01A03 Elementary Electronics 1967 03 04

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HowTo

UA

ELEMENTARY

SÑÓTS

EL

MARCH -APRIL 75C

PROJECTS

Add

DAY
p
RAINY
FOR

TALK
POWER
to CB and

Alarm
Line Failuree
r Pack
$699 project Powe
Stomper
$349 Electr
Electronic Foot

$925

Ham

rigs

design notes

for a

HAM
CONTROL
CENTER
THE INSIDE
STORY ON
DETECTORS: AMIFMIVIDEO
FLIP- FLOPSELECTRONICS
THE TWO -CYLINDER ENGINES OF Editors
of
iCr

By the

RADIO -TV EXPERIMENTER

Introducing EICO's New "Cortina Series "!
Today's electro-technology makes possible near -perfect
stereo at moderate manufacturing cost: that's the design 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.

New EICOCRAFT'' easy -

to -build solid -state elec-

tronic TruKits:

4

great

for beginners and
sophisticates alike. As

!`

professional

as the
standard EICO line

t

only the complexity

You hear all the action -packed capitals of the

NEW EICO 888 Solid -State

world with the NEW EICO 711 "Space Ranger"
4-Band Short Wave Communications Receiver
operators, ship -to- shore, aircraft,
Coast Guard, and the full AM band. 550KC to
30MC In four bands. Selective, sensitive superhet, modern printed circuit board construction.

-

plus ham

Easy,

-

Now you can tune -up, troubleshoot and test your own car or
boat.
Keep your car or boat engine in
tip -top shape with this completely

-fast pinpoint tuning: Illuminated slide.

Is

pre -drilled copper plated etched printed
circuit boards; finest parts; step -by -step instructions; no technical experience needed
just soldering iron and pliers. Choose from: Fire

Engine Analyzer

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.

-

reduced to make kit.
building faster, easier,
lower cost. Features:

Alarm; Intercom; Burglar Alarm; Light Flasher;
"Mystifier "; Siren; Code Oscillator; Metronome;
Tremolo; Audio Power Amplifier; AC Power Supply. From $2.50 per kit.

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 including 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.

-

More "ham" for your dollar than ever
with
the one and only SSB /AM /CW 3 -Band Transceiver Kit, new Model 753
"the best ham
transceiver buy for 1966"
Radio TV Experimenter 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
$299.95 wired.

priced at $199.95 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 transmitter tuning controls. 23 crystal -controlled
transmit and receive channels
all crystals
supplied. Rear -illuminated S /RF meter. Transistorized 12VDC and 117VAC dual power supply.
Wired only, $169.95. Positive- Negative Ground/
Mobile Marine Modification kit (optional $5.95).

-

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 interested in:
D test equipment
D ham radio
D stereo /hi -fi
D Citizens Band radio

automotive electronics
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.

Name
Address

Model 232 Peak -to -Peak VTVM. A must
for color or 88W TV and Industrial
use. 7 non -skip ranges on all 4 func-

City

l

State

tions. With exclusive UniProbe.W
$29.95 kit, $49.95 wired.

Zip
J

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
into cold cash, or begin a whole new career -in
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 professional 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 electronic 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 experimentation, 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
future in this fast -growing field!
Make up your mind right now to find out how
I. C. S. training in Radio-TV- Electronics can pay
off for you. See how it can help you cash in on
the tremendous demand for men skilled in installation, maintenance and servicing of radios, TV
sets, hi -fis, computers, automation systems and a
host of other space -age devices. Clip and mail
the coupon below. You'll receive 3 valuable free
booklets-including ample lesson. They'll show
how you can land in this big -money field fast!
Coupon brings 3 valuable FREE booklets.
MAIL IT TODAY!

INTERNATIONAL CORRESPONDENCE SCHOOLS

I

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.

4,

Electronic Fundamentals
Electronic Instrumentation
Computer Fundamentals
Radio -TV Servicing

Hi -Fi /Stereo & Sound
Systems
General Electronics

Electronics Technician

Electronic Principles for
Automation

Industrial Electronics
Engineering

SemiconductorTransistor Circuits

FCC Radiotelephone

Name

E

Industrial Electronics
Telephony
Other (please specify)

Licenses

Age

Address

City

State

Occupation

Working Hours
I

am

a

A.M. te

P.M.

Convenient payment plan

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

II.
MARCH- APRIL, 1967

Zip Code

Employed by

Training Programs for Industry

J
1

ELEMENTARY

"' "

,

" " "R

ELECTRONICS

NOW THERE ARE

138 RADIO

SHACKS COAST TO COAST!
ARIZONA

--

Phoenix

ARKANSAS

Little Rock
Anaheim,
Bakersfield, Downey, Garden
Grove, La Habra, Long Beach,

CALIFORNIA

Los Angeles, Mission Hills,

Mountain View, Oakland,

THEORY

*
*

'*

29

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

tronics
37
55
81

97

**

61

Ham Shack with a Heart
Transmitter Speech Processor
Power Pack: Experimenter's Six or Niner

66

50¢

71

Line Failure Alarm
Electronic Foot Stomper

93
95

--- - -

Stamford, West Hartford
Orlando
FLORIDA
GEORGIA
Atlanta
ILLINOIS Chicago
KANSAS
Wichita
LOUISIANA
New Orleans
MAINE- Portland
Langley Park
MARYLAND
MASSACHUSETTS
Boston,
Braintree, Brockton, Brookline,
Cambridge, Dedham,
Framingham, Lowell, Medford,
Natick, Quincy, Saugus,
Springfield, Waltham, West
Springfield, Worcester
MICHIGAN
Detroit
MINNESOTA- Minneapolis,

Transistor Tester

Tenna Blitz

FEATURES

'

16
28
46
47
64
68
79
80

Tips from a Technician's Notebook
Wide World of Electronics
Great Day for QSL
Lafayette RK -840 Stereo Tape Recorder
Space -age Showcase
Space Shots: Countdown for DX

'

St. Paul

Low Down on Way Down QSL

Arecibo Listening
in the News
Ask Me Another
e/e Etymology
En Passant-Chess Column
Imagineering
Home -Study Bluebook
FCCQ &A
Literature Library

Len

"ELEMENTARY

Buckwalter- K1ODH /KBA4480, John

Smith- W5MQL,

o.,
AAA

EIECrAONICs

-

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
and the ELEMENTARY
ELECTRONICS' Editorial Staff.
Cover Photo by Leonard Heicklen
2

Tulsa

OREGON
Portland
PENNSYLVANIA
Philadelphia, Pittsburgh
Providence,
RHODE ISLAND

Cover Highlights

AUTHORS IN THIS ISSUE:

- -- - -

MISSOURI
Kansas City, St.
Joseph, St. Louis
NEBRASKA
Omaha
NEW HAMPSHIRE
Manchester
NEW JERSEY- Pennsauken
NEW MEXICO
Albuquerque
Albany,
NEW YORK
Binghamton, Buffalo, New
York, Schenectady, Syracuse
OHIO
Cincinnati, Cleveland
OKLAHOMA
Oklahoma City,

DEPARTMENTS
6 Newscan -Electronics
18
24
25
67
74
75
108

Francisco, Santa Ana, Santa
Monica, Torrance, West
Covina
COLORADO
Denver
CONNECTICUT- Hamden,
Manchester, New Britain, New
Haven, New London, Orange,

-

Those Electronic Diagrams
SSB Is In!
The Inside Story on Detectors
Power in Watts

CONSTRUCTION
43
49

Reseda, Sacramento, San
Bruno, San Diego, San

4AAM,'OiY

,4Mip Powx

PveM

East Providence
Chattanooga,
TENNESSEE

Memphis, Nashville

Abilene, Arlington,
Austin, Brownsville, Corpus
Christi, Dallas, Fort Worth,
Houston, Lubbock, Midland,
San Antonio, Sherman, Waco
UTAH -Salt Lake City
Arlington, Virginia
VIRGINIA
TEXAS

Beach

-

WASHINGTON
Seattle

-

Everett,

ELEMENTARY ELECTRONICS

SPECIAL GET - ACQUAINTED OFFER
FROM THE COUNTRY'S LEADING
PARTS 01 TRIBUT I

RADIO
SHACK

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;:
ranges. AC /DC volts: 0 -1000
5
in 3 ranges; 0-150 ma DC; 0100 KU. 22 -4027.

HOBBYIST'S ONE TUBE RADIO KIT
Tunes

2- TRANSISTOR AM RADIO KIT

AM Band

With Crystal Earphone
Solid State Circuitry
Ideal for Beginners or
Do- lt- Yourselfers

from 540 -1600 KC
Hi -Q Coil for
Top Sensitivity

3 49

28-001

ß8-002

Fun to use; easy enough for anyone to build.

Fine reception across the entire broadcast band!

ELECTRONIC ORGAN KIT

WIRELESS MIKE /TRANSMITTER KIT

Better than 1 Octave
Range! Easy to Play!
A Family Favorite!

Broadcasts into Any
AM Radio at Ranges up
to 20 Feet!

28-003

298

28 -004

FILL OUT COUPON AND MAIL TODAY TO:
RADIO
SHACK

Your Choice of
Either $2 Book
at Half Price!
solid state
projects
from a simple
radio to a 2 -way
intercom system.
Each book entirely
different: Book 1,
62 -1050; Book 2,

...

VOM, 22-4027

Organ, 28.004

-Tube Radio, 28 -001
2- Trans. Radio, 28-002

Book
Book

Wireless Mike, 28 -003

Please send me a FREE 1967 Rodio Shack Catalog

I

# I,

#2,

62 -1050
62 -2025

Name (print)

Street

City

slightly more

MARCH -APRIL, 1967

East: 730 Commonwealth Ave., Boston, Mass. 02215
West: 1515 So. University Dr., Ft. Worth, Tex. 76107

Please rush me the item I've checked below.
,
plus 500 for postage and handling:
I enclose $

50 easy -to -build

advanced, 62 -2025

5 95

Play songs on an organ you built yourself!

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

SAVE $100

398

State

L.

Zip

EE

-367

..a
3

Now there's a full line of

fLfMFN(gqY

ELECTNONICS
MARCH /APRIL 1967

Vol. 4 No.

1

Dedicated to America's Electronics Experimenters

Soldering Tools
for all soldering needs

JULIAN M. SIENKIEWICZ
WA2CQL/KMD4313

Editor

RICHARD A. FLANAGAN

Managing Editor

ELMER C. CARLSON

Technical Editor

KOD1752

A

Each model outperforms any other soldering
tool of comparable size and price. All have

JIM MEDLER

Art Editor

replaceable tips of solid copper, instant heat,
long reach, and rugged construction that
means long-life, dependable performance.

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

Production Director

PINTO

F.

CARL BARTEE

Production Dianager

HELEN GOODSTEIN

Assistant Production Manager

DAVID COHN

Promotion Director

WILFRED M. BROWN

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

Weller Dual Heat Guns
Feature trigger -controlled dual
heat, efficient double -barrel design, long -life tip, and work spotlight. Available in three wattage
ratings, and in handy soldering
gun kits. Priced from $6.95 list.

$41$,

SOLDERING IRON

KIT

:1;xr';+.

ELEMENTARY ELECTRONICS, Vol. 4, No.
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., 312-5270330; 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 advertising representative: Jim Wright, 4 N. Eight St., St. Louis, CH.1 -1965.
1

Weller MARKSMAN Irons
Best for intricate soldering or continuous -duty operation. Five sizes
-all lightweights -with replaceable, premium -plated Vs" to Vs"
tips. From $2.98 list. Also in complete kit form with a soldering aid,
solder and 2 extra soldering tips.

T ry them all

... at your electronic parts distributor!

WELLER ELECTRIC CORP., Easton, Pa.
WORLD LEADER IN SOLDERING
4

TECHNOLOGY

vi?

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
mailing office. Copyright 1966 by Science and Mechanics Publishing Co.

ELEMENTARY ELECTRONICS

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

any previous experience in electronics. The free book
shown here tells you how.
In the last 15 years, the electronics manufacturing
industry alone has grown from $2.7 billion to $17 billion,
and is expected to hit $24 billion by 1970.
Thousands of trained men are urgently needed to help
design, manufacture, inspect, test, install, operate, and
service electronics marvels that are making headlines.
If you qualify, it means a secure, steady high -pay job
with a real future to it.
Maybe you'd like to become a broadcast engineer...
put famous radio disc jockeys and television entertainers
"on the air." Or be your own boss servicing some of the
more than a million two -way mobile radio systems in
taxis, trucks, trains, etc. Or work alongside famous scientists developing and testing such electronics miracles
as picture -frame TV, desk -top computers, pea-sized
hearing aids, rocket guidance and control systems.
Regardless of which you choose, the secret of "getting
your foot in the door" is getting a Government FCC (Federal Communications Commission) License. It's government- certified proof, respected by employers everywhere,
that you have passed a standard Federal exam on the
fundamentals of electronics that you're not just an
electronics handyman, but a real "pro." Many jobs
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.

-

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
and qualify for
learn how you can get your license
top opportunities in Electronics.
With this book, you will receive a second free book,
"How To Succeed In Electronics." It's the catalog of
the Cleveland Institute of Electronics . .. first organization to offer an FCC License Warranty. (CIE will refund all of your tuition if you don't pass the FCC exam
after completing the course
on your first try
designed to prepare you for it.) You will learn why
better than 9 out of 10 men with CIE training get their
FCC Licenses, even though 2 out of 3 without this
training fail.
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
17th Street, Dept. EL-1 , Cleveland, Ohio 44114. Do
it now -it may change your whole life.

...

...

r

1

MAIL COUPON FOR 2 FREE BOOKS

C.' E

Cleveland Institute of Electronics
1776 East 17th Street, Cleveland, Ohio 44114

Please send me, without cost or obligation, your 24 -page book,
"How To Get A Commercial FCC License," together with your
school catalog, "How To Succeed In Electronics," of license -

preparation courses.
Name

(please print)

Address

ENROLL UNDER NEW G.I. BILL
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.
AU CIE

Bill information.

MARCH- APRIL, 1967

State

City
Occupation

Zip
Age

Check here for G.I. Bill information.
Accredited Member National Home Study Council
A Leader in Electronics Training ... Since 1934

E

L-1J

5

SHOPPING MART
GIANT SURPLUS BALLOONS
"Balls of fun" for the kids.
traffic stoppera for stores, ter-

rific for amateur meteorolo-

gists. Create a neighborhood
sensation. Great backyard fun.
Exciting beach attraction. Amateur meteorologists
use to
measure cloud heights, wind
heavy
black rubber.n Inflate with vacuum cleaner or auto air hose;
or locally available helium for
high rise. 8' diem. $2.00 Ppd.
Order Stock No. 60,568EK.
Edmund Scientific Co., Barrington, New Jersey 08007.

I

HI- VOLTAGE ELECTROSTATIC GENERATOR
Van

De Graf low -amp type.
200,000 volt potential, yet
completely safe. Demonstrates
lightning, St. Elnico's fire. repulsion of charges, electrostatic dust Collection, many
other electrical wonders. Motor, 110V, 80- cycle, AC. Humidity range, 0 -90 %. Current,
1.5 to 2.5 microamps. Aluminum base, frame and charge
.
collector. Unbreakable plastic.
Insulating column. Ht. 17 ",
die. Ba /q . Full instructions.
$43.50 Ppd. Order B70,284EK. Edmund
Scientific Co., Barrington,
New Jersey 08007.

EXPERIMENTAL FUN WITH TESLA COIL

Now perform spectacular ex-

8". $44.00
rington,

New

Ppd.

periments without wires
res
as Nicola Tesla did 50 yrs.
trancos itseextremely high Cfrefrequency electromagnetic
(millions
yclesa per
secondi- through space.
Lights
fluorescent tube 2 ft. away,
ionizes gases, performs total
of 21 fascinating experiments.
Incl. Neon Lamp, discharge
electrode, 2 radiation antenna
plates. Generates 5.000 V. for
Meas.
Order Jt70,301EK. 1Edmund OScientfic Co. Bar

Jersey 08007.

DuPONT PLASTIC LIGHT GUIDE KIT

Experiment with amazing new
plastic fiber optic light guides.
1001 uses for mfrs., experimenters, hobbyists. Use for
exciting new projects and
products. Guides transmit
light same as wire conducts
electricity. Use to illuminate
remote areas, multiple locations from single source, confine light to small areas, conduct sensing and control systems. Inc. 2 guides, source,
lens, dyes, connectors.
$10
Ppd. Order jj70,855EK. Edmund Scientific Co., Barrington, New Jersey 08007.

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 system 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 technology necessary for new methods of TV picture display not dependent on the cathode-ray
tube.

NEW MODEL DIGITAL COMPUTER

Solve problems, tell fortunes,
play games with miniature

version

of

brains! Adds, subtracts, multiplies, shifts, complements.
carries, memorizes. Colored
plastic parts easily assembled.

/z" x 43/4 ". Incld.
assembly diagrams, 32 -p. instruction book
covering operation
re language (binary system)
em)
peammins. problems & 15 experiments.
Ppd. Order

step -by -step

1!i

Edmund Scientific

Barrington, N. J.

"FISH" WITH A MAGNET

treasure hunting on the
bottom!
Fascinating fun &
sometimes profitable! Tie a
line to our 5 -lb. Magnet-drop
it overboard in bay, river, lake
or ocean. Troll it along bottom-your "treasure" haul can
he outboard motors, anchors,
other metal valuables. 5 -1b.
Magnet is war surplus -Alnico
V Type- Gov't. cost $50. Line
over 150 lbs. on land -much
greater weights under water.
$12.50 Ppd.
Order
Stock
Edmund ScienJt70,571EK.
Go

w;.+L

tific Co., Barrington,

GIANT FREE CATALOG

N. J.

08007.

Completely new 1987 edition
-148 pages. Bargains galore!
New categories, items, illustration- 1.000's of buys for
industry Optics, Science,
Math, On -the -Job helps, quality control aids. Optics for
research labs, design engineers, experimenters- Instrumenta for checking, measuring
to speed work, improve
quality, cut costs. Hard -to -get
war surplus bargains. Write
for Catalog EK. Edmund Scientific Co., Barrington, New
Jersey 08007.

-

6

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

What You Pay
Color TV...

Regardless
For

A

Of

It Can't Perform
As Well As This
New Heathkit® "180"
For Only $37995*

Here's Why!
Exclusive Features That Can't Be Bought In Ready Made Sets At Any Price! All color TV sets require
periodic convergence and color purity adjustments.
This new Heathkit GR -180 has exclusive built -in
servicing aids so you can perform these adjustments
without any special skills or knowledge.
anytime

...

Simple -to- follow instructions and detailed color
photos in the GR -180 manual show you exactly
what to look for, what to do and how to do it.
Results? Beautifully clean and sharp color pictures
and up to $200 savings in
day in and day out
service calls during the life of your set!
Exclusive Heath Magna -Shield ... surrounds the entire tube to keep out stray magnetic fields and improve color purity. In addition, Automatic Degaussing demagnetizes and "cleans" the picture
everytime you turn the set on from a "cold" start.
Another Exclusive! The
Choice Of Installation
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 critical circuits are preassembled, aligned and tested at
the factory. The GR -180 manual guides you the

...

...

NEW 12" Transistor Portable TV
Unusually sensitive performance. Plays anywhere ... runs on household 117 v. AC, any
12 v. battery, or optional rechargeable battery
pack ($39.95); receives all channels; new integrated sound circuit replaces 39 components;
preassembled, prealigned tuners; high gain IF
strip; Gated AGC for steady, jitter -free pictures; 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.

rest of the way with simple, non -technical instructions and giant pictorials. You can't miss!
like the hi -fi
Plus A Host Of Advanced Features
180 sq. inch rectangular tube with "rare earth phosphors", smaller dot size and 24,000 volt _picture
power for brighter, livelier colors and sharper definiAutomatic Color Control and gated Autotion
matic Gain Control to reduce color fading and insure
. deluxe VHF
jitter-free pictures at all times
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
300 ohm balanced and a 75 ohm coax
Inputs
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 quantities.
*Kit GR -180, everything except cabinet,
$379.95
102 lbs.
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...
$75.00
Available February

...

...

...

-a

- First Kit With Integrated Circuit
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

o
Kit TG -46

$21995
(save

Kit

0

TG -26

Kit

$0095

$11111.55)

(save $47)

o
Kit TA -16

TG -36

(save S40.55)

$12995

D NEW Heathkit Transistor Guitar Amplifier
60 watts peak power; two channels
one for accompaniment, 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 reduction; 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.

- -

reinforcing rod; 3 pickups with individually adjustable pole-pieces under each string for emphasis and
balance; 3 silent switches select 7 pickup combinations; 6 controls for pickup tone and volume; professional Bigsby vibrato tail -piece; curly maple
2" rim
shaded cherry red. 17 lbs.
arched body

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.

...

...

3 Pickups
Hollow Body
0 Deluxe Guitar
Double- cutaway for easy fingering of 16 frets;
ultra -slim fingerboard
2434" scale; ultra -slim
"uniform feel" neck with adjustable Torque -Lok

-

-

...

2 Pickups
D Silhouette Solid-Body Guitar
Modified double cutaway leaves 15 frets clear of
24'/4" scale; ultra body; ultra -slim fingerboard
slim neck for "uniform feel "; Torque -Lok adjustable
reinforcing rod; 2 pickups with individually adjustable pole -pieces under each string; 4 controls for
tone and volume; Harmony type `W' vibrato tailpiece; hardwood solid body, 1'/2" rim, shaded
cherry red. 13 lbs.

...

...

2 Pickups
Hollow Body
0 "Rocket" Guitar
Single cutaway style; ultra -slim fingerboard; ultra slim neck, steel rod reinforced; 2 pickups with individually 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

Kit GR -36

$6995

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;
two 5'/4" PM speakers; clutched volume control for individual channel adjustment; compact 19" W x 61/2" D x 91/4" H size; preassembled, 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 operation; die -cast top -plate, flywheel and capstan
shaft housing; all push- button controls; automatic 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

Kit SB -101

$36000
(less speaker)

1

...

NEW Portable Phonograph Kit

2 -Watt Walkie -Talkie
Assembled
GRS-65A

Kit GD -16

$9995

$3995

...

Factory AssemNew
bled. Up to 6 mile range;
rechargeable battery; 9 sili-

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

con transistors, 2 diodes;
superhet receiver; squelch;
ANL; aluminum case. 3
lbs. 117 v. AC battery
charger & cigarette lighter
charging cord $9.95. Crystals $1.99 ea.

HEATHKIT

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 kHz dial calibrations. 23 lbs. SBA -301 -2,
400 Hz CW filter ... $20.95. Kit HP -13, mobile
$59.95. Kit HP-23, fixed
power supply
$39.95
station supply

1967

FREE

& beige preassembled cabinet; 117 v. AC. 23 lbs.

r HEATH

Enclosed is $

World's Largest
Electronic Kit

shortwave, test, educational, home and hobby
items. Mail coupon for
your free copy.

MARCH -APRIL, 1967

plus shipping.

Please send FREE 1967 Heathkit Catalog.

and over 250

easy -to -build Heathkits
for color TV, stereo/
hi -fi, CB, ham, marine,

,

Please send model (s)

Catalog!
108 pages ... many in
full color ... describe

these

COMPANY, Dept. 139.3

Benton Harbor, Michigan 49022

Name
Address

City

L

State
Prices & specifications subject to change without notice.

Zip
CL -269

9

NEWSCAN
tensity modulation; a second diffraction cell
that acts as a horizontal deflector which provides a high degree of resolution; and a ver-

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 performance. Every time. All the time.
Made by the world's largest manufacturer of
speakers, this premium audio equipment is available at popular prices.
And you can select from many fine models -from
the unique, handsome metal-grilled CS-24 Auxiliary Wall Speaker to the efficient, compact CS -20,
CS-52 and the Ultimate 5- speaker CS-61 Bookshelf System. All carried only by franchised
dealers.
A word from you and we'll send literature and
the name of your nearest dealer.

