NEW LOOK

- NEW STORIES - NEW DEPARTMENTS

Popular Electronics
FIFTY

Indestructible
125-Wait
Power Amp

CENS / OCTOBER 1970

EDISON- INVENTOR
OF WIRELESS!
REFORMING YOUR
ELECTROLYTICS

VHF-UHF GRID -DIP

OSCILLATOR
MEASURING RESISTANCE
BELOW 1.0 OHM

Stereo
Tone

Control

PHOTO ENLARGER
LIGHTMETER

DISCOVER THE EASE AND EXCITEMENT

OF TRAINING AT HOME THE NRI WAY

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Only NRI offers you this pioneering method of simplified "3 Dimensional" home -study training in Electronics, TV /Radio and Broadcasting /Communications. It's
a remarkable teaching idea unlike anything you have
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-regardless of your education -you can effectively
learn the Electronics field of your choice the NRI way.
NRI has simplified Electronics by producing "bite
size" lesson texts averaging only 40 pages each. Dozens
of illustrations open wide a picture window through
which you'll see and understand practical uses of Electronics. You start out with NRI's exclusive Achievement
Kit, containing everything you need to get started fast.
(Illustrated at right.)
NRI has organized Electronics training to take you
step -by -step from the first stages into more intriguing
areas. Once you know the fundamentals thoroughly, it's
easy to grasp more advanced theory and techniques.
You move with confidence and enthusiasm into a new
adventure filled with the excitement of discovery.
NRI has dramatized Electronics through the careful
development of special training equipment that is
programmed into your training systematically ... beginning with your first group of lessons. Things you
read about come alive in your hands as you build, experiment, purposely cause "problems" in circuits
and solve them. You learn to use test equipment, to
build radios and TV sets, transmitter, or computer
circuits. It's the priceless "third dimension" in NRI
training ... practical experience.

More than 50 years of leadership

in Electronics Training

YOU GET MORE FOR

YOUR MONEY FROM NRI
Mail postage -free card now for your free NRI catalog.
Then, compare. You'll find -as have thousands of others
-NRI training can't be beat. Read about the new
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See why NRI gives you more value. Whatever your reason
for wanting more knowledge of Electronics, NRI has an
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needs. Check the course of interest to you on postage -free card
and mail today for free NRI cata-

NEW
BILL

GI

log. Nosalesmanwillcall. NATIONAL

Electronics Div..,
Washington, D.C. 20016.
RADIO INSTITUTE,

If you served since

January 31, 1955, or
are in service, check
GI line in postage

free card.

Career? Part -Time Earnings? Hobby? Choose From 12 Training Plans

1.

TELEVISION -RADIO SERVICING

Learn to fix all TV sets, including Color.

Includes your choice of NRI Color Kit or
19" black -white TV Kit. Also covers
radios, stereo hi -fi, etc. Profitable field
spare or full -time.

2. INDUSTRIAL -MILITARY ELECTRONBasics to computers. Starts with

ICS
fundamentals, covers servos, telemetry, multiplexing, phase circuitry, other
subjects.

r.

3. COMPLETE COMMUNICATIONS*
Operation, service, maintenance of AM,
FM and TV broadcasting stations. Also

covers marine, aviation, mobile radio,

facsimile, radar, microwave.

Prepares you for

4. FCC LICENSE*
1st Class FCC License exams. Begin

with fundamentals, advance to required

subjects in equipment and procedures.

Brief
FOR ELECTRONICS
course for engineers, technicians seeking quick review of essential math:
basic arithmetic, short-cut formulas,
digital systems, etc.
5. MATH

For anyone
6. BASIC ELECTRONICS
wanting a basic understanding of Radio TV Electronics terminology and components, and a better understanding of
the field.

7. ELECTRONICS FOR AUTOMATION

Not for beginners. Covers process control, ultrasonics, telemetering and remote control, electromechanical measurements, other subjects.
B. AVIATION

COMMUNICATIONS*

Prepares you to install, maintain, service aircraft in- flight and landing systems. Earn your FCC License with
Radar Endorsement.

9. MARINE COMMUNICATIONS*
Covers electronic equipment used on
commercial ships, pleasure boats. Prepares for FCC License with Radar
Endorsement.
10. MOBILE COMMUNICATIONS*
Learn to install, maintain mobile transmitters and receivers. Prepares for FCC
License exams.
11. ELECTRICAL APPLIANCE REPAIR
Learn to repair all appliances, including
air conditioning, refrigeration, small gas
engines. Leads to profitable part or fulltime business.
12. ELECTRONICS FOR PRINTERS -.
Operation and maintenance of Elea
tronic equipment used in graphic arts
industry. From basics to computer circuits. Approved by major manufacturers.

You must pass your FCC License

exams (any Communications course) or NRI
refunds in full the tuition you have paid.

October, 1970

www.americanradiohistory.com

VOLUME 33 NUMBER

OCTOBER 1970

Popillar Electronics
p

WORLD'S LARGEST -SELLING ELECTRONICS MAGAZINE

FEATURE ARTICLES
A QUESTION OF SEMANTICS

27

Fred Shunaman

31

Dan Meyer

46

George J. Plamondon

51

George Meyerle

60

A. A. Mangieri

69

A.

77

David

Who really invented radio?

ASSEMBLING A UNIVERSAL TIGER

Low -cost,

indestructible power amplifier

BUILD AN ELECTROLYTIC RESTORER

New life for your old capacitors

ASSEMBLE A FREQUENCY EQUALIZER

Segment tone adjustment

BUILDING A PRINTING EXPOSURE LIGHTMETER
Save time and money on enlargements

VHF -UHV DRAIN -DIP OSCILLATOR

E.

McGee, Jr., K5LL1

Check 140 -540 MHz frequencies

A PRACTICAL EXPANDED SCALE MILLIOHMMETER

R.

Corbin

Measure the almost unmeas;trable

THE

PRODUCT GALLERY

Knight -Kit

81

-195 Receiver

Eico 150 Signal Tracer

Electro -Voice Landmark 100 Stereo System

COMMUNICATIONS
STEREO SCENE

OPPORTUNITY AWARENESS
SOLID STATE

87
94
98
100

J.

Gordon Holt

David

L.

Heiserman

Lou Garner

DEPARTMENTS
DIRECT & CURRENT

NEW LITERATURE
ELECTRONICS LIBRARY
READER SERVICE PAGES

NEW PRODUCTS
OUT OF TUNE

Oliver

P.

Ferrell

12
15, 115
22
111

Build a RIAA /NAB Preamplifier

Build Dynamic Diode Tester
INTERFACE

POPULAR ELECTRONICS is Indexed

In the Readers' Guide
to Periodical Literature

113
This month's cover photo by

Justin Herr

Copyright 0 1970 by ZIFF -DAVIS PUBLISHING COMPANY. All rights reserved.

POPULAR ELECTRONICS, Uetob,, 19'',. el rime .;
dumber i- Published monthly ut Onc Park :Ir.,. New' York. S.S. 1001r.
Une
subscription rate for 1-. N., U.S. Pa.r,csiOarn- and Cmrada, SG. ou: 41 "thrr u,untr es. .7 un, ,vrrond class postage paid nt
.d'eu- Sprk. 'iA.. and at add it irdr al 'nailing offices. Authorized as
conel clus-s mail !,g the Post Office letartln eat, Whom,. Canada
and far inlyment of postage in rash. Subscription srrcice and Furs 8.779: P.U. nor 1096. Flushing, S.F. 113.-62. Editorial uftres
for manuscript contributions. reader inquiries, etc.: One Park Ace., Sea- Sorb. S.S. 10016.

yu

POPULAR

ELECTRONICS

Making CB newer every day!

Midland's biggest product is innovation...such as com3at ble Single
Sideband in base, mobile, and hand-held unite... or using revolutionary
Integrated Circuitry in our professional CB line...or a sophisticated 23channel hand -held AM transceiver. That's how Midland built it reputation
in CB for first -rate performance and dependability...an we're still building!

23- Channel

10 -Watt

SSB,

5 -Watt

AM Mobile

Transceiver.

Compatible with all other CB units and mobile companion

to model 13 -880. Dual transmitters to operate either on
upper or lower side bands and all 23 AM channels. Noise
blanker, F.E.T. front erd, dual meter, PA switch, clarifier,
mike. Model 13 -873. $359.95

Pushbutton Base Mobile. Economical and compact.

Variable squelch, transmit light,
integrated circuit. Channel 9 crystals, mike. Model 13 -855. $79.95
5 -Watt, 6- Channel

23- Channel AM /SSB Base -Mobile CB. Compatible with all other CB units. 10 watts
P.E.P. on upper or lower sideband, 5 watts
AM. Two separate transmitters, automatic
digital clock. AC -DC operation. SWR /RF
meter, noise blanker, clarifier, on /off and
transmit lights. Tape output, headphone
jacks; mike. Model 13 -880. $369.95

Complete
Midland CB broFREE!

chure. Write:

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I

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Prices shown are suggested retail

Dept.. 1410,

AL

Box1903,
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P.O.

CIRCLE NO. 29 ON READER SERVICE PAGE.

5

October, 1970

www.americanradiohistory.com

Earn Your

A. S. E. E.
DEGREE

Popular Electronics
LAWRENCE SF'ORN
Pr blisher

OLIVER P. FERRELL

(Associate in Science in Electronics Engineering)

Editor

LESLIE SOLOMON
Technical Edito

JOHN R. RIG S
.Managing Edito

EDWARD I. BUX AUM

Art Director

ALEXANDER W. BURAWA
.Associate Editor

Mostly by NOME STUDY Instruction

Where will you be five years from today? Are you
headed for real advancement in electronics, or
are you in a rut? The technical experience you
now have is important; it gives you a head start
toward a better future. But to get ahead and stay
ahead, experience must be supplemented with
more education in electronics and allied subjects.
Grantham School of Engineering -"the college that comes to you"- offers to electronics
technicians a home-study educational program
for the Degree of Associate in Science in Electronics Engineering (the ASEE), accredited by
the Accrediting Commission of the National
Home Study Council.
The complete degree program except for the
final ten lessons is presented entirely by correspondence. However, these last ten lessons are
part of a two -week "Graduation Seminar" held
at the School. Thus, you may do all of your
ASEE Degree work by correspondence except
for the final two weeks.
Accreditation and G.I. Bill Approval
Grantham School of Engineering is accredited
by the Accrediting Commission of the National
Home Study Council, is approved under the G.I.
Bill, and is authorized under the laws of the State
of California to grant academic degrees.

GRANTHAM
"the
that
college

1505

N.

Western

ENGINEERING
comes to you"

Av, Hollywood, CA

90027

TI

Grantham School of Engineering PE -10 -70

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

I Gentlemen: I have been in electronics for
years.
I

Please mail me your free Bulletin.

ANDRE DUZANT
Technical Illustrator

PATTI MORGAN
Assistant Edito

JUDITH L. HOGAN

Editorial A.esietn of
J. GORDON HOLT
L. E. GARNER. JR.
DAVID L. HEISERMAN
Contribtting Edit -,re

J. ROYCE RICHARD
Assistant Pnbl;.ei,

RICHARD J. HALPERN
Advertising

Mrterr

i,i

ROBERT UR

.Marketing ]la n,'o.-r

MARGARET DANIELLO
Advertising Service .tinngo,-

FURMAN H.

BB

Cron Viee Presid ut

Electronics and Photo. aphte
ZIFF -DAVIS PUBLISHING COMPANY
Editorial and Executiv Offices
One Park Avenue, New York, ew York 10016
212 679 -7200

Midwestern Offi e
The Pettis Group, 4761 We t Touhy Ave.,
Lincolnwood, Illinois 60646, 312 679-1100
GERALD E. WOLFE, DI K POWELL
Western Officei
9025 Wilshire Boulevard, Beverly HMIs, California 90211
213 CRestview 4-0265; BRa show 2 -1161
Western Advertising Manag r, BUD DEAN
Japan: James Ye gi
Ishikawa Mansion #4, S akuragaoka
Shibuya -ku, Tokyo, 46 2-2911.3

Circulation Offi,e

P.O. Box 1096, Flushing, N.Y. 11352

William Ziff, President

W. Bradford Briggs, Executive Vice President
Hershel B. Serbin, Senior Vice President
Stanley R. Greenfield, Senior' Vice President
Philip Sine, Financial Vu a President
Walter S. Mills, Jr., Vice President, Circulation
Phillip T. Heffernan, Vice President, Marketing
Frank Pomerantz, Vice President, Creative Services
Arthur W. Butzow, Vice President, Production
Edward D. Muhlfeld, Vice President, Aviation Division
Irwin Robinson, Vice President, Travel Division
George Morrissey, Vice President
Sydney H. Rogers, Vice President
Ziff -Davis also publishes Airline Management and Marketing Inluding American Aviation, Boating. Bus ness A Commercial Avisinn. Car and Driver. Cycle. Electronics World. Flying, Modern
Bride. Popular Photography. Skiing, Siding Area News, Skiing
Trade News, Stereo Review. and
Travel Weekly.

3579 and all subscriptions corr,teondence should be addressed to POPULAR ELECTRONICS. Circulation Department. P.O.
Box 1096. Flushing, N.Y. 11352. Please allow at least six weeks for
change of address. Include your old address. a well as new-enclosing if possible an address label from a recent Issue.

Forms

EDITORIAL CONTRIBUTIONS must be accompanied by return postage and will be handled with
;
sonal lc
however. publisher
for return or safety of art work, photoass m

ility
0
ormanuscripts

Name
e

Address

City

State

Zip

CIRCLE NO. 13 ON READER SERVICE PAGE

Member Audit Bureau

of Circulations

POPULAR ELECTRONICS

DIRECT

& CURRENT

Second in a Monthly Series by Oliver P. Ferrell, Editor

CB! FOR BETTER? OR WORSE?

Since its introduction to the 27 -MHz band, millions of words
have been written about the pros and cons of CB. From that
plethora of verbiage, there has been little objectivity
substantial denegation of facts, and an incomprehensible attitude
toward CB by the Federal Communications Commission. Exactly
how the FCC can ignore 4,000,000 CB transceivers aid 875,000
"licensed" CB stations defies rational explanation. Eut, ignored
it is- castigated on occasion-and a source of enormous revenue
to the FCC.
Even the most cursory tally shows that CB license fees and
forfeitures provided 7 /o of the money spent by the FCC in 1969
more than any other radio service. This was achieved at an
expenditure of around $300,000. The FCC's return or its investment
is about 500 /o and if that situation is not a shocker, bear in mind
that the FCC expects CB to make up 171/20/o of its ainual budget
starting August 1, 1970. For this larger sum, the FCC apparently
expects to provide little or no additional services.
Several years ago the FCC proposed an independent study
of CB regulatory problems and budgeted money to get the program
under way. When Congress didn't approve of all the FCC proposed
expenditures, what money was available went to the Broadcast
Bureau and hopes of finding a solution to CB went down the drain.
Popular Electronics feels that the time is past for the FCC
to "make something" as is out of 27 -MHz CB. The $20 license fee
(up from $8) will be ignored by an ever -increasing number
of illegally operating CB'ers. In its unthink=ng haste to make
itself look good fiscally on paper, the FCC has creased a behemoth
out of a monster. Rather than take the initiative and right
the wrongs of CB, the FCC has opened the floodgates to put more
stations on the air with fewer and fewer controls.
When will the FCC learn that they must live with CB? It cannot
be hidden away in the attic or swept under the rug. Through its
own inadequate planning and slavish responsiveness to broadcasting
lobbies at the sacrifice of all other radio services, the FCC is
now in a cul -de -sac.
Popular Electronics finds no valid argument for the FCC's
continuing to think of CB solely in terms of 23 chancels scattered
around 27 MHz. The FCC must consider either the allocation
of additional channels between 26.1 and 27.54 MHz (90 channels
possible) or close down the 27-MHz citizens band within 5 years
and move it en masse to the 450-MHz band.

October, 1970

www.americanradiohistory.com

Every record
you buy is
one more reason
to own a Dual.
of your
- which may
or
of dollars - we

If you think
total investment in
records
be hundreds
even thousands
think
you'll agree that those records should be
handled with the utmost care.
Which brings us to the turntable,
the component that handles those
precious records. Spinning them on a
platter and tracking their fragile grooves
with a diamond stylus, the hardest
substance known to man.
For many years, serious music lovers
have entrusted their records to one make
of automatic turntable Dual. In fact,
most professionals (who have access to
any equipment) use a Dual in their own
stereo component systems. And not
always the highest priced mode.
So the question for you to consider
isn't which Dual is good enough, but
how much more than "good" your
turntable has to be.
This question can be answered in our
literature, which includes complete
reprints of independent test reports. Or
at any of our franchised dealers.
United Audio Products, Inc.,
120 So. Columbus Ave., Mt. Vernon,
New York 10553. Dual

5,

To obtain

a copy of any of he catalogs or

leaflets described below, fill in and mail
the Reader Service blank on page 15 or 115.

Dynascan Corp. has released a 24 -page catalog of B &K Professional Test Equipment
for electronics servicing and school, laboratory, and industrial applications. Solid-state
design is dominant in the instrument listing,
including a FET VOM, an rf signal generator, a sine /square -wave generator, and a tube
tester with lockout pushbuttons that provide
positive short indications. Other instruments
listed include: a sweep/marlter generator,
oscilloscope /vectorscope, capacitor analyst,
color bar generators, etc. Probes, adapters,
and other accessories are also included.
Circle No.

CIRCLE NO. 27 ON READER SERVICE PAGE

8

Reader Service Page

15

or 115

illustrated catalog has just been

published by Turner Company describing its
complete line of microphones and accessory
equipment. The catalog, No. 2620, contains
specifications and prices of professional, recording, broadcast, and PA cardioid dynamic
mikes; standard and transistorized mobile
communications mikes; tape recording and
general- purpose mikes; paging and PA
mikes; and stands, cartridges, and accessories.
A 24 -page

Circle No. 76 on Reader Service Page

15 or

IS

For the automobile enthusiast who demands

high performance from his wheels, Automotive Research Electronics has available a catalog of electronic device listings for mobile
use. Among the items listed are a capacitive
discharge ignition system, a dwell stretcher,
street and strip r /min limiter. road and track
r /min limiter, and a digital racing timer.
Circle No.

Dual 1209, $129.50.

Other models from $99.50 to $175.00.

75 on

77 on

Reader Service Page

15

or

115

The Space Support Division, Sperry Rand

Corp., is offering Scanning Electron Microscope (SEM) services at its Microanalysis
Laboratory on a machine-hour basis. The
SEM has a useful range from 20X to 50,000X
and is capable of examining, with little or no
special preparations, surface details of almost
any kind of specimen in such diverse fields
as biology, microelectronics, and material
science. A photograph which faithfully repPOPULAR ELECTRONICS

thrifty tool

Be creative -and

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

NOW YOU CAN SEE

NEW "TREASURE

THE MUSIC YOU HEAR.

`HUNTER" KIT

Finds metals, pipes several

inches underground. EICO
TH -30 Solid State Treasure
Hunter locates iron, steel,
tin, gold, silver, copper

etc. Beep pitch increases as you near

object.

Battery operated. $29.95.

MACES"CELESTIAL
COLOR
Electronic Art in Motion.
"CH
"CHROMACUBE"

Sound It Color
Color Organs, Translators.
Strobes

LITES"

\,

Classic white 18'

Cube features a
fantastic audioresponsive light
disn!ny-

Constantly flowing
color images move
in rhythm to manic.
24" x 24" x 6 ".

COLOR ORGANS
The now dimension
to music pleasure.

eectronic solid-state
Aud.o.COl.4, Organs transform
EICO all

NEW "BULLHORN" KIT

Carries your voice up to 400 feet.
EICO BH-16 Solid State Bullhorn.
2V lbs. light, is perfect for
all outdoors. camping. sports.

"LIGHT FANTASTIC"

Battery-operated, $15.95.

Translucent dome provides 3-

dimensional world of ever changing

light patterns it response to music. 38" high.

crtina2
STEREO KITS
The lowestpriced

component quality
high fidelity!
EICO 3780 50-Watt

P; EON

NEW EICOCRAFT

Silicon Solid State FET AM -FM Stereo

Kit $109.95, Wired $169.95

The electronic science project kits

for beginners, sophisticates,
educators. 42 lots to dale.

Receiver.

sound war es into moving synchro.

nized color images.
MODEL 3450 Giant (30" x 12
10"1 4-Channels. Kit $79.95,
Wired $109.95.
MODEL 3445 (24" x 12" x 10 ")
4-Channels. Kit $64.95,
Wired $99.95.
MODEL 3440 (10" x 15" x 16 ")
3- Channels. Kit $49.95.
Wired $79.95. Other models to.
choose, fsam $19 95 and up.

TRANSLATORS
The electronics you need to create

P9

audio -stimulated light displays.

MODEL 3460
I Channel.
Kit $24.95,
Wired $39.95.
MODEL 3465
3 Channel.
Kit $39.55, Wired $69.95.

STROBIE LITES
Burst of write light flash in
FM WireleSS
M
$9.95.

EICO 3080 50-Watt Silicon

Solid State Stereo Amplifier.

Kit $69.95, Wired $109.95

8 NEW EICOCRAFT KITS

Automotive "LIGHTGUARD"
"VARIVOLT" DC Power Supply
"MOODLITE" Light Dimmer
Control "VARASPEED" Motor
" LIGHTSHOW"
Speed Control
Sound / Lite Translator
"ELECTRIC FIESTA" Audio Color
"SUPER MOODLITE"
Organ
Remote Control Light Dimmer
"ELECTROPLATER" From
$2.50 to $14.95.

NEW

"FLEXt -CAB"
Build your own custom
designed cabinet in
minutes!
Give your EICOCR AFT
and other projects
that finished professional look with
decor -styled FLEX(.
CAB vinyl clad steel
cabinets. Fast, easy,
push -together
assembly. 3 -sizes

from $3.49.

EICO 3300 Silicon Solid State

FET AM -FM Stereo Tuner.

Kit $69.95, Wired $109.95

NEW SOLID STATE TEST INSTRUMENTS

The fast and

111.1.

only, nl,d '.tat.' t''J ,' ',,I, "I,

Ili MI

rit

for 5 years!

soFka7.1

Kit $69.95, Wired $94.50.

EICO 242 Solid State FET.TVOM. Kit $69.95, Wired $94.50.
EICO 150 Solid State Signal Tracer. Kit $49.95, Wired $59.95.
EICO 330 Solid State RF Signal Generator.
Kit $59.95, Wired $24.50.

FREE 1970 EICO CATALOG

;

AUTOMOTIVE
EICO 889 Solid State
Capacitive Ignition

Bcnst gas mileage up to 25 %,

life of points, plugs 10 100.000 miles;

Kit $29.95, Wired, $39.95.

PE -1C

rro FREE catalog describing the lull EICO

200 best buys, and name of nearest dealer.
Name

Address
City

Adjustable Rate.
Kit $29.95,
Wired $39 95.
Model 3475
Audio Actuated
Kit $39.95, W Ircd $50 95.

11110011.1.1

RICO 240 Solid State FET-TVM. Kit $59.95, Wired $79.95.

EICO 379 Solid State Sine/ Square Wave Generator.

lira:

cadence of each beat of audio.

Model 3470

State_

Zip_

EICO 888 Solid Stole

f.lciversol Engine Analyzer.
Tunes and troubleshoots
your car /boat engine. the
totally professional 's:
Kit $49.95, Wired $69 -9,.

FICO Electronic Instrument Co.. Inc.

283 Malta Street, Brooklyn, N,Y, 11207

CIRCLE NO. 12 ON READER SERVICE PAGE

October,

1970

www.americanradiohistory.com

LITERATURE (Continued from page 8)

Get
the
last
word
every
time.

resents the surface features of the test sample can be provided within a few seconds at
any stage of the examination. Flyers are
available on request.
Circle No. 78 on Reader Service Page

15

or

115

A two -page data sheet, Ni. 5170, that describes the company's new Models 8000 and
8000 -A digital volt- ohm- milliammeters is
available from Triplett Corp. The two-color
data sheet provides complete electrical and

mechanical specifications.
:ircle No.

79 on Reader Service Page 15 or 115

Catalog No. 710, available from Lafayette

Radio Electronics, is a complete buyer's
guide to current home entertainment, hobby,
and experimenter parts and equipment. It
includes the latest in hi-fi tuners, receivers,
and amplifiers; turntables; reel -to -reel, cartridge, and cassette recorders and decks;
TV receivers; test equipment; auto accessories; and many other itenis.
Circle No. 80 on Reader Service Page

Get

Turner's
" +2" series:
+2 base station mike (List Price:
$55.00) and M +2 /U mobile mike
(List Price: $39.50). Up to 50 times
the modulation of other mikes. No
more fade outs. No more static.
(Even at great distances). Both
"--2" series microphones use a
two - transistor
pre -amp and

work with all

transistor and
tube sets. See
them at your CB
dealer or distributor soon. And
get.the last word.

International Rectifier's No.

15

or 115

"Diamond
Line" catalog for 1970 will e of interest to
anyone involved in electro] llcs either as a
hobby or a livelihood. It lis s such items as
Diacs and Triacs, IC's, silic n and germanium diodes and transistors, photocells, heat
exchangers, and electrolytic capacitors. Also
included is a two-page cross reference guide
to IR transistor and diode replacements.
Circle No.

81

TD352

on Reader Service Page 15 or 115

An 80 -page catalog of computer parts, Geiger counters, electronic parts and equipment

cameras, telescopes, watches, a tachometer

kit, and many other surplus parts and items
from government and industry is available
from B. & F. Enterprises. The catalog lists
some real bargains on electronic parts.
Circle No.

82 on Reader Service Page 15

or

115

Sharpe Audio Division of cintex, Inc., is

offering their price list and atalog of newly
developed audio visual pr ducts. Included
are high-quality headphones, headset microphones, cordless induction -type headsets,
wireless headsets, and audio station and
sound centers. There is also an extensive
listing of impedances and radio frequencies.
Circle No.

83 on Reader Service Page 15 or 115

A new full-line, 68 -page dealer catalog of

TURNER
919 -17th Street N.E.,
Cedar Rapids, Iowa 52402
In Canada: Tri -Tel Associates. Ltd.

CIRCLE NO.55 ON READER SERVICE CARD

selected electronic products has just been

published by North American Electronics,
Inc. The various items listed are in discrete
product groupings which include virtually
everything in electronics from test equipment to unit parts such as i esistors and capacitors. The number of items in standard
packages is listed.
Circle No. 84 on Reader Service, Page

10

15

or

I5

CIRCLE NO. 5 ON READER SERVICE PAGE

-*

THE GREAT NEIN

Locking for the mobile antenna that outperforms the others? Get the "Super 45 ".
You'll see why Shakespeare, the fiberglass pioneer, is the leader in fine an-

"45"

G57a2>eaeCth2

tonnas.

Industrial Sales Division

Jefferson Square

P.

0. Drawer

2416,

Columbia, S. C. 29202

www.americanradiohistory.com

(803 -779-5800)

1970 -WINTER

$1.35

ELECTRONIC EXPERIMENTER'S
HANDBOOK
148 pages of the most fascinating and challenging construction projects for the electronics hobbyists. All with complete schematics, illustrations, parts list, and easy to- follow instructions that guarantee you
perfect finished products.

1970-SPRING

iSTEREO

$1.50

ELECTRONIC EXPERIMENTER'S
HANDBOOK
Another big package containing the most
challenging, fun -to -build electronics projects
ever! Be sure to order this one today!

'.2;

Ht-Ft
o1HE,CT9RY
t

-15-

1970 STEREO /HI -FI DIRECTORY $1.35

Giant 180 page buyer's guide listing more

than 1,600 individual Stereo /Hi -Fi components by 176 manufacturers. Nine indi
vidual sections complete with specs, photos,
prices -the works!

6 Vital Components
For Knowledge . . Sheer
For Profit ...For
Electronics Enjoyment!
1970 TAPE RECORDER ANNUAL $1.35
130 pages covering every aspect of
tape recording. Complete buyer's guide to
the brands and models on the market. Expert tips on equipment
making better
tapes
copying -everything you
want and need to know about tape recording.
Over

-editing-

1970
$1.35
COMMUNICATIONS HANDBOOK
148 fact packed pages for the CB, SWL
or HAM. Equipment buyer's guide -photos

-tables- charts-getting

license-ev-

erything to make this the world's most complete guide to communications.

1970

$1.35

ELECTRONICS INSTALLATION &

SERVICING HANDBOOK
Covers all,8 areas of- consumer electronics
servicing--all the tricks of the trade in
one complete guide.The industry's "how-to"
book for installing and servicing consumer
electronics equipment.

ZIFF -DAVIS SERVICE DIVISION

Dept. W

595 Broadway, New York, N.Y. 10012

Please send me the annuals I've checked below:

1970
1970
1970
1970
1970
1970

Electronic Experimenter's Handbook -Winter

Electronic Experimenter's Handbook -Spring
Stereo /Hi -Fi Directory
Tape Recorder Annual
Communications Handbook
Electronics Installation 8 Servicing Handbook

am enclosing $
My remittance includes an
additional 25f per copy for shipping and handling (Outside
U.S.A. all magazines are $2.00 per copy, postpaid.)

PE-10-70

print name
address

city

--

12

zip
PAYMENT MUST BE ENCLOSED WITH ORDER ev

LIBRARY
ABC's OF THERMISTORS
by Rufus

P.

Turner

This book tells, in simple language, how the

thermistor works and how it can be used in
representative circuits. The text should be
equally useful to the student and practicing
technician. Soft cover. 96 pages. $2.95.
101 QUESTIONS & ANSWERS ABOUT
HI -FI & STEREO
by Leo G. Sands & Fred Shunaman
Whether you are interested in building and
servicing hi -fi equipment or in how well hi -fi

equipment can reproduce music, there should

be something for you in this book. The simple question-and -answer format of the text
seems to be the best approach to the subject.
Soft cover. 128 pages. $3.50.
COLOR -TV TROUBLE CLUES (Vo ume

3)
Since the first two volumes of Trouble Clues
were published, remarkable changes have
taken place in the television industry. This
volume contains information On receivers
produced since Volume 2 was published. It
is not intended to replace the earlier volumes; rather to provide additional, up -to -date
material. Soft cover. 128 pages.. 3.50.
TAPE RECORDER SERVICING GLIDE
by Robert G. Middleton

In this book are presented both the electronic

circuit theory and mechanical construction
of tape recorders. The magnetic and biasing
circuits unique to tape recorders are emphasized in the text. Soft cover. 96 pages. $3.95.
Above four titles published bp Howard W.
Sams & Co., Inc., 4300 West 62 St., Indianapolis, IN 46268.
ELECTRIC MOTOR REPAIR, Second Edition
by Robert Rosenberg

state

Electronics

-j

For many years, there has been a need for

a practical nontheoretical book on electric
motor repair and control that c uld be used
by men with little background o knowledge
of electrical engineering. This b ok appears
to fill that need admirably. Bo h alternate
and direct current motors are reated, and
extensive consideration is given to the connections and troubles in controlle s. Although
numerous changes and addition have been
made in this edition, nearly all f the material that appeared in the first edit on has been
POPULAR ELECTRONICS

The Army can take

your hobby and turn if
into a career.
Tear down an engine
or snap a picture or solder some
wires to a speaker to rock the
room.
Maybe you call it a hobby
or a knack or maybe even your
thing.
And, you know, the Army
can take that favorite talent of
yours and turn it into a rewarding.
lifetime career.
We have more horsepower
than the Motor City.
We have cameras that can
take a portrait of a bird a half
mile away.
We have electronic
equipment so new that it hasn't
even been named yet. The Army
needs people to run it all and
keep it running.
We can train you to be an
expert. What's more, we'll
guarantee this training in writing
before you enlist.
Send for our free book.
Use the coupon or write:
Army Opportunities, Department
200A, Hampton, Virginia 23369.
It's full of things. Maybe
yours is one of them.
Your future, your decision.
Choose ARMY.

Army Opportunities
Date
Dept. 200, Hampton, Va. 23369
I'd like to find out more about how the Army
can turn niy hobby into a career. Please send me
your free booklet.

Nane

Date of Birt

Address
City
State

County

_Zip

Phone

Education
2PE 10.70

retained. Because solid -state electronics is

important to motor control, a section on solid
state controls has been added. Study questions for each chapter are included. The physical design of the book is practical; all illustrations appear at the reader's left on a
separate wire ring binder. while at the right
is the text.
Published by Holt, Rinehart and Winston,
Inc., 383 Madison Ave., New York, NY 10017.
Soft cover.

750

pages. $12.95.

CB RADIO
by Leo G. Sands

from the

inventors of the
dual polarity loop

antenna...

*THE MOONRAKER:
Designed along the lines of antennas used to
pinpoint signals on "moon bounce."

$6.95.

Uses only

AUDIO CYCLOPEDIA, Second Edition

Combines li wave cross dipole elements with

the famous Avanti PDL".' design reflector. Switch
box (included) permits operation on the horizontal or vertical mode.

Most books dealing with the subject of audio

cover only specialized topics -such as hi -fi
amplifiers, tape recorders, etc. --or touch on
a broad range of subjects without really
going into detail. The Audio Cyclopedia, however, combines specialized topics from all
areas of audio and discusses them in detail.
Primarily a reference source, this book is of
particular importance to the audio engineer
but will also be used by anyone whose interest in audio goes beyond just listening. The
text coverage is complete and is supported by

a 15' boom to eliminate efficiency loss

inherent in multiple in -line quad designs, thus
better signal excitation is achieved to provide
greater true gain.

Aircraft quality seamless aluminum construction

... extrusions and castings used in hubs and
mounts

... no

stampings.

year guarantee.

SPECIFICATIONS
Gain:
SWR:

Impedance:
Power Handling:
Front to Back

14.5 db
1 20:1
50 ohms
1000 watts

Wind Survival:

Weight.

$129.95
*Patent Pending

want%

38 db
25 db

90 mph
24 lbs.
Made in America
AVENUE.
ADDISON. ILLINOIS 60101

33 -35 WEST FULLERTON

AVANTI RESEARCH & DEVELOPMENT. INC.

THE PACESETTER

by Howard M. Tremaine

numerous schematic diagrams, photographs,

line graphs and charts.

Published by Howard W. Sands & Co., Inc.,

4300 West 62 St., Indianapolis, IN 46268. Hard
cover. 1757 pages. $29.95.

INTRODUCTION TO SWITCHING
CIRCUIT THEORY
by Donald D. Givone

Separation
Vertical to Horizontal
Separation

IN HIGH PERFORMANCE

ANTENNAS

CIRCLE NO. 2 ON READER SERVICE PAGE

14

Since the Federal Communications Commission established the Class D Citizens Radio
Service, more than one million station
licenses have been issued authorizing the use
of some four million CB transceivers. Here,
in this one compact volume, is the entire
story about the most widely used and fastest
growing form of radio communication. The
book describes the Citizens Radio Service
and its many applications. Equipment is discussed in detail, and information on equipment installation and maintenance as well as
on operating rules is presented. The book is
a basic introduction to CB radio.
Published by A.S. Barnes & Co., Box 421,
Cranbury, NJ 08512. Hard cover. 143 pages.

Most books on switching circuit techniques

are either too basic or too technical. Here
the author attempts to hit a happy medium
by integrating the two extremes -first providing the fundamental mathematical principles of switching circuit theory and then
letting the mechanics of logic design be a
direct consequence of the theory. Because
this book is for a first course on the undergraduate level, mathematical development is
presented in detail. Special features include:
a chapter devoted to universal logic operations; transformation development between
switching expressions involving these operaPOPULAR ELECTRONICS

EADER
ER1liGE PAGE

free information service:

s an easy and convenient way for you to get additional information about
products advertised or mentioned editorially (if it fas a "Reader Service
Number ") in this issue. Just follow the directions below .. and the material
will be sent to you promptly and free of charge.

Here

On coupon below, circle the number(s) that

corresponds to the key numbs r(s1 at the bottom or next to the advertisement or editorial mention that is of interest to you. (Keay cumbers for
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Cut ou: the coupon and mail it to: POPULAR ELECTRONICS,

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Void After November 30, 1970

POP

NICS

ELECTULROAR
1

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4
24
44
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84

P.O. BOX 8391

PHILADELPHIA, PA. 19101

8 9 10 11 12 13 14 15 16 17 18 19 20
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www.americanradiohistory.com

tions and the more conventio

of Boolean algebra; and a st
mental mode and pulse mode
cuits.
Published by McGraw -Hill Boo;
42St., New York, NY 10036. H
pages. $14.50.

al operations

dy of fundaequential cirCo., 330 West

rd cover.

494

DESCRIPTIVE ELECTRONICS
by

R.R

8 C.A. Huffsey

On the beginning electronics level, this volume proposes to explain both tube and solid state circuits without the extensive use of
mathematics. After an introduction to the
concepts of current and voltage and a discussion of basic electronic components, the
text continues with detailed ex lanations of
circuit operations. Examples of ower supply,

amplifier, oscillator, and detect circuits are

analyzed. Experiments suggeste in the book
are adaptable to almost any ex sting laboratory situation -including the h bbyist's and
experimenter's bench.
Published by Holt, Rinehart tfnd Winston,
Inc., 383 Madison Ave., New Yo 'k, NY 10017.
Hard cover. 365 pages. $9.95.
FILTER SYSTEMS DESIGN:
ELECTRICAL, MICROWAVE:, AND
DIGITAL
by Yale Jay Lubkin

Scanningly New and Field Tested

for Automatic, Positive, and Clear
Reception of the Intricate UHF Band
Push the buttons. They're there to give you program control
over your choice of eight UHF crystal controlled frequencies

-450 -470 MHz.

Program it to hear both sides of two -way conversations, even
though they may be on different frequencies. Operate it automatically or manually. Each of 8 channels has a push button for
placing the frequency in or out of service. Hear what's happening on all or any combination of channels. Fascinating scanning
lights detail over busy receiver's signal search. It stops to hear
all of an active message.... then resumes search for a return
or other signal.
Our new monitoradio /scanner has been developed and tested to

perform in areas of high density interference. With Regency,

you get the result of exacting performance: .05 second per
channel scan rate and 0.7 microvolt sensitivity @ 20 db.

It comes complete with AC and DC cords, mobile mounting

bracket, detachable telescope antenna, built -in 4" speaker plus
terminals for external speaker and remote antenna. All for only
5159.00. Crystals $4.95 each. Also single channel Model TMR1 U $119.00. See them at your favorite Regency retailer all over
the country.
American Made
One Year Warranty

Patent Pending

-TeMC

_ELECTRONICS, INC.

Indianapolis, Indiana 46226

7900 Pendleton Pike
CIRCLE NO. 21 ON READER SERVICE PAGE
16

Employing an informal but thorough approach, this book is designed tb extend the
working engineer's knowledge of electrical
filters and to provide him with tools he can
use immediately. Presented are the fundamental concepts of electrical filters: why and
how the various kinds originated, what types
of problems they solve, and their limitations.
Some of the concepts developed have never
before appeared in printed form; and, while
they are rather advanced in nature, they are
nevertheless understandable. Aimed at the
engineer, this book requires little mathematical sophistication; the math needed is developed with the flow of the text.
Published by Addison -Wesley Publishing Co.,
Inc., Reading, MA 01867. Hard cover. 212
pages. $11.50.

FET APPLICATIONS I-IANDI3OOK,

Second Edition

by Jerome Eimbinder

For anyone who needs practica design data

on FET circuits, here is possi ly the most
current and comprehensive gui a currently
available. In its second editio the book
contains almost 25 percent more material
than before, to the tune of six entirely new
chapters. The text covers FET types, parameters and characteristics, and operational
modes. Emphasis is on applications from
linear to switching circuits and IC's. For
the engineer interested in photo -FET design,
the last two chapters offer new data and
many practical and unusual applications, including a FET electrometer amplifier. More
than 250 schematics and graphs illustrate
(Continued on page n.7)
,

UNIVERSITY JUST MADE YOU A

SOUND INSTALLATION EXPERT

= Totally
Coordinated Sound
systems you
can install yourself.

TCS

Totally Coordinated
University just invented TCS
Sound systems so painstakingly pre- engineered anyone
can install them. Everything you need comes with each
system: speakers, amplifiers, microphones, color -coded
'cables, plus assembly and installation instructions. All
pre- engineered, pre -matched, pre- sized, for hundreds
of applications.
It you can twist a wi-e, screw a screw, push a plug into
a socket -congratdations! University just made you
a sound installation expert.,
Write for details today about haw you can
install your own PA sound system tomorrow.

UNIVERSITY` SOUND

CIRCLE NO. 32 ON READIER SERVICE PAGE

October, 1970

www.americanradiohistory.com

17

Second in

series...

Can you solve

these problems
in electronics?

They're a cinch after you've taken RCA Institutes'

new communications electronics program.
It includes new preparation for the FCC license plus the
assurance of your money back if you fail to get it.

This one is quite elementary.

This one is more advanced.

2uf

2uf

tuf

In this door bell circuit, which kind of

transformer is T, step -up or step -down?

What is the total capacitance in the above

Note: if you had completed only the first lesson of

any of the RCA Institutes Home Study programs,
you'd easily solve this problem.

Note: you'd know the solution to the problem if

you'd taken only the first two lessons in RCA's new
Communications Electronics Program.

circuit?

These are the lessons that prepare you step -bystep for an FCC License.

This license is a requirement for servicing all

types of transmitting equipment nd can help
open doors to jobs commanding high income in
communications, radio and broadcasting,
aerospace, industrial automation and many others.

lTiS

uMop-datS alaMSut1
18

For a rewarding career with good pay, take that

first step now. Send for complete information

mail the attached card.

POPULAR ELECTRONICS

RCA Institutes Autotext learning method

makes problem -solving easier...
gets you started faster towards a good-paying career in electronics

Are you just a beginner with an interest in

electronics? Or, are you already making a living
in electronics, and want to brush -up or expand
your knowledge? In either case, RCA has the
training you need. And Autotext, RCA Institutes'
own method of Home Training will help you learn
more quickly and with less effort.

Wide Range of Courses

Select from a wide range of courses. Pick the
one that suits you best and check it off on the
attached card. Courses are available for beginners
and advanced technicians.
Electronics Fundamentals
Black & White'Television Servicing
(Transistorized TV Kit Available)
Color Television Servicing (Color TV Kit Available)
FCC License Preparation
Automatic Controls
Automation Electronics
Industrial Electronics
Nuclear Instrumentation
Electronics Drafting
Computer Programming
Plus these new
up -to- the -minute courses
Semiconductor Electronics
Digital Electronics
Solid State Electronics
Communications Electronics

Build and keep this

valuable oscilloscope.

Prepare for good paying

positions in fields like these
Television Servicing
Telecommunications
Mobile Communications

Variety of Kits -Yours to Keep

A variety of RCA Institutes engineered kits are
included in your program of study. Each kit is yours
to keep when you've completed the course.
Among the kits you construct and keep is a working
signal generator, a multimeter, a fully
transistorized b- eadboard superheterodyne
AM receiver, and the all- important oscilloscope.
These 4 kits are at no extra cost. Compare this
selection with other home study schools.

Two Convenient Payment Plans

Pay for lessons as you order them. No contract
obligating you tc continue the course. Or, you can
take advantage of RCA's convenient monthly
payment plan. No interest charges!

Classroom Training Also Available

RCA Institutes operates one of the largest technical
schools of its kind. Day and evening classes. No
previous training is required. Preparatory courses
are available. Classes start four times a year.
Job Placement Service, Too!
Companies like Bell Telephone Labs, GE,
Honeywell, IBM, IRCA, Westinghouse, Xerox, and
major radio and TV networks have regularly
employed gradLates through RCA Institutes' own
placement service.

All RCA Institutes courses and programs are

approved for veterans under the new G.I. Bill.
Send Attached Postage Paid Card Today.
Check Home Study or Classroom Training.
Accredited Member National Home Study Council.

REPLY CARD

IS

DETACHED, SEND THIS COUPON

RCA Institutes Inc.

Home Study Dept. 694 -010 -0
320 West 31 Street
New York, N.Y. 10001

CATV

Broadcasting
Marine Communications
Nuclear Instrumentation
Industrial Electronics
Automation
Computer Programming
Solid State
Electronics Drafting

7
IF

In the new program on Solid

Please send me FREE illustrated career catalog.

State Electronics you will study

the elects of temperature and
leakage characteristics of
transistors.

RC,'

Name

Age
(please print)

Address
City

October, 1970

www.americanradiohistory.com

State

Zip

J
21

Additional information on products described

in this section is available from the manufacturers. Each new product is identified by
a

PRODUCTS

corresponding number on the Reader Service

Page. To obtain additional infor nation on any

of them, circle the number on tl e Reader Ser

vice Page, fill in your name an address, and
mail it in accordance with the instructions.

-If

SONY REEL -TO- REEL /CASSETTE SYSTEM

you're in a quandary about the reel -to -reel vs cassette
debate, the Sony Model 330 provides a workable solution. Billed as a Stereo Tape System /Control Center, the
330 permits reel recording, editing, and re- recording to
cassette. Or, if you have too many bulky reel tapes, the
cassette may be your answer by simply transferring one
format to the other. Modestly priced, the 330 has 3 reel
tape speeds, dual VU meters, tone controls, separate
volume controls, headphone output jack, 5" lid -integrated stereo speakers and two cardioid microphones.
Adding a tuner and changer, you have a full complement
of a low-cost stereo system.
Circle No. 85

on Reader Service Page 15 or 115

UNIMETRICS MONITOR SCANNER -Simpl city seems

to be the keynote in the appearance of the nimetrics,
Inc. Digi Scan-8 VHF /UHF automatic sc
ing receiver. Only two lever switches are seen on the panel.
One lever sets the receiver up for scanning up to 8 preselected crystal- controlled channels or permits manual
channel selection. The second selects the ' ppropriate
channel after manual setup. Readout of the hannel being monitored is through a bright, segme ed digital
indicator. Manufacturer claims a 0.5 -V sen-itivity and
-60 -dB image rejection.
Circle No. 86

on Reader Service Page 15 or 115

SENCORE POWER MONITOR -Using the Sencore

PM157 Power Monitor, radio -TV technicians have a
new test instrument for solving problems concerning
excessive power drains. The technician first reads line
voltage on an expanded scale covering 65 to 135 volts
ac. Then the drain is measured and can be read in values up to 10.0 amperes and /or 1150 watts. The PM157
also contains a bridge circuit to permit measurement
of dc up to 10 amperes and /or a combination of ac and
dc, such as might be found in fuse resistors. In fact, a
separate scale on the PM157 reads the drain on fuse
resistors with the common values of 4.7, 5.6, 7.5, 9-10,
22, 47, and 100 ohms. The PM157 is protected by a cir-

cuit breaker.

Circle No. 87 on Reader Service Page

15

or 115

NIKKO "DO EVERYTHING" STEREO RECEIVER -A

recent entry in the American market, Nikko Electric
Corp., has announced its feature -loaded 1101 stereo receiver. Rated at 160 watts (IHF) at plus or minus 1.0
dB and 4 ohms (112 watts at 8 ohms) the claimed frequency response of the amplifier is 10- 70,000 Hz, also
22

POPULAR ELECTRONICS

Newest SAMS Books

Stereo Servicing Guide
by ROBERT G. MIDDLETON. A complete
Hi -Fi

guide to effective hi -fi and stereo servicing. Provides the basis for a full understanding of hi -fi tuner and amplifier
circuitry and procedures for servicing
this type of equipment. The proper use
of audio test and measurement equipment and the basic principles of acoustics are also given. Covers all hi -fi components (except record players and tape
$3.95
recorders). Order 20785, only
ABC's of Avionics
by LEX PARRISH.

'

Provides a basic understanding of avionics -the electronic

equipment used to insure the safety of
crew and passengers. The type of equipment and the techniques employed in
private aircraft operations are featured.
Discusses requirements for basic communications, navigation aids, instrument flight aids, weather guidance,
and flight control safety devices
$3.50
Order 20764, only

Security Electronics
by JOHN E. CUNNINGHAM. Explains the

Mobile -Radio Systems Planning

by Leo C. SANDS. Here is practical, basic

information about various types of

mobile-radio systems, how they work,

their capabilities and limitations, system requirements, licenses, channels,
band and frequency selection, transmitter- receiver selection, antenna systems, and accessories. Includes an invaluable system -requirements form for
planning a mobile -radio system
$4.50
Order 20780, only
Transistor -TV Servicing Made Easy
by JACK DARR. This practical guide will
help you become skilled ill the special
techniques of transistor -TV servicing.

Covers tools and equipment required;

transistors and transistor- servicing

techniques; power supplies; horizontal

and vertical sweep circuits; video i -f
and output circuits; age and sync -separator problems; tuners; audio circuits;
and selecting replacement transistors.
$4.95
Order 20776, only

operating principles of modern electronic devices and systems used to provide security against crime. Describes
intrusion alarms and intrusion- detection devices. Includes chapters on the
detection of hidden metal objects, announcement of detected intrusions, bugging, debugging, and speech-scrambling

systems, and future developments.

$4.50
Order 20767, only
How to Hear, Police, Fire,
and Aircraft Radio
by LEN BUCKWALTER.

After World War

II, police, fire, and aircraft radio moved
to the less crowded vhf bands, and the
"police band ", which was found in many
older radios, was silenced. Few listeners
had receivers capable of covering the
vhf band, because they were relatively
expensive. With the advent of solid state circuitry, a wide variety of relatively low -cost monitoring equipment
is available. This book is a guide to the
selection and use of vhf radio.
$3.50
Order 20781, only
Answers
About Transistor Circuits

101 Questions and

by LEO G. SANDS. Answers the most

commonly asked questions about transistor circuitry. Explains transistor nomenclature, biasing, the three basic circuit configurations, input and output
impedances, current and voltage gain,
and other basic considerations. Covers
power supplies and circuits; of circuits;
rf circuits, and oscillators.
$3.50
Order 20782, only

HI-FI STEREO

,,,07)}l,
(_

1 -2 -3 -4

.,,.

K+rf

p,we^imlor
sr

ru/tor

Aviation Electronics, 2nd Edition

by KEITH W. BOSE. This practical handbook for aircraft owners, pilots, tech nicians, and engineers explains the design, operation, and maintenance of
aviation electronics equipment. Covers
automa tic direction- finders, distance -

measuring equipment, omnirange, ATC

transponders and weather radar, com-

munications and instrument -landing

systems, and related devices and systems used in aviation today.
Order 20743, only

.ut

1-2-3-4 Servicing Transistor Color TV

by FOREST H. BELT. The "1 -2 -3 -4
Method" is a simple, logical, step -bystep process that helps do the service

job the right way and the easy way. In

this book, the fundamentals of transistor color TV are covered, followed by
a detailed explanation of how to apply
the method for quick troubleshooting
and easy repairs.
$4.95
Order 20777, only

North American Radio-TV

Station Guide, 6th Edition
by VANE A. JONES. Lists all

radio and
TV stations in the U.S., Canada, Mexico, and the West Indies. Includes operating a -m, fm, and television stations,
as well as those that are about to start
operating, or are temporarily off the air.
Separate listings arranged by geographical location, frequency (or channel),
and call letters make this guide the most
useful one available.
$2.95
Order 20779, only

HOWARD W. SA MS & CO., INC.

$9.95

Order from your Electronic Parts Distributor,

or mail to Howard W. Sams & Co., Inc., Dept. PE -100
4300 W. 62nd St., Indianapolis, Ind. 46268

Questions & Answers

on Short -Wave Listening

by H. CHARLES WOODRUFF. A helpful

guide to the interesting world of listening afforded by short -wave receivers.
Questions and answers cover interna-

tional short-wave broadcasting, frequencies, and services; how short-wave

is transmitted; how short -wave is received; and how short -wave receivers
are constructed and operated.
Order 20783, only

FOREST H. BELT. This book first applies the ingenious "1- 2 -3 -4" repair
method to both mechanical and electrical equipment. It then proceeds to
cover the electronic and mechanical
principles of automobile stereo, fm
multiplex and tape cartridge systems.
Finally, the book shows how to apply
the method to auto stereo systems.
Order 20737, only
$3.95

S1AAp*t r'1

.rav,n,.
esnnhilo
cltlv'tfr

Servicing Automobile Stereo

by

enclosed
Send books checked at right S
Send FREE 1970 Sams Book Catalog
Name

Address
City

State

$3.50
L
CIRCLE NO. 22 ON READER SERVICE PAGE

October, 1970

www.americanradiohistory.com

20785

20777

Li 20764

20767

20780

20781

20776

20782

EJ 20743

20737

20783

20779

Zip

23

NEW PRODUCTS CONTINUED

FROM ?ACE 22

at plus or minus

1.0 dB. Besides receiving AM /FM /FM

stereo, the Nikko 1101 has the following somewhat "different" features: VU metering in the stereo amplifier;
plus 10 dB speaker compensation at 30 Hz; stepped volume control for remote (second pair) speaker system;
rear panel patch cords to disconnect stereo preamp from
stereo power for insertion of special components; triple
circuit breakers; plug -in circuit board construction; etc.
All solid-state, the Model 1101 uses 6 FET's, 12 IC's,
25 transistors, and 22 diodes. Available in either a black
metal or walnut ($20 extra) cabinet.
Circle No.

88 on Reader Service Page 15 or 115

HARMAN - KARDON CADS CASSETTE: RECORDEROne of the chief complaints about casse tte recordings
has been the presence of high- frequency n ise. The Dolby
noise reduction system, a technique rece tly introduced
to get rid of a lot of this noise, is an in Legral part of
Harman- Kardon's CAD5 tape cassette d ck. It is said
that the system extends the frequency re ;ponse of cassettes to beyond 12,500 Hz. The CAD5 can play standard
tape cassettes or Dolby processed tapes v 'ithout special
adjustment and the Dolby controls (per channel) can be
set for special tapes. An electronic speed control assures
minimum speed variation and professional -type sliding
potentiometers set the recording level.
Circle No.

89 on Reader Service Page 15 or 115

ABPHOT AC VOLTMETER Measuring low -level signals in audio equipment is made easier with the Model
1001 Electronic Analog Voltmeter, a solid -state instrument with a range of 30 microvolts to 100 volts in the
frequency range from 10 Hz to 1 MHz. Sensitivity is
300 microvolts FSD and internal noise is typically -108
dBm on the 300 -microvolt scale. Battery operation eliminates troublesome ground loops and beat effects while
making measurements in the vicinity of the line frequency. Accessory Series 900 plug -in notch filter makes
possible measurements at spot frequencies. These RCL
bridged -T networks plug directly into the meter.
Circle No.

90 on Reader Service Page 15 or 115

PIONEER AUTOMATIC -TUNING RECEIVER

- The

ultimate for dial twisters is Pioneer's AM /FM/FM

stereo Model SX -2500 receiver with precision automatic
tuning. With a 340 -watt ! IHF) output, th receiver can
be set to hunt out strong local stations r weak stations or to stop only on stations broadcas ing in stereo.
A muting level control permits the listene to determine
the amount of muting beween FM stations The SX -2500
also has a remote control unit for automa 'c tuning and
volume control from distances up to 23 eet. The FM
front end tuner uses FET's, IC's and crys al filters and
has a sensitivity of 1.6 microvolts per meter. Selectivity
is 65 dB at 98 MHz and signal -to -noise ratio is over 70 dB.
Circle No.
24

91 on

Reader Service Page

15

or 115
POPULAR ELECTRONICS

check

your CB rig's
performance
10 ways...

Suggested list:

$49.95

Johnson's new transceiver tester.

Does everything other testers do

...

and more! Reads power output in

actual watts. Reads modulation
directly in percentage And lets you
hear what your transmitted signal actually sounds like, with the headphoie
monitoring jack! Also can be installed
to read received "S" units. Constantly
monitors your rig while you're on -theair. Flip a switch and you can make

tests using the built -in dummy load.

There are built -in RF and audio generators, crystal activity checker, SWR
peter, and more -so you can pinpoint
problems like a professional. Battery
cperated and portable, it even has a
field strength meter that's great for
making comparative checks at jamborees. No serious CBer should be
without it!

Other Johnson Accessories for the Advanced CBer

NEW

,,.
CB MATCHBOX
ANTENNA TUNER

;15.95

..

NEW

r T14

CB ANTENNA
METER ;14.95

f F'.'

NEW

ANTENNA MATE
TUNER AND SWR
METER $29.95

RECHARGER' BASE
POWER SUPPLY FOR
HAND -HELDS $28.00

E. F.

CB MOBILE
SPEAKER ;13.00

JOHNSON COMPANY
W A

CIRCLE NO. 1S ON READER SERVICE PAGE

25

October, 1970

www.americanradiohistory.com

Now it costs less

to owe the best
oscilloscope you need.

*Inexpensive Quality
/Optional Distributor.
Resale Price

The New RCA WO -505A Solid -State Jscilloscope

The best you need is the new 5 -inch RCA WO -505A,

all solid -state oscilloscope. It makes yesterday's
general -purpose 'scopes look old- fashioned.
At just $298.50t the WO -505A offers an unmatched
list of features usually found only in more expensive, laboratory -type instruments. For example
there's the all solid-state circuitry... an illuminated
graph screen calibrated directly in volts, and a
deep -lip bezel for exceptional clarity. The regulated power supply minimizes trace bounce and
provides excellent stability. And the camera mounting studs offer still more evidence of the functional
value built into the new WO -505A.
But you've got to see this new RCA 'scope in
operation -see the sharp, clean trace it provides
to appreciate it.

into

Some statistics:
High- frequency response, usable to 8 MHz.
High Sensitivity (.05 V p -p range).
DC vertical amplifier; DC/ AC nput.
Return trace bianking...Trace polarity reversal
switch ... Phase control.
High- frequency horizontal sweep; solid lock -in
on 5 MHz.
Preset TV "V" and "H" 'frequencies for instant

lock-i n.
Built -in square-wave signal for calibrating P -P
voltage measurements.
Provision for connection to vertical deflection
plates of CRT.
Some statistics! For complete details, contact
your RCA Distributor.
RCAIElectronic ComponentsjHarrison, N. J. 07029

CIRCLE NO. 20 ON RE ADER SERVICE PAGE

26

POPULAR ELECTRONICS

,C4

L.,Ztte4b;cn/

LCG.e4i
/2
WHO DID INVENT RADIO?

BY FRED SHUNAMAN

IN ALL PIiOIiABILITP there

xvill never be
total agreement on the question of who actually discovered radio. In fact, the word
"radio" itself sloes not stand up to a strict
historical interpretation. Does the "first radio"
mean the first two -way wireless communication? Or a one -way wireless transmission?
Or would a minor laboratory demonstration
and a patent establish the precedency of the
discoverer /inventor?
In one way or another, Marconi, Popov,
Loomis, Butterfield, Lodge, Hertz and Tesla
all quality as discoverers of radio. However,
history now shows that none of these men has
the supporting. evidence of discovery that belongs to Thomas Alva Edison -to whom the
honor Inlay right fully belong.
A simple language difficulty may have cost
Edison the credit for first discovering and using. radio as a means of communication. He
announced the discovery of "etheric toree"

vhen Marconi was only a year old and while

Tesla was still attending school. And, in 1885,
two years before Hertz announced the discovery of electromagnetic waves, Edison applied for a patent on a complete wireless system. Submittc.l with his application were
patent drawings of radio towers and antennas
on the masts of ships.
How It All Began. During the evening of
November 22, 1875, Edison was studying the
action of a ni: gnetic vibrator. He noticed a
tiny spark between the armature and core of
the vibrator as the armature approached the
core. Suspecting faulty insulation, he checked
the coil but found everything in order.
However, Edison reported that "If we
touched any part of the vibrator we got the
spark," and that "the larger the body of iron
touched to tlic vibrator, the larger the spark."
If a wire was connected between the vibrator
:

27

October, 1970

www.americanradiohistory.com

Above is one of the drawings from Edison's Patent No. 465,971, Dec. 29, 1891,

describing a "Means for Transmitting

Signals Electrically." Particularly interested in transmitting across bodies of
water, he showed high towers and ships

carrying "condensing surfaces" (which

we would call antennas). At the right
is an enlargement of the insert, in which
Edison described how signal was generated and transmitted to antenna.

28

POPULi,R ELECTRONICS

Edison's "black box" 1881 demonstration had

graphite points which could be connected to
an external circuit. The extension eye -shade
permitted viewer to see, jumping between
the contacts, sparks unlike any known to
an electrical phenomenon at that period.

and a gas jet on the wall, a spark could be

drawn from the gas pipes anywhere in the
room.
Then Edison performed the experiment that
Hertz was to do 17 years later; he found that
"if you turn the wire round on itself and let
the point of the wire touch any part of itself,
you get a spark.... This is simply wonderful
and a good proof that the cause of the spark
is not now known force."
Next, Edison constructed a demonstration
apparatus and revealed his new setheric
force" to the Polyclinic Club of the American
Institute. Many of the members seemed upset
by the name he had chosen for the new effect.
But Edison was undaunted, and he predicted
(in the January 1876 issue of the Operator,
a telegrapher's magazine) that the new force
might become the telegraphic medium of the
future. IIe is quoted as having stated: "The
cumbersome appliances of transmitting ordinary electricity, such as telegraph poles, insulating knobs, cable sheathings, and so on,
may be left out of the problem of quick and
easy telegraphic transmission, and a great
saving of time and labor accomplished."
The Scientific American of December 1875
stated : "By this simple means signals have
been sent [by wire] for long distances, as
from Mr. Edison's laboratory to his dwelling
house in another part of the town. Mr. Edison
states that signals have also been sent the
distance of 75 miles on an open circuit, by

attaching a conducting wire to the Western

Union telegraph line."
As It Developed. A "black box," used by
Edison to demonstrate etheric force was sent
to Paris where Edison's assistant, Charles
Batchelor, lectured on the etheric force. ( The
black box detector consisted of a pair of
adjustable graphite points in a shaded enclosure, with terminals to attach it to an external circuit.) There is a bare possibility
that Heinrich Hertz might have heard about
Edison's experiments, for his spark points
with the micrometer adjustment are virtually
identical to those in the black box, and he
repeated the experiment of turning the wire
back upon itself.
Work on the telephone took Edison's attention away from etheric force for some time.
But in 1885 he applied for a patent for a
wireless telegraph system based on his etheric
force. The patent drawings show towers that
are easily recognizable as radio masts, and
two ships with broad ribbon-like antennas
hung between their masts! The text of the
patent application goes into detail about the
equipment shown in the drawings.
"The wire (from the `condensing surface'
C) extends through an electromotograph
telephone receiver D (Fig. 2) or other suitable
receiver, and also includes the secondary circuit of an induction coil F. In the primary of
this coil is a battery b and a revolving circuit-

October, 1970

29

www.americanradiohistory.com

Thomas A. Edison, from a print dated

1877, about the time he was working on
his "etheric force" invent on. This and
other illustrations in this article are
adapted from those appearing in "Menlo
Park Reminiscences," Vol. I, by F. Jehl,
Edison Institute, Dearborn Park, Mich.

...

is short breaker G. This circuit -breaker

circuited normally by a backpoint key K, by
depressing which ... the circuit -breaker makes
and breaks the primary circuit of the induction coil with great rapidity," Edison wrote.
Explaining the phenomenon as he saw it,
Edison went on to state: "These electric impulses are transmitted inductively to the
elevated condensing surface at the distant
point ..."
Here is where the confusion in language
occurred. At the time, the term induction, un-

less otherwise explained, meant electrostatic

induction, (a tendency that still lingers on in
some elementary physics textbooks). The
transformer had just been invented, and magnetic induction was a laboratory curiosity.
The term "electrostatic" drifted into obscurity as the art progressed, and later writers
referring to the "induction telegraph" unquestioningly accepted the term to mean mag-

netic induction.
The confusion was increased because the
only commercial use Edison made of his invention was the "grasshopper telegraplI," a
system of telegraphing from moving trains
to the telegraph wires alongside the tracks.
This was a distance that could be covered
easily by electromagnetic induction, and historians who believe that radio communication
started with Tesla, Lodge, and Marconi assumed that this was the case. Yet, in explaining the "grasshopper telegraph" to a reporter,
Edison said, "The system works by electro-

So, a change in the genera lv accepted

meaning of a word with the changing times
buried the fact that Edison i'ventecl, described, patented, and operated a radiotelegraph system in 1886 -a year efore Hertz
explained the cause of the etheric force, which
he called electric force.
What other "firsts" may lay cried or attributed to other discoverers becai se semantics
denied the original inventor or c iscoverer his
due ? At least now Thomas Alva Bison's long
list of achievements will have nu bered among
them the discovery of radio way s -even if he
did not title them as such.
-[31

Editor's Note: We are given to understand

that the graphic -points "black t ox" is still
in existence and has been exhit ited on the
second floor of the restored Edi son Laboratory.
In his book, "Menlo Park Rer iiniscences"
(now believed to be out of prin and unobtainable), author Jehl says that Edison was
intrigued by the spark and perform ed many experiments to seek an explanation If its nature.
Edison did find that the spark was unpolarized;
had no respect for the usual typ s of insulation; would not discharge a Ley( en jar; and
had no effect on his electroscope s.
Unquestionably, Edison had st imbled onto
radio -wave transmission, but tt e fact that
energy could be propagated throug i the atmosphere and not via wires was ali rn to all of
his telegraphy experiments.

static induction."
30

POPULA

ELECTRONICS

BY

DAN

MEYER

Assedlini a

UNIVERSAL

El
This power amplifier design is the
culmination of various "Tiger" amplifier projects developed key the same
author. It is virtually indes- ructible and
our exhaustive tests reveal that no combination of input- output mismatching
and short circuils can cause amplifier
failure. The performance specifications
equal or better numerous commercial
quality hi -fi power amplifiers.

f/

A UBIQUfTOUS, 125-WATT-

PER-CHANNEL DESIGN

..

sllt

And th's mil all. No evterua I;td,

circuit,
input condition can :ni>e anplt,t%
fier failnre The nnrsi dial will nippe is :i
blown fusc. Thennnl aal)ilitk"
1l1,1i
the output transistur, olternte illi ,. hent
sink tempctatnre of 1
l' rtlie
poiiit.
fettdeneF to
of Water) Witlt
\or is the-' any darezer ot sIi,tJcer
due to a -t rtitt_ transient since Mile re nu
latee ea}t,'iiurs iu Ile cittenit that tutit
elyr,e tilt b2'fore u+rutal H1erntiot can
trued on ::
NN"hen the Universal 'l'i_tr is
small (diel; ir ltean-d in the speaher
then. ipslau >ount'.
t

Rowel amplifier ca t be all tltin s

to all men. Inn. tht "I nitrr.sal Tir'er''
come; ell sir to floe ideal flu t- Von nti2ht
think. Consider the folio roar: The on- put
power of the i" ti--ersxl firer eons he set to
any level ':etwtwn 10 and 12) watts rmr/
catannel by conneMi.r.4 ro the atsalifier circuit
an appropriate p r.Ver supply- (12-40 volts
de). Over the aa i spi ct nun. distortion is
never motel-Ilan (toe and it e.11 be reduced
to less that_ 0,'). at The user's option. The
bandwidth bet,ceen the :l -dl] d_csn points is
1- 100,000 Hs!
Nil

Construction. The riNer lid colt;c

amplifier s acte t,t the t(iora Ti_er are
assembled o.n a ltrinted circuit
the actual sire 4iin1:: guide and c(tnllx ntrnt placement diat;rain for which are. ;hoc,i in E itf. 2.
The cirenit board is Flesia-tred
match the
space reytvirentents of the "Super
(see "Tigeas That Pcaa.'' l'or-t--,Ar,
Tao:lec, .Jnh 19114) so that huilters of the
earlier project can easily update it.

Octcber, 1970

t=.

31

www.americanradiohistory.com

The chassis and power supply for the

Super Tiger can also be used with the Universal Tiger if no more than 80 watts mono
or 60 watts /channel stereo output is desired.
If you want a lower output power, one of the

low -voltage transformers listed in the sidebar

should be used. And with a 4 -ohm load and a
heavy -duty power supply (see Fig. 3) for
each channel, a 125 watts rms/channel stereo
system can be built.

0+

10

to

V
_LL

H"
U3

LL

MOZ
UU

32

LL

0
QO

NO
E

POPULAR ELECTRONICS

The power supply circuit is simple and

straightforward. However, depending on the

amount of power you want from your amplifier, you will have to select the prolog secondary voltage -current rating for transformer

PARTS LIST
AMPLIFIER

CI.CS- 220 -p! rainy

C2-220 -F,

6.3-volt electroIvtir capacitor

C3.C4- 1000 -pF rapari1or

C5- C7.C9---0.1 -F capacitor

C10- C12-0.l -F alise capnritnr
D1 -4.7 -volt zener dinde (I V'4732 or FIEP602)
1)2,D3- IN3754 or IIEP 156 silicon diode
F1
ampere standard-NOT slow-blow-fuse

-5

J1-Phono Jack

Q1,Q2,Q9- MPS-6566 transistor

Q3,Q6- Transistor (RCA 40410)

Q4,Q5- Transistor (RCA 40409)

Q7- Transistor (Motorola MJ4502)

Q8- Transistor (Motorola MJ802)
R1,R5,R7-2200 -ohm, -watt
R2- 20,000 -ohm, -watt
R3 -4700 -ohm, -war
R4- 18,000 -ohm. -watt
All resistors
R6 -1000 -ohm. ? -watt
R8- 150 -ohm, % -rcatt
10% tolerance
L.

