Elementary Electronics 1966 07 08

ELEMENTAR ¡HI-FI

IB'LD

THE

SERfOPNOME SERVER:

ON WHEELS!

ELECTRON/CS

JULY -AUGUST 75c By the Editors of RABIO -T' EXPERIMENTER

BASIC

ELECTRICITY

From the atom to Ohm's law!

I i1

OT -can

S1Aß1ER!-

Uses SCR's

countdown

tdown

Those Fabulous

FUEL CELLS

Electrolysis in reverse!

Electrolysis lin reverse!

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Be creative -and thrifty too!

Save up to 50% with EICO Kits and Wired.

EICO supports your sense of

achievement with no- compromise

engineering, finest parts, dramatic

esthetics, simple step -by -step

instructions and large pictorial

diagrams. You need no technical

background -just pliers, screw-

driver, soldering iron. Three million

TEST EQUIPMENT

people, ages 8 to 89, have built EICO

kits. If you love to create, EICO is

for you. And if you want the best

buys in ready -to -use factory -

assembled equipment, again EICO

is for you. Judge critically for

yourself. Send for your free catalog.

See EICO at your local dealer.

CITIZENS BAND/ HAM RADIO

EICOJ

KITS & WIRED

STEREO/HI-FI

Model 232 Peak -to -Peak VTVM. A must for color

or B &W TV and industrial use. 7-noskip ranges

on all 4 functions. With Uni-Probe., $29.95 kit,

$49.95 wired.

Model 460 Wideband DirecCcopled 5" Oscil-

loscope. DC.4.5mc for color and B &W TV service

and lab use. Push -pull DC vertical amp., bal. or

unbal. input. Automatic sync limiter and amp.

$89.95 kit, $129.50 wired.

Model 324 RF Signal Generator. 150kc to 435mc

range. For IF -RF alignment and signal tracing of

TV, FM, AM. CB end mobile. Built -in and ext.

modulation. $32.95 kit, $44.95 wired.

New Model 779 Sentinel 23 CB Transceiver. 23-

channel frequency synthesizer provides crystal.

controlled transmit and receive on all 23 chan-

nels. No additional crystals to buy ever! Features

include dual conversion, illuminated S RF meter,

adjustable squelch and noise limiter, TVI filter.

117VAC and t2VDC transistorized dual power

supply. Also serves as 3.5 watt P.A. system.

$169.95 wired.

New Model 712 Sentinel 12 Dual Conversion 5-

watt CB Transceiver. Permits 12- channel crystal -

controlled transmit and receive, plus 23-channel

tunable receive. Incorporates adjustable squelch

& noise limiter, & switches for 3.5 watt P.A.

use, spotting, & Part 15 operation. Transistorized

12VDC & 117VAC dual power supply. $99.95

wired only.

e'

New Model 753 The one and only SSB SAM 'CW

Tr i -Band Transceiver Kit. "The best ham trans-

ceiver buy for 1966" -Radio TV Experimenter

Magazine. 200 watts PEP on 80. 40 and 20

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

level dynamic ALC. Unequaled performance, fed.

or^c and appearance. Sensationally priced at

$189.95 kit, $299.95 wired.

New Model 3566 All Solid -State Automatic FM

MPX Stereo Tuner 'Amplifier. "Very satisfactory

product, very attractive price" -Audio Magazine.

No tubes, not even nuvistors. Delivers 112 watts

IHF total to 4 ohms, 75 watts to 8 ohms. Com-

pletely 'pre -wired and pre. aligned RF, IF and

MPX circuitry, plus plug -in transistor sockets.

$219.95 kit (optional walnut cabinet $14.95t,

$325.00 wired including walnut cabinet. UL

approved.

Model ST70 70 -Watt Integrated Stereo Amplifier.