...

tical deflector. They perform essentially the
same functions as parts of a conventional picture 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 brightness. 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 deflection and vertical deflection stages of the system.

Honest Weight
A new portable electronic platform scale developed 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) CS -62 Bookshelf 3-way speaker system (3 speakers).
Oiled walnut enclosure. Meas. 254
15% x 111 6 ,,
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
system.

"x

enclosure. Meas.

'"

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

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 transmitted through Revere electronic load cells in
(Continued on page 12)
10

ELEMENTARY ELECTRONICS

knightkif

Build this famous

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
a few fun -filled evenings you can
electronics
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 zero -in on Coast Guard LORAN signals
casts
exact time from station W W V in
. get the
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.

-in

...

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, nontechnical instructions and extra -large illustrations
that show where every part fits ... and almost
_

_

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- 1
i.. turn your money, less transportation 1
04 charges, under the Allied guarantee of
satisfaction.
ALLIED RADIO
'.4
,
IIAlif iVilliPn+lrrliiIMll
r -,rnt%rIfnr-n
,

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 Automatic Volume Control to prevent fading and blasting, illuminated "5" meter for fine tuning, and
many other features found only in shortwave receivers 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 assembly instructions for only

..

Read the unique money-back guarantee
then rush coupon
exclusive in the industry
for full details and Special Introductory Offer.

...

r

ALLIED RADIO, Knight -Kit., Dept.
P.O. Box 4398, Chicago, III. 60680

S

1

CC

Please rush full details and Special Introductory Offer
on the Knight -Kit Star Roamer 5 -Band Short-

wave Receiver.

r

,

u

MARCH -APRII., 1967

i

ï

Name
PLEASE PRINT

Address

City

State

lip

11

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

tom"

Fill in coupon for a FREE One Year Subscription 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 Values. Credit plan available.

The world, truly, is getting smaller. Machined 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 microscope are dozens of different parts machined of

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

tell how small small is by comparing
machined parts to centimeter scale on
microscope stage platform.
You can

stainless steel for the computer, electronics,
telephone, missile and communications industries. 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 Chicago 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"

All

99.3076WX*

CB Cha nnels

Crystal Controlled
Plus 2 Reserve Channels
Push -to -Talk Dynamic Microphone
Variable Squelch plus Series Gate Automatic
Noise Limiting

19 Transistors, 7 Diodes, Thermistor
Dual Conversion Receiver for Extra Selectivity
and Sensitivity

Public Address System (with external speaker)
12 -Volt DC Operation (pos. or neg. ground) 6Volt DC (with optional DC Power Supply)
Pi- Network for Optimum RF Output
117 Volt AC Operation with Optional Power
Supply
`Imported

Full 5-Watt Input
Range BoostTM Circuitry for Added Power
3- Position Delta Tune -Provides Accurate Fine

Tuning
Mechanical 455KC Filter for Superior
Selectivity

1967 CATALOG NO 670

FREE

Featuring Everything in Electronics for
HOME

Over 500 Pages

from the

INDUSTRY

LABORATORY

"World's HiFi & Electronics Center"

LAFAYETTE Radio ELECTRONICS
Dept. DEEC -1 P.O. Box 10
Syosset, L. I., N. Y. 11791
()EEC-]

I

Send me the FREE 1967 LAFAYETTE Catalog 670

I
I

Name

I

Address

I

MARCH-APRIL, 1967

City

State

Zip

1967

1001 BARGAINS IN

SPEAKERS -PARTS- TUBES

-HIGH

TAPE RECORDERS
I

I
I

-

FIDELITY

COMPONENTS -RECORD CHANGERS

r- McGEE

NEWSCAN

E' S
CATALOG
Mc G E

NOWRI FOR

-KITS-

EVERYTHING IN ELECTRONICS

RADIO CO..
1907 McGee St.
Kansas City 8, Missouri
SEND 1967 McGEE CATALOG
NAME

ADDRESS

p_CITY

ZONE.... STATE

J

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

ALL TV- RADIO
RECEIVING TUBES
ALL

BRAND-NEW,

$1
ra

First Quality. All

Types Available.
Orders Shipped First
Class Same Day Rec'd.
Unconditionally

Guaranteed.

24 Month Warranty.
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.
Send $1

UNIVERSAL TUBE CO.

et%

Ozone Park, N. V. 11417

Learn how to become

GAME WARDEN

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 participated 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.
a

GOV'T HUNTER, FORESTER, WILDLIFE MANAGER

Exciting job openings now for qualified men who love
outdoor work. Protect forests and wildlife- arrest violators! 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

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,

ALL BAND BATTERY SHORT WAVE RADIO KIT .12.95
Listen around the world-Thousands of miles
away! Ships -Aircraft -Voice of America
sia- London-Australla- Amateurs-Police.-RusAlso
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
for PP del In USA. Basic Kit as
$3 00
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.

f

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.

14

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 "flashing" or rough edges from threads in electrical
connector parts for space and defense applications. The connectors are tumbled in huge barrels 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
ELEMENTARY ELECTRONICS

Reg. U. S.

RADIO
BUILD 20
HOME

Pat. Off.

only

CIRCUITS AT
with the New Improved

95

PROGRESSIVE RADIO "EDU -KIT"®
A Practical Home Radio Course

*
*
*
*
*

Now Includes
12 RECEIVERS
3 TRANSMITTERS
SQ. WAVE GENERATOR
SIGNAL TRACER

**

*
*
* AMPLIFIER
INJECTOR
** SIGNAL
CODE OSCILLATOR

No Knowledge of Radio Necessary
No Additional Parts or Tools Needed

EXCELLENT BACKGROUND FOR TV

Training Electronics Technicians Since 1946

SCHOOL INQUIRIES INVITED

FREE EXTRAS

Sold In 79 Countries

SET

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VALUABLE DISCOUNT CARD

HOME RADIO COURSE at a
"Edil -Kit" offers you an outstanding PRACTICAL
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rock - bottom price. Our Kit is designed to train Radio
You will learn radio theory, Construc-

The

home training.

Of
use Of the most modern methods
THIS IS A COMPLETE RADIO COURSE IN EVERY DETAIL.
tion practice and servicing.
regular schematics; how to wire and solden
You will learn how to build radios, using
radios- You will work with the standard type of
In a professional manner; how to service
development of Printed Circuit chassis.
punched metal chassis as well as the latest
will construct, study and work with
You will learn the basic principles of radio. You
r ctifiers, test equipment. You will learn
RF and AF amplifiers and oscillators, detectors,
and practice
Progressive Code Oscillator. You will learn Injector,
and practice code, using theProgressive
Pro Signal Tracer, Progressive Signal
trouble -shooting, using theElectronics Tester,
Square Wave Generator and the accompanygressive Dynamic Radio &
ing Instructional material.
Radio
s
of
F.C.C.
and General
You will receive training for the Novice, Technician
Code
Transmitter, Square Wave Generator,
Amateur Licenses. You will build Receiver,circuits,
and learn how to operate them. You
Oscillator, Signal Tracer and Signal Injector
Electronics.
for television, Hi-Fi isandrequired.
will receive an excellent background
is
-Kit"
The "Edu
or science
Absolutely no prevìou knowledge of radio
nd engineering experience. The 'Edu -Kit" will
product of many years of teaching Electronics
and Radio worth many times the low
basic education in
provide you with
e
rice of the kit.
moree than the
Tracer alone is worth m
The
price

CERTIFICATE OF MERIT
TESTER INSTRUCTION MANUAL
QUIZZES
HIGH FIDELITY GUIDE
RADIO
TELEVISION BOOK
TROUBLE -SHOOTING BOOK
MEMBERSHIP IN RADIO.TV CLUB:
FCC
CONSULTATION SERVICE
AMATEUR LICENSE TRAINING
. PRINTED CIRCUITRY

I

tries of
step by tep, so that
carefully designed, mistake.
The Edu-Kit"
you cannot make a
allows you to teach yourself at your own
is
necessary.
NO
instructor
rate.

Investment.

the

any0uthousandsw

ofh Individuals of all

PROGRESSIVE TEACHING METHOD

world.
Is the foremost educational radio kit in the
The Progressive Radio "EduKit"
electronics training. The "Edu as the standard in the field ofDoing
and is universally accepted
Therefore you construct,
-"
of "Learn by
the modern educational principle
proKit" uses
Integrated
a
closely
In
shooting
practice trouble
learn schematics, study theory,
thorough and Interesting background in radio.
the
gram designed to provide antheasilYlearned,
Edu-Kit." You then learn first
the
various radio parts of build
You begin by examining
this
radioWith
simple
a
Then you
iring of these parts.
function. theory andlistening
learn theory. practice testing
to regular broadcast stations,
goy
theory
set You will
advanced
more
learn
radio,
build a more advanced
will
and trouble-shooting. Then you
in a progressive manner. and at your own rate. you
and techniques. Gradually,
more advanced multi -tube radio circuits. and doing work like a
find yourself constructing
Signal
Oscillator,
Professional Radio Technician.
Code
Transmitter,
Included in the 'Edu -Kit" course are Receiver,
These are not unprofessional
l
Tracer. Square Wave Generator and Signal Injector Circuits.
of pro^e
by

wiring
-all

but genuine rags circuits, constructed
"breadboard" experiments,metal
construction siown
of
the rats,
chassis. p
and soldering on
house current.
on our re ,ular AC or
as "Printed Circuitry." These circuits operate

THE "EDU -KIT" IS COMPLETE

and
necessary to build twenty different radio variYou will receive all parts and instructions
Our Kits contain tubes, tube sockets.
aranteed to operate.
electronics circuits, each ceramic
tie strips,
and paper dielectric condensers, resistors,wire,
able, electrolytic, mica,
solder,
-up
hook
Manuals,
Instruction
chassis,
metal
hardware, tubing, punched
volume controls and switches, etc.
selenium ectifiers, coils,
materials, including Printed Circuit chassis,a
In addirtion, you receive Printed Circuit
set of tools,
instructions. You also receive a useful and
special tube sockets, hardware and
Electronics
and a self -powered Dynamic Radio
professional electric soldering iron, Code
Oscillator,
Instructions and the Progressive Code lessons
Tester. The "Edu -Kit" also includes License
for
training. You will also receive
in addition to F.C.C. Radio Amateur Tracer and the Progressive Signal Injector, a High
with the Progressive Signal
Membership in Radio -TV Club, Free ConsultaGuide and a Quiz Book. You r a eeive
and Discount Privileges. You receive all parts, tools,
tion Service, Certificate f Merit
instructions, etc. Everything is yours to keep.
servicing

r----UNCONDITIONAL

PRINTED CIRCUITRY

Ì

no increase in price, the "Edu -Kit"
includes Printed Circuitry. You build
Printed Circuit Signal Injector, a unique
servicing instrument that can detect many
Radio and TV troubles. This revolutionary

At

now
a

technique of radio construction is now
popular in commercial radio and
TV sets.
A Printed Circuit is a special insulated
new

becoming

chassis on which has been deposited

ducting material

a

con-

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 interested in Electronics.

MARCH -APRIL, 1967

I

trouble- shooting nd
manner. You
at
s on e the sets
will prac tice s repairs
symptoms
construct. You will learn
portable
and causes of trouble in home,
how to
and car radios. You will learn
Signal Tracer, the
use the
professional
unique Signal
TesterL h Welle you
Electroniics
&
way, you
are learning in this practical
many a repair lob for
will be able to do neighbors.
char
your friends andfar eighbo d the d price
will
feess
the
with any technical
ou
' help you
lems you may have.

will

t

learn

ggrr

THE KIT FOR EVERYONE
ages and backgrounds have successfully
background
You do not need the slightest
more than 79 coon.
used the "EduKit'' in "Edu
radio or science. Whether you are Inter-Kit" has been
the world. The

In
because you
ested in Radio & Electronics
hobby. a well aying
want an interesting
business or a job with a future, you will find

SERVICING LESSONS
You

i

you .pay.

OF TOOLS

FROM OUR MAIL BAG
Pl., WaterJ. Stataitis, of 25 Poplar
have repaired
I
writes:
bury. Conn., for
friends, and made
several sets
fora
' pai
as ready to spend $240 for a Course.
but I found your ad and sent for your
Kit."
Ben Valerio. P. 0. Box 21. Magna,
Here
are
Utah:
uesti
am sending POU the questions
have been In
answers for them. I years,
but like
Radio for the last seven
to
Radio Kits. and like ento wOrk withTesting
build Radiyyo minute Equipment.
worked with
joyed every
works
the a Signal
fine. Also like to let you know that I

o.

1

feel proud of becoming a member of your
Radio -TV Club."
Robert L. Shutt. 1534 Monroe Ave..
Huntintona few lines "Thought
to say that I re.
u
dreg

and as
celved
had y at (such
by adba gain can
rea low price. I have already started MY
phonographs.
pairing radios andsurprised
to see me
friends were really of It so quickly.
The
get Into the swing
Trouble-shooting Tester that comes with
the
the Kit Is really swell. toandbe finds
found."
trouble. If there Is any

MONEY-BACK GUARANTEE

Please rush my Progressive Radio "Edu -Kit" to me, as Indicated below:
Check one box to indicate choice of model

Regular model $26.95.

Deluxe model $31.95 (same as regular model, except with superior parts and
tools plus Radio & TV Parts Jackpot worth $15.)
Check one box to indicate manner of payment
I
enclose full payment. Ship "Edu -Kit" post paid.
Ship "Edu -Kit" C.D.D. I will pay postage.
Send me FREE additional information describing "Edu -Kit."
Name

Address

PROGRESSIVE "EDU - KITS" INC.
1186 Broadway, Dept. 517DJ, Hewlett, N. Y. 11557
15

Tips from a
Technician's
Notebook

Shortcuts -developed, and used,
by our readers
make your
servicing and troubleshooting
easier and more professional.

-to

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 desirable. Fasten a miniature lamp socket to one
side of a spring -type clothespin. To the other
side of the clothespin attach the magnet element 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 battery or 6.3 -volt AC filament transformer.
The magnet will cling to iron tools for extra
reach.
1111111111111111111111I11111111111111111111111111111111111111111111111111111111111111111111111111111111111111ÌI

EMERGENCY COUPLER
HAS ZERO BACKLASH
A one -inch length of automobile windshield wiper hose can be used as a quick, inexpensive 1/4 "- to -1/4" shat coupler for radio
and other electronic gadgets. While not intended to replace conventional couplers
which employ set screws, the hose does grip
the shafts with surprising tenacity, making
it handy in an emergency or in experimental

breadboards. A 3- to 4 -inch length of hose
makes a good flexible coupler for connecting the shaft of a variable component to a
knob shaft when the two shafts are out of
line up to 45 degrees from each other -backlash is practically nil.
Other uses for the hose include couplers
for small electric motors, Veeder -Root counters -in fact, anywhere 1/4 -inch shafts are
used, and the load requirements are moderate.
!1! 1111111! 11111111111 !IIIIIIIi11111111I11111!IIIII

DISCARDED PORTABLE BECOMES TEST SPEAKER
OUTPUT

OUTPUT

TRANS. JACK

TRANS.

VOICE COIL
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 trans16

former. Now scrounge up open- circuit and
closed circuit phone jacks (see schematic diagram), 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.
ELEMENTARY ELECTRONICS

NEWSCAN

look

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

10

Icelile for
me best in
p1Ì¢15 & SÑps, 100
LONG NOSE AND

DIAGONAL PLIERS

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.

VIVZ,.:

filled with gas and lighted by passing an electrical 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, Maryland. Come on down next vacation time.

TV

PLIERS

COMBINATION

SIIP JOINT PLIERS

SIDE CUTTING PLIERS

TRANSVERSE
CUTTING PLIERS

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

RADIO AND

UTILITY PLIERS

Same professional quality as famous Xcelite screw
drivers and nutdrivers. Forged alloy steel construction. 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).

s

--1

r-Sea -going switchboard contacts the world

by telephone.

radio room. Installer Arne Brenden, of the
Norwegian subsidiary of ITT, installs the modern "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.
MARCH -APRIL, 1967

80 BANK ST., ORCHARD PARK, N. Y.
Send Catalog Sheet N664 on pliers and snips.

XCELITE INC.
name
address

city

state

&

zone

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 questions in the available space in upcoming
issues of
Elementary Electronics. Sorry, Leo will
be unable
to answer your questions by mail.

Why is a dry cell tested for life in volts instead 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 operating load when measuring voltage.

115v

+ VOLTMETER

LOAD

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 different. Magnetic speakers weren't much more
than glorified earphones
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
low- impedance coil moving in a
field generated by an electromagnet. Electrodynamic 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 universal output transformer. Connect the primary
to the speaker terminals and the speaker across
the transformer secondary taps that give maximum 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 connected 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
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 capacitors too-ones with 40 to 60 mf rating for better
DC filtering since the hum -buck circuitry will
not be in the PM circuitry.)

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?
-R. J., Palos Park, Illinois
Don't have a schematic available. But, you ,® PRI
probably can get one from the manufacturer iwrJ
whose address is listed as 1205 West Roscoe MAGNETIC
SPEAKER
Street in Chicago.
TERMINALS
18

-a

-a

Can't Have One

1

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.

-if

OUTPUT
TRANSFORMER

PM
SPEAKER

ELEMENTARY ELECTRONICS

Mike Low -Down

it's FUN it's NEW
it's EDUCATIONAL

several
have a low -impedance mike and

1

like to
high- impedance amplifiers and 1 would
without reconnect the mike to the amplifiers
wiring them. How can 1 do it?
-D. B., Eldorado, Texas
the
Use a matching transformer as shown in
diagram and adjust the primary transformer
taps to match your mike.

DO -,T- YOURSELF

ELECTRONICS

KIT

SHIELDED

SHIELDED
CABLE

CABLE
MICROPHONE
PLUG

Build your own
AM radio, voice
operated lamp,
rain detector,
fire alarm.

LOW-IMPEDANCE
MICROPHONE

Now Only

LOW-IMPEDANCE MICROPHONE
TO - GRID TRANSFORMER

-

Work with capacitors, resistor, inductors. BUILD YOUR OWN POWER
TRANSISTOR and the circuits to test
it Learn electronic symbols. how to
simply exread schematics
plained in the easy-to- follow instruction manual. All parts included.

$159s

..

400 Hz Supply

Fill out coupon
below and mail to:

would like to get a power supply delivering
400 -cycle AC for a radar set. Can you
-volt,
115
one?
tell me where 1 can buy one or how to build
-R. B., Swedesboro, New Jersey
1

Bogue Electric, 100 California Avenue, Patersupson, New Jersey, makes 400-cycle power
plies, but they aren't cheap. Don't forget that
you
you can't operate a radar lawfully unless
it.
cover
to
license
have a station

Color -TV Service Info

What is the correct procedure for adjusting
the color in my Zenith TV set? It has gain controls for red, blue and green but I am at a loss
to know what to do with them.
P. P., East Tawas, Michigan
Get a Sams Photofacts kit for your set at a

Tempe,Ariz.
P.O. Box 417
Idea Corporation of America
IPlease rush deli very of the Do -it- yourself Electronics
Kit to:
NAME

I ADDRESS
CITY

I

I

am enclosing

Kit postpaid

or

STATE
Send Electronics
have enclosed $2.00 extra for my C.O.D.

full payment of $15.95.
I

J

NOW... BUILD YOUR
OWN CCTV CAMERA

-N.

radio parts distributor. It should contain the
information you need. Don't overlook the service manual published by the manufacturer -send
model and serial number for exact information.

Off Calibration
1 have a communications receiver which contains a 100 -kc crystal calibrator. The dial markings 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?
W. G., Oakville, Ontario
First, check the dial calibration-tune in

-J.

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
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

-if

MARCH- APRIL, 1967

NEW
IMPROVED MODEL
Vidicon
25mm. f1.9 Lens
Cable

Instructions

$20 DOWN
$10 MONTH
ASSEMBLED $259.50
The affordable answer to an easy -to -use, top performing surveillance camera. Hundreds of uses in home,
store, plant, office, hospital, school. Connects instantly to any TV set. Gives excellent picture with
light under normal room lighting. Operates up to six
nothing else to buy. Optional lenses
sets. Complete
and tripod available.
All parts guaranteed one year. Vidicon guaranteed 90
days. Make check or money order to CONAR. Shipped

-

REA

collect.

SEND FOR FREE CONAR CATALOG
of National Radio Institute, Dept. CVIC
3939 Wisconsin Ave., Washington, D.C. 20016

CONARDivision

19

ASK ME ANOTHER

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
needed. Once the dial is calibrated properly adjacent -channel TV station you can make a
tune to WWV on 2.5, 5, 10 or 15 MHz (mc) simple wave trap with a small capacitor and a
and adjust to 100 -kHz (kc) crystal calibrator short length of twin lead. If a small -value fixed
capacitor is used the twin lead will have to be
to zero -beat with the WWV carrier.
adjusted in length for maximum effect. If a compression -type trimmer is used it is adjusted for
Adding Bandspread
maximum effect.
I have an ancient Emerson Model 524 reThe twin -lead trap is just taped loosely
ceiver and 1 would like to know if I can band - lead -in-there is no direct connection. to the
Certain
spread the ham bands over a longer portion of spots on the lead -in will give more
effect than
the shortwave bands. I am planning to use it others.
as a novice receiver and would like, if possible
CONDUCTORS TWISTED
to spread the 40 and 80 meter bands.
2.7 TO 30MMF
TRIMMER
-N. G., Flemingsburg, Kentucky AND SOLDERED TWIN LEAD?
Add an auxilliary local- oscillator- tuning capacitor as shown in the diagram. Mount it close
4 "T08.
to the present tuning capacitor gang -use a shaft
RAZOR BLADE
extender, if necessary, to couple the bandspread
SHORTING BAR
capacitor to its own tuning dial. Maximum capacitance of the bandspread capacitor probably
IOMMF
won't be as high as 50 uuf and may be as low
MICA
CAPACITOR
as 25 uuf if you want to keep the oscillator
within the bandpass of the RF circuits. The
12°
TWIN LEAD
relatively -broad tuning of the IF amplifier may
not give you the selectivity you will probably
ANTENNA
need for clear reception.
TWIN

LEAD

TAPE

ADDED

BANDSPREAD-

POSITION TRAP

TUNING
CAPACITOR
50MMF MAX.

TUNING
CAPACITOR

4

ON LEAD -IN FOR

MAXIMUM EFFECT

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.
AUDIO

POWER

A

000

40

40-100 Hz

00

O (J

VARIABLE
AUDIO

FREQUENCY
OSCILLATOR

LINE
SIDE

TO 100 WATTS

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 station in our local area broadcasting on TV Channel 6 so I can pick up a station 162 miles away.
If so, how?
-D. W., Jamestown, N. Y.
20

A Little Light
I have an old Powell repeater flash and a rechargeable 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 "information" systems. What are they and where can
I get basic information?
-D. R., Hollywood, California
That's just another definition of computer systems and EDP (electronic data processing). Get
a copy of the September 1966 issue of Scientific
ELEMENTARY ELECTRONIça

i

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.

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
the green one to the output transformer and
yellow lead to pin 8 of a 35Z5.
-A. E. F., Phoenix, Arizona
Connect a PM speaker as shown in the diagram, adding a filter choke to take the place of
the field coil.

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 converter 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
include 25Ç for postissue if you don't have
age and handling.

it-

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

Your Own Business Now Provides
For Their Future
What better

he

conduct

investment

pagee ofINCOME OPPORTUNITIES.
the Mar/Apr issue
Whether you're interested in full or part -time,
provides "55 Businesses for Under $500" .. tells
how they work and reveals their pros and cons.
Read INCOME OPPORTUNITIES for up- to -theminute details on franchises with investments
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EE -367
INCOME OPPORTUNITIES
10022
N.Y.
York,
New
Avenue,
505 Park
Begin my subscription to INCOME OPPOREnclosed is
TUNITIES with the next issue.
(cash money-order). Bill
(Foreign: dd 75c a
me.o(Fo

Name

please print

Address
City

State

Zip

MARCH-APRIL, 1967

21

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 terminals, 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.

Now, better than ever, the
new and improved S &M

supersensitive photo meter
Here is a precision instrument that meets
the highest standards of any meter available.
It offers consistently accurate readings at
very low light levels, which, if required, can
be converted to ft.-candles from a graph sup plied. Researchers, scientists, educators and
hobbyists have confirmed that this meter can
read light levels as low as 0.000245 ft.candles.
The S &M Supersensitive Photo Meter uses
the newest Clairex Corp. CL-505L Cadmium
Sulfide Light Cell to measure light levels
from twilight to bright sunlight at ASA
speeds of 3 to 25,000. A new %" high easel
type probe and also a miniature probe are
now available as accessories. The Computer
gives F stops from .7 to 90; lists exposure
time from 1/15,000 sec. to 8 hrs.; 4 range
selection; EV- EVS -LV settings; weighs only
10 ounces.
Used extensively in Photo Labs, Physics and
Research Labs, Hospitals, High Schools, Universities and numerous industries. Also used
with movie or still cameras, microscopes and
telescopes and IS A MUST FOR PHOTOMICROGRAPHY,

r

Phones Replace Old Speaker
My old radio has four speaker wires. How
can I disconnect the speaker and permanently
install headphones?
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 headphones, 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 8ohm 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.

-l.

///

SHORT WIRES
TOGETHER

HIGH-

IMPEDANCE
HEADPHONES

10n
RESISTOR
SPEAKER

FIELD- COIL
LEADS

PUSH PULL
AMPLIFIER

-KIT

SCIENCE & MECHANICS

DIVISION EE -887
505 Park Avenue/New York, N.Y.
10022
Enclosed is $
Please send me the new
S &M Supersensitive Photo Meter. I understand
that if I am not completely satisfied, I may return
the meter within 10 days for a complete refund.

-In

No. 10I
kit form
$29.95 with carrying case

No. 105

$2.00 carrying case only
Additional Computer

No. 102 -fully assembled

$34.95 with

carrying case
Easel Probe $6.50

$1.00
% inch Probe 56.50

Add 105, for Canadian and foreign order. New York City residents add 5% for N.Y.C. sales tax.

Name
(PLEASE PRINT)

Address
City
22

State

Zip Code

C T.

HIGH - IMPEDANCE

PHONES

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

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.
a

Add An

S -Meter

How can 1 hook up an "S" meter to my shortwave 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 amplifier as shown in heavy lines in the diagram.
Replace the AF power amplifier cathode resistor with a 2 -watt potentiometer (Rl) having
approximately the same resistance as the original 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

Color TV `Acting -up "?
Learn How To Adjust Your
New Color TV Set!

Save money too!
Avoid the expense of calling a repairman
each time your TV set "acts -up ". In easyto- understand language, complete with illustrations, learn just how to adjust your
color TV; the right way to replace any
picture tube; how to fix your own tape
recorder, kiddie phono, fm tune, stereo
system and ac /dc radio. These and many
more dollar -saving tips in the new edition
of TV REPAIR.

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 numbers 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-

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TV REPAIR
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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.
MARCH- APRIL, 1967

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23

activity. This work was done in close collaboration with W. Müller. Together the scientists
succeeded in making a gas -filled tube with cylindrical 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 numerous important uses. Linked with other components it proved capable of measuring radiation intensity with great accuracy.
Though Müller spent years on the project
and made vital contributions to it, the combination 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 Müller's role and speak of the Geiger counter.

ELEMENTARY
EI,ECTRONICS

ETYMOLOGY

©O ®O

By Webb Garrison
t7

©O

G

Magnet

A Magnesia ad Maeandrum-or Magnesia on

Battery

the Maeander-was built near the mouth of
a
A In the language of medieval France battre
famous river in Asia Minor. Until its destrucwas used as a verb of action to name the proction by the Cimmerians about 700 B.C. the city
ess of beating repeatedly with hard blows. Milwas an important center of commerce and art.
itary leaders were positively ecstatic when the
But it was best known as the source of a
development of cannon gave them a new and
queer type of heavy mineral that ancients found
powerful means of beating down the walls of
to be endowed with special power. Known to
an enemy city or fortress. So from the old
the Greeks as Magnetis, from the city of its
term for such action they called an artillery
origin, the potent stuff could draw iron to itself.
unit a batterie.
There was no practical use for it until, cenMany a batterie played a decisive role in
turies later, someone discovered that the nature
battle.
of a- needle was changed when it was rubbed guns, Since such a unit included from 2 to 6
fired in sequence, its name attached to
with stone from Magnesia. Arranged so that
various kinds of coordinated groups of things
it could swing freely, such a needle always
and persons. Among these was a favorite toy
pointed to the north.
of early electrical experimenters: panes of sash
Makers and users of the compass found that
glass armed with thin lead plates and arranged
magnete, as they called the power -conferring
in precise order. Properly wired and activated
mineral, occurred not only in Turkey but also
by acid, such a device would yield a steady flow
in many other regions. It was long taken for
of electricity.
granted by seamen that a huge mass of the stuff
He probably borrowed the name from other
formed an "Ilande of Magnete" located under
who used it earlier, but Benjamin
or near the north pole and responsible for the amateurs
Franklin was one of the first to write about
tug on a compass needle. In one of his bursts
work with an electric battery. His crude one
of fancy Milton wrote of an imaginary white
actually preserved the pattern of ordered secity surmounted by a castle built of magnet.
quence that marked an artillery unit. But many
Natural magnets varied greatly in power and
of today's batteries have little if anything in
quality, so had few applications other than in
common
with a row of cannon trained on a
making crude navigational instruments. But
target and set to fire in order.
with the development of the electromagnet science 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.
JEW
11111.1,111

A After

Geiger Counter

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. Rutherford developed the theory of the atom and won
a Nobel prize; Geiger concentrated on perfecting a radiation counter.
By 1908 he was successful with alpha particles. He then turned to study of beta -ray
24

11

o

tii3>
-_
:

111111111111111111,:

ELEMENTARY ELECTRONICS

E\ PASSANT

BY

How Bad Is

JOHN W. COLLINS

Highway

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-

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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(Outside U.S.A. & Canada add $1.50 for

Name
White
1. K-N2
2. K-B3
3. Q-KN6

MARCH -APRIL, 1967

K-Q4
K-K4
K-B5

EE -367

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EXPERI-

Payment
Bill me.

postage.)

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Address
4. K-04
5. Q-N5
6. Q-N4

K-B6
K-B7
K-K8

City

Zip
State
Please include your ZIP CODE

J
25

EN PASSANT
7. K -K3
8. 0-N7

Position after 20

.

.

B -N7!

.

1 I

/'

K-B8
K-K8

9. 0-N1 Mate

Usually it is accomplished in fewer moves.
White's only problem is to avoid stalemates
(draws).

í
,VA

/%,

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

I
"'.

/ g

Why did White resign? Because he cannot
defend against Black's mating attack, combination 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 elbow, 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
for no other reason than to let the
reader see he can play as well as edit.
Problem. The problem this month is an original one, never published before. It is composed
by Master Sidney Bernstein of Brooklyn, N. Y.,

-

White
K-N2
K-B2
R-N5I
K-N3
K-B3
K-Q3
7. K-K3
1.
2.
3.
4.
5.
6.

K-05

8.

K-K5

9.
10.
11.
12.
13.

K-05
K-K5
K-85

K-N5
K-N6!

R-N5#

K-R5
K-R6
K-R7!
K-R8!
K-R7

K-B4
K-B3I
R-N8
K-B2
R-R8 Mate

-if

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 opponent was Frutsaert of Belgium. It occurred in
the 1948 World Correspondence Chess Championship and the opening was a French Defense.
1. P-K4

P-K3

P-04

P-04

N-02

N-0B3

2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.

26

KN-B3

N-B3

P-K5
P-B4

N-02
P-B3

14. R-0B1
NxN
16. RxP?
17. K-B1
18. PxR
19. K-K2

BPxP

KPxP

20. K-01

B-N5
NxP

PxP

N/2-83
B-02
QxB
BxN

0-B3

B-N5#
BxB#
0-0
PxB

115.

Resigns

P-B4!
BxN

Q-KN3!
RxN!

B-R6#
R-K1

#

B-N7!

Problem 5.

By S. N. Bernstein

j

Black

'

i-i

"e

j j j jj
j
j j
} ,,,,. }S
%*..fiii
,,

'.%i1f,"..

White

White to move and mate in two.
Solution in next issue.
ELEMENTARY ELECTRONICS

4

former champion of the Manhattan and
Marshall Chess Clubs. He quips it is his
"sole and immortal masterpiece." It has an astonishing key move and a rich variety of mating
variations.
Solution to Problem 4: 1 Q -08.
More Answers. The Solution to End Game
BPxP
Study #2 is 1 P -N5! Now if 1
2 P -R5! PxRP 3 P -B5, P -R5 4 P -B6 and wins.
If 1
BPxP 2 P -R5! PxBP 3 PxP, P -B6
4 P -N7 and wins. And if 1 P -N5! RPxP 2 P -B5!
PxBP 3 P -R5 and wins. In each case White
queens first and then liquidates all the Black

NEW 1967
ELECTRONICS HOBBYIST
ANNUAL
NOW AT YOUR NEWSSTAND'

....

....

Pawns with the new Queen.
Tips for Readers. A brief explanation of
chess notation and symbols may be in order.
The pieces are denoted by capital letters, thus
K = King, Q = Queen, R = Rook, N = Knight
(more modern and economical than the older
Kt), B = Bishop, and P = Pawn.
And # = check or double check (often given
as ch), ! = good move, ? = weak move, !? _
speculative move and double or triple exclamation and question marks = exceptionally good
or weak moves.
There are several methods of recording
moves, the English Notation, which we use,
and the Algebraic Notation, used in Europe,
being the most prominent. In the English Notation each square on the board has two names,
one used by White and one used by Black,
derived from the original placement of the
pieces. Thus the original square on which the
White King is placed is called KI, the square
immediately in front of it K2, the one in front
of that K3, and so on to K8. Conversely,
White's K8 is Black's K1, the one in front of
that K2 (White's K7) and so on. Reading from
left to right, therefore, the squares on White's
first rank are called QR1 (Queen Rook One),
QN1, QB1, Ql, KI, KB1, KN1 and KR1. 1
P -K4, the first move in my game with Frutsaert,
if written out in full would read Pawn to King
Four and the last move B-N7 would read
Bishop to Knight Seventh. Strange and seemingly difficult at first, one catches on very
quickly to these notations and symbols.
News and Views. Grandmaster Boris Spassky
of the U.S.S.R. scored 111/2-61/2 in taking the
Piatigorsky Cup Tournament in Santa Monica
during July- August. Robert J. Fischer, U.S.
Champion, off to a poor stárt, made a sensational stretch run and barely missed catching
Spassky with 11 -7. Bengt Larsen of Denmark
finished third with 10 -8.
Grandmasters Pal Benko and Robert Byrne
each compiled scores of 11 -2 to emerge as cowinners of the U. S. Open at Seattle in August.
Duncan Suttles of Vancouver was a clear third
with 10 -3.
Grandmaster Larry Evans of New York, reviser of "Modern Chess Openings," 10th Edition, won the Canadian Open at Kingston, Ont.,
August- September, with 9 -1.
MARCH -APRIL, 1967

Hours of
"How To" Enjoyment
for Pro & Novice
For A Limited
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magazine for those whose interest in electronics Is
on the hobby level. THE ELECTRONICS HOBBYIST

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100 -kHZ CALIBRATOR/BUILD THE AERO-BANDER/
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1

EE -367
rTHE ELECTRONICS HOBBYIST
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Enclosed is $1.00. Please send my copy of the 1967
Edition.

Name

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State

yip

J
27

Wide World of

By Jack Schmidt

ELECTRONICS

L

b

4°-4°

1eitym,S

1,1,11

suzisKNYbL ,1

"Where's the burnt tube?"

"Wait till you see the cute
ashtray Harold made from those
small plastic chips!"

". . and have somebody take a
look at my garage door opener!"

don't ask him aboìit his hi -fi!"

"Whatever you do,

oma
oGm

"Did you leave one of your 'bugs'
in the den, Honey?"
28

ELEMENTARY ELECTRONICS

FLIP- FLPS

El'Ib -Ef b2
THE 2- CYLINDER

ENGINES OF
ELECTRONICS
By Len

Buckwalter, KIODH/ KBA4480

Click -click, push-pull go zillions of flipis, if you could
flops every day

-that

hear these silent electronic double-throw
switches. They utter no sound as they tip -toe
through computers, see-saw in sonar, or skim
through counting circuits. They're not only
quiet, but perform the switching job without
moving parts, friction or wear. And they're
fast. That's why in numberless applications,
the flip -flop has given the heave-ho to the
mechanical toggle switch and relay.
The flip -flop is filed under several names
because of the different jobs it does and the
way it does them. Some are called a multivibrator, others relaxation oscillator, or maybe something special like a Schmitt Trigger.
Whatever the name, the flip -flop has these
distinguishing features. First, it's a two -stage
combination of tubes or transistors with a
feedback connection between them. Whenever one stage is on (conducting current) the
other is off. But a stupendous feature of the
flip-flop is that it abhors any in- between condition. Like pushing a flower pot off a window ledge, once the action starts it is
self-completing. Snappy switchover is important -when flipping to flop, in a computer for example, a gradual transition for a
counting operation might print your tax refund check as $10,000 instead of 10 cents.
As we'll see, the circuit's feedback assures
that the on stage always tries to force the
other one off. That's a persistent theme despite numerous variations.
Another peculiarity is that the circuit produces signals which don't resemble the
familiar, flowing sine wave generated by
regular oscillators. The wave form is often
MARCH-APRIL, 1

137

square, clipped or sawtooth in shape. That's
because the circuit switches quickly as stages
are driven between on and off. This is important for generating pulses in radar equipment which needs squared -off signals of fast
rise and decay time. Another quality of the
flip -flop is that it can trigger itself or feed on
external signals. To penetrate the heart of a
flip -flop, we can start with the method for
developing the switching action.
Putting Phase in Reverse. Let's feed a
simple amplifier tube with an input signal
and cause it to conduct current. The input
is shown as a positive -going pulse (1) applied to the tube grid in Fig. 1. As in any
conventional amplifier, a positive -going grid
voltage produces an increase in plate- current
flow through the tube (from cathode to
plate). It also produces another effect: voltage at the plate (2) will drop to a lower
value. Reason for the drop is that more
current flows through the plate -load resistor
and that component drops more B+ supply
voltage than previously. The plate of the tube
receives less supply voltage, since current
flow has increased, and the tube appears (to
the power supply) as a lower value resistance.
COUPLING

CAPACITOR
PLATE

VOLTAGE`

NEGATIVE-GOING
OUTPUT PULSE

DROPS

PLATE LOAD
RESISTOR

POSITIVE GOING PULSE CATHODE
TO GRID

Zr

B+

Basic triode amplifier

shows effects of a
Fig. 1.
square -wave signal passing through the circuit. The
numbers relate to specific actions covered in text.

L;i

1@i®

FLIP -FLOPS

For example, if plate voltage is originally 250
volts B -plus, a positive -going signal on the
grid might drop it to 150 volts -the remaining 100 volts appearing as a voltage drop
across the plate -load resistor.
The drop in plate voltage
a less -positive level
applied to the coupling capacitor. The direction of current flow is such that
electrons flow onto the plate of the capacitor
connected to the plate-load and this charge
repels electrons away from the other right hand plate. The net result is a negative-going
signal (3) at the output side of the amplifier.
This action, actually a 180 -degree phase reversal, is crucial to operating the flip -flop
circuit. The tube has caused the input signal
to do an about -face. Consider, next, how the
same phase reversal occurs in a transistor.
With the trend toward solid state, the semiconductor is becoming the standard device in
constructing flip-flop circuits.

-to

-is

0

COLLECTOR
VOLTAGE DROPS

ed/

PNP

COLLECTOR

b

RESISTOR'

t
NEGATIVEGOING PULSE
TO BASE

POSITIVE-GOING
0_ UTPUT PULSE

e

EMITTER

COUPLING
CAPACITOR

Fig. 2. Basic transistor amplifier should be compared
with basic vacuum -tube amplifier (Fig. 1). Both
pnp and npn transistors can be used in this circuit.

In Fig. 2 is a transistor amplifier. Its
phase- reversing action is nearly identical to
that of the tube. Only difference is the polarity of the input signal; to start the stage
conducting, it is a negative -going pulse. (This
is true for a pnp transistor; an npn type
would require a positive-going input pulse
for the same effect.) As the base is driven
VI

pl PLATE
FLOWS
Fig. 3. Two -stage amplifier shows
current flow, coupling -capacitor
discharge path, discharge waveform
and output signal. Numbered points
are covered in text. Circuit action
occurs too rapidly to be shown on
normal measuring instruments but can
easily be seen with a good scope.

30

more negative (1), collector current rises.
Unlike the tube plate in our earlier example,
collector voltage (2) drops to a less negative
(or more positive) value. Applied to the
coupling capacitor, this change appears at
the output as a positive -going signal (3).
Again, the output signal is opposite in polarity when compared to the input, due to a
phase reversal. Now couple two identical
phase-reversing stages together, and you have
the beginning of a basic flip -flop circuit.
Hitching Flip to Flop. We can fire the
opening gun to commence flip-flop action, as
traced in Fig. 3. When the circuit is first
turned on, one tube will always conduct more
than the other even though all circuit values
are the same. It could be due to slight tube
unbalance, a fluctuation in the power supply,
or some other transient disturbance. We'll
assume that tube VI is first to conduct. What
follows is a four-step sequence shown by the
numbers in Fig. 3. Plate current (1) corn mences to flow through tube VI, which lowers Vl plate voltage because of the IR drop
across Rl. This is the phase -reversal effect
described earlier and the resulting signal
rapidly charges the coupling capacitor (2)
with a negative -going signal. We've assigned
this charge a value of -75 volts and it's applied to the grid of the second stage, V2.
High negative voltage at the grid puts V2
into cutoff and V2 plate current flow stops.
If you consider what's happened, you'll note
that as the first tube (V1) went on, it quickly
drives the second stage into cutoff with a
strong negative signal. But the circuit doesn't
remain in this condition very long.
The charged coupling capacitor between
stages sees a path to ground through the grid
resistor. Thus the capacitor begins to discharge current to ground. But that outflow
of current is not sudden since electrons encounter opposition from the grid resistor.
The coupling capacitor (C1) and grid resistor form an RC (time- constant) circuit
that slows the discharge. And it's possible to
select a resistor -capacitor combination to
PLATE

2 CAPACITOR CHARGES

ON

-75V-

CURRENT

-75
i-

V2

DISCHARGE

s

FF

VOLTAGE
HIGH

J

CI

OUTPUT
30 CAPACITOR
DISCHARGES
THROUGH GRID

Rl

R2

RESISTOR

8+

-rks,
GRID

RESISTOR

ELEMENTARY ELECTRONICS

A

control capacitor discharge from seconds to
microseconds.
Next see what occurs at the plate of V2the o$ tube -during the discharge time of the
capacitor. We can see at the output side (4)
that plate voltage has risen to a high positive
value, caused by a negative charge on V2
grid. What's more, the plate will display a
steady high-voltage plateau as the capacitor
discharges. It might seem that V2 plate voltage would slowly rise as the capacitor loses
its negative charge. This doesn't happen,
however-the tube can be completely cut
POSITIVE

4,- FEEDBACK

C2
V1
C

GRID
RESISTOR

Rl.

GRID
RESISTOR

_

-

B+
Fig. 4. Basic flip -flop circuit includes feedback
path-added to two-stage amplifier in Fig. 3. A
capacitive -coupled flip -flop works reliably only at
moderate to high frequencies or repetition rates.
B+

off with a small negative grid voltage (less
than about 10 volts). It takes the capacitor
nearly its full discharge time to go from a

high of -75 volts to below -10 volts. Thus
V2 remains cutoff during most of the discharge time. It results in a squared -off, positive -going output pulse.
From Flop to Flip. Now we can complete
the flip -flop circuit as shown in Fig. 4. What's
been added is a second coupling capacitor,
C2, from the plate of V2 back to the grid of
V1. Purpose of this component is to create
a positive feedback path. As you may recall,
when the plate of V2 was switched off it developed a positive -going voltage pulse. With
the addition of the second coupling capacitor
(C2), the pulse is now applied back to the
grid of VI. The result is to rapidly force V1
to conduct more current. Soon the tube is
fully on (completely saturated) and it can
pass no additional increasing current.
These events reveal how the flip-flop relies
on positive feedback to obtain its important
characteristic: that an on tube produces a
signal which is subsequently returned from
the off stage. Feedback is always in a direction that reinforces the on condition. Up to
this point, the circuit has produced one -half
cycle. Next to be examined is how the tubes
may continuously switch back and forth.
MnaCH-APen., 1967

Recall that in Fig. 3, the coupling capacitor
charged quickly, but discharged at a fairly
slow rate through the grid resistor. When the
discharge time is nearly complete, V2 goes
from the off to an on condition since the
capacitor no longer delivers a negative -going
cut-off voltage to the grid of V2. As V2's
grid voltage approaches zero, current will
commence flowing through V2. At this moment the circuit goes from flop to flip -all
the conditions described earlier are reversed.
The sequence occurs this way as V2 now
goes on and V1 is switched off: rising current
flow through V2 drops that tube's plate voltage; this feeds back a negative -going signal
to the grid of V 1; tube V1 is then cutoff and
remains that way until its grid capacitor
(C2) loses its charge.
From Eccles to Jordan. The flip-flop circuit described so far is termed free running.
It repeatedly see -saws at a frequency which
depends on values selected for the coupling
capacitors and grid resistors. The circuit produces square -wave output since the stages
are either fully on (saturated) or fully off
(grids driven into the cutoff region) And
since the feedback signal is initiated quickly
(during capacitor charge), the instant of
switchover is very fast. And the on or off
periods may be sustained by choosing larger
capacitor and resistor values. These features
make the flip -flop an admirable device for
computer logic circuits since the electronic
components-tubes, resistors, etc. -may
change value through age, but the circuit
continues to generate a distinct binary action. When a serious component defect does
occur, it generally puts the circuit completely
out of action. This is far more reliable than a
circuit which produces some in-between or
analog signal. Another descriptive term for
the free-running flip-flop is the astable multi vibrator. If you want to be historical about
it, call the circuit an Eccles-Jordan multi vibrator. Now to modify it for another important function.
One Shot. The circuit .in Fig. 5 is variously called the one -shot multivibrator, or
the univibrator. It displays the useful characteristic of responding with a single, uniform output pulse when triggered by pulses
of varying lengths from an external source.
This enables it to perform as a counter of
input pulses.
If we examine Fig. 5, it is seen that the
one -shot circuit differs from its free -running
cousin. The principal operating feature is
that one tube-VI always prefers to remain
.

31

GA

FLIP -FLOPS

off, while VI attempts to maintain a con-

ducting, or on, condition. An external pulse
applied to VI, however, instantly switches
that tube on and V2 off. Then the circuit will
automatically reset to its normal condition,
awaiting the next input signal.
Note in Fig. 5 there is no complete, or
closed, feedback loop; that is, no coupling
capacitor returns the signal from V2 back
to V 1. There is another type of coupling between stages. It is the common cathode
connection. If plate current flows in either
tube, a voltage drop appears across cathode
resistor R2. Further, an increase in that voltage drop across R2 always tends to reduce
current flow in both tubes. (This is a standard cathode biasing technique, where an increase in positive voltage at the cathode is
the same as making the tube grid more negative.)

the two stages. But this on and o13 relationship changes when a triggering pulse is applied to the circuit. The pulse, which is
positive going, overcomes the negative bias
on the grid of V1. (Recall that the +3 -volt
cathode has the effect of biasing the grid to

-3 volts). Plate current now flows through
R4 and V1 and plate voltage drops. This
sends a negative -going pulse through coupling capacitor Cl. The negative -going pulse
causes tube V2, normally on, to sharply decrease its current flow and plate voltage increases. It is this plate voltage increase at V2
which produces the signal output of the one shot multivibrator.
As in earlier circuits, pulse length is controlled by discharge time of the coupling
capacitor (CI) through the grid resistor.
That time is uniform, and independent of the
length of the trigger input,
There is still another feature of the circuit
-one that keeps the changeover action brisk.
Without it, the tubes wouldn't switch quickly
enough to form a clean, square -wave output.
It's the common cathode connection for both
stages, which causes the on tube to assist in

TRIGGER

INPUT

V2

PULSE
OUTPUT

Fig. 5. Cathode- coupled one -shot
flip -flop will always return to
its starting condition
is
always driven to cutoff because of the
grid bias across R2 and applied
only to VI through RI. No bias is on
grid of V2 since grid is returned
(through R3) directly to cathode.

-VI

Before the action begins, let's see why VI
normally off, while V2 is on. This can be
traced to the grid connection for each tube.
VI is returned to ground through resistor
Rl and no grid bias develops from this
source. But the tube cathode, operating at
+3 volts does bias the grid. The grid of V1
is now at cutoff value since a +3 -volt
cathode voltage means that the grid is 3
volts negative in relation to the cathode.
Thus V1 doesn't conduct current (through
its plate circuit) at this time. Now to trace
the source of the +3 volts on the cathode.
If tube V2 is examined, it is seen that its
cathode also connects to the common cathode
resistor. The grid of V2, however, doesn't
return directly to ground. It connects directly
to the cathode (through R3) . This eliminates
the effect of cathode bias ( +3 volts) and V2
is permitted to conduct a large amount of
current. This imbalance between tubes represents the normally on and off condition of
is

32

COMMON
CATHODE
CONNECTION

switching the other tube off as quickly as
possible. When plate current of V2 falls,
less current flows through the common
cathode resistor
less positive voltage appears at the top of the R2. Since VI. is also
connected to this point, the grid bias on this
tube (V1 ) becomes less negative. The total
effect of this circuit feature is that the tube
which goes on (VI ) helps turn off the other
tube.
The cycle ends as VI reaches saturation
and can no longer pass a signal through the
coupling capacitor. This causes V2 to switch
back to its normally on condition, and VI to
off. The circuit is now ready to receive the
next triggering signal. Since the one -shot
multivibrator automatically returns to its
original state after it goes through its cycle,
it is sometimes called a monostable multivibrator.
(Continued on page 36)

-a

ELEMENTARY ELECTRONICS

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MARCH -APRIL, 1967

35

(DA

Fig. 6. Variable-frequency multivibrafor can be used
as a code practice oscillator if you rep/ace s.p.s.t.
switch with a morse -code key. While output is not a
sine wove if is suitable for this use. Output can
also be used as generator for signal -tracing tests.

FLIP -FLOPS

Continued from page 32

10K

150K

AUDIO
TRANSFORMER

-1

2K

Bi
SPKR

PNP

= 3 -9V
fT

BATTERY

I(
,01MF

500K
TONE

3.3K

SPST
SWITCH

e

I.OIMF

A Practical Application. As we have
seen, the input pulse merely serves to trigger
the cycle, which then takes off and completes itself. The output signal is always the

T0 2ND
STAGE
PNP

FROM

FEEDBACK
CAPACITOR

SECOND
STAGE

FEEDBACK SIGNAL

COLLECTOR SIGNAL

TO BASE

Fig. 7. Partial circuit and waveforms of Fig. 6.

same length, since it is timed by the coupling
capacitor and resistor. This feature might be
useful for, one example, in a transistorized
automobile tachometer. Triggering signals
obtained from the ignition system distributor
MULTI VIBRATOR

points tend to vary in length, according to
engine speed. But applied to the one -shot
multivibrator, all input pulses are cleaned up
before proceeding further into the tach's circuits. Output will contain only the number
of pulses per second-not their varying
length. Another application is in computer
counting. Let's assume that a given one-shot
multivibrator always produces an output
pulse which is one second long. Now trigger
that circuit with a continuous stream of short
input pulses, each one -tenth second long. The
result will be one output pulse for every ten
input pulses. (After the first input pulse, the
circuit takes off and can't respond until it
resets, just as the eleventh pulse comes
along). This function can perform addition
by ticking off every ten pulses. A third important application of the one -shot multi vibrator is in expensive oscilloscopes where
it becomes the Schmitt Trigger. When the
scope is examining a complex input signal,
the triggered sweep can be adjusted to lock
on to any desired portion of the signal. This
synchronizes the scope to produce stable
images. (Less sophisticated scopes try to lock
on or synchronize with the strongest portion
of the input signal).
Construct Your Own. The circuit given
in Fig. 6 is that of a practical flip -flop you
(Continued on page 110)
LAMP AMPLIFIER

S

93 LAMP
12V, !AMP

Fig. 8. Multivibrator
drives direct- coupled amplifier
to flash 12 -volt, -amp
lamp used in high- intensity
lights. Power transistor
is needed to carry such a high
current. If you decide
to build flasher use heavy-duty
-cells won't last.
battery
1

Q4
2N441

I2V-

-D

36

ELEMENTARY ELECTRONICS

those
ELIECMCM11©
DI1A@G3AG3

BY

E.

NORBERT SMITH

Diagrams are the maps of electronics. If you don't understand them it's a
good bet you won't get anywhere. Here are the most frequently used types.
Electronics is one of the largest and fastest growing industries today. It varies
in complexity from inexpensive audio amplifiers to complex systems that make possible
a successful soft lunar landing. As with any
specialty, various abbreviations and symbols
are used to such an extent that the outsider
is left bewildered, if not frightened.
The diversity of electronics may be seen
in the variety of electronic diagrams used.
They range from the simple block diagram,
familiar to the most casual electronics reader, to highly complex logic diagrams used in
computer work. A better understanding of
the various electronic diagrams used may
prove useful as well as interesting.
Block Diagrams. The block diagram is
the simplest of all the electronic diagrams
and is perhaps the most widely used. It consists of named boxes connected by a series
of lines. The rules for the block diagram

4

are few and flexible. The named boxes or
blocks may be a single transistor or an entire
radar system. The lines generally show signal flow but can just as easily identify primary power distribution or direction for a
laser beam.
Flexibility is what makes the block diagram
so useful. No matter how complex a circuit
or system may be, a simplified block diagram
can be drawn to bridge the gap in understanding. The signal flow in something as
complex as a dual-conversion receiver can
easily be illustrated with a simplified block
diagram. Once you have mastered the simplified block diagram a more complex block
diagram could be explained.
Primarily then, the block diagram is an
introduction; a training aid -useful for describing an electronic circuit or system to
someone for the first time. It provides an
uncluttered, functional view of a circuit.

-Jvv A

T

Single Cell
(

Fixed

(

)

Variable)

Capacitor

Anlerna

-47111111-

(

-ten vv_

Fixed)

Battery

(

Variable)

Resistor

/7137
(

Earth)

(pop)

(Chassis)

Ground

Transformer

Iron - Core Choke

(npn)
Transistor

Some of the many symbols used in schema /ic diaaroms.

MARCH-APRIL, 1967

37

(g @

ELECTRONIC DIAGRAMS
FIRST
CONVERTER

- ---'

SECOND
CONVERTER

1650kHz

r-

262kHi

I

MIXER
I

I

MODULATED
RF TO
DETECTOR

(

LOCA

L----J

Ì

Block diagrams are helpful in tracing signal flow hut they are seldom included in manufacturers' manuals. They
are used extensively in advanced texts covering the more complex units like TY and communications receivers.

The block diagram is by no means limited
to the classroom. It has found wide application in the advertising medium. For example, it is often used to acquaint prospective
customers with the operation of an electronic
product without giving away the actual circuit. As a troubleshooting aid the block diagram can help to isolate a trouble to one area
or stage by showing signal flow.
The block diagram, however, doesn't show
enough detail to understand how any given
circuit performs its function. All it does is
indicate the individual stages. To indicate
the actual electronic components that make
up a circuit the schematic diagram is used.
Schematic Diagrams. The schematic
diagram could be called an electron's eye
view of the circuit. It consists of lines representing wires and symbols designating every
electronic component as shown in its proper
electrical relation to the remaining circuit.
This electrical relation (rather than physical
relation) may be somewhat difficult to grasp
at first. The majority of the blueprints and
drawings (whether it is a house plan or
design for a machine) are carefully drawn to
maintain proper physical relation, but any
physical resemblance a schematic diagram
may have to the layout of resistors and capacitors in the working circuit is purely accidental. The schematic diagram's purpose
is to show exactly what is connected (electrically) to what -not where the components
will be physically positioned.
The abbreviated table of schematic symbols, on the preceding page, would need several pages to present completely-with all the
variations and combinations.
Some of the more common electronic
symbols, as used in the industry today, are
38

pictured in the table. They may seem rather
arbitrary at first, but a little thought will
show their descriptive nature. How could
a capacitor be described more clearly than
two plates separated by a gap, or an inductor
by a looping line. These symbols have found
such universal acceptance that, for example,
an American electronics engineer, technician
or experimenter will find only a little difficulty "reading" a German or Japanese schematic diagram.
Schematic diagrams are the written language of electronic circuits. They are used
from the conception of an idea through development and testing and finally they are
an invaluable road map in troubleshooting.
Many electronic circuits start as a schematic diagram scribbled on a scrap of paper
by an electronics design engineer. This rough
schematic may then be modified, added to,
and redrawn dozens of times before the circuit is built and tested. To the design engineer, the schematic diagram is a tool with
which to make calculations; try new circuit
configurations and make preliminary cost
estimates.
Schematic diagrams, along with block diagrams, are used extensively in electronics
training at all levels. They make it possible
to understand how even the most complex
system functions. At first glance the schematic diagram of a TV or even a radio seems
quite complicated but after becoming familiar with the symbols it will become apparent
that many of the circuits seem duplicated, at
least in part.
All components grouped around one transistor, or tube, are often referred to as a
stage. In a radio there may be two or three
identical, or at least very similar, IF ampliELEMENTARY ELECTRONICS

Most RF stages have certain
similarities, as do audio or IF stages. After
the few basic circuits are understood a complex electronic circuit can be reduced to
many simple stages which, when taken one
at a time, are easy to understand.
In addition to having each component,
its value and electrical position, a troubleshooting schematic may have such helpful
guides as waveforms, voltages, resistance to
ground, etc., marked at various points in the
circuit. These guides are used in troubleshooting when an instrument indication is
found that differs from the value printed on
the schematic. The defective component can
then be found more quickly.
Although the experienced engineer, technician or experimenter can usually build a
working circuit from only a schematic diagram, more information is needed by the
beginning experimenter. In working with
high -gain and high- frequency circuits, lead
dress becomes just as important as using the
fier stages.

.

proper components. Signal leads must be
kept short, special grounding methods may
be required and care must be observed to
avoid unwanted hum pick-up. To assure the
circuit works as it was designed to, the original layout must be used. This requires tht
use of the pictorial diagrám.
Pictorial Diagram. The pictorial diagram
is the most lifelike of all the electronics diagrams. Often actual retouched photographs
are .used for a pictorial diagram. It is common, however, to have draftsmen or technical illustrators draw the pictorial diagram.
In order to illustrate a crowded area an exploded view or exaggerated drawing is used.
The purpose of the pictorial diagram is
to show how and where (physically) each
component is mounted. All tie points, sockets and mounting hardware are shown.
Generally, the components are shown simply
by an outline drawing with their circuit designation and possibly their value written on
them.
(Turn page)
Artist's concept of the electronic
circuit is the pictorial diagram. The
one at the left shows the same circuit as that in the photograph below.
the pictorial diagram all connections are shown as they would be
made to the component -only the
chassis is not shown here. Tubular
objects are solderless connectors.
In

Sl
red

green

green

. Yellow

Ti

green

JSPKR

(right) shows actual
construction of the unit. Some of
Photograph

the connections are obscured and
others are a confused jumble. Its
a good assembly illustration as
all nods are shown in their erect
positions- mounted in cabinet.

MARCH-APRIL, 1967

39

AgELECTRONIC DIAGRAMS

Pictorial diagrams enable the inexperienced builder to duplicate the layout and
lead dress of the professional. They enable
production -line workers to assemble complex
electronic equipment without knowing any
electronic theory. These detailed drawings
are what made electronics kit building a
reality.
By using the pictorial diagram a beginner can build an electronic circuit and by
carefully rechecking his work for errors a
circuit can usually be made to work (at least
in modest construction projects) but the
pictorial diagram is meant to be used as a
layout guide with the checking done using
the schematic. Even though all the components, hardware, and so on is shown in the
pictorial diagram, it becomes difficult, especially in larger construction projects, to
determine where to drill holes in a chassis or
panel. A drill diagram is needed.
Chassis Layout Or Drill Diagram. The
chassis layout or drill diagram is for the metal
worker. It is a sketch that shows the location
and size of each hole to be drilled in the
chassis or panel. Dimensions are usually
referenced from one corner or edge. In industry, drill diagrams are an absolute necessity because the metal work is done in a
different area (or even subcontracted) than
electronic assembly. Each panel and chassis
must look like every other panel and chassis for that certain piece of electronic equipment.

The chassis layout or drill diagram is
generally the work of a specialist called an
electronics packaging engineer or designer.
He works with the circuit design engineer
to package the electronics in a box that meets
all the circuit requirements, is pleasing to
the eye and mechanically feasible to fabricate. The packaging engineer must know the
exact dimensions of all components, which
ones produce RF noise or heat, which controls are used the most, etc. He then may
go as far as building a mock -up to find the
layout that is most suitable. From this final
layout the drill diagram is sketched from a
prototype unit and finally drawn by draftsmen.
The hobbyist that uses a drill diagram will
find it a great help in producing a neat, clean,
finished project. Unless a considerable
amount of time is spent measuring components and planning their exact location a
rather haphazard layout can result. In electronic circuit construction all the mounting
holes should be drilled first to avoid getting
metal chips in the partly built circuit. Also
if all the holes are drilled at one time, the
panel or chassis may be painted, or otherwise finished as desired before the components are mounted -without scratching the
finish by drilling some holes later.
Printed Circuit Layout. Due to reduced
size, ease of assembly and increased reliability more and more electronic circuits are
being produced on printed- circuit boards.
It's not uncommon to find printed -circuit
boards in home -built projects. In its simplest
form the printed- circuit board is an insulator base (such as phenolic or fiberglass)
layout diagram style
Chassis
shown here is suitable for most

/

HOLES FOR 4 -40
5á
SCREWS
(4 REQ.)

BOTTOM

4 -40

ally a box such as one shown here
would be drilled, punched and

HOLE

DIA.HOLE

2

construction projects. Commercial
drill diagrams would show a flat
surface for each side that is to be
drilled, punched or cut out. Gener-

cut before
unless

it

it was bent into shape
was a commercial box.

L

COVER
á

g DIA.HOLE
(2 REO)

DIA. HOLE

(2 REQ.)

3

FORES

s

6 -32 SCREWS

40

ELEMENTARY ELECTRONICS

layout artwork must be done on a dimensionally stable material (such as Mylar)
which will not shrink or stretch from heat
or humidity.
The printed -circuit layout diagram is a
very specialized diagram -for only one specific application; that of producing a printed
circuit. Shear and trim lines are usually included as well as a reduction guide. A reduction guide is a line with a reduced length
specification. When photographically reducing the printed circuit to the right size, this
reduction guide is used to know exactly how
much to reduce it.
Logic Diagrams. The logic diagram is
used for designing computers. It is sort of
a cross between the schematic and block
diagram but it is mostly a block diagram. A
15*
16
computer is a highly electronic machine
containing tens of thousands of transistors.
It is relatively simple in spite of its complexity. Computers are constructed by using
a few basic circuits many times, over and
over. In the logic diagram each of these
11ß"
circuits or logic functions is represented
by a symbol with the interconnecting lines
Printed- circuit layout is almost twice the finished
representing logic or signal flow. Each of the
size. Doughnut -shaped pads surround holes for piglogic symbols represent an electronic cirtail leads of resistors, capacitors and transistors.
cuit, such as an and gate, bistable flip -flop,
function.
(previously applied to the copper foil) are ex- etc., which performs some logic
one comrepresent
to
a
symbol
use
of
The
posed -much like photographic prints are
simplifies the
exposed. This positive is the printed circuit plete logic function greatly
logic diagram by omitting such repetitive
layout.
For some simple, not -too -small applications the layout is produced 1 to i (actual
size) but usually the printed- circuit artwork
is several times larger than the finished board WITH POSITIVE INPUT
WITH GROUND INPUT
LEVEL, POSITIVE OUTPUT
-then reduced, photographically, to exact LEVEL, GROUND OUTPUT
(NAND)
(NOR)
size. It is easier and more accurate to lay
out a circuit several times larger than the Logic diagram symbols are many and varied. These are
from MIL -STD (Military Standard) 806B. Industrial
actual circuit board-then reduce it to actual
designs by different manufacturers often use somewhat
size-than it would be to try to lay out a
in the logic diagrams.
miniature printed-circuit board actual size. different forms as logic blocks
To understand how reducing the size improves the accuracy, assume for a mbment nonessentials as supply lines, bias networks,
that a draftsman can work by using a grid etc. This electronic shorthand still illustrates
pattern to a tolerance of -i-1in inch. Also exactly each logic function and the signal
assume that a transistor is to be mounted distribution. Computers are designed from
and the holes for the leads allow only ±1/32 a logic approach with the designer hardly
inch ( ±.03 inch) tolerance. The draftsman knowing how, electronically, each function
must be very careful or the transistor leads is performed. In fact even at the maintenance level the logic diagrams are used to
will not fit the hole. On the other hand, if
the draftsman is working on a layout that aid in locating the defective plug-in board
which is replaced-all without the aid of a
is to be reduced by a ratio of 4 to 1 he can
make an error of 4 times Áu or Vs inch and schematic diagram. Only if the board is to
the transistor leads will still fit. Or looking be repaired must a schematic diagram be
at it another way, a ±-1/32-inch error on the used.
1;^, *
to ralrnre
1 oglc alagrams
large layout reduces to only -!-Mí28 inch. All

covered by a thin sheet (foil) of copper, on
one side or both sides. Most of the copper
is etched off leaving a pattern of copper on
the board. This pattern of copper is used in
place of the interconnecting wires for the
components that are mounted on the circuit
board.
Mass produced printed -circuit boards are
usually made by a photographic process.
This requires a positive transparency through
which areas of a photo-sensitive coating

D-

03

an

MARCH-APRIL, 1967

°

41

Wg

ELECTRONIC DIAGRAMS

lating applications. Complex industrial production machines, also computers, are often
presented by a logic diagram. The logic
diagram is not only an aid to understanding
how a machine operates but is valuable in
troubleshooting as well.
Ladder Diagram. The ladder diagram, so
named because the circuits are laid out horizontally between two vertical wires like a
ladder, is widely used in industry, but is not
as well known as some of the other diagrams.
The ladder diagram is similar to the schematic diagram in that all electrical components are shown, but the ladder diagram is
laid out from top to bottom usually in the
order in which it works. Some of the symbols used are similar to those used in schematics but some seem quite different. The
ladder diagram was developed as a troubleshooting aid for industrial production -line
machines. Wherever there is mass production, there is automation and with it electrical or, if you prefer, electronic control circuits. Just trying to find out what circuits
a given relay controls on a many-page schematic diagram becomes quite a task. The
ladder diagram greatly simplifies the job by
showing all the circuits a relay controls on
the same line as the relay. At right is an
example of a ladder diagram; a circuit to
provide a temperature controlled environment-heating and cooling -using a modified refrigerator is given in part.
To illustrate how the ladder diagram
works consider for a moment what is required to energize RLY4 on line 6. One
terminal of the coil of RLY4 is connected to
one side of the 117 VAC line. If S1, the AC
power switch, is closed, the other terminal of
the relay coil is connected to the other side
of the line through the contacts of RLY 3,
S4, the overtemperature light (with a series
100k resistor) and the overtemperature
thermostat contacts (that are paralleled with
a 100k resistor). The relay coil cannot be
energized by the small current that flows
through either of the 100k resistors. But even
the current through both resistors is enough
to light the neon lamp. Now if S4 is pressed
the overtemperature light will go out
will
also go out if the contacts of RLY3 are
closed. As long as the overtemperature light
is on, RLY4 is not energized. Only when

-it

42

RLY3 contacts are closed (or if S4 is
pressed) and the overtemperature thermostat contacts are closed will the coil of RLY4
be energized. The coil of RLY3 is not shown
in this portion of a very long diagram.
The ladder diagram makes a convenient
tool with which to design and troubleshoot
automatic and production machines. You
may find one pasted on the back of your
automatic washing machine or refrigerator.
1I7VAC
FI
F2

SI

AC POWER

SI

Si

100K
vww

2

AC

DOOR
SWITCH

ON

n_04.7

CLOSE -DOOR

RLYT

OPEN

LIGHT

INSIDE

ON~ S34

OFFFF

LIGHT

AUTO

I

100K

LIGHT

RLY' 1

T

Crqp

s4

FYYYY T
RLY2

CONTROL THERMOSTAT
OPEN- TEMP RISE

L-mio

IOOK
NO

6.+ -+S4

OVERTEMP
RESET

6.9

OVERTEMP THERMOSTAT
OPEN - TEMP RISE

RLY3

w

_

100K

RLY4

FAN

100K

OVERTEMP

LIGHT

ON" S5

*FAN
CIRCULATING

OFF

RELAY CONTACTS,

--H-- NORMALLY

-->-

FAN

LAMP

OPEN (NO)

NORMALLY CLOSED (NC)
MOTOR

Ladder diagram simplifies circuitry by separating
relay coils from relay contacts. This eliminates
the many lines, representing wires, that crisscross
most schematic diagrams. Ladder diagram is limited
to control circuits in appliances and in automation.

The ladder diagram given here is much
abbreviated
would run most of the way
down the page. It is only an illustration of a
typical ladder diagram-just to be compared
with the previously given types. Diagrams
used here were taken, partly or completely,
from actual devices.
There are many other kinds of electronic
diagrams in use today but they are beyond
the scope of this article. Only the more common and useful types have been discussed.