L_

L_

R9,R10-390 -ohm, L_ -watt

-100 -ohm, ? -mou

R17 ,R18-0.1-ohm, 5 -watt
R 19,R20- 10-ohrn, 1 -watt
R21 -50 -ohm potentiometer
1111 -R16

Misc. -Steel chassis (6" x 11") ; Wakefield

Semiconductor No. NC403C or Thermalloy
Co. No. 64038 heat sinks (2) ; two -lug ungrounded terminal block; four -lug terminal
strip; 22-18-gauge aluminum stock for U
and L brackets; #18 or larger stranded

hookup wire; fuse holder; #6 and #4 machine hardware; diode clamps (2); solder
lugs (2); three-lug terminal strips (2):
transistor mounting hardware; solder; eta.
Note -The following items are available from
Southwest Technical Products Corp., 219
West Rhapsody, San Antonio, TX 78216:
circuit board (No. 175B) for $2.75; complete amplifier as listed, but excluding chassis (No. 175C) for $30 plus shipping and
insurance on 3 lb; complete stereo version
with punched chassis and power supply (No.
2S -175) for $80 plus shipping and insurance
on 17 lb; complete single- channel version
with punched chassis and power supply
(No. S-175) for $60 plus shipping and insurance on 14 lb.

and the current rating of fuse F1 from

the table in the sidebar.
The power supply mounts directly on the
steel chassis that accommodates the amplifier
circuits. Point -to -point wiring is used
throughout, but be extremely careful during
wiring to make sure diode and capacitor
polarities are correct.
Since the physical layout of the Super
Tiger was presented previously, this article
will focus on the construction of only the
125 -watt mono version with power supply.
Unless you purchase the steel chassis with
the complete kit from the source listed in the
Amplifier Parts List, you will have to machine your own, using the photos given in this
article to guide you.
After mounting and soldering into place
the components on the circuit board, solder
8" lengths of #18 or larger stranded hookup wire at hole locations C and D from the
foil side of the board and at locations G,
GND, E, L, F, and K from the component
side. Twist together 21/2" lengths of black and
white wires. Solder the black wire to A and
the white wire to B on the component side.
Then mount the circuit board in its proper
location on the chassis.
At the opposite end of the chassis, anchor
the power transformer with #8 hardware
and the filter capacitors with #6 hardware.
Fasten the power supply primary fuse holder and line cord with strain relief in their
appropriate holes on the rear apron of the
chassis. Then bolt down the secondary fuse
block and the terminal strips associated with
T.1

TECHNICAL SPECIFICATIONS
Output power: Up to 80 watts /channel with
8-ohm load; to 120 watts /channel with
4 -ohm load

Distortion: Less than 0.5% from 20 to 20,000

Hz standard; less than 0.05% from 20 to
20,000 Hz with optional low distortion adjustment
Frequency response: 3 dB down at approximately 1 and 100,000 Hz
Hum and noise: Better than 80 dB below 1
watt rms output
Damping factor: Better than 100 with 8 -ohm
load

Fig. 1. Circuit of power amplifier is simple

and foolproof in design. Note absence of "weak
link" large -value capacitors. Two such ampli-

fier

circuits are required for stereo system.

Sensitivity: 1.5 volts rms input for full output

Stability: Completely stable with any source
impedance; can be used with any load impedance as low as 3 ohms or capacitive
loads to 1F.

October, 1970

33

www.americanradiohistory.com

GND

0,0o 0
G

On R13 NO

C3Rii

05

R12

R14

C610

0-R11 NO

Q4
R16C4

O D O

b
C2

it
+

Q3

R7

C8

R8

bb

02

o
R11J

vie

0-1

Negative dc supply voltage is taken

from right side of F2. Table lists ratings
of F1 and T1 for desired amplifier output.

01

O'

Qt

o
o

me

o-

R3

O.' R2.4O

VO /--45(19

c104)"R1um0

O
A

125W"
80W
40W
20W
10W

COW )NENTS
Ti secondary

SUPPLY
F1

Voltage

DC

Current
2.6A
2.6A

& Current

Output

1.5A
1.0A

4EVct.2A

1.0 A

2x1.Vct,IA

62Vct,3A

40

62V et, 3A

40
28

34 V ct

1.5

`Af -i-uhnt lnad: all othtvc tur,r,

turrl + ti-hrt G,rt iniheriarr'e.

20 V
--15V

ratings ref-

POWER SUPPLY
PARTS LIST

TI - --1!7 -colt primary (see table for secondary

voltage and current ratings) power trans-

Cl.C2- 4000 -pF. 50 -roll electrolytic capacitor

C1 -200 thermostat (No. L200 88 -4, avail-

Misc. -Fuse holder: fuse block; ac line cord

with plug; line cord strain relief; #18 or

able for $5 from Elmwood Sensors, Inc., 1655

Elmwood ,4re. Cranston. RI 02907)
PI -Slow -blow fuse (see table for rating)
F2-5- ampere standard -NOT Slow-blow-

fuse

IiE(.TI -- Full -wave bridge rectifier assembly

(Motorola AID- 1962-3). or .substitute four
3- ampere. 200 NV silicon diodes

34

Fig. 2. Actual size etching guide is shown at

left. In component layout and orientation diagram (above), boxes around Q3 -Q6 represent
outlines of heat sinks on these transistors.

Power

Fig. 3.

R6

0R5'11&42 o

Output

F2

O-C9,

OR4

POWER

L--

'

OC

former

larger stranded hookup wire: #6 and

#8 machine hardware: two-lug -neither
grounded--terminal strips (2) : five lug
center lug grounded-termin.cl strip; solder: etc.
Note
above items available from SottthI est Technical Products Co. o part of kits
-17.5 and 2S -175 (.;ee Amplifit r Parts List).

-ill

POPULAR ELECTRONICS

Fig. 4. Power supply secondary

fuse and bridge rectifier assembly diodes mount on fuse
block and terminal strip. Resistors R17 and R18 connect
output of power supply to Q7
and Q8 in amplifier circuit.

over supply (see Fig. 4) Now, referring to Fig. 3, wire together the power sup ply circuit, using #18 or larger stranded
hookup wire. (Note: Where #18 or larger
wire is specified, do not substitute a smaller
size wire. The circuits to which these wires
connect carry as much as 10 amperes when
the amplifier is driven to full power. If too
small a wire size is used, power will be sacrificed and clamping will s.i fer.)
Returning to the amplifier end of the chassis, mount input jack J1, the speaker fuse
holder, and the output terminal block on the
front apron. Solder the white wire from fiole.
B on the circuit board to the center contact
of J1 and the black wire from hole _1 to the
the

if

other lug on J1. Bolt a four-lug terminal

strip (one lug grounded) to the chassis at the
right of the circuit board and in line with the
speaker fuse holder.
Close -wind one layer of $26 enameled
wire along the entire length of the body of
R10 (10 -ohm, 1 -watt resistor). Scrape the
ends of the wire and solder them to the leads
of the resistor. Then solder one lead of this
L1/1?19 assembly to the center lug on the
output fuse holder and connect the other
lead to the lug nearest the fuse holder on the
last terminal strip mounted.
As shown in Fig. 5, connect C5 and R20
to the terminal strip near R19/L1. Solder
only the ground lug that serves as the tie

WI NMn/MN

,41g3,
l'wok

iassmar.

tp
FI

LI /R19

R20

C5

QE

Fig. 5. Close -wind a single layer of .#22 enameled wire along the entire length of
R19 and solder the wire ends to the resistor leacs to make the D_1 /R19 assembly.

October, 1970

3$

www.americanradiohistory.com

NTS aufs a whole new

NTS home training can put a
whole new way of life in the palm
of your hand. A new, exciting job,
a much bigger income is now
easily within your reach.
NTS training is something special. We provide all the kits you
need for the most effective training. National Technical Schools
sends kits with every course, and
teaches you to build and test a
36

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39

October, 1970

www.americanradiohistory.com

1.0

-- --

UNIVERSAL TIGER

0.5

0.2

lr
TEE-

E_a__' ::
1=

F.?

01

p.05

11111

NmemEel!k.1!

gE1i117

.01

.005

MEN
wlnlnliiiiiiiwrr

rlNlpgNW

.,

`:
tlWC6i13Ett{t

..

MIEC;$REMERR_

3g111P

1=9:

l51il5ZIgs5agg101111HUIRlwNIegigIOvWi3
RRIENgINISt0EE=11&11ffilllMMIiKRLIE`__

:_

MBEEffigiEg

- waluwlnawuneumlxalx,u
-MNIMYIMIxIa k[IpxaWpiiY
iC511AAr4 3YIg11YNlxitlffi1NI1

.02

REFERENCE POWER If
-LOW POWER(
-HALF POWER( -:

r+
M onrurllnuul
1Mnmlm
/11x&2AF1WIx6:sA
11=1!l11111111111I511NA2g4l2115135V
InglinnifiligiliERSEZAg'
AM9MOIIN

--

KaligMEMENEME_IlEg=
YE4auWi;r=1Mxtmam,s
txliailtNN.EE5:

.002
20

50

100

200

IB$REi:i=
500

2K

IK

5K

IOK

20K

FREQUENCY IN Hz

HIRSCH -HOUCK LABORATORIES

Project Evaluation
This is a very impressive basic amplifier for a home -brew project. The schematic diagram of the "Universal Tiger"
is reminiscent of the new Harman -Kardon
"Citation 12," with an operational amplifier input configuration and overall direct coupled feedback to maintain the speaker
at dc ground. However, unlike the Citation
12, the Tiger uses complementary symmetry output transistors, and opposite
polarities on the other transistors.
In general, we confirmed Mr. Meyer's
specifications figures. Where he claims a
0.01% or less distortion under most op-

erating conditions, we feel that he is a

he certainly comes
close. At 80 watts, the distortion is typically less than 0.05% from 70 to 17,000
Hz, rising to slightly in excess of 0.5%
at 20 Hz. At half power or les , the distortion is typically less than 0. 2% from
20 to 20,000 Hz.
At 1000 Hz, distortion alls from
0.15% at 0.1 watt to a mi imum of
0.009% at 20 watts and rise to 0.1%
at 85 watts, which is just bel
clipping
level. These powers were mea ured with
an 8 -ohm load and a 117 -volt line.
Intermodulation distortion ias slightly
higher. But at most power levels greater
than one watt, it was less than 0.1 %.
We did not have enough voltage from our

trifle optimistic, but

IM

analyzer to drive the amplifier to more

point for both C5 and

1120. Te porarily set

aside the chassis assembly.
Spread a film of silicone pas e on the bottorn of the case of Q7 (\1J45 2) and slip
onto the pasted side a mica insu ator. Spread
another film of the paste on on of the heat
sinks in the area over which Q7 is to be
mounted. Then seat Q7 on tl e heat sink.
Push a #4 machine screw throu h the mount ing hole tabs in the case of t ie transistor,
turn over the assembly, and sl. e onto each
screw a shoulder fiber washer. J ake sure that
the shoulders engage the oversi holes in the
heat sink. Then place a solder lug over the
screw nearest the edge of the he t sink and a
three-lug terminal strip and
diode case
I

When mounting Q3 -Q6 on printed circuit board,

make certain that triangular lead configurations and
heat sink tabs line up with holes in circuit board.

40

POPULAR ELECTRONICS

UNIVERSAL TIGER

---- 60 /7000Hz

IkHz TOTAL HARMONIC DISTORTION

(4:HIM DISTORTION

..

.005

.002
01

MIMI

iiii
..,
=C....,
Irln!>i

11111I1i

INIiM

II.,
............,

iaMZq
"AM
Nrmull.111111113
INIMMI

p
N1i

50
10
20
5
0.2
05
2
CONTINUOUS AND EQUIVALENT SINE -WAVE POWER OUTPUT

than 40 watts. These figures were measured with the bias adjust control set as
received with best thermal stability. The
low -level distortion could be reduced substantially with this control set at its opposite limit, where the measured reduction
was from 0.045% to 0.023% at one watt
and from 0.15% to 0.047% at 0.1 watt.
However, it is hardly worth the bother to
play with the bias adjust control, since
we doubt that many people have the test
equipment needed to make the adjustment.
Into 4 ohms, the maximum power at
the clipping point was 97 watts; into 8
ohms, it was 92 watts; and into 16 ohms,
it was 53 watts. An input of 0.9 volt was
needed for a 10 -watt output (our standard
reference level) and hum and noise were

10

86 dB below 10 watts -a very low figure.

The frequency response of the Universal Tiger was 0.2 dB from less than 10
Hz to beyond 20,000 Hz. It was down 0.3
dB at 5 Hz and 50,000 Hz, and the higher
end was slightly better than claimed.
being down 1.1 dB at 100,000 Hz and 3.9
dB at 200,000 Hz. Square wave tests
showed a rise time of about 2.5 microseconds.
In all, the Universal Tiger is one of the
best power amplifiers we have had the
pleasure of testing. Short- circuiting the
output at full power blew only the speaker
fuse, while full power square -wave drive
at 100,000 Hz blew only the power supply
fuse after a few moments. But nothing
seemed to damage the amplifier circuit
itself.

over the other screw. Fasten the

screws with appropriate nuts. Use #4 hard ware tu bolt. ('111 in place.
Ilepeat the above procedure for the second
heat sink and QS with the following changes.
(.181111)

Anchor only the diode clamp and solder lug

to the hold -down screws for (,)Y. \boot R21
on an L bracket and fasten the bracket and a
three -lug terminal strip to the Heat sink with
#4 hardware and shoulder fiber washers.
Slide 112 and TE into tige diode clamps and
push unto the diode leads 1." lengths of plastic tobin. Connect the leads to the an ioxtldrl! Ins of the terminal strips. `older a 10 "Ilne, wire to the ln, to which the anode lead
ut' U3 is connected and a 1" wire from lug 3

In upper waveform, crossover distortion at base of

Q4 can be seen; lower trace shows undistorted waveform (F =1000 Hz at 0.25 watts into 8 -ohm load).
41

October, 1970

www.americanradiohistory.com

THEORY OF CIRCUIT DESIGN

The circuit of the Universal Tiger is a combination of operational amplifier and contplcntentary output techniques. As -ho%n in Fig.
1. transistors Ql and Q2 form a differential
:nnplifier. The input signal i- applied to the
hase of QI. with negative feedback on the base
of Q2.
Zoner diode DI maintains a constant bias
voltage on Q9 so that the current is constant
through the base- emitter circuit of the transistor for any supply potential exceeding -1.7
ohs. Hence. the Q9 circuit functions as a
,vitestant- current source for Q and Q2. Since
(:2 provides for 100 percent negative feedback
on the
in the circuit. the output voltage offset
ruder of a fete millivolts: any unbalance is immediately corrected by the QI!02 differential
-tage. And the ratio of R7 to 178 determines

the amount of overall ac negative feedback.

Note that C2 is the only element in the cirt

nit that prevents the amplifier from respondlog down to dc

From the collector of QI. the amplified signal goes to the base of Q3. Normally. Q3
Mould he the voltage amplifier that supplies
the large voltage suing needed to drive the inlpedance- matching (Irkeriocutput ciruit. here.
however. it is limited in voltage gain :std.

uorking with QI. it provide- some unique

ha raileri-tics.
In most of the common amplifier circuits.
the voltage amplifier load n -istor is split I as
in Fig. Al. and a "bootstrap" capacitor is connected to the output. This cas -es the voltage
tcrnss collector load resistor Rr, to remain at a
on -tant value so that collector current is con -hint. If a con- tant -current circuit were not
used. the amount of current available to drive
the output circuit would drop to zero as the
to-itive peaks of the waveform approach the
teak positive potential of the power supply.
This would result in a con- iderable amount of
distortion on positive peaks that would be
difficult or impossible to ironed no matter
bow much degenerative feedback sas used.
in the circuit of the Universal Tiger. an active current source is used instead of the more
common bootstrap system. The results are the
saune with one important exception. The driver
is not affected by supply voltage variations,
due to the use of a constant load resistance.
and a solution is provided for the crossover
distortion problem because the active current
source supplies a constant current to Q3 at all

lines. The bootstrap circuit, obviously, does

not.
Consider what happens if a portion of the
output waveform is flat. as from .1 to B in Fig.
R. due to an underbiased condition in the output stage. During this portion of the cycle.
there is nn increase in output voltage. and. as a
42

result. no bootstrap action by tIhe capacitor.

.111r1 during this time the circui tldoes not provide the driver transistor with w constant current. \With the active curent so t rue. this does
not occur.
The active current source acts ally eliminates
most of the crossover distortion I at can occur
due to an uuderbiased conditiot t,tn the output
circuit. \\re vaut see why- if we c outsider what a
constant current source does. ft adjusts the
voltage to keep the current thro jgh the circuit
constant. But what happens if a underbiaserl
condition exists in which Q5 aux. dfi Q6 are both
cut off?
1s the driving voltage approa whys zero, the
active di iver begins to turn off. lut the voltage
is not vet sufficient to cause the other driver to
conduct. The loading on the cmr 1+ent source beroutes far less during this pc rind since no
ru recut ran be supplied to cille r driver while
both are cut off. Hence. the cur rent source increases the voltage in an attem pt to maintain
a constant current through the amplifier circuit. And the driving voltage jan a- very quick ly from the cutoff point of one driver to the
conduction point of the other d iver. resulting
in the minimum of effect on the ont put wave
forni during the crossover periodI,
In a crase like this. !Ito bias in the output
stage would normally be adjust(d so that both
output transistors are conductin at a low level
to avoid crossover distortion. I-I fwcver. if it is
possible to avoid having to oak e a critical bias
adjustment. so much the better. Without making this adjustment. a considers de problem in
thermal stability will result. As he transistor's
temperature increases. the saur bias voltage
w ill cause a considerable increa t e in collector
current. opening the way to p sihle thermal
runawai. The use of diodes 1)2 and 03 in the
Universal Tiger provides art tnatic adjustment which helps to climinat the thermal
problem.
The diodes are actually nous ed on the heat
sinks used for Q7 and Q8. Now r any tempera tore changes in the output trail -istors are dcteeter] by the diodes. whose rr -istances var
with temperature. As the dio le resistances
change. so do the bias voltages to driver bran si-lors Q5 and Q6. 1hnee. if Qr and Q8 begin
to operate abnormally hot. the iodes increase
the bias voltage to 05 and Q6 and indirectly
lower the operating tempera tun of Q7 and Q8.
There are two types of con round connections commonly employed in th output stages
of transistor power amplifier -. T te-e are shown
in Fig. C. The qua- icomrlenti rotary circuits
which use only one polarity of power transistors have one of each type ie their output
-huge. The doable emitter fol lo Iver compound
system requires two diode drop s to bias it on,
while the double common cmi ter compound
requires only one diode. This is a slight adI

POPU.AR ELECTRONICS

i
o

B
vantage since one less diode must be included
in the temperature- compensated bias network.
Neither compound has any voltage gain;
both require a driving signal voltage swing
equal to the needed output. Since the common
emitter driver compound at the right in Fig. C
has 100 percent degenerative feedback, gain
matching is not required in the output transistors, just as in the double emitter compound
also shown.
Comparison of the two circuits as a power
output stage gives the circuit at the right a
slight advantage in lowest distortion and other
areas if the circuit has overall negative feedback.
While testing a full complementary circuit
using the common emitter compound. it appeared that there was really no reason why
100 percent degenerative feedback should be
necessary or even desirable in the driver transistor. With a complementary circuit it is not
necessary to rely on a double emitter follower
for half of the output -which requires a second half with matching drive voltage requir ments. A complementary circuit alines the use
of any amount of degeneratine feedback from
zero to 100 percent in the driver portion of
the circuit. A circuit w ills no degeneration can
provide the maximum amount of voltage gain
from two transistors, but it requires matched
gain, in the output transistors.
Since there is plenty of gain available elsewhere in the circuit of Hie Universal Tiger. a
50 percent feedback arrangement was selected
for the driver stage. This gives a gain of two
in the output stage and enough feedback to
make transistor matching unnecessary.
The gain of only two might appear to be too
null. but it does provide several substantial
benefits. First, the peak -to -peak drive voltage
,'yl,irsion need be only half that of the peak

supply voltage This simplifies design demands.

Second, it is possible to keep distortion down
to hutch lower levels in the driver circuit if it
does not have to develop full supply positive
and negative excursions. Additional temperature stability, by using 50 percent feedback in
the output stage, is yet another advantage.
Even without the current drive system, the
circuit of the Universal Tiger would have been
many times more stable than circuits employing 100 percent degeneration in the driver.
Another bonus is that the output stage is virtually failure hoof.
If the output of the circuit in Fig C is short
circuited, or too low an impedance load is connected to it, he driver transistor would attempt to put enough current through the base emitter junction of the output stage to bring
the voltage up (due to overall feedback effects). This can cause the collector current
rating of the driver transistor or the base
emitter rating of the power transistor, or
both. to be exceeded. The same thing can also
happen in the second circuit, but in a slightly
different mariner; therefore elaborate protection circuits must be designed to prevent this.
This situation cannot occur with a 50 percent feedback arrangement. The driver's emitter resistor limits the amount of current that
can pass through the emitter- collector circuit
and into the base of the output transistor. The
base current is limited to a value that does not
allow collector current in the output transistor
to exceed its rating. Hence, short-proof protection is hails in and works automatically-.
Since the output transistors specified in Fig.
1 have a 30-ampere rating, a fuse in the output
line and another in the primary circuit of the
point supply transformer will circumvent any
possible damage that might otherwise result
from overloading. Also, to provide the maximum amount of protection against damage
CB1 in Fig. 3 is used on one of the output
transistor heat sinks.

October, 1970

www.americanradiohistory.com

R21

D2

C5
Distortion control R21 fastens to heat sink on which Q8 is mounted with small L
bracket and machine hardware. Terminal strip for D2 mounts directly below R21.

I21 to the anode lug of D2. Then solder

an 8" -long, #18 or larger wire to the solder
lug on Q7 and a 3" -long wire to the solder
lug on Q8.
Use #6 hardware to bolt the U brackets to
the chassis. Mount the heat sink assembly on
which Q7 is mounted to the left sides of the
brackets. Solder the wire from hole C on the
circuit board to the cathode lug of D3 on
the terminal strip. Connect and solder a 0 "long, #18 or larger wire between 7117 and
the emitter lead of Q7. Then solder the lead
from hole F on the circuit board to the base
lead of Q7. Route the lead connected to the
solder lug on Q7 under the board, and connect it to the lug at the junction of L1/1119
and 1120.
Now, mount the other heat sink assembly
in place. Connect and solder the lead from
the solder lug on Q8 to the L1/1119 and 1120
junction lug. (There should now be five wires
connected to this lug.) Locate the lead from
hole D on the circuit board and remove 3!1" of
insulation from the free end. Connect and
solder this wire to lugs 1 and 2 of 1121.
Route an 8" -long, #18 wire from the emitter
of Q8, under the board, and to R18. Solder
both connections. Then route the 10" wire
from the anode connection lug of D3 under
the board and connect the free end to the
44

cathode connection lug for D'. Solder the

wire from hole E on the boar to the base
lead of Q8.
Finish the wiring as follows Solder a 6"
wire between the side lug on th speaker fuse
holder and the lug nearest the use holder on
the output terminal block, an an 8" wire
from the ground lug on the r. etifier bridge
terminal strip to the other lug o n the terminal
block. Cut two wires to 12" lengths, strip the
ends, twist them together, ant connect one
end of the pair to the lugs on CB1 and the
other end to the lugs on the , erminal strip
located between the two fuse Holders in the
power supply. Finally, solder the free ends
of the wires on the circuit board to the appropriate points in the power supply filter section.
Insert a 5- ampere standard fuse in both
the speaker fuse holder and the power supply
secondary fuse block. For the rating of the
primary fuse, refer to the table in the power
supply sidebar for the particular output
power selected.
Q

Adjustment and Use. If the Universal

Tiger is to be used with any bu the very best
speaker system, the circuit car be assembled
without distortion control 1121. (In this event,
simply connect the wire from iole D on the
POPUL

ELECTRONICS

circuit board directly to the lug to which the

anode of D2 is connected.) However, with a
first-rate speaker system where there is a
possibility of noticing the difference between
0.1% and 0.01% distortion, R21 should be
added as shown.
Control P21 allows adjustment of the bias
to eliminate crossover distortion completely.
Thermal stability will not be quite as good,
but with a sound system there is little danger
of overheating since few people would operate the amplifier continuously at its full rated
power.
To set R21, adjust the potentiometer for
minimum resistance and the amplifier for
approximately a 1 -watt output into a load.
Observe the waveform at the base of Q5 on
an oscilloscope. Increase the resistance of
R21 until the waveform is distortion free.
Check the idle current of the amplifier; it
should be approximately 50 mA. Then seal
the adjustment.
The Universal Tiger should give years of
trouble -free operation if it is properly assembled. It is doubtful that any improvements in amplifier design during the next few

CBf

D3
For proper operation, sensing element of thermal
circuit breaker CB1 must contact Q7's heat sink.

years will produce an improvement in sound

quality when compared with this amplifier.
With distortion levels as low as they are in
the Universal Tiger, speaker, cartridge, and
tuner distortion will have to be reduced by a
factor of at least ten to make the amplifier
distortion a significant contributor to overall
distortion.
If you decide to build any of the high power versions of the Universal Tiger, remember that most speaker systems are rated
for peak power handling ability. This means
that in most cases you have to divide the
peak power by two to determine roughly the
amount of nos power the speaker can tolerate without damage. Other than this, there
are no precautions that have to be taken. -31--

1P 15K

Filter capacitors Cl and C2 in power supply mount

between amplifier assembly and power transformer.

Syln ur

,
45

October, 1970

www.americanradiohistory.com

BUILD AN

Electrolytic Restorer
PREVENT HIGH-VOLTAGE

CAPACITOR BREAKDOWN

This project is used to restore reform) the

dielectric in electrolytic capacitors that have
not been in use for an extended period of time Half -wave rectified ac is switch -selected and
applied to the capacitor. As the dielectric reforms, the voltage increases indicating a reduction in current flow through the capacitor.
Various reforming rates are available to the
builder, as well as various applied voltages
from 100 to 600 volts.

some of these capacitors in their junk boxes

(they were quite common in power supplies
for vacuum -tube circuits), but hesitate to use
them. Since they are fairly expe isive, it behooves the electronics experiment r or service
man to salvage such capacitors y restoring
the dielectric so that there is no lance of its
breaking down when put to use.
Aowever, before finding out h v to restore
an electrolytic, let's be sure we kn. w the exact

nature of the trouble.

WFIEN a high- voltage electrolytic capacitor
has been unused for too long a time, it is

What Is an Electrolytic Capacitor?

customarily looked upon as a possible troublemaker. Too often, when power is applied
to such units, the dielectric punctures, destroying the capacitor and probably the associated
circuit. Unfortunately, many people have

An electrolytic capacitor usually consists of

two flexible sheets of aluminum foil separated
by gauze impregnated with an electrolyte.
Leads are connected to each foil section. The
foil connected to the positive lead has an
BY GEORGE J.

46

PLAMONDON

POPULAR ELECTRONICS

oxide coating which serves as the capacitor's

dielectric. It is the thickness of this coating
that determines the working voltage of the

capacitor.
While the capacitor is being used, the oxide
coating is preserved by chemical processes resulting from the voltage impressed across the
terminals. Unfortunately, when it is in storage, time and ambient heat take their toll and
the oxide deteriorates. When the full working
voltage is applied to a capacitor whose oxide

is weak, the latter breaks down and a short

circuit is placed across the circuit.

Reforming the Dielectric. The dielectric of a suspect capacitor can be reformed

by connecting a low de voltage across the
capacitor and slowly increasing the voltage
until the rated value is reached. This must be
done over a long period of time to allow the
oxide to reform properly.
The "Electrolytic Restorer" described here

m
OY

YON

QN

-vQQQ-Q

October, 1970

47

www.americanradiohistory.com

J4

J3

J2

JI

Perf board construction may be

used with the operating controls
and jacks mounted on the front
panel of the selected cabinet. A
TV -type "cheater" connector is
used to make the power connection. Mount the perf board on
suitable spacers and be sure that
components on the board do not
make electrical contact with any
of the front -panel elements.

R9

RIO

does this job automatically, and requires only

an occasional look at a dc voltmeter to check
progress. The cost of the project is about $14
if all parts are bought new.

Construction. The prototype shown in the

photos was housed in a conventional plastic
case although any type of arrangement will
suffice. The schematic of the circuit is shown
48

RII

R12

in Fig. 1. Exact placement o parts is not

given since dimensions are not ritical and the
control locations can be chan ed depending
on personal preferences.
Most of the circuit can be assembled on
perforated board. The front anel controls
and jacks are mounted direct' y on the case
cover, making sure that all cads are long
enough to reach the electron es board. For
i

POPULAR ELECTRONICS

sn l'ety,

1 :1

ac line isolation

lunld he used, tltonit this

he prottpc.

THEORY OF CIRCUIT DESIGN

Diodes 1)1 through D -1 and capacitors CI

throili C4 form a half-nave voltage quadrupler rectifier with a do output of approximately
600 volts. Resistors R7 through R16 form a

voltage divider network and S3 selects the desired voltage and applies it to the parallel
connected positive output jacks J1 and .12.
The negative side of the power supply is connected through a switch-selected resistor network consisting of R4 through R6 to the
parallel -connected negative jacks J3 and J4.
The use of S2 determines the forming rate.
The DIRECT position permits the unit to be
used as a high- voltage, low -current power sup ply. This position can be eliminated if desired.
The DISCHARGE position of S3 places R17
across the output to discharge the formed capacitor, while resistors R2 and R3 keep a
small load on the power supply and discharge
the power supply capacitors.
During the forming process, the capacitor's
resistance is low so most of the voltage is
dropped across the limiting resistor. As the
oxide coating in the capacitor is re- formed.
less current flows through the capacitor, causing the voltage across it to increase. When
this voltage equals the preset voltage on S3.
the reformation is complete.
-

trauslormer

is not shown in

Operation. The electrolytic capacitor to be

reformed is connected to the output jacks,
making sure that the polarities are observed.
The positive side of the capacitor is connected to either J1 or .1 and the negative
side to either ,T3 or J1. The de voltmeter for
checking the reforming action is connected
to the remaining two jacks. Make sure that
the polarity and voltage range are correct.
The voltmeter can be disconnected and reconnected at any time without affecting the
operation.
Place S3 in the ntscnARGE position, ping
the unit in, and turn on the power. Neon indicator lamp 11 should glow. Set the desired
forming rate on S2 and then rotate S3 to the
working voltage of the capacitor. If the capacitor is unformed, the voltmeter will indicate a. much lower voltage than that set on S3.
Note that the voltmeter indication starts to
increase quickly at first, then slows down as
the dielectric forms. The rate of increase is
determined by the eoudition of the capacitor
and the setting of S2. When the now setting
is used, the operation takes longer but the
oxide formed will be of better quality. The
opposite is true for the EAST setting. Use the
NORMAL position for most cases.

careful when drilling the holes in the plastic front panel as it will chip easily.
The neon indicator lamp is cemented in the hole, other components use hardware.
Be

49

October, 1970

www.americanradiohistory.com

Insulated wiring is used to make interconnections. If a metal case

is used, make sure spacers keep connections from touching the case.

When the voltage across the capacitor is

approximately equal to the set on S3, put the
switch on DISCHARGE and remove the capacitor. No harm will be done if the capacitor is
left connected longer than required, so it is
not necessary to check progress constantly.
To use the unit as a high -voltage, low -current power supply, set the forming rate switch
(S2) to DIRECT. A current of 4 mA may be

drawn continuously, and sour what higher

currents for a short period of t me. (A load
current of 10 mA causes a dis ipation of 3
watts in the divider resistors.)
The Electrolytic Restorer can also be used
for a quick go -no -go check o voltmeters.
Comparison of voltage switch settings and
voltmeter readings will reveal ny gross inaccuracies.

The finished front panel should be labelled as

shown here. A coating of transparent plastic
spray keeps lettering from becoming smeared.

50

POPULAR ELECTRONICS

COVER STORY

BY GEORGE MEYERLE

asseme
a

FReouency
eeuauzeR
THE NEW THING

Segment tone adjustment

This unity gain amplifier is inserted in a stereo

system between the preamp and the power
amplifier. Five manually operated controls
vary segments of the audio spectrum around
60. 250, 1000, 3500, and 10,000 Hz through a
range of plus r minus 12 dB. The Equalizer
introduces no distortion, hiss, or ac hum. Suggestions are made enabling the connection of
this device to an integrated stereo system.

S O YOU

SPENT a lot of time and money

putting together your separate-component stereo system. Now you are starting to

wonder where you went wrong because some

program material sounds terrific and some
not so hot- especially when you know it
should all be good.
Actually, there may be nothing wrong;
your problems probably stem from a variety
of sources which are difficult if not impossible
to control individually. For example, you
may have an imported disc recording which
was made using a nonstandard recording

October, 1970

51

www.americanradiohistory.com

-VE

`-

ern

IE

iii

mS
ce

1 1 1

-
Kn

mY

X
Y

111
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SO

ti'?
o

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I.O

11

n
S

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<

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a
co

EHI1

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/2

N
w=

z
ao

52

POPULAR ELECTRONICS

THEORY OF CIRCUIT DESIGN

PARTS LIST

-2

-MF, 50 -volt, electrolytic capacitor

(
10-pF, 50 -volt, electrolytic capacitor"
C.3, C'4
-pF disc capacitor`
10 -trF. 50 -volt. electrolytic capacitor'`
( :6,
250 -pF, 75 -volt, electrol }'tic. capacitor

( :1

:2-

-10

C5C7-

(:8--- 4.7 -)iF, 35 -volt capacitor*

( :9 -1 -pF, 100 -volt capacitor"
C10-- 0.22 -pF capacitor"
(: 11--- 0.068 -F capacitor*
(: 12- 0.0_2 -aF capacitor*
DI-D1-2-.1, 600 -V silicon rectifier diode
11- 117 -colt neon indicator assembly
J1 -J4 -Phono jack*
L1- 1.4 -11 inductor* (175 ohms dr resin
tance*)
I,2- I).3 -H inductor` (60 ohms do resistance" *)
L3 -0.1 -H inductor* (20 ohms dc resis-

tance''')

1.4

-30 -mH

inductor* (140 ohms dc resis-

tance'")
L5-10 -mil inductor" (30 ohms dc resistance'`*)
QI- Q3- 2.N5232 transistor*
Q4- 2N5354 transistor*
R 1,1110- 10,000 -ohm, '3 -watt resistor`
112- 150.000 -ohm. -watt resistor*
113-82,000-ohm, L:-watt resistor*
114.R5,R6.R8,R9- 3300 -ohnt. ', -tratt resistors
117-22.000 -ohm, ! = -watt resistor*
1111 -740 -ohm, 1-watt resistor
lt12.1114,1116.R18.1t20 -50. 000 -ohm linear -taper- dual slide potentiometer (CTS V490 or

similar)

-17 0 -ohm, f4-watt resistor"

115,R19-560 -ohm, Vi-watt resistor*
1117,1121 -680 -ohm, '4 -watt resistor*
SI -Dpdt slide or toggle switch.
52-Spst slide or toggle switch
T1 -Power transformer. 40-colt secondary
(Triad F-90X or similar)
'`For one channel only: duplicate for stereo.
"De resistance is important to avoid lowering
Ii 13

Q of

circuit.