Best buy of highest ranked stereo amplifiers

according to independent testing. $99.95 kit,

$149.95 wired. ST40 40 -Watt Integrated Stereo

Amplifier, $79.95 kit, $129.95 wired. ST97 Match-

ing FM MPX Stereo Tuner, $99.95 kit; $139.95

wired,

FREE 1966 CATALOG

EICO Electronic Instrument Co., Inc. EE -6

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

Send me FREE catalog describing the full EICO

line of 200 best buys, and name of nearest

dealer. I'm interested in:

test equipment ham radio

stereo /hi -fi Citizens Band radio

Name

Address

City

State Zip

1945 -1965: TWENTY YEARS OF LEADERSHIP IN CREATIVE ELECTRONICS

www.americanradiohistory.com

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Accredited Member National Home Study Council

TuLY-AucusT, 1966

1

www.americanradiohistory.com

ELEMENTARY

ELECTRON /CS

JULY -AUGUST 1966

THEORY

23 Electricity, Magnetism and the Atom

37 Basics of RTTY

41 RTTY in the Shack

45 Using Cross -Coupled Circuits

58 Block that Leak

63 Angles on DX

77 Making Zener Diodes Work for You

81 Electroplating for the Hobbyist

83 Those Fabulous Fuel Cells

CONSTRUCTION

59 Breaking the Crystal Barrier

't 67 SCR Slot -Car Starter

* 71 Stereophone Server

87 SCR Touch -Control Switch

92 Calibrated Attenuator

FEATURES

16 Electronics on Wheels

18 Traffic A Go Go

49 Build 'em Good

57 Hartman Marine -Auto Converter Report

65 Knight -kit Safari I CB Transceiver Report

74 Suitcase Workshop

76 TV on the Go

90 TV Schooling in the Hospital

95 Speedy Readin'

101 Network on the Prowl

104 Have Brains, Will Travel

DEPARTMENTS

8 NewScan

19 E/E Etymology

21 En Passent (Chess Column)

96 FCC Q & A

103 DX Central Reporting

108 Literature Library

AUTHORS FEATURED IN THIS ISSUE:

Jack Brayton, Len Buckwalter- K1ODH /KBA4480, John W.

Collins, Lester Escargot, James A. Fred, Herb Friedman -

W2ZLF/KB19457, Charles Green- W31KH, Carl L. Henry,

Robert E. Kelland, K.C. Kirkbride, John D. Lenk, Marshall

Lincoln- K9KTL, A. A. Mangieri, Martin H. Patrick, C. M.

Stanbury Il, Art Trauffer

Cover Photo by Leonard Heicklen * Cover Highlights

NOW THERE ARE OVER 85 RADIO

SHACK STORES COAST TO COAST

ARIZONA

PHOENIX - 3905 East Thomas Rd.

CALIFORNIA

ANAHEIM -507 Eut Natalia Ave.

BAKERSFIELD - 1308 19th St.

LA HABRA -1511 West Whittler Blvd.

LONG BEACH - 3976 Atlantis Ave.

LOS ANGELES:

Downey -Wormwood Shop. Ctr.

Ladera Shop. Ctr. - 5305 Centinela Ave.

Mission Hills- 10919 Sepulveda Blvd.

Reseda- 19389 Victory at Tampa

Torrance - 22519 Hawthorne Blvd.

West Coyly. -2518 Eut Workman Ave.

West L. A. - Pleo Blvd. at Overland

OAKLAND (Ban Leandro) - Bay Fair Shop. Ctr.

SACRAMENTO - 600 Fulton Ave.

SAN DIEGO (La Mete) - Grossmont Shop. Car.

SANTA ANA - Bristol Plaza Shop. Ctr.

COLORADO

DENVER:

798 South Santa Fe Dr.

Westland Shopping Center

CONNECTICUT

HAMDEN - Hamden Mart. Shop. Ctr.

MANCHESTER - Manchester Shop. Parkode

NEW HAVEN -92 York St.

NEW LONDON - New London Shop. Ctr.

STAMFORD - 29 High Ridge Rd.

WEST HARTFORD - 39 So. Mein St.

GEORGIA

ATLANTA - Greenbrier Shopping Center

ILLINOIS

CHICAGO - Ev Plaza at 95th St.

MAINE

PORTLAND - Pine Tree Shop. Ctr.

MARYLAND

LANGLEY PARK - HampahirsLanIley Ctr.

MASSACHUSETTS

BOSTON:

167 Washington St.

594 Washington St.

110 Federal St.

BRAINTREE - South Shore Plaza

BROCKTON - Westgete Mall

BROOKLINE -730 Commonwealth Ave.

CAMBRIDGE - Fresh Pond Shop. Ctr.

FRAMINGHAM - Shopper.' World

LOWELL - Central Shop. Plus

SAUGUS -N. E. Shop. Ctr.

WEST SPRINGFIELD - Century Shop. Ctr.

WORCESTER - Lincoln Plaza

MINNESOTA

MINNEAPOLIS - 1121 Nieollet Ave.

ST. PAUL -473 North Snelling

MISSOURI

ST. 125 Pine St. (Welter Ache Div.)

South County Shopping Center.

Northland Shopping Center

NEW HAMPSHIRE

MANCHESTER- 1247 Elm St.

NEW MEXICO

ALBUQUERQUE -á31S Lomu, N. E.

NEW YORK

BINGHAMTON (Vestal)- Vestal Shop. Plaza

BUFFALO (Clarence) - Transitown Shop. Gtr.

NEW YORK - 1126 Ave. of the Amer kas

SC ENECTADY (Rotterdam) - Shoporema Ctr.

SYRACUSE:

3057 Erie Blvd. East.

Fairmount Feb. Shop. Ctr.

OHIO

CINCINNATI -852 SwItton Ctr.

OKLAHOMA

OKLAHOMA CITY - Mayfair Shop. Ctr.

TULSA - 2730 South Harvard

OREGON

PORTLAND -1928 N.E. 42nd St.

PENNSYLVANIA

PHILADELPHIA:

2327G Cottman Ave., Roosevelt Mall

1128 Walnut St.

PITTSBURGH -309 Se. Hill. Village

RHODE ISLAND

CRANSTON - 1301 Reservoir Ave.

EAST PROVIDENCE - Shoppers' Town

TEXAS

ABILENE -2910 North First St.

ARLINGTON - Collins at Park Row

AUSTIN - Hancock Shopping Center

BROWNSVILLE -847 S. E. Elizabeth SL

DALLAS:

Medallion Center

125 Wynnewood Village

Plymouth Park Shop. Ctr.

FORT WORTH:

ISIS So. University Dr.

900 East Berry St.

3520 Denton Highway

2615 West 7611 St.

HOUSTON:

8458 Gulf Freeway

322 Northllne Mall

Bellaire- 4759 Bluonnet

SAN ANTONIO:

150 Wonderland Shop. Ctr.

684 8.W. Military Drive

SHERMAN - 1820 Highway 75 North

WACO -1018 Austin Ave.

UTAH

SALT LAKE CITY - Cottonwood Mall

VIRGINIA

ARLINGTON - WeshingtonLee Shop. Cir.

WASHINGTON

SEATTLE:

2028 Third Ave.

837 N. E. 110th St.

Burlen Plaza

2 ELEMENTARY ELECTRONICS

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SURPRISE PAKS

At a fraction of their cost -

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60 -pc Transistor

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2 98 NPN's,PNP's

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27 -034 2.98

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198 Parabolic re-

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60 -pc Jumbo Rectifier

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198

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27 -1516

JULY -AUGUST, 1966

1-70 Wireless Phono Oscillator Module: designed to play your phonograph.

directly through a radio without connecting wires. 27-257 .... 4.95

Intercom Amplifier Module: custom -build a modern, convenient inter-

com system for your home or office. 27 -254 4.95

"Baby- Sitter" Amplifier Module: gives real peace of mind; even lets

you monitor sound of baby's breathing. 27-256 4.95

Phonograph Amplifier Module: designed for use with crystal or

ceramic cartridge. 2 watts peak power. 27 -261 4.95

Telephone Amplifier Module: permits "group- listening" to a phone

conversation; talk with hands free. 27 -260 4.95

Super High -Gain Amplifier Module: for use as a hearing aid, audio

signal tracer, "eavesdropper ", etc. 27 -251 4.95

Power Amplifier Module: the ideal amplifier to use with tuners,

microphones, paging systems, or as signal tracer. 27 -253 4.95

Guitar Amplifier Module: can be used with guitars or any stringed

instrument. 2 watts peak power. 27 -255 4.95

AC Power Supply Module: converts 115 VAC to 6 VAC, 1 amp. Use

with rectifier -electronic filter (below). 27 -258 1.95

Rectifier -Electronic Filter Module: provides dual DC output from AC

power supply. 6 VDC; 24V max., 1 amp. 27 -259 3.95

Cl

0

Optional Accessories for Modules Above

Cat. No. Description

27 -1430 Loopstick Antenna

23 -465 "C" Cells (4 required)

27 -1437 Battery Holder (2 required)

23 -006 6V Lantern Battery

27 -258 AC Power Supply

27 -259 Rectifier- Electronic Filter

40 -1203 4" Speakers (2 required)

27 -1384 4PDT Switch

27 -066 50052 Control w /Switch

40 -219 8" Extension Speaker

27 -1264 100 -Ft. Speaker Wire

33 -100 Lapel Microphone

27 -212 500K Control w /Switch

40 -1213 8" Speaker

44 -533 Telephone Pickup

33 -180 Headphone

23 -468 Penlight Batteries (2 required)

27 -1433 Battery Holder

33 -918 Dynamic Microphone

33 -115 Contact Type Microphone

Key Letters Each

A A A

B, C, D, E, G, H

B,C,D,2,G,H

B, C, D, E, G, H

B

C

C, F

D, E, F H

D, E, G, F

E

F G H

MAIL

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Please send FREE 1966 Radio Shack Catalog! EE -7 -66

Please send me the modules and accessories I have

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$ $2.00 Solid-State

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postage and handling anywhere in the U.S.A.

v

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ELEMENTARY

ELECTRONICS

JULY -AUGUST 1966 Vol. 2 No. 3

Dedicated to America's Electronics Experimenters

JULIAN M. SIENKIEWICZ Editor

WA2CQL /KMD4313

WILLIAM HARTFORD Technical Editor

KKD7432

ELMER C. CARLSON

KOD1752 Construction Editor

RON STAFFIERI Art Editor

ANTHONY MACCARRONE Art Director

IRVING BERNSTEIN Corer Art Director

EUGENE F. LANDINO Associate Art Director

JUDITH ANDERSON Art Associate

ELLIOT S. KRANE Advertising Director

JIM CAPPELLO Advertising Manager

LEONARD F. PINTO Production Director

CARL BARTEE Production Manager

HELEN GOODSTEIN

CLIFF SHEARER

JOSEPH DAFFRON

Assistant Production Manager

Promotion Director

Erecutire Editor

President and Publisher

B. G. DAVIS

Erecutire Vice President and Assistant Publisher

JOEL DAVIS

Vire President and Editorial Director

HERB LEAVY, KMD4529

117111711 OW

HIGH FIDELITY s

ELEMENTARY ELECTRONICS, Vol. 2, No. 3 10931 is published bi-

monthly by SCIENCE& MECHANICS PUBLISHING CO., a subsidiary

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

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

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

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

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

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

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

& Brown, 3108 Piedmont Rd., N.E., 404. 233.6729; Long Island: Len Osten,

9 Gorden Street, Great Neck, N. Y., 516- 487 -3305; Southwestern ad-

vertising representative; Jim Wright, 4 N. Eight St., St. louis, CH 1 -1965.

EDITORIAL CONTRIBUTIONS must be accompanied by return postage

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

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

photographs. All contributions should be addressed to the Editor,

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

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

4 ELEMENTARY ELECTRONICS

11

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JULY -AUGUST, 1966 5

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8 HEATHKIT® Values...See The

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AM /FM /Shortwave Portable

Tour The Voice Capitals Of The World! 7 bands

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and a 88 -108 mc FM band offers you quiet, re-

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a 150 -400 kc longwave band for aircraft and

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Boasts 16 Transistors, and 44 Prebuilt & Aligned

RF Circuits; separate FM tuner & IF strip (same

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built -in antennas; 4' x 6' speaker; battery -saver

switch. Operates anywhere on 7 flashlight bat -'

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converter, $6.95. Build in only 10 hours. 19 lbs.

Deluxe 5 -Band Shortwave Radio! Low Cost AM /Shortwave Radio!

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Kit GR -54

4 bands cover 550 kc to 30 mc. Built -in 5'

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antenna. 15 lbs.

Kit GR -64

6

23- Channel 5 -Watt Solid -State

CB Transceiver!

Kit GW -14

$8995

Assembled GWW -14

$1 2495

23 crystal- controlled transmit & receive channels for

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ideal for car, boat, any 12 v. neg. gnd. use. "S"

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Other 242 In FREE Catalog!

New 30 -Watt Transistor FM Stereo Receiver

Kit AR -14 $V995

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31 transistors, 11 diodes for transparent

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Best Hi -Fi News of '66 ... New Low Cost Transistor Stereo Twins!

New Transistor FM /FM Stereo Tuner

Assembles in only 4 to 6 hours! 14

transistor, 5 diode circuit; 5 uy sensi-

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Kit AJ -14

$4995

(less cab.)

Matching 30 -Watt Stereo Amplifier

Assembles in 10 hours! 17 transistor, 6

diode circuit 20 watts RMS, 30 watts

IHF music power @ ±1 db from 15-

50,000 cps; Handles tuner, phono, aux-

iliary. No audio transformers ... assures

lower distortion, minimum phase shift.

Install in a wall, or either Heath cabinet

(walnut $7.95, beige metal $3.50). 10 lbs.

Kit AA -14

$5995

(less cab.)

HEATHKIT 1966

JULY- AUGUST, 1966

Deluxe 6- Transistor AM Portable!

Surpasses miniatures in performance and econo-

Kit GR -24 my! Boasts large 4" x 6" speaker for a crisp, bold

sound; slide -rule dial; "thumb- touch" controls;

smooth vernier tuning; tuned RF stage & double -

tuned IF stage for greater sensitivity and selec-

tivity; big 1/4" diameter rod antenna for distant

station pickup; handsome black simulated leather

case. Build in 4 to 6 hours. Uses long -life "D"

size flashlight batteries (not included). 5 lbs.

$2825

FREE

1966

Catalog!

Describes these and

over 250 electronic

kits . world's

largest selection.

Mail coupon, or

write Heath Com-

pany, Benton Harbor,

Michigan 49022.

ITN 1

Heath Company, Dept 139.7

Benton Harbor, Michigan 49022

Enclosed is $ plus shipping. Please send model(s)

Please send FREE 1966 Heathkit Catalog.

Name

Address

City State

Prices & Specifications subject to change without notice. CL-242

Zip

7

www.americanradiohistory.com

IN THE JULY ISSUE OF

SCIENCE & MECHANICS

READ THE SECOND FANTASTIC

DOCUMENTED FEATURE ON

THE "MANNED"

SOVIET

SPACE FLIGHTS

THAT WERE

NEVER

MANNED!

íßf. Cienct &I

Mechanic

NEW

ELECTRIC

CAR!

WORLDS TOP ASTROLOGERS

PREDICT THE FUTUREI

IR E-t41 lei Wm SA& R- WW1

NOW

ON

SALE

"My contention is that the Soviet Union uses its

real -and often very crude -achievements in space

research as a springboard for spectacular hoaxes.

Foremost among these hoaxes is their manned

spaceflight program. The status of their technology

cannot support a man -in -space program at this time.

Nor have they ever actually documented one of

their manned spaceflights beyond a question of

doubt. How do I know this? SCIENCE & MECHANICS

assigned me to the job of unearthing this and

many other phony qualities inherent in flights of

the Russian manned space ships." So began space

expert Lloyd Mallan's sensational expose of "The

Russian Spacemen Who Weren't There."

Don't miss the second of 3 provocative AND docu-

mented articles in the July issue of SCIENCE &

MECHANICS, now on sale at your newsstand.

SCIENCE & MECHANICS MAGAZINE

505 Park Avenue

New York, N. Y. 10022

o \EWSCA

Out of the Dark

A newly designed lighting system for the

interior lighting of trailers and truck bodies

permits loading and unloading operations to

be completed quickly, accurately and safely.

The system is the first for van lighting which

can operate fluorescent lamps off either con-

Lighting system for truck

provides adequate illumination

for rapid, accurate and safe

loading and unloading of cargo.

General Electric's newly designed

system permits operation of 15-

watt fluorescent lamps off

either 120 -volt dockside power

or the truck's 12 -volt battery.

ventional 120 -volt dockside power or the

truck's .12 -volt battery power. Trailers nor-

mally loaded and unloaded at docks need to

be equipped to utilize only 120 -volt power

from the loading dock. Delivery trucks and

others which operate away from docks

trailers

s ELEMENTARY ELECTRONICS

www.americanradiohistory.com

E

Live Better Electronically With

LAFAYETTE

RADIO ELECTRONICS

it REÜDt BECTRDt1ICAtLI W11N LARiRITE .,. F 1966

OUR 4s11FYEAR

Catalog 666

lndex-P+te501

Over 500 Pages

R E

TV Tibes and Parts

',Electronic Parts

Test Equipment

Citizens Band

Tools

Ham Gear

Stereo Hi -Fi

Tape Recorders

Walkie- Talkies

Auto Accessories

LAF AY ETTE

RADIO ElKS RONKS

:1 i

00ppöQy

1966 Catalog 660

Featuring Everything in Electronics for

HOME INDUSTRY LABORATORY

from the

"World's Hi -Fi & Electronics Center"

LAFAYETTE Radio ELECTRONICS

LAFAYETTE'S MAIL ORDER &

LONG ISLAND

SALES CENTER

Dept. DEEG -6, P.O. Box 10, Syosset, L.I., N.Y. 11791

Cut out and Mail Coupon for FREE Lafayette Catalog

Send me the Free 1966 Lafayette Catalog 660

Name

Address

City State

Zip (Please Give Your Zip Code No.

111 Jericho Turnpike

Syosset, Long Island, New York

OTHER LOCATIONS

NEW YORK NEW JERSEY MASSACHUSETTS

Brooklyn Newark Boston

Syosset Paramus Natick

Manhattan Pla nfield MARYLAND

Jamaica Connecticut Mt. Rainier

Scarsdale New Haven (Wash. D. C. A-eal

Bronx West Hartford

Dept. DEEG -6

www.americanradiohistory.com

NEWSCAN

should be equipped with a special General -

Electric- developed inverter -ballast. This

makes it possible for fluorescent lamps to be

operated off battery power.

Basic components of the system in each

trailer are four 15 -watt fluorescent tubes

housed in especially designed, single -lamp

fixtures, and a male plug inside the door.

The docks they use are equipped with a

switch, cable and female plug. The fixtures,

only about three inches deep, are higher than

the door opening when mounted on the ribs

of the trailer roof. This minimizes the pos-

sibility of damage during loading and un-

loading operations. Lighting levels are about

eight footcandles, three times as high as exist

in the average well -lighted parking lot.

High frequency current from the inverter -

ballast increases the efficiency of fluorescent

lamps. With this gain, plus the inherent effi-

ciency advantages of fluorescent over incan-

descent light sources, the new system pro-

duces at least four times as much light as

conventional light bulbs of the same wattage

with no increasing battery drain.

Seeing Infrared

Infrared light like that used in many mod-

ern cooking ranges may soon carry valuable

data to astronauts on expeditions into deep

space. Beams of the invisible, infrared light

may be used to carry thousands of coded

messages between ground tracking stations

and missiles. The light beams are part of a

new data link system developed by the Gen-

eral Electric Company. The feasibility of

this new method of sending information has

been proven recently by the successful trans-

mission of an extremely clear television pic-

ture. The new system was designed to relieve

the growing congestion of the airwaves at

missile test ranges. Presently, the increased

message load is straining the number of avail-

able radio channels. However, the situation

will become even more acute in the future.

For example, larger launch vehicles will re-

quire additional monitoring functions. In-

creased complexity of space missions will de-

mand transmission of even greater quantities

of messages. Interference -free transmission

of messages is also a big advantage of the

new data system. With the light beams there

is no interference with or from radio waves.

Although the new gallium arsenide sys-

tem is an outgrowth of laser technology, it

10

does not employ a laser as a light source.

The diode employed as the light source differs

from a laser in that it produces light directly

proportional to the current passed through

it, whereas the laser diode produces more

light at a higher rate than the increase in cur-

rent. It is predicted that the new data system

will be more popular than laser systems, espe-

cially for relatively short range use where

total cost is of great importance.

In addition to transmitting data from the

ground to a missile, the new system has other

potential applications. For example, in send-

Television picture is transmitted

over an invisible light beam,

demonstrating new data link system

developed by the General Electric

Company's Radio Guidance Opera-

tion, Syracuse, N. Y. Actual

system consists of compact trans-

mitter shown at far left and

receiver shown on top of the TV

monitor. It may soon be used to

carry valuable data to astronauts,

to transmit other data from one

location at a missile launch

center to another, or to carry

signals from a radio or TV studio

to a transmitter.

ing guidance and instrumentation messages

from missile pad to block house, block house

to launch operation center and from range

safety TV vans to launch operation control.

The advantages of the gallium- arsenide

method over conventional radio systems in

these uses are: it has less equipment, is less

costly, lighter and more compact. The new

system consists, simply, of a transmitter

which is about the size of a loaf of bread. It

ELEMENTARY ELECTRONICS

e

www.americanradiohistory.com

BUILD 20 RADIO

CIRCUITS AT HOME

with the New Improved

PROGRESSIVE RADIO "EDU -KIT "®

A Practical Home Radio Course

Now Includes

* 12 RECEIVERS

* 3 TRANSMITTERS

*SQ. WAVE GENERATOR

* SIGNAL TRACER

* AMPLIFIER

* SIGNAL INJECTOR

* CODE OSCILLATOR

Reg. U. S.

Pat. Off.

* No Knowledge of Radio Necessary

* No Additional Parts or Tools Needed

* EXCELLENT BACKGROUND FOR TV

* * Sold In 79 Countries

SCHOOL INQUIRIES INVITED

YOU DON'T HAVE TO SPEND

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The "Edu -Kit" oners you an outstanding PRACTICAL HOME RADIO COURSE at a

rock -bottom price. Our Kit is designed to train Radio 8 Electronics Technicians. making

use of the most modern methods of home training. You will learn radio theory, construc-

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

You will learn how to build radios, using regular schematics: how to wire and soiden

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

punched metal chassis as Well as the latest development Of Printed Circuit chassis.

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

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

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

troubleshooting, uSing the Progressive Signal Tracer. Progressive Signal Injector. Pro-

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

ing instructional material.

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

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

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

will receive an r xcellent background for television, M1 -Fi and Electronics.

Absolutely no previous knowledge of radio or science s required. The Etlu Kit" is

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

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

price o pay. The Si' nal Tracer alone is worth more than the rive of the kit.

THE KIT FOR EVERYONE

You do not need the slightest background

In radio Or science. Whether you are inter-

ested in Radio 8 Electronics because you

Want an Interesting hobby. a well paying

business or a job with a future. you will hod

the "Edu -Kit" a worthwhile investment.

Many thousands of Individuals of all

ages and backgrounds have successfully

used the Edu Kit in more than 79 coun-

tries of the world. The , EduKlt" has been

carefully designed. step by step. so that

you

allows k mistake. d

llows you to teach yourself at your own

rate. No Instructor Is necessary.

PROGRESSIVE TEACHING METHOD

The Progressive Radio 'Edu Rill" Is the foremost educational radio kit in the world.

and is universally accepted as the standard in the held of electronics training. The "(du-

Nit" uses the modern educational principle of Learn by Doing." Therefore you construct,

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

gram designed to provide .in easolyivarnell. thorough and Interesting background in radio.

You begin bye m ning the various adio parts of the 'Edu -Kit." You then learn the

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

Set you will enjoy listening to regular broadcast stations. learn theory. practice testing

and trouble Shooting. Then you build a more advanced radio. learn more advanced theory

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

lined yourself constructing more advanced multi -tube radio circuits, and doing work like a

professional Radio

the T'Édu.K,t" course are Receiver, Transmitter, Code Oscillator. Signal

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

breadboard" experiments, but genuine radio circuits. constructed by means of professional

wiring and soldering on metal chassis, plus the new method of radio co s truction known

as "Printed Circuitry." These circuits o rate on our re ulcer AC or DC house current.

You w 11 receive all parts and instructions necessary to build twenty different radio and

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

able, electrolytic, mica, ceramic and paper dielectric tond eeeere, resistors, tie strips,

hardware, tubing, punched netal chassis, Instruction Manuals, hookup Wire, solder,

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

In addition, you receive Printed Circuit materials, including Printed Circuit chassis.

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

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

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

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

servicing with the Progressive S,ilnal Tracer and the Progressive Signal Injector, a Nigh

Fidelity Guide and a Quiz Book. You receive Membership in Radio -TV Club. Free Consulta-

tion Service, Certificate of Merit and Discount Privileges. You receive all parts, toots,

instructions. etc. Everything is yours to keep.

PRINTED CIRCUITRY

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

now Includes Printed Circuitry. You build

a Printed Circuit Signal Injector, a unique

servicing instrument that can detect many

Radio and TV troubles. This revolutionary

new technique of radio construction is now

becoming popular in commercial radio and

TV sets.

A Printed Circuit is a special insulated

chassis on which has been deposited a con-

ducting material which takes the place of

wiring. The various parts are merely plugged

in and soldered to terminals.

Printed Circuitry is the basis of modern

Automation Electronics. A knowledge of this

subject Is a necessity today tor anyone in-

terested in Electronics.

JULY -AUGUST, 1966

Training Electronics Technicians Since 1916

FREE EXTRAS

SET OF TOOLS

SOLDERING IRON

ELECTRONICS TESTER

PLIERS -CUTTERS

VALUABLE DISCO1/NT CARD

CERTIFICATE OF MERIT

TESTER INSTRUCTION MANUAL

NIGH FIDELITY GUIDE QUIZZES

TELEVISION BOOK RADIO

TROUBLE-SHOOTING BOOK

MEMBERSHIP IN RADIO -TV CLUB:

CONSULTATION SERVICE FCC

AMATEUR LICENSE TRAINING

PRINTED CIRCUITRY

I SERVICING LESSONS

You will learn troubleshooting and

servicing in a progressive m . You

Will practice repairs on the sets that

and causesu of trouble) will learn

l homes symptoms

ol

and car radios. You will learn how to

use the professional Signal Tracer. the

unique Signal Injector and the dynamic

Radio A Electronics Tester. While you

are Iiii- 111,1,' tu in do any a l l replir job for

your friends and c, lghllorsand charge

fees whtch will lin exceed the price of

the 'Edu -Kit." Our Consultation Service

will help you with ally technical prob-

lems you may have.

FROM OUR MAIL BAG

.1 Stataitis, of 25 Poplar PI., Water-

bury, Conn.. writes: 1 have paired

several sets for my friends. and made

money. ady to spend $240

i s

paid for a (Course.

s

but I found your ad and sent for your

Kit." Ben Valerio, P. 0. Box 21. Magna,

Utah: "The Edu -Nits are wonderful. Here

1 am sending You the questions and also

bee n in

the answers

Radio tor the l last seven) years. but a like

to work with Radio Kits. and like to

build Radio Testing Equipment. I en

payed every minute I orked with the

finer Also tuts: like to Signal

t you Tracer works

know that I

feel proud of becoming a member of your

Radio -TV Club."

Robert L. Shutt. 1534 Monroe Ave..

Huntington, W. Va.: 'Thought I Would

drop you a few lines to say that I re-

ceived my Edu -Kit, and was really amazed

that such a bargain can be had at such

a low price. I have already started re-

pairing radios and phonographs. Me

friends were really surprised to see e

et into the ing of it so quickly. The

Trouble-shooting Tester that comes with

te Kit Is really swell, and finds the

trouble, if there is any to be found."

r UNCONDITIONAL MONEY -BACK GUARANTEE----1

1 ,

ORDER FROM AD- RECEIVE FREE BONUS

RADIO & TV PARTS JACKPOT WORTH $15

t.

O Send i 'Edu -Kit" postpaid. I enclose full payment of $26.95.

O Send 'