 ohms -near full -scale.

A very much lower reading indicates a leaky

or shorted transistor. Connect the clip lead

or switch SI to connect Rl to the base of

Ql. This supplies base curent to the transis-

tor. The indicated resistance should then

drop to a value much lower than 2000 ohms

(the value of R1). Usual values are 30

ohms or so for high -gain transistors to 200

ohms or so for low -gain transistors. If little

(Continued on page 113)

ELEMENTARY ELECTRONICS

electronics

IMAGINEERING

Look what happens when imagin -ation

and engin -eering get together!

,.,,.1.,1,,,,111,11,1 ,1,,...1,1,1,.,,1111,1, ,11111,...I,.n../..,1,,,,1,1,1111 1,11,... 111,111111...,11,.11MIM

Read Battery Drain Quickly

To measure battery drain in radios and

experimental circuits, use this special test

lead. Cement a thin brass or aluminum

strip to each side of a piece of plastic.

PLASTIC 32 THICK

METAL

STRIP

LEAD'S

SOLDER

(>.`h

METAL

STRIP

BATTERY

TERMINAL

Then solder leads to each metal strip and

connect them to a VOM. Insert the lead

between the batteries and terminals to

make quick current -draw readings.

Rubber -Mount Treble Speaker

Rubber suction cups are ideal shock -

mounts for treble loudspeakers. They

make good mechanical mounts and acous-

tically isolate the speaker frame from

cabinet panels which tend to accentuate

the bass frequencies. Attach the cups to

the speaker frame with screws (get the

kind of cups having threaded inserts or

screws) and to the cabinet panel with

rubber or service cement.

Salvaging Worn

When a vol-

ume, tone, or

other radio -TV

variable resist-

ance control be-

comes worn and

gives spotty op-

eration that can't

be eliminated

with control

Radio -TV Control

RESISTANCE

/ ELEMENT

(-4- GOOD

PORTION

SLIDE CONTACT

WORN

WIRES E

cleaner, try reversing the two ouiwer wiic

connections. This may put the operating

range of the control on the least -used por-

tion that is still serviceable.

VOLUME

CONTROL

MARCH-APRIL, 1967

Color- Coding Wires

When you need

some color -coded TAPE

wires for a circuit

COUNTDOWN

FOR

Why should any sophisticated DXer

wait for network radio reports of

what's what with our astronauts when

he can tune in on the action direct?

By Tom Kneael

K2AES /KBG4303

Being something of a busybody, al-

ways concerned with what's going on

behind the scenes, I decided that while net-

work TV /radio coverage of our space shots

was okay for the general public, it was fall-

ing far short of the mark where I was con-

cerned. What about all of those long pauses?

What did Jules Bergman mean when he said,

"They appear to be having some kind of

problem in the capsule ?"

Having a trusty Hertz inhaler sitting on

the shelf, I decided to try and locate the

original source of the network's information

-the network's remote transmitter located

aboard the rescue vessels. A little tuning

and there it was, loud and clear and furnish-

ing considerably more "closed circuit" in-

formation on the progress of the space shot

than was filtering through to John Q. Public's

transistor portable. Not only was I able to

dig out the network's stations, I accidentally

stumbled upon the entire NASA communi-

cations network, rescue ships, Cape Ken-

nedy, helicopters, and all. I was able to

listen to the music being sent from Cape

Kennedy to the capsule and even to Presi-

dent Johnson wishing the astronauts a happy

landing, all direct and as it was happening

(the network coverage frequently ran these

communications, but with mucho delay).

The Big List. One problem I had arose

when I found that most of the NASA sta-

tions weren't using callsigns or announcing

their locations, using instead "tactical" iden-

tifier names. After listening in on a few of

the launchings and taking notes, comparing

my own observations with those listed in DX

club bulletins (such as ASWLC, CIDXC,

and NNRC), I was able to piece together a

handy roster of the stations and their most

often heard 'fone (mostly SSB) frequencies.

Every time I spoke to a fellow DX hound

about my little list I was buttonholed for a

copy and hounded until I came through with

an exact duplicate of the fruits of my moni-

(Continued on page 70)

ELEMENTARY ELECTRONICS

Elementary Electronics' Guide to Space Shot DX

POSSIBLE APOLLO LAUNCH STATIONS

17655 kHz 20186

SEARCH & RECOVERY NETWORKS

3023.5 kHz.

3090

4690

4739

5718 (Circuit 1B)

6393

6694.5 (Circuit 1D)

6698

6709.5

6993

8880

8975.5

8982.5

8985

9005 (Circuit 11I)

9027

9830

11205

11248 (Circuit 1K)

11256.5

11421

13227

13237

13320 (Circuit 1M)

15022

15028.5

15051

15088 (Pacific)

15968

17610

20007 (emergency)

RADAR TRACKING STATIONS

Ships: Ship Sierra, Ship Whiskey, Ship

Yankee, RKV, Alumni, Auto 1, Number 1,

etc.

6787 kHz 8176 11514 18635

7898 10648 14896 18660

7919 10780 17643 19960

22857

Antigua Tracking, Antigua Is.

7919 kHz AFE86 10780 AFE86

Ascension Tracking, Ascension Is.

6752 kHz AFE83 11634 AFE83

7919 AFE83 12140 AFE83

10780 AFE83 20286 AFE83

11407 AFE83 20454 AFE83

20700 AFE83

Canary Tracking, Canary Is.

8119.5 kHz EAU65 13527.5

13423 20450 EDT63

13447.5 EDT42

Canton I. Tracking, Phoenix Is.

10987.5 kHz KCCA 16440 KCC97

Cape Kennedy, Fla.

5775 kHz AFE70 14585 AFE70

7675 AFE70 14896 AFE70

7833 AFE70 17390 AFE70

7919 AFE70 18330 AFE70

8260 AFE70 19960 AFE70

10780 AFE70 20390 AFE70

11634 AFE70 20454 AFE70

12140 AFE70 20475 AFE70

13170 AFE70 20700 AFE70

13878 AFE70

Honolulu Tracking, Hawaii

9212 kHz 12212

10410 KUH50 13175.5

Kano Tracking, Nigeria

9440 kHz 50V8 18335

13905 50V23 21845

London Tracking, England

6970 kHz GAD26 13620 GDJ33

7480 GC127 13595 GBB33

8005 GLK28 14890 GCI34

9157.5 GAN29 18130.5 GCB38

10792.5 18580 GMJ38

10795 GBL30

13555 GIC33

Panama Tracking, Panama

9132.5 kHz HPI 17682.5 HOD72

10242.5 HPD2 20727.5 HOD24

15925 HPE

Perth Tracking, Australia

9200 kHz 13580

10950 V K K4 14939

Sydney, Australia (link to Honolulu)

10165 kHz 13500 19465

Tananarive Tracking, Malagasay Rep.

7690 kHz 11430

9863 5RX98 12275 5RY23

10270 20990 5RZ9

BROADCAST OPERATIONS

Aboard rescue vessels

6956 kHz 9460 KH9344 & KJ3197

9337.5 13915 KJ3498

IT &T Control, Brentwood, N.Y.

7622 kHz WFH87 14635 WFK44

11035 WFL51

RCA Control, Rocky Point, N.Y.

4555 kHz WEO44

7407.5 WEP57

9095 WEP69

9460 WE059

10620 W ES50

13915

15460

15982.5

15987.5

18960

WES43

WES65

WES25

WES75

WES58

MUSIC TO CAPSULE

15016 kHz

CAPSULE FREQUENCIES

225.7 mHz

259.7

296.8

telemetering

voice

GODDARD SPACE CENTER

7580 kHz

7878

10615

SOME STATIONS IN SEARCH & RESCUE

NETWORKS

Ageless Sierra Kwajalein Relay

Atlantic Chief Radio (Marshall Is.)

Atlantic Public Affairs Lake Champlain (ship)

Atlantic Recovery Lant Leader

Atlantic Surgeon Lively Net Radio

Atlantic Tribe Mayport Control

50V7 Atlas (Jacksonville, Fla.)

Boxer (NASA ship) McKinley Leader

50V4 (Continued on pnon 701

15870 50V3

MARCH -APRIL, 1967 69

COUNTDOWN

A FOR DX

Continued from page 68

toring. Apparently there are very few lis-

teners who realize how easy it is to eaves-

drop on these communications. I thought

that you might like to have a copy, so I'm

making it immortal in these hallowed pages.

As clarification to the listings, I'd like to

point out that most of the frequencies are

approximate, and some of the locations

stated as the users of tactical callsigns are

educated guesses. Some fellows have, I un-

derstand, gone on to bigger and better things

by even obtaining QSL's from stations en-

gaged in these launches -notably the sta-

tions at Cape Kennedy and aboard the

U.S.S. Guadalcanal.

It seems that most of the communications

from Cape Kennedy are actually transmitted

from the Cape via remote control from the

Manned Space Flight Center at Houston.

With each space shot the picture changes

slightly. For instance, the President has

been heard talking to the capsule on 6709.5

kHz during one shot and on 9005 kHz in a

subsequent launch. Sometimes the press

stations are shifted around from one vessel

to another (KJ3498 has been aboard the

U.S.S. Wasp and the U.S.S. Guam during

different shots). In any event, the frequen-

cies seem to remain fairly constant over the

various shots and the same tactical callsigns

are heard regularly. The busiest channels

are 6709.5, 9005, and 15088 kHz.

How Good Is the Data? All of the in-

formation in this article is based on listening

reports made during the Mercury and Gem-

ini shoots. However, you can bet your bot-

tom buck that 95% of the network will re-

main intact and on frequency for the Apollo

space shots. With the space communications

networks around the globe tried and proven,

Apollo communications needs will be serv-

iced by the existing network with new fre-

quencies added only where old channels get

too crowded.

I think that by listening to these stations

you'll greatly add to your appreciation of

the gigantic task it is to successfully launch,

keep track of, and land a manned capsule.

It's quite an involved deal, and you can be

part of the "in" group digging the sounds

while your neighbors sit and wonder what's

happening.

70

DX'ing a Russian in space is difficult because of

the language barrier and the Reds' reluctance to

announce space shots in advance. The author even has

trouble identifying Volga River boat captains.

Space Shot DX List

Continued from page 69

Camera Bug (aircraft)

Cape Recovery

Chisel Bolt (ship)

Dauntless

Eastlant Leader (ship)

Eniwetok Rescue

(Marshall Is.)

Fisher

Gemini Quad

Goodrich (ship)

Guadalcanal Sick Bay

(ship)

Guam Rescue

(Mariannas Is.)

Gulf Stream

Gun Train

Hickory

Houston Public Affairs

Houston Recovery

Houston Surgeon

Ivanhoe (Norfolk, Va.)

Naha Rescue

(Ruykyu Is.)

Norris (ship)

Northlant 3 (ship)

Pacific Chief

Pary

Pine Tree

Pistol Pete

Rescue 1 (helicopter)

Roamer

Rony

Samoa Rescue

Sea Roar

Singapore Relay

Southlant (ship)

Star Buster

Strike 1

Top Hand

(Annapolis, Md.)

War Chief

Wasp Radio (ship)

Westlant Leader (ship)

Who will be the first U. S. astronaut you DX?

The coming Apollo program promises many firsts.

ELEMENTARY ELECTRONICS

Now when your pet experiment is deprived of

AC power it will complain loudly about it.

How many times has your electricity gone

off at night and you never knew it-

until you woke up late for work? There are

also many more -serious situations that need

instant attention, such as in laboratories

where a complicated experiment might be

a complete failure because you never knew

that the line voltage had failed sometime

during the experiment.

At home there is the refrigerator and

freezer to worry about as well as the electric

alarm clock. Of course a power line failure

due to a thunderstorm will usually awaken

some member of the family. However many

power line failures originate many miles

from your home. A careless motorist may

knock over a utility pole, a line fuse may

blow, or some other remote type of failure

may occur without warning.

In the past it has been necessary to use

a relay energized by the line voltage, when

the line voltage failed the relay dropped out

and a battery and buzzer connected in series

produced a warning sound. Here is a solid -

state circuit that has no moving parts and

should be very trouble free. The heart of

the circuit is a Sonalert. The Sonalert deliv-

ers an audible signal generated by a tran-

sistor oscillator driving a ceramic transducer.

It operates on 6- to 28 -volts DC and only

draws 3 ma. to produce 68 db of sound. At

28 volts DC it will produce up to 80 db of

sound.

How it Works. You should find the cir-

cuit quite interesting. The schematic diagram

shows the line voltage is rectified by a full -

wave bridge Zl. It is filtered and used to

maintain a trickle charge on a 9 -volt battery,

through diode D1. Current limiting resistors

R1 and R2 are used to adjust the DC voltage

across R3, which is the load resistor. It also

serves as the return path from the Sonalert

to the negative terminal of the battery. The

capacitor removes some of the ripple from

the DC voltage. When line voltage is present

the 10 volts developed by the current flow

(from Z1) through the 1000 -ohm resistor

(R3) is shunted across the Sonalert by diode

D1. This is because the diode has a much

lower forward resistance than the Sonalert.

When the line voltage fails the battery can-

not discharge back through the diode so the

current flows through the Sonalert and back

through the 1000 -ohm resistor to battery

minus. When this happens the Sonalert

ennnrc off with a 2800 -cycle tone alerting

MARCH- APRIL, 1967 71

AgLINE FAILURE ALARM

anyone in the listening area. The Sonalert

will continue to sound until the line voltage is

restored or until switch S2 is turned off.

The push -to -test switch is there to test the

alarm circuit. Since the battery is on a per-

manent trickle charge and the Sonalert draws

only a little over 3 ma. the battery should

last well over three years.

To build the Line- Voltage Failure Alarm

you will need the parts listed. Most of the

parts are standard and all should be available

at your parts distributor. Substitutions may

be made for manufacturers listed but be

Front panel shows dimensions of layout and size of

holes to drill to duplicate the Line Failure Alarm.

This noisemaker can be included in another project.

very sure to use the values listed. The two

switches, Sonalert and battery are attached

to the back of the front panel. The balance

of the parts are mounted on a phenolic

board using turret terminals. If you prefer

you may use perforated phenolic board and

push -in terminals or flea clips. The board is

then mounted on the panel by a standoff

which raises it above the slide switch. Switch

S2 is necessary because whenever the line

cord is unplugged the Sonalert will sound off.

Construction. The first step in building

Schematic diagram of Line Failure

Alarm shows few parts are required to

wire the device. Diode D1 shunts

current from bridge rectifier Z1 past

Sonalert. Reversed current, from

battery, powers Sonalert.

72

R1

this device is to lay out the holes in the front

panel and drill and file them out. After all

the holes are drilled in the black phenolic

panel carefully wipe it clean and spray it with

several light coats of model maker's dull

spray. This spray is available in hobby shops

and most drug stores. Apply decals or press -

on letters to designate the intended use of

the switches. Spray on a final coat of dull

spray as a protection for the lettering.

While the front panel is drying you can

work on the phenolic circuit board. The large

photograph of the board will help you in

the layout and placement of the parts. The

phenolic box must have a hole drilled in

the left end for the line cord. All the wiring

is straightforward and the only necessary

precaution is to use a heat sink when solder-

ing the leads of the diode and rectifier.

After the wiring and assembly is finished

double check the hookup before plugging in

the line cord. After plugging the cord into

an outlet slide switch S2 to on. The Sonalert

may sound off depending whether or not the

DC voltage across Cl, R3 is higher or lower

than the battery voltage. If it does sound off,

ignore it and proceed as follows: connect

a DC voltmeter across the filter capacitor

PARTS LIST j

B1 -9 -volt mercury battery (Mallory TR146X or

equiv. -see text)

C1- 50 -mf., 25 -volt electrolytic capacitor

D1- Diode, 1N34 (or equiv.)

R1 -8,200 -ohm, 1 -watt resistor

R2 -2,000 -ohm potentiometer (Mallory MTC-

2314 or equiv.)

R3 -1,000 -ohm, 1/2-watt resistor

Sl- S.p.s.t. pushbutton switch

S2- S.p.s.t. slide switch

Z1 -Full -wave bridge rectifier (Mallory FW50

or equiv.)

Z2- Sonalert (Mallory 5C628 or equiv.)

Misc. -Phenolic box, box cover, solder termi-

nals, wire, solder, battery holder, battery

connector, line cord, machine screws, nuts,

spacers, panel decals, etc.

Estimated cost: 89.25

Construction time: 2 hours

R2 2000A Sl

SONALERT

Z2

AC -1

R3

1000 - 81 -

*9v T

S2

ELEMENTARY ELECTRONICS

BI S1 Z2 S2

All of the electronic components are mounted on the

cover of the box. The circuit board (top right) is

mounted on the/standoff seen protruding from near the

bottom left -hand corner of the circuit board. One

machine screw, through hole above S2, secures board.

(Cl) and adjust R2 until the Sonalert is

silent -the meter should now read about 10

volts. Now press the pushbutton (Si) and

the Sonalert should sound once more. While

holding the button in, slide switch S2 to its

oft position -this should quiet the Sonalert.