-it

f

ELEMENTARY ELECTRONICS

DESIGN NOTES
FOR A HAM
CONTROL CENTER

NAM

r

BY HOWARD S. PYLE

W7OE

SHACK

WITH A
HEART
"And what may you mean by that ?" you
may well ask! Well, just what is the heart
of a ham shack? Obviously it is the center
from which control of all the equipment is
effected. If you don't have such centralized
control, you're antiquated. That's right! If
going on the air means you have to independently switch on every piece of gear
you'll be using- transmitter, receiver, keyer,
antenna rotators and miscellaneous accessory
equipment by flipping a myriad of switches
scattered on their individual panels you're
doing it the hard way!
Centralized control can be as simple or
as complex as the multiplicity of your gear
or your own personal ideas of operating
convenience dictate. For a simple novice
set-up, for example, comprising only a transmitter, receiver and possibly an electric
clock, a control center may seem to be a
bit on the ridiculous side -but is it? Take a
quick break -down; obviously the clock must
run continuously-24 hours a day -to be
of any value. Often it occupies a spot on
top of the receiver or transmitter or it may
be hung on the wall in a spot not always
convenient to read quickly when logging.
The receiver has a toggle switch on the panel
for AC power on -off control perhaps; the
transmitter no doubt is likewise fitted. Both
have, or should have, independent fuses.

-

w

MARCH- APRIL, 1967

Too often these are buried deep within the
chassis, far from a convenient spot for a
quick change should you happen to blow
one. Why not group all of these controls,
fuses and, yes, even the clock and indicator
lights in one neat little package together with
a main switch and fuse, right in front of you?
A Start. Take a look at the little unit in
the photo group on the next page. This is
the heart of a simple novice station. In
addition to the clock, a main -power toggle
switch and fuse, together with an indicating

TO

TRANSMITTER

P

TO

RECEIVER

Simplest control center has main switch (left) and
two switched outlets or receptacles (R) for power
plugs of transmitter and receiver. Clock is not
turned off by either main switch or by main fuse.
43

1

c-

ttt777

j

light are provided (in the vertical row to
the left of the clock). If the main switch is
turned to off no power can reach any of the
other switches and all equipment except the
clock is effectively turned off. The same
condition occurs should the main switch
fuse' blow. However, assuming the fuse is
good and the main switch is on, the bank
of switches, fuses and lights to the right of
the clock provide independent control of
each piece of equipment as well as a visual
indication that it is on. (In the unit shown
in the photo, one switch, fuse and indicator
light could be deleted as this unit was built
in the days when a Conelrad receiver for the
Ham shack was a legal requirement; the
control could however remain and be used
for some other piece of equipment.)
With a little magic box like this, it is
obvious that the transmitter and receiver
can be separately switched on or off, if
the power switches on their individual panels
are left in the on position. If either piece
of gear blows a fuse it is right in front of
the operator in an insert type fuse-holder;
changed in a jiffy -without removing umpteen screws to dig into a chassis! Remember
though to either by -pass the chassis fuse
with a wire or use one of higher- than -normal
rating with the normal size placed in the
control unit. This little box then constitutes
just about as simple a control center as could
be devised for a minimum amount of equipment yet it is just as effective and conveni911

.,m.....,111..

11111

LINE

HAM SHACK HEART

.,,,,.,111..,,,,,,,,,,

,

........11..,,,,11m,.

To
TO
RECEIVER

pi of lamps (l) across lop of diagram indicate
(from left to right) main power, transmitter power,
power amplifier on -off, and receiver power. Fuses
(F) protect house wiring from fuse- blowing defect.
Four

ent a centralizing point for the station equipment AC power as its more elaborate big
brothers.
Audio Tool Now take a look at the little
unit in the upper right of the group photo.
This lad chose to include his speaker in the
control-center cabinet. In fact he also included a power amplifier stage for the
speaker as well! His clock was wall mounted
within easy visual range -no need to move
it to the control cabinet. His switch, light
and fuse combinations included a main ACpower control, a similar combination for the
transmitter and again, a duplicate group for
the receiver. The third fuse- switch-light
string controls the power amplifier stage
for the built -in speaker.
A control center is not necessarily limited
to power circuit controls-far from it. Almost any station accessories can be included

.,.,...,.,.

1111...,.,,,.1,,,.11111,,,,,,,,.1..1,

1.,,,,111111,,,,,1111111,1,.1111..11:P1

For a simple installation (top
left) all you need is a couple
of switches and an equal number of pilot -light and fuse ho/der assemblies. If you must
start small it is best to leave
lots of room for expansion
equipment never dreamed of now.

-for

;/1/11111

44

.

1..

.........

,

1.111111.111111111111111111..1..1..11..1.,.1111111...1.11111111111111111.1.1111..1..1.1.11111111.

..1.1...1.1..1...111111.1.111111111.1.....1..1....1..1...111.1.11..111..1.1.11111111111111-..1.1

ELEMENTARY ELECTRONICS

One of the twelve slide switches on the
panel permit silencing or activating the alarm
circuit. A built -in RF keying monitor is
provided and the two knobs (in a vertical
plane on the left of the panel) control the
volume and tone of the monitor. The monitor is AC powered -with a slide switch and
AC fuse in its supply line together with an
indicator light. The other four slide switches
on the left hand sub -panel control not one
but four transmitter AC power supply
sources. A duplicate sub -panel, on the right
(which also has six slide switches), controls
the AC supply to four receivers. The left
hand upper slide switch on this panel selects
either the built -in speaker or headphone jack
on the rear panel. Next to the RF- monitor
tone control on the lower left of the main
panel is a two -position rotary switch which
connects the output of any of four receivers
(Continued on page 112)

as well. Take a look at the unit at the
lower right of the picture. Note that both
a clock and a speaker are mounted in the
panel of this control center. In addition, an
RF- keying monitor is mounted in the upper
left hand corner of the panel and a noise
limiter (with rectangular dial plate) on the
right. Switches, fuses and indicator lights
for a transmitter, receiver and the RF -monitor power supply are provided as well as
fuse, switch and indicator. light for the
incoming AC power. A fuse is also provided
for the clock circuit; perhaps a superfluous
refinement although adequate fusing of all

circuits is never wrong.
The Grand Daddy. Now have a look at
the lower left hand unit . . . the "granddaddy" of all control centers. This one
leaves little to be desired. A jump type
clock with a ten -minute call -ident alarm buzzer occupies the upper center of the panel.

T

P

Additional switches added to this
control unit are not only for the power
circuits -audio circuits are
controlled as well. This shows the
design of a control center is
suitable to all types of controlling
-audio as well as power
high -fidelity systems. Control center

RECEIVER

-in

TRA7 NSMITTER -

can be designed to switch speakers,

select tuner, turntable or tape player
outputs and make connections for
tape recorder to any of the components
in the system-even for stereo.

TO

PHONE JACK
AUDIO
NOISE

RF
KEYING
MONITOR

TO

FROM

I

LIMITER

RECEIVER

RF

PICKUP

COIL
KEYING

Grand Daddy of
all controls most
functions needed
by the active amateur
radio operator.
In fact this control
center, with a
few exceptions, would
do for commercial
installation of an
efficient, 2- .ay
communications setup.

OIL

them

You may not need
all these controls to

start -just leave
panel space to odd the
new controls as
you add new items of

IUI

ON

MONITOR
POWER

AUTO
ALARM

lil11©

VIII©

111111©

VIII©

U

AMP

RS

iL

LIMITER

NOISE
SPEAKER

TRANSMITTERS

©óFF
O

O

RECEIVERS

aQIL

ILO

O

TRANSMITTER FUSES- 5 AMPS

O

11111

©2

: 111111©
RECEIVERS

IL®
ILO

OUT

111111©

111111©

OIL

LIMITER
IN

PHONES

Q

,'11111©

(fRS

O

10O

f
IL

OIL

2

MONITOR MORSE SOUNDER

OTONE

MAIN

CLOCK

FUSE

Q

TRANSMITTERS

SWITCHES

I
OFF

TS
SWITCH

MONITOR VOLUME

c:,111111©AL11111

POWER

MAIN

MONITOR

OIL

RECEIVER NO

.3

2

OUT

\

RECEIVER OUTPUTS AUDIO FRIER

Q
RECEIVER FUSES

-2 AMP

O

Y

MARCH-APRIL, 1967

45

A

veri that's on for 24

hours only has all the

makings of a once in -a- lifetime deal!

December 1, 1966, may have been just
another day in the lives of most people, but
it was a very special one for the staff of the
National Bureau of Standards' station WWV.
It was also a special day for countless Hams
and SWLs around the world, and in a most
unusual way. What made the day for the
WWV people was inauguration of transmissions from that station's new home in Fort
Collins, Colo. And for DXers of every ilk,
the day offered a rare opportunity to snag
what had all the markings of a rare QSL.
When you come right down to it, of
course, securing a QSL card from WWV is
no great shakes, since the station mails out
hundreds every year. But this was a card
with a difference, for it was intended to
furnish the WWV staff with valuable information on how the station was being re-

Above, WWV's First-Day QSL (shown
greatly reduced in size). At left, part
of antenna array at new Colorado site.

ceived from its new location. Just as importantly, it was also designed to honor those
Hams and SWLs who succeeded in logging
the station's new transmitter during its first
day on the air. Since WWV is a cinch to
tune on one of its many frequencies (which,
by the way, are the same 2.5, 5, 10, 15, 20,
and 25 mHz as always), applicants were
required to correctly quote a new voice announcement made during the first day of operation from the new site. Further, all reports had to be postmarked before midnight
of December 2, local time.
Most of WWV's equipment is brand spanking new, and the present site is more
centrally located than the old one at Greenbelt, Md. And while final tabulations weren't
available at time of writing, NBS officials
expect WWV will be received throughout
most of the continental U.S. better than ever
before. All of this means that a WWV QSL
ordinarily belongs anywhere but in the rare
category, although that First -Day QSL is another matter. For first days and First-Day
QSLs just don't come along that often.

-RON
46

MITCHELL

ELEMENTARY ELECTRONICS

HIGH- FIDELITY
LAFAYETTE Model RK -840
4 -Track Solid -State

Stereo Tape Recorder

Though just about the size and weight of
the new breed of battery operated tape
recorders, Lafayette's new RK-840 is a fullfeature, AC- powered, family -style recorder
that packs into one case decent performance
from several points of view; from Pop's hi-fi
flat frequency response to junior's experiments with cavernous, echo sound effects.
Features. The RK -840 has switch selected speeds of 71/2 and PA ips. The 1% ips
speed is available by removing a sleeve on

the capstan shaft. Each channel is independently push-button controlled; either track or
both may be selected for recording. With the
exception of the record button interlocks, all
functions (FF, stop, play, pause and FR) are
determined by a single mode switch. A special push- button switch selects the proper
equalization for a phono pickup, allowing
direct recording without the use of an intermediate amplifier.
Both microphone and high level inputs are
provided for the L and R channels, each
channel controlled by an independent volume
control. The tone control, which is effectively the speed equalizer, is ganged; a single
setting determines the equalization for both
channels. Line level outputs as well as a
stereo headset jack are provided.
MARCH -APRII,, 1967

Both the left and right power amplifiers
and their associated speakers are built -in. For
those who prefer "big speaker" sound, external speaker jacks are provided that automatically disable the internal speakers. One
other big plus, the unit can operate with the
cover closed.
Two calibrated VU meters, one for each
channel, indicate both the record and playback levels. The meter switching is automatic. When the recorder is in the record
mode, the meters indicate the record level;
when the recorder or track is set for play,
the meters indicate playback volume levels.
How It Tested. All functions delivered, at
the least, decent sound quality and /or convenience. In any mode, the recorder's
mechanical operation is typical of the simplicity of family models. The electrical performance in terms of frequency response is
shown in the graph. Note that at 71/2 ips
both tracks are within 2 db of each other;
they can be made closer yet by juggling the
setting of the level controls. The indicated
response was obtained with the tone control
in the 10 o'clock position. Unfortunately,
the tone control is not calibrated for the
must be de"flat" position at any speed
termined by the user. But who cares? Just
set it for best sound.
At 33/4 ips the tracking is again good to
about 8 kHz, diverging to the upper limit of
10 kHz; but this is still good when one considers that the RK -840 is in the budget price
range.
We did not check out the 1% ips speed
with instruments as it is obviously intended
only for speech reproduction. A dictation

-it

recorder's two basic speeds of
third speed -17/8 ips -can be
obtained simply by removing sleeve from capstan.
Push -pull switch selects
71/2 and 33/4 ips, but a

47

Ol®

The microphone input impedance can
create some problems for the recordist prone
to experiment with different microphones.
While the auxiliary (line) input impedance
is 500,000 ohms, and the phono input is
50,000 ohms, the microphone load is 10,000
ohms -designed for the two microphones
supplied with the recorder. Do not connect
microphones intended for load impedances in
the megohms, such as a hi -Z crystal or ceramic model. Severe bass attenuation will be the
end result.
The Sound Counts. Perhaps the most
important aspect of any of the miniature
portable recorders is the sound quality
through its own playback, for it is one thing
to feed a tape deck through a hi -fi amplifier
(even the cheapest of recorders can do that
well) but it is quite something else to get
decent sound out of very small speakers.
The integral sound quality of the RK -840
is best described as "mellow." The sound is
balanced slightly towards the bassy side, with
a generally ear - pleasing tone associated with
wood speaker enclosures (the cabinet is
wood), rather than the brittle, slightly edgy
tone that results when small speakers are
combined with plastic or metal enclosures.
Considering the budget price of $169.95,
Lafayette has managed to combine the characteristics of a tape deck suitable for a budget
priced Hi -Fi system with the advantages and
conveniences of a portable family type recorder in the RK -840.
For more information write to Lafayette
Radio Electronics Corp., Dept. CP, 111
Jericho Tpke., Syosset, N. Y. 11791

Lafayette RK -840

test at this speed rated the RK -840 as excellent.
With a record level of "0" VU at 1 kHz,
and the level control wide open for playback,
the maximum distortion checked out at 2.8%
through the line level output jacks. Though
the internal power amplifiers are rated for 3
watts each, with the recommended "0" VU
recording level the maximum power output
was 2.2 watts into 16 ohms-the recommended internal and external speaker impedance. At typical room volume power
level of 1.0 watt, the total overall distortion
was less than 1.5 %. Using the line output
and your own hi -fi amplifier, the distortion
at the recommended recording level should
measure less than 1%-typical of even much
more expensive recorders.
Inputs. The various input sensitivities are
about typical for portable recorders; for the
indicated "0" VU recording level the line
inputs require 0.1v., the microphone inputs
0.2 mv., the phono input 0.6 mv.

Unusual -and valuable-feature of the RK -840
built -in equalization for dubbing
any LP record. Magnetic -phono pick+2
up can be fed

4-

its

is

directly into recorder.

0

Overall record /play response of
RK -840 at 33/4 ips was flat within
±2 db over major portion of audio
spectrum. Note relatively small
divergence between two channels.

V)

w

m
Z3

0

2

i

4

-6

LAFAYETTE RK

34IPS; TONE

-840

-_

---

CONTROLS

FLAT
I

50

I

RIGHT CHANNEL
LEFT CHANNEL

1

I

100

200

500

2

1

5

10K

15K

FREQUENCY

LAFAYETTE

Two channels fell within 2 db of
each other at 71/2-ips setting.
Useful response was maintained to
15 kHz, indicating recorder is ca-

7i

RK -840

IPS, TONE

_
FLAT

RIGHT CHANNEL

LEFT CHANNEL

pable of full- fidelity performance.

100

200

500

IK

2K

5K

10K

15K

FREQUENCY

48

ELEMENTARY ELECTRONICS

COVER
STORY

TRANSMI
SPEECH
PROCESSOR

You don' t need Hi -Fi to
make your needs known on CB.
So it pays to weed out
power- wasting frequencies.

by

Alice

you build this Speech Processor and
hook it to your rig it will be a popular
topic of conversation when you get together
on the air with the gang. CB'ers and Hams
alike have much interest in getting the most
out of their low -power rigs.
There are a number of well known ways to
squeeze the last milliwatt out of the transmitter without actually increasing the final
amplifier's input power. Probably everyone
realizes the importance of a good, properly
matched antenna, a low-resistance ground
system and a low -loss antenna feeder. But
given the crowded conditions on many
amateur bands and the inherently -low power
capabilities of CB equipment, more talk power is always needed.
The Speech Processor greatly increases
the effectiveness of any AM transmitterMARCH-APRIL, 1967

E.

Norbert Smith

and it is perfectly legal to build, install and

adjust without the appropriate license (for
CB transmitter repair). By combining three
methods, which are commonly used and have
proved highly effective, into one small unit
the benefits of all three can be utilized for
maximum modulation.
Compressing the Frequency Band. Most
of the intelligibility in speech frequencies is
centered between 500 and 2500 Hz (cycles).
However, a large percentage of speech power
is normally below 500 Hz. If the frequencies below 500 Hz are reduced or eliminated
the frequencies actually needed for communication can be increased in amplitude
without exceeding 100% modulation. Two
additional bonuses that frequency compression contributes are: reduced hum (because
the low- frequency response is cut) ; decreased

D

e

Block diagram of Speech Processor makes circuit
(below) easier to understand
you wont to dig
into the technical side of the unit. You don't have
to know how it works to build it or use it
it might make it a bit easier to set controls.

-if

D

SPEECH PROCESSOR

-but

HIGH LEVEL

DIODE

AMPLIFIER

ATTENUATOR
Dl, D2

02

to

VOLTAGE

EMITTER

AMPLIFIER

FOLLOWER

03

Q4

IL

A

DC AMPLIFIER

AGC

AGC
FILTER

Q5

RECTIFIER

D5, 06

4

AUDIO
OUTPUT

RF bandwidth because the high-frequency
generated sidebands are attenuated or miss-

sampling of the output of the speech amplifier is rectified, filtered and used to control
the gain of an earlier stage. The output then
will have constant average amplitude, enabling the transmitter to be fully modulated
regardless of differing voice levels and different lip to microphone distances (within
limits of course).
Speech Clipping. Speech waveforms
contain considerably less average power than
a sine wave of equal peak amplitude because
of many high -amplitude, low-energy, short duration peaks in speech. Since the percentage of modulation is based on peak values
a transmitter modulated 100% by a sine
wave will contain many times the sideband
or talk power of a transmitter modulated
100% by speech waveforms of the same

ing altogether.
Volume Compression or Audio AGC.
If a modulator is properly adjusted to give
100% modulation on voice peaks, it will fall
far below 100% modulation under a major
portion of normal operating conditions due
partly to changing voice intensity (as with
expression and mood), and partly to changing lip -to- microphone distance with changing
positions, etc. Vast differences also occur
when the microphone is passed from one individual to another.
Obviously it is desirable to modulate the
transmitter as fully as possible at all times
and the most dependable method is with
audio AGC (Automatic Gain Control). A
+12V

RI

330K

+150V
R3
10K

01

2N1304

R6

R7

50K

680K

BASS
CUT

c

C4

C2

.005MF .05MF
CI

100n

R2

SI

100K

MF

R9
22K

,IMF

b02
e

.IMF

R10
1K

D2
1N461

+

R12

C6

2N3712
BASE

03
2N1304

b

C11

R15

R31

R17

100K

270n

-10K

10MF

5MF
R23
4.7K

J

R24
D6
1N461

1K

e

+ C13

D7 +
1N46

50

2N1304
b

1K

05
2N1304

2N1304

04

e

HI

en
+ C3
5MF

D

c

C7

Rll
2N3712 47k

c

10K

1N461

C5

c

R16

R14
2.2MEG

R13
10K

D1

LO

R4

.02

+12V

100

R25

C12

IMEG

5MF

D5

IN461

MF

ELEMENTARY ELECTRONICS

i3

ßi10

Alternate circuit for AGC rectifier and filter adds
three controls to Speech Processor. Added controls
match circuit operation to your voice frequencies.
+12V
R34
470K

PROCESSOR

PERFORMANCE
CURVE

10

05

INPUT (MILLIVOLTS)

MANUA

S4

Graph shows Speech Processor output voltage in
relation to input (microphone) voltage. Input
varies
over 1,C00 -to -1 range-output 2.5 -fo -1.

AGC

R32
100K

R24

C13

peak value. If the low- energy peaks are
clipped off, the remaining waveform will contain a much higher ratio of average power
to peak power.
This is quite the opposite of hi -fi audio
and this purposeful clipping does distort the
speech so that it doesn't sound exactly like
the original. However, it is possible to secure
a worthwhile increase in modulation power
without sacrificing intelligibility. As much as
20 db of clipping can be used without loss
of intelligibility, although some naturalness
is lost. A clipping level of 20 db simply
means a 10 -volt peak speech waveform is
clipped to 1 volt.
Speech clipping introduces the same high order harmonics as does overmodulation
and therefore some form of filtering must be
used after clipping and before modulation,
otherwise, look out for the FCC.
The Speech Processor combines each of
these methods of improving talk power in
one easy to build package. The processor is
simply connected between the microphone
and the microphone -input jack of the present
CB or amateur rig. Almost 40 db of speech
AGC is available to insure full modulation
from lip to arm length. And from no-clipping to 20 db of clipping is available with
the turn of a knob. Both high- frequency and
Schematic diagram /oses much of its complexity if
you compare if fo the block diagram at the top of
opposite page. Power supply is on the next page.
CB

.IMF

CLIPPER

R20

TREBL_
CUT

MARCH -APRIL. 1967

100MF

D7

R33

D6 +

1MEG
AGC

RATE

S

R35
25K
MANUAL
GAIN

1K

+

C12

TMF

-

D5

R23

-

low- frequency response can be adjusted to
suit personal preference.
Circuit Action. Referring to the block
diagram, we find the output of a crystal or
dynamic microphone is amplified by the pre amp. The gain of the preamp (Q1) can be
hi or to depending on whether part of its

emitter resistance is bypassed or not through
SI. (See schematic.) The output of the
preamp goes to the bass -cut control (R6)
where the lower-frequency response can be
narrowed from 120 Hz to 500 Hz (cps).
The signal proceeds to the high-level amplifier which uses a television video-output transistor (Q2) to provide 150 -volt peak -to -peak
capability. At first glance this seems like an
uncommonly large voltage swing but it must
be remembered the Speech Processor is capable of 40-db audio AGC. This means the
input signal can change in amplitude by
1000 times with hardly any change in the
output. So, stated another way, to have 40db audio AGC means 40 -db extra gain to
throw away with large signal conditions.
Diode Attenuator. The device that
throws away that 40-db gain when not required is the next stage, a diode attenuator.
In the simplified partial schematic the signal
passes through a high -value resistor to the
junction of two diodes. If the diodes are
hardly conducting (Re large) little attenuation occurs because the effective "impedance of the diodes is large. But as diode
current increases this effective impedance
decreases and the signal is attenuated more
as more and more current flows. In the
Speech Processor Re is replaced with a tran51

(DA

SPEECH PROCESSOR

sistor (Q5-the DC amplifier in the block
diagram) which amplifies the rectified and
filtered output of the emitter -follower (Q4).
More on this later.
After the signal has been reduced to the
required level it goes to another voltage amplifier (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
is rectified by two more diodes,
(D5, D6) and filtered so the AGC stage responds to average (not instantaneous) voice
levels. Following the filter is the DC ampli-

-it

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 almost cut off and very little current flows
through the diodes. This increases their effective 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 lowering their effective impedance. Now this
large signal entering the diode attenuator is
greatly reduced in level. So the average output level of the Speech Processor going on

(4)1N207
D8

12aV

4
EVAC

C16

500MF

N.C.

Power supply circuit diagram can fool you. It looks like a normal transistor power supply but voltage from collector of Q6 is 150 volts. Unit can be hooked to mobile rig if you can get 150 volts somewhere.

,,,.,,,
SPEECH PROCESSOR PARTS LIST

,.:.,,I,IIII111111,11111111111111111111111111111,1111111111111111,1111IIIIIIIIII.III1111111111111111$11111111011111011111g

Cl,

C10- ,02 -mf,

150 -volt disc capacitor
150-volt disc capacitor
C3, CI1, C12
-mf, 25 -volt electrolytic capacitor
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
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
C9,

C2- .005 -mf,

Cl6-

52

-5

R9- 22,000 -ohm, 1/2 -watt resistor
RIO, R12, R24- 1,000 -ohm, 1/2 -watt resistor
Rl
47,000-ohm, 1/2 -watt resistor
RI 4-2,200,000-ohm, 1/2 -watt resistor
R8,

1-

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)
D.p.s.t. slide switch
125 -volt, 15 -ma secondary, power transformer (Stancor 8415, Knight 612410 or
equiv.)
1
x 4 x 5 -in. utility cabinet-see text (Bud
AU1028 or equiv.)
Misc.-Pilot light assembly (optional) perforated phenolic board, machine screws, nuts,
knobs, line cord and AC plug, wire, solder,
RI

53T1-

-3

etc.

Estimated cost: $22.00
Construction time: 6 hours

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 undesirable, low- energy speech peaks. From
here the signal goes to the treble cut control (R21) which removes the speech-frequency 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 modulation 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 perforated- phenolic circuit board, the power

INPUT

This simplified partial schematic of diode attenuator uses some part ca//outs as in main schematic diagram. Voltage across diodes is controlled by Re.

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 controls 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 follower and DC amp) should be approximately half that measured between ground and
supply -voltage point. If any stage is corn-

C16

C15

Reverse side of power supply shows single transistor, Q6. Transistor socket is not really needed;
Q6 could be soldered right into circuit by leads.

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

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 finally the output level at J2 should be slightly
53

(gg

SPEECH PROCESSOR

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
test many transistors in circuit.

-to

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

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, however, 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)

HIGH
AGC
PATE

GAIN
LOW

.

AGC

MAN

MAN JAI
GAIN

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.

54

ELEMENTARY ELECTRONICS

SSB is ins
By

Len Buckwalter
KIODH /KBA4480

eliminating the nonessential, poweromponents in the AM signal, range is
sed- making efficiency much higher.

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 answer, "More efficient radio -frequency power." Put together those wishes for slim, but
booming signals and they'd all be answered
single sideband.
by SSB
This single-sideband system of radio transmission 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 highbutton shoes and, until recent years, considered too mysterious for all but commercial
communications. Today, single sideband has
been snapped up by the military, is embraced 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

A

...

MARCH-APRIL, 1967

microphone is strengthened in the audio amplifier, then is applied to the RF amplifier
(in the transmitter) where it meets the steady
carrier.
At this common meeting point, the modulator, audio voltages aid or oppose the carrier during modulation with the result shown.
It's a convenient picture that provides a reassuring explanation of what happens during
amplitude modulation. If the audio signal is
carrier
1 kHz (kc) (a high -pitched tone) then
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

RF

AMPLIFIER

STEADY RF
CARRIER

AMPLITUDE CHANGE
DUE TO AUDIO

1111111111i11111111111111

IIIIIIT11111111I1 II

1

1111111

I

11111111

t
(MIC

LJ"

AUDIO
AMP

Conventional picture of AM signal shows
Fig.
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 appears. It bears not the least trace of modulation! 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
UPPER

SIDEBAND

601 kHz

Typical SSB rig (this is an E/CO Ham transmitter) incorporates Mode switch to enable
operator to select CW, AM, or SSB operation at
will. Finger points to knob labeled "Carrier

Bal

RF

AMPLIFIER

CARRIER

(600 kHz)

which serves as fine- tuning adjustment

of modulator stage to eliminate

RF

carrier.

600 kHz

AUDIO
AMP

AINFAVAIVAIII/
VARYAVAIRV

(1kHz)

LOWER SIDEBAND

599 kHz

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.

sidebands deserve close inspection.
If an audio tone reaches up to 3 kHz it
When the audio tone (1 kHz) combined generates
an upper sideband on 603 kHz
with the carrier (600 kHz) in the transmitter,
(3 +600). Too, there's a mirror-image apa mixing process occurred in the RF amplipearing at 597
fier. As audio and radio frequencies beat intermediate kHz, the lower sideband. The
lines in Fig. 3 indicate the
against each other, they formed carrier -plus- product
of other audio tones. One precaution
audio and carrier -minus -audio frequencies.
when interpreting the image is this: sidebands
That creates the two sidebands, an upper one are
not in themselves audio tones. They are
at 601 kHz, a lower sideband on 599 kHz.
RF signals whose frequencies are determined
This may also be recognized as the hetero- by
the original audio. RF remains the medidyne process, where mixing signals add and
um which carries signals, via the antenna,
subtract. Thus sidebands are always spaced out
"over the air."
from the carrier by a frequency a number
If upper and lower sidebands repeat the
of Hz or kHz determined by the audio signal. same intelligence,
why transmit both? There
Modulate with voice or music and sidebands is one
good reason. On arriving at the receivspring further from the carrier as tones grow
higher in frequency
move in close to the
CARRIER
carrier for low -pitch sounds. Again, it's due
LOWER
to the frequency-mixing process.
UPPER
SIDEBAND
SIDEBAND
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
,SII
accepts a group of close 598
599
600
spaced frequencies -we pick up sidebands 597
601
602
603
just above and below 600. Each of those
DIAL
FREQUENCY
POINTER
sidebands represents the whole band of
modulating frequencies that might occur dur- Fig. 3. Some idea of conventional AM's spectrumwasting properties is evident in this diagram.
ing a voice transmission.
Note
that a 3 kHz signal fills an area fully 6 kHz wide.

-or

Iil,

-it

t

56

ELEMENTARY ELECTRONICS

-at

most a few watts. Once sidebands
one
are produced, the carrier will be rejected before it gulps RF watts further along in highlevel 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 connection. Both amplifier tubes commence to conduct. Since the output transformer is split by
a centertap, two magnetic fields are created.

er, power from sidebands add, so two are better 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 effectively halve the signal band width -and almost double available space in the radio spectrum. As we'll see, this is one significant
advantage of single sideband. There's a second 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
SIGNAL APPLIED
IN PARALLEL

=

SIGNAL
OUTPUT

UPPER SIDEBAND

LOWER

SIDEBAND

NO

+

50 WATTS

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
mere 100
information whatever. Balance of power
split between upper and lower sidebands.
watts

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.

Fig. 4 illustrates how a regular 300-watt AM
transmitter divides its power: the carrier contains 200 watts, while each sideband has 50.
That's a colossal waste since carriers, as
we've noted, contain no modulation. Total
a mere
two sidebands
useful power
100 watts, or one -third the carrier level.
If a carrier spills two- thirds of the transmitter power down the drain, why is it produced 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 uneven, 3 -way split. This underlies the first step
toward the single sideband transmitter. The
SSB rig generates a carrier but a negligible

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 pushpull 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
(Turn page)
cancel.

-a

-is

-in

-is

BALANCED
MODULATOR

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.

AUDIO INPUT

TRANSFORMER

-

RF INPUT
TRANSFORMER

OUTPUT

USI

ILSB

J

,

CANCELLED
CARRIER

OUTPUT
TRANSFORMER

AUDIO APPLIED
IN PUSH

-PULL
RF APPLIED
IN PARALLEL

MARCH -APRIL, 1967

57

SSB IS IN!
4,011.1 N

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 positive, 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 negative.
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 envelope 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 suppressed carrier.
Eliminate One Sideband. A system for
slicing off a sideband utilizes the crystal
filter (see Fig. 7). The crystal forms an extremely selective tuned circuit just a few

-

601
OUTPUT

DOUBLE SIDEBAND SIGNAL

(FROM BAL,MODULATOR)0

1.11
CRYSTAL

SSB SIGNAL
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 mechanical filter. It is a series of mechanically
resonant metal disks, as shown in Fig. 8.
58

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 mechanical movement (via an electromagnetic
coil and rod). This spurs the disks into action. Since resonant motion can occur only
over an extremely narrow range of frequencies, 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 techniques. We've been describing the filter system 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 produced by a type of push -pull amplifier.
There's also a "bridge" balanced modulator,
seen in Fig. 9. Again, there are two inputsone 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

DOUBLE

AUDIO IN

SIDEBAND
OUTPUT

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 generation. It's frequency. For a sideband filter

RF CARRIER IN

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 bottom, 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 current flows). This upset in the bridge enables
an
RF voltage to develop at the output
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 bandwidth; 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
boosted to desired output
useless carrier
wattage. But there are further steps before
that efficient signal can ride off an antenna.

-at

SSB transmitter.

In Fig. 10 there is a
transmitter which ina
of
block diagram
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
The Transmitter.

-is

2ND

BALANCED
MODULATOR
LSB

1ST

LSB

USB

CARRIER
OSCILLATOR
SIDEBAND
SELECTOR
SWITCH

1

MIXER
1

S

;

+

\\i

MIXER

3800- 4000 kHz

LINEAR
AMP

_TNT

- - - - --

455 kHz

UPPER

II

LOWER

-

-to

operate with high
crystal or mechanical
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 28mHz range.
Conventional transmitters increase frequency with multiplier stages. An RF amplifier tube is strongly driven by an input signal
until it produces distortion in the form of
harmonics, or frequency multiples. That approach works well in regular AM transmitters since only the RF carrier signal is
distorted. This doesn't matter since it bears
no intelligence during the frequency- multiplying step. The audio modulation is tacked
on at the final RF amplifier and thus escapes
distortion. Multipliers, however, would destroy a sideband signal. To preserve its audio
envelope, the sideband signal must be heterodyned up or down to the final operating frequency. The mixing step will appear as we
trace the simplified diagram of a complete

1

1)

MECHANICAL

455kHz
CARRIER

455
kHz

FILTER

T

OSC

COIL

VFO

3345-

AUDIO

3545 kHz

8+
TUNING

transmitters where audio is
Fig. 10. Block diagram of a basic SSB transmitter. Unlike conventional AM
replace multipliers in circuit.
therefore
Mixers
early.
comparatively
audio
insert
SSB
rigs
final,
the
at
injected
MARCH- APRIL, 1967

59

(/ssB

IS IN!

oscillator which generates a low -level RF
signal at 455 kHz
popular frequency
since it can use the IF transformers manufactured for standard AM receivers. Found
in this stage is the sideband switch. By
selecting either of two capacitors, oscillator 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 modulator which receives carrier and audio signals.
As already described (Fig. 6), its output is a
double -sideband signal with the carrier suppressed. 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 sideband. Back in the carrier oscillator, the sideband 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 mechanical filter is a lower sideband signal nominally 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 sideband signal at its control grid, and a mixing
(RF) signal on its screen. That second RF
signal arrives from the VFO (variable fre-

-a

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 circuitry 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 distortion. 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 amplifier 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 imparts little distortion to the modulated signal.
When you first see specs on a linear amplifier 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 power. 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)

-

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

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

high- current experimenter projects use 6
or 9 volts as the power source. Projects running above 9 volts usually are low- current
devices and a battery will last months and
months. Down on the other end, the verylow- 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 experimenter'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
takes but minutes to kill a buck- and -a-

-it

quarter battery.

Regulation. If you're an experimenter,
why not avoid the whole battery problem
with the Six-or -Niner regulated power supply? 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 regulation 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

changing two components, R2 and D1,
though you may also make this a dual voltage 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 powersupply filtering you'll need is built into the
Six-or- Niner. Maximum AC ripple -the AC
4 millicomponent of the output DC
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 experimenters-and things do go wrong with
experimental projects -there is full protection 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 protecting the experimental project in addition to
the power supply.
How It Works. Transistor Ql, which is in

-is

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
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 attempts 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 reduction in collector -to- emitter "resistance."
When emitter -to-collector resistance is reduced, the voltage drop across Q1 is also
reduced and the emitter voltage rises to the
rated value of the Zener diode (D1) in the

-in

PARTS LIST
500 -mf, 25 -volt electrolytic capacitor
C2- 100 -mf, 12 -volt electrolytic capacitor.

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
voltage drop of 6 volts, maximum.

IC1-

-a

See

text.

D1

-Zener

diode, 6.2 -volt (Motorola HEP103

or equiv.).
9.1

-volt (Motorola HEP104 or equiv

text.

_

Q1

-Power transistor,
or equiv.). See text.

R1-4.7-ohm,

I.

See

pnp (Motorola HEP230

-watt resistor, 10 %
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
Bridge rectifier, encapsulated (Motorola
HEP175). See text.
Misc.- Perforated phenolic hoard, push -in terminais, machine screws and nuts, wire, sol- t
der, aluminum for heat sink /mounting broc- 3

R2- Select

1

Z1-

ket, etc.

i

+i

Estimated cost: $6.99
Construction time: 2 hours

R1

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 effective resistance of Q1 increases until the voltage drop from emitter -to-collector has restored the output voltage to the rated value
of the Zener diode.
Construction. The model shown in the
photos is assembled on a section of perforated 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 installed under Cl, so it must be
e
95V mounted before CI is sol01
-_
dered into place.

117
VAC

C2

o
+

100MF

Z1

*

SEE TEXT

COMMON

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.
62

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 slightly 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 reduced 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

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
DC- output
mark; the (+) and (
the
tab terminals are similarly marked. Transformer 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 medium or high -power transistor -use the lowest 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.
t1

Only the basic power supply
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 insulated from the cabinet to prevent possible short circuits to
the experimental equipment.

Rl

Dl

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

MARCH- APRIL, 1967

SPACE -AGE

SHOWCASE
By Ron Mitchefi
The New York World's Fair is only a memory 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

With lunch in hand and eagerness in their faces,
school children throng Hall of Science Museum.
Below, science enthusiasts gaze at towering rocket.

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 window after window on the world of today
and tomorrow.

-

Even astronauts' spacesuits are available for close
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 another section of the museum. Given proper prep-

aration and orientation,
science- minded youngsters
can hardly fall to profit
from their hours at
the museum.

,

w

toomate

MARCH -APRIL, 1967

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.

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

it's nice to have a fancy transistor open) down
checker to indicate gain and leakage, you shorted. This to zero with the test leads
don't have to pass over a pile of dollars to meter- pointer voltage varies uniformly with
position, not indicated resisjust find out if that transistor is usable or tance.
It is exactly Vb /2 (half of Vb), or .75
dead. Much information on the condition of volt,
when the meter pointer is at mid -scale.
a transistor can be had using nothing more
Amplification. For the amplification test,
than a VTVM and a resistor. One simple connect
the circuit as shown, but less S1 (or
amplification test shows whether the transisthe clip lead) . Set the ohms -range selector
tor can amplify, and also reveals shorted and on
the VTVM to R x 10 ohms. This range
open transistor junctions. Another collectorpasses up to 15 milliamperes current with
to-base leakage test spots leaky and drifting
test leads shorted. The indicated resistance
transistors. These tests are used when the
transistor tester is not on hand or when a
quick test bench check of transistor condition is needed.
Those Tests. Amplification and leakage
tests use an ohms range -giving resistance
VTVM
readings well up on the scale to insure that s1
AC
the test voltage is not too low. To avoid
COMM
OHMS
calculations, resistance readings are used as
guidelines to transistor condition although
leakage currents can be calculated from an
Ohm's law formula.
Just two components-a 2.2k resistor (shown here as
Current flow in the ohms test lead of the 2000 ohms) and a s.p.s.t. switch (shown here as a
clip lead) -suffice for transistor amplification tests.
typical VTVM (for any indicated resistance
on any range) may be calculated using the
should be above 5000 ohms -near full-scale.
formula
A very much lower reading indicates a leaky
or shorted transistor. Connect the clip lead
1= Vb /(Rx Rc)
or switch SI to connect Rl to the base of
where Vb is the ohmmeter-circuit battery Ql. This supplies base
curent to the transisvoltage, Rx is the measured or indicated re- tor. The indicated
resistance should then
sistance, and Rc is the center-scale resistance drop to a value much lower
than 2000 ohms
reading of the selected ohms range.
(the value of R1). Usual values are 30
Voltage across the ohms test leads, which ohms or so for high -gain transistors
to 200
is also across the transistor under test, varies
ohms or so for low-gain transistors. If little
from Vb (usually 1.5 volts with the test leads
(Continued on page 113)
While

66

ELEMENTARY ELECTRONICS

electronics
IMAGINEERING
,.,,.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

LEAD'S

METAL
STRIP

(>.`h
SOLDER

METAL
STRIP

TERMINAL

BATTERY

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 acoustically 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 Radio -TV Control
RESISTANCE
When a vol- WORN
ELEMENT
ume, tone, or
radio
-TV
other
(-4-PORTION
GOOD
variable resistance control becomes worn and
SLIDE CONTACT
gives spotty operation that can't
VOLUME

/

be eliminated

with

control

WIRES

E

CONTROL

cleaner, try reversing the two ouiwer wiic
connections. This may put the operating
range of the control on the least -used portion that is still serviceable.

MARCH-APRIL, 1967

Look what happens when imagin -ation
and engin -eering get together!

When

Color- Coding Wires
you need

some color -coded
wires for a circuit

TAPE

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 network TV /radio coverage of our space shots
was okay for the general public, it was falling far short of the mark where I was concerned. 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 furnishing considerably more "closed circuit" information 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 communications 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 President 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 stations weren't using callsigns or announcing
their locations, using instead "tactical" identifier 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

DX
Elementary Electronics' Guide to Space Shot
POSSIBLE APOLLO LAUNCH STATIONS
20186

17655 kHz

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
7898
7919

8176
10648
10780

11514
14896
17643

18635
18660
19960
22857

Antigua Tracking, Antigua Is.
7919 kHz

AFE86

10780

AFE86

Ascension Tracking, Ascension Is.
6752 kHz
7919
10780
11407

AFE83
AFE83
AFE83
AFE83

11634
12140
20286
20454
20700

AFE83
AFE83
AFE83
AFE83
AFE83

London Tracking, England
GC127

GLK28
GAN29

Canton

I.

Panama Tracking, Panama

Cape Kennedy, Fla.
AFE70
AFE70
AFE70
AFE70
AFE70
AFE70
AFE70
AFE70
AFE70
AFE70

Perth Tracking, Australia
9200 kHz
10950

KUH50

Sydney, Australia (link to Honolulu)

Tananarive Tracking, Malagasay Rep.
7690 kHz
9863
10270

9440 kHz
13905
15870

MARCH -APRIL, 1967

11430
12275
20990

5RX98

5RY23
5RZ9

BROADCAST OPERATIONS
Aboard rescue vessels
6956 kHz
9337.5

KH9344
KJ3498

9460
13915

&

IT &T Control, Brentwood, N.Y.
14635
WFH87

7622 kHz
11035

KJ3197

WFK44

WFL51

RCA Control, Rocky Point, N.Y.
4555 kHz
7407.5
9095
9460
10620

WEO44
WEP57
WEP69

WE059
W ES50

13915
15460
15982.5
15987.5
18960

WES43
WES65
WES25
WES75
WES58

MUSIC TO CAPSULE

16440

KCC97

225.7 mHz
259.7
296.8

14585
14896
17390
18330
19960
20390
20454
20475
20700

AFE70
AFE70
AFE70
AFE70
AFE70
AFE70
AFE70
AFE70
AFE70

CAPSULE FREQUENCIES
telemetering
telemetering
voice

GODDARD SPACE CENTER
7580 kHz
7878
10615

SOME STATIONS IN SEARCH & RESCUE

NETWORKS

Kwajalein Relay
Ageless Sierra
(Marshall Is.)
Atlantic Chief Radio
Atlantic Public Affairs Lake Champlain (ship)

12212
13175.5

18335
21845

19465

13500

10165 kHz

15016 kHz

Kano Tracking, Nigeria
50V8
50V23
50V3

13580
14939

V K K4

EDT63

Honolulu Tracking, Hawaii
9212 kHz
10410

HOD72
HOD24

17682.5
20727.5

9132.5 kHz HPI
HPD2
10242.5
HPE
15925

Tracking, Phoenix Is.

10987.5 kHz KCCA

5775 kHz
7675
7833
7919
8260
10780
11634
12140
13170
13878

13527.5
20450

GDJ33
GBB33
GCI34
GCB38
GMJ38

GBL30
GIC33

Canary Tracking, Canary Is.
8119.5 kHz EAU65
13423
EDT42
13447.5

13620
13595
14890
18130.5
18580

GAD26

6970 kHz
7480
8005
9157.5
10792.5
10795
13555

50V7
50V4

Atlantic Recovery
Atlantic Surgeon
Atlantic Tribe
Atlas

Lant Leader
Lively Net Radio

Mayport Control
(Jacksonville, Fla.)
McKinley Leader
Boxer (NASA ship)
(Continued on pnon 701
69

A

COUNTDOWN
FOR DX
Continued from page 68

toring. Apparently there are very
few listeners who realize how easy it is
to eavesdrop 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
point out that most of the frequencies to
are
approximate, and some of the locations
stated as the users of tactical callsigns
are
educated guesses. Some fellows have, I understand, gone on to bigger and better things
by even obtaining QSL's from stations
en- DX'ing a Russian in
space is difficult because of
gaged in these launches -notably the
stathe language barrier and the Reds'
reluctance to
tions at Cape Kennedy and aboard
announce
the
space shots in advance. The author
even has
U.S.S. Guadalcanal.
trouble identifying Volga River boat
captains.
It seems that most of the communications
from Cape Kennedy are actually transmitted
Space Shot DX List
from the Cape via remote control from the
Continued from page 69
Manned Space Flight Center at Houston.
With each space shot the picture changes
Camera Bug (aircraft) Naha Rescue
Cape Recovery
slightly. For instance, the President has
(Ruykyu Is.)
Chisel Bolt (ship)
Norris (ship)
been heard talking to the capsule on 6709.5
Dauntless
Northlant
3 (ship)
kHz during one shot and on 9005 kHz in a
Eastlant Leader (ship) Pacific Chief
subsequent launch. Sometimes the press
Eniwetok Rescue
Pary
(Marshall Is.)
stations are shifted around from one vessel
Pine Tree
Fisher
Pistol Pete
to another (KJ3498 has been aboard the
Gemini Quad
Rescue (helicopter)
U.S.S. Wasp and the U.S.S. Guam during
Goodrich (ship)
Roamer
different shots). In any event, the frequenGuadalcanal Sick Bay Rony
(ship)
cies seem to remain fairly constant over the
Samoa Rescue
Guam Rescue
Sea Roar
various shots and the same tactical callsigns
(Mariannas Is.)
Singapore Relay
are heard regularly. The busiest channels
Gulf Stream
Southlant (ship)
Gun Train
are 6709.5, 9005, and 15088 kHz.
Star Buster
Hickory
Strike
How Good Is the Data? All of the inHouston Public Affairs Top Hand
formation in this article is based on listening
Houston Recovery
(Annapolis, Md.)
reports made during the Mercury and GemHouston Surgeon
War Chief
Ivanhoe
ini shoots. However, you can bet your bot(Norfolk, Va.) Wasp Radio (ship)
Westlant Leader (ship)
tom buck that 95% of the network will remain 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 serviced by the existing network with new frequencies 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
Who will be the first U. S. astronaut you DX?
happening.
1

1

The coming

70

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
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
energized by the line voltage, when
relay
a
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 delivers an audible signal generated by a tran-

it-

MARCH- APRIL, 1967

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 circuit quite interesting. The schematic diagram
shows the line voltage is rectified by a fullwave 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 cannot 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
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 permanent 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

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 soldering 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

B1

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

-9-volt mercury battery (Mallory TR146X

j
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 MTC2314 or equiv.)
R3 -1,000 -ohm, 1/2-watt resistor
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 terminals, wire, solder, battery holder, battery
connector, line cord, machine screws, nuts,
spacers, panel decals, etc.

Sl-

Estimated cost: 89.25
Construction time: 2 hours

SONALERT

Z2

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.

R1

R2

2000A
Sl
AC

-1
R3

1000
81

--

*9v T
S2

72

ELEMENTARY ELECTRONICS

BI

Z2

S1

5500 -ohm, 2 -watt resistor for the 8200-ohm,
this
1 -watt resistor. A convenient way to do
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-

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 terminals. The proper battery holder is a Keystone number 166. Of course this also means
that a higher DC voltage is necessary from
the rectifier. You will have to substitute a

Completed Line Failure Alarm shows adjustment potentiometer 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)

Employed in Electronics?

Are you a Veteran?

Age

Male

Occupation
Are you

a

Single

Female

Part-time

student? Full -time

Married

Home Study

Check the last school you attended: Circle schools you graduated:
Graduate School
College
High School
Grade 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...

MARCH- AFRIL, 1967

1-111.-.

73

HOME STUDY

e /e's

Guide to selected
Home -Study Courses
now being offered by

BLUEBOOK

Electronics Schools

E's in Electronics is for Educayou 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 impractical 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 nonCL:,

One of the

tion- wherever

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 forward 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 communications, plus radio -TV transmission, microwave relay, and teletype. Course contains 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.
CUT HERE

1
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ELEMENTARY ELECTRONICS, Dept. HS -1

1

505 Park Avenue, New York, N.

1
1

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Y.

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10022

1

would like to know more about the electronics home study courses described above.
interested in only the course numbers circled below.
CS. Yes!

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am

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Veti

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City

State

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(Fill in facts on reverse side)

Zip

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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 operator's test years ago would be unpleasantly surprised if we had to take it today.
Since 1950, the tests have been expanded
to cover UHF radio, radar, FM radio, television, and the use of semiconductors in communications. Each of these new fields has
added questions to the operator's tests. The
most recent addition to the tests, semiconductors, 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 relearn 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 Communications 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 included 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.
MARCH-APRIL, 1967

Generally, there two basic types of transistors. 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
A

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 center wafer being the base.
Amplifier action is as follows: barriers are
formed at the wafer junctions. These barrier 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 junction) 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.
,

75

1(g

FCC

Q&A

FEEDBACK
COUPLING

BIAS

BIAS

T2

Ti

I2

OUTPUT

INPUT
R2

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 operate at all without some forward bias on
the base emitter circuit. Too much forward
bias on the base circuit will damage the transistor. 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 transistors, by physical construction: point- contact
and junction; by wafer arrangement: pnp
and npn. The schematic symbols for transistors are shown in Fig. 2.

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

Fig. 3. Oscillator circuits will be a major part of
the examination. This basic Hartley oscillator circuit 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) semiconductors with respect to: (a) the direction of current flow when an external emf is applied:
(b) the internal resistance when a external

emf is applied.
(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 toward 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 circuit, with reference to the emitter. The internal resistance is smallest in this forward
bias direction. Therefore, for maximum internal resistance, the polarity described is
reversed. An npn transistor is exactly opposite to the pnp type.
Q What is the difference between forward
and reverse biasing of transistors?
A Forward bias is that condition of maximum 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 circuit 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 opposite polarities to maintain the same biasA

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.
Fig. 4.
Q Draw a circuit diagram of a method of
obtaining self -bias, with one battery, without
current feedback, in a common -emitter amA See

PNP

SIGNAL
INPUT

o,

Ti

J

OUTPUT

I

BIAS

A

BI

PNP

ci
SIGNAL
INPUT

g

OUTPUT

BIAS
VOLTAGE
DIVIDER

B

SIGNAL
INPUT

ii
R3

OUTPUT

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 negative feedback and reduces temperature runaway. Voltage drop across primary of T1 (from increased current
flow in collector) lowers forward bias to base input.

plifier. Explain the voltage drops in the resistors.
A See Fig. 4.
There are three basic common- emitter biasing circuits, each of which is shown in Fig.
4. Fig. 4A is comparable to a fixed -bias
vacuum -tube circuit. Here the base is forward biased by battery B1, through resistor R l which acts to limit the current in
the base circuit, since in a forward bias condition 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 divider 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 supplies degeneration and also acts to stabilize
the bias by its self-correcting action. Emitter bias resistor R3 is unbypassed, further signal degeneration is introduced here that also
helps to stabilize the circuit. Too, this resistance acts to raise the base -emitter resistance.
Q Explain the significance of each item
listed: (A) Collector-to -Base Voltage (Emitter open) -40 MAX. VOLTS (B) Collectorto- Emitter Voltage (Base to Emitter Volts 0.5v)-40 MAX. VOLTS (C) Emitter-toBase Voltage -5 VOLTS MAX. (D) Collector 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 operation 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-tobase 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 microampere leakage current called 1,,.
The third specification is the reverse
breakdown voltage across the base -emitter
circuit. From this we can judge that the input 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 current flow in the collector circuit.
Transistors are self-destroying when their
maximum ratings are exceeded, because a
77

Fig. 4C. The resistor in the emitter
circuit,
R3, is used to develop emitter bias
FCC Q & A
voltage. However, contrary to vacuum -tube
operation, transistors must be biased on, not
off. The resistor used here bucks the forward
destruct cycle is started which reinforces bias of the base circuit. Without a bypass
itself. For example, if an excessive current capacitor, its effect is to raise the input reflows in the collector circuit, the transistor sistance of the transistor by a rule-of -thumb
junction overheats. This heat causes the re- factor of approximately R X beta (gain of
sistance of the junction to decrease, which the amplifier.) A 1000 -ohm resistor would
causes the current to increase further, which raise the input resistance (if the amplifier
in turn, heats the junction more, etc.
gain was, say, 100) to 100 X 1000 or 100,Maximum dissipation is stated to be 120 000 ohms. The actual input resistance canMW. This is the real limiting factor in tran- not be raised this much, but lower resistance
sistor operation. Although the collector- values give a good approximation. A further
emitter voltage is stated to be 40 volts, and effect is to stabilize the stage gain. The dethe collector current stated to be 10 MA, generation introduced in this manner is very
the transistor cannot handle both maximum
effective in stabilizing stage gain and prevalues at the same time. This would be a venting thermal run -away.
dissipation of 400 MW. Either the volt- Q The value of the alpha cutoff frequency
age or current can be the stated maximum
of a transistor is primarily dependent upon
value, and the other must be limited to the what one factor? Does the value of alpha
value that will not cause the maximum dissi- cutoff frequency normally have any relationpation to be exceeded. For instance, if the ship to the collector -to -base voltage?
voltage is -40 volts, the maximum current A The alpha cutoff frequency of a transistor
can only be 0.120/40 or 3 milliamperes. No- is primarily dependent on the width of the
tice too that this dissipation is specified at base region of its junction and the following
room temperature in free air -this means formula is fairly accurate: alpha cutoff (in
that in normal operation if the room tem- megacycles) is equal to C /Wa, where C is
perature of the air at the transistor exceeds equal to 5 -6 for germanium npn, 1 -9 for
25 °C, the maximum dissipation must derate germanium pnp. W is equal to the width
accordingly. If a heat source such as a pow- of the base region in mils. The alpha cutoff
er resistor were located near the transistor frequency increases with increasing collector
and no ventilation provided, the transistor bias because widening of the space- charge
might be derated from 120 milliwatts to layer decreases the effective base region
possibly as little as 1 milliwatt.
width.
The seventh specification limits both the Q Why is stabilization of a transistor amstorage, that is, inactive; and operating tem- plifier usually necessary? How would a therperature to -65 °C to 100 °C. The transistor mistor be used in this respect?
will cease to function even in a derated con- A Stabilization of a transistor amplifier is
dition beyond these temperature extremes.
necessary because of variations in the tranQ Draw a circuit diagram of a common - sistor characteristics with varying temperaemitter amplifier with emitter bias. Explain tures. A thermistor can be used in the biasits operation.
(Continued on page 111)

@

A See

g

DRIVER
PNP
b

`

OPTIONAL, USE
,ONLY IF COLLECTOR
EXCEEDS BASE
+REQUIREMENT

I

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

ELEMENTARY ELECTRONICS

Paradys, S. Afr"...a
Sarawak, Mayl ly i
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

1

By

Walter

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
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 frequencies some of the rarest DX can be
found. Most 90 -meter stations broadcast primarily 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 stations 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
90 -meter band. Sierra Leone has its only

-a

MARCH -APRIL, 1967

L

r

!

¡I

G

.

k, Maylaysia
Zambia

Suva, Fiji
Tananarive, Malagasy
Gwelo, Rhodesia
Pyongyang, Korea
1
Papua
t
{

1

diwan

I

Conakry, Guinea
Kabul, Afraganistan
lagdad, Iraq
'ibul, Afghanistan
R.

Levins

SW outlet on this band. A high -powered
station (100 kw) operated by Radio Clube
de Mozambique offers the only high -powered transmissions from Africa on this band.
Mozambique is one of the last colonies in
Africa, thus making it a controversial country to verify.
Frequency

Power

(kHz)

(kw)

3250
3255
3259
3260
3270
3284
3288
3290
3295
3306
3320
3335
3335
3375
3376
3780
3925
3985
3990

20
10

20
100
10
10

30
25
100
10

50
10
10
10

50
100

50
50
50

Station & Country
Paradys, S. Africa

Liberian Bc. Corp., Liberia
R. Malaysia, Sarawak
R. Clube de Mozambique
Lusaka, Zambia
Suva, Fiji Isl.
Tananarive, Malagasy Rep.
R. Nacional, Colombia
Delhi & Bombay, India
Gwelo, Rhodesia
Pyongyang, Korea
R. Wewak Papua
Taipei, Taiwan
R.

Angola

Conakry, Guinea
R. Iran
Tokyo, Japan
R. Kabul, Afghanistan
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 Afghanistan (50 kw). Middle East stations in Iran
(Continued on page 113)
79

ARECIBO LISTENING

ce

o

a
ó
v

c
0
E
E
o

V

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 valley near the little Puerto Rican port of
Arecibo.
Operated by Cornell University and sponsored by the U.S. Advanced Research Projects Agency, the Arecibo telescope easily
qualifies as the world's biggest ear. The entire installation covers an area larger than
56 city blocks, and the antenna alone880

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 answer to this and countless other riddles. For
the Big Ear has only begun to listen.
-Ron Mitchell
ELEMENTARY ELECTRONICS

the inside story
on DETECTORS
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1T6

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00'

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-1-C35
R23

1/10

J

L-

PHASE
DISCRIMINATOR
RFC4

R26

R24

138
C34

B+
R25

R36

R22

C37

l
C27

C26

R20

R21

R34

C541

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

The next important function of a shortwave 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 demodulator when it picks out the amplitude -modulated carrier. For FM signals this important
detector stage usually is one of several types
-the most common ones are the discriminator 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
the positive or negative half of the signal is
MARCH- APRIL, 1967

7906

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. Modulation 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 applied to the carrier it will compress and expand 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 modulating signal. Since the positive and

-

81

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

DETECTORS

¡

ti.
, ,
1

1

j.
'

,
1

1
1

1

1

s,
1

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.

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

-

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. Therefore, 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). Today the adjustable crystal diode has been
germanireplaced by a miniature device
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 negativegoing signal causes a reduction in plate cur(Continued on page 85)

-a

Fig. 3. When viewed on an oscilloscope the RF s'gnal
would appear as above-depending on the sweep frequency. High repetition rate at left; low at right.
RF CARRIER

0

Fig. 5. Series -diode detector allows one half of
modulated -carrier signal to flow through headphones
while presenting high impedance to other half.

AF

RF

FILTER

ENVELOPE
Fig. 4. Gap occurs in RF carrier only when modulation
exceeds 100 %. Such operation distorts audio information and generates harmonics and other interference.

negative peaks are almost mirror images of
each other, and equal in amplitude but of
opposing polarity, one of them must be eliminated 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 amplifier. 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,
82

Cl

SHUNT
DIODE

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

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.

Fig.

ELEMENTARY ELECTRONICS

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TUBE
CHARACTERISTIC
CURVE
BIAS
POINT

IFMTRAN

PLATE CURRENT SATURATION

LINEAR
PORTION

CUTOFF

AF

HEAD-

PLATE
CURRENT

C1

PHONES

C3

C
AVC

R3

c
RF
SIGNAL

RF

C4

I

SIGNAL

GRID VOLTAGE

I

- 0+

BIAS
VOLTAGE

)

PLATE
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 signal at grid increases plate current and decreases plate voltage). Again, a capacitor
(C) across the output filters out the remaining RF component. The average plate current 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 detector is in series with the secondary winding
of the IF transformer, R1 and R2. Capacitors Cl and C2 in conjunction with R1 form
a low -pass filter which passes the AF signal
POSITIVE

NO- SIGNAL
PLATE VOLTAGE
PLATE -CURRENT CUTOFF

PLATE - CURRENT
SATURATION
AF

ENVELOPE

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 developed across R1 and R2, resulting from
rectification of the IF signal. (Arrows indicate 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-

GOING

SIGNAL
RESULTING
OUTPUT SIGNAL

ACTUAL SIGNAL

NEGATIVE GOING
SIGNAL

Fig. 9. Because tube does not cutoff sharply at the
bias point some distortion is introduced in signal
that rides between the bias point and current cutoff.
MARCH -APRIL, 1967

C2

11. Circuit of semiconductor -diode defector is
just about identical with that of vacuum -tube circuit.
o
^I ^ +e. t.^ . ;d ^. 6te h ;ny frnm detector DC.

Fig.

r

85

DETECTORS
fier stages. A small negative voltage is applied 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 negative signal swings. A positive DC voltage is
also developed across CI which opposes the
negative forward bias applied to the transistor bases, causing the receiver gain to
drop. Hence, the receiver gain is controlled
by signal level.

VOLUME
CONTROL

)

T

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 is equal to the sum of the
voltage charges across C and C2, each of
which charges to the peak value of the IF
signal. The AF signal is also developed
1

I

86

Fig. 14. Full -wave voltage doubler circuit raises signol level to audio amplifier input but not enough to
eliminate an audio stage; actual cost is increased.

RF

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 impedance of a grid -leak detector is not as high
as that of the plate detector since some grid
current flows, loading down the resonant input 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 circuit, 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, resulting in possible blocking of the tube, is prevented by grid leak R1 which is the load for
the grid -to- cathode shunt rectifier. Bias voltELEMENTARY ELECTRONICS

detector, used mainly in the hi-fi AM tuners
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

-it
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.

9

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 received a negative grid -bias voltage develops
across R1 (grid to cathode) and plate current 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 combination of a diode detector and an AF amplifier as Fig. 16 suggests. The grid sees and
amplifies the output of the shunt-diode detector found inside the tube by the cathode to -grid electron glow.
Infinite- Impedance Detector. The circuit 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 determines 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

.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 compared 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 electronic oscillator around the DeForest tube.
The courts were busy for a long time trying
to determine which came first, the chicken
(Turn page)
or the egg.
87

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 selfquenched-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 sometimes 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-

eDETECTORS

The barristers argued about the regeneration 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 circuit (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 detector should oscillate. When receiving AM
signals, the detector should not oscillate.
Maximum gain (sensitivity) and selectivity
are obtained just below the threshold of oscillation. Therefore, receivers with regenerative detectors are equipped with a regeneration 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)

AUDIO
TRANSFORMER

L3

AF

RF

/

REGENERATION
CONTROL

RI

LI

AUDIO

TRANSFORMER

AF

RF

REGENERATION
CONTROL

88

Fig. 20. Regenerative detector
uses separate feedback winding
(L3). Feedback is controlled
by varying capacitance of C3changing circuit impedance for RF
through L3, C3 and triode. Grid
leak R1 -C1 develop grid bias as in
a grid -leak detector circuit.

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

-

divider across B).

ELEMENTARY ELECTRONICS

RF

I
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

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 output will vary and the FM signal will be demodulated. 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

CONTROL

DETECTOR

Fig. 23. With the exception of added
quench oscillator and grid resistor connection, circuit of superregenerative detector
is identical to the circuit given in Fig. 20.

no

RFC

V1

Fig. 24. Self- quenching circuit is
preferred for high -frequency receivers. The
regeneration control bypasses RF through
variable capacitance shunting from L3.

AF

RF

FILTER
RF

AUDIO.
TRAN

QUENCH

SIGNAL

e

RF FILTER

V2

AUDIO

L3

QUENCH

TRANS.

GRID LEAK

OSCILLATOR

L1
L

RF

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 background hash (noise) when no signal is being
received. This detector will also cause interference 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 constant amplitude to the detector. Thus, if fed
an AM signal, the AM (variation in amplitude) 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 receiver with a 455kHz IF, for example, if
the receiver is detuned so that the IF produced 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 freMARCH -APRIL, 1967

REGENERATION
CONTROL

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 preceding IF stage (limiter) is fed inductively
into the secondary of T and through a capacitor (C) to the center tap of the second89

I@

DETECTORS

ary. When T is tuned to the carrier frequency 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. Therefore, 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.

--1

RFC

(r,

'000O'

-

Ratio Detector. While this circuit is used
widely in FM communications receivers, the
ratio detector (shown in Fig. 27) is commonly used in FM broadcast tuners and receivers 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 effective 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 current is cut off and the control grid (No. 1)
loses control. If slightly positive, plate current 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

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.

AF
C4

D2
GATED

-

8EAM
T

AF

IF

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.

TRA

SHARP-CUTOFF
PENTODE

IF

IF
TRAN

90

Iii'

R4

AF

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 suppressor grid has on plate -current flow.

ELEMENTARY ELECTRONICS

TI

IE

IF
TRANS

Fig. 30. Bradley

detector was never
popular in entertainment receivers. Again,
o hard -fo -align circuit
-increases production
cost and loses
in many
cases, never gets a
chance in mass-

OSCILLATOR
II, T2

R6

popularity or,

-'VVV-110
BIAS
NETWORK

C6

AF

produced circuitry.
R5

vvvv
DETECTOR
AF AMP

AM

SSB

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.

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.

(the carrier frequency as translated to the
IF within the receiver). When a signal at
the IF center frequency is fed through T
-C is shock
to the control grid (No. 1)
excited at its resonant frequency and generates a signal voltage at that frequency.
When the incoming signal is deviated in frequency (FM) the phase relationship be-

-L

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 similar 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 Ordinarily, 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 receiver. 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 incoming 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
tapped down on the coil
of the tuned circuit. Using tap
reduces loading on tuned circuit
increasing selectivity.
has base

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 frequency varies. Therefore, the BFO is usually
made variable in order to offset these frequency changes.
Product Detectors. More sophisticated
SSB detectors are used in professional and
amateur communications receivers and trans92

-

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
(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.

Electronic Is Better. What's the advantage in an electronic metronome? Well
there's tone quality and long-term convenience, to name just two. The ordinary
arm- buster used by musical students requires
always
They
project with experimenters.
it's five -to -one the spring will
work, and are great for elementary school winding, and
before the last note of the
long
out
run
other
Science Fairs, primarily because while
And the usual tack Rhapsody.
science fair projects just sit and stare at the Hungarian
arm buster is often
-wound
spring
of
the
tack
tic
-tic.
parents, a metronome at least will ticclown who interthe
than
But an electronic tic -tic can be more than more annoying note to comment on the
fifth
every
rupts
a child's toy. Dress it up in a fancy box,
abilities. On the other hand, the
select component values that get the tics to musician's
shown in the schematic diagram
metronome
vary continuously through the 40 to 208
soft thock -thock sound, similar
a
produces
nice,
a
got
beat-per- minute range, and you've
to a muted tom -tom drum,
characteristics
in
and thoughtful, gift for a musical friend.
to play along with.
beat
pleasant
very
a
and
speaker
And your cost (less the box,
circuit shown could
metronome
basic
The
battery) comes to less than $3.50.
cost you under $3.50- providing you use
R2
of
only the components listed in the Parts List
QE
and shop carefully. Do not attempt to improve performance by using industrial grade
components as a tantalum capacitor is not
going to improve anything over the lowestpriced Cl specified. Same thing with transistors Q1 and Q2. With the specified transistors the output sound is a soft thockthock; using better or less expensive transistors will result in the usually annoying
electronic metronome tic -tic sound-like
someone driving a nail into your ear. HowWhole circuit is contained on a scrap of perforated
ever, if you like tic -tic substitute the least
phenolic circuit board. Only other component on the
Cl
board is C1- that's on the other side. If you like
expensive audio -grade transistors you can
Q1
can be mounted on this side of board alongside
get (like 20 for a dollar) ; and while you can
Because they cost next -to- nothing

(use

junk -box components), and can be assembled by a five -year -old, electronic metronomes have always been a favorite one -night

and Q2. Control

R1

is

mounted on side of cabinet.

93
MARCH -APRIL, 1967

®Ag

R1

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 inch x 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
1

1

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 (Lafayette 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:
hour
1

COLLECTOR LEAD Q2

R2

Cl

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 enclosure shown. The cabinet is purchased
complete with speaker, volume control and
wire. Remove the existing speaker -level control 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
94

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 metronome- indicate the correct timing on the
cardboard.
ELEMENTARY ELECTRONICS

c

r

TENNA-Bil

you mount the flashing light
You'll be outstanding in a parking lot whether
lamp on the dashboard.
-mounted
box
on the tip of your antenna or place the
by Steve Karlsen

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 TennaBlitz 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 cabinet to keep costs down, and we'll guarantee a
blinking light will attract almost as much attention 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 applied, 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

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
ci

R1

470a

2MF
R2

Q1

I1

Qi
e

RED
DOT

.

is
Schematic diagram for the Tenna -Blitz reveals what
known as a blocking oscillator. Resistor R1 (M conjunction with capacitor Cl) controls length of flash.

PARTS LIST
Z4 battery (RCA VS068 or equiv.)
-mf, 6 -volt electrolytic capacitor (see
C1
text)
-volt, 60-ma panel lamp (Type 48 or 49)
11
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, machine screws and nuts, scrap aluminum, etc.
Estimated cost: $2.00
Construction time: 1 hour

B1-6 -volt

-2
-2

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

illgaMa-

01

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

GROUND LUG

MOUNTING BRACKET

All

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

C1

R3

Only three components appear on bottom of perfboard: capacitor C and resistors R2 and R3. Collector lead from Q2 (see call -out) runs to one side of
lamp 11; screw holding ground lug in place also supports perf -board mounting bracket (see photo at left).
1

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 increase 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 tomorrow.
Completed unit fits neatly into suggested chassis
box, although switch S1 should ideally be
of the miniature variety to avoid any possibility of crowding. Note holder for B1.
BI

II

All

wired up and ready to go, completed unit
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 /2 -in. rubber grommet.
has but one

SI

96

01

02

1

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

W= E2 /R or W = 12 R,
respectively. If the load resistance is not
known, it can first be determined by measuring it with an ohmmeter or bridge.
Resistance Load. When the load in an
AC circuit is resistive (lamp, heating element, tube filament, etc.) , the same technique 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
W= E1= E2 /R =12R
as before. To measure true power, a
watts,
current
E representing volts, 1 representing
wattmeter is required. Its indication will
in amperes, and R representing load resistdiffer from the calculated volt- amperes (apance in ohms.
parent power) by an amount determined by
a
DC
in
load
a
by
The power consumed
of the load. The power
circuit can be determined by measuring the the power factor
load is less than unity.
an
inductive
of
factor
and
voltmeter
DC
voltage and current with a
An electrodynamometer is similar in conand DC ammeter as shown in Fig. 1, and
to a voltmeter or ammeter except
struction
watts.
to
then multiplying the meter readings
that it employs an electromagnet (field coils)
W = El
instead of a permanent magnet, as illustrated
power
When the load resistance is known,
in Fig. 5. The rotating coil, to which the
measurby
determined
be
can
consumption
indicating pointer is attached, is the voltage
the
ing either the voltage across the load or
coil and is connected across the line through
3,
and
2
Figs.
in
shown
it
current through as
a series resistor. The field coils are the curand computing

you know what's what with watts?
Power in watts, kilowatts and megawatts makes the industrial giant move
toasts your bread, dries your clothes, heats
your house, brightens that dark corner with
light and is right there when you want recreation. It's time you learned more about this
ever-faithful servant.
Electric power consumption is expressed
in watts. One watt is consumed by a oneohm load to which one volt is applied, causing one ampere of current to flow. Power in
watts is equal to
Do

-it

MARCH-APRIL, 1967

97

IV®

POWER IN WATTS

AMMETER

LOAD

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 indicates the true power consumption of the
load, even if power factor is not 100 %.
SERIES

RESISTANCE

(MULTIPLIER)

Fig. 1. Voltmeter can be across source or load since
IR drop across ammeter is low; as is voltmeter
current.
CURRENT
FROM

CURRENT

LINE

PIVOT

COIL

CO L

TO
LOAD

SHUNT

Fig. 5. E ectrodynamometer-type wattmeter connects
to both s'des of line and to load- computes E X I.

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

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 wattmeter, 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

LOA

LOAD

VOLTAGE
COMPENSATING
COIL

Fig. 4. This connection for AC wattage measurement
is accurate only when the load is a pure resistance.

ROTATING DISC

CURRENT

COIL

CURRENT COIL

DRIVE SHAFT TO
MECH. COUNTER.

MECHANICAL COUNTER

Fig. 6. Watt -hour meter is variable -speed motor and
a revolution counter -computes wattage against time.

Multimeter -sized instrument that measures wattage,

current and voltage is made by Simpson -Model 390.
98

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
S

MIC

WEIGHTING
NETWORK

AMP

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 measuring voltage across the load, it must be calibrated 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

AMP
ATTENUATOR

ATTENUATOR

1*

AUDIO

ril

WEIGHTING
NETWORK

DC

AMP

°

AUDIO (AC)

AMMETER

AUDIO
GENERATOR

CALIBRATED
METER

Fig. 7. Block diagram of the General Radio 759 -13
a
sound-level meter shows the instrument is quite
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 expressed in watts, dbm or dbw. The standard
reference levels are 0 dbm, representing one
milliwatt (0.001 watt), and 0 dbw, representing 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

LOAD
RESISTOR

AMPUF1ER

Fig. 9. This setup is seldom used-that in Fig. 8
are a
is preferred since audio-frequency voltmeters
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
W = E2 /R.
a
not, lower the input signal level until the
across
volts
4
is
For example, if there
output signal is a sine wave and then recom16 -ohm load, the power consumed by the
pute the undistorted (relatively) output
X
divided
4
4
load would be one watt since
power -RMS power.
by 16 equals one.

MARCH -APRIL, 1967

99

@AD

POWER IN WATTS

PEAK

NP

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. Therefore, 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 capacitor (2 mf) in series with the AC voltmeter, 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 calibrated 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

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 multiplier, 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

VARIABLE

RATIO
TRANSFORMER
LOSS ADJUSTING
NETWORK

METER
ULTIPLIER

Fig. 11. Variable ratio tran former is input of
block diagram of General Radio 583 -A power meter.
100

Relative measurements of RF power can be mode with
Olson's low -cost C8 -67 SWR and Field Strenath Meter_
ELEMENTARY ELECTRONICS

with extreme inefficiency. It's called radio.
When you tune in a station radiating 50 kilowatts of energy, some of it is consumed by
your receiver-perhaps a fraction of a billionth 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 delivering 3 watts into the antenna, the ERP
(Effective Radiated Power) is 30 watts. At

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.

Two -unit instrument consists of Standing Wave Bridge

(Model SWB), Bridge Indicator Unit (Model B/U).
indicate up to 1,000 watts at frequencies between 1.8.225 MHz without added loss.
These Ameco units

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 power 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 concerned, is the power consumed by the final
RF ctage of the transmitter (not including
MARCH -APRIL, 1967

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 determined 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 current 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 breaking 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, input 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.

101

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

POWER IN WATTS

rent, as shown in Fig. 14, and then multiplying.the indicated voltage and current.
Input power, whether to a tube or transistor, is equal to the voltage times the current 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.

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.
TANK CIRCUIT

TO ANTENNA

VIA RELAY OR
SWITCH
RFC

RF POWER

AMPLIFIER

CW (RF)

INPUT FROM
OSCILLATOR

X2
MILLAMMETER

+
+

X3

` --

%

MEASURE PLATE
CURRENT HERE

- SCREEN

+I VOLTMETER

T-R

SWITCH

MEASURE CATHODE
CURRENT HERE

AUDIO OUT
MODULATION /OUTPUT
TRANSFORMER

I

MEASURE PLATE
VOLTAGE HERE

MODULATOR

8 +.

Fig. 13. Transmitter input -power measurement method varies with the circuit used in the individual transmitter. Usually meter is at some distance from plate or cathode circuit -shunt is in actual current path.

r
TANK
CIRCUIT

This simple instrument is calibrated with
the circuit in Fig. 17. Simply plot a graph
(or make a table) for translating the meter

-- iMILLIAMMETER
MEASURE
COLLECTOR CURRENT
HERE

VOLTMETER

"1-.©_-_

1

MODULATED
MEASURE

COLLECTOR-EMITTER
VOLTAGE

Fig.

14.

HERE

Transmitter

has power measured

using transistor in output
similar to method in Fig. 13.

RF Output Power. The relative RF output power of a transmitter can be determined by using a filament -type (incandescent) lamp as a dummy load or phantom
antenna, connected directly across the transmitter output. In the case of a CB set, a No.
47 pilot lamp is often used. The lamp has a

102

Fig. 15. Dummy load for low -power transmitter uses
three pilot lamps. Current flow changes resistance.
ELEMENTARY ELECTRONICS

in water and the increase in water temperature is measured. Or, the sensing element of
a thermometer (Fig. 19) can be strapped
to a dummy load and the increase in temperature noted.

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

COAX

CONNECTOR

1,\\
\\

AC

TO RF POWER

MILLIAMMETER
AC

LINE

METER
VIA COAX
JUMPER

Fig. 19. Industrial thermometer measures heat rise
in dummy load
practical way since heat is power.

-a

VOLTMETER

r
115

24V

TRANSFORMER

Fig. 17. Simple circuit measures power used to calibrate RF-power meter shown in Fig. 16 above.

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 transmitter 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

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 thermistor whose resistance drops, unbalancing
the bridge. Power is then determined by rebalancing the bridge or translating the
amount of indicated unbalance into watts.
COAX

PLUG

GALVANOMETER

RF
INPUT

MILLI AMMETER

PRECISION
RESISTORS

BRIDGE

BALANCE
ADJ.

= 12.5.
Fig. 20. Simplified circuit of bridge -type power
meter. Milliammeter, potentiometer not always used.

COAX
CONNECTOR

50A
INPUT

RF

11

DUMMY LOAD

(THREE

150A

CARBON

RESISTORS)

RF

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.

AMMETER

Fig. 18. Dummy load with series RF ammeter measures
current through constant load or resistance (Fig. 3).

COAX
CONNECTOR
DC

RF

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
MARCH- APRIL, 1967

MILLI -

VOLTMETER

INPUT

DUMMY
LOAD

THERMOCOUPLE
JUNCTION

Fig. 21. Heat in dummy load generates voltage in a
thermocouple junctión- indicating wattage on meter.
103

POWER IN WATTS

GM

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

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 forward 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.

THERMOCOUPLE
JUNCTION

COAX
CONNECTOR

RFC

MILLI-

RF
INPUT

VOLTMETER

RFC

TRANSCEIVER

/SWR METER
COAX CABLE
JUMPER

/

/DUMMY

RF FILTER

LOAD

Fig. 22. Two RFCs and C form RF filter that is used
in many instruments to isolate RF; pass DC to meter.

Fig. 24. Connected between transmitter and antenna,
fester indicates power output and reflected power.

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

The same instrument can be used on the
bench for extended periods of troubleshooting and testing- measuring transmitter output 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 Electronics (Ford -Philco), Menlo Park, California. By setting the SWR meter to measure forward power, it will indicate transmitter output in watts.
More accurate RF wattmeters are available from Bird and Sierra (Fig. 25) which
contain an internal 50 -ohm dummy load.

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 combined 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
120

Ir

n
1H4G

I

CALIBRATION

I

SHUNT

RF,

12rí

INPUT

MILLI-

52n

DUMMY
LOAD

AMMETER
RFC

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 connected, 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 device 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
RF
INPUT

CONNECTOR
R1

- RANGE
SHUNT

HIGH

DIODE

R3
C2

R4

MILLI -

RANGE
SWITCH

AMMETER

COAX

.

CONNECTOR

CALIBRATION

Cl

RANGE
SWITCH

RF
INPUT

LOAD

SHUNT

measured with an oscilloscope when modulating 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 RFsignal 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.

C2

RF

Fig. 26, 27. At top, R4 is shunted across milliammeter for high -power range. RF voltage divider
(R1, R2), range switch multipliers measure voltage.

:DUMMY
LOAD

INPUT

J

COAX
CONNECTOR
LOAD

DUMMY
LOAD

LINK
RF

FROM

TRANSMITTER

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 produced 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

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 important (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

AF GENERATORS

OR TRANSCEIVER

Fig. 29. Two AF generators feed signals into modulator of rig. Dummy load is a necessity for all extended periods of transmitter testing-particularly with high-powered rigs that can easily span the nation.
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 measured 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 increase will be less.
The RF-power output of an FM transmitter, on the other hand, does not increase
under modulation. Instead, the carrier frequency 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 deviation meter which indicates frequency deviation, not power.
RF- Power -Meter Connections. In all of
RF power measuring devices, coaxial connectors 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 instruments are also equipped with SO -239 receptacles (some use an N or UHF type connector). Connections to the transmitter output 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 CB24 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 (50ohm) 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 dealing 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 intermittently 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 microsecond 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 extremely 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 average power may be less than 100 milliwatts
but occasional sound peaks might feed several watts into the speaker system.
RMS power is measured using the techniques described previously. Peak power can
be determined by measuring the peak voltage 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 resistance 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 average 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 kilowatthours of power (120 watts for 10 hours) .
The efficiency of electronic equipment is
rising, thanks to transistors. The power consumption 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

RADIO

wrIc

LITERATURE
* Starred items indicate advertisers in this issue. Consult
their ads for additional in-

formation and specifications.

LIBRARY
C8-BUSINESS

RADIO
SHORTWAVE RADIO

KITS

*42. Here's

catalog containing a wide assortment of
115. Get the fully story on Poly - electronic kits. You'll find something
Ironics Laboratories latest CB entry for any interest, any budget. And
-Carry-Comm. Full 5-watts, great Heath Co. will happily send you a
for mobile, base or portable use. copy.
Works on 12 VDC or 115 AC.
*44. EICO's new 48 -page 2 -color
*93. Heath Co. has a new 23 -chan- pocket-size short form catalog is just
nel all- transistor 5 -watt CB rig at the off the press. Over 250 products: Ham
lowest cost on the market, plus a full radio, CB, hi -fi -in kit and wired
line of CB gear. See their new 10- form -are illustrated. Also, discover
band AM/FM /Shortwave portable EICO's new experimenter kit line.
and line of shortwave radios.
ELECTRONIC PRODUCTS
101. If it's a CB product, chances
are International Crystal has it listed 66. Try instant lettering to mark
kit
their
colorful
catalog.
Whether
in
control panels and component parts.
or wired, accessory or test gear, this Datak's booklets and sample show
CB oriented company can be relied on this easy dry transfer method.
to fill the bill.
108. Get the facts on Mercury's
48. Hy-Gain's new CB antenna cata- line of test equipment kits- designed
log is packed full of useful informa- to make troubleshooting easier, fasttion and product data that every er and more profitable.
CB'er should know. Get a copy.
67. "Get the most measurement
107. Get with the mobile set with value per dollar," says Electronics
Tram's XL'100. The new Titan CB Measurements Corp. Send for their
base station, another Tram great, is catalog and find out howl
worth knowing about.
92. How about installing a transiselectronic ignition system in
111. Get the scoop on Versa - torized
current car? AEC Laboratories
Tronics' Versa -Tenna with instant your
will
mail
their brochure giving you
magnetic mounting. Antenna models specifications,
schematics.
available for CB'ers, hams and mobile
109. Seco offers a line of specialunits from 27 MHz to 1000 MHz.
ized and standard test equipment
45. Catering to 2 -way radio buffs that's ideal for the home experimenter
for 30 years, World Radio Labora- and pro. Get specs and prices today.
tories has a new free catalog which
includes the latest CB transceivers,
HI -FI /AUDIO
etc. Quarterly fliers chock -full of bargains are also available.
26. Always a leader, H. H. Scott
a new concept in stereo
50. Make your connection with introduces
catalogs. "At Home With
Amphenol -tune in to the latest on console
Stereo,"
decorating ideas, a
offers
CB product news with specs and pics complete explanation of the more
on new gear. Keep informed on technical aspects of stereo consoles.
Amphenol's new products.
85. Need a tuner? Preamp? Amp?
100. You can get increased CB range Tape deck? Then inspect Dyna for
and clarity using the "Cobra" trans- kits or wired units. It's worthwhile
ceiver with speech compressor -re- looking at test reports Dyna sends
ceiver sensitivity is excellent. Catalog your way.
sheet will be mailed by B &K Division 110. Get the latest facts on sound
of Dynascan Corporation.
columns. American Geloso Electronics
54. A catalog for CB'ers, hams and Inc. offers a ten-page booklet giving
experimenters, with outstanding val- the bows and whys plus method of
ues. Terrific buys on Grove Electron- installation and arrangement of sound
ics' antennas. mikes and accessories. columns.
in audio
96. If a rugged low cost business/ 15. A name well -known
is Acoustic Research. Here's
industrial two-way radio is what circles
booklet on the famous AR speakyou've been looking far, be sure to its
send for the brochure on E. F. John- ers and the new AR turntable.
son Co.'s brand new Messenger "202." 16. Discover how Cueing Control,
anti-scating and other Garrard fea102. Sentry Mfg. Co. has some inter- tures in the Lab 80 offer tops in audio
esting poop sheets on speech clippers, listening. 32-page Garrard Comparaconverters, talk power kits and the tor Guide will make you a wiser
like for interested CB'ers, hams and buyer-get it.
SWL'ers, too.
17. Build your own bass reflex en103. Squires-Sanders would like you closures from fool -proof plans offered
to know about their CB transceivers, by Electro- Voice. At the same time
the "23'er" and the new "S5S." Also, get the specs on EV's solid-state hi-fi
new pace setter for the audio
CB accessories that add versatility to line
industry.
their 5- wattera.

-a

108

a

colorful

108 -page

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? University Sound has an interesting microphone booklet audio fans should
read before making a purchase.
An assortment of high fidelity
components and cabinets are described

27.

in the Sherwood brochure. The cabinets can almost be designed to your
requirements, as they use modules.

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.
95.

99.

Get the

inside info

on why

Acoustech's solid -state amplifiers are
the rage of the experts. Colorful brochure 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 accessories.

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.

All the facts about Concord
Electronics Corp. tape recorders are
yours for the asking in a free booklet. Portable, battery operated to four track, fully transistorized stereos cover every recording need.
31.

"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. Includes a valuable table of recording
32.

times for various tapes.

Become the first to learn about
Norelco's complete Carry-Corder 150
portable tape recorder outfit. Four color booklet describes this new cartridge- tape unit.
33.

If you are a serious tape audiophile, you will be interested in the
new Viking of Minneapolis line -they
carry both reel and cartridge recorders you should know about.
35.

Sound begins and ends with a
Uher tape recorder. Write for this
new 20 page catalog showing the entire line of Uher recorders and accessories. How to synchronize your slide
projector, execute sound on sound,
and many other exclusive features.
91.

ELEMENTARY ELECTRONICS

105. Get the low -down on the latest *4. Olson's catalog is a multiin educational electronic kits from colored newspaper that's packed with

HI -FI ACCESSORIES
112.

Telex would like you to know

about their improved Serenata Headset -and their entire line of quality
stereo headsets.

Trans -Tek. Build light dimmers.
amplifiers, metronomes, and many
more. Trans-Tek helps you to learn
while building.

A 12 -page catalog describing the
TOOLS
audio accessories that make hi -fi living a bit easier is yours from Switch- *78. Learn about Xcelite's line of
craft, Inc. The cables, mike mixers. pliers and snips, specialized for radio,
TV and electronic work. Xcelite's
and junctions are essentials!
hand tools offer many advantages
98. Swinging to hi -fi stereo head- worth looking into. Bulletin N464
sets? Then get your copy of Superex and N664.
Electronics' 16 -page catalog featuring
a large selection of quality headsets.
TELEVISION
39.

104. You can't hear FM stereo unless your FM antenna can pull 'em in.
Learn more and discover what's available from Finco's 6 -pager "Third Dimensional Sound."

AMATEUR RADIO
A long -time builder of ham
equipment, Hallierafters will send you
lots of info on the ham, CB and commercial radio-equipment.
46.

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.

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.
59.

Corre(International
spondence Schools) offers 236 courses
including many in the fields of radio,
TV, and electronics. Send wr Lice
booklet "It's Your Future."

*61. ICS

*74. How to get an F.C.C. license,
plus a description of the complete
electronic courses offered by Cleveland Institute of Electronics are in
their free catalog.

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 catalog contains over 4000 products that
embrace many interests and fields.
It's an 148 -page buyers' guide for
Science Fair fans.

*70. The Heath Co. now has a 19" *106. With 70 million TV's and 240
color TV to complement their 21" million radios somebody somewhere
and 25" models. A new B &W port- will need a vacuum tube replacement
able model will be a hot seller for at the rate of one a second! Get Unithe mobile set. Get the facts today! versal Tube Co.'s Troubleshooting
Chart and facts on their $1 flat rate
72. Get your 1967 catalog of Cistin's per tube.
TV, radio, and hi -fi service books.
Bonus -TV tube substitution guide 7. Whether you buy surplus or
and trouble- chaser chart is yours for new, you will be interested in Fair
the asking.
Radio Sales Co.'s latest catalog
chuck full of surplus buys for every
29. Install your own TV or FM an- experimenter.
tenna! Jefferson- King's exclusive free
booklet reveals secrets of installation, 8. Want a colorful catalog of
orientation; how to get TV -FM trans- goodies? John Meshna, Jr. has one
mission data.
that covers everything from assemblies to zener diodes. Listed are gov97. Interesting, helpful brochures ernment surplus radio, radar, parts,
describing the TV antenna discovery etc. All at unbelievable prices.
of the decade -the log periodic antenna for UHF and UHF-TV, and 6. Bargains galore, that's what's
FM stereo. From JFD Electronics
in store! Poly -Paks Co. will send you
Corporation.
their latest eight -page flyer listing the
latest in merchandise available, inPARTS
ELECTRONIC
cluding a giant $1 special sale.
*1. Allied's catalog is so widely 10. Burstein- Applebee offers a new
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the latest Allied Radio catalog? The power tools, tubes, and parts.
surprising thing is that it's free!
Now available from EDI (Elec*2. The new 1967 Edition of Lafay- 11.
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erte's catalog features sections on tronic Distributors. Inc.)
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containing
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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 controlled by the 500K potentiometer. The transistors 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 higher 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 colorless, 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 frequency. The output transformer which feeds
the speaker is a 2K to 3.2 -ohm type commonly found in AC -DC table radios.
Viewing the Flip -Flop Signal. We constructed 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 transistor. Before tracing it in detail, recall the
basic action of a pnp transistor. A positive going signal applied to its base reduces current 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 represents 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 increasing 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 corn110

mences to taper away, representing the relatively slow discharge of the capacitor. Collector voltage, however, is still maintained at
full cut -off condition. Only when the capacitor reaches nearly full discharge will it release 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 emergency use on the highway.
The two transistors at the left form a freerunning multivibrator which produces a
square wave approximately 69 times per minute. 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 functions occur within the semi -conductor material, 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?

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ELEMENTARY ELECTRONICS

FCC Q &

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A

Continued from page

an early start
in electronics
with

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

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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) ClassB 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.
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Ham Shack Heart
Continued from page

45

to either the normal speaker-headphone arrangement or to a telegraph converter. This
latter is a vacuum-tube device employing a
sensitive polar relay which accepts the receiver 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 switches 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
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 transmitters 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 replacement, these fuses were not deemed sufficiently important to warrant front -panel space
as they are not pertinent to actual communication operation.
The indicator lights (one for each receiver 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 monitor 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 parleleliminating all screw or solder type terminals.

-a

112

The complete control center can be unplugged 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 safeguard however, one plug and socket assembly is painted bright red, the other brilliant
green. While hardly in a class with Gemini
Control, this versatile control center apparently overlooks nothing which could be considered as a station operating convenience
and most certainly provides finger -tip control of everything, directly from the operating position.
Design Your Own. From the foregoing
description and the accompanying illustrations it should appear rather evident that
wide leeway in the design of a control center
is possible. From the simplest little transmitter-receiver AC control box to the "granddaddy" unit, these control centers offer a
broad range for exercise of ingenuity and initiative to produce a control center to suit your
equipment. Individual ideas of the "homebrew" designer and builder can run rampant. 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 leeway in modifications to suit the builders'
fancy.

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ELEMENTARY ELECTRONICS

50)t Transistor Tester
Continued from page 66

or no resistance change is noted upon applying base current, the transistor cap be assumed to be defective.
Base Leakage. The next test checks Icbo,
the collector-to-base leakage current with
emitter open, in terms of resistance or current if desired. Excessive Icbo leakage biases
or shifts the transistor operating points upwards to higher collector currents-leading
to excess heating, large -signal distortion and
other effects. A transistor with higher-thannormal Icbo leakage may or may not operate properly depending on the particular circuit 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 transistors. Silicon transistors, which have extremely-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 including 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 inadvertently 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 Ryukyu Islands voices of the Far East. Australian territories of Papua and New Guinea
operate regional stations of 10 kw each.
Europe. Very few European transmitters
broadcast on 90 meters, mainly because regional broadcasting can be done on the standard broadcast and FM bands (without the
high levels of static, usual in tropical areas,
on these bands). All of the European stations 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 being mostly tropical, many stations operate on
this band. These stations, however, are predominantly low powered. Radio TV Dominicana, 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 antenna is sufficient. Generally speaking, logging 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!
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did you notice any grid leak

?

113

_.]

Tenna -Blitz

Speech Processer

Continued from page 96

Continued from page 54

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 photographs). The bracket provides the ground
connection for the circuit via a solder lug
which is held in place by the bracket mount-

Using the Speech Processor. To use the
speech processor simply unplug the microphone from your rig and plug the microphone 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 microphone 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.

L

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 between 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.
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ELEMENTARY ELECTRONICS

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115

SSB Is In!
Continued from page 60

peaks, it is accepted within legal limits prescribed by the FCC.
Receiving Sideband. Sideband transmitting 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 receiving 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 recreate 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 receiver 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
it had been transmitted. As the BFO dial is adjusted, an incoming 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 intelligible, even during difficult band conditions. So effective is single sideband that the
new definition for conventional AM. When
that day comes, AM may very well mean

-if

"Ancient Modulation."

Detectors
Continued from page

92

provide forward bias causing collector current 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 detectors, 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

Video detector using triode in cathodefollower hookup. Coil labeled "L" serves as RF choke.

Fig. 35.

116

Fig. 36. Video detector using pentode. Both this circuit and the one appearing in Fig. 35 are AM types.

was called the "second" detector. The frequency converting mixer is a detector since
it may be a rectifier or a non -linear amplifier.
Television sets have at least three detectors, 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 detectors here. Basically, AM detectors are
rectifiers or non -linear amplifiers, and FM
detectors are essentially sensors of phase or
frequency.
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