Misc.- Chassis, knobs (5), line cord, terminal

strips. mounting hardware, metal bracket

for slide potentiometers.
Vote -7'he following are available from Ale trotee Industries, 1405 Old Northern Bird.,
Roslyn, .ArY 11576: etched and drilled PC
hoard #501 for :8 2.10; slide potentiometer
#502 for 82.20 each: set of 10 coils #503
for 89.50; complete kit of all parts including front panel- knobs, walnut side panels,
and instructions. T FEK fur $59.95; completely wired and tested unit with 2 -year
guarantee, # FEi! for :499.95. For last two
items. add 81?5 shipping charge.
New York State residents rind 5; sales tax.
Fig. 1. To avoid confusion, schematic shows
only one channel of equalizer; other channel
is identical to that shown. Power supply (at
lower left) is used for both of the channels.

The circuit uses a direct- coupled. four -stage

amplifier having slightly less than unity gain.
The first stage (Q1) is an emitter follower for
high- impedance input and low distortion. The
next two stages (Q2 and Q3) form a differential amplifier having two inputs to allow the
application of both signal and feedback. The
last stage I Q4) is used as a voltage amplifier
ith high open-loop gain to provide a stable
dc operating point.
The five manually operated tone controls
:,re linear slide potentiometers connected bencen the two differential amplifier inputs.
The slider of each potentiometer is returned
lo ground t:rrough a resonant circuit that delermines the frequency and range of adjust
ment. When the slider is at the full cut posilion. the resonant circuit shunts the input to
Ilie differential amplifier to ground. When the
-lifer is in the full boost position. the same
resonant circuit shunts the feedback to
_round. Thus. a single resonant circuit performs two functions.
Rr dcdgning the circuit so that both ends
of the slide potentiometers are returned to the
-:une potential, the coupling capacitors which
-onld othetsri.se be required are eliminated.
The capacitors in the resonant circuits perform the dc blocking function.
Due to the high feedback and ripple rejection. an inexpensive power supply can be used
tu full advantage.
The coils are suspectible to magnetic field
pickup from the power transformer if not
properly oriented. If you follow the physical
.urr :usgment shown in the photos. pickup
-hould be at a mininmun.
-

curse. In titis ease, y-ou may not he able to

compensate for the odd sound level.
Your problems may also he due to room
acoustics and the response of your speakers.
The wall behind a speaker acts as an extension of the speaker mounting hoard for low
frequencies, therefore wall size and how
close the spe._ker is to it can stake a dramatic
difference in the low-frequency response of
the system. The materials of which tige floor,
galls and cciling are stade can affect the
l'rctfhcueies from the lower mid -range and
np. W lien !tight-frequency sounds bounce
around the hard walls of tt room, tllc net
effect is an apparent peaking of the highs.
On the other Laud, it' the floor is carpeted
and there are heavy drapes on the walls, the
hilts usas appear dull. Similarly, late sofas
and overstuffed chairs absorb certain freclucueics and reduce their coutribttfioti to the
overall. sound.
Speakers are particularly suspect. Certain
types (even good ones) may have excessive

October, 1970

53

www.americanradiohistory.com

Fig. 2. This actual size etching guide can be used to duplicate circuit board
used in original prototype. Dots in corners locate board mounting holes.

CUT

IN

BOOST

OUT

02
R3

RI

C2

i
R6 R7

lQI

04

CIL.

*--R2-40-R5-'

GND`*
-- Z- ..-R5 -r
R

Clt}
1

C2

RI

T
R6 R7

Q3

Q2
R

R C3

4-0
CUT

IN

BOOST

OUT

Fig. 3. When mounting components on

ientations
54

of

electrolytic

capacitors,

GND

circuit board, make sure that lead orand transistors are correct.

diodes,

POPULAR

ECTRONICS

limit-frequency response which makes strings

sound tinny and strident. Others may be weak
in the mid- range, producing a sort of nasal
result. There are many reasons why speakers
sound different and there's not much you can
do about most of them except adjust the
frequency response curve.
Up to now the high- fidelity industry lias
tried to solve these problems by supplying
tone controls that boost or cut the high and
low ends. This lias not been satisfactory because such controls cannot compensate for the
small changes required in the low and upper
mid -ranges without dramatically affecting the
it is
extreme lows and highs. For example,
desired to boost "presence" at 3000 ITr a few
decibels, the standard toile control would also
boost 10 kHz about 8 or 10 dB, increasing
hiss and record scratch.
What the stereo enthusiast requires is a
tone control system that allows adjustment of
discrete segments of the audio frequency
spectrum so that these individual segments
call be tailored to suit a particular requirement, without affecting any other part of the
spectrum. The Stereo Frequency Equalizer is
just such a system, with five independent
i

L'

frequency range adjustments. Wbiie there is

no limit to the number of .idjustments that
could be used, the more adjustments, the
sharper the separation filters have to be, and
it has been found that sharp, narrow filters

TECHNICAL SPECIFICATIONS
Frequency response (flat setting): 1 dB, 5 Hz
to 250 kHz
Tone control range: 12 dB at 60 Hz, 250 Hz,
1 kHz, 3.5 kHz, and 10 kHz
Intermodulation distortion: 0.05% at 2 volts

output
Harmonic distortion: 0.05% at 2 volts output
(20 Hz to 20 kHz)
Hum and noise (shorted input): 80 dB below
1

volt

Maximum output: 9 volts

Gain: Unity, plus 0, minus 2 dB
Recommended output load: 10,000 ohms or
greater
Output impedance: 10 ohms
Input impedance: 75,000 ohms
Power consumption: 3 watts

have excessive phase shift and may actually

canse a whole new series of response problems.

Construction. The Equalizer, whose partial schematic is shown in Fig. 1, should be

constructed on a printed circuit board, using
the foil pattern shown in Fig. 2. Once the
PC board is available insert the components
as shown in Fig. 3. Note that the schematic
shows only one channel of the stereo system,

Capacitors, indc.ctors, and resistors for filters mount on front panel of chassis.
Terminal or tag strip is used to provide interconnection points for components.
October, 1970

55

www.americanradiohistory.com

HIRSCH -HOUCK LABORATORIES

Project Evaluation
was capable of delivering 3.7 volts, although distortion increased a bit here.
The harmonic distortion at 1000 Hz is
virtually nonexistent, unmeasurable below 1 volt and much less than the 0.03%
noise level. At one volt output, the first
was
made -a
mere
measurement
0.0077% of second harmonic! At the
rated 2-volt output, the distortion was
only 0.015 %, climbing to a maximum of
0.077% at 7 volts.
Intermodulation distortion at 2 volts
was measured at 0.016 %, and fell to a
minimum of 0.005% between 10 and 20
dB below the rated output, climbing to
0.015% at 30 dB below 2 volts. This is
just about as distortionless as could be
desired with modern equipment and techniques.
The noise level in the output could not

The Frequency Equalizer is one of

those add -on devices that go well with
almost any stereo setup where tailoring
the sound reproduction to the listening
environment is desired. The project did
a good job of tailoring. It was tested first
on the bench, then through objective listening.
The gain of the Frequency Equalizer
was measured at 0.79 ( -2 dB) at 1000
Hz. It measured within 0.3 dB from 5
to 500,000 Hz, well under the author's
specification. The output impedance is
exactly 10 ohms, also as claimed. Into a
high- impedance load of about 100,000
ohms, the output clipping level occurred
at 9.5 volts. Then into a 10,000 -ohm
load, clipping occurred at 9.0 volts, which
is still ultra -safe for any hi -fi application.
Even into a 1000 -ohm load, the Equalizer

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FREQUENCY, Hz

Response of equalizer at maximum and minimum settings; at zero position, response is flat.

Note short wires for input connections

and twisted pairs for the two outputs.
56

POPULAR ELECTRONICS

g' L Eli

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FREQUENCY. Hz

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New curve was obtained with all controls set at zero, except 1000 Hz control set at

be measured because of a slight subsonic

"bounce" at about 70 dB below

volt,

which masked the actual hiss and /or

hum. Judging from the display pattern on
an oscilloscope, the noise level in the
audio region must exceed the -80 -dB
rating claimed.
The composite frequency response
curve was made with the 60 -, 1000 -, and
10,000 -Hz controls at maximum (and
minimum), while the remaining controls
were set to zero. Then the controls were
set to zero and the 240- and 3500 -Hz
controls were set to a maximum (and
minimum). This gives a rough idea of the
variety of curves possible with the Equalizer. Needless to say, there are an extraordinary number of combinations
available. Also, note how flat the re-

while both channels are on the one PC board.

The power supply is connnon to both channels. Component numbers are identical in the
tWF-o ehannels.
A typical mounting and enclosure scheme
is shown in the photos -and- other arrange meut would be equally satisfactory. The PC
board is mounted on four spacers at the bottom of the chassis. The power transformer,
power outlet SO/, tape monitor switch Si
and two sets of four phono jacks are on the

+12 dB.

sponse is with all controls set to zero.

To display the shape of one filter, the
1000-Hz filter was set to maximum with
all the other controls set to zero. As an
extreme case of correction, all but the
1000 -Hz control were set to minimum
and the 1000 -Hz control to maximum.
As compared to something like the
Altec 'Acousta -Voicette," of course, the
Frequency Equalizer has rather broad
filters. However, they do an effective job
and go well beyond the capability of most
ordinary tone controls. They are essentially equivalent to the JVC "SEA" amplifier, which is considered to be one of
the best from the equalization standpoint. In any event, the Frequency Equalizer performed fine in listening tests. It
was able to tailor the sound very well.

rear apron. Use

line cord.
The filter and
are mounted on
are arranged so

a grommeted hole

for the ac

potentiometer combinations
a separate metal plate and
that only the potentiometer
shafts protrude through slots on the front
panel. The metal plate is drilled to accommodate the five dual -slide potentiometers
which are twist- locked in place if you use the
devices specified in the Parts List. Be sure
that the end holes for the slide potentiometers

October, 1970

57

www.americanradiohistory.com

Input and output jacks J1 -J4, ac receptacle SO1, and power transformer T1 are
mounted on rear apron of chassis as in
interior (above) and exterior (right)
views. Strain relief protects line cord
from sharp edges of entry hole in apron.

Dual slide -type potentiometers fasten to front surface of filter subchassis bracket After fastening
them in place, make certain that control tabs properly mate with slots in decorative front panel.

To provide clearance for and access to sol

der lugs on potentiometers, cutouts must be

made through the filter subchassis bracket

have sufficient clearance l'or the potentiometer

terminals. One end of each inductor is connected to its respective teTntinal on the
potentiometer; the other end is connected to

terminal strip insulated from Brou n j

Titi; lug also holds une end nl' the associated
resistor. The other end of the resistor and One
end of the associated capacitor are couaected
to another terminal lug. The other cull of the
capacitor is conuec'ed to a column]] gTottnd
buss that runs the length of the metal plate.
Slot.; jest wide enough for the poteniometer .shafts are made in the actual front
panel. PoVer iwitr:I s ? and indicator lamp
/1 are mounted on the limit panel. Once all
mechanical work is complete, 'ire the circuit
as shown in
I, remeiobering that yon are
dealing with a stereo systcm.
For a neat appearance, the front panel
should be marked with care. Trim the five
slots l'or the potentiometer shafts. Mark each
slot with a frequency identifier as shown in
the photos. At the exact center of each
potentiometer range, marl: a zero. Then space
the 3 -, (i -, 9 -, and 12 -dB marks evenly above
and below the zeros. The 12 -di; points should
be at the extreme ends of the potentiometer
travel.
a

FRED. EQUALIZER

RECEIVER
TAPE

INPUT

OUT

L O--

TAPE MON,
L

TAPE MON,

0--i

INI

SF-

713

gm

1-

LgIOUT

If you have an integrated receiver or any

combination having it tape monitor switch,
use the hookup shown in Fig. 4A. In this
ease, note that the tape monitor switch on

r-0

-0

QR

(A)

TAPE RECORDER
(THREE HEA01
IN

OUT

LOIN

Fi

Use. If your audio s }-stem lins a. preamplifier separate from the poorer amplier, connect Flic Frequency Equalizer between the
two, observing the correct channel notations.

SWITCH TO OUT

ain

OUT

SWITCH TO IN

le)
Fig. 5. Wiring diagram (A) shows how to connect

equalizer to integrated stereo system. Diagrarr

(B) shows how to make hookup for a tape recorder

the equalizer is in the "out" position; the

receiver switch in the "monitor" position.
Use other controls normally. The Equalize]
provides a tare monitor feature with an additional pair of jacks at its output, to allow
monitoring of the tape as before. For connections to a tape recorder, see Fig. 4B. The
other connections are as shown in Fig. 4A.
Wif.lt the system operating, each slick
potentiometer can be adjusted for the desired
results, which, of course, are up to you. -Er-

October, 1970

55

www.americanradiohistory.com

BUILDING A

Printing Exposure
met er
Light

Measure Enlarger
Light Intensity
with Accuracy and Repeatability

Through the use of an LDR as one leg of a dual -range bridge circuit, this lightmeter "trips"
on or off a panel indicator lamp. Light level
variations are readily detectable and the longterm repeatability of the circuit is excellent.
The tripping action is selected by the operator
and may be calibrated in foot candles.

FOR THE PHOTOGRAPHY enthusiast

who does his own enlarging, a enlarger
lightmeter is a must if he expec s to work
efficiently and economically. By tandardizing his enlarger exposures, he can just about
eliminate paper waste.
Since enlarging paper requires uch closer
enlarger
control than photographic film,
lightmeter should include a well subdivided
BY A. A. MANGIER1

60

POPULAR ELECTRONICS

ii\:
\\\$}

Q\\(\

Ji.Ea

{(

\ \ \ } \ \ \ \\

{(
o

ui

0-0-WPAN-

\\/\\/

\}}\}\

October, 1970

a,

www.americanradiohistory.com

Get more
education
or
get out of
electronics
...that's my advice."

IN-DEPTH
COVERAGE OF

SOLID STATE
ELECTRONICS

...including
integrated circuits!

62

POPULAR ELECTRONICS

Ask any man who really knows the electronics industry.

Opportunities are few for men without advanced technical education. If you stay on that level, you'll never
make much money. And you'll be among the first to
go in

layoff.

But, if you supplement your experience with more

education in electronics, you can become a specialist.
You'll enjoy good income and excellent security. You
won't have to worry about automation or advances in
technology putting you out of a job.
How can you get the additional education you must
have to protect your future-and the future of those
who depend on you? Going back to school isn't easy
for a man with a job and family obligations.
CREI Home Study Programs offer you a practical way

to get more education without going back to school.

You study at home., at your own pace, on your own
schedule. And you study with the assurance that what
you learn can be applied on the job immediately to
make you worth more money to your employer.
You're eligible for a CREI Program if you work in electronics and have a high school education. Our FREE
book gives complete information. Mail postpaid
card for your copy. If card is detached, use coupon
below or write: CREI, Dept. 1210A, 3224 Sixteenth
Street, N.W., Washington, D.C. 20010.

aMm! Monde

el

rn Menawl Mg, iM Padr CmrJ

CREI, Home Study Division

McGraw -Hill Book Company
Dept. 1210A, 3224 Sixteenth Street, N.W.
Washington, D.C. 20010
Please mail me FREE book describing CREI Programs.
am employed in electronics and have a high school education.
NAME

AGr

ADDRESS
CITY

STATF

ZIP

CODE_

EMPLOYED BY
TYPE OF PRESENT WORK
I

G.I. BILL

am interested in

Electronic Engineering Technology

Computers
Space Electronics
Nuclear Engineering Technology
o Industrial Automation o NEW! Electronics Systems Engineering

APPROVED FOR TRAINING UNDER NEW G.I. BILL.

October, 1970

65

t
www.americanradiohistory.com

Fig. 2. Actual size printed circuit etching

guide is shown at right; while below is the
component location and orientation diagram.

RIO

02

LDRI
RIO

;1

}}

11

1
R3
K

R6

R7

'11

..}I 1
DI
1

TI
(123v)

RI

Ig

R277
11C3R9C4R13

- 11111

--022
41-+

also shows the component ins allation and

the external connections. Tran istor sockets
should be used to prevent the al damage to

II
T

(COI M)

TI

(6.3V)

scale for high resolution readout. It should

also have precise resettability and repeatability. The meter described here has a low
range from 0.01 to 1 footcandle over an eight inch scale, plus a 10X multiplier to increase
the range to 10 footeandles. Light -level variations just a few percent above or below the
set point of the calibrated dial cause snap action turn -on or turn -off of a panel lamp. A
stabilized bridge circuit affords long -terni repeatability and 100:1 light coverage per
range, while a nonlinear scale provides readability to several percent at any setting.

Construction. The schematic of the enlarger lightmeter is shown in Fig. 1. The

photoresistor (light dependent resistor)
LDR1, is mounted in a thin plate -like package which is connected to the rest of the
circuit by a long two- conductor cable as shown
in the photos. Most of the electronic circuit is
built on a printed circuit board, the foil pattern for which is shown in Fig. 2. This figure
66

II

the semiconductors during sold. ring.

For the prototype a 41/2" X 61 " X 2" metal
case was used to provide ample room for the
components with enough space for a large,
easy -to -read scale. Almost any type of enclosure can be used, as long as s fficient panel
space is provided.
Mounted on the top panel ar the calibration potentiometer R10, powe switch S1,
range switch S2, indicator lamp 71, and input
jack J.I. The latter should be iii sulated from
the metal ease. When all of tires components
have been assembled, mount the power transformer T1 on one wall of the e, se; and after
soldering the required leads to die PC board,
mount the board on four space Connect the
circuit as shown in Fig. 1.
Using a piece of %r," thick trai sparent plastic, make up a cursor (or poin er) as shown
in the photos to fit on the siaft of R10.
Scratch a hairline at the center of the cursor
and fill it with black ink. The knob selected
for use on R10 should preferably have a large
diameter for easy handling. Ccn ent the cursor
to the knob. Prepare the upper surface of the
panel for the calibration mark: and with the
knob temporarily installed on /1/0, make sure
that the cursor can swing fro limit to limit
of the potentiometer. Install fo 1r rubber feet
on the base of the chassis.
POPULAIR ELECTRONICS

Interconnecting wires from chassis mounted components can be soldered

to appropriate points on the circuit
board through use of "flea" clips.

The photoresistor is placed either within a

thin plastic case or sandwiched between two
pieces of thin insulation board. A slot is made
in one board to provide room for the connect ing cable (which can be made from old earphone cabling). A hole in the other board permits light to reach LDR1. Some form of finger
,grip should be fabricated and attached to the
upper board. Use small hardware to finish off
the insulation board sandwich.

Calibration. With the circuit wired as

shown in Fig. 1., turn on the power. Remove
QI from its socket and note that indicator
lamp J1 comes on. If Il remains off, progressively decrease the value of R5 to keep SCR1
simple plastic "sandwich" provides a convenient
means of mounting light dependent resistor LDR1.
A

FINGER
GRIP
LORI

from turning on by itself. Re-insert Q1 in its

socket and with S2 set to the X.1 position,
connect a 390,000 -ohm resistor in place of
LDR1. Lamp Il should go on and off as I10
is varied about its mid -position. If it does not,
reverse the leads of either secondary or Ti. If
the problem still exists, progressively decrease
the value of RI to increase the drive to SCR1.
Remove the 390,000 -ohm resistor and note that
71 remains off at all settings of 110. If it
does not, slightly increase the value of R7.
Set 111 to about 30 ohms. Then adjust to desired lamp brightness but do not exceed 2
volts across lamp.
A 0 -100 dial plate can be used as a logging
scale. However, it's well worth the effort to
prepare a calil.rated scale for maximum versatility of the meter. The calibrating procedure makes use of the inverse square law
relating to light radiating from point sources.
illumination in foot -candles (FC) is equal to
lamp candle power (CP) divided by the
square of the distance in feet (D) from lamp
to LDP. location. Thus, FC = CP /D'.
For the light source, use a new #5i1 panel
l:unp operated at 7.5 volts ae from a filament
transformer. Use a powerst at on the primary
side or a rheostat in series with the lamp on
he secondary side to adjust the lamp voltage.
Mount the lamp rigidly, base down, and positioned so that is filament is broadside to the
I,DR, facing it squarely.
Tape the mounted LDP. to a wooden L
bracket and mount a black card having a
hole several inches in front of the cell to block
oft most of the stray room light. Run tests at
night in a large dark- walled room. At lamp-tot

PLASTIC " sANDWIC14"

67

www.americanradiohistory.com

THEORY OF CIRCUIT DESIGN

l'hntore-istor light dependent re- istor)
f

LORI and selected range resistors R8 and R9

form two sides of a bridge energized by filtered
dc. Resistors R6, R7, and RIO make up the
remaining arms of the bridge, energized by a
dc square wave developed at zener diode DI.
The square wave resets Ql to off at each cycle.
When the voltage at the anode of Ql exceeds
the voltage at the anode -gate AG I. QI turns
on thus energizing the gate of NCR 1. This
turns the SCR on and simultaneously turns
pilot lamp II off. Averaging filter R2 -C2 bypasses moderately large ac components of
light present in cold light sources and the
comparatively small components from incandeseentsources.
As the resistance of LDRI takes on different
values when exposed to different light levels,
the turn -on for trip point) of Ql occurs at
different settings of potentiometer RIO. Circuit action provides a snap action, rather than
a gradual turn on, of II at the trip point. Resistors R3 and R4 determine the bridge loading and are proportional in values so that turn on and turn -off of QI occur with minimum
hysteresis or deadband on RIO.
I

1.I)lt distances of 3 ", 6", 9 ", 1', 2', cte. to 10',

measure LDII resistance at each point with an
accurate ohmmeter.
Next, using the inverse square law, calculate
the illumination in footcaudles -using 1.2 for

the lamp's candle power. (Titis value is 20%

higher than the rated value to allow for higher
radiation broadside to the lamp filament.)
Plot cell resistance vs footcandles on 1 X 1
cycle logarithmic graph paper.
From the graph, read cell resistances at
0.01, 0.02, 0.03, ete. footcaudles. Using a potentiometer set to these resistance values substituted for LDR1, locate division marks on
the panel from 0.01 to 1 FC. If the 0.01 to 1.0

Circuit board mounts on U

bracket with aid of four
spacers. Potentiometer RI i
then fastens entire assembly to front panel of case
via its mounting bushing.

68

POPULAR ELECTRONICS

range sloes not fit over the availa le range of

R10, use a different value of resi tor for RS
to account for LDR variations. W th resistors
equivalent to 1 and 10 FC, use a different
value of resistor for R9 so t tat th i high range
tracks the low range with as lit le tracking
error as possible. You may prepa e a second,
separate scale for the high range if desired.
Scale numbers may be direct rem ing or they
can be as shown on the prototyp with X.01
and X.1 multipliers selected by S'.

Application. When measuring light levels

of a projected image, adjust I.10 CCW so
that 11 goes from off to on. Also, when adjusting light level through lens opening, decrease the aperture so that the la np goes on
at the trip point. This eliminate. any stray
light contribution from the panel amp itself.
All darkroom lights must be off during use
of the meter.
Standardize the meter by makii g test runs
with the various enlarging pape : that you
use. Make a perfect print by the usual cut and -try procedure. Using the meter, measure
and record the setting of R10 when the lamp
turns on at the lightest and darkest portions
of the image, as well as at the important parts
of the image. For negatives and paper of the
saute or similar contrast and with he sane or
different enlarger magnification, 11 you have
to do is adjust the lens aperture t match the
standardized settings and expos the print
as before.
Since readings on the calibrate scale have
a known relationship to each oth r, you can
double the standardized readings nd cut the
exposure in half -and vice ve . Also, the
highest and lowest readings provic an indication of the contrast on a negative, which is an
aid in selecting paper contrast. For enlarging,
you may prefer to read the calii$rated scale
as 1 to 100 on the low range and 10 to 1000
on the high to avoid use of decimals. -ice

VHF UHF
DRAIN -DIP
OSCILLATOR
SPOT CHECKING IN THE 140 -540 MHz SPECTRUM

carefully machined quarter -wavelength line

is substituted for a parallel -resonant LC tuned

circuit in this grounded -gate FET oscillator.

Mechanical calibration of the tuned line permts accurate frequency determinations between 140 and 540 MI*. 'he author describes
a unique coupling and tuning system of interest to the experimente-.

1IE 6111D -DIP" OSI'1LL-ATJP is a real

godsend when it comes to checking radio requency circuits. Its versatility in measuring
c resonant frequency cif a tuned circuit, as

a si_nal injector. and as an aid to determining

the values of unknown capacitors and inductor, plus its h cost, make it an it found
on many workbenclres. Unfortunately, the usefulness of most inexpensive dip oscillators decreases rapidly at frequencies exceeding about

150 1IITz.
The VIIF -UTIF "drain -dip" oscillator described in this article is designed to work at

frequencies wIere most dip oscillators work

poorly -if at all, It covers a continuous frequency renne of 140 to 540 MIIz. Tuning' over
this range is smooth and even, with only one
false dip in the entire coverage.
BY A. E. McGEE, JR., K5LLI

October, 1970

69

www.americanradiohistory.com

-1

cl

3pP

RI
IK

01
2N3819

EPI

LI

C2

I
I

JI

0-1

R3
1

10K

L.

R2

mAMI

SI

*SEE TEXT

Fig. 1. Those components shown inside dashedline box are located in one chassis, while in
another chassis are located those at right.

PARTS LIST
Bl, B2 -9 -volt battery
CI

-3-pF ceramic capacitor

JI -Phono jack
LI -See text

MI-0 -1 -mA dc meter movement

PI -Phono plug
Q1-2N3819 or HEP802 field -effect transistor

RI- 1000 -ohm,'''4 -watt resistor

The circuit is extremely simple, and the absence of plug -in coils and a sensitivity control
makes for easy operation. Most important, the
drain -dip oscillator costs less than $10 to build
if an inexpensive imported or surplus meter
movement is used.

Theory of Circuit Design. Field-effect

transistor Q in Fig. 1 operates as a grounded gate oscillator. The variable -length drain lead,
Li, acts as a quarter-wavelength tuned line
which is equivalent to a parallel- resonant LC
tuned circuit. Feedback of the proper phase
to sustain oscillations is provided by capacitor
Cl, which is in series with the internal source to -gate capacitance of Ql. These capacitances
form a voltage divider across resistor R1, applying a source -to -gate voltage that is in phase
with the drain voltage to bring about oscillation.
Drain current varies with the strength of
the oscillations and is greatest when the oscillations are the strongest When the dip oscillator and the external circuit are both tuned to
the same resonant frequency, the external
circuit absorbs power from the dip oscillator.
This reduces the feedback and causes a reduction, or "dip," in the drain current indication on meter MI.
Unique construction is responsible for the
simplicity of the drain -dip oscillator. Tran70

BI

9V

62

9V

R2 -1000 -ohm potentiometer

R3-10,000-ohm potentiometer
SI -Dpst slide or toggle switch
Misc.-%" x 3s" x %" aluminum tangle; ''A "outer- diameter brass tubing; -'/z" faucet
washer; M"-diameter shaft; control knob;
dial cord: 316" aluminum sto:k; 0.018"
galvanized steel or brass; 0.005" brass; 4 -40
machine screws; hookup wire; .older; etc.

sistor Q1, capacitor Cl, and res storilil mount

on a small circuit board asset ably to which
contact "fingers" are connecte 1. This circuit
board assembly is designed to r >ove in chassis
rails so that the fingers bear do vn on the rails
and ground the source and gate circuits of Ql.
Drain voltage is supplied by a aength of copper braid (LI) that forms the resonant drain
circuit.
When the circuit board is moved in either
direction against the chassis rai s, the effective
length of the braid is varied by pulling it
through an output coupling loop. The base of
the loop is grounded for r -f by the mounting
plate, which itself forms one plate of an r -f
bypass capacitor. Physical mo ement of the
board is accomplished by a tuning "dial"
mechanism that connects the co i per braid and
a dial cord in a continuous lo ,p around the
tuning shaft pulley. The circuit .oard is joined
to the top side of the loop, wl le the bottom
of the loop passes freely un er the circuit
board assembly.
By turning the tuning kn.b, the circuit
board moves along the chassis rails, varying
the length-and, hence, the indi etance-of the
line between the drain lead oI Q1 and the
coupling loop. Since, in the p ocess, the inductance of the line changes, th ' resonant frequency of the line and, therefor the frequency of oscillations also change.
POPULAR ELECTRONICS

Parts Fabrication. Machining the parts

that make up the drain -dip oscillator is fairly
simple. It involves cutting, filing, drilling, and
thread- tapping the metal members, plus fabricating a circuit board assembly and minimal
wiring. Some careful fitting together of the
mechanical assembly is necessary, but in most
cases tolerances are not critical; the only
criterion is that the parts fit together uniformly and do not interfere with each other. In any

event, any machining that might be necessary

to get the parts to fit together will be simplified by the use of soft aluminum angle which
can be easily cut and filed.
First, fabricate the four chassis rails from
1/8" -thick aluminum angle that is 3/4" on the
side. Dimensicns and hole locations are given
in Fig. 2. When cutting the angle, use a fine tooth hacksaw and take care to prevent bending the pieces. Use a 4 -40 tap for the holes to

16"

I/8"R

o
I"

16

2"

1i8"R/

1-2

Ai

b*

DIA

ALL RAILS I/8" THICK ALUMINUM

ANGLE WITH 3/4" a 3/4" LEGS

13

3"

6
16

DIA

(4 HOLES)

16

3"

DRILL AND TAP

FOR 4 -40 SCREW

FRONT AND REAR

BOTTOM PLATES
I/16" -THICK ALUMINUM

Fig. 2. Chassis rails (upper drawings) are made from /B" -thick by 3/4" on
the leg aluminum angle; front and rear bottom plates from 1/16" -thick
aluminum stock. Drill all holes as indicated, but screw-tap only those specified.

October, 1970

71

www.americanradiohistory.com

It must first be annealed by heating it until

3

red hot and allowing it to cool to room temperature naturally; do not immerse the hot tubing
in water or oil.
When the tubing is cool to the torch, pinch
one end closed with pliers and fill t e tubing
with fine sand (beach sand will d nicely).
Pack the sand tightly, and pinch losed the
open end of the tube. Then file or cut a 1/8 "wide by %2" -deep groove around a length of
3/4 "- diameter wood dowel to make a bending
form. Place the tubing in the groove and carefully bend it to shape. Work slowl to avoid
sharp bends.
Referring to Fig. 3, trim the tubi g to size,
removing both crimps. Empty out the sand
and remove any remaining grit wi h a pipe
cleaner. Machine the output loop mounting
plate from 0.018" -thick brass or galvanized
sheet steel as shown. Then solder the tubing
to the plate. Be careful to prevent the solder
from flowing into the open end of the tube
and, through capillary action, causi g an obstruction. Let the assembly cool; hen slip
over the curved portion of the tub a length
of plastic tubing.
The drawings given in Fig. 4 sho all of the
dimensions and assembly instructio s for the
circuit board assembly. The circuit oard and
k epoxyits base should be made from
glass board, copper-clad on one side only. After etching and drilling the cire 't board,
mount the components on it as sho, 'n in the

3"
B
16

5/16 "R

/6"
OD BRASS
/TUBING (SEE TEXT)
I

Fig. 3. The mounting plate for the output

coupling loop must be fashioned from 0.018" thick galvanized steel or brass shim stock.

be tapped as indicated. Then fabricate the

front and rear bottom plates from %e-thick

aluminum.
The most difficult part to fabricate is the
output coupling loop. This must be formed
from 1/8 "- inner-diameter brass tubing (available from most hobby shops or salvaged from
an old and empty ballpoint pen ink cartridge) .
The tubing is too hard to be bent immediately.

CIRCUIT
BOARD

T
12

F
f

24

LIL

t-L-4-1:1DIMPLE
LIGHTLY
CONTACT

FINGERS
(4 SETS

COPPER
BRAID

RE0.0)
DIAL.

N.

SPRING

Fig. 4. Complete details for fabricating circuit board assembly are shown
in this series of drawings. The contact fingers are made from 0.005" -thick
springy metal. Circuit board etching guide (directly above) is actual size.

72

POPULAR ELECTRONICS

H- i"--*1
TAP 4 -40

I"

-r

9"

,16

.1L

T2
T

Li

Fig. 5. Two short lengths of aluminum

angle serve as supports for dial

TOP
16

2"

shaft. Faucet washer is cemented to

shaft and grooved to make pulley.

DIA

_L
9"
32

T
6

8
SI DE

layout drawing. Then carefully set the board

over the oblong area shown on the base (see
perspective drawing), and solder the two together. Bolt a dial cord spring to the board
with 4 -40 hardware.
The contact "fingers" must be made from
thin (about 0.005 ") brass, beryllium- copper,
or other springy metal. A piece of bronze
weatherstrip is a convenient source of material. Eight fingers in all are needed. Before
bending them to shape, lightly dimple each
about 1/8" from one end.
Once bent to shape, the fingers should be
soldered to the four square corners of the base
of the assembly, about 4i4' in from the side
edges to prevent the sharp edges of the fingers
from dragging along the aluminum rails.
The drive pulley for the tuning mechanism
can be made from 1/2 "- diameter hard rubber
or fiber faucet washer (see Fig. 5). The actual
dimensions of this washer will be about 3/4"
diameter by 1/8" thick. Carefully ream out the
center hole of the washer to provide a snug fit
when it is slipped over a 3/4" oaring shaft.
Posit ion the washer as shown, and bond it in
place with epoxy cement. Allow the cement
to cure for at least 24 hours. Meanwhile fabricate the shaft brackets from the same aluminum angle used for the chassis rails. Drill

mounting holes and tap them for 4-40 machine hardware.

When the cement has cured, chuck the short
end of the tuning shaft into a drill. With the
drill operating, gently apply pressure from
a small file against the outer rim of the washer
until you have a groove that is about 1/22" deep
by 1/8" wide.
The tuned drain lead is simply a length
of tinned copper braid measuring approximately %io " wide when stretched and flattened.
The exact dimension is not critical, just so the
braid passes freely through the output loop
tubing.

Assembling the Project. Locate the

front bottom plate, the output loop assembly,
and both bottom rails. Determine which will
be the mating surfaces between these pieces;
then cover the top side of the front bottom
plate and the underside of the rails with a
single layer each of Scotch "Magic" tape.
Lay the tape an evenly without overlapping
the strips or leaving any exposed metal. An
awl or other sharp instrument can be used to
perforate the tape at the screw hole locations.
Now, set the bottom plate atop the output
loop's base, properly oriented, and mark the
outline of the notch in the bottom plate on the

#4 SOLDER
LUG

PLASTIC

TUBING

With brass tubing soldered to mounting

plate, slip piece of plastic tubing over
looped section; solder piece of hookup
wire with solder lug to mounting plate.

October,

1970

73

www.americanradiohistory.com

TUNING SHAFT BRACKETS

(2)

FLAT METAL WASHERS(2)

TUNING SHAFT

DIAL CORD

COPPER BRAID

CONTROL KNOB

TAPE INSULATOR
(SEE TEXT)

-.
6

A
A

*THESE

*
(4

SCREWS BOLT DOWN TUNING

SHAFT BRACKETS

CONTACT FINGERS NOT SHOWN

Fig. 6. Assembly drawing shows how all parts that

make up oscillator subassembly go together. Use 440 machine screws throughout. Also, carefully note
how dial cord /variable drain braid must be routed.

When properly put together, circuit board

assembly should move freely in the chassis
rails. Use just enough spring tension to
prevent dial cord from slipping when you
tune back and forth along the dial train.

74

POPULAR ELECTRONICS

Shown is correct sequence of assembling parts that make up dial tuning assembly. Flat metal washers are
used to reduce friction and wear between pulley and support brackets and to prevent play between them.

loop plate. Solder one end of a 24" length of

stranded hookup wire within the outline
marked. Make sure that neither the Faire nor
the solder goes beyond the outline.
Referring to Fig. (i, assemble the lower half
of the project, making sore that the larger
holes in the output loop assembly are centered
over the smaller holes in the rails and bottom
plate. Use 4 -40 X r'ic" machine screws. (Under one of these screws, fasten one end of
another 24" length of hookup wire, using a
different color of insulation for easy identification. Twist both wires together and solder
the free ends to a phono plug.)
Now, use an ohmmeter, set to the highest
multiplier range, to check the insulation between the output loop assembly and all other
metal parts. You should obtain a reading' of
infinity. Any other reading indicates that the
insulation between the output loop assembly
and metal chassis is defective and must he
corrected immediately before proceeding.
Temporarily mount the top rails to the assembly with 4-40 X 1'4" tnacliiuc screws. Test
the circuit board assembly for fit inside the
rails and proper movement in both directions.
1f you are satisfied, disassemble the top rails.
Leave the circuit board in place, and string
the dial cord and variable-length drain lead
braid as shown. Apply .lust enough dial spring
tension to insure that the dial cord does not
slip when the tuning knob is turned. _1lso at
t Ids time, make sure that the copper braid enters the coupling loop squarely; if it does not,
carefully adjust the geometry of the loop tubing until it does. Ruh a. soft. lead pencil over
the copper braid to provide lubrication, and
apply small amounts of light grease to the
chassis rails where the contact fingers ride.
Then fasten only one of the top rails in place.
Meter .111, batteries P,1 and 1 ;2. and resistors 2 and 113 can be assembled in any size

chassis box that will conveniently accommodate them. Circuit layout is not critical.

Tuning And Use. Set 1'2 for minimum resistance and temporarily disconnect IC?. ('lose
,''1 and adjust I'? for about a three -quarter
scale pointer deflection on 111. NOW touch the
tuned line near ,)1 with the tip of your finger.
if the oscillator is operating, touching the litre
will cause a drop in the meter current indication. Tune the oscillator through its range; the
current should remain fairly stable ()NAT most
o1' the tuning. range, gradually falling off at
the high- frequency end.
If you experience trouble getting the oscillator to work properly throughout its ent ire range, try changing the value of C1 slight ly. (You might encounter a false dip ill the
meter indication at one point in the tuning
range. If so, make a note of its location on the
dial rail to avoid future confusion.)
Next, set 1?.9 for maximum resistance and
reconnect 1;?. With ,ti'J closed and the oscil-

CALIBRATION CHART
F

(in.)

(MHz)
140

150
160
170
180
190

165/32

200
220
240
260
280
300

121/4

17;ie
155732

149'3?

13'5/32
123/4

11',.2
103/3?
911/22
821/22

83/32

(MHz)
320
340
360
380
400
420
440
460
480
500
520
540

(in.)

_.

6;
63,

6 ;'i

525/22
51/2

5h2

5 ;'i b
421/22
421/32

415/32

For other frequencies use the formula:

2422
L(in.)= F(MHz)

75

October, 1970

www.americanradiohistory.com

lator set near the high end of its tuning range,

touch a moistened fingertip between the drain
connection of QI and the chassis. Oscillations
should immediately cease. Still touching the
drain lead, adjust R2 so that the meter indicates zero. Remove your finger and tune the
oscillator for a maximum meter indication.
Adjust R3 for full -scale pointer deflection.
Repeat this procedure and readjust R2 as necessary. Now the meter pointer will remain onscale at any frequency setting and the meter
pointer will swing between zero (no oscillations) to full-scale (strongest oscillations) .
The oscillator can be calibrated easily and
with reasonable accuracy by using predetermined lengths of 300 -ohm twin -lead TV antenna cable as quarter-wave resonant lines
with known resonant frequencies. Cut the
twin -lead first to 18" long. Strip away 1/4" of
insulation from both conductors at one end,
bend the stripped wires toward each other
until they touch, and solder the wires together.
Now, starting with the longest length of
twin -lead (lowest resonant frequency) indicated in the Calibration Chart, tune the drain dip oscillator as follows : Loosely couple the
drain -dip oscillator to the shorted end of the
line and rotate the tuning knob on the oscillator chassis for a dip in the meter pointer
deflection. The dip should be sharp and dis-

tinctive. Mark the dial rail with he frequency

indicated in the Chart for the ength of line
used near the circuit board inde_
Trim the twin-lead to the ne t longest dimension indicated in the Chart ( rim from the
open end of the line only), and peat the tuning procedure. Continue trimmi'ig and tuning
for each frequency desired.
If possible, lay the twin -le d across the
edges of an open cardboard bo so that most
of the line is in open air and well clear of
metal surfaces. For greatest
curacy, the
coupling between the twin-lea and output
coupling loop of the drain- ip oscillator
should be as loose as possible The 140- to
180-MHz lengths of line will al.o give resonances at three times the mark d frequency,
or at 4 -wave resonances. T se harmonic
resonances, however, can be asily distinguished from the primary reson nces by their
positions anvay from the low -fr uency end of
the oscillator's dial.
If possible, the output loop .Iiould be coupled to the low- impedance or gr unded end of
the circuit to be measured. If th circuit is inaccessible, link coupling can be, used between
the circuit and the dip oscilla or. But take
care to avoid mistaking the li k resonances
with the resonances of the rcuits under
test.

In the photo above, the oscillator subassembly is shown in the stages of final assembly,
hile the underside view below shows part of the power cables that goes to the bridge circuit's chass s (lower right).

76

POPULAR ELECTRONICS

c/k

Practical
expanded eocale

Mllimmeter
MEASURING THE ALMOST JNMEASURABLE

This test instrument was developed

to measure what most electronic experimenters are inclined to think of as
inconsequential resistances. However,
the less than 1 -ohm losses are important factors in detecting hi -fi ground
loops, poor contacts in high amperage
circuits, corrosion, etc. The circuit is
a simple, easily balanced bridge. Provision is made in the instrument for
long storage and battery protection.

rONVE.T1C.., I,

home and ticld -tylce

"OM's are not designed to resolve ac-

curately resistance readings between zero and

one ohm. Even the very best mnitimeters employ a logarithmic scale.
10 ohms as an
average center-scale reading when the raine
switch is in the times -one position. And you
need a very sharp eye, indeed, to differentiate
between reading; of, say, 027 and 0.115 ohms
on a multitap transformer.
Commercially available milliohmmetcrs are
BY DAVID R. CORBIN

October, 1970

77

www.americanradiohistory.com

RI

PARTS LIST

S2

2511

STORE

-TEST LEADS

3 -0.1 OHM
4 -1.0 OHM
5 -0.47 OHM

BI -Three 1.5 -volt AA cells connected in

parallel
M1- 0- 1 -ntA, 50 -ohm meter movemet t (Monarch No. PMC6.S or similar)
R1 -25 -ohm. 5 -matt wire -wound potentiometer
(Mallory No. V W25 or similar)
122,B6-1 -ohm, 2 -watt, 5% tolerance wire uround resistor
R3 -10 -ohm, 2-watt, 5% tolerance w rewound
resistor
R4-2 -ohm, 5 -watt wirewound pote tiometer
(Mallory No. V IV2 or similar)
-ohm, 1.5 -watt, 5% tolerance w rewound
R5
resistor
R7 -0.1 -ohm, 2 -watt, 5% tolerance w rewound
resistor
R8-0.47 -ohnt, 2 -watt, 5% tolera e wirewound resistor (optional, see text.
SI -Spst pin- plunger momentary-acti n switch
(Robertshaw No. 1MD1 -1A)
S2- Five-position, non -shorting rotary switch
(Mallory No. 3215f or similar)
Misc.-Five-way binding post pair; banana
plug pair; Keystone No. 171 three -AA -cell
holder; control knobs: chassis box: hookup
wire: epoxy cement; solder; etc.

-4

R4
211

Fig. 1. Resistor R8 provides optional but very

useful internal testing facility for checking

calibration; Si is momentary- action switch.

expensive instruments, costing $175 and

more. However, with modern solid -state
equipment in which biasing resistors in the
0 -1 -ohm range are common, a milliohmmetcr
is almost a must for measuring such values.
By eliminating unnecessary ranges and maintaining accuracy to within practical limits, it
is possible to build a milliohmmetcr for less

than $18.
The milliohmmetcr described in this article
has two very useful ranges-0 -1 ohm and
0-0.1 ohm. The scale is very nearly linear (it
would take very expensive and elaborate
equipment to show that it is not), but is actually a tiny portion of a logarithmic curve,
expanded to cover the full swing of the meter
pointer.
Theory of Circuit Design. As shown in
Fig. 1, the circuit of the milliohnuneter consists of a resistive bridge, one side of which is
made up of the test leads (and resistance
being measured). Closing S1 causes current
to flow from 131 via R1 to the bridge.
With S2 in position 2 and the test leads
shorted together, R4 is adjusted to ten times
the lead resistance, balancing, the 1:10 ratio
of the R2-R3 side of the bridge. The meter
will now indicate zero, regardless of the setting of R2. If the test leads are disconnected,
with Si closed, the bridge will be heavily unbalanced in a direction such that current will
78

flow from R2 through the me .r to R4,

swinging the meter pointer off -seal
For calibration purposes, S must be

switched to R6 for the 1-ohm rang or R7 for

the 0.1 -ohm range. If S2 is in po ition 3, 117
is placed in series with the test 1 44 ds, unbalancing the bridge circuit and i owing the
meter pointer by an amount det rmined by
calibration potentiometer Ili. Po entiometer
RI is then adjusted to produce full-scale
pointer deflection.
Setting S2 to position 2 anc, placing a
0.1 -ohm resistor across the leas s will also
cause a full -scale deflection of the meter
pointer (assuming that the settin of R1 remains undisturbed). Hence, it is possible to
compare the standard internal re istances of
R6 and R7 with the values o resistance
being measured and obtain direct :readings in
ohms.

Resistor RS is used to smooth the operation

of R4 and help balance the brit ge. An optional feature of the circuit is 1T 5 which provides a useful internal resistance for checking
calibration.

Construction. Assembling the milliohmmeter should present no problems, since there

is nothing critical about the circuit. As shown
in Fig. 2, all components, excels_ the battery
bank and its holder, mount directly to the
front panel. To simplify mounting, a hardPOPULAR ELECTRONICS

RI

2. The simplicity of the circuit

allows all components to connect directly to the control and meter lugs.
Fig.

battery supply for the circuit is

mounted in place with the aid of three
AA -cell holders and machine hardware.
The

set epoxy cement bonding is used between the

top of the housin of switch s'1 and front

panel and between the battery holder bank

and ease. The meter utovetuent, binding posts,
function swilel (.s.2), and potentiometers
fasten in place \Nith the horawtne supplied.
Sinec there are only a few eoutponents,
wiring by the point -to-point method is easy.
Note, however, that the bank of three batteries that stake up /11 must he connected in
parallel with each other. _\!so, when mounting the binding posts, make absolutely certain
that both are insulated from the front pastel.

Once the circuit is wired up as illustrated

in Fig. 2, assemble the ease. Now, make your
test leads. Probe -type leads are useless for
the ntillioluutneter. What are needed for the
test ends of the cables are strong spring loaded clip; that will lock solidly onto the
leads of the components under test. This is
necessary because in dealing with resistance
measurements in the fraction of an ohnt
range, contact resistance becomes an imporant factor in accurate cal :.oration and test

read in s.
It is not necessary to use any special type

October, 1970

79

www.americanradiohistory.com

Polar Electronics
El..,

CENTS

NOVEMSER

1970

Light -emitting
Diodes for

Readout

and
Communications

On Sale

October 20
FEATURING
What may become the most significant invention within the past few years
is the light- emitting diode. Possible
applications range from miniaturized
readouts to color TV with paper -thin
screens. Find out all about LED's
including details on a basic voice
communications system using commonly available components.
Kickoff of a new series of digital
test instruments that provide the
experimenter with premium gear at
modest prices. This first article
describes a main frame and frequency
counter. Subsequent issues will show
construction of a time period readout,
digital voltmeter, etc. All are plug -in
modules.
If two hi -fi speakers are better
than one, does it follow that four are
better than two or 16 an improvement
over 8? Not so, says Dave Weems in
his analysis, "The Numbers Game."

80

of test lead cable, nor are the le gths of the

cables critical. The instrument is designed so
that, in zero -adjust nulling and ill -scale deflection calibration, the test leads ecome part
of the bridge circuit and are ` nulled out"
regardless of their specific resi tances. (It
may seem strange that you have to consider
test lead resistance, but the mete will easily
demonstrate that if a null is ob ained using
only one lead, the meter will indicate halfscale deflection with both lead -and after
calibration will give the resista ce in milli ohms of the lead not used in the nulling procedure )
How To Use. First, short together the
alligator clips on the test leads. It is best to
clip the leads together in the saine manner as
they would be clipped to the leads of the
component under test. This will assure good
contact resistance. If you merely hold together the clips with one hand, You will find
adjustments difficult to make because of the
varying pressure you exert on the clips.
Especially noticeable on the 0.1 -ohm range
will be the "jumpy" movement of the meter
pointer.
Next, set R1 to maximum resistance and
S2 to the TEST LEADS position. Depress Si
and adjust null control R4 for a zero meter
reading. Then release S1 and s t S2 to the
desired range position. Again, depress S1.
Now, adjust the setting of calibr tion control
R1 for a full -scale pointer deflec on.

Release S1. Set S2 to the TES LEADS position. Your meter is now ready to measure
resistance values in the range for which it was
calibrated.
When storing the milliolunme er away, set
S2 to the STORE position. This inimizes the
chances of damage or off -scale readings
should the PRESS -TO -TEST switch e accidentally depressed. As with any type of electronic
equipment, batteries should be removed altogether for prolonged storage.
Aside from checking the va ues of less than- one -ohm resistors, the mill ohmmeter is
a handy item to have available for other
tests. It can be used to check corrosion in
automotive wiring connection,, a serious
source of IR losses even if onl\ a few milliohms of resistance is involved. Other uses include troubleshooting motors, generators,
and starters, measuring the cold resistance of
incandescent light bulbs, winding bias and
motor control resistors from hookup wire,
and checking for resistance in power distribution systems and ground circuits.
1

POPULAR ELECTRONICS

Second in a New Series by "The Reviewer"

UNLIKE SOME stereo equipment, the testing of communications receivers is a
well- defined art. First you make sure that
alignment is on the nose and that all controls
(panel and otherwise) are operating according to the parameters set forth in the instruction manual. Next, you submit the
receiver to a battery of laboratory tests:
selectivity, sensitivity, agc characteristic and
i -f image rejection. Last, but not least, you
try out the receiver on the air using a
variety of antennas. Then, hopefully, you
write a sensible and useful report.
In today's language, a "communications
receiver" is defined as a receiver that tunes
the shortwave spectrum ( preferably 2 to 30
MHz), has a fair degree of sensitivity and
selectivity, bandspread tuning, S- metering,
bfo, product detection, noise limiting or
blanking, etc. Obviously, there are many
receivers ( ranging up to $4500) that fit
within the above definition, but sad to say,
there are probably just as many ( regardless
of price) that fail to qualify usually in
more ways than one.
Heretofore, an SWL or ham knowledgeable about receivers could distinguish a true
communications receiver on the basis of
selling price, but within the past year the
price parameter has collapsed. In June 1970
The Product Gallery reviewed the Heathkit
Model GR -78 and although Heath calls it a
General Coverage receiver, it is really a
flexible, low -cost communications -style receiver. About the same time that review was
being written, Knight-Kit ( Allied Radio

Shack) was announcing a new SWL /ham

receiver that it did advertise as a communications receiver -the under $100 Model
R -195.

The Knight -Kit R -19S This is a 5 -band

single conversion superhet tuning from
about 200 to 420 kHz and 550 kHz to 30
MHz. The R-195 is another of the new breed
of receivers using i -f stages employing 455 kHz ceramic filters. These filters replace l -f
transformers and are fixed tuned, thus the
i -f strip never needs adjustment or alignment. Three FET's are used in the R -195
front end; one in a grounded-gate r -f stage,
a second FET in the mixer, and a third FET
as a Hartley oscillator. Separate AM and
CW /SSE detectors are used and there is a
series -gate AM noise limiter, S -meter amplifier. agc rectifier, and a complementary
configuration audio output stage. Although
designed for 117 -volt ac operation, the R -195
may be operated in an emergency from a
12 -volt dc battery about 14-ampere drain)
through a special rear skirt connection.
Assembly of the R -195 is very simple.
since the receiver is delivered to the buyer with three pre -wired printed circuit
r -f board, an i -f board and an
boards
audio amplifier board. The builder wires
in the power supply, bandswitching, front
and rear panel controls and terminals and
strings the dial cord. Only the latter is of
any sort of major undertaking and is notable for trying your patience and improving
(

an

The Knight -Kit R -195 is a good looking

receiver, although the photo shown here,
supplied by the manufacturer, differs (in
bandspread scale) from the model as
received and assembled by your reviewer.

October, 1970

81

www.americanradiohistory.com

your swear-word vocabulary. From opening

the shipping container to turn-on, you can
expect to invest between 12 and 13 hours.

Laboratory Tests. Following the r -f

alignment instructions detailed in the Construction Manual and then double -checking
with test equipment, I found that the builder
can obtain very good performance from the
R -195 without resorting to an r -f alignment
generator. However, for purposes of comparison between the manufacturer's claims
and my tests, the R -195 was aligned with
laboratory test gear. The sensitivity results
(10 dB S +N /N) are shown at the right.
The AM sensitivity vs CW /SSB sensitivity
suffers from inefficiency in the AM diode
detector. At many points on the dial the AM
detector is operating at a very low level and
apparently departs from the linear portion
of its detection (rectification) curve. Thus,
efficiency is low and there is a deterioration

20

zo
1-

4-30

v
>

40

50

6012

10

kHz

10

12

Clean symmetrical selectivity curve of the R-195 results from the use of ceramic filters in the i -f stages.
Unfortunately, good selectivity cannot be used
to maximum advantage due to poor bandspread.
82

Band

SENSITIVITY TALE
AM
AM
CW /SSB
(Measured)

(Claim d) (Measured)

(Microvolts for 10
A: 200 -420 kHz
B: 550 -1800 kHz
C: 1.8-4.8 MHz

3.0

2.0

1.4
1.25
3.1

1.5
1.5

B S +N

/N)

0.55*
0.3*
0.28*

2.0
4.8-12.0 MHz
1.8
1.0*
4.4
11.0 -30.0 MHz
*Equal to or better than manufacturer's claim.

D:
E:

in the AM sensitivity of weak signals.

Selectivity was measured at 3.0 kHz at

dB down, 10.0 kHz at 30 dB down and 24

kHz at 60 dB down. This compares with the
claimed 2.5 kHz at 6 dB and 7.0 kHz at 30
dB. The S -meter readings varied from a
low of 28 V for S9 at 1800 kHz to a high
of 240 V at 28.0 MHz. A 40 dB r -f input
change (10 -1000 V) resulted in a 14 -dB
a-f output change indicating that the age
characteristic was not too satisfactory.
6

Overloading occurs at about 1000 V and

will produce "birdies" and intdrmodulation
on the AM broadcast band.
Image rejection averages 25 dB on Band
A, 40 dB on Band B, 28 dB on Band C, 22
dB on Band D, and 10 dB on Band E. On the
latter band the average is distorted by the
very poor rejection above 22 MHz where it
drops to less than 6 dB.

10

cc

R -195

On The Air -As the test figures indicate,

the R -195 is a sensitive receiver with reasonable selectivity, both qualities far better than
the operator can use to advantage. Also on
the good side of the ledger, the audio quality
is excellent and more volume output is available than necessary. Frequency stability is
surprisingly good for a $100 receiver and
the front panel controls are nicely situated
and convenient. On the negative side, I found
Band A (200 -420 kHz) useless in metropolitan New York due to the strong images
from the AM broadcast band stations. Overall bandspreading is too tight for ease in
separating stations and on Band E the antenna trimmer pulls the oscillator making
the R -195 somewhat unstable on the 10meter band. Dial calibration and the S -meter
are difficult or impossible to read under
some lighting conditions in your SWL /ham
shack.
As a summary of my findings, I am convinced that the R-195 is easy nd foolproof
to assemble and in a dollar cons fous marketWhat the
place it is an obvious barga
receiver lacks in refinements are compensated for by excellence in st bility, sensitivity, and selectivity.
POPULA

ELECTRONICS

The printed circuit boards (above) are su3plied

pre -soldered and partially pre -aligned - Builder
makes the necessary interconnections, mounts the
front and rear Janet cortrols and terminac and
then threads that _!"% dial cord through the hole.

Considering the selectivity and excellent sensitivity of the R-195, the totally inadequate main tuning
and bandspread arrangements are almost criminal. Only below 4 MHz does the operator have a
chance of setting up cold on a desired frequency.
Not only is the recessed S-meter difficult to photograph, it's more difficult to see when operating
the receiver. The main dial tuning scale suffers
from parallax problems and, on higher frequencies, it is virtually impossible to set or reset
the R -195 receiver to a desired known frequency.

MY PERSONAL nomination

for the least

used, yet highly useful, piece of test

equipment is the signal tracer. I don't think
it's a matter of discrimination or thoughtlessness, it's just that most hobbyists and
experimenters fail to see the value of assembling something for which they have
no immediate requirement. Also, the signal
tracer is not exotic :.s an oscilloscope or as
"basic" as a VOM /VTVM. but for what the
tracer lacks in glamour, it makes up in prac-

tical usefulness.
I have had some sort of signal tracer on
my lab bench for the past 20 years. Its
built -in audio amplifier has been used a
hundred or more times and the r -f probe
has repeatedly located "lost" signals in receivers ranging from the All- American 5
to the most complex and costly multi -tube
communications type. Within the past six
years, the tracer I've used has been the

Eico Model 147A -an oldie with four vacuum

tubes including a 1629 "Magic Eye" and
6 X 4 rectifier.

The Eico Model 150 Signal Tracer

Some months ago Eico obligingly sent nie
a new 150 Signal Tracer Kit. It is similar to
the old 147A except that everything is solid
state and the magic eye has been replaced
by "cat's eye" meter! Assembling the kit
is not a major undertaking and working at
my snail's pace I had the job completed in
just under 4 hours.
There's nothing too tricky about assembly although a few wiring instructions were
confusing. For example the "Red Dot" on
the speaker (p.. 8, step 6) was missing as
were the 10 solder lugs (p. 9, step 1 ) , but
neither of these classifies as a calamity. Of
course, the GED 29A6 transistor is now a
2N5355 which might confuse some builder,

October, 1970

83

www.americanradiohistory.com

and there's no eyelet to bend over the shield

(p. 17, step 61 -both a little startling. But
Eico is getting back on the ball and the 150
worked perfectly at first turn -on.
For those interested, the 150 is basically
a four -stage audio amplifier with a 400 mW output, medium gain audio amplification (60 -mV drive to full output) , high gain
r -f amplification (1 -mV drive) very low
internal a.c. hum level, meter and aural
output, plus provisions to use the built -in
speaker separately without the amplifier.
The amplifier output can also be fed to a
scope or VOM.
,

There isn't too much more I can say

about the 150. I like it better in some ways
than the elderly 147A, althoug strangely
enough the first thing I missed vt as the taliBut this
brated wattmeter of the 147
would have been a difficult add tion to the
150 circuit. I have used the 150
ice in the
last few weeks, once to find ho much r -f
was leaking out of a suppose y shielded
enclosure and then as a substitute amplifier
to trace out some residual hum in an HQ215 receiver -I still haven't found the hum,
but that's not the 150's fault-it did the job
it was expected to do.

Signal tracer is supplied with two probes- direct

for audio tests and an isolated diode rectifier for
rf tests. We dislike fragile tips and tip jacks
and plan to substitute sturdy double banana jack
and plug at Audio Input on our Signal Tracer.

Two hundred microampere meter on new

150 is "different." Wired to collector
of the audio output stage, the speaker
had to be blasted to get'
halfway up scale. It looked Ike cat's eye.

Behind the panel of the 150,

wiring is very simple. Audio

amplifier is assembled on a
printed circuit board. Power
transformer is <t lower left.

84

POPULAR ELECTRONICS

ITHINK that I have an unhealthy dislike

about reviewing stereo hi -fi equipment. I

seem to be more consciously aware that so
much about stereo is wholly subjective. You
can make laboratory measurements to your
heart's content and report your findings in
very explicit language, but reading in a magazine about a stereo system will never actually tell you what it really sounds like.
Such word pictures can be misleading-possibly not intentionally-but subject to literal
misinterpretation, nevertheless. In The Product Gallery I have made a decision (with the
concurrence of the publisher and the editor)
that I will only review stereo equipment that
is "different" and not "run -of- the -mill."
Although such a decision might seem to
limit severely stereo product reviews, I have
found that there are numerous unusual products that can be reviewed in POPULAR ELECTRONICS and which the readers will find of
particular interest. Some of these new products involve atypical concepts, some brilliant
engineering innovations, and others represent either extraordinary performance capabilities or noteworthy dollar values. I don't
intend to compete with the numerous competent analyses in my sister publication STEREO
REVIEW with its strong emphasis toward
the user and music lover. But, then, I don't
expect STEREO REVIEW to start talking about
test equipment or communications receivers
either.
Stereo enthusiasts need not be told that
within the past few years there have been
two concurrent equipment developments for
use in the home-the "compact" system and
the "surround sound" reproducers. The evolutions of both developments make interesting stories-some of which appears in this
issue on page 94. I think it is safe to say
that the compact stereo system is here to
stay and that it has brought matched -component stereo equipment into the hands of
music listeners who might not otherwise feel
that they had the resources or knowledge to
assemble an individual component setup.
There is a tendency among stereo equipment manufacturers to combine the two
above developments into the same package.
The reasoning is valid, but the method as to
how the combining should be accomplished
and to what order of magnitude the listener
should depend on surround (or reflected)
sound is just coming out of its experimental
stage. And, for more years than I care to
recall, audio engineers have attempted somehow or other to make the hi -fi amplifier responsive to changes in the listening environment. Engineers have explained that a
system should sound better if it could be
made to compensate automatically for
changes in room absorption, changes in the
furniture arrangement, selective room reso-

nances, etc. To my knowledge and up until

now, none of these schemes ever worked in
a fool -proof fashion. The "feedback" loop of
information caused these systems to "hunt"
or "cycle" in wild -eyed attempts to compensate for compensations.
The Electro -Voice Landmark 100. Recently I field- tested and Hirsch -Houck laboratory- tested a "different" compact stereo
system that has apparently solved some
part of the runaway feedback problem -the
Electro -Voice Landmark 100. This compact
system has introduced what it calls "Servo Linear Motional Feedback" which it applies
to its "Acoust-Array Cube Speakers."
All of this impressive lingo means that
E -V has developed a new solid -state circuit
to monitor the speaker cones and to instantaneously compare its movement with
the signal being passed out the amplifier. If
these two do not match, the feedback circuit
makes a minor correction that has the effect
of reducing audible distortion (particularly
below 300 Hz ) and slightly adjusting the
amplitude responsiveness of the speakers to
the listening environment.
When you open the three E -V shipping
cartons containing a Landmark 100 you
find a Garrard turntable /player mounted
above an AM /FM /FM stereo receiver /amplifier combination in one carton. In the second carton are two relatively small speaker
cubes (somewhat truncated on two edges)
and in the third carton is a smoke -tinted
plastic dust cover that snugly fits over the

turntable /player.
Hooking up the Landmark 100 is a matter
of plugging in the cables from the speaker
cubes, attaching the FM dipole (if necessary), releasing the turntable hold -down
bolts, and plugging in the ac power cable. In
a matter of 10 minutes you are listening to

stereo.
The most obvious physical "difference" in
the Landmark 100 to distinguish it from
other compact stereo systems are the two
partially truncated "Acoust- Array" cube
speakers. Each cube contains three miniature
full -range speakers and one emphasizing
tweeter see photo) Each cube weighs over
10 lb and has full -range radiation from the
front and from the two truncated planes.
The user can position the cubes to literally
aim, compress, or expand the stereo listening stage. I have no information on the division of power between the various speakers
in each cube and there may not be any,
but I can say that the idea of "aiming" appears to work in practice. The connecting
cables between the amplifier and the cubes
are 16' long and this permits placing the
cubes in seven or eight different configurations-one of which is undoubtedly suitable
(

October, 1970

85

www.americanradiohistory.com

to your particular listening requirements.

The amplifier in the Landmark 100 is rated
at 80 watts IHF music power, or 20 watts
per channel continuous output with both
channels being driven. There is no way to
confirm or deny this fact in a laboratory test
since the speakers are permanently wired
into the amplifier circuit. Although in power
output the Landmark 100 may not look impressive, let me say that it can be played loud
enough (without apparent breakup or distortion) to drive just about any listener out
of a very big room.
Laboratory tests on the FM tuner were
a different matter and, happily, all of the
tests met the manufacturer's specifications.
The IHF usable sensitivity was 1.9 V, as
rated, and the FM distortion was 0.53%

which the manufacturer had rat d at 0.5 %.

The FM frequency response w s very flat
and is well within 0.5 dB fror 230 Hz to
15,000 Hz. Stereo separation in ti- e FM tuner
was better than the average to e expected
in this price category and exceded 35 dB
from 500 Hz to 2500 Hz and was more than
20 dB from 30 Hz to 12,500 Hz.
New Phono Cartridge. For what appears to be exclusive use in the Landmark
100. Electro -Voice has developed a new

moving magnet cartridge, trademarked the

"Stereo -V." In laboratory tests it was noted
that the cartridge itself does not have particularly high compliance, but does have excellent tracking ability at middle and high
(Continued on page 116)

Landmark 100 is a compact stereo

system with 40 watts (IHF) per channel output into pair of unusual cube
speakers. Motion of speaker cones is
monitored to insure reduction of low
end distortion through special feedback loop. Rear skirt (below) reveals
simplicity of stereo setup connections.
E -V

Cube enclosure has 3 full -range speakers -one facing forward, two on the
truncated surfaces. Tweeter is under
fingertips. Panel controls are plain
with FM carrier centering meter and

automatic "Stereo" multiplex light.

Earphone output jack is under thumb.

86

POPULAR ELECTRONICS

SHORTWAVE LISTENING

Broadcasters Change Frequencies -The majority of the international

broadcasting stations shift to winter/summer frequencies and schedules
on November 1. Broadcasters make four primary schedule changes each
year (March, May, September, and November) In view of the now rapidly
declining sunspot cycle, shortwave listeners may expect to hear more
crowding on the lower frequencies -particularly 31, 25, and 19 meters.
Many of the broadcasters have abandoned 11 meters and a drastic
curtailment of broadcasting on 13 meters is expected in 1971.
.

AMATEUR RADIO

Planet Mars QSO- Visitors to the headquarters of

the American Radio Relay League, Inc., Newington, Conn.,
continue to be intrigued by one of the most unusual
trophies offered to ham radio operators. It is the
Elser- Mathes Cup that will commemorate the "First
Amateur Radio Two-Way Communications Earth and Mars."
Donated by Colonel Fred Elser, W6FB /W7OX and Lt. Cmdr.
Stanley Mathes, K1 CY (deceased), the cup also honors
Hiram Percy Maxim (founder of the ARRL), who had
an intense interest in communicating with Mars and
Venus. When donated to the ARRL in 1929, the idea of
ham radio reaching even the moon was considered
impractical, but ham -style E -M -E (earth- moon -earth)
reflected communications are now almost commonplace.
Maybe the first man on Mars will be a ham. If so,
his trophy is all ready and waiting for him.

BROADCAST BAND

-If

TV Antenna for DX'ing

you have a selective receiver and would
like to try your hand at BCB DX'ing don't put up a long -wire antenna
you probably have a better antenna right at your fingertips. Don't laugh,
but it's your outdoor TV antenna! Look at it this way: if you twist
the two wires from the 300 -ohm twinlead together and connect them
to your receiver ANT input, you have a top -loaded vertical-just like
a BCB transmitter. Make sure that the receiver GND goes to a very good
earthy ground because at the medium wavelengths that part of the antenna
system is particularly important. (Submitted by Frank H. Tooker)
RESEARCH
A Reading from on High -The FCC has been requested by Readex Electronics, Inc.
to establish a wholly new radio service called "Industrial Telemetry." Readex
wants assignments in the 216- 220 -MHz band for miniature low -power transmitters,

October 1970

87

www.americanradiohistory.com

i'EDER\IMUl4ML'\TCi.1TIO\S'COtl.fIISSIO\

S.MttILlLF31iinaert
FIRST

CLASS

irindy,"si!

:;;i`
I7
. uAR!!'ILe11n1or1E7As![A,ZlnRlll711TRRTi
!

..m. e e........o....c.......a. .ca `w;4.+.

ttcaMa

ester than

9 out of
10
CIE men Hein

91. 1%7

their "ticket"
the very
first
time they try
rg 7NY

Cleveland Institute of Electronics

of success in obtaining a
Government FCC License
The Cleveland Institute of Electronics hereby warrants that
upon completion of the Electronics Technology, Broadcast
Engineering, or First -Class FCC License course, you will be
able to pass the FCC examination for a First Class Commercial Radio Telephone License (with Radar Endorsement) ;
OR upon completion of the Electronic Communications
course you will be able to pass the FCC examination for a
Second Class Commercial Radio Telephone License;
AND in the event that you are unable to pass the FCC test
for the course you select, on the very first try, you will receive a FULL REFUND of all tuition payments.
This warranty is valid for the entire period of the completion time allowed for the course selected.

Dr. G. O. Allen
President

88

Popular Electronics -Oct. 1970

iL

Ur

or

3)

You can earn more money

if you get an FCC License
4

...and here's our famous CIE warranty that

you will get your license if you study with us at home
There is one way, however, of being pretty
certain that you will pass the FCC exam. And
that is to take one of the FCC home study
courses offered by the Cleveland Institute
of Electronics.
CIE courses are so effective that better
than 9 out of every 10 CIE -trained graduates
who take the exam pass it. That's why we can
afford to back our courses with the iron -clad
Warranty shown on the facing page: you get
your FCC License or your money back.
There's a reason for this remarkable record. From the beginning. CIE has specialized
in electronics courses designed for home
study. We have developed techniques that
make learning at home easy, even if you've
had trouble studying before.

with your present income?

The most practical thing you can do
about it is "bone up" on your electronics,
pass the FCC exam, and get your Government license.
The demand for licensed men is enormous. Ten years ago there were about
'100.000 licensed communications stations.
including those for police and fire departments, airlines, the merchant marine, pipelines, telephone companies, taxicabs, railroads, trucking firms, delivery services, and
NOT SATISFIED

so on.

Today there are over a million such stations on the air, and the number is growing
constantly. And according to Federal law,
no one is permitted to operate or service
such equipment without a Commercial FCC
License or without being under the direct
supervision of a licensed operator.
This has resulted in a gold mine of new
business for licensed service technicians. A
typical mobile radio service contract pays
an average of about $100 a month. It's possible for one trained technician to maintain
eight to ten such mobile systems. Some men
cover as many as fifteen systems, each with
perhaps a dozen units.

In

a Class by

It Really Works
Our files are crammed with success stories
of men whose CIE. training has gained them
their FCC "tickets" and admission to a higher
income bracket.
Mark Newland of Santa Maria. Calif.,
boosted his earnings by $120 a month after
getting his FCC License. He says: "Of l
different correspondence courses I've taken.
CIE's was the best prepared, most interesting, and easiest to understand."
Once he could show his FCC License, CIF
graduate Calvin Smith of Salinas, California.
landed the mobile phone job he'd been after
for over a year.

Opportunities in Plants
And there are other exciting opportunities
in aerospace industries, electronics manufacturers, telephone companies, and plants operated by electronic automation. Inside industrial plants like these, it's the licensed
technician who is always considered first for
promotion and in -plant training programs.
The reason is simple. Passing the Federal
government's FCC exam and getting your
license is widely accepted proof that you
know the fundamentals of electronics.
So why doesn't everybody who "tinkers"
with electronic components get an FCC License and start cleaning up?
The answer: it's not that simple. The government's licensing exam is tough. In fact,
an average of two out of every three men
who take the FCC exam fail.

...

Station WBOE

"I give Cleveland In-

stitute credit for my

First Class Commercial

FCC License. Even
though I had only six
weeks of high school
algebra, CIEs AUTO PROGRAMMED lessons make electronics theory and fundamentals easy. I
now have a good job in studio operation,
transmitting, proof of performance, equipment servicing. Believe me, CIE lives up
to its promises."

Yourself

Your CIE instructor gives his undivided personal attention to the lessons and question;
you send in. It's like being the only student
in his "class." He not only grades your work.
he analyzes it. Even your correct answer;
can reveal misunderstandings he will help
you clear up. And he mails back his corrections and comments the same day he receives your assignment, so you can read his
notations while everything is still fresh in
your mind.

Coming Impact of UHF

This demand for licensed operators and service technicians will be boosted again in the
next 5 years by the mushrooming of UHF
television. To the 500 or so VHF television
stations now in operation, several times that
many UHF stations may be added by the
licensing of UHF channels and the sale of
10 million all-channel sets per year.

THESE CIE MEN PASSED THE FCC

NOW THEY
LICENSE EXAM
HAVE GOOD JOBS
Matt Stuczynski,
Senior Transmitter
Operator, Radio

Chuck Hawkins,
Chief Radio
Technician, Division
12. Ohio Dept.
of Highways

"My CIE Course enabled me to pass both

the 2nd and 1st Class
License Exams on my
first attempt...I had no
prior electronics train-

ing either. I'm now in charge of Division

Communications. We service 119 mobile

units and six base stations. It's an interesting, challenging and rewarding job. And
incidentally. I got it through CIE's Job
Placement Service."
ENROLL UNDER NEW G.I. BILL: All CIE
courses are available under the new G.I.
Bill. If you served on active duty since
January 31, 1955, OR are in service now,
check box on reply card for G.I. Bill

Mail Card for Two Free Books

Want to know more? The postpaid reply card
bound -in here will bring you free copies o
our school catalog describing opportunitie.
in electronics, our teaching methods, and ou
courses, together with our special booklet
"How to Get a Commercial FCC License.'
If card has been removed, just mail the coupon at right.

information.

Cleveland Institute of Electronics

1776

E.

2 NEW

CIE CAREER
COURSES

CIE

mitter Operation

Cleveland Institute of Electronics j

44114

am especially interested in:

Electronics
Technology

Electronic

Broadcast

Engineering

Industrial
Electronics

First Class

Electronics

Communications

license

Engineering

Name
(PLEASE. PRIM71

2. ELECTRONICS ENGINEERING...covers steady -state and tran.

sient network theory, solid state physics and circuitry, pulse
techniques, computer logic and mathematics through calculus.
A college -level course for men already working in Electronics.

O.

license.`

FCC

FCC

1. BROADCAST (Radio and TV) ENGINEERING...now includes

Video Systems, Monitors, FM Stereo Multiplex, Color Trans-

17th St., Cleveland,

Please send me without cost or obligation:

Your 44.page book "How To Succeed In
Electronics" describing the job opportuni.
ties in Electronics today, and how your
courses can prepare me for them.
Your book on "How To Get A Commercial

Address
City
State

Zip

Age__

Check here for G.1. Bill information

PE -O7

1776 East 17th Street. Cleveland. Ohio 44114 !'..4j

L
CIRCLE NO. 6 ON READER SERVICE PAGE

October, 1970

91

www.americanradiohistory.com

COMMUNICATIONS

CONTINUED

plus frequencies for a 5 -watt command unit. The miniature transmette s would be
installed by utility companies and connected to water, electric and gas meters.
Information on customer usage would be put in digital code and the miniature
transmitters interrogated by a command unit in a high- flying plane! Read ex says
that an area of ten thousand square miles can be covered in one flight and the
readings would be recorded on tape. Big Brother and 1984 are getting closer!
AMATEUR RADIO
Novice or Technician Exams -- Would -be hams in the state of Washington
may take their Novice or Technician class exams at one of the following
locations: Amateur Radio Supply Co., 6213 13th Ave. South, Seattle;
G &C Electronics, 2502 Jefferson St., Tacoma; and HCJ Electronics, 8214
Sprague Ave., Spokane. R. E. Aspinwall, W7PV, says exams are year- round.

CITIZENS RADIO (CB)

Channel 11 -Now that the natter of channel

(exclusively for emergency traffic) has
been settled, REACT National Headquarters
has proposed voluntary nation-wide adoption
of channel 11 for inter -licensee calling.
Emphasizing that channel 9 had originally
been used for intra-station and inter- station
calling, a new, nationally recognized
"calling" frequency must be sought.
REACT says that channel 11 appear, to be an
agreeable choice to most clubs, REACT teams,
and CB magazines. POPULAR ELEt;TRONICS
agrees also.
9

SHORTWAVE LISTENING

Clarification -Radio Nederland'. Tom Meyer

has corrected some misinformation that
appeared in Hank Bennett's June 19-0 SWL
column. First, tape recordings to Radio

Nederland for verification need not he ONLY

71/2 in. /s; but may be any speed, any track
arrangement, and even in cassettes. Also,
Tom's show is not a listener's request
program, although he is filing away his
regular listeners' preferences (and birthdays).
Musical requests are handled by Jerry and
Dody Cowan's "His and Hers" on Tuesdays and
"By Request" on Mondays and Fridays.
-

Keith Glover

Compere "Mail)
Radio Austral,a

Antusunce

Due to lack of space, we omitted Keith Glover's

picture from last month's interview with Richard
Wood. Still looks good, though, so here it is now.

SHORTWAVE LISTENING

Jamming It Up -The Sino- Soviet communist block countries are

gradually intensifying jamming of international shortwave broadcasts.
Practically all broadcasts beamed to the Soviet Union and mainland China
are being jammed. On August 1, a sweep across the 19 -meter band showed
jamming on the following frequencies (practically a new high) 15,105;
:

15,115; 15,125; 15,130; 15,145; 15,170; 15,205; 15,215; 15,225;

15,260; 15,280; 15,290; 15,300; 15,340; 15,370; 15,380; 15,390; 15,440;
and 15,445 MHz. Because of the splatter, this means that about
25
92

percent of the possible broadcasting frequencies are useless.

POPULAR

ELECTRONICS

SHORTWAVE LISTENING
1 -Space scientists are still perplexed by the telemetry
China's 380 -lb satellite Chicom 1. Some specialists
mainland
from
claim that it wasn't telemetry at all- simply the tag end of a tape
recording made to sound like something important. Thousands of SWL's
heard Chicom 1 on 20.009 MHz during its short life -an indication
that battery power was used in this 5- plus -watt transmitter. Tape
recordings mailed by SWL's to Peking have not been acknowledged
according to the latest information -much less "verified." Experts
are now partially convinced that the 20.009 -MHz frequency was chosen
not out of respect for the ITU, but as a convenience since Peking
monitors the Soviet Cosmos series on 19.995 and 20.005 MHz.

Chicom

BROADCAST BAND

there's a will, there's a way; and since AM

stereo they can get it from XETRA,
want
listeners
-band
broadcast
Tijuana, Mexico. Stereo enthusiasts are advised to get a second AM
receiver and tune one receiver to the lower sideband of the 690 -kHz
AM signal and the other receiver to the upper sideband. Reports from
southern California about the quality and stereo effects are mixed,
but at least it's there for the tuning. (Submitted by Larry Sharp)
Mexican Stereo -Where

CITIZENS RADIO (CB)

Unique Noise Silencer -Introduction of the "Noise Eliminator" Model CE -0 -05

by Omega-t Systems Inc., opens exciting new possibilities in mobile operation.
Intended to supplement the built -in CB transceiver noise limiter, the Omega -t
solid -state (18 transistors, IC and 11 diodes) device enables 100c copy
of weak signals even in the midst of a traffic jam. Besides eliminating noise,
the unit also acts as an r -f preselector. Basic operation (patent pending)
is to take incoming signal and compare it with noise on a nearby frequency.
It then makes pulses from the noise bursts and, when pulses exceed a preset
level (adjustable by operator), shifts the received frequency, which effectively
switches off the preselector and quiets the transceiver. Only three connections
are necessary to use the unit: antenna in, antenna out, and 12 -volt dc power.
1

SHORTWAVE LISTENING

They Can't Do That To Us- Canadian shortwave listeners, police and

fire signal buffs, feel that their Department of Communications has
"flipped." In an apparent, but ill- advised, effort to stop unrestricted
listening to police radio signals, the DOC has issued a new ruling that
requires an SWL to have a "Private Commercial Receiving" license in
order to listen to anything above 138 MHz. And, to add insult to injury,
the SWL must also have permission from the stations he wants to hear
in order to be granted the special license. According to reports in
the Canadian magazine Electron, Department of Communications
inspectors are not paying a great deal of attention to this new rule.
RESEARCH

Death of a Radar Echo --Try, try again, scientists are working on

a "different" approach to the absorption of UHF radar signals. Laboratory
tests indicate that a ballistic missile with recessed resonant antennas
beneath an aerodynamically true-but transparent skin-will absorb
UHF energy. If enough is absorbed, the echo return can be
weakened to a point where detection at great distances is impossible.
Stumbling blocks to implementing this idea concern not only mechanics
of preparing missile skin, but determining Sino- Soviet radar frequencies.
(Continued on page 116)
93

October, 1970

www.americanradiohistory.com

STEREO SCENE
o

am

Second in a Monthly Series by J. Gordon Holt

THERE IS SOMETHING about loudspeak11

that brings out the "kook" in people.

Rational human beings, who would never

think of designing their own amplifier or
phono pickup, somehow get the idea that
they have found The Answer to the loudspeaker problem; and the less they know
about what they're doing, the more convinced they are that they are on the right
track.
Perhaps this is because loudspeakers are
less amenable to "instant objective analysis" than other audio components, and have
gained a reputation for being arcane, occult
devices, the science of which is more of an
art than a science. It is only a short step
from the observation that "measurements
don't tell the whole story" to the conclusion
that "the sound is what counts." Thus, an
ardent home experimenter, blissfully ignorant of the pertinent laws of physics but
with strong convictions about how things
should sound, hits upon an earth -shaking
idea that is so simple, so beautifully basic,
that it is a wonder nobody ever thought of it
before.

MUCH

FLEXING

Produce and Reproduce. The conviction

that the method by which music is produced

must perforce be the correct way to reproduce music has resulted in some of the
worst -sounding and oddest -looking speakers
that have ever been made. One such design,
that "worked like a pipe organ," used a
dozen or so tubes of different lengths,
bundled around one another and coupled at
one end to a small loudspeaker. The inventor
claimed that the loudspeaker would excite
the "pipes" into resonance, just like a "majestic cathedral pipe organ." Predictably, it
resonated horribly at a dozen or so different
frequencies.
Not all speaker-cum -musical- instrument
designers are unsophisticat d hobbyists,
though. The inventor of one speaker -thatworked -like -a- violin was a r petted audio
engineer whose idea also wei t awry. This
device, called the Bi-Phonic Coupler, used
as its radiating surface a wooden panel of
"specially selected woods," to produce the
"warmth and richness of a fine violin." Like
almost all designs that reproduce music "the
way music is produced." it added its own

SOME

FLEXING

flat surface, with minimal rigidity, moves a relatively large

amount in reproducing necessary
A

sound. The stiffness of the ra-

diator is increased significantly, without affe ting the mass

when surface is siaped into cone.

VOCE
COIL

FLAT PAPER
RADIATOR

94

CONICAL PAPER
RADIATOR

Electronics

POPUZ

ELECTRONICS

sonic characteristics to every sound it reproduced, including the sound of a violin.

Fortunately for us listeners, most loudspeaker designers know what they're doing.
Some have access to computers that can
draw a frequency response curve from a
given set of design parameters. But not even
the best technology can avoid occasional
goofs. In fact, the only way to ensure perpetual success in loudspeaker design is to
play it safe. Build a nice, conventional paper cone speaker and try, if you can, to forget

about the mathematical analyses.

The paper -cone speaker has been the
"standard" design for over 50 years, and
nobody can deny that today's versions are a
whale of a lot better than they were in 1920.
On the other hand, nobody can deny that
paper leaves much to be desired as speaker
cone material.
If a loudspeaker diaphragm or cone is to
reproduce a wide range of frequencies, it
must embody two properties that happen to
be mutually antagonistic: Large size and
light weight. To reproduce bass, it must
move a considerable volume of air in order
to create the necessary long-wavelength air
disturbances. You can do this by using a
smallish radiating surface and driving the
daylights out of it, or you can use a very
large radiating area and just barely tickle
it; but however you do it, you must move the
entire radiating surface in order to move
enough air. Since the diaphragm is pushing
air, its whole surface encounters some resistance to motion, and because the driving
element (usually a voice coil) is generally
much smaller than the total diaphragm area,
the diaphragm must be very rigid if the
driven area is to carry the whole surface
back and forth with it. And, almost inevitably, adequate rigidity usually means heavy
weight.
On the other hand, high- frequency reproduction and the concomitant ability to start
and stop rapidly on demand require that the
diaphragm be free from inertia. And there,
in a nutshell, is the Loudspeaker Problem.

Material's the Thing. A flat surface has

minimal rigidity. Forming the flat surface
into a conical shape increases the stiffness
significantly without affecting the mass; but
beyond that, the crucial factor becomes the
material that is used. Certain kinds of paper
can provide a good compromise between
mass and stiffness, and can also have good
internal damping characteristics to minimize resonances. But paper is always a compromise.
Experimental speaker diaphragms have
been made from almost every conceivable
material that looked as if it might have the
right mass /stiffness ratio. Soft materials

RIBBON
DIAPHRAGM

MAGNETS (FASTENED
TO REAR FRAME)

The Ge -Go "Orthophase" speaker had a long folded

ribbon fastened to rear of flat diaphragm with a

grooved magnet assembly interleaved with ribbon.

have excellent self-damping properties, but

lack the necessary stiffness. Hard materials

like metals have excellent stiffness properties but little internal damping, so they tend
to resonate so characteristically that it is
often possible to tell from their sound the
material used to make the diaphragm.
There were a couple of successful nonpaper designs. The IMF speaker, with a solid
foam -plastic "plug" instead of a thin cone,
and the Leak "sandwich" speaker, with two
metal skins and a cone of polystyrene sandwiched between two layers of damping material, sounded so much like good paper -cone
speakers that they prompted some people to
wonder if the Speaker Problem was not so
much the paper as the cone itself.
One interesting non -cone design was the
Kelly ribbon tweeter, an English product
that was essentially a somewhat oversized
version of a ribbon microphone, and functioned in exactly the same manner, only in
reverse. Still in production ( like the Leak
sandwich) and popular among English hobbyists, the Kelly tweeter yields exceedingly
smooth, extended highs but has limited power- handling ability. An intense cymbal crash
or a transient burst of system oscillation,
and the ribbon can disappear in a flash.
Unlike previous designs, the ribbon trans ducing element in the Kelly tweeter is also
its radiating surface, and this surface is
driven by the magnet assembly, so stiffness
is not a consideration, even had the design
been intended for low- frequency reproduction. The idea of a uniformly driven transducer element offers a promising way of
driving a very large radiating area without
demanding too much of it in the way of
rigidity.
,

95

October, 1970

www.americanradiohistory.com

in push -pull electrosta le speaker,

the flexible plastic she t is either
attracted or repelled by e opposing
charges on the wire g ids. Design
must be large for good bass reproduction, but it makes good tweeter.

SLIGHTLY
CONDUCTIVE

FLEXIBLE
PLASTIC
SHEET

WIRE
GRIDS

STEPPED -UP

INPUT
SIGNAL

HIGH -VOLTAGE'
POLARIZING SUPPLY

In the French Ge -Go "Orthophase" speaker, a long, folded ribbon was fastened to
the rear surface of a flat foam -plastic diaphragm, and the ribbon interleaved with a
grooved magnet assembly. The principle
was the same as the Kelly: a ribbon microphone in reverse, but this one could move
plenty of air. It sounded very good, but was
costly to manufacture and, in order to yield
deep bass, it had to be larger and costlier
than most people were prepared to accept
for something that still didn't sound remarkably better than a good paper -cone speaker

system.
Meanwhile, some other designers had given up on the magnetic transducer and were
investigating some entirely new actuating
forces for speakers. One promising idea that
was first brought to commercial refinement
by England's Peter Walker was to utilize
the same force that causes a lady's Nylon
underwear to cling tenaciously to anything
it touches in dry weather -electrostatic
force.
As its name implies, static electricity is
a concentration of electrons that aren't going anywhere (usually because they are on
a nonconducting surface) Although they
aren't moving, their negative charge exerts
an attraction on any nearby object that has
less of a concentration of electrons; and this
attraction tends to draw the two objects
together. If both objects have their respective charges spread evenly over their surfaces, the force of attraction will be uniform
over their entire surface areas, and if, by
design, one object happens to be a flexible
plastic sheet and the other a stationary grid
of wires, the sheet will move toward the grid

like the theoretically perfect loudspeaker

diaphragm.
The nice thing about this arrangement is
that, since the moving surface is uniformly
driven, it needs virtually no stiffness, which
in turn means practically no esonances.
And with stiffness out of the picture, the
diaphragm can be extremely thin, for maximum transient response.
The electrostatic speaker was one of the
I

96

Corona -wind speaker has high -voltage charge on

two elements to move air molecules tetween them.
POPULAR ELECTRONICS

non -paper designs that did sound markedly

better than the cone type of speaker. The
design is rather less costly than the Ge -Go
to manufacture, but it still must be physically very large in order to reproduce deep
bass. It makes an ideal tweeter, though.

Air is a Possibility. If an extremely

lightweight diaphragm could reproduce
sound so well, it seems reasonable to assume
that no diaphragm at all would be better
still. But without a diaphragm, how do we
move air? Easy, use the air itself!
Some years ago, there were rumors of a
fabulous loudspeaker design that could, literally, reproduce from do (0 Hz) to the
middle of the AM radio broadcast band. It
was called the corona -wind loudspeaker, and
it used the attraction between charged air

One air-pushing speaker that did get into

production, though, is the so- called blue glow tweeter developed by the French
Audax company and first manufactured in
the U.S. under the name Ionovac. This produces sound in the same manner as a lightning bolt -through intense heating, and consequent expansion, of the air. A high -voltage
supply creates a continuous disc- shaped
spark between two concentric electrodes.
Audio impulses are stepped up and fed to
the same electrodes, where they tend to
cancel or reinforce the supply voltage, thus
varying the intensity of the spark and hence
the amount of heat it generates. As the
spark is only about 1/s inch in diameter, and
paper -thin, it can't move much air on its
own, but with the assistance of a small horn
in front of it, it functions rather efficiently

One of first omnidirectional

speakers was the Hegeman
lily cone tweeter aimed up
at top of an open column
cabinet with woofer in the
bottom. The fragility of the
cone was its downfall.

AIR
MOVEMENT

molecules to draw the air back and forth

through a grid -like contraption that resembled two bed springs with Yogi -style
spikes between them. When a high -voltage
charge was placed across the spikes, air
molecules between them would become ionized and would be drawn toward one or the
other set of spikes, depending on the polarity
at the moment. With do applied, there would
be a steady flow of air, and with no inertial
elements involved ( theoretically, anyway) ,
there should be no limit to the speaker's
upper -range response.
Some people who heard a prototype of the
corona -wind speaker reported that it showed
"promise," but wouldn't commit themselves
further. Evidently, the promise was never
kept, for it never got into production. Maybe
the cost would have been prohibitive -like
other flat -panel systems, the speaker would
have had to be very large in order to plumb
the lower-bass regions.

as a tweeter, with a virtually unlimited high end range and unusual freedom from peaks.
The Ionovac was subsequently made by
DuKane Corporation and, more recently, by
Electro- Voice, and is still popular with perfectionists as a range -extending tweeter,
although its tendency to wear down electrodes and generate distressing amounts of
ozone has discouraged its widespread use.
Before stereo, a home hi -fi loudspeaker's
beaming tendencies were mainly of academic interest to designers. If the highs collapsed off -axis, so what? The speaker just
sounded a bit mellower. But along came the
second channel, and suddenly speaker directionality was an important consideration.
On -axis beaming causes poor center fill and
limits the area in the room from which the
listener can hear good stereo. The byword
was 30- degree sound, and there were some
interesting variations on that theme, too.

(Continued on page 112)

97

October, 1970

www.americanradiohistory.com

OPPORTUNITY
AWARENESS
Thoughtful Reflections On Your Future
Seventh in

Those "Mysterious" Out -of -Town Jobs

One story after another in the periodicals
tells of the shortage of electronics technicians and how employers are screaming
for help. I've completed an electronics
technology course, graduating with high
scores, and have a commercial FCC license.
But, where are the guys who wrote those
articles? Where are the jobs? They are not
in my area and the only places I know that
have any openings are New York and Los
Angeles -the last two places I'm interested

Monthly Series by David L. Heiserman

portunities exist at the moment of graduation. Without the help of a school placement
service, you are on your own. Since, apparently, your school did not have a job placement service, it would be well to examine
the three industries that are interested in
electronics technicians. These are detailed
in the Table.
Kind of Industry

Kind of Business

Manufacturing

Aerospace

ssembly lead man

Communications
Computers

uality control
inspector

Instrumentation

est

Components

esearch and

in living.

Statistics from the U.S. Department of

Labor show that there is an ever -increasing
shortage of trained electronics technicians.
Possibly, some of the articles that you have
read misinterpret these statistics and ignore the hard realities that not every single
electronics manufacturer in the nation is
suffering from a shortage of help all the
time. There are even whole areas of the
United States that have shortages one or
two months a year, and a surplus of technicians the remainder.
Your situation is aggravated by the fact
that you live in a town with a population
under 4000 people and in the state of Idaho,
which is not particularly well -known for its
electronics industry. I feel that anyone taking a home study course in electronics, or a
recent home study graduate in electronics
technology should face up to the fact that
there are plenty of towns that have absolutely no need for electronics technicians.
It may be hindsight, but anyone enrolling
in a home study program should always
make sure that the school has a good job
placement program for its graduates. The
school should also provide some sort of free
resume writing service. There should also
be school counsellors to help graduates prepare resumes and to be able to direct those
graduates to cities where employment op98

Technicians' Jobs

development

Communications

Commercial
broadcasting
Private companies using
radio equipment

representative
adio engineer
or monitor
aintenance and
troubleshooting

Government
agencies using
radio equipment
Radio and TV

Research and

Development

Repair
Universities
Private research
foundations
Government research

lectronic research
technician
nstrument maintenance and
repair

facilities

From this table, make a tentative decision as to the type of a job ou would like.
Don't be too narrow in your selection and
always bear in mind that manufacturers
POPULAR ELECTRONICS

are looking for men with experience and

you may find it necessary to lower your
sights in order to gain that necessary experience for a better paying job.
Employers are not standing in dark door ways grabbing up every electronics technician that passes by. It is, however, true that
some employers and manufacturers are
"screaming for more help." The trick is to
find those employers. There are about eight
major areas in the country always looking
for good electronics technicians -excluding
New York City and Los Angeles. These
areas are Boston, Denver, St. Louis, Baltimore /Washington, Chicago, and Houston/
Dallas /Fort Worth.
If you have the opportunity to visit any
of these cities, your problem is practically
solved. If not, try to obtain a complete edition of one of the major Sunday newspapers
containing all of the classified employment
advertisements. You will invariably find at
least several dozen job openings in any of
the cities mentioned above.
If you can't find the Sunday newspaper,
try your local library and see if they by any
chance have a few of the major city telephone directories-particularly the so- called
"Yellow Pages." Select some promising
looking companies and send a resume to
those companies. Don't hesitate to saturate
a particular area.
If you don't like the idea of moving into
one of the above areas, there are still several tricks left. Find a smaller town that is
the site of a major state university. Not all
of the large state universities are in major
cities. The University of Illinois, for example, has a lot of government- sponsored research work and is in the town of Champaign-with only a population of about
50,000. Such colleges nearly always have
openings for electronics technicians interested in working in various scientific projects.

For a complete listing of colleges and

universities, consult the "World Almanac."
And, for a listing of land grant colleges.
write to the National Association of State
Universities and Land Grant Colleges. Ask
for their free "Fact Book." The address is:
1785 Massachusetts Ave., NW, Washington,
DC 20036.

The last suggestion I can make is to attempt to find work through a competent
and reputable employment agency. There is
only one nation-wide employment agency
that will handle clients not living in the
major cities. This agency has about 400
offices and I would suggest that you write
directly to the attention of: Mr. Howard
Benner, International Headquarters, Snelling & Snelling, 2 Industrial Boulevard,
Paoli, Pennsylvania 19301.

Job Opportunities in Australia

I have been told that the Australian Government pays the traveling costs for immigrants
from the United States. Is this true? If so,
what are the chances of my getting a job
there in electronics? I have worked as an

electronics technician for three years, and I

have a diploma from a reputable home study
school.

According to Mr. K. E. Scott of the

Australian Embassy in New York City, the
Australian Government welcomes immigrant settlers from the United States and
Europe. The Government pays about $375
(U.S. dollars) towards the fare for adults,
and approximately $400 for every child under 19 years of age. This so- called "passage
subsidy" is Paid after you arrive in Australia.
To learn something about up-to- the -minute employment opportunities for electronics technicians, we consulted Mr. P. H. Cook,
Secretary of the Australian Department of
Labour and National Services in Melbourne.
"The unemployment rate is only a little
more than one per cent of the total workforce in Australia," Secretary Cook says.
"In the professional, semi -professional, and
skilled electrical fields (which includes electronics) the number of unfilled vacancies
exceeds the number of job seekers."
Speaking of the places where electronics
technicians and engineers work, the Secretary says, "In the more heavily populated
eastern States of Australia there is a strong
demand for experienced electronics engineers and technical personnel. In these
States, the large firms, located mainly in
Melbourne and Sydney, are engaged in the
production of a variety of telecommunications equipment, instrumentation and control systems, electronic componentry and
radio and television receivers."
The chances of an American immigrant
getting a job with the Australian Government Departments are slim, ". . because
of the requirements that applicants for such
employment be British subjects."
"Employment opportunities in the other
States of Australia occur less frequently,
with occasional vacancies arising for specialists in communications or control systems work, and there are good prospects
for instrumentation engineers in those
States in which major processing plants
are located.
The commercial TV field is well-established and growing. Color TV is still a
novelty, but the predicted popularity of
color TV will open new positions for hundreds of skilled technicians and engineers.
(Continued on page 114)
.

99

October, 1970

www.americanradiohistory.com

SOLID STATE
One Hundred SeventyThrd in a Monthly Series by Lou Garner
AMONG the predictions for 1970 in our
January column, we anticipated the development of a new solid -state memory system suitable either for a computer or,
possibly, an "electronic" camera. Although,
quite frankly, we considered this prophecy
a little on the wild side, we can now thank
Bell Telephone Laboratories (Murray Hill,
N.J.) for turning our prediction into a

reality.
At Bell Labs, Drs. Allen Meitzler, Juan
Maldonado, and David Fraser have been
working with solid -state devices which can
store picture images until electronically
erased or changed. Imagine a reusable 35mm slide on which an operator can electronically erase all or part of the image, add
new material, and then project the new
image on a standard screen.
Called "ferpics" (for ferroelectric picture)
the new devices are based on the electrooptic properties of fine -grained lead zirconate -lead titanate, a ferroelectric ceramic
material first announced by the Sandia Corporation.
In its basic form, the ferpic is a sandwich
structure consisting of transparent electrodes, a photoconductive film and a thin
plate of ferroelectric ceramic. This basic
sandwich is bonded to a transparent substrate which is then flexed so as to stretch
or "strain" the material. Using this "strain biasing" technique, Bell Labs scientists were
successful in changing the stored information in the basic structure.
On a conventional photographic slide, the
image is stored as variations in the transparency of the film. In a ferpic, on the other
hand, the image is stored as a variation of
the birefringence of the ceramic plate -that
is, as a variation in the way the plate transmits polarized light.
In one mode of operation, a scanned laser
beam records an image on the photoconductive film, one picture element at a time, much
as a TV image is formed. A voltage applied
to the transparent electrodes develops a field
across the ceramic. When the field is removed, the image remains stored on the
100

ceramic plate. The resulting image can be

viewed directly by putting light polarizing
sheets over it or, if prefered, the image can
be projected onto a conventional screen using
polarized light.
To erase the image, the entire structure is
flooded with light in the presence of a reversed electric field. Afterwards, the plate is
ready to store another image.
At the present stage of development, Bell
Lab scientists have demonstrated that ferpic devices can store and display, with good
resolution, black- and -white images that have
a relatively long lifetime before fading. Present ferpics are suitable for the display of
written text or figures, since suc applications, although exploiting the unique image
storage capabilities of the device, do not
place severe demands on the speed or lifetime of the ceramic material.
Further experiments are being carried out
in the hope of obtaining efficient, low -cost

Bell Laboratories' Juan Maldonado ad usts focus of

image from ferpic device on small viewing screen.
POPULAR ELECTRONICS

low -cost light- emitting diodes now being

offered by Motorola, Hewlett Packard, and

Monsanto can be used in a variety of interesting applications other than as simple re-

placements for conventional pilot lamp

bulbs. He submitted the three basic experimental circuits illustrated in Fig. 1 as examples of how these intriguing little units
can be used with other active semiconductor
devices. All three circuits are suitable for
breadboard tests, science fair demonstrations, or as sub-systems in complex equipment designs.
Useful in a visual metronome or as an
attention -getting indicator for intrusion or
process alarm systems, the blinker circuit
RI

47K

Same negative made original print at top and one

from the ferpic storage device (directly above).

solid -state information displays with features that are difficult to obtain in present
display systems. Since the stored image can
be projected, very large displays may be

obtained. In addition, ferpic slides can retain

images for a long time without electrical
power, in contrast to other electro- optical
memory systems.
Still considered laboratory devices, ferpics
probably will not be available in commercial
versions until at least mid or late 1971. But
serious experimenters can look forward
one day-to the prospects of working with
another new and exciting solid -state device.

D.

POWER
SUPPLY

LOSE

(C)

Reader's Circuit. Sometime author and

regular reader Luis Vicens (Box 1546,
Wheaton, Md. 20902) writes that the new

Fig. 1. Circuit (A) is relaxation oscillator blinker,

(B) is dual blinker, and (C) is polarity reversal

alarm,

all

using

October, 1970

unusual

light-emitting diodes.
101

www.americanradiohistory.com

new

19 -piece midget

shown in Fig. lA teams an LE D with a pro grammable unijunction trans. stor (PUT),
Q2, in a simple relaxation oscill ator. In operation, Cl is charged by Bi thr )ugh RI until
Q1's breakdown (or "firing" voltage is
reached, as determined by v ltage divider
R2 -R3, at which time Q1 switc hes to a conducting state, discharging Cl through the
LED and activating this device. The entire
cycle is then repeated at a rate determined
by the supply voltage, R2 -R3's ration and
Ri-Cl's time constant. The LED may be
either a Motorola type MLE 600 or Monsanto type MV50, and with 41e component
values shown, the repetition r to is approximately 100 flashes /minute and the current
drain about 0.5 mA. The flashing rate can be
reduced by using a larger valued capacitor in
place of Cl and vice versa.
The alternating dual -blinker circuit given
in Fig. 1B may be used alone as a simple
demonstration or can be incorporated into
such projects as electronic toys, games, and
advertising displays. Transistors QI and Q2
are used as a conventional collector-coupled
multivibrator, with their resistive collector
loads replaced by LEDs. As in any multi -

reversible
ratchet offset
screwdriver set
3 -3/4" heavy duty, stainless steel

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Unique 6" spinner/extension has drive
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vibrator, the circuit's repetition (flashing)

rate is determined by its R-C time constants.
Referring to the diagram, the LEDs are
Motorola type MLED600 or Monsanto type
MV50, with transistors QI and Q2 general
purpose pnp types similar to RCA type

hex to 1/4" square adapter bit

permits use of ratchet or
spinner/extension with Xcelite Series
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2N109.

In operation, the two LED's flash alternately about once per second with the specified component values. The flashing rate can
be increased by using lower values for Cl
and C2, decreased by using larger valued
capacitors. Assuming a symmetrical circuit
( matched components ) the LED's will flash
alternately for equal intervals. If the planned
application requires unequal flashing periods,
different value coupling capacitors (CI, C2)
may be used. Typically, with Cl larger than
C2, LEDI remains lit for a longer period than

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LED2.
A combination do polarity reversal alarm
and protective circuit is shown in Fig. 1C.
Suitable for use with mobile transmitters,
receivers, p.a. systems and test instruments,
the circuit will protect the equipment against
catastrophic damage if the power source's
dc polarity is reversed and, at the same time,
will flash a warning signal for the operator.
The circuit may be built in as an integral
part of a new design or assembled as an outboard accessory for existing equipment.
In operation, rectifier diode D1 is forward biased when correct do polarity is applied
and, therefore, does not interfere with equipment performance. The LED is reverse biased, but at a very low voltage (i.e. Dl's
IR drop), and thus remains dark. If the
POPULAR ELECTRONICS

SYDMUR

supply voltage polarity is reversed, whether

accidentally during hook -up or as a result of
external equipment failure, Dl is reverse biased and, acting as a high resistance, prevents equipment damage. The LED, on the
hand, is then forward- biased and activated,
thus signalling the operator that there is a

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problem.
As in previous circuits, the LED is an
MLED600 or MV50. Protection diode Dl
can be any silicon rectifier capable of handling the equipment's load current and with
a PIV rating at least twice the supply voltage. Resistor Rs is a half -watt or one -watt
resistor, with its value determined by Ohm's
law to limit the LED's voltage and current
within the device's maximum ratings. Simply
subtract the LED's maximum forward voltage from the source voltage and divide by
the average operating current. With a 9 -volt
source, for example, a 200- to 240 -ohm resistor may be used.

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"TA -TA!" In the past, we've occasionally

featured experimental circuits using RCA
devices with a "TA" prefix in their type number. An example is the TA5371B IC featured
in our June 1970 "Manufacturer's Circuit."
The TA designation is used by RCA to identify development devices-those in pilot, but
not yet full, production or those not yet n-signed a commercial, JEDEC, or EIA typt
number. TA type devices are not stocked by
distributors but, as a general rule, can be
obtained on special order through franchised
RCA semiconductor dealers or direct from
the factory.
Often, due to publishing deadlines, a standard stock type number will be assigned by
RCA before a device reference appears in
print but too late for a change to be made in
final copy. The TA5371B IC featured in our
June column, for instance, is now available as
a stock RCA device and is designated CA3062.

If you need a TA device for a special

project, first check to see if it is available
under a commercial stock number; if not,
then the device can be obtained only on
special order. A phone call to your local RCA
component representative check the Yellow
Pages) or a letter to the factory will give
you the information needed.
(

Manufacturer's Circuit. Although wide-

ly used and extremely popular for burglar

alarm applications, the standard light -operated relay can be defeated quite easily by a
clever thief. All that he needs is a flashlight
to intercept the light beam and he can walk
by as if on his way to a picnic. Using an invisible (infrared) beam helps some, but even
this will not deter a determined and skilled
intruder. One good solution to this problem
Popular Electronics

103

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For free li -terature and parts list write:

SYDMUR ELECTRONIC SPECIALTIES
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is suggested by Motorola engineer John

Bliss in his technical Applicatio is of Photo transistors in Electro -optic Sy4ttems. John
recommends the use of a modulated light
beam coupled to a frequency- densitive detector /amplifier. His complete paper, which
includes a wealth of other information, is
published by Motorola Semiconductor Products, Inc. (Box 20912, Phoenix AZ 85036)
as their Application Note No. AN -508. John's
frequency -sensitive detector /amplifier circuit is illustrated in Fig. 2.
The modulated light beam is detected by

phototransistor Q2, with the resulting signal

applied through common -base amplifier Q2
to FET preamplifier Q3. T1e preamp's
output signal is developed across, a potentiometer which serves as the system's sensitivity control. From here, the signal is capacitance coupled to two cascaded band -pass IC
amplifiers. A pair of parallel -T feedback networks establish frequency selectivity. The
amplifier's output is coupled to a diode detector and applied as base bias to Darlington
amplifier Q.4 which, operating in a saturated
state, effectively shorts out the SCR's gate
bias.
In operation, any interruption in the modulated light beam will result in a loss of Q4's
base bias, shifting this device away from its
saturated state and permitting a gate bias to
be applied to the SCR. Triggered into operation, the SCR switches power to an alarm
device, such as a bell, buzzer, siren, or floodlight. Once the alarm is actuated, it remains
on even if the light beam is restored, until
the system is reset by momentarily shorting
the SCR by a spst anode -cathode switch.
The modulated light beam needed for system operation can be obtained by pulsing
a LED, neon bulb, or low -power incandescent
lamp. Such sources are adequate for short
distances. If the installation requires a strong
light beam for a long "throw," however, a
pulsed laser or a high -intensity incandescent
lamp modulated by a motor -driven rotary
"chopper" can serve as the liglht source.
In practical installations, tte frequencies
of the two bridge -T networks are calculated
by conventional techniques, making sure that
they correspond to the frequency of the light beam transistor. Lenses would be used at
both the light source and detector, with infrared filters provided to obtain an invisible
light beam. Naturally, accurate optical
alignment of the system is essential for optimum performance.

Roll (Design) Your Own! Old -time cowboys used to pride themselves on their ability
to "roll their own" cigarettes with one hand.
If you use Siliconix FET's in your projects,
you'll now be able to outdo the legendary
cowpokes and "roll your own" circuit designs
104

POPULAR ELECTRONICS

i12V

012 V
5.1k

12 V

ALARM

2N4441

12 V

Fig. 2. Motorola- designed intrusion alarm amplifier /control circe it employs modulated light
(source not shown) to foil burglars; Q1, sensitive to frequency -modulated light, is detector.

with no hands, slide rules, computers, or

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circuit designs similar to the two -stage FET
amplifier illustrated in Fig. 3 without tedious
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New Heathkit Solid -State

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of 45 transistors, 55 diodes, 2 silicon controlled
rectifiers; 4 advanced Integrated Circuits containing another 46 transistors and 21 diodes;
plus 2 tubes (picture and high voltage rectifier) combine to deliver performance and reliability unmatched by conventional tube sets.
Exclusive design solid -state VHF tuner uses an

MOS Field Effect Transistor for greater sensi-

tivity, lower noise, and lower cross -modulation

you sharply superior color reception,

especially under marginal conditions. Gold/
Niborium contacts give better electrical connections and longer wear. Memory fine tuning,
standard. Solid -state UHF tuner uses hot-carrier diode design
for increased sensitivity.

...gives

picture tubes.
Choice of 295" or 227" picture tube sizes.

Adjustable tone control lets you choose the sound you prefer
...from deep, rich bass to clean, pronounced highs.
Hi -fi output permits playing the audio from the
set through your stereo or hi-fi for truly lifelike
reproduction. Another Heath exclusive.

Designed to be owner serviced.The new Heath solid -state color

TV's are the only sets on the market that can be serviced by
the owner. You actually can diagnose, trouble -shoot and maintain your own set.
Built -in dot generator and tilt -out convergence panel let you
do the periodic dynamic convergence adjustments required of
all color TV's for peak performance. Virtually eliminate technician service calls.

higher gain for better

overall picture quality. Emitter -follower output
prevents spurious signal radiation, and the entire factory- aligned assembly is completely
shielded to prevent external interference.

Snap -out glass epoxy circuit boards with transistor sockets add strength and durability and
permit fast, easy troubleshooting and transistor replacement. Makes each circuit a module.

Automatic Fine Tuning- standard on both sets. Just push a

button and the assembled and aligned AFT module tunes in
perfect picture and sound automatically... eliminates manual
fine -tuning. Automatic between- channel defeat switch prevents tuner from locking in on stray signals between channels.
AFT can be disabled for manual tuning.

Built -in Volt -Ohm Meter and comprehensive

manual let you check circuits for proper oper-

3 -stage solid -state IF has

VHF power tuning...scan through all VHF and one preselected

UHF channel at the push of a button.

Built-in automatic degaussing keeps colors pure. Manual de-

gaussing coil can be left plugged into the chassis and turned
on from the front panel ... especially useful for degaussing
after the set is moved some distance.

Automatic chroma control eliminates color variations under

different signal conditions.
Adjustable noise limiting and gated AGC keeps pulse -type interference to a minimum, maintains signal strength at constant level.
High resolution circuitry improves picture clarity and new adjustable video peaking lets you select the degree of sharpness
and apparent resolution you desire.

"Instant -On ". A push of the power switch on the front panel
brings your new solid -state set to life in seconds. Picture tube
filaments are kept heated for instant operation, and extended
tube life. "Instant-On" circuit can be defeated for normal onoff operation.
Premium quality color picture tubes. Both the 227 sq. in. GR270 and 295 sq. in. GR -370 use the new brighter bonded -face,
etched glass picture tubes for crisper, sharper, more natural
color. And the new RCA HiLite Matrix tube is a Bow cost option
for the GR -370. See below.

106

ation and make necessary adjustments. The

manual guides you every step in using this
built-in capability. Absolutely no knowledge of
electronics is required.

Easy, enjoyable assembly ...the Heathkit way. The seven -section manual breaks every assembly down into simple step -bystep instructions. With Heath's famous fold -out pictorials and
simple, straightforward design of the sets themselves, anyone
can successfully complete the assembly.
Heathkit Solid -State Modular Color TV represents a significant
step into the future... with color receiver design and performance features unmatched by any commercially available
set at any price! Compare the specifications. Then order yours
today.
Kit GR -270, all parts including chassis, 227" picture tube, face
mask, UHF & VHF tuners, AFT & 6x9" speaker, 114 lbs. $489.95*
Kit GR -370, all parts including chassis, 295" picture tube, face
mask, UHF & VHF tuners, AFT & 6x9" speaker, 127 lbs. $559.95*
Kit GR- 370MX, complete GR -370 with RCA matrix picture tube,
127 lbs.
$569.95
GR -270 AND GR -370

SPECIFICATIONS

Approximate Viewing Area:

TUBE SIZE: GR370

- PICTUREApproximate
Viewing

295 Sq. In. GR -270

Area: 227 Sq. In. DEFLECTION: Magnetic, 90 degrees. FOCUS: Electrostatic. CONVERGENCE: Magnetic. ANTENNA INPUT IMPEDANCE: VHF
300 ohm balanced or 75 ohm unbalanced. UHF: 300 ohm balanced.
TUNING RANGE: VHF TV channels 2 through 13. UHF TV channels 14
through 83. PICTURE IF CARRIER: 45.75 MHz. SOUND IF CARRIER:
41.25 MHz. COLOR IF SUBCARRIER: 42.17 MHz. SOUND IF FREQUENCY: 4.5 MHz. VIDEO IF BANDWIDTH: 3.58 MHz. HI -FI OUTPUT:
Output impedance 1 k ohm. Frequency response +1 dB 30 Hz to 10
less than 194 at 1 kHz. Output voltage
kHz. Harmonic distortion
ohm or 8
0.3 V rms nominal. AUDIO OUTPUT: Output impedance
ohm. Output power -2 watts. POWER REQUIREMENTS: 110 to 130
volts AC, 60 Hz, 240 watts. NET WEIGHT: GR -370, 114 lbs.; GR -270, 101
lbs.

-4

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Modular

for
erati onal

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... Circuit Boards snap l5'

for easy assembly, simple sery cing

Exclusive Modular Design

ITS FEATURED IN
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shorting
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Gun

Plug -in
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11

Plug -in
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Add extra convenience and versatility to your

new GR-270 or GR -370 Solid -State Color TV with
this new ultrasonic remote control kit. Lets
ycu turn the set on and off, adjust volume
change VHF channels and adjust color and
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adjustment a matter of minutes.
SNAP
Kit GRA -704, 6 lbs.

New Expedited 48 -Hour No- Charge Warranty Service Plan for Solid State TV Modules! Special service facilities have been established
at the factory and all Heathkit Electronic Centers to expedite
service and return of Solid -State TV circuit modules within two
working days. During the 90-day warranty period, TV modules will
be serviced or replaced with no charge for labor or parts. After
the initial 90-day warranty period expires, TV modules will be serviced or replaced at a fixed charge of $5.00 per module for labor and
parts for a period of two years from date of original kit purchase.

Choose One Of These Handsome, Factory Assembled Cabinets

3

models in 295 sq. in.

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Maple.

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Assembled .

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oil -

GRA- 301.23, 56

lbs...

$74.95

dandy Roll-Around Cart

and Cabinet Combination. Features the GRA 203-20 walnut cabinet
plus a walnut- trimmed
wheeled cart with storage shelf. Assembled
GRA -203.20 Cabinet, 45
lbs.
$49.95
GRA-204.20
Roll-Around
Cart, 18 lbs
919.95'
GRS-203.5,Cart Cattiest
Cembo, 58 lbs. $59.95`

$59.95

NEW

FREE 1971 CATALOG!

Now with more kits, more
color. Fully descr bes these
along with over 300 kits for
stereo/hi -fi, color TV, electronic organs, guitar amplifiers, amateur radio, marine,
educational, CB, home &
hobby. Mail coupon or write
Heath Company, Benton Harbor, Michigan 49022.

October, 1970

an

$114.95`

Cabinet and Base Combination. Handsome walnut finished cabinet sits

on a matching walnut
base. Cabinet dimensions 20- 31/32" H x 317/16" W x 184b" D. Base
dimensions 73/s" H x
273/4" W x 18q" D.
Assembled GRA -203 -20
Cabinet, 45 lbs. $49.95
6RS.203.6 above cab. w/
matching base, 58 lbs.

techniques and finished

In stylish Mediterranean
ecan.
Accented with
statuary bronze handle.

solids with

rubbed walnut finish.

29- 17/32 "H x 35- 13/16"
W x 19rh" D. Assembled

Contemporary Walnut

Mediterranean

... assembled

&

29-21/32" H x
W x 193/4" D. AsGRA -303 -23, 67

sembled
lbs.

GRA -304-23, 85

fine furniture

sembled of fine veneers

veneers and
finished in classic Salem

models in 227 sq. in.

Exciting

Cabinet... factory as-

woods &

can. Statuary bronze

trim handle. 30- 1/32" H
a 47" W e 173/4" D. As-

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American

Cabinet... factory assembled of a special

combination of hard

sembled of fine furniture grade hardwoods

and finished In a flawless Mediterranean pe-

sembled
lbs.

Early

Deluxe

Cabinet... factory as

SATHY_IT'
HEATH COMPANY, Dept. 10.10

Benton Harbor, Michigan 49022

Enclosed is $

Schlumbrger company

plus shipping.

Please send model (s)

O Please -send FREE

Hcathkit Catalog.

--t7- PInase-send -credit Application.

Name

Address
l

City

LMall order prices;

O.B.

State
Zip
factory. Prices & specif cations subject to change without notice.

CL -392RJ

CIRCLE NO. 14 ON READER SERVICE PAGE

109

www.americanradiohistory.com

CONTROLLED

STEREO SCENE

QUALITY

(Continued from pt ge 97)

CRYSTALS by

C RYSTEK
The "On- Channel" Crystals
"MARS" TOO!

NOW

Ms-ORDER

CRYSTALS

Your dealer has new. fast. direct- factory

ZIP Order Purchase Certificates to enable
you to get CRYSTEK CB. Monitor Amateur,
and Mars freq. Crystals mailed direct to
you promptly. Ask about them.
CRYSTEK

formerly Texas Crystals

Div. of Whitehall Electronics Corp.

1000 Crystal Drive
Fort Myers, Florida 33901

4117 W. Jefferson Blvd.

Los Angeles. California 90016

CIRCLE NO. 7 ON READER SERVICE PAGE

DISCOVER HIDDEN
TREASURE
A powerfully
sensitive instrument
detects gold, silver, coins,
relics, etc. Fully tested
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guaranteed,

Send

WITH A JETCO ELECTRON /C

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for Free Catalog

JETCO,

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up

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COOPERATE WITH
THE ZIP CODE

PROGRAM
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DEPARTMENT.
USE ZIP CODE
IN ALL. ADDRESSES
112

Omnidirectionality. One of the first

truly omnidirectional hi -fi speakers was the
brainchild of Stu Hegeman, an audio inventor of enviable reputation. This system had
an upturned woofer in a rectangular shaped
enclosure (standing on end) with a "cage"
of grille cloth at the top. Looking inside the
cage, directly above the woofer, you could
see a cute looking tweeter shaped like a lily
and made from what appeared to be stiff
paper. (The prototypes were actually handmade of ledger paper and the fine blue rules
could be seen.) The bottom end of the lily
was attached to a voice coil on the tweeter

assembly. The lily design proved to be a

very excellent high- frequency radiator and
the early prototypes of this Hegeman design
sounded superb, embodying a sense of depth
and openness that put practically every
other loudspeaker available at that time to
shame. Hegeman sold the manufacturing
rights of his system to Eico and it might
have been a commercial success were it not
for the fact that the speaker', system was too
fragile for interstate truck or rail shipment.
There were, and still are, other 360-degree
speakers of varying quality,; but one (happily discontinued) design probably established a record for disorganized thinking.
Advertised as a "360- degree speaker," this
little gem contained the usual upturned
woofer, but instead of an omnidirectional
tweeter, it had a small cone, tweeter aimed
horizontally that was rotated by a little
electric motor like a lighthouse beacon!
However, once per revolution, the rear of
the tweeter was actually aimed at the listener and the woofer /tweeter phasing was
reversed twice for each revolution, causing an
in -out modulation that was quite upsetting
to the listener. If this was 't bad enough,
the remainder of the syste left the midrange fairly muddled and no one of the con sumer hi -fi magazines did ore than mention this system in a cursory fashion. The
fact that the rotating tweete went over like
the proverbial lead balloon ith the buying
public is a tribute to their prspicacity.
On the other hand, the po ular hi-fi press
has had some nice things to say about the
Bose 901 speaker system, th first of a new
spate of "omnidirectional" d:signs. This system is based on the idea that what makes
360 -degree speakers sound so spacious is the
reflection of the rear radia ed sound from
the wall behind the system, t ather than just
the freedom from on -axis beaming.
The designer, Dr. Bose, is a professor of
POPULAR ELECTRONICS

acoustics at M.I.T. and a very capable and

knowledgeable audio enthusiast. He claims
that much of the music reaching the listener
in a concert hall consists of reflections arriving from the walls, which is of course true.
After an extended analysis of this effect,
Dr. Bose concluded that a speaker system
for the home should radiate about 89% of its
sound from the rear of the enclosure for reflection from the surrounding walls. This expands the stereo stage and produces (in the
home) a concert-hall type of listening environment.
Personally, I happen to be on the side
of those who say that the speaker system
should do no more than accurately reproduce
full -fidelity sound. Whether you should attempt to create conditions in your home
similar to a concert hall is to me quite debatable. Certainly there can be no disagreement that concert -hall reflections produce
the ambience information creating the feeling that the original sounds were made in a
very large "room." I feel that this ambience
information should be reproduced "as is" in
the home and that this should mean adding
as little as possible of the listening room's
"ambience" to the reproduced sound.
Those who have listened to a properly installed Bose 901 system cannot fail to be
impressed by the startling sense of spaciousness it provides. The system works as
claimed; however, unless it is very carefully
installed, listeners begin to notice that almost every sound across the stereo stage
seems to be stretched from left to right.
Mono material is strung out between the
speakers -a not unpleasant illusion for mono,
but a contradiction and an ill omen for stereo
reproduction.
You can achieve the spaciousness claimed
for the Bose 901 through very careful placement of the speakers. The phase relationship
between sounds emanating from the rear
speakers, reflected off the walls and reinforced by the sound from the front-facing
speakers appears to be quite critical.

KEEP IN TOUCH
WITH THE ACTION

pair

ndard

INTERFACE
a
MORE "BUG- SHOO"

I constructed your July project by Lyman

Greenlee and clipped it to my belt strap.
Potentiometer R3 was adjusted until I could
no longer hear the squeal. Now, while sitting
in an outdoor patio, I am the only person not
getting eaten alive by mosquitoes.
M. WkLDMAN

Philadelphia, Pa.
BETTER TV RECEPTION
George Monser's article on TV twinlead
"transformers" gave far better results than
anticipated. I live about 80 miles from channels 2, 4, and 5; and the improved matching
between antenna and receiver cut down
about 80% of the snow.
D. HASTING

Hemingway, S.C.

SUGGESTIONS
In line with your new editorial outlook,
how about projects on a magnetometer,
balanced induction metal locator, AM BCB
direction finder, and full- fledged lie detector
that records heart beats, etc?
J. WEGNER, JR.
Glendale, Calif.

Wortmai Ave., Brooklyn, N.Y. 11207

Please send information on the SONARCOM.
SONAR RADIO CORP., 73

Dept. 207

Other models available for

`--=

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frequency ranges

32.5- 41 -42 -50 MHz

1

Better performarce anc more featcres than much highe- priced

units
Engineered with space age techniques and military
type components for high reliability, superior performance and
long life
Full frequency range fcr all public safety. industrial
and land t-anspertation services
Provides instant voce contact with 5ase stations, mobile un is and other portable transceivers
compatible with all VHF narrowband system=_
1.6
watt output
FCC TYPE ACCEPTED and D.

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set of standard b,
teries less tones

(4,
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WE GET THRU - WHERE OTHERS FAIL!

SONARCOM
Available in

Proper speaker placement of ordinary

front -radiating systems is more critical than
most listeners realize. The Bose 901 certainly expands the stereo stage, but it seems to
be that, although the answer to achieving
optimum stereo reproduction in the home
may be closer at hand, it is still subject to
critical elements that not every listener has
the knowledge and provisions to overcome.

Title

Firm Name
Address
City

VHF &

UHF with and without tone

State

r-

CIRCLE NO. 24 ON READER SERVICE PA

October, 1970

Phone
Zip

:3E

113

www.americanradiohistory.com

K TEST EQUIPMENT

OPPORTUNITY AWp RENESS

(Continued from pa ge 99)

PRODUCT OF

OYNASCAN

FREE
preteauenel
Tool fOelDmect

1070-t071

Concerning other branches of modern

electronics, the Secretary states, "There is
also a demand for highly skilled men to install and maintain computer hardware, although Australian manufacture in this field
is at present concerned mainly with software. The development of fully electronic
telephone exchanges and the extension of
Subscriber Trunk Dialing services throughout Australia have meant great expansion
in the field of integrated circuitry. In addition, the Australian Government actively
encourages the local manufacture of microelectronic devices to meet both defense requirements, and the needs of the Post Office and Civil Aviation."

CATALOG
TV ANALYSTS
NEW FET TESTER
VOMs -VTVMs
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CIRCLE NO. 10 ON READER SERVICE PAGE

the

IIIIIIIIIIIIIIIIIIII

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With 500 Watt Coil

NOW AT POPULAR PRICES. Each model loaded

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Model 500A...With 500 watt solid -state high "Q" coil
a

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For details see your Mosley dealer

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CIRCLE NO. 18 ON READER SERVICE PAGE

1 Post St.
Crocker Plaza
San Francisco, CA 94104
Employment information
Dept. of Labour and National Service
P.O. Box 2817AA
Melbourne, Victoria 300]

Australia
Information concerning application for
professional engineering status or
higher education
Institution of Radio and Electronics
Engineers
Science House
157 Gloucester St.
Sydney, Australia

SERIES

E
R

OPPORTUNITIES IN AUSTRALIA
Immigration information (Eastern USA)
Australian Consulate General
636 Fifth Ave.
New York, N.Y. 10020
Immigration information (Western USA)
Australian Consulate General

Electronics and electrical engineers from

the U.S. can apply for professional engineer
ing status, and any technician or engineer
can further his education in the excellent
Australian schools. According to Secretary
Cook, "Professional recognition as an engineer in Australia depends upon acceptability to the Institution of Engineers,
Australia. Some employers stipulate that
applicants for positions in the engineering
field must have qualifications for graduate
membership in the Institution."
Salaries for electronics technicians and
engineers are from 3500 to 8000 U.S. dollars a year. Although these figures are low
by American standards, the cost of living in
Australia is somewhat lower, too.
-N7
114

POPULAR ELECTRONICS

free information service:

Here's an easy and convenient way for you to get additional information about
products advertised or mentioned editorially (if it has a "Reader Service
Numbe>') in this issue, Just follow the directions below... and the material
will be sent to you promptly and free of charge.

circle the number(s) that

corresponds to the key nurnber(s) at the bottom or next to the advertisement or editorial mention that is of interest to you. (Key numbers for
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On coupon below,

Cut out the coupon and mail it to: PO'ULAR ELECTRONICS,

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no

If you want to tivrite to the editors of

POPULAR ELECTRONICS about an article
on any subject that does not have a key number, write
to POPULAR ELECTRONICS, One Park Avenue, New
York, N.Y. 10016. Inquirie<_ ccncerning circulation
and subscriptions should be sent to POPULAR
ELECTRONICS, P.C. Box 1096, Flushing, N.Y. 11352,

POPULAR
r ELECTRONICS
1

21
41
61
81

22
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23
43
63
83

VOID AFTER NOVEMBER 30, 1970

P.Q. BOX 8391

PHILADELPHIA, PP 19101

4 5 6 7 8 9.10 11 12 13 14 15 16 17 18 19 20
24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
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NAME 'Print clearly)

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115

October, 1970

www.americanradiohistory.com

COMMUNICATIONS

PRODUCT GALLERY

(Continued from page 93)

(Continued from page 86)

SHORTWAVE LISTENING

Speech Scramblers-Next year we can celebrate the 70th anniversary of first attempts
at electronic speech scrambling-Alexander
Graham Bell tried it, but the results were
unimpressive. Local and state police are
increasingly concerned over the influx of
VHF /UHF monitoring receivers and speech
scrambling is being installed in an average
of three police communications systems per
month. The E. F. Johnson Co. has demonstrated a hand -held VHF transceiver with 6
possible modes of scrambling. It will sell for
about $1000 per unit-not considered too
high for the extra security. Scrambling can
be speech inversion, band splitting, frequency modulation, analog, or time division. Band
splitting was used during World War II for
supposedly secure messages between Roosevelt and Churchill, but the Nazis managed
to unscramble it.
CITIZENS RADIO (CB)

Canadians Get CB Reciprocity -In a sudden

unexpected move, the FCC on July 24, granted CB reciprocal operating privileges to all
Canadians coming into the U.S. with bona
fide GRS licenses. CB'ers from the States
have been able to operate in Canada for several years and a reciprocal arrangement had
been advocated by numerous CB organizations. Canadians must request permission
using FCC Form 410 (New Form 410 -B
after November 1) and should understand
the FCC Part 95 CB Rules and Regulations.
While in the States, Canadians use their
"XM" callsigns followed by a geographical
identification (city and state).

frequencies. A frequency response curve run

on the cartridge alone (tracking at just
under 3 grams) showed a response of 1
dB from 40 Hz out to 20,000 Hz. The channel-to- channel separation was better than
20 dB below 12,000 Hz and was still 10 dB at
18,000 Hz.

Speaker response tests were made to conthe tone burst method -that
the system had excellent respo se at all frequencies. Hirsch -Houck Labor tory subjectively reported (a.nd this re 'ewer subsequently confirmed) that the L ndmark 100
has very solid and healthy -sou ding bass in
the 50 -60 Hz region and that t e audio output is smooth and free of peaking out beyond the limit of normal hearing (say,
15,000 Hz)
As compact stereo systems go, the Landmark 100 is certainly one of the more unusual designs and one of the better sounding
systems that we have heard.'
to the
lack of "on- axis" beaming from the small
speakers that are usually supplied with compact systems, the Landmark 100 appears to
give the listener the ideal mix between direct
and reflected sounds and judging from the
response below 300 Hz the " ervo- Linear"
feedback system can really p rform in almost any listening environmen
One thing that I do dislike ab ut the Landmark 100 is the absence of FM interstation
hiss suppression or squelch. Jttst why this
has been eliminated is a mystery and I hope
that the next manufacturing run has this
additional minor circuit.
I apologize for not getting
the Avanti
"Astro- Plane" CB antenna in t is column. I
sometimes think I write too nu ch.

firm- through

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Amplified AVC constant AF output Price 5299.00

Write for free Brochure.

R. L. DRAKE COMPANY

Miamisburg, Ohio 45342

CIRCLE NO. 9 ON READER SERVICE PAGE

116

POPULAR ELECTRONICS

LIBRARY
(Continued from page 16)

Schober Recital Organ

the text, and practical mathematical analyses
are used to explain operation and design
detail.
Published by TAB Books, Blute Ridge Summit, PA 17214. Hard corer. 352 pages. $14.95.

"1850!

*Includes
finished walnut
console. (Only
$1446 if you build
your own console.)
Amplifier, speaker
system, optional
accessories extra.

DICTIONARY OF ELECTRONICS
AND NEUCLEONICS
by Hughes, Stephens

&

Brown

Since electronics and neucleonics are in many

cases interrelated, a common dictionary of
definitions is a useful reference book, indeed.
In addition to the dictionary text of some 9000
definitions, this book contains a comprehensive list of abbreviations, acronyms, and symbols. The appendices provide fuller statements of some of the fundamental theories
of the increasingly complex fields of atomic
and nuclear physics, as well as numerous useful and relevant tables of data on a wide
range of topics.
Published by Barn, & Noble, Inc., 105 Fifth
Ave., New York, NY 10003. Hurd cover. 443
Pages. $14.50.
.e

TECHNICAL CALCULUS
by H.R. Stillwell

&

D.H. Price

Written to meet the calculus requirements

of students of engineering technology in technical institutes, junior colleges, etc, this book
requires a working knowledge of trigonometry, college algebra, and logarithms. However, for the reader who may have been
away from these subjects for some time, there
is a brief review. The text material is elementary, with the subject matter grouped
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textbook, but no answer key is provided for
the review questions.
Published by Holt, Rinehart and Winston,
Inc., 383 Madi.sou Are., New York, NY 10017.
Soft cover. 251 pages. $3.95.
ACTIVE NETWORK THEORY
by S.S. Haykin

This book presents, in a unified manner, the

fundamentals of active network theory so

that the student can understand fully the

circuit properties of semiconductor devices

and vacuum tubes and be able to deal effectively with circuit devices yet to come. Written
at a level suitable for use by senior undergraduate and graduate electrical engineering
students, physical explanation and meaningful examples have been included to elucidate
the results obtained. Each chapter ends with
a list of problems and references.
PltWished by Addison -Wesley Publishing Co.,
Inc., Reading, MA 01867. Hord corer. 556
pages. $16.50.

couldn't touch an organ like this in a store for

less than $4,000 -and there never has been an electronic instrument with this vast variety of genuine
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any time you like! If you've dreamed of the sound
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You can learn to play it -and a full -size, full- facility instrument is easier to learn on than any cut -down
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slightest knowledge of electronics or music, for design and parts quality from the ground up, and
above all -for the highest praise from musicians
You

everywhere.

Send right now for the full -color Schober catalog,

containing specifications of all five Schober Organ
models, beginning at $499.50. No charge, no obligation. If you like music, you owe yourself a Schober

Organ!

The
YCh(t2eiOrgan Corp., Dept. PE -35
43 West 61st Street, New York, N.Y. 10023
Please send me Schober Organ Catalog and

free 7 -inch "sample" record.

Enclosed please find $1.00 for 12 -inch L.P.
record of Schober Organ music.

NAME
ADDRESS

CITY

STATE

ZIP

CIRCLE NO. 23 ON READER SERVICE PAGE

i'N`,ToELECTRONICS

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October, 1970

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ELECTRONICS MARKET PLACE

COMMERCIAL RATE: For firms or individuals offering commercial
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FOR SALE

SLOW FLASHING TURNLIGHTS ARE DANGEROUS. WINKER -KIT

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FREE! Giant bargain catalog on transistors, diodes, rectifiers, SCR's,

zeners, parts. Poly Paks, P.O. Box 942, Lynnfield, Mass. 09140.

GOVERNMENT Surplus Receivers, Transmitters, Snooperscopes, Radios, Parts, Picture Catalog 250. Meshna, Nahant, Mass. 01908.

for miniature transmitter tests. New illustrated

catalog. 250. Single and multistage kits, cones, engines, launchers,
trackers, rocket aerial cameras, technical information. Fast service.
Estes Industries, Dept. 18 -K, Penrose, Colorado 81240.
LOWEST Prices Electronic Parts. Confidential Catalog Free. KNAPP,
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EUROPEAN and Japanese bargains catalogs. $1 each. Dee, 10639E
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WE SELL CONSTRUCTION PLANS. TELEPHONE: Answering Machine,

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WEBBER LAB's. Police & Fire Converters. Catalog 250. 72 Cottage
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INVESTIGATORS, LATEST ELECTRONICS AIDS. FREE LITERATURE.
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ELECTRONIC PARTS, semiconductors, kits. FREE FLYER. Large catalog $1.00 deposit. BIGELOW ELECTRONICS, Bluffton, Ohio 45817.
RADIO -T.V. Tubes -330 each. Send for free catalog. Cornell, 4213
University, San Diego, Calif. 92105.
ULTRA -SENSITIVE AND POWERFUL METAL DETECTORS -join the
many who are finding buried coins, minerals, relics and artifacts.
Don't buy till you see our FREE catalog of new models. Write Jetco,
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LASER parts catalog 600. Moynihan, 107 North
City, New Jersey 08401.

Brighton, Atlantic

PSYCHEDELIC catalog. Posters, lighting, etc. Send 500 for handling

to Hole In The Wall, 6055PE Lankershim, North Hollywood, Calif.

91606.
THE ART OF DE- BUGGING- $5.95. TRON -X PUBLICATIONS,
BOX 38155, HOLLYWOOD, CALIFORNIA 90038.

P.O.

$2.00. Listening Devices

$1.00. Tail Transmitter
two F.M. Mike Transmitters
$1.00.
Sound Telescope . . . $2.00. Infinity Transmitter
. $2.00.
Equipment and kits available. Howard, 20174 Ward, Detroit, Michigan 48235.
CONSTRUCTION

PLANS: LASER

...

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CLEARANCE SALE rectifiers, transistors, 1000's other items. Catalog

150. General Sales Company, 254 Main, Clute, Texas 77531.

10016.

B &K TEST EQUIPMENT UNBELIEVABLE PRICES. FREE

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STREET, BRONX, N.Y. 10451.

SENCORE,

AMATEUR SCIENTISTS, Electronics Hobbyists, Experimenters, Students .

.
Construction Plans-all complete, including drawings.
schematics, parts lists with prices and sources
. Radar-Build
your own ultrasonic doppler radar. Detect motion of people, automobiles, even falling rain drops. Transistorized, uses 9 volt transistor
battery -$4.50.
.
Long -Range "Sound Telescope" -This amazing
device can enable you to hear conversations, birds and animals, other
sounds hundreds of feet away. Very directional. Transistorized. Uses

battery- $3.70.
.
Robot Man -Moves hands and arms -$3.50
Or send 250 coin (no stamps) for complete catalog. Other items
include Psychedelic strobes, light shows, lasers
.
46 different
projects. Technical Writers Group, Box 5994, State College Station,
Raleigh, N.C. 27607.
9V

MECHANICAL, ELECTRONIC devices catalog 100. Greatest Values

Lowest Prices. Fertik's, 5249 "D ", Philadelphia, Pa. 19120.

MUSIC LOVERS, CONTINUOUS, UNINTERRUPTED BACKGROUND

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SPACE -AGE TV CAMERA KIT!

Education. Solid-state.

Only

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$116.95! Star er kits: $18.95 up.

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Plans 250

CONVERT any television to sensitive, big -scr en oscilloscope. Only

minor changes required. No electronic expert nce necessary. Illustrated plans, $2.00. Relco -A33, Box 10563, Houston, Texas 77018.

BURGLAR ALARM SYSTEMS and accessories. dontrois, bells, sirens,

hardware, etc. OMNI -GUARD radar intruder detection system, kit
form or assembled. Write for free catalog. Microtech Associates,
Inc., Box 10147, St. Petersburg, Florida 33733.

PRINTED CIRCUITS. Magazine projects and experimental.

listing. Vico, Box 1590, Los Angeles, Calif. 0053.

Free

ELENCO LR -6 Bi- Lateral linear amplifier 150 watts output, variable

receive boost, $149.95. (Illegal for Class D CB use.) Elenco, Dept.
A, Wabash, Ind. 46992.

ELECTRONIC COMPONENTS- Distributor prices,

El Cajon, California 92021.

Free catalog.

Box

2581,

PRINTED CIRCUITS for projects, Popular Electronics or others.

Send page or black -white drawing of circuit pattern, 250 square
inch. Min $1.75 board. Send remittance: Gereral Printed Circuits,
Box 4013, Downey, California 90241.

CIRCUIT BOARDS: Complete Job Shop Operation. Jetca, Inc., Box

418, Monon, Indiana 47959.

ANTIGRAVITY, EXPERIMENT AND THEORY; rushed -$1.00. U.S.

Inquiries. Intertech -7A2, Box 5373, Station -F, Ottawa, Canada.
Ham's, CB'ers-Rotary QSL File
Lowell, Chicago, Illinois 60639.

SWL'S,

CB -8.

MB Sales,

1917

RADIO CHASSIS'S NEW. Postpaid with SCHEMATIC. AM /FM 10

TRANSISTOR $5.20 each. AM 6 Transistor $2.65 each. Information
150. Union Supply; Box 32; Niles, Illinois 60648.

SEMICONDUCTORS and parts catalogue free over 100 pages. J. & J.

Electronics, Box 1437, Winnipeg, Manitoba, Canada. U.S. Trade

50 NEW PRECISION RESISTORS I/aw- 1w 1% and better with 50

NEW MICA CAPACITORS. Tremendous assortment of values. $3.95.
General Instrumentation Services, Box 34721, Los Angeles, Cali-

directed.

fornia 90034.

118

POPULAR

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STROBES, Xenon, save over 50 %. $14.95 assembled! Guaranteed.

Plans, $1.00. Box 233P, Mablevale, AR 72103.

STROBES, color organs, the incredible Strobit. Electric Candles,

Remote Switch, Touch Switch. All in KIT and ASSEMBLED forms.
Send 250 for complete catalog. Teletronics, Box 1266, South Lake
Tahoe, California 95705.

CHEMICAL FORMULAS and preparation instructions when possible.

Send self- addressed stamped envelope and $3.50 to Chemtronics,
Box 1266, South Lake Tahoe, California 95705.
DIRECTORY. Electronics, all merchandise.
World trade information. $1.00 today. 'piano Kaisha Ltd., Box
F266. Spokane, Washington 99207.
JAPAN & HONG KONG

XENON STROBE TUBE. Peak light output approximately 25,000,000.

New $17.95 postpaid. Free Literature. R.W. Electronics, 4005 West
Belmont Avenue, Chicago, Illinois 60641.
COMP -U -KIT, Computer micro -circuits

and a book which tells all

about computer logic. Unique modules and kits, fascinating booklets. Write for free illustrated literature. Scientific Measurements,
C143, 9701 Kenton, Skokie, Illinois 60076.
SECRETLY transmit voice or music one mile on invisible infrared
light beam. Solid state, optoelectronic communications day or night.

License not required. Construction straightforward. Details, 300.

Comprehensive manual, $6.00. Lundart, University Station 4008 -E3,
Tucson, Arizona 85717.
CIGARETTE papers flash to music. Psychedelic Electronics Handbook,
$9.95. Box 46156 Seattle, Wash. 98146.
ROUTER Bits, r/4" shank, hi- speed, used, excellent condition, $2.50
dozen postpaid. Lillian's, Box 17165PE, Chicago, Illinois 60617.

PLANS AND PC BOARD FOR 3 CHAN ACTIVE FILTER COLOR ORGAN

-$3, ALSO FOR METAL LOCATOR-$2.50, SCA FILTER -$2.50.
DYMAX CO., P.O. BOX 1023, SCOTTSDALE, ARIZ. 85252.
B URGLAR and FIRE ALARM SYSTEMS and supplies. INSTALLATION

FIBRE OP -KITS, using the "magical optical fibers" that transmit

light energy. FREE CATALOG. Scientific Devices, 211E Albion,
Wakefield, Mass. 01880.
beat frequency type-$3.25. New, operational amplifier discriminator type -$6.00. Magneto -Hydro- Dynamics,
Box 114, Plaza Station, Merrick, New York 11566.
METAL DETECTOR Plans,

BUILD amazing new device. Automatically indicates when oil in your

auto's crankcase becomes 1 quart low. Inexpensive, easy to build.
12 volt neg. gnd. Plans $3.00. J. R. Boykin, 40 Doncaster, Rome,
Georgia 30161.
SURVEILLANCE DEVICES IN KIT FORM: Telephone Transmitter, FM
Spy Transmitter, Telephone- Recorder Actuator, Tail Transmitter,
Bug Detector. Complete Kits Send $15.00 each. ELECTRONIC
SECURITY SYSTEMS, 1101 West Rosecrans Avenue, Gardena, Cali-

fornia 90247.

for commercial -free FM background music. Connects easily to any FM tuner. 6- transistor circuit uses standard components. Plans and 3 x 4r/2" etched circuit board $4.50. Component
kits also available. Wallace Enterprise, Inc., 83 -15 98th Street,

SCA music adapter

Woodhaven, N.Y. 11421.

CIRCUIT KITS:
COMPUTER, OPTOELECTRONICS,
AUDIO. Catalog free. KAYE ENGINEERING, Box 3932 -A, Long Beach,
INTEGRATED

Calif. 90803.
TESLA COIL -40" SPARKS! Plans $5.00. Information 500. Huntington Electronics, Box 9 -P, Huntington, Conn. 06484.

TUBES
"Oldies ", latest. Lists free. Steinmetz, 7519 Maplewood,

MANUAL and catalog $1.00. Refunded first order. Electronic Sentry

Systems, P.O. Box 8023A, Sacramento, California 95818.

TUBES

67KC SCA Adapter, manufacturer's closeout on this model. The

missing link between FM tuner and audio amplifier if you want
commercial free music. Solid state demodulator board wired and
tested. Operates on 9 to 30 volts. Variable gain input and adjustable
mute. Easily switched in and out. Packed with instructions and station
lists. All orders shipped postpaid same date as received, anywhere
USA $16.50 each. Marvin Industries, Box 551, Hudson, Ohio 44236.

RECEIVING

PLANS -PARTS -KITS A wide range of the unusual for the experimenter,
hobbyist and amateur scientist. Many psychedelic items; STROBES,
color organs. ELECTRIC CANDLES, Touch Switches, LIGHTNING
GENERATORS. Complete line of COMPONENTS. Air Mail Catalog 500.
Teletronics, Box 1266, South Lake Tahoe, Calif. 95705.
-

TINY LIGHT to cheer you, blinks for years. Five dollars postpaid.
F.

Ramsey, 1402 N. Fresno, Fresno, California 93703.

CAPACITORS 140 mfd 450 WVDC Electrolytics Brand New, Ten for
$9.50. Mehaffey, 6835 Sunnybrook Lane, NE, Atlanta, Ga. 30328.

listing relays, steppers, & other electronics parts

for experimenters. Send name, address and a dime to: Gust & Company, Box 24081, Edina, Minnesota 55424.
B ARGAIN sheets

REPAIRS -Complete Course Details, 12 Repair Tricks,

Many Plans, Two Lessons, all for $1. Refundable. Frank Bocek,
Box 833, Redding, Calif. 96001.

TV TUNER

ELECTRONIC devices. Catalog 250.

Franklin, Worcester, Mass. 01604.

Taurus

Engineering,

706

quality, five input model, with master

control, $58.20 net postpaid. Other models available. Send 100
specification
sheet.
for catalogAJC Electronics, 2801 Sandy Lane,
Fort Worth, Texas 76112.
MIXER,

Hammond, Indiana 46324.

& INDUSTRIAL TUBES, TRANSISTORS. All Brands

Biggest Discounts. Technicians, Hobbyists, Experimenters- Request
FREE Giant Catalog and SAVE! ZALYTRON, 469 Jericho Turnpike,
Mineola, N.Y. 11501.

Send 10c for Catalog (tubes, electronic equipment) Barry, 512 Broadway, N.Y.C. 10012.
TUBE Headquarters of World!

thousands of types of electronic parts, tubes,

transistors, instruments, etc. Send for Free Catalog. Arcturus Electronics Corp., MPE, 502 -22nd St., Union City, N.J. 07087.
THOUSANDS and

-33f

each. Send for free

RADIO & T.V. Tubes
University, San Diego, Calif. 92105.

list. Cornell, 4213

TUBES -Lowest

Obsolete, receiving,
prices. Foreign- American.
special purpose, transmitting tubes. Send for tube, parts catalog.
Ferry
Newark,
Radio
Company,
56
-P
St.,
N.J. 07105.
United

TAPE AND RECORDERS

BEFORE Renting Stereo Tapes try us. Postpaid both ways -no deposit

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-prevail here. If you've been dissatisfied in the past, your initial
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20,30% and more, postpaid anywhere U.S.A.

discount batteries, recorders, tape /cassettes, 80 -page catalog
250. SAXITONE TAPES, 1776 Columbia Road, N.W., Washington,
D.C. 20009.
STEREO TAPES, save
We

CITIZEN BAND Radios, SSB, AM, Accessories, Free Catalogue.

Dealers send letterhead for factory prices. Call 714-846-3101.
C.B.E.D., 6624 Westminister Avenue, Westminister, Calif. 92683.
IC

"ONE TUBE DXER" Handbook-50f. 15 Distance one tube plans

250. Catalog. Laboratories, 2612 -L Butano, Sacramento, Calif.
95821.

Professional

TELEPHONE Recorder Switch, Diagram, Parts list, $5.00., TECH

CONSULTANTS, P.O. Box 02231, Cleveland, Ohio 44102.

OLD radio programs on tape. 6 hours for $8.00. Catalog

Maris, 1926 Cherokee, Norman, Okla. 73069.
TAPE -blank,
TAPE
RECORDERS,
Tower, Lafayette Hill, Pa. 19444.

pre -recorded.

50f.

Catalog

Don

25f.

OLD RADIO PROGRAMS on tape. Hundreds available. 2 -hr. sample

$6.00, 4 -hr. $9.00. Hobby Catalog for collectors of radio tapes, old

comics, movie serials, nostalgic items, only $1.25 or free with sample tape. NOSTALGIA, 9875 SW 212 St., Miami, Fla. 33157.

PLANS AND KITS

CIRCUITS for 32 electronic projects, R.F., audio and gadgetry complete plans $1.00. P.M. Electronics, Inc., Box 46204, Seattle,
Wash. 98146. Dealer inquiries invited.

CASSETTES-Cash in on a tremendous All -year round market.

Send for lowest pricing and details. Include $1.00 for 2 cassette
samples. DICTATION PRODUCTS, PO Box 87 DPM, Hallandale,

Florida 33009.

October, 1970

119

www.americanradiohistory.com

REPAIRS AND SERVICES

code from tireless teacher. Wilkinson programmed course

and LP player stays with beginners to license speed. $9.45 postpaid.
Florida residents $9.83. Details free. Wilkinson Laboratories, Box

Tuners rebuilt and aligned per manufacturers specification.

Only $9.50. Any make UHF or VHF Ninety day written guarantee.
Ship complete with tubes or write for free mailing kit and dealer brochure. JW Electronics, Box 51C, Bloomington, Indiana 47401.

14196, Gainesville, Fla. 32601.

DRAFTING (Electronic, Mechanical, Architectural). Home courses
$5.00. Send $3.00 first lesson. Prior Inc., 23 -09 169 Street,
Whitestone, New York 11357.

TELEVISION tuners, any make VHF or UHF, cleaned, repaired and

realigned per manufacturer's specifications $9.50. One year guarantee. Quality Tuner Repair, 526 West Busby Street, Lebanon, Indiana

HIGH FIDELITY

LEARN

TV

46052.
SPEAKER RECONING, replacement grill cloth, vinyl covering, hardware. For price list send self -addressed, stamped envelope: Creative

FREE! Send for money saving stereo cataldg

P1OE, lowest quotations on your individual component, tape recorder, or system requirements. Electronic Values, Inc., 200 W. 20th St, New York,

Sound Products, 262B Cranz Place, Akron, Ohio 44310.

N.Y. 10011.

ELECTRONIC

Assembling. Receive, assemble and return. Small

to medium size devices wanted. Satisfaction guaranteed. Electronics,
Box 384, Everett, Wash. 98201.

LOW, Low quotes: all

PERSONALS

HI -Fl components. Tape Recorders, at guaranteed "We Will Not Be

Undersold" prices. 15 -day money -back gUarantee. Two -year warranty. No Catalog. Quotations Free. Hi- Fidelity Center, 239 (P) East
149th Street, New York 10451.

MAKE FRIENDS WORLDWIDE through international correspondence.

Illustrated brochure free. Hermes, Berlin 11, Germany.
INVESTIGATORS, LATEST ELECTRONIC AIDS. FREE LITERATURE.
CLIFTON, 11500 -K NW 7th AVE., MIAMI, FLORIDA 33168.

INSTRUCTION
all makes including
transistor. Experimental kit-trouble- shooting. Accredited NHSC,
Free Booklet. NILES BRYANT SCHOOL, 3631 Stockton, Dept. A,
Sacramento, Calif. 95820.
LEARN ELECTRONIC ORGAN SERVICING at home

FCC First Class License in six weeks -approved

components and

recorders,

HiFi, Roslyn,

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Hi -Fi, components, Sleep Learning Equipment,

tapes. Unusual Values. Free Catalog. Dressner, 1523R, Jericho
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DIAMOND NEEDLES AND STEREO CARTRIDGES at low, low prices
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TAPE RECORDERS,

BSR record changers; $13. McDonald 300-$18; 400 -$20;

500 -$25. AM /FM component system -$50. Davis, Dept. 2737 Third
Ave., Bronx, New York 10451.
New

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WANTED

Write Elkins Institute, 2603B Inwood Road, Dallas, Texas 75235.

R.E.I.'s famous (5) week course for the First Class Radio Telephone
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Florida 33577 -or 3123 Gillham Road, Kansas City, Missouri 64109
-or 809 Caroline Street, Fredericksburg. Virginia 22401 -or 625
E. Colorado Street, Glendale, California 91205.

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suggestion, Box 24-ID, Olympia, Washington 98501.
LEARN

QUICKSILVER, Platinum, Silver, Gold, Ores Analyzed. Free Circular.

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SCREW Base electrolytic capacitors. Must have solder lug terminals,
ratings. No leakers. Henry Schwartzman, 73 Bridge Street, Corning,
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free. Auto-

DEGREE in Electronics Engineering earned mostly by correspondence. Free brochure. Dept. G -9, Grantham School of Engineering,
1505 N. Western Ave., Hollywood, California 90027.

PLAY ORGAN EASILY! AMAZING METHOD! FREE

KEGLEY, 1016-PE KELLY, JOLIET, ILLINOIS 60435.

CASH PAID! Unused tubes, electronic equipment. Barry, 512 Broadway, NYC 10012.

INFORMATION.

HIGHLY effective home study courses in Electronics Engineering

Technology and Electronics Engineering Mathematics. Earn your
Degree. Write for Free Descriptive Literature. Cook's Institute of
Electronics Engineering, (Dept. 15), P.O. Box 10634, Jackson,
Miss. 39209. (Established 1945).

F.C.C. FIRST CLASS LICENSE in three to four weeks. Write American

Institute of Radio, 2622 Old Lebanon Road, Nashville, Tennessee
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AMATEUR RADIO.
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vice. 2420 -P 77th, Oakland, Calif. 94605.

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ents.

MEMORIZE: "1970 TESTS -ANSWERS" for FCC FIRST AND SECOND CLASS LICENSE. Plus "Self -Study Ability Test." PROVEN.
$5.00. Command, Box 26348 -P, San Francisco 94126.
College degree at home. Many subjects. FLORIDA STATE
CHRISTIAN COLLEGE, Post Office Box 1674, Fort Lauderdale,
Florida 33309.
EARN

LEAP! LEAP! LEAP! Into BIG Money; 150,000 Computer Programmers needed in 5 years. Diploma Home Study Course, Price
Breakthrough: only $9.95. Act Now. Money Back Guarantee. U.S.
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120

including copies of related United States PatInventors, attorneys, manufacturers use our "World- Wide"
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"Tips on Safeguarding Your Invention." Write:

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FREE PAMPHLET:

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GOVERNMENT Surplus How and Where to Buy in Your Area. Send
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FOPULAR ELECTRONICS

..

.
Trucks From $78.40... Boats,
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Electronics Equipment. Wide Variety, Condition. 100,000 Bid Bargains Direct From Government Nationwide Complete Sales Directory and Surplus Catalog $1.00. (Deductible First $10.00 Order).
Surplus Service, Box 820 -1, Holland. Michigan 49423.

JEEPS Typically From $53.90

HYPNOTIZE PERFECT STRANGERS- EITHER SEX -SUCCESSFULLY!

Secret Methods -they never know! Illustrated Course and 10 inch
Hypnodisk $2.00. RESULTS ABSOLUTELY GUARANTEED! Dr. H.
Arthur Fowler, Box 4399, Woodbury, New Jersey 08096.

MAGAZINES

80% or more on all types of electronic equipment. Buy

direct from Govt. surplus. How to receive their catalogues. Send
$2.00. Bridgeworth, P.O. Box 2292 -M, Vancouver, Washington
98661.
INDUSTRIAL and Government Electronic Surplus. Latest list free.
Startroniu, Box 17127, Portland, Oregon 97217.
SAVE up to

JAPAN PUBLICATIONS GUIDE Business, pleasure, education. $5.00.

INTERCONTINENTAL, CPO 1717, Tokyo 100 -91.
OVER 2,000,000 backdate magazines!
917 -PE, Maywood, New Jersey 07607.

Specify needs. Midtown, Box

MAGNETS

SHORTWAVE LISTENING

MAGNETISM (1C0) page script newly discovered magnetic principles

($3.00). Jesse Costa, Box 26, Waquoit, Mass. 02536.

NEW 2nd EDITION OF POPULAR BOOK "Better Shortwave Reception"

covers eavesdropping 10 Khz -UHF; get best receiver buy; when/
where listen; outer space "signals "; astronaut circuits; police, etc.
156 pages, $3.95. At leading dealers, or direct from publisher
(please add 200 for handling). Radio Publications, Inc., Box 149M,

PHOTOGRAPHY-FILM,
EQUIPMENT, SERVICES

Wilton, Conn. 06897.

SCIENCE Bargains Request Free Giant Catalog "C.1" -148 pages

Astronomical Telescopes, Microscopes, Lenses, Binoculars, Kits,
Parts. War surplus bargains. Edmund Scientific Co., 300 Edscorp

BOOKS

Bldg., Barrington, New Jersey 08007.

catalog aviation /electronic /space books. Aero Publishers,

329PE Aviation Road, Fallbrook, California 92028.
"UNSSUAL" Books! Catalog Free! International, Box 7798 (PE),
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FREE book prophet Elijah coming before Christ. Wonderful bible
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RECORDS
POPULAR organ albums factory direct. Concert Recording, Lynwood,

Calif. 90262.
SPECIAL interest records available, produced by the editors of the
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INFORMATION. Amazing Book. Swimsuits, jewelry. Write: LYN, Box

1573, Waco, Texas 76710.

HYPNOTISM
FREE Hypnotism, Self- Hypnosis, Sleep
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PRINTING

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QUALITY Printing-Both
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1222

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Please refer to heading on first page of this section for complete data concerning terms, frequency discounts.
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SPACEOPHOBIA? Romania nudes plus 50

approvals, BKJ, Astor, Boston, Mass. 02123.

EXCITING OVERSEAS JOBS. Directory $1.00.

Box 942 -E, Belmont, California 94002.

Research Associates,

"HOW to get jobs overseas " -Worldwide Lists Hiring Organizations

-143 pages inside information -$2.98. Refundable. Staydrype,
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BUSINESS OPPORTUNITIES
I MADE $40.000.00 Year by Mailorder! Helped others make money!
Start with $10.00 -Free Proof. Torrey, Box 318 -N, Ypsilanti, Michigan 48197.

FREE BOOK

"999 Successful Little Known Businesses" Work home,

Plymouth 445 -M, Brooklyn,

N.Y. 11216.

$200.00 DAILY In Your Mailbox! Your opportunity to do what mail order experts do. Free details. Associates, Box 136 -J, Holland,
Michigan 49423.
MAKE BIG MONEY raising chinchillas, rabbits, guinea pigs for us.
Catalog-25e. Keeney Brothers, New Freedom, Pa. 17349.

CITIZEN BAND DEALER.

Brockton, Massachusetts 02403.
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pictures hundreds of farms, ranches, town and country homes, businesses coast to coast! Specify type property and location preferred.
Zip Code, please. UNITED FARM AGENCY, 612 -EP West 47th St.,
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MUSICAL INSTRUMENTS
30% DISCOUNT any name brand musical instrument. Free catalog.
Freeport Music, 127 -N Sunrise Highway, Freeport, N.Y. 11520.

RUBBER STAMPS
RUBBER address stamps $2.00, Signature $3.50.
Jackson's, Box 443G, Franklin Park, Illinois 60131.

Free

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MISCELLANEOUS

Communications,

$25 to $75 spare time! Take orders for double air

cushion Bronson Shoes. Men's, women's line for dress, work, play.
Highest commissions. Shoes for yourself. Outfit FREE. Bronson,
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MAKE extra

PIANO TUNING learned quickly at home. Tremendous field! Musical

knowledge unnecessary. GI Approved. Information Free. Empire
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MAILORDER! Make big money working home. Free report reveals

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SPARE TIME CASH -Sell

advertising Book Matches -every business

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repeat business. Power house selling kit with new complete catalog
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WINEMAKERS: Free illustrated catalog of yeasts, equipment. Semplex, Box 12276, Minneapolis, Minn. 55412.

DRIVER'S License, Birth Certificate, H.S. & College Diploma,

Marriage & Divorce Certificates-Blank Forms. Fill them in yourself.
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ABOUT YOUR
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air conditioning, refrigeration. Tools, supplies, full instructions. Doolin, 2016 Canton, Dallas, Texas 75201.

Household Products. Your trade name -our formulas.

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PRODUCE

BIG EARNINGS selling Hertel Bibles. New 3- dimension cover, finest

reference edition sells fast. Demonstrator furnished. Big commissions. International Book, Dept. PE, Box 118, Wichita, Kansas

67201.

TREASURE FINDERS
GOLD, SILVER, RELICS! Located with powerful Detectron Metal Detectors. Free information. Terms- Detectron, Dept. PE -10, Box 243,
San Gabriel, California 91778.
FREE TREASURE GUIDE! Fact -filled

collectors edition; send 500 for

postage. Also request free literature on ultrasensitive, professional

Fisher Detectors. FISHER RESEARCH, Dept. PE -10, Palo Alto, Cali-

fornia 94303.
locates buried gold. silver, coins, treasures.
powerful models. $19.95 up. Free catalog. Relco -A33, Box 10839,
Houston, Texas 77018.
TREASURE FINDER
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122

POPULAR ELECTRONICS

10010's OF UNUSUAL SCIENTIFIC BARGAINS

Lt`

POPULAR ELECTRONICS

SPECIAL UNIQUE

LIGHTING

f, ..,41c11dElC.

7tfaf.P

"

cccc4Cdvq...

CHROMATiIC "MACHINE -GUN" STROBE

OCTOBER 1970

Blue & While light

yeballs every 6 secthis low-cost mechanical
that can run continuously
without fear of burning Op. Devastating effects over 500 ft. sq. area.
Created by
color wh
wheell in
front of 100W. 120v reflector flood-

ited, Green.
barrage the

onds

with

strobe

ADVERTISERS INDEX

lamp (Incl.)- elements seem to flash

on & off as colors fluctuate. Turns

stare windows, posters, parties Into

flashing.
productions.
pulsating

READER
SERVICE NO.

PAGE NO.

ADVERTISER
Allied Radio Shack

110

Avanti Research & Development

C/P Corp.

Stock No. 71.171AV

105

Argos Products Co.

Co., Inc.

Convection cooled. Walnut cabinet.

Brass handle. Reg. house current.
(9x1Ox6s /4 ")
$28.50 Ppd.

LIGHTING HANDBOOK
100
information packed pages!
Fully espial. latest in psychedelic

PSYCHEDELIC

lighting

technigses,
equipment.
developments. Covers all facets of
psychedelic light -show Production
including strobes, black lights,

14

II

mirrors

CREI, Heine Study Div.,

McGraw -Hili Book Co.

62. 63. 64, 65

Cleveland Institute of Electronics

88. 89. 90, 91

re,

color taorganfi

light

to "psychedelizet'i
musical groups, shows or

etc. Shows
borties,

ow

"electric trips" for

to set up

private

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gatherings.

looseleaf paper for

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it

$3.00 Ppd.

Stock No. 910OAV

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112

Datak Corp.

110

Drake Company. R.L

116

to Identify minerals, fanal, bac Aferla -check for surface flaws,

Communications Div., DYNASCAN CORP.

114

playsgwith fluorescent paper, palots.

h Ik, crayons, trace powder, Incl.

Electronics

THIRD COVER

LONG -WAVE BLACKLIGHT FIXTURE

Extremely versatile, compactly de-

'"

signed,

long

'lromxl

black

ture. Has

umer

(3200 -4000 ang-

light (ultraviolet) fix 110 -V lamp with

-watt

Aolvteer-

letrlmvoa

rahUe
for

10

odn,nt

II

Edmund Scientific Co.

12

EICO Electronic Instrument Co.. Inc.

123

Electro- Voice, Inc.

4
13

14

FOURTH COVER

Grantham School of Engineering

Heath Company

66. 107, 108,

Johnson Company, E.F

Kedman Company

16

Lafayette Radio Electronics

29

Midland International

18

Mosley Electronics

11r

vC

National Technical Schools

...36,

New Jersey Semi- Conductors

30

Olson

19

Progressive "Edu- Kits." Inc.

20

RCA Electronic Components & Devices

included.

Stock

ferrilic Buy! Top Quality! Projects

LriMani, slmre L3/ ft. sq. image
from 8' using up to 5 "X5" color,
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Ira logs, coins, maps, etc. Revolutionary peanut -size quartz Halogen
1:m111 (:,0 hr. life), 200mm a a tigttle lens (f3.5. 8" F.L.), unique
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inal

37, 38, 39

124

tkonn

Stock No.

Regency Electronics.

Sams & Co., Inc.. Howard W.

23

Schober Organ Corp.

117

24

Sonar Radio Corp.

113

25

Southwest Technical Products

Surplus Savings Center

III

Stock No.
Stock No.
Stock No.
Order

117

EDMUND SCIENT

26

Sydmur Electronics

103

55

Turner Microphone Co., The

U.S. Army
United Audio Products

10

University Sound
Valparaiso Technical Institute
Xcelite. Inc.

17

16

23

71,O66 V
V
71,O63 V

85,1!0t
by

Ft

CO.

300

WRITE FOR GIANT FREE CATALOG

117

EDMUND
SCIENTIFIC CO.
Ostie

.l

15005

CIRCLE
October, 1970

$89.75 Ppd.

$17.50 Ppd.
18" Diam.I
M.O.- Money-Back Guarantee
EDSCORP BLOC, BARRINGTON, N.J.08007

102

ft. cord.

Stmt No. -Check or

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CLASSIFIED ADVERTISING 118. 119, 120, 121, 122

tt

Yesteryear's ballrooms echo in

mirrored lights that ricisochet to
the beat of today's dis_otheque.
Up to 1,000 lustrous. clear,
handmade glass mirrors on each
ball create fantastic lighting effects. Motorized-they cast reflections that blow the mind!
Ideal for light shows, displays,
restaurants. hotels, and modern
atores.
$30.00 Ppd.
(12" Giant.)
$75.00 FOB
116" Dlam.)

26

22

28

tire field focus.

brightness.
the used upside down. Turbo-

rooted.
111/4 Ibs)

MIRRORED EA.LS BOUNCE LIGHT

21

32

(wt:

71,27AV

18, 19, 20, 21

Inc.

Ppd.

1st QUALITY OPAQUE UNDER $200

2, 3

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$19.50 Ppd.

No. 70,0 ;0AV

104

Electronics

RCA Institutes, Inc.

27

'._

114

17

comer.

a thrilling spark display as you

set off a miniature bolt of lighting
Sturdily made -stands 14" high. Two
5" plastic discs rotate in apposite
directions. Metal collector brushes
hick up the static electricity. store
it in the Leyden jar type condenser
until discharged by the Jumpag
ark. 24 page illustrated booklet

25

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See

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11 ON READER SERVICE PAGE

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www.americanradiohistory.com

123

BUILD 20 RADIO

and Electronics Circuits

PROGRESSIVE "& -kiI"
HOME RADIO COURSE
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CODE OSCILLATOR

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SCHOOL INQUIRIES INVITED

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ou begin by examining the
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-all

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FROM

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will receive all parts and instructions necessary to build twenty different radio and
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N.
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Broadway,
Dept.
6870
Progressive "Edu- Kits" Inc.. 1189

-UNCONDITIONAL MONEY -BACK GUARANTEE

ud

- - - --1

Please rush my Progressive Radio "Edu -Kit" to me, as indicated below:

Check one box to indicate choice of model

Deluxe Model $31.95.

New Expanded Model $34.95 (Same as Deluxe Model plus Television Servicing
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Chock one box to indicate manner of payment
I enclose full payment. Ship "Edu -Kit" post paid.
I enclose $5 deposit. Ship "Edu -Kit" C.O.D. for balance plus postage.
Send me FREE additional information describing "Edu- Kit."
Name

Address

PROGRESSIVE "EDU- KITS" INC.

1189 Broadway, Dept. 687D, Hewlett, N. Y. 11557

124

MMUS
1

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"

You

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TOOLS

SOLDERING IRON
ELECTRONICS TESTER
PLIERS- CUTT'.ERS
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TESTER INSTRUCTIONS MANUAL
GUIDE
TELEVISIONI1100K
RADIO
TROUBLE-SHOOTING BOOK
MEMBERSHIP
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C
AMATEUR LICENSE TRAINING
PRINTED CIRCUITRY

The "Edu -Kit" otters you an outstanding PRACTICAL HOME RADIO COURSE at a
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In a professional manner; how to service radios. You will work theto standard type
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and practice code, using the Progressive Code Oscillator. You will learn and practice

THE KIT

Pat. Off.

Radio Necessary
Parts or Tools Needed

No
No

12 RECEIVERS
3 TRANSMITTERS
SQ. WAVE GENERATOR
SIGNAL TRACER

Reg. U.S.

PRINTEC
At

CIRCUITRY

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
new technique of radio construction is now
becoming popular in commercial radio and
TV sets.
A Printed Circuit is a special insulated
chassis on which has been deposited a conducting material Which takes the place of
wiring. The various parts are merely plugged
in and soldered to terminals.
Printed Circuitry is the basis of modern
Automation Electronics. A knowledge of this
subject is a necessity today for anyone interested In Electronics.
now

no

increase in

CIRCLE NO. 19 ON READER SERVICE PAGE

Punted in U.S.A.
CIRCLE NO. 16 ON READER SERVICE

PAGE-*

NEW! CB Scanner

monitors all channels visually

.z

VISUAL

a _

MONITOR

Watch thc live ones flash on!

FIRST ONE ANYWHERE! Patented new
Commander Scanalyzer 23 lets you monitor
all 23 CB channels at a glance -continuously
and simultaneously.
It not only tells you where the activity is,
but offers an exclusive sensitivity control so
you can determine the signal strength of any
particular channel or the relative signal
strength of all channels at once.
In addition, the 'Scanalyzer 23' has a
memory control which lets you know what's
been going on if you leave the unit.

manderDivision

This yoJ've got to have! Solid state, self contained and ready for operation. You need
no special tools or wiring for installation.
Just use your present equipment and the
Scanalyzer! It's the most spectacular CB
advancement since the synthesizer! Carries
full E.T.A. standard warranty. See your local
authorized Commander distributor or
Model 779...$149.95
Also available
REACT Model 780..
gives AUDIO alarm when channel 9 is active
... only $174.95.
ORDER BY MAIL.

...

of Trippe Electronics

133 N. Jefferson, Dept. P,Chicago, Illinois 60606

Please rush my new

SCANALYZER 23...

enclosed is check
or money order for

$149 95.
Please rush my new
REACT Model 780.
Enclosed is S174.95.

NAME
ADDRESS

CITY

STATE

CIRCLE NO.

Please rush linformation

3 ON

READER SERVICE PAGE

Zip

7 arguments in favor

of building your own speaker

system from scratch.
The easiest way to buy high fidelity speakers
may not always be the best. Because a complete pre -packaged system may be far from
what you need. Consider some of the advantages of separate component loudspeakers:
1. You choose from an almost infinite variety
of sizes and levels of performance. Your system will exactly reflect your specific listening
preferences.
2. You save space by building speakers into
walls, ceilings, closet doors, even in floors!
Or use existing cabinets or custom -built enclosures that better suit your decor than any
mass -produced system.
3. You enhance the illusion of "live" music
by hiding or disguising the sound source. You
listen to the music not the speakers.
4. You can up -date your component system
as often as you wish to meet advances in
the state of the art.
5. You save money by paying only for
performance.

6. You end the conflict between fine sound

and handsome decor by making the speaker
system an integral part of the room or the
furniture.
7. You can use the building -block method of
planned improvement as your budget permits. There's no problem of being "stuck"
with a compact that fits today's budget but
can't meet your ultimate listen, g goals.
Take a few minutes to study t} e variety of
Electro -Voice component speaker . 21 models
from $20.00 to $275.00. From su per- tweeters
to giant 30" woofers. Consider h 1w they can
aid in creating a speaker system tl at uniquely
expresses your musical needs. A Id ask your
Electro-Voice high fidelity speci Mist for his
recommendation. Finally, take he time to
listen carefully.
Freedom of choice. It's at the very nub of
high fidelity.
ELECTRO- VOICE, INC., Dept. 1004P,
630 Cecil St., Buchanan, Michigan 49107

Ze1kc

A SUBSIDIARY OF BUTTON INDUSTRIES,

CIRCLE NO. 4 ON READER SERVICE PAGE

INC.