Make it Louder. To make the Sonalert

louder it is necessary to increase the voltage

applied to it. Since it is the battery that

powers it when the line voltage fails it is

necessary to use a higher -voltage battery.

You can use a RM411 which is rated at

14 volts. Mount it in the same battery holder

as before, but it will be necessary to solder

the battery leads directly to the battery termi-

nals. The proper battery holder is a Key-

stone number 166. Of course this also means

that a higher DC voltage is necessary from

the rectifier. You will have to substitute a

5500 -ohm, 2 -watt resistor for the 8200 -ohm,

1 -watt resistor. A convenient way to do this

is to use two 11,000 -ohm, 1 -watt resistors in

parallel. Now potentiometer R2 is adjusted

for 15 volts or if you don't have a voltmeter

adjust R2 with the slide switch on until the

Sonalert is off. Pulling the line plug should

start the sound again. This modification will

make the sound a good deal louder.

If you want the alarm to wake you up

plug it into an outlet near your bed and set

the alarm on your bedside table. There will

be no trouble recognizing the distinctive

2800 -Hz tone -you will never confuse it

with an alarm clock, telephone, or door bell.

For use as a laboratory alarm plug the

alarm into the same outlet with your equip-

Completed Line Failure Alarm shows adjustment po-

tentiometer R2 in center of component side of circuit

board. Adjustment must be made with the unit opened.

ment for your experiment. If by chance you

want the alarm quite a distance away from

your laboratory area then a long extension

cord may be used. Don't forget to slide the

switch to oft when moving the alarm from

place to place.

.........-.. r..-......-......-.......-..-..-«...-..-..-...,..-........-.,..-.....-...-...-....-.<

: HOME STUDY BLUEBOOK COUPON

(Turn page for details)

Age Are you a Veteran? Employed in Electronics?

Occupation Male Female Single Married

Are you a student? Full -time Part -time Home Study

Check the last school you attended: Circle schools you graduated:

Grade School High School College Graduate School

Have you ever taken a Home -Study course? Completed?

What school(s)?

What is your yearly income to the nearest thousand? $

(If your income is $6745, write in $7000)

.--..H... 1-111.-.

MARCH- AFRIL, 1967 73

HOME STUDY

BLUEBOOK

e /e's Guide to selected

Home -Study Courses

now being offered by

Electronics Schools

CL:, One of the E's in Electronics is for Educa-

tion- wherever you can get it. Fortunately,

many of our readers are located near resident

schools offering electronics courses suited to

their educational needs. A far greater number,

however, are less privileged on one or both of

two counts: resident schools are either located

so far away that attendance would be impracti-

cal or personal educational needs have become

so esoteric and specialized that resident schools

simply can't provide appropriate instruction.

And this is where home -study courses from non-

resident schools can prove indispensable. For

such schools not only fill normal educational

needs, they actually forge ahead by offering

courses and personalized educational services

resident schools can never hope to provide.

CA Listed below are a few courses from several

home study schools. For more information,

circle those course numbers that interest you on

the coupon below, and fill out both sides of the

coupon. ELEMENTARY ELECTRONICS will for-

ward your request to the schools and ask that

additional data be sent to you directly.

1. 2 -Way Radio. National Radio Institute's Complete Communications Course gets

you to pass the FCC First Class Radiotelephone license exam or returns your money.

This "beginner- oriented" course covers mobile, marine, aircraft, and railroad com-

munications, plus radio -TV transmission, microwave relay, and teletype. Course con-

tains 70 lessons with texts, 13 reference texts, 7 training kits. Tuition: $309 with time

payment optional; average completion time, two years. GI Bill approved.

2. 2 -Way Radio. Grantham School of Electronics' FCC License Course (Course

FL). No previous training required; enrollment at any time; up to one full year

allowed for completion. Prepares student for First Class FCC Radiotelephone license;

if he fails, all tuition payments are refunded. Course of 88 lessons in basic mathe-

matics, basic electricity, basic electronics, and communications electronics. $130 cash

in advance; or $25 down, 6 monthly $20 payments. GI Bill approved.

3. Radio Construction and Repair. Progressive Edu -Kits train you to become a Radio

Technician (no education or experience necessary). For $26.95, you receive all parts

and instructions for building 20 different radio and electronic circuits, guaranteed to

operate. Kits contain 12 receivers, 3 transmitters, signal tracer, amplifier, signal injector,

code oscillator, square -wave generator. You also receive printed circuit materials, a

multiple tool set, electric soldering iron, books and other valuable items.

4. Computer in a Case. Cleveland Institute of Electronics offers four Auto -

Programmed Glide rule lessons along with their already- famous electronics slide rule,

which features nine conventional scales plus an "H" scale to solve resonant frequency

problems and the "2 pi" scale for inductive or capacitive reactance problems. Lessons

and slide rule (complete with case) are only $24.95.

1 ELEMENTARY ELECTRONICS, Dept. HS -1

1 505 Park Avenue, New York, N. Y. 10022

1

1 1 2 3 4

CUT HERE

CS. Yes! I would like to know more about the electronics

interested in only the course numbers circled below.

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ELEMENTARY ELECTRONICS

The prospective radio operator licensee must be proficient in the state-of-the-art,

whether it be tubes or semiconductors. Prepare yourself -learn the basic circuits.

Those of us who passed the FCC radio op-

erator's test years ago would be unpleas-

antly surprised if we had to take it today.

Since 1950, the tests have been expanded

to cover UHF radio, radar, FM radio, tele-

vision, and the use of semiconductors in com-

munications. Each of these new fields has

added questions to the operator's tests. The

most recent addition to the tests, semicon-

ductors, has added many new questions.

Questions on semiconductors will be easier

for the novice than for the old -timer. Once

tube operation is mastered, it is hard to re-

learn amplifier theory on a current basis

rather than on a voltage basis. In 1950 there

were no transistors, and no tunnel diodes.

At the rate that semiconductors are being

incorporated into electronic equipment, by

1970 there may be no tubes.

One thing we can be sure of is that the

radio operator licensee must be proficient in

the state -of- the -art, whether it be tubes or

semiconductors, and the Federal Communi-

cations Commission operator's test questions

will reflect this requirement. So this month

I will cover some of the test questions about

semiconductors, ,many of which are in-

cluded in the new supplement to the Study

Guide to Radio Operator's Examinations,

just published by the U.S. Government

Printing Office.

Q Describe the physical structure of two

types of transistors and explain how they

operate as an amplifier.

A Generally, there two basic types of tran-

sistors. These are the seldom- encountered

point- contact and popular junction types.

The point -contact transistor is constructed of

a single pellet of n -type germanium with two

catwhisker -like contacts. These catwhiskers

are the emitter and collector, while the base

lead makes an area contact with the body

of the pellet. This pellet is very small, being

in most cases no larger than the head of a

pin. p -type areas are formed around the

catwhisker connections.

The junction transistor is constructed as a

multiple wafer sandwich. A pnp transistor

consists of an n -type germanium wafer with

a p -type wafer on either side. Connections

are made to the wafers with wires, the cen-

ter wafer being the base. ,

Amplifier action is as follows: barriers are

formed at the wafer junctions. These bar-

rier resistances are affected by the applied

external currents. Forward biasing the base -

emitter junction increases the supply of holes

in the base -collector region, which is reverse -

biased. This allows a comparatively small

current (supplied to the base -emitter junc-

tion) to control a larger current through the

base -collector junction, thus giving a power

gain. A voltage gain is available and is

maximum in the common- emitter circuit

configuration due to the high ratio of input

to output impedances.

Q Draw a schematic diagram of a two stage

audio amplifier using transistors.

MARCH-APRIL, 1967 75

1(g FCC Q&A

Ti

R2

BIAS

INPUT

BIAS

OPTIONAL

Fig. 1. This typical transformer -coupled two -stage

transistor amplifier can be used for preamplifier or

output (to speaker or as modulator) stages -the basic

circuit is the same. Only the actual part values will

change as power or signal levels reach maximum.

A See Fig. 1.

Q What affect does biasing have on the

performance of a PNP transistor?

A A transistor circuit will generally not op-

erate at all without some forward bias on

the base emitter circuit. Too much forward

bias on the base circuit will damage the tran-

sistor. Proper biasing is therefore necessary

for the transistor to operate.

Q Name some common types of transistors

and draw their schematic symbols.

A There are two general classes of transis-

tors, by physical construction: point- contact

and junction; by wafer arrangement: pnp

and npn. The schematic symbols for tran-

sistors are shown in Fig. 2.

T2

I2

OUTPUT

NPN

INPUT EMITTER LOAD

RESISTOR

Fig. 2. Either NPN or PNP transistors may be used

in a circuit -just reverse supply voltage polarity.

Emitter- follower or common collector circuit is the

semiconductor equivalent of the vacuum -tube cathode -

follower circuit -both have a gain of less than one.

Q Draw a transistor amplifier circuit which

would be analogous to that of a vacuum -tube

cathode- follower amplifier.

A See Fig. 2.

Q Draw a simple schematic of a Hartley

type transistor oscillator.

A See Fig. 3.

76

FEEDBACK

COUPLING

Fig. 3. Oscillator circuits will be a major part of

the examination. This basic Hartley oscillator cir-

cuit will be important to remember. Basic Colpitts

oscillator circuit is given in Fig. 6. Make sure

you can tell the difference between the two types.

Q Describe the difference between positive

(p -type) and negative (n -type) semiconduc-

tors with respect to: (a) the direction of cur-

rent flow when an external emf is applied:

(b) the internal resistance when a external

emf is applied.

A (a) When an external emf is applied to a

p -n or n -p junction, the current flow tends

to be high when the polarity is negative to-

ward the n -type side, and positive toward

the p -type. A pnp transistor in a common

emitter circuit is therefore forward biased

(that is, has largest current flow) when the

emf polarity is negative in the base circuit,

with reference to the emitter; and when the

second emf is positive in the collector cir-

cuit, with reference to the emitter. The in-

ternal resistance is smallest in this forward

bias direction. Therefore, for maximum in-

ternal resistance, the polarity described is

reversed. An npn transistor is exactly op-

posite to the pnp type.

Q What is the difference between forward

and reverse biasing of transistors?

A Forward bias is that condition of maxi-

mum current flow and reverse bias is the

condition of minimum current flow. A pn

junction is considered forward biased, the

condition of maximum current flow, when

an emf is applied positive to the p -type side

and negative to the n -type. A common -

emitter pnp transistor has an n -type base, a

p -type emitter, and a p -type collector. For

proper operation, the base- emitter cir-

cuit is forward biased; the collector- emitter

circuit is reverse biased. The emf supplies

therefore connect: negative to base, positive

to emitter; negative to collector, positive to

emitter. An npn transistor would have op-

posite polarities to maintain the same bias-

ing.

Q Show connections of external batteries,

resistance load and signal source as would

ELEMENTARY ELECTRONICS

appear in a properly (fixed) biased common -

emitter transistor amplifier.

A See Fig. 4.

Q Draw a circuit diagram of a method of

obtaining self -bias, with one battery, without

current feedback, in a common -emitter am-

PNP

SIGNAL o, J

INPUT I

A

SIGNAL

INPUT

ci

BIAS

VOLTAGE

g DIVIDER

SIGNAL

INPUT

BIAS

PNP

BI

Ti

B

ii

OUTPUT

R3 EMITTER -BIAS

RESISTOR

Fig. 4. Simple resistor bias (R1 in A) is unstable.

Adding R2 (in 8) maintains constant voltage at base.

Connecting R1 to collector (in C) introduces nega-

tive feedback and reduces temperature runaway. Volt-

age drop across primary of T1 (from increased current

flow in collector) lowers forward bias to base input.

plifier. Explain the voltage drops in the re-

sistors.

A See Fig. 4.

There are three basic common- emitter bias-

ing circuits, each of which is shown in Fig.

4. Fig. 4A is comparable to a fixed -bias

vacuum -tube circuit. Here the base is for-

ward biased by battery B1, through re-

sistor R l which acts to limit the current in

the base circuit, since in a forward bias con-

dition the base -emitter circuit has a low

resistance. The collector -emitter circuit is

biased by B2, through the load Tl. There

is no degeneration in this circuit.

The bias for both base and collector are

supplied by a single battery in Fig. 4B. The

base -emitter bias is supplied by a voltage di-

vider consisting of R1 and R2. This circuit

has one basic flaw. The base -emitter circuit

has, as mentioned before, a low resistance

when forward biased. The value of R2 is

MARCH -APRIL, 1967

chosen to be between 5 and 10 times the

base -emitter resistance to partially stabilize

this resistance. It cannot be too low, and

since R1 is generally considerably higher,

the current through the base -emitter circuit

is not stable with variations in temperature.

A method of biasing the transistor that is

better, from the standpoint of stability, is

shown in Fig. 4C. The bias is supplied here

by R1 from the collector circuit. This sup-

plies degeneration and also acts to stabilize

the bias by its self- correcting action. Emitter -

bias resistor R3 is unbypassed, further sig-

nal degeneration is introduced here that also

helps to stabilize the circuit. Too, this re-

sistance acts to raise the base -emitter re-

sistance.

Q Explain the significance of each item

listed: (A) Collector -to -Base Voltage (Emit-

ter open) -40 MAX. VOLTS (B) Collector -

to- Emitter Voltage (Base to Emitter Volts -

0.5v)-40 MAX. VOLTS (C) Emitter -to-

Base Voltage -5 VOLTS MAX. (D) Collec-

tor Current 10 MAX. MA. (E) Transistor

Dissipation at Ambient Temperature of 25 °C

for operation in free air 120 MAX. MW.

(F) At case Temperature of 25 °C for opera-

tion with heat sink 140 MAX. MW. (G)

Ambient -Temperature Range: Operating and

Storage -65 to 100 °C.

A The rating given in transistor handbooks

fall into two categories: absolute Maximum

ratings and working ratings. The ratings

shown here are absolute maximum ratings.

With the emitter open, if the collector -to-

base voltage exceeds 40 volts, the transistor

will be damaged.

The second specification is the reverse

breakdown voltage on the collector- emitter

circuit with the base reverse- biased. This is

also specified frequently in terms of a micro-

ampere leakage current called 1,,.

The third specification is the reverse

breakdown voltage across the base -emitter

circuit. From this we can judge that the in-

put to the stage should not exceed -5 volts

when summed with the forward bias. Since

the forward bias is usually small, from a

voltage standpoint (a constant- current

source), the input must be restricted to a

10 -volt swing at peak value on a sinusoidal

signal.

The collector current is listed as 10-MA.

maximum. Under no conditions should the

base bias be such as to allow a greater cur-

rent flow in the collector circuit.

Transistors are self -destroying when their

maximum ratings are exceeded, because a

77

IJ

@ g FCC Q & A

destruct cycle is started which reinforces

itself. For example, if an excessive current

flows in the collector circuit, the transistor

junction overheats. This heat causes the re-

sistance of the junction to decrease, which

causes the current to increase further, which

in turn, heats the junction more, etc.

Maximum dissipation is stated to be 120

MW. This is the real limiting factor in tran-

sistor operation. Although the collector -

emitter voltage is stated to be 40 volts, and

the collector current stated to be 10 MA,

the transistor cannot handle both maximum

values at the same time. This would be a

dissipation of 400 MW. Either the volt-

age or current can be the stated maximum

value, and the other must be limited to the

value that will not cause the maximum dissi-

pation to be exceeded. For instance, if the

voltage is -40 volts, the maximum current

can only be 0.120/40 or 3 milliamperes. No-

tice too that this dissipation is specified at

room temperature in free air -this means

that in normal operation if the room tem-

perature of the air at the transistor exceeds

25 °C, the maximum dissipation must derate

accordingly. If a heat source such as a pow-

er resistor were located near the transistor

and no ventilation provided, the transistor

might be derated from 120 milliwatts to

possibly as little as 1 milliwatt.

The seventh specification limits both the

storage, that is, inactive; and operating tem-

perature to -65 °C to 100 °C. The transistor

will cease to function even in a derated con-

dition beyond these temperature extremes.

Q Draw a circuit diagram of a common -

emitter amplifier with emitter bias. Explain

its operation.

DRIVER

PNP

A See Fig. 4C. The resistor in the emitter

circuit, R3, is used to develop emitter bias

voltage. However, contrary to vacuum -tube

operation, transistors must be biased on, not

off. The resistor used here bucks the forward

bias of the base circuit. Without a bypass

capacitor, its effect is to raise the input re-

sistance of the transistor by a rule -of -thumb

factor of approximately R X beta (gain of

the amplifier.) A 1000 -ohm resistor would

raise the input resistance (if the amplifier

gain was, say, 100) to 100 X 1000 or 100,-

000 ohms. The actual input resistance can-

not be raised this much, but lower resistance

values give a good approximation. A further

effect is to stabilize the stage gain. The de-

generation introduced in this manner is very

effective in stabilizing stage gain and pre-

venting thermal run -away.

Q The value of the alpha cutoff frequency

of a transistor is primarily dependent upon

what one factor? Does the value of alpha

cutoff frequency normally have any relation-

ship to the collector -to -base voltage?

A The alpha cutoff frequency of a transistor

is primarily dependent on the width of the

base region of its junction and the following

formula is fairly accurate: alpha cutoff (in

megacycles) is equal to C /Wa, where C is

equal to 5 -6 for germanium npn, 1 -9 for

germanium pnp. W is equal to the width

of the base region in mils. The alpha cutoff

frequency increases with increasing collector

bias because widening of the space- charge

layer decreases the effective base region

width.

Q Why is stabilization of a transistor am-

plifier usually necessary? How would a ther-

mistor be used in this respect?

A Stabilization of a transistor amplifier is

necessary because of variations in the tran-

sistor characteristics with varying tempera-

tures. A thermistor can be used in the bias-

(Continued on page 111)

b

` OPTIONAL, USE

,ONLY IF COLLECTOR

EXCEEDS BASE I

+REQUIREMENT

Fig. 5. Typical transistor amplifier transformer -couples low- signal stages to drive push -pull output stages.

ELEMENTARY ELECTRONICS

Paradys, S. Afr"...a

Sarawak, Mayl ly i 1

Lusaka, Zombi,

Suva, Fiji

Tananarive, Malagasy

Gwelo, Rhodesia

Pyongyang, Khrc n

Wewak, Palau*

Taipei, Taiwan

Conakry, Guinea

Kabul, Afraganistan

Bagdad, Iraq

Kabul, Afghanistan

Paradys, S. Africa

R r k, Maylaysia

L ! ¡I G . Zambia

Suva, Fiji

Tananarive, Malagasy

Gwelo, Rhodesia

Pyongyang, Korea

1 { t 1 Papua

I diwan

Conakry, Guinea

Kabul, Afraganistan

lagdad, Iraq

'ibul, Afghanistan

By Walter R. Levins

Tired of the ordinary SW DX? Looking

for a new frontier to conquer? Well,

here's something new and difficult for even

the old -time Shortwave Listener (SWL) to

add to his list of rare DX loggings.

For the average SWL, 90 meters is an

unknown part of the SWBC ( ShortWave

BroadCast) spectrum -a part he never tunes

in. However, here on 90 meters lurks that

rare DX on a relatively low frequency. Low

frequencies coupled with low power present

a challenge you can't afford to miss. But in

return, that rare QSL comes and makes the

undertaking well worthwhile. With winter

here, the 90 -meter SWBC band should be

at its maximum.

The band extends from approximately

3250 kHz (kc) to about 3995 kHz (which

actually is 75.09 meters). On these fre-

quencies some of the rarest DX can be

found. Most 90 -meter stations broadcast pri-

marily for listeners in regional areas and

very few for international purposes. Hence,

there are mostly low -power stations on 90

meters. Now let's have a look at these sta-

tions by continent.

Africa. This continent is hard to log

for some SWLs. Not many stations have

high power. But on this band, Africans

constitute a large part of the DX. Countries

like Rhodesia and South Africa, with their

policies of apartheid, bear some attention.

Both of these countries can be logged on the

SW outlet on this band. A high -powered

station (100 kw) operated by Radio Clube

de Mozambique offers the only high -pow-

ered transmissions from Africa on this band.

Mozambique is one of the last colonies in

Africa, thus making it a controversial coun-

try to verify.

Frequency Power Station & Country

(kHz) (kw)

3250 20 Paradys, S. Africa

3255 10 Liberian Bc. Corp., Liberia

3259 20 R. Malaysia, Sarawak

3260 100 R. Clube de Mozambique

3270 10 Lusaka, Zambia

3284 10 Suva, Fiji Isl.

3288 30 Tananarive, Malagasy Rep.

3290 25 R. Nacional, Colombia

3295 100 Delhi & Bombay, India

3306 10 Gwelo, Rhodesia

3320 50 Pyongyang, Korea

3335 10 R. Wewak Papua

3335 10 Taipei, Taiwan

3375 10 R. Angola

3376 50 Conakry, Guinea

3780 100 R. Iran

3925 50 Tokyo, Japan

3985 50 R. Kabul, Afghanistan

3990 50 Baghdad, Iraq

Asia. This is a continent which many

SWLs lack in terms of logged countries -

especially those SWLs on the East Coast.

The Far East has many offerings; such as

Sarawak, Indonesia, Fiji Islands and Taiwan.

Most Asian transmitters are of the low -

power variety, save India (100 kw), Japan

(50 kw), Pakistan (50 kw) and Afghani-

stan (50 kw). Middle East stations in Iran

90 -meter band. Sierra Leone has its only

MARCH -APRIL, 1967

(Continued on page 113)

79

ce

o

a

ó

v

c 0 E E o

V

880

ARECIBO LISTENING

Mercury, that speedy little planet nearest

the sun, probably rotates on its axis once

every 88 days, it says here (here being a

nationally known and respected encyclopedia

bearing a 1964 copyright). But the real

period of Mercury's rotation is a mere 59

days. Says who? Says the most authoritative

voice now exploring the heavens, a unique

radio -radar telescope that fills an entire val-

ley near the little Puerto Rican port of

Arecibo.

Operated by Cornell University and spon-

sored by the U.S. Advanced Research Proj-

ects Agency, the Arecibo telescope easily

qualifies as the world's biggest ear. The en-

tire installation covers an area larger than

56 city blocks, and the antenna alone-

supported by a complex network of towers,

cables, and guys. (see photo above )-weighs

an unbelievable 450 tons!

Happily, the Big Ear has already come

forth with scientific findings worth its weight

and more. The planet Venus, for example,

shrouded in a cloak of clouds and therefore

immune to most probing, has always been

assumed to rotate counterclockwise like any

normal planet. But Arecibo has found that

Venus revolves clockwise (though the why

of the matter remains a problem for another

day). Still, Arecibo may someday offer the an-

swer to this and countless other riddles. For

the Big Ear has only begun to listen.

-Ron Mitchell

ELEMENTARY ELECTRONICS

the inside story

on DETECTORS

RFC4

C36 `L

R26

138

B+

R25

-1-C35

R23

C34

C37

R24

r

1T6 ' ÓÓ 00'

I

1/10 L-

PHASE

DISCRIMINATOR

R36

C541

R22

l C27

R20

C26

R21

J

R34

Much has happened since the days of the simple

crystal detector. Now we have FM and SSB to add to

that old standby -the AM diode demodulator.

By Leo G. Sands, W7PH /KBG 7906

The next important function of a short-

wave or home receiver after receiving and

amplifying the RF signal is to extract the

intelligence. This is the job of the detector.

However, some prefer to call it a demodu-

lator when it picks out the amplitude -modu-

lated carrier. For FM signals this important

detector stage usually is one of several types

-the most common ones are the discrimina-

tor and the ratio detector. Whatever name

you give to a detector stage, the circuit really

doesn't care. It does its job by snipping out

the intelligence from the RF in the form we

would like to hear it -code, voice and even

music.

An AM detector may be either a diode

rectifier or a non -linear amplifier. When a

steady AC voltage (such as an unmodulated

RF signal) is applied to a rectifier, either

sheared off as illustrated in Fig. 1. When

applied to a non -linear amplifier, either the

positive or negative half cycles are amplified

more than the other as illustrated in Fig. 2.

The output waveform, therefore, is not a

replica of the input waveform.

An AM radio signal is simply AC (RF

carrier) modulated by lower frequency AC,

be it voice, music or an audio tone. Modula-

tion causes the amplitude of the carrier to

vary. If we examine a radio carrier with an

oscilloscope, it will look as shown in Fig. 3,

except the sine waves may be narrower and

closer together- depending on the time -base

(horizontal) rate. When modulation is ap-

plied to the carrier it will compress and ex-

pand the RF carrier as shown in Fig. 4. This

is known as an AM radio -signal envelope -

the peaks of the RF sine waves representing

the positive or negative half of the signal is

MARCH- APRIL, 1967

the modulating signal. Since the positive and

81

DETECTORS

ti. j. ¡ ' s

, , , 1

1 1 1 1 1 1

,

1

Fig. 1. Perfect diode strips away part of carrer

Output voltage is determined by diode connections

so it can be either positive or negative. Connections

do not matter in simple circuits as in Figs. 5 and 6.

Fig. 2. Non -linear amplifier results in s'gnal stripp ng

waveform shown. Average voltage below line must

be subtracted from average voltage above zero line.

The resulting signal distortion is indicated in Fig. 9.

0 -

Fig. 3. When viewed on an oscilloscope the RF s'gnal

would appear as above -depending on the sweep fre-

quency. High repetition rate at left; low at right.

0 -

RF CARRIER

as shown in Fig. 7. The negative -going por-

tion of RF component (carrier) remaining

in the detector output is filtered (bypassed)

by capacitor C which has an extremely -low

impedance at the carrier frequency (RF)

and a comparatively -high impedance at the

audio (AF) modulating frequencies. There-

fore, the voltage applied to the headphones

is an audio signal.

Recognize the circuits in Fig. 5 and 6?

They're what used to be known as crystal

sets -which employed a galena or other

metallic crystal as a rectifier (diode). To-

day the adjustable crystal diode has been

replaced by a miniature device -a germani-

um or silicon (semiconductor) diode.

Non -Linear Amplifier. When an AM

signal is applied to a non -linear amplifier

(using the basic circuit shown in Fig. 8) the

positive half of the signal has a much greater

effect on plate current than the negative

half. The tube is biased almost to cut -off.

When a positive -going signal is applied to its

grid, plate current rises sharply. A negative -

going signal causes a reduction in plate cur -

(Continued on page 85)

Fig. 5. Series -diode detector allows one half of

modulated -carrier signal to flow through headphones

while presenting high impedance to other half.

AF

ENVELOPE

Fig. 4. Gap occurs in RF carrier only when modulation

exceeds 100 %. Such operation distorts audio informa-

tion and generates harmonics and other interference.

RF FILTER

Cl SHUNT

DIODE

negative peaks are almost mirror images of

each other, and equal in amplitude but of

opposing polarity, one of them must be elim-

inated or attenuated in order to extract the

modulating intelligence.

Diode Detector. As we said before, an

AM radio signal can be demodulated by

feeding it into a rectifier or a non -linear am-

plifier. If fed into a diode detector using the

series -rectifier circuit shown in Fig. 5 or the

shunt -rectifier circuit, Fig. 6, the positive

half of the AM envelope will be sheared off

(as in Figs. 1 and 2), leaving the negative

half upon which the modulating signal rides,

Fig. 6. Shunt -diode detector shorts one half of the

carrier signal across headphones; other half flows in

headphone circuit with C separating RF from audio.

o

RF AF

ENVELOPE

Fig. 7. With positive half of carrier (top half)

stripped away RF follows low -impedance path through

C in Figs. 5 and 6. Audio flows through headphones.

82 ELEMENTARY ELECTRONICS

4111E0 1967 CATALOG'

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TUBE

CHARACTERISTIC

CURVE

BIAS

POINT

CUTOFF

LINEAR

PORTION

C

c RF I

SIGNAL SIGNAL I

GRID VOLTAGE

PLATE CURRENT SATURATION

PLATE

CURRENT

RF

HEAD-

PHONES

BIAS PLATE )

- 0+ VOLTAGE VOLTAGE

Fig. 8. Plate current /grid -bias voltage characteristic

curve is for the typical operation of most tubes.

rent -which is already low and which can't

be reduced to less than zero regardless of the

amplitude of the negative -going signal.

Therefore, the output signal, shown in

Fig. 9, is not a replica of the input

signal (Fig. 4) and is inverted (positive sig-

nal at grid increases plate current and de-

creases plate voltage). Again, a capacitor

(C) across the output filters out the remain-

ing RF component. The average plate cur-

rent through the headphones, therefore,

follows the modulating signal.

Practical Diode Detectors. In most tube -

type AM radios, the detector circuit uses

one diode section of a duo -diode- triode tube,

as shown in Fig. 10. The detector follows the

last IF amplifier. The amplitude modulated

IF signal (RF after conversion to a lower

frequency) is fed to the plate of the diode.

But, it is not a shunt detector (as in Fig. 6)

even if its cathode is grounded. The detec-

tor is in series with the secondary winding

of the IF transformer, R1 and R2. Capaci-

tors Cl and C2 in conjunction with R1 form

a low -pass filter which passes the AF signal

NO- SIGNAL

PLATE VOLTAGE

PLATE -CURRENT CUTOFF

POSITIVE GOING

SIGNAL

IFMTRAN

C 1

AVC R3

C4

AF

C3

C2

Fig. 10. Duplex- diode -triode detector and the first

audio stages appears in almost all AM receivers.

Circuit has changed little in 30 -odd years of use.

but removes the remaining RF in the signal.

The AF signal voltage is developed across

R2 and is fed through C3 to the grid of the

AF amplifier (triode section of the tube). At

the same time, a DC voltage is also devel-

oped across R1 and R2, resulting from

rectification of the IF signal. (Arrows indi-

cate electron path) . The level of the DC

voltage varies at the AF rate. However, by

adding R3 and C4, a steady DC voltage is

developed across C4 which becomes charged

and prevents the voltage from varying with

the audio. The level of the DC voltage

across C4, therefore, is proportional to the

level of the IF carrier signal, not of the

derived AF signal. This voltage (AVC) is

used for controlling the gain of the receiver

by applying it to the grids of RF, IF and

mixer stages.

Instead of a tube, a semiconductor diode

(D1 in Fig. 11) may be used in the detector

circuit. In many transistor -radio circuits,

the diode polarity is reversed, as shown in

the circuit in Fig. 12. Here, the diode (D1)

provides AGC voltage to transistor IF ampli-

RESULTING

OUTPUT SIGNAL

PLATE - CURRENT

SATURATION

AF ENVELOPE

ACTUAL SIGNAL

NEGATIVE GOING

SIGNAL

Fig. 9. Because tube does not cutoff sharply at the Fig. 11. Circuit of semiconductor -diode defector is

bias point some distortion is introduced in signal just about identical with that of vacuum -tube circuit.

that rides between the bias point and current cutoff. r o ^I ^ +e. t.^ . ;d ^. 6te h ;ny frnm detector DC.

MARCH -APRIL, 1967 85

DETECTORS

fier stages. A small negative voltage is ap-

plied to the cathode of the diode and, at the

same time, to the base circuits of the gain -

controlled transistors. This negative voltage

forward biases the transistors and the diode.

Current flows through the diode even when

no signal is being received.

When a signal is received, current flow

through the diode is increased by positive

signal swings and reduced or cut off by nega-

tive signal swings. A positive DC voltage is

also developed across CI which opposes the

negative forward bias applied to the tran-

sistor bases, causing the receiver gain to

drop. Hence, the receiver gain is controlled

by signal level.

) T

VOLUME

CONTROL

Fig. 12. Cell B applied forward bias to diode D1 to

overcome junction potential- increasing sensitivity

of detector and AGC controlled RF and IF transistors.

AVC

Fig. 13. Full -wave detector circuit increases average

voltage available for AVC (AGC), AF output. It is

seldom used because it requires special (tapped) coil.

Dual -Diode Detectors. A pair of diodes

can be used to form a full -wave detector

circuit, as shown in Fig. 13. Or, two diodes

can be used in a voltage -doubler circuit as

shown in Fig. 14 to provide 6 db of gain in

the detector stage. When the IF signal swings

negatively, diode D1 conducts and charges

Cl. When the signal swings positive, D2

conducts and charges C2. The resulting DC

voltage across R 1 is equal to the sum of the

voltage charges across C I and C2, each of

which charges to the peak value of the IF

signal. The AF signal is also developed

86

Fig. 14. Full -wave voltage doubler circuit

nol level to audio amplifier input but not

eliminate an audio stage; actual cost is

RF

raises sig-

enough to

increased.

Fig. 15. Plate -detector circuit is similar to that

in Fig. 8. Bias voltage is developed across R1 and

is filtered by Cl. Bleeder R2 increases cathode bias.

across R1, if Cl and C2 are not so large as to

bypass audio frequencies.

Plate Detectors. The circuit in Fig. 8

is of a theoretical or basic plate detector. A

practical circuit is given in Fig. 15. Bias is

provided by cathode resistor R1, augmented

by current through R2 which makes the

cathode more positive with respect to the

grid (grid more negative). Since the grid is

always negative, and never draws current,

the input impedance is extremely high.

Grid -Leak Detector. The input imped-

ance of a grid -leak detector is not as high

as that of the plate detector since some grid

current flows, loading down the resonant in-

put circuit and lowering its Q. The signal

is fed to the grid through a capacitor (C1),

as shown in Fig. 16. The grid and cathode

function as a diode (with the grid as the

anode), forming a shunt rectifier circuit (as

in Fig. 6). When the RF signal is positive

going, grid current flows since the grid -

cathode path looks like a partial short cir-

cuit, causing plate current to rise and Cl to

charge -with polarity as indicated in the

diagram.

When the input signal is negative going

grid current flow cannot occur and the

signal voltage is added in series -aiding with

the charge on Cl, reducing plate current.

Excessive build up of voltage in Cl, result-

ing in possible blocking of the tube, is pre-

vented by grid leak R1 which is the load for

the grid -to- cathode shunt rectifier. Bias volt-

ELEMENTARY ELECTRONICS

9

RF 1

Fig. 16. Grid- cathode circuit of triode acts as a

diode -R1 is load. Voltage across Cl varies along

with audio modulation impressed on received carrier.

LI

RF

j

Fig. 17. Load for grid -cathode diode is R. Voltage

across R1 biases triode to cutoff. Filter Cl passes

RF while recovered audio (AF) passes on through C3.

age developed by the intercepted signal is

determined by the values of Cl and R1, as

well as the signal level and frequency.

So, how does it detect? When no signal

is being received, plate current is maximum

since there is no bias. When a signal is re-

ceived a negative grid -bias voltage develops

across R1 (grid to cathode) and plate cur-

rent is reduced. Modulation on the carrier

causes plate current to drop more than rise.

Hence, the output signal is not a replica of

the input signal, and average plate current

represents the modulating signal.

Actually, a grid -leak detector is a com-

bination of a diode detector and an AF am-

plifier as Fig. 16 suggests. The grid sees and

amplifies the output of the shunt -diode de-

tector found inside the tube by the cathode -

to -grid electron glow.

Infinite- Impedance Detector. The cir-

cuit in Fig. 17 could be that of a cathode

follower amplifier. It can be a detector or a

power amplifier, depending upon the ohmic

value of a cathode resistor R (which deter-

mines the bias voltage and the valves of

components in the grid circuit). When R

has a relatively high value, the grid is biased

so that the tube operates in the non -linear

portion of its characteristic curve (see Fig.

8) . Then it is a detector which functions

like a plate detector. Positive input signals

cause a sharp rise in cathode current and

negative signals cause a small reduction.

This is known as an infinite impedance

MARCH- APRIL, 1967

detector, used mainly in the hi -fi AM tuners

-it provides no voltage gain.

Pentode Detectors. Pentodes are also

used as grid -leak and plate detectors. Their

output impedance is much higher than for

triodes and resistance- capacitance coupling

to the AF amplifier is generally employed.

The biggest advantage of using a sharp

cut -off pentode as a detector is gain. The

grid -leak detector circuit shown in Fig. 18

delivers a much higher signal voltage to the

AF amplifier than one using a triode. The

same is true of the pentode plate detector

circuit shown in Fig. 19. The screen voltage

can be critical. When using either circuit

it is necessary to try various screen voltages

to obtain maximum output with minimum

distortion.

Regenerative Detectors. About 55 years

ago, Dr. Lee DeForest and his associates

.RF SCREEN

BYPASS

Fig. 18. Pentode circuit is essentially the same as

that for a triode. Screen gives added gain to stage

as well as other advantages of using a pentode tube.

RF i BIAS

RESIST

Fig. 19. Plate detector using pentode should be com-

pared to that of triode in Fig. 15. Voltage developed

across bias resistor operates tube near cutoff region.

were developing an AF amplifier, in Palo

Alto, California, utilizing DeForest's audion

(triode) tube. Accidentally, the output

transformer and the input transformer got

too close together and oscillation took place.

About the same time, Major Edwin H.

Armstrong deliberately designed an elec-

tronic oscillator around the DeForest tube.

The courts were busy for a long time trying

to determine which came first, the chicken

or the egg. (Turn page)

87

eDETECTORS

The barristers argued about the regenera-

tion technique for drastically increasing the

gain of a detector and for producing RF

energy. If we take the grid -leak detector

circuit of Fig. 16 and add a tickler coil (L3

in Fig. 20), we have a regenerative detector.

Before filtering the RF out of the plate cir-

cuit (with C2), if we feed the plate current

through coil L3, energy will be fed back

from the plate to the grid. We use the tube

to amplify the intercepted signal. Then,

after amplification, we send it back through

the tube to be amplified again. As a result

the gain of several tubes is obtained from the

use of only one.

However, most regenerative detectors

are unstable and can cause interference to

someone else's reception. That's why they

have almost disappeared in spite of their

high gain.

To receive CW (code signals), the de-

tector should oscillate. When receiving AM

signals, the detector should not oscillate.

Maximum gain (sensitivity) and selectivity

are obtained just below the threshold of os-

cillation. Therefore, receivers with regener-

ative detectors are equipped with a regenera-

tion control -there are many types. In Fig.

20, variable capacitor C3 is the regeneration

control. The lower its capacitance, the

greater the feedback. A potentiometer (R2)

L3

RF /

LI

RF

88

is used in Fig. 21 to control regeneration by

varying the plate voltage. And, in Fig. 22

in which a pentode vacuum tube is used,

regeneration by varying the screen voltage

with R1.

Superregenerative Detectors. The same

man, Armstrong, who invented FM and the

superheterodyne, also invented the super -

regenerative detector. It's like a regenerative

detector except that it is alternately swung

in and out of oscillation at an ultrasonic

rate. It provides extremely high gain, but

it lacks the selectivity of a plain regenerative

detector.

The regenerative detector (V1) shown in

Fig. 23 is made superregenerative by the

quench oscillator (V2). When the quench

oscillator's signal swings positive, it reduces

the bias on V1, allowing it to oscillate. When

it swings negative, it quenches the oscillation.

The quench oscillator frequency can be

quite low as long as it's above the frequency

of audibility.

Most superregenerative detectors are self -

quenched-a separate quench oscillator is

not used. Instead, the detector's grid leak

and capacitor have values which cause the

tube to function as a blocking oscillator and

a regenerative detector simultaneously. The

grid leak (R) resistance is increased to a

high value (several megohms) and is some-

times connected between the grid and plate

(B +) as shown in Fig. 24.

A superregenerative detector will detect

both AM and FM signals. It often provides

as much sensitivity with one tube or transis-

AUDIO

TRANSFORMER

RI

REGENERATION

CONTROL

Fig. 20. Regenerative detector

uses separate feedback winding

AF (L3). Feedback is controlled

by varying capacitance of C3-

changing circuit impedance for RF

through L3, C3 and triode. Grid

leak R1 -C1 develop grid bias as in

a grid -leak detector circuit.

AUDIO

TRANSFORMER

AF

REGENERATION

Fig. 21. Autotransformer L2

provides feedback signal to grid

circuit. Feedback is controlled

by varying overall gain of circuit -

increasing or decreasing plate

voltage with R2 (a voltage

CONTROL divider across B).

ELEMENTARY ELECTRONICS

I

RF

REGENERATION

CONTROL

Fig. 22. Screen -voltage regeneration control has

smoother control over regeneration. Rapid changes

in supply voltages seriously affect regeneration.

Batteries or well- regulated power supply are a must.

REGENERATION CONTROL

no

DETECTOR RFC

V1

RF

RF SIGNAL -

quency deviates -+kHz, detector output

will be maximum. When it deviates'.-5kHz,

detector output will be much lower. As the

carrier frequency deviates, the detector out-

put will vary and the FM signal will be de-

modulated. This is known as slope detection.

The results leave much to be desired, as far

as fidelity is concerned.

A superior slope detector employs a more

elaborate circuit, as Fig. 25 indicates. Here,

L2 is tuned to a frequency above the mean

IF and L3 below the mean IF. When the

incoming signal is deviated upward, a larger

voltage is developed across L2 than L3, and

Fig. 23. With the exception of added

quench oscillator and grid resistor connec-

tion, circuit of superregenerative detector

is identical to the circuit given in Fig. 20.

QUENCH

SIGNAL

V2 e

RF

FILTER

QUENCH

OSCILLATOR

tor as a superhet employing several. It also

provides limiting action. Its response to

weak and strong signals is about the same.

But, it has poor selectivity and has a back-

ground hash (noise) when no signal is being

received. This detector will also cause inter-

ference unless preceded by an RF amplifier.

FM Slope Detectors. The job of an FM

detector is to sense a change in the frequency

of a radio signal. It should not sense changes

in signal amplitude. This can be avoided by

employing limiters ahead of the detector. A

limiter saturates when it is fed a signal above

a certain level and delivers a signal of con-

stant amplitude to the detector. Thus, if fed

an AM signal, the AM (variation in ampli-

tude) is erased. But, changes in frequency

are not affected.

The simplest way to demodulate an FM

signal is to use an AM detector tuned slightly

off frequency. In a superherterodyne re-

ceiver with a 455kHz IF, for example, if

the receiver is detuned so that the IF pro-

duced by an unmodulated carrier is at

450kHz instead of 455kHz, the output of

the detector will vary as the frequency of the

signal is deviated. When the signal fre-

AF

AUDIO.

TRAN

Fig. 24. Self- quenching circuit is

preferred for high -frequency receivers. The

regeneration control bypasses RF through

variable capacitance shunting from L3.

RF FILTER

L3 GRID

L1

L

RF

LEAK

REGENERATION

CONTROL

AUDIO

TRANS.

Fig. 25. Slope detector is difficult to align and

requires sharply -tuned circuits. Critical circuitry

is never popular since it requires frequent retuning.

vice versa. While each of the detectors (Dl

and D2) detect changes in amplitude, they

will jointly demodulate an FM signal since

the signal amplitude seen by each depends

upon frequency.

Discriminator. The Foster -Seeley circuit

is a much more sophisticated FM detector.

As Fig. 26 shows, the signal from the pre-

ceding IF stage (limiter) is fed inductively

into the secondary of T and through a ca-

pacitor (C) to the center tap of the second-

MARCH -APRIL, 1967 89

I@ DETECTORS

ary. When T is tuned to the carrier fre-

quency and the incoming signal is at that

frequency, equal and opposite voltages are

fed to the two diodes. The DC voltage at X

is zero. When the frequency of the signal

deviates up and down, each diode alternately

conducts more heavily than the other. There-

fore, the voltage at X becomes alternately

positive and negative, obtaining AF from an

FM signal.

Fig. 26. Foster -Seeley discriminator was very popular

in the early days of TV. Now it is seldom used -

only a very few hi -fi FM tuners use this circuit at all.

IF

90

RFC

--1 (r, '000O' -

C4

Ratio Detector. While this circuit is used

widely in FM communications receivers, the

ratio detector (shown in Fig. 27) is com-

monly used in FM broadcast tuners and re-

ceivers and TV sets. It combines some of

the features of a limiter and a discriminator.

Capacitor C charges to a level determined by

the level of the incoming signal. The effects

of rapid changes in signal level are negated.

Gated -Beam Tube. One of the most ef-

fective FM detectors employs what is known

as a gated -beam tube (6BN6, etc.) which is

used in a circuit such as the one shown in

Fig. 28. The symbol for a gated -beam tube

is the same as for a common pentode, but

the tube is actually quite different.

The suppressor grid (No. 3) voltage of a

pentode has but little effect on plate current.

But, the voltage on the quadrature grid (also

No. 3) of a gated -beam tube has a great

effect. If even slightly negative, plate cur-

rent is cut off and the control grid (No. 1)

loses control. If slightly positive, plate cur-

rent is controlled solely by the signal on the

control grid.

In the gated -beam detector circuit shown

in Fig. 28 the quadrature circuit (L and C)

is tuned to the center frequency of the IF

IN

AF

D2

GATED -

8EAM

T

TRA

SHARP-CUTOFF

PENTODE Iii'

IF

TRAN

AF

R4

AF

Fig. 27. Ratio detector has built -in

limiting that eliminates need for the

special stages that contribute little

or no gain. This circuit is a favorite

for cutting those production costs.

Fig. 28. Gated -beam detector uses o

quadrature coil (tuned circuit L -C) fo

form a reference signal that converts

FM signal into audio (AF) voltages.

Phase difference between IF signal

and quadrature signal is the secret.

Fig. 29. Using a sharp -cutoff pentode

requires added bias for the suppressor

grid. This suppressor bias is developed

across RI -CI and increases the

effectiveness of the control the sup-

pressor grid has on plate -current flow.

ELEMENTARY ELECTRONICS

Fig. 30. Bradley

detector was never

popular in entertain-

ment receivers. Again,

o hard -fo -align circuit

-increases production

cost and loses

popularity or, in many

cases, never gets a BIAS

chance in mass- NETWORK

produced circuitry.

IE TI IF

TRANS

Fig. 32. Product detector is

also used for SSB (Single Side

Band) audio recovery.

Complex circuit gives better

stability and isolation

for the BFO circuit.

OSCILLATOR

II, T2

DETECTOR

AF AMP

AM SSB

R5

vvvv

R6

-'VVV-110

C6 AF

Fig. 31. Single Sideband

defector requires BFO (Beat

Frequency Oscillator) to

reinsert carrier signal. The

rest of the detector

circuit is the same as that

for the diode detector

in Fig. 10.

(the carrier frequency as translated to the

IF within the receiver). When a signal at

the IF center frequency is fed through T

to the control grid (No. 1) -L -C is shock

excited at its resonant frequency and gen-

erates a signal voltage at that frequency.

When the incoming signal is deviated in fre-

quency (FM) the phase relationship be-

tween grids 1 and 3 varies, causing them

to be alternately positive and negative, but

not in phase. The plate current, therefore,

varies with the change in frequency of the

incoming signal.

The circuit shown in Fig. 29 is similar,

but a sharp -cutoff pentode is used instead

of a gated -beam tube. It functions in a simi-

lar manner except that bias for grid 3 is

developed across R1 and Cl by the signal.

Both types of FM detectors are popularly

used ln I v sets, out me gaLeu-vc ssIs LYYC

preferred in FM communications receivers.

Still another type of FM detector is the

Bradley detector, whose circuit is shown in

MARCH- APRIL, 1967

Fig. 30, which was developed at Philco.

Here, an oscillator is employed, operating

at the translated carrier frequency (IF). As

the signal deviates in frequency, the local

oscillator signal and the incoming signal are

out of phase and extract a signal (audio)

which is equal to the rate at which the signal

frequency is being deviated.

SSB Detectors. An SSB (Single Side -

Band) signal is a form of AM signals Or-

dinarily, an AM signal has two sidebands

one above and one below the carrier. The

same intelligence is contained in each. Only

one is required for reception. And, in fact,

91

DETECTORS

even the carrier is superfluous as far as the

actual transmitting is concerned. Therefore,

most SSB transmitters radiate only one side -

band and no carrier. For example, an SSB

transmitter operating on 27,125 -kHz and

modulated by voice within the 300 -3000 -Hz

(cps) range would radiate a signal extending

from 27,125.3 -kHz to 27,128 -kHz, but no

carrier on 27,125 -kHz.

In order to demodulate an SSB signal it is

necessary to re- insert the carrier at the re-

ceiver. The re- inserted carrier can be at the

IF. For example, if the above signal is

intercepted with a receiver having a 453 -kHz

ceivers. One of these is the typical product

detector circuit shown in Fig. 32. Tubes V1

and V2 form an electronic mixer. The in-

coming SSB signal is fed to the grid of V1

and the BFO signal is fed to the grid of V2.

The output of the mixer, containing both

signals is fed to the cathode of V3, a

grounded grid detector. Its output feeds

audio to the AF amplifier.

The product detector shown in Fig. 33

employs one less tube. Tube VI is a cathode

follower whose output is fed to the cathode

of V2 which functions as a detector. The

BFO signal is fed to the grid of V2 where

the signals are mixed. An RF filter (C1, C2,

L) removes any remaining BFO and side -

band signals, leaving only the recovered

audio.

Transistor Detectors. So far, we have

Fig. 33. Circuit is similar lo

that of product defector in Fig. 32

-modified circuit requires

one less triode. A great saving in

space as well as parts.

Fig. 34. Transistor circuit

has base tapped down on the coil

of the tuned circuit. Using tap

reduces loading on tuned circuit -

increasing selectivity.

IF (27,125 -kHz translated to 455 -kHz), a

locally generated 455-kHz signal is required.

An ordinary AM detector of any type can

be used along with a 455 -kHz BFO (Beat

Frequency Oscillator) as shown in Fig. 31.

The 27,125.3- 27,128 -kHz signal will have

been translated in the receiver to 455.3 -458

kHz. When this sideband is heterodyned

with a 455 -kHz CW signal, the resulting

beat frequencies will extend from 300 -3000

Hz (455.3. -455 = 0.3 kHz and 458 -455 = 3

kHz). If the frequency of the BFO varies,

the pitch of the recovered voice signals will

be changed. This will also happen as the

transmitter or receiver local oscillator fre-

quency varies. Therefore, the BFO is usually

made variable in order to offset these fre-

quency changes.

Product Detectors. More sophisticated

SSB detectors are used in professional and

amateur communications receivers and trans-

IF

only looked at tube and semiconductor diode

detectors. Transistors can be used in similar

circuits except in the case of a gated beam

FM detector which has no solid state

counterpart.

The most common transistor detector for

AM employs a circuit similar to the one

shown in Fig. 34. Here, fixed forward bias

is not provided. Instead, the signal provides

forward bias. When no signal is present,

collector current is zero except for minute

leakage current. Negative signal excursions

92

(Continued on page 116)

ELEMENTARY ELECTRONICS

Electronic

Foot Stomper

By

Herb Friedman

W2ZLF /KBI9457

Why not beat time

the Space -Age way -

use electronics to

save your achin' feet.

Because they cost next -to- nothing (use

junk -box components), and can be as-

sembled by a five -year -old, electronic metro-

nomes have always been a favorite one -night

project with experimenters. They always

work, and are great for elementary school

Science Fairs, primarily because while other

science fair projects just sit and stare at the

parents, a metronome at least will tic- tic -tic.

But an electronic tic -tic can be more than

a child's toy. Dress it up in a fancy box,

select component values that get the tics to

vary continuously through the 40 to 208

beat -per- minute range, and you've got a nice,

and thoughtful, gift for a musical friend.

And your cost (less the box, speaker and

battery) comes to less than $3.50.

QE of R2

Whole circuit is contained on a scrap of perforated

phenolic circuit board. Only other component on the

board is C1- that's on the other side. If you like Cl

can be mounted on this side of board alongside Q1

and Q2. Control R1 is mounted on side of cabinet.

MARCH -APRIL, 1967

Electronic Is Better. What's the ad-

vantage in an electronic metronome? Well

there's tone quality and long -term con-

venience, to name just two. The ordinary

arm- buster used by musical students requires

winding, and it's five -to -one the spring will

run out long before the last note of the

Hungarian Rhapsody. And the usual tack -

tack of the spring -wound arm buster is often

more annoying than the clown who inter-

rupts every fifth note to comment on the

musician's abilities. On the other hand, the

metronome shown in the schematic diagram

produces a soft thock -thock sound, similar

in characteristics to a muted tom -tom drum,

a very pleasant beat to play along with.

The basic metronome circuit shown could

cost you under $3.50- providing you use

only the components listed in the Parts List

and shop carefully. Do not attempt to im-

prove performance by using industrial grade

components as a tantalum capacitor is not

going to improve anything over the lowest -

priced Cl specified. Same thing with tran-

sistors Q1 and Q2. With the specified tran-

sistors the output sound is a soft thock-

thock; using better or less expensive tran-

sistors will result in the usually annoying

electronic metronome tic -tic sound -like

someone driving a nail into your ear. How-

ever, if you like tic -tic substitute the least

expensive audio -grade transistors you can

get (like 20 for a dollar) ; and while you can

93

®Ag FOOT STOMPER

substitute for the specified R1, R2 and CI

values, keep in mind that the timing will not

correspond to a standard metronome.

Circuit Board. Assemble the electronics

on a section of perforated phenolic -board

about 1 inch x 1 inch. If you don't have a

scrap of perf -board lying about use any piece

of stiff fibre board or plastic and drill your

own holes with a #52 or 1,4e -inch drill.

(Don't be fussy about the hole size, as long

as the component doesn't fall through, the

hole is the right size.)

Solder terminals are not needed. As

Inside view of Foot Stomper shows speaker, battery,

location of 121 and perforated circuit board. The

battery is mounted on the bottom cover of the speaker

cabinet -use flathead screws to prevent scratches.

shown in the photographs, just pass the leads

through the holes, twist once, and solder.

The completed metronome consists of the

phenolic board assembly, the external R1,

the battery and the speaker. The speaker

can be anything you've got lying around

with a 3.2 -, 4- or 8 -ohm voice coil. Any six -

volt battery will do -the smaller the better.

So little current is drawn the battery should

last almost as long as its shelf -life.

Box It. For a little ritzy styling, you can

use the inexpensive wood grain speaker en-

closure shown. The cabinet is purchased

complete with speaker, volume control and

wire. Remove the existing speaker -level con-

trol and install R1 in its mounting hole.

Using a single screw, with a 1/4 inch spacer

or stack of washers between the board and

the cabinet, install the metronome circuit

R1

Direct -coupled transistor circuit has few components

and requires only a scrap of phenolic board to mount

them on. Speaker SPI is the largest item and S1 -R1

mounts on the side of the speaker enclosure. Either

6 -volt battery or 4 cells in series will power unit.

PARTS LIST

B1 -6 -volts (Burgess Z4 or equiv.)

C1- 2 -mf., 6 -volt electrolytic capacitor (La-

fayette 99C6003 or equiv.)

Q1- Transistor, npn (Motorola HEP -50 or equiv.)

Q2- Transistor, pnp (Motorola HEP -252 or

equiv.)

R1- 1,000,000 -ohm potentiometer with switch

Si (Lafayette 32C7287)

R2- 100,000 -ohm, 1/2-watt resistor

S1- S.p.s.t. switch (part of R1)

SPKR- Speaker (see text)

Misc.- Perforated phenolic board, battery holder,

mounting hardware, wire, solder, etc.

Estimated cost: $3.49

Construction time: 1 hour

COLLECTOR LEAD Q2 R2 Cl

GROUND LUG R3

Bottom view of perforated circuit board shows lone

component Cl and connections to speaker and BI.

board in the cabinet close to Rl.

Mount the battery holder (if one is used)

on the speaker cabinet's removable base.

Finish the wiring and your "Oh, how

thoughtful" gift is ready for presentation.

If desired, you can install a calibrated

dial under R1's knob to indicate the actual

beat. Slip a piece of stiff cardboard under

RI's mounting nut and then compare the

electronic beats against a standard metro-

nome- indicate the correct timing on the

cardboard.

c

r

94 ELEMENTARY ELECTRONICS

TENNA-Bil

You'll be outstanding in a parking lot

on the tip of your antenna or place the

by Steve

whether you mount the flashing light

box -mounted lamp on the dashboard.

Just as the blinker on top of an antenna

tower is a beacon for ships of the sky,

the Tenna -Blitz is your beacon as you go

through the American futility dance -trying

to find your car in the movie parking lot

when it's 12 midnight.

Or if you're the type of churl who sends

his date out for refreshments at the drive -in,

you can use the Tenna -Blitz to guide her

back before the iced drinks turn to warm

sugar- water.

What is the Tenna -Blitz? If you've got a

good imagination it's a miniature radio tower

with a blinker on top. Otherwise, it's a small

metal cabinet with a lamp on top that flashes

every three seconds (see, isn't it more fun to

have imagination ?). Of course, the Tenna-

Blitz isn't limited to finding your car. Need

some attraction for the window notices of the

local drama group ?; then throw the circuit

together on the perf- board, discard the cabi-

net to keep costs down, and we'll guarantee a

blinking light will attract almost as much at-

tention as last month's Playboy centerfold.

If you think hard you'll come up with even

more ridiculous uses for the Tenna -Blitz

than we've dreamed up.

What it is. The Tenna -Bliz circuit shown

in the schematic diagram is a simplified

blocking oscillator. When power is first ap-

plied, collector -to- emitter impedance of Q1

is high, keeping Q2 almost at cutoff. As Cl

charges, the end connected to the base of Q1

(through R1) goes more positive, till finally

it reaches a potential high enough to "break-

MARCH -APRIL, 1967

Karlsen

over" the diode formed by the base -emitter

circuit of Q1; Q1 conducts, causing Q2 to

conduct, and the current flowing through

Q2's emitter- collector causes lamp I1 to light.

At the instant of conduction, C1 discharges

R1

470a

Q1 R2

ci

2MF

I1

Qi

e RED

DOT .

Schematic diagram for the Tenna -Blitz reveals what is

known as a blocking oscillator. Resistor R1 (M con-

junction with capacitor Cl) controls length of flash.

PARTS LIST

B1-6 -volt Z4 battery (RCA VS068 or equiv.)

C1 -2 -mf, 6 -volt electrolytic capacitor (see

text)

11 -2 -volt, 60 -ma panel lamp (Type 48 or 49)

Q1 -2N647 npn transistor, or equiv.

Q2 -2N404 pnp transistor, or equiv.

R1-470 -ohm, (maximum) Ys -watt resistor

(see text)

R2- 2,700 -ohm, 1/2 -watt resistor (see text)

R3- 1,000,000 -ohm, 1/2 -watt resistor (see

text)

S1- S.p.s.t. toggle or slide switch

Misc.-Perforated phenolic board, chassis box,

grommet, battery holder, wire, solder, ma-

chine screws and nuts, scrap aluminum, etc.

Estimated cost: $2.00

Construction time: 1 hour

95

TENNA-BLITZ

through the base -to- emitter circuit of QI,

Q2's collector -to- emitter circuit, and R1.

When the charge on Cl falls below Q1's

base -to- emitter breakover voltage, Q1 is

driven to cut off, cutting off collector current

to Q2, and lamp I1 is extinguished. Then the

procedure starts all over with the charge on

Cl building up until Ql conducts.

The lamp flashes approximately every

01 illga Ma-

MOUNTING BRACKET

All components are mounted directly on a section of

pert -board without need for tie -points or terminals.

L- bracket attached to bottom holds board in place.

three seconds. The length of the flash -from

a rapid blink to a full second -depends on

RU's value. R3 (in combination with Q1's

leakage) provides a slight forward bias to in-

crease the blink time of lamp Il.

Average battery current is next -to- nothing

and a fresh Z4 battery can last for several

months. If you turn it on when you go into

the movie it will still be blinking six hours

later, and tomorrow, and tomorrow and to-

morrow.

Completed unit fits neatly into suggested chassis

box, although switch S1 should ideally be

of the miniature variety to avoid any pos-

sibility of crowding. Note holder for B1.

BI

Construction. Both the cabinet, (a 21/4 x

21/4 x 4 -inch aluminum chassis box) as well

as the battery holder are optional.

While we are certain that the Tenna -Blitz

will work with the transistors specified for

Q1 and Q2, any npn and pnp transistors

you've got in the junk box might work just

as well.

In the unit shown the electronic circuit is

assembled on a 11 x 2 -inch section of perf-

(Continued on page 114)

COLLECTOR LEAD 02 R2 C1

GROUND LUG R3

Only three components appear on bottom of perf-

board: capacitor C 1 and resistors R2 and R3. Collec-

tor lead from Q2 (see call -out) runs to one side of

lamp 11; screw holding ground lug in place also sup-

ports perf -board mounting bracket (see photo at left).

SI

96

01 02

II

All wired up and ready to go, completed unit

has but one control- switch SI, whose shaft

extends from lower left of front panel. Flasher

lamp 11 appears at top of chassis box; its

base is pressed into 1 /2 -in. rubber grommet.

ELEMENTARY ELECTRONICS

POWER

IN WATTS

LEO G. SANDS

Accurate power measurements

demand the right toots- -

instruments that can cover AC line,

audio, and RF frequencies

Do you know what's what with watts?

Power in watts, kilowatts and mega-

watts makes the industrial giant move -it

toasts your bread, dries your clothes, heats

your house, brightens that dark corner with

light and is right there when you want recrea-

tion. It's time you learned more about this

ever -faithful servant.

Electric power consumption is expressed

in watts. One watt is consumed by a one-

ohm load to which one volt is applied, caus-

ing one ampere of current to flow. Power in

watts is equal to

W= E1= E2 /R =12R

E representing volts, 1 representing current

in amperes, and R representing load resist-

ance in ohms.

The power consumed by a load in a DC

circuit can be determined by measuring the

voltage and current with a DC voltmeter and

and DC ammeter as shown in Fig. 1, and

then multiplying the meter readings to watts.

W = El

When the load resistance is known, power

consumption can be determined by measur-

ing either the voltage across the load or the

current through it as shown in Figs. 2 and 3,

and computing

W= E2 /R or W = 12 R,

respectively. If the load resistance is not

known, it can first be determined by measur-

ing it with an ohmmeter or bridge.

Resistance Load. When the load in an

AC circuit is resistive (lamp, heating ele-

ment, tube filament, etc.) , the same tech-

nique may be used -using AC meters, of

course -as shown in Fig. 4.

Volt- Amperes. In an AC circuit, when

the load is inductive (transformer, motor,

etc.) , the voltage and current are not in

phase. The products of the measured voltage

and current is equal to volt -amperes, not

watts, as before. To measure true power, a

wattmeter is required. Its indication will

differ from the calculated volt- amperes (ap-

parent power) by an amount determined by

the power factor of the load. The power

factor of an inductive load is less than unity.

An electrodynamometer is similar in con-

struction to a voltmeter or ammeter except

that it employs an electromagnet (field coils)

instead of a permanent magnet, as illustrated

in Fig. 5. The rotating coil, to which the

indicating pointer is attached, is the voltage

coil and is connected across the line through

a series resistor. The field coils are the cur-

MARCH-APRIL, 1967 97

IV® POWER IN WATTS

AMMETER

LOAD

Fig. 1. Voltmeter can be across source or load since

IR drop across ammeter is low; as is voltmeter current.

AMMETER

Figs. 2, 3. With constant- resistance load you need

only measure voltage (top). When voltage is known,

current measurement can be used to calculate wattage.

AC

LINE RESISTIVE

LOAD

Fig. 4. This connection for AC wattage measurement

is accurate only when the load is a pure resistance.

Multimeter -sized instrument that measures wattage,

current and voltage is made by Simpson -Model 390.

98

rent coils through which load current flows.

(In some types the rotor is the current coil

and the field coils are the voltage coils.)

The meter will indicate zero when there is

no load current through the current coils.

When there is load current, the meter indi-

cates the true power consumption of the

load, even if power factor is not 100 %.

SERIES RESISTANCE (MULTIPLIER)

CURRENT

FROM PIVOT COIL

LINE CURRENT

CO L

TO

SHUNT LOAD

Fig. 5. E ectrodynamometer -type wattmeter connects

to both s'des of line and to load- computes E X I.

Watt -hour Meter. The utility company

keeps track of the power you consume with

a watt -hour meter, which is essentially an

induction motor whose speed is çportional

to power consumption. It is installed where

the AC line enters the house. Like a watt-

meter, it has a voltage coil and two series -

connected current coils plus a compensating

coil, as shown in Fig. 6. The coils are wound

INE

VOLTAGE

CURRENT

COIL

COMPENSATING

COIL

ROTATING DISC

CURRENT COIL

LOA

DRIVE SHAFT TO

MECH. COUNTER.

MECHANICAL COUNTER

Fig. 6. Watt -hour meter is variable -speed motor and

a revolution counter -computes wattage against time.

on iron cores and are stationary. The moving

element is a metallic disc which rotates when

power is consumed.

Current flowing through the coils induces

current flow in the disc. Since the voltage

coil has many turns, it is highly inductive

and the magnetic flux at its ends will lag

about 90 degrees behind the applied voltage.

The fluxes at the ends of the current coils,

ELEMENTARY ELECTRONICS

which have very few turns, are in phase with

the current. Hence, torque is produced.

Sound. The threshold of human hearing

is zero decibel (db) equal to one tenth of

a billionth of a watt of sonic power per

square centimeter. The dynamic range of

the human ear is 120 db, a ratio of a trillion

to one.

Sound levels can be measured with a

microphone, audio amplifier and AF output

meter. However, a professional instrument

such as the General Radio 759 -13 sound -level

meter is more complex. Frequency weighting

networks are provided, as shown in Fig. 7,

r

MIC S

ATTENUATOR

AMP

WEIGHTING

NETWORK

ATTENUATOR

1* ril °

AMP WEIGHTING DC AMP CALIBRATED

NETWORK METER

Fig. 7. Block diagram of the General Radio 759 -13

sound -level meter shows the instrument is quite a

complicated device -required fo do precise tests.

to permit adjustment of frequency response.

The range of the instrument is from 24 to

140 db above the standard reference level.

Audio. Audio power level may be ex-

pressed in watts, dbm or dbw. The standard

reference levels are 0 dbm, representing one

milliwatt (0.001 watt), and 0 dbw, repre-

senting one watt. Hence, 10 watts could be

40 dbm or 10 dbw since a 10 db rise in

power level is ten fold in terms of watts.

An electrodynamometer wattmeter could

be used for measuring relatively high audio

power levels but only at the frequency for

which the meter was designed (usually

60 Hz- cycles per second) .

Ordinarily, audio power is measured with

an AC voltmeter, VTVM or calibrated scope

connected across the load, as shown in Fig.

8. If the load resistance is known, power

can be computed by dividing the resistance

into the square of the voltage

W = E2 /R.

For example, if there is 4 volts across a

16 -ohm load, the power consumed by the

load would be one watt since 4 X 4 divided

by 16 equals one.

MARCH -APRIL, 1967

AUDIO

AMPLIFIER RESISTOR

Fig. 8. Typical setup fo measure audio -power output

of public -address or high -fidelity power amplifiers.

When an oscilloscope is used for measur-

ing voltage across the load, it must be cali-

brated in terms of RMS voltage.

Another way is to use an audio (AC)

ammeter in series with the load as shown

in Fig. 9. If the meter indicates one ampere

AUDIO (AC)

AMMETER

AUDIO

GENERATOR

LOAD

RESISTOR

AMPUF1ER

Fig. 9. This setup is seldom used -that in Fig. 8

is preferred since audio -frequency voltmeters are a

lot more popular than audio- frequency milliammeters.

flowing through a 16 -ohm load, the power

consumed by the load is equal to 16 watts

since W= I2R= 1X1X16 =16.

The disadvantage of this technique is that

it is accurate only at the frequency for which

the meter was designed (usually 60 Hz).

To measure the true output capability of

an audio amplifier, use a sine wave input

signal (from an audio oscillator, etc., as

shown in Fig. 8). Turn up the amplifier gain

control and advance the signal generator

output for maximum voltage across the load.

Then compute power consumed by the load

dividing the load resistance into the square

of the indicated voltage

W = E'/R.

However, the output may be distorted. So,

look at the signal across the load with a

scope. It should be a sine wave (Fig. 10). If

not, lower the input signal level until the

output signal is a sine wave and then recom-

pute the undistorted (relatively) output

power -RMS power.

99

@AD POWER IN WATTS

PEAK

N P POWER ! ' INSTANTANEOUS

POWER

AVERAGE

POWER

- TIME

INSTANTANEOUS

VOLTAGE

INSTANTANEOUS

CURRENT

Fig. 10. Sine wave has voltage, current and power

indicated -wattage can never be a negative value.

RMS or Music Power. Now RMS power

is quite different from music power. A sine

wave test signal works the amplifier hard

whereas music is a complex signal with lots

of hills and momentary peaks in it. There-

fore, in terms of music power, the output

rating of an amplifier may be much greater

than its RMS power capability.

When measuring the output of a transistor

amplifier, DC may be present at the output

terminals. To avoid the possible effects of

the DC, connect a large paper dielectric ca-

pacitor (2 mf) in series with the AC volt-

meter, or if you are using a VOM, connect

the test leads to the common and output

jacks. With a VOM low -frequency power

response of the amplifier will not be read

accurately.

Professional audio power- output meters,

such as the General Radio, 583 -A, contain

an impedance matching network, a cali-

brated attenuator and output meter as shown

in Fig. 11. The variable ratio transformer

permits selection of 40 different impedances

from 2.5 to 20,000 ohms. The instrument

measures power from 100 microwatts to 5

watts (in four ranges) at frequencies from

20 Hz to 10 kHz. The meter is calibrated

VARIABLE RATIO

TRANSFORMER

LOSS -

ADJUSTING

NETWORK

METER

ULTIPLIER

Plug -in Add -A- Tester (Model 654) converts popular

Simpson 260 VOM to audio wattmeter almost instantly.

from 0 -50 milliwatts and from 0 -17 db

above one milliwatt. With the meter mul-

tiplier, the total range is from -17 db to

+37 db -with reference to one milliwatt.

A later model, the General Radio 1840 -A,

measures from 100 microwatts to 20 watts

and its frequency response extends from 20

Hz to 20 kHz. The impedance can be set

to 48 different values from 0.6 ohm to

30,000 ohms.

RF Transmission. Scientists have long

tried to transmit electric power through

space without wires. It is being done, but

0

Fig. 11. Variable ratio tran former is input of Relative measurements of RF power can be mode with

block diagram of General Radio 583 -A power meter. Olson's low -cost C8 -67 SWR and Field Strenath Meter_

100 ELEMENTARY ELECTRONICS

with extreme inefficiency. It's called radio.

When you tune in a station radiating 50 kilo-

watts of energy, some of it is consumed by

your receiver -perhaps a fraction of a bil-

lionth of a watt. But, it is power.

When beam transmission is used, much

more of the radiated power is captured by

the receiver. For example, when using a

10 -db gain Yagi antenna with a CB set de-

livering 3 watts into the antenna, the ERP

(Effective Radiated Power) is 30 watts. At

Two -unit instrument consists of Standing Wave Bridge

(Model SWB), Bridge Indicator Unit (Model B/U).

These Ameco units indicate up to 1,000 watts at fre-

quencies between 1.8.225 MHz without added loss.

a distant receiver, the signal will be 10 db

stronger. If a similar gain antenna is used at

the distant receiver, the signal level will be

boosted another 10 db, making the signal as

effective as one from a 300 -watt transmitter.

Thus, a total of 20 db of power gain (100

times) is obtained without increasing the

electric power consumption of either CB set.

A gain antenna provides increased power

free, except for the initial cost of the

antenna.

There actually isn't more power. The

available power is simply concentrated into

a beam instead of being dispersed in all

directions.

Input Power. A transmitter consumes

power from a battery or a power line and

converts it into RF energy. A typical CB

set consumes about 50 watts of primary pow-

er and delivers about 3 watts of RF, making

it about 6% efficient. Primary (AC) input

power can be measured in volt- amperes with

an AC voltmeter and ammeter as shown in

Fig. 4 or by reading the meters built into

an AC power supply, such as the one shown

in Fig. 12. Or, watts can be measured with

a wattmeter.

But input power, as far as the FCC is con-

cerned, is the power consumed by the final

RF ctage of the transmitter (not including

Fig. 12. AC power input can be controlled easily

with this E/CO Model 1078 -K Variable Bench Supply.

Fuses protect instrument- meters indicate output.

filament power). In the case of a CB set,

input power is limited to 5 watts. If the

transmitter delivers 3 watts of RF, its RF

power amplifier efficiency is said to be 60 %.

Input power to a pentode tube can be de-

termined by measuring plate voltage and

plate current, plate and screen current or

cathode current. The voltage is measured

with a DC voltmeter, connected as shown in

Fig. 13, with the transmitter operating but not

being modulated. Combined plate- screen cur-

rent can he measured with a milliammeter,

as shown by breaking the circuit at X1. To

measure plate current only, break the circuit

at X2 and insert the milliammeter there.

Cathode current can be measured by break-

ing the cathode circuit at X3 and inserting a

milliammeter series with it, as shown also in

the diagram.

If the final RF stage uses a transistor, in-

put power is determined by measuring the

collector- emitter voltage and collector cur-

Measure relative transmitter power of Ham, marine,

eammoreiol or CB rias with this small Heathkit PM -2.

MARCH -APRIL, 1967 101

POWER IN WATTS

rent, as shown in Fig. 14, and then multiply -

ing.the indicated voltage and current.

Input power, whether to a tube or tran-

sistor, is equal to the voltage times the cur-

rent in amperes. For example, if the plate

voltage is 200 and the plate current is 25

milliamperes, input power is 5 watts since

200 X 0.025 = 5.

CW (RF)

INPUT FROM

OSCILLATOR

resistance of approximately 50 ohms and

will light brightly when consuming about

two watts. The more brightly it glows, the

higher the RF output. A factory -made

power indicator dummy load employing

three lamps in parallel is illustrated in

Fig. 15.

A lamp can also be used to determine

absolute RF power output by measuring its

brilliance with a photoresistive cell and a

meter, as shown in Fig. 16. The lamp and

photocell should be placed inside a light -

tight enclosure to keep out external light.

RF POWER

AMPLIFIER

RFC

X2

+

X3

% ` -- T -R

MEASURE CATHODE SWITCH

CURRENT HERE

TANK CIRCUIT

MILLAMMETER

TO ANTENNA

VIA RELAY OR

SWITCH

MEASURE PLATE - SCREEN

+ CURRENT HERE

+I VOLTMETER

AUDIO OUT MEASURE PLATE

MODULATION /OUTPUT I VOLTAGE HERE

TRANSFORMER

MODULATOR 8 +.

Fig. 13. Transmitter input -power measurement method varies with the circuit used in the individual trans-

mitter. Usually meter is at some distance from plate or cathode circuit -shunt is in actual current path.

r TANK

CIRCUIT

-- iMILLIAMMETER

MEASURE

COLLECTOR CURRENT

HERE

VOLTMETER

"1-.©_-_

MODULATED

MEASURE

COLLECTOR-EMITTER

VOLTAGE HERE

Fig. 14. Transmitter using transistor in output

has power measured similar to method in Fig. 13.

RF Output Power. The relative RF out-

put power of a transmitter can be deter-

mined by using a filament -type (incandes-

cent) lamp as a dummy load or phantom

antenna, connected directly across the trans-

mitter output. In the case of a CB set, a No.

47 pilot lamp is often used. The lamp has a

This simple instrument is calibrated with

the circuit in Fig. 17. Simply plot a graph

(or make a table) for translating the meter

Fig. 15. Dummy load for low -power transmitter uses

three pilot lamps. Current flow changes resistance.

1

102 ELEMENTARY ELECTRONICS

CONNECTOR TO

TRANSMITTER

OUTPUT MILLI AMMETER

CALIBRATION

CONTROL

L J

LIGHT -TIGHT

ASSEMBLY

DRY CELL(S)

Fig. 16. Increased RF power brightens lamp, changing

resistance of photocell which varies meter current.

VARIABLE AUTO

TRANSFORMER

AC

LINE r

115 24V

TRANSFORMER

Fig. 17. Simple circuit measures power used to cali-

brate RF -power meter shown in Fig. 16 above.

COAX CONNECTOR

,\ TO RF POWER

\ \\ METER

VIA COAX

JUMPER

1

AC

MILLIAMMETER

VOLTMETER

indications into watts -multiplying volts by

amperes to arrive at watts.

The simplest way to measure the RF

power output of a relatively low -power trans-

mitter at frequencies up to 30 MHz (mc),

is to use an RF ammeter (thermocouple

type) in series with a dummy load, as shown

in Fig. 18. Since the load resistance is

known, power is determined by noting the

ammeter reading and computing PR. For

example, if the meter indicates 0.5 amperes,

and the load resistance is 50 ohms, the

power is about 12.5 watts since 0.5 X 0.5

X 50 = 12.5.

COAX

CONNECTOR

RF 11

INPUT

RF

AMMETER

Fig. 18. Dummy load with series RF ammeter measures

current through constant load or resistance (Fig. 3).

50A

DUMMY LOAD

(THREE 150A

CARBON

RESISTORS)

How Much Heat. RF power can also be

measured by converting RF energy into heat

by feeding it into a resistive dummy load

and noting the result" ^g rise in temperature.

A resistive dummy load, connected to the

transmitter output, is sometimes immersed

in water and the increase in water tempera-

ture is measured. Or, the sensing element of

a thermometer (Fig. 19) can be strapped

to a dummy load and the increase in tem-

perature noted.

Fig. 19. Industrial thermometer measures heat rise

in dummy load -a practical way since heat is power.

The RF energy from a transmitter can be

fed into a thermistor connected in a bridge

circuit, as shown in Fig. 20. The RF causes

an increase in the temperature of the ther-

mistor whose resistance drops, unbalancing

the bridge. Power is then determined by re-

balancing the bridge or translating the

amount of indicated unbalance into watts.

COAX PLUG

RF

INPUT

GALVANOMETER

MILLI -

AMMETER

BRIDGE

BALANCE

ADJ.

PRECISION

RESISTORS

Fig. 20. Simplified circuit of bridge -type power

meter. Milliammeter, potentiometer not always used.

A thermocouple can be used to sense the

rise in temperature of a dummy antenna

load (R), as shown in Fig. 21. The higher

the load temperature, the greater the output

voltage of the thermocouple. The millivolt -

meter can be calibrated directly in watts.

COAX

CONNECTOR

RF

INPUT

DUMMY THERMOCOUPLE

LOAD JUNCTION

DC MILLI -

VOLTMETER

MARCH- APRIL, 1967

Fig. 21. Heat in dummy load generates voltage in a

thermocouple junctión- indicating wattage on meter.

103

GM POWER IN WATTS

Another way to use a thermocouple is

shown in Fig. 22. Here the thermocouple is

in series with the dummy load (R). Current

flowing through the thermocouple causes

self heating and generates a DC voltage

which is developed across R and measured

COAX

CONNECTOR

RF

INPUT

THERMOCOUPLE

JUNCTION

RFC

RF FILTER

MILLI-

VOLT-

METER

Fig. 22. Two RFCs and C form RF filter that is used

in many instruments to isolate RF; pass DC to meter.

by the millivoltmeter. The two RF chokes

and C keep the RF out of the meter. The

transmitter must have a DC path across the

antenna connector to allow the DC to flow

around the circuit.

Still another way to measure RF output

power is to use the filament of a tube as the

dummy load, as shown in Fig. 23. The com-

bined resistance of the tube filament and the

resistors should be approximately the same

as the transmitter output impedance. As the

RF heats the tube filament, plate current

flows in proportion to RF watts. The tube

COAX CONNECTOR

Ir I

I

RF,

INPUT

120 n 1H4G CALIBRATION

SHUNT

Wave Ratio) meter. Ordinarily, it is used

in series with a radiating antenna, as shown

in Fig. 24, to measure forward and reflected

power for determining the efficiency of an

antenna system. When set to measure for-

ward power, it indicates transmitter power

output. When set to measure reflected power,

it indicates how much of the power is being

reflected back from the antenna and is being

wasted.

TRANSCEIVER /SWR METER

COAX CABLE /

JUMPER

/DUMMY LOAD

Fig. 24. Connected between transmitter and antenna,

fester indicates power output and reflected power.

The same instrument can be used on the

bench for extended periods of troubleshoot-

ing and testing- measuring transmitter out-

put power -by plugging a 50 -ohm dummy

load into its antenna terminal. Dummy loads

of this type are available from Lafayette

(catalog No. 42C 0902, $0.98) and other

parts stores as well as from Sierra Elec-

tronics (Ford -Philco), Menlo Park, Cali-

fornia. By setting the SWR meter to meas-

ure forward power, it will indicate trans-

mitter output in watts.

More accurate RF wattmeters are avail-

able from Bird and Sierra (Fig. 25) which

contain an internal 50 -ohm dummy load.

12rí

52n DUMMY

LOAD RFC

MILLI-

AMMETER

II 45V

Fig. 23. Heating of filament varies current passed

through diode -connected -triode to indicate RF power.

can be a filament -type diode or a triode con-

nected, as shown, as a diode. The meter is

a DC milliammeter whose range depends on

the type of tube used, and which can be

adjusted with shunt potentiometer R.

CBers, hams and mobile radio service

technicians use less complicated means to

measure RF power. The most popular de-

vice for this purpose is the SWR iStanding

104

Fig. 25. Accurate RF wattmeter is suitable for much

higher power transmitters -fins at rear radiate heat.

Devices of this type employ circuits similar

to those shown in Fig. 26 and 27. They

simply rectify the RF voltage and measure

the resulting DC.

An electronic wattmeter can be used for

measuring RF power. In Fig. 28, two triode

tubes are used in a bridge circuit employing

a galvanometer (zero- center meter such as

ELEMENTARY ELECTRONICS

COAX CONNECTOR

R1

DIODE

RF

INPUT R3

HIGH - RANGE

SHUNT

C2

R4

COAX CONNECTOR

Cl

RF

INPUT

MILLI -

AMMETER RANGE

SWITCH .

CALIBRATION

RANGE SHUNT

SWITCH

LOAD C2

Fig. 26, 27. At top, R4 is shunted across milliam-

meter for high -power range. RF voltage divider

(R1, R2), range switch multipliers measure voltage.

COAX

CONNECTOR LOAD

GALVANOMETER

Fig. 28. Vacuum -tube circuit is similar to that in

a VTVM. Only RF input circuitry is quite different.

a 50 -0 -50 DC microammeter.) With no RF

power input applied, the bridge is balanced

with R4. With RF power applied, the bridge

is rebalanced and the power is read from

the calibrated scale used with R4.

P.E.P. Measurement. So far, we have

been discussing RF- carrier power as pro-

duced by a CW, AM or FM transmitter. The

power output of an SSB (Single -Sideband)

transmitter is expressed in terms of PEP

(Peak Envelope Power.) This is usually

AF GENERATORS

Fig. 29. Two AF generators feed signals into modulator of rig. Dummy load is a necessity for all ex-

tended periods of transmitter testing- particularly with high- powered rigs that can easily span the nation.

=

measured with an oscilloscope when modu-

lating the transmitter with two audio tones

simultaneously (frequently 1000 Hz) and

1800 Hz), as shown in Fig. 29. The power

output is determined by the height of the

scope pattern. The scope must be a wide -

band type capable of working at the RF-

signal frequency. A conventional scope can

be used, as shown in Fig. 30, by connecting

directly to the vertical deflection plates of

the CRT. The deflection voltage is obtained

by tuning L and C to the transmitter

frequency.

RF

INPUT :DUMMY

LOAD

J

DUMMY

LOAD

RF FROM

TRANSMITTER

LINK

VERTICAL

PLATES

Fig. 30. Phase -shifting circuit, top, doesn't need time -

base sweep as in lower method using oscilloscope.

Talk Power. While carrier power is im-

portant (except in an SSB transmitter where

it is absent) it contains no intelligence unless

keyed or modulated.

Maximum useful transmitter range is

achieved under 100% modulation. The RF

power output of an AM transmitter rises

50% above its unmodulated carrier level

when modulated 100% by a sine wave audio

signal. When modulated by voice or music,

the average power output does not increase

as much, but power output peaks can hit

as high as 400% of the unmodulated carrier

level.

41 IMO

SSO TRANSMITTER

OR TRANSCEIVER

MARCH -APRIL. 1y1í7 IUD

POWER IN WATTS

To achieve 100% modulation when using

plate modulation, the power output of the

modulator must be approximately the same

as the transmitter's RF output. In the case

of a 3 -watt RF output CB set, the modulator

usually delivers around 3 watts of audio.

The increase in power output of an AM

transmitter due to modulation can be meas-

ured with an RF output meter. When 100%

modulated by a sine wave test tone, the

power output reading should rise 50 %. If

an RF ammeter is used, as shown in Fig. 18,

the current should rise 22.5 %. For voice

modulation, the indicated power- output in-

crease will be less.

The RF -power output of an FM trans-

mitter, on the other hand, does not increase

under modulation. Instead, the carrier fre-

quency varies with modulation. The more

the frequency is deviated, the greater the

effective talk power. The RF power output

of an FM transmitter is measured with an

RF wattmeter which indicates carrier power.

Modulation level is measured with a devia-

tion meter which indicates frequency devia-

tion, not power.

RF- Power -Meter Connections. In all of

RF power measuring devices, coaxial con-

nectors are shown. Ordinarily, transmitters

are designed to work into a 50 -ohm antenna

system and coaxial connector -most accept

a PL -259 plug. Many measuring instru-

ments are also equipped with SO -239 re-

ceptacles (some use an N or UHF type con-

nector). Connections to the transmitter out-

put are made easier with a coaxial jumper,

Fig. 31. Length of co -axial cable with connectors

makes it easier to connect to transmitter, antenna.

106

Threaded connectors, along left edge of panel, mate

with those on ends of co -ax in Fig. 31. The Olson CB-

24 uses solid state circuitry to make seven important

tests on all types of Citizen's Band transceivers.

such as the one shown in Fig. 31. In this

case the jumper is a length of RG -58/U (50-

ohm) coaxial cable with a PL -259 plug at

each end. Some transmitters, (such as

medium frequency marine and some ham

types) have binding posts and their output

impedance may be other than 50 ohms.

Types of Power. Ordinarily, when deal-

ing with AC, AF and RF, we are concerned

with RMS (Root Mean Square) power.

Like an AC voltage, power has a peak

value which, in the case of a sine wave, is

1.414 times the RMS value or 1.57 times the

average value. It is the RMS value which is

the effective value, and which is normally

given in AC voltage specifications as 120 -

volts AC.

Power consumption may also be related to

time. I.f a load consumes one watt inter-

mittently for 10% of the time, the average

power is only one tenth of a watt. The peak

power of a radar pulse for example could

be 30 kilowatts. If each pulse is one micro-

second in duration and is repeated 500 times

per second, the average power would be only

15 watts since power is present only 2000th

of the time.

A small capacitor can be charged slowly,

consuming a very small amount of power'

over a period of time. When short circuited

it can release a tremendous amount of

power, but only momentarily -for an ex-

tremely short period of time.

Music contains peaks of considerable

power, often much higher than the rated

output of an amplifier. Yet, they can be

handled by a well designed amplifier since

ELEMENTARY ELECTRONICS

4

they occur only during a short period of the

total time. At normal room level, the aver-

age power may be less than 100 milliwatts

but occasional sound peaks might feed sev-

eral watts into the speaker system.

RMS power is measured using the tech-

niques described previously. Peak power can

be determined by measuring the peak volt-

age drop across the load with an oscilloscope

noting the height (deflection) of the trace

and computing the power level. With a scope

you can observe short -duration peaks which

are missed by a meter.

The power consumption of some loads

may vary considerably when power is first

applied. A filament -type (incandescent)

lamp may consume many times its rated

wattage when first turned on since the re-

sistance of its filament is very low when cold

-increasing considerably with increasing

temperature. A motor needs several times its

rated power until it reaches normal running

speed.

You pay for electric power on the basis of

watts consumed over a period of time. If

you consume 6000 watts for 15 minutes and

1000 watts for 45 minutes, you will have

to pay for 2.25 kilowatt -hours since the aver-

age power consumption during the hour was

2,250 watts.

A battery is rated in terms of ampere -

hours. For example, if a battery is rated

100- ampere hours and 10 amperes are

drawn for 10 hours, the battery will pre-

Portable Knight (Model Ten -2) CB tester performs

ten test functions on transmitter and receiver circuits.

MARCH- APRIL, 1967

Sensitive Field Strength Meter (Jerrold Model 704B)

reads down to 5 microvolts for TV and FM intensity

surreys. Lafayette CB Transceiver Tester (below)

measures RF power, field strength, modulation, etc.

sumably be exhausted. If it is a 12 -volt

battery, it will have delivered 1.2 kilowatt -

hours of power (120 watts for 10 hours) .

The efficiency of electronic equipment is

rising, thanks to transistors. The power con-

sumption of a 20 -watt all- transistor amplifier

can be as low as 30 watts whereas a tube

type might consume 100 watts or more.

Where does this wasted energy go? Most of

it is converted into unwanted heat -and

that's what's watt.

107

HEATNKR t967 LITERATURE

* Starred items indicate adver-

tisers in this issue. Consult

their ads for additional in-

formation and specifications.

LIBRARY

RADIO

wrIc

C8- BUSINESS RADIO

SHORTWAVE RADIO

115. Get the fully story on Poly -

Ironics Laboratories latest CB entry

-Carry-Comm. Full 5- watts, great

for mobile, base or portable use.

Works on 12 VDC or 115 AC.

*93. Heath Co. has a new 23 -chan-

nel all- transistor 5 -watt CB rig at the

lowest cost on the market, plus a full

line of CB gear. See their new 10-

band AM /FM /Shortwave portable

and line of shortwave radios.

101. If it's a CB product, chances

are International Crystal has it listed

in their colorful catalog. Whether kit

or wired, accessory or test gear, this

CB oriented company can be relied on

to fill the bill.

48. Hy- Gain's new CB antenna cata-

log is packed full of useful informa-

tion and product data that every

CB'er should know. Get a copy.

107. Get with the mobile set with

Tram's XL'100. The new Titan CB

base station, another Tram great, is

worth knowing about.

111. Get the scoop on Versa -

Tronics' Versa -Tenna with instant

magnetic mounting. Antenna models

available for CB'ers, hams and mobile

units from 27 MHz to 1000 MHz.

45. Catering to 2 -way radio buffs

for 30 years, World Radio Labora-

tories has a new free catalog which

includes the latest CB transceivers,

etc. Quarterly fliers chock -full of bar-

gains are also available.

50. Make your connection with

Amphenol -tune in to the latest on

CB product news with specs and pics

on new gear. Keep informed on

Amphenol's new products.

100. You can get increased CB range

and clarity using the "Cobra" trans-

ceiver with speech compressor -re-

ceiver sensitivity is excellent. Catalog

sheet will be mailed by B &K Division

of Dynascan Corporation.

54. A catalog for CB'ers, hams and

experimenters, with outstanding val-

ues. Terrific buys on Grove Electron-

ics' antennas. mikes and accessories.

96. If a rugged low cost business/

industrial two-way radio is what

you've been looking far, be sure to

send for the brochure on E. F. John-

son Co.'s brand new Messenger "202."

102. Sentry Mfg. Co. has some inter-

esting poop sheets on speech clippers,

converters, talk power kits and the

like for interested CB'ers, hams and

SWL'ers, too.

103. Squires- Sanders would like you

to know about their CB transceivers,

the "23'er" and the new "S5S." Also,

CB accessories that add versatility to

their 5- wattera.

108

KITS

*42. Here's a colorful 108 -page cat-

alog containing a wide assortment of

electronic kits. You'll find something

for any interest, any budget. And

Heath Co. will happily send you a

copy.

*44. EICO's new 48 -page 2 -color

pocket -size short form catalog is just

off the press. Over 250 products: Ham

radio, CB, hi -fi -in kit and wired

form -are illustrated. Also, discover

EICO's new experimenter kit line.

ELECTRONIC PRODUCTS

66. Try instant lettering to mark

control panels and component parts.

Datak's booklets and sample show

this easy dry transfer method.

108. Get the facts on Mercury's

line of test equipment kits- designed

to make troubleshooting easier, fast-

er and more profitable.

67. "Get the most measurement

value per dollar," says Electronics

Measurements Corp. Send for their

catalog and find out howl

92. How about installing a transis-

torized electronic ignition system in

your current car? AEC Laboratories

will mail their brochure giving you

specifications, schematics.

109. Seco offers a line of special-

ized and standard test equipment

that's ideal for the home experimenter

and pro. Get specs and prices today.

HI -FI /AUDIO

26. Always a leader, H. H. Scott

introduces a new concept in stereo

console catalogs. "At Home With

Stereo," offers decorating ideas, a

complete explanation of the more

technical aspects of stereo consoles.

85. Need a tuner? Preamp? Amp?

Tape deck? Then inspect Dyna for

kits or wired units. It's worthwhile

looking at test reports Dyna sends

your way.

110. Get the latest facts on sound

columns. American Geloso Electronics

Inc. offers a ten -page booklet giving

the bows and whys plus method of

installation and arrangement of sound

columns.

15. A name well -known in audio

circles is Acoustic Research. Here's

its booklet on the famous AR speak-

ers and the new AR turntable.

16. Discover how Cueing Control,

anti -scating and other Garrard fea-

tures in the Lab 80 offer tops in audio

listening. 32 -page Garrard Compara-

tor Guide will make you a wiser

buyer -get it.

17. Build your own bass reflex en-

closures from fool -proof plans offered

by Electro- Voice. At the same time

get the specs on EV's solid -state hi -fi

line -a new pace setter for the audio

industry.

19. Empire Scientific's new 8 -page,

full color catalog is now available to

our readers. Don't miss the sparkling

decorating- with -sound ideas.

24. Need a hi -fl or PA mike? Uni-

versity Sound has an interesting mi-

crophone booklet audio fans should

read before making a purchase.

27. An assortment of high fidelity

components and cabinets are described

in the Sherwood brochure. The cab-

inets can almost be designed to your

requirements, as they use modules.

95. Confused about stereo? Want to

beat the high cost of hi -fi without

compromising on the results? Then

you need the new 24-page catalog by

Jensen Manufacturing.

99. Get the inside info on why

Acoustech's solid -state amplifiers are

the rage of the experts. Colorful bro-

chure answers all your questions.

34. You can't pick the tape recorder

you need without a program -and

Sony Superscope has one. Full color

16 -page booklet is as good as your

dealer's showcase. Includes acces-

sories.

TAPE RECORDERS AND TAPE

113. Scotch is the product and it's

made by Minnesota Mining and Mfg.

Co. (3M). Get a packet full of facts

and tape data from 3M and learn all

about your tape recorder and the

tape it needs.

31. All the facts about Concord

Electronics Corp. tape recorders are

yours for the asking in a free book-

let. Portable, battery operated to four -

track, fully transistorized stereos cov-

er every recording need.

32. "Everybody's Tape Recording

Handbook" is the title of a booklet

that Sarkes -Tarzian will send you.

It's 24-pages jam -packed with info for

the home recording enthusiast. In-

cludes a valuable table of recording

times for various tapes.

33. Become the first to learn about

Norelco's complete Carry- Corder 150

portable tape recorder outfit. Four -

color booklet describes this new car-

tridge- tape unit.

35. If you are a serious tape audio-

phile, you will be interested in the

new Viking of Minneapolis line -they

carry both reel and cartridge re-

corders you should know about.

91. Sound begins and ends with a

Uher tape recorder. Write for this

new 20 page catalog showing the en-

tire line of Uher recorders and acces-

sories. How to synchronize your slide

projector, execute sound on sound,

and many other exclusive features.

ELEMENTARY ELECTRONICS

HI -FI ACCESSORIES

112. Telex would like you to know

about their improved Serenata Head-

set -and their entire line of quality

stereo headsets.

39. A 12 -page catalog describing the

audio accessories that make hi -fi liv-

ing a bit easier is yours from Switch -

craft, Inc. The cables, mike mixers.

and junctions are essentials!

98. Swinging to hi -fi stereo head-

sets? Then get your copy of Superex

Electronics' 16 -page catalog featuring

a large selection of quality headsets.

104. You can't hear FM stereo un-

less your FM antenna can pull 'em in.

Learn more and discover what's avail-

able from Finco's 6 -pager "Third Di-

mensional Sound."

AMATEUR RADIO

46. A long -time builder of ham

equipment, Hallierafters will send you

lots of info on the ham, CB and com-

mercial radio-equipment.

SCHOOLS AND EDUCATIONAL

114. Prepare for tomorrow by

studying at home with Technical

Training International. Get the facts

today on how you can step up in

your present job.

59. For a complete rundown on

curriculum, lesson outlines, and full

details from a leading electronic

school, ask for this brochure from the

Indiana Home Study Institute.

*61. ICS (International Corre-

spondence Schools) offers 236 courses

including many in the fields of radio,

TV, and electronics. Send wr Lice

booklet "It's Your Future."

*74. How to get an F.C.C. license,

plus a description of the complete

electronic courses offered by Cleve-

land Institute of Electronics are in

their free catalog.

105. Get the low -down on the latest

in educational electronic kits from

Trans -Tek. Build light dimmers.

amplifiers, metronomes, and many

more. Trans -Tek helps you to learn

while building.

TOOLS

*78. Learn about Xcelite's line of

pliers and snips, specialized for radio,

TV and electronic work. Xcelite's

hand tools offer many advantages

worth looking into. Bulletin N464

and N664.

TELEVISION

*70. The Heath Co. now has a 19"

color TV to complement their 21"

and 25" models. A new B &W port-

able model will be a hot seller for

the mobile set. Get the facts today!

72. Get your 1967 catalog of Cistin's

TV, radio, and hi -fi service books.

Bonus -TV tube substitution guide

and trouble- chaser chart is yours for

the asking.

29. Install your own TV or FM an-

tenna! Jefferson- King's exclusive free

booklet reveals secrets of installation,

orientation; how to get TV -FM trans-

mission data.

97. Interesting, helpful brochures

describing the TV antenna discovery

of the decade -the log periodic an-

tenna for UHF and UHF -TV, and

FM stereo. From JFD Electronics

Corporation.

ELECTRONIC PARTS

*1. Allied's catalog is so widely

used as a reference book, that it's re-

garded as a standard by people in the

electronics industry. Don't you have

the latest Allied Radio catalog? The

surprising thing is that it's free!

*2. The new 1967 Edition of Lafay-

erte's catalog features sections on

stereo hi -fi, CB, ham gear, test equip-

ment, cameras, optics, tools and much

more. Get your copy today.

*3. Bargains galore! Parts, tools,

test equipment, radios and many more

specials at ultra -low prices. Progres-

sive Edu -Kits will send latest catalog.

*4. Olson's catalog is a multi-

colored newspaper that's packed with

more bargains than a phone book has

names. Don't believe us? Get a copy.

*23. No electronics bargain hunter

should be caught without the 1967

copy of Radio Shack's catalog. Some

equipment and kit offers are so low.

they look like misprints. Buying is

believing.

*5. Edmund Scientific's new cata-

log contains over 4000 products that

embrace many interests and fields.

It's an 148 -page buyers' guide for

Science Fair fans.

*106. With 70 million TV's and 240

million radios somebody somewhere

will need a vacuum tube replacement

at the rate of one a second! Get Uni-

versal Tube Co.'s Troubleshooting

Chart and facts on their $1 flat rate

per tube.

7. Whether you buy surplus or

new, you will be interested in Fair

Radio Sales Co.'s latest catalog -

chuck full of surplus buys for every

experimenter.

8. Want a colorful catalog of

goodies? John Meshna, Jr. has one

that covers everything from assem-

blies to zener diodes. Listed are gov-

ernment surplus radio, radar, parts,

etc. All at unbelievable prices.

6. Bargains galore, that's what's

in store! Poly -Paks Co. will send you

their latest eight -page flyer listing the

latest in merchandise available, in-

cluding a giant $1 special sale.

10. Burstein- Applebee offers a new

giant catalog containing 100's of big

pages crammed with savings includ-

ing hundreds of bargains on hi -fi kits.

power tools, tubes, and parts.

11. Now available from EDI (Elec-

tronic Distributors. Inc.) a catalog

containing hundreds of electronic

items. EDI will be happy to place you

on their mailing List.

12. VHF listeners will want the

latest catalog from Kuhn Electronics.

All types and forms of complete re-

ceivers and converters.

ELEMENTARY ELECTRONICS, Dept. 367

505 Park Avenue, New York, N. Y. 10022

Please have literature whose numbers I have en-

circled sent to me as soon as possible. I am enclos-

ing 25G (no stamps) to cover handling charges.

1 2 3 4 5 6 7 8 10 11 12 15 16 17

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105 106 107 108 109 110 111 112 113 114

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of booklets requested

7

NAME (Print clearly)

ADDRESS

CITY STATF ZIP CODE J

MARCH -APRIL, 1967 109

Flip -Flops

Continued from page 36

can easily build for demonstration purposes.

It is a free -running multivibrator whose

values were selected to generate a continuous

tone in the audio range. The tone, heard in

the speaker, is variable from about 100 Hz

(cycles) to several thousand . Hz, as con-

trolled by the 500K potentiometer. The tran-

sistors may be any general- purpose audio

pnp types (GE -1, 2N107, etc.). The circuit

can oscillate with battery voltage from about

3 to 9 volts, but output is louder on the high-

er voltage. A circuit of this type produces a

tone which is slightly different in quality

from that generated by a conventional sine -

wave oscillator. Rather than sounding color-

less, like a pure tone, it is fuller and musical.

It's due to the squared -off wave produced by

flip -flop action. It is rich in harmonics, or

multiples, of the fundamental pulse fre-

quency. The output transformer which feeds

the speaker is a 2K to 3.2 -ohm type com-

monly found in AC -DC table radios.

Viewing the Flip -Flop Signal. We con-

structed the practical circuit of Fig. 6 and

threw a scope across key circuit points to

obtain pictures of two signals; feedback and

output pulses in one stage. Both photos are

seen in the schematic of Fig. 7. One is the

sawtooth shape, representing the charge -

discharge action of the coupling capacitor,

the other is a square output wave which

shows the on and off conditions of the tran-

sistor. Before tracing it in detail, recall the

basic action of a pnp transistor. A positive -

going signal applied to its base reduces cur-

rent through the collector circuit, a condition

which drive the transistor into cutoff. Output

voltage will be high (maximum negative).

Examine first the feedback signal (lower

left) applied to the base or input side. That

signal is being fed back from the second

stage. The wave begins with a sharp, upward

thrust in the positive direction, which repre-

sents charging of the capacitor in a few

millionths of a second. Applied to the base,

it causes rapid cutoff of collector current.

This is seen in the top scope trace which

monitors the collector; voltage is rapidly in-

creasing in the negative -going (downward)

direction. In comparing input and output

signals, you will see that a phase reversal has

occurred since positive input has produced

negative output.

Next, the input signal at the base corn-

110

mences to taper away, representing the rela-

tively slow discharge of the capacitor. Col-

lector voltage, however, is still maintained at

full cut -off condition. Only when the capaci-

tor reaches nearly full discharge will it re-

lease the transistor from the cutoff condition.

In the interests of simplicity we've shown

only signals for one stage during a half

cycle. The identical sequence follows in the

second stage to complete a full cycle of flip -

flop action.

Electronic Switching. We've seen the

flip -flop in counting and oscillator circuits.

Our final application illustrates electronic

switching. The circuit in Fig. 8, a practical

device described in RCA semiconductor

literature, eliminates thermal switches or

other mechanical contacts. The circuit might

be used to operate a flashing lamp for emer-

gency use on the highway.

The two transistors at the left form a free -

running multivibrator which produces a

square wave approximately 69 times per min-

ute. This signal is used to gate the third

transistor (2N270) on and off. Output of the

transistor then controls the base of the final

transistor, a 2N441, which can handle the

heavy lamp current. Since all switching func-

tions occur within the semi -conductor ma-

terial, there are no contacts to get dirty,

oxidize or wear out. Life of the switch can

be considered indefinite.

Now that you have the theory of flip -flops

under your belt and have mastered a few

simple, but practical, circuits, you are on your

own for dreaming up any number of zann

applications for flip -flops.

n

ELEMENTARY rELECTRONICa

March/April 198?

1111111 11111 11 11 1111 rrr11111111111111 n rnn nnnnrnnnrr rrrnrnn,n,rnnnnnn

ELEMENTARY ELECTRONICS

FCC Q & A

Continued from page 78

determining voltage divider so that as the

temperature increases the forward base bias

is reduced. Alternately, a germanium diode

or transistor junction can be used as part of

a voltage divider in this application.

Q Draw simple schematic diagrams of the

following transistor circuits and explain their

FEEDBACK

COUPLING

R1

LI

RFC

Fig. 6. Basic Colpitts oscillator circuit uses two

capacitors in tuned circuit. Either R2 or RFC is

needed as collector load of DC current -RF goes

through tuned circuit (L1 and split capacitor CC).

principle of operation. Use only one voltage

source: (a) Colpitts -type oscillator, (b) Class -

B push -pull amplifier, (c) A pnp transistor

direct coupled to a npn type.

A (a) See Fig. 6.

(b) See Fig. 5.

(c) See Fig. 5.

ittninillimiJlzu.numitilitatirtoirml.11111111militnnimosmtovimmnnimillimamillitnimilimilminumin111111nnlInmmn

"... and the rest of the time I use it

for tracking satellites!"

rt

MARCH- APRIL, 1967

Get

an early start

in electronics

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ELEMENTARY

ELECTRONICS

The magazine that serves up elec-

tronic theory in pleasant spoon-

fuls and reinforces the knowledge

you gain with exciting and useful

projects.

Special Introductory Offer

12 issues for only $4.00. SAVE 50%

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Elementary Electronics

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who vacation in the out-of-doors. Features all facets of

mobile camping and wilderness treks by foot,

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Mobile Life 50C -For present owners and prospective

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Ham Shack Heart

Continued from page 45

to either the normal speaker- headphone ar-

rangement or to a telegraph converter. This

latter is a vacuum -tube device employing a

sensitive polar relay which accepts the re-

ceiver output, amplifies it and transfers it

to a conventional telegraph sounder. The

owner of this control center is a member

of a charmed circle who often work each

other in the Continental Morse telegraph

code rather than International, hence the

sounder arrangement! Now to the right of

the main panel, there are two rotary switch-

es just below the slide- switch sub -panel. The

left hand rotary switch connects the output

of any of the four receivers to the speaker,

headphones or telegraph sounder as selected.

The other rotary switch provides two values

of audio -tone filtering as well as a position

to cut the filter out of the circuit.

Above the right hand slide- switch sub -

panel is a potentiometer to control the audio

noise limiter -a slide switch directly below

it switches it in or out of the circuit. In a

horizontal row along the bottom of the

panel, eight fuses protect the four trans-

mitters and four receivers. The main fuse

(to the right of the clock) and the main

switch (to the left of the clock) remove all

power from the entire control unit -turning

off all equipment connected to it by merely

flipping one switch. The clock, of course,

has a separate, fused circuit which remains

"hot" at all times. Fusing for the clock,

RF- monitor power supply and the telegraph

converter are on the back panel. While

conveniently reached for possible replace-

ment, these fuses were not deemed sufficient-

ly important to warrant front -panel space

as they are not pertinent to actual com-

munication operation.

The indicator lights (one for each re-

ceiver and transmitter and one for the main

incoming power as well as one for the keying

monitor supply) are of novel design. They

are small neon lamps with a built -in resistor

for 11.5-volt operation and are press -fitted

into appropriate panel holes. Amber jewels

are used for the receivers and keying moni-

tor and red for transmitters and main power.

All external wiring from the control center

to the equipment is terminated in a series

oI plugs anu sucxels un we rear parlel-

eliminating all screw or solder type terminals.

112

The complete control center can be un-

plugged from all equipment and removed

in less than a minute. With the exception

of the transmitter and receiver AC- supply

plugs, no two plug- and -socket assemblies are

alike, preventing any misconnection. Should

the two AC power plugs (both of the octal

type) be reversed in connecting, no harm

is done. The transmitter switches would

then simply activate the receivers and vice -

versa which would immediately make the

transposition obvious. As a further safe-

guard however, one plug and socket assem-

bly is painted bright red, the other brilliant

green. While hardly in a class with Gemini

Control, this versatile control center appar-

ently overlooks nothing which could be con-

sidered as a station operating convenience

and most certainly provides finger -tip con-

trol of everything, directly from the operat-

ing position.

Design Your Own. From the foregoing

description and the accompanying illustra-

tions it should appear rather evident that

wide leeway in the design of a control center

is possible. From the simplest little transmit-

ter- receiver AC control box to the "grand-

daddy" unit, these control centers offer a

broad range for exercise of ingenuity and in-

itiative to produce a control center to suit your

equipment. Individual ideas of the "home -

brew" designer and builder can run ramp-

ant. Regardless of the end result, grouping

controls at one central point is about the

handiest and most convenient station layout

imaginable. The block diagrams offer some

ideas for various control groupings; almost

any item of station equipment can be deleted

or added and the arrangements shown are

sufficiently flexible to provide for wide lee-

way in modifications to suit the builders'

fancy.

mum n Aunt= n --"

ELEMENTARY ELECTRONICS

50)t Transistor Tester

Continued from page 66

or no resistance change is noted upon apply-

ing base current, the transistor cap be as-

sumed to be defective.

Base Leakage. The next test checks Icbo,

the collector -to-base leakage current with

emitter open, in terms of resistance or cur-

rent if desired. Excessive Icbo leakage biases

or shifts the transistor operating points up-

wards to higher collector currents- leading

to excess heating, large -signal distortion and

other effects. A transistor with higher -than-

normal Icbo leakage may or may not oper-

ate properly depending on the particular cir-

cuit and other factors.

Switch the VTVM to the R X 10K -ohm

range. Maximum test current on this range

is 15 microamperes with leads shorted. Open

Si and connect the positive -voltage ohms

lead to the base. The indicated resistance

should fall in the upper third of the scale

corresponding to a test -lead current of five

microamperes or less. Most transistors will

read higher than one megohm on this ohms

range -the lower the resistance, the higher

the leakage current.

A high -leakage transistor will indicate near

zero ohms on the R X 10K -ohms range. An

appreciable downward drift of the meter

pointer indicates unstable leakage current

leading to transistor drift. No sharp division

line exists, but resistance readings well below

200K at these test voltages indicate higher -

than- normal leakages for low -power transis-

tors. Silicon transistors, which have extreme-

ly -low Icbo leakages, will read near infinity

on the R X 10K range.

These tests and resistance guidelines were

established by checking a number of low -

power germanium junction transistors in-

cluding not only good but also defective

transistors to insure their rejection. Although

infrequently, a transistor passing these tests

may fail to operate properly in the circuit

(at normal voltages) if the transistor has an

abnormally- rising Icbo leakage current with

an increase in collector voltage.

When running these tests, do not inad-

vertently set the ohms range to R X 1 ohm.

This range supplies about 150 milliamperes

of test current -which could damage some

converter -mixer type transistors. And just

reverse all polarities shown and mentioned

when checking npn transistors.

MARCH-APRIL, 1967

Way -Down SWL'ing

Continued from page 79

and Iraq are also members of the high

power society. Relay stations of the BBC

and the VOA make Malaysia and the Ryu-

kyu Islands voices of the Far East. Aus-

tralian territories of Papua and New Guinea

operate regional stations of 10 kw each.

Europe. Very few European transmitters

broadcast on 90 meters, mainly because re-

gional broadcasting can be done on the stand-

ard broadcast and FM bands (without the

high levels of static, usual in tropical areas,

on these bands). All of the European sta-

tions broadcasting on 90 meters are high

powered -such as the BBC in London,

Radio Budapest in Hungary, and Radio Free

Europe in Germany.

South America. With South America be-

ing mostly tropical, many stations operate on

this band. These stations, however, are pre-

dominantly low powered. Radio TV Do-

minicana, Santo Domingo, is one of the few

South Americans running over 5 kw in this

band. Since this country has just been

through a rebellion, logging it is fun.

Sky Wires. Antennas for the 90 -meter

band present no problem. A longwire an-

tenna is sufficient. Generally speaking, log-

ging Africa is easier on the east coast, and

Asia easier on the west coast. QSLing these

stations require a better than average report

because of their regional broadcasting.

Listening on 90 meters offers you a chance

at logging many rare stations. Just keep

those ears ready for anything and take a slow

twirl on that dial!

,,..o,,,,,,.,,,,,,,,,,,,,,,,,,,,.,.mm.lii,loli,.,..i..,mu..,ium,m.,,i,n .,,,,.,,,,, mm,,,,,

"While the current was going through,

did you notice any grid leak ?

113

L

Tenna -Blitz

Continued from page 96

board. To make connections, simply push the

component leads through the holes in the

board, twist them together, and solder.

There's no need for terminals.

If you're building the unit as shown, form

a bracket for mounting the perf -board from

scrap aluminum (as shown in the photo-

graphs). The bracket provides the ground

connection for the circuit via a solder lug

which is held in place by the bracket mount-

ing screw.

Wide variation is permitted in component

values. R1, which controls the length of the

flash, may be eliminated and replaced with a

jumper for a "quick burst" of light. The

higher you make the value of R 1 the longer

the flash will be. But do not exceed 470

ohms. If the flash is too long (caused by

more than 470 ohms) Q2 will overheat and

literally burn up.

Protection resistor R2 (2700 ohms) allows

experimentation with different transistors. If

you use the transistors specified in the parts

list R2 may be eliminated and replaced with

a jumper. R3 provides a slight bias for Q1

and its value may range from 470K to 2.2

megohms.

The value of capacitor Cl should be be-

tween 2 and 4 microfarads. Too small, the

lamp won't blink; and too large, the period

between flashes will be excessive.

Lamp I1 must be a type 48 or 49 or an

equivalent 2 -volt, 60 milliampere lamp. It is

press -fit into a 7/i -inch rubber grommet (no

need for the expense of a lamp holder). Just

make certain you solder the wires to I1 very

quickly -use flux if necessary to insure a fast

flow joint.

A Touch Of Schmaltz. If you use the

Tenna -Blitz as a car beacon it is normally

placed on the rear deck or the dashboard. But

you can attach a small clip to I1 and mount it

on the tip of the antenna running the wires

back to the control unit inside the car. Of

course, while the local hoodlums will pass -by

the blinker on the dash -thinking it's a

child's toy, you can almost bet a tower light

on the antenna will attract them from every

nook and gutter (don't say we didn't warn

you) .

Can you power the Tenna -Blitz from your

12 v. car battery? No! The excess current

will destroy Q2 and I1.

114

Speech Processer

Continued from page 54

_.]

Using the Speech Processor. To use the

speech processor simply unplug the micro-

phone from your rig and plug the micro-

phone into the Speech Processor and plug

the Speech Processor into the microphone

input of your rig. Turn on the AC. Wait a

few seconds for voltages to stabilize and with

the level control set to about mid -range make

a call. Unless a low- output dynamic micro-

phone is used the HI -LO gain switch (SI)

can be left in the low -gain position. With a

scope (or the help of a friend) adjust the

level control (R22) for just a little less than

100% modulation.

Now move the microphone to arm's length

and talk in a normal level voice. Modulation

should stay about the same. The bass and

treble controls are adjusted to suit individual

preferences and band conditions; with both

controls fully advanced the voice should

sound more penetrating and less natural.

The clipper will probably be used only

when conditions are bad as there is some loss

of naturalness. However, this is a small price

to pay for the difference of making and losing

a contact.

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MARCH -APRIL, 1967 115

SSB Is In!

Continued from page 60

peaks, it is accepted within legal limits pre-

scribed by the FCC.

Receiving Sideband. Sideband trans-

mitting systems may seem complex at first

glance but it was probably the receiver that

held back single sideband acceptance for

many years. And this despite the fact that no

special circuits are needed to receive single

sideband on a communications receiver that

contains a BFO for making code signals

audible. The problem was mostly a matter of

receiver selectivity, stability, or freedom from

drift. Picking up single -sideband is mainly a

matter of reinserting the carrier. In any re-

ceiving system, the detector must reverse the

process that began back at the transmitter.

As you may recall, a carrier was required to

create sidebands. It's also necessary to re-

create original audio. It's the mixing process

all over, again. When the conventional AM

transmitter sends carrier and sidebands to the

receiver, the detector heterodynes them to

produce audio. Using our earliest example:

a 600 -kHz carrier mixes with a 601 -kHz

sideband to produce a 1 kHz difference .. .

which is the original audio. (The lower side -

band contributes to the identical result). But

an incoming single sideband signal is carrier -

less. This is easily corrected by turning on the

receiver's BFO.

Tuning a single -sideband signal on a re-

ceiver is done slowly and with care. The

reason is that the BFO must inject a signal

which corresponds exactly to the frequency

of the original carrier -if it had been trans-

mitted. As the BFO dial is adjusted, an in-

coming speech transmission first sounds like

a signal of tremendous distortion. Then it

assumes a characteristic "Donald Duck"

quality. But when tuning is on the nose, the

sideband signal can be crystal clear and in-

telligible, even during difficult band condi-

tions. So effective is single sideband that the

new definition for conventional AM. When

that day comes, AM may very well mean

"Ancient Modulation."

Detectors

Continued from page 92

provide forward bias causing collector cur-

rent to flow in proportion to signal strength.

Positive signal excursions provide reverse

bias and have no effect. Hence, we have the

solid -state version of the plate detector.

Other Detectors. There are also other

kinds of detectors. Some, such as level de-

tectors, sense changes but not, necessarily

intelligence. A superheterodyne radio, for

example, has two detectors, but only one is

called a detector these days. Long ago, the

mixer (frequency converter) was called the

"first" detector and the AM demodulator

Fig. 35. Video detector using triode in cathode-

follower hookup. Coil labeled "L" serves as RF choke.

Fig. 36. Video detector using pentode. Both this cir-

cuit and the one appearing in Fig. 35 are AM types.

was called the "second" detector. The fre-

quency converting mixer is a detector since

it may be a rectifier or a non -linear amplifier.

Television sets have at least three de-

tectors, a frequency converting mixer, an

audio detector (FM) and a video detector

(AM). The latter can be a diode or employ

a triode, as in Fig. 35, or a pentode, as in

Fig. 36. The former is an infinitive imped-

ance type (cathode follower) whereas the

latter is a plate detector. In both circuits,

coil L is an RF filter.

It is not possible to cover all type of de-

tectors here. Basically, AM detectors are

rectifiers or non -linear amplifiers, and FM

detectors are essentially sensors of phase or

frequency.

116 ELEMENTARY ELECTRONICS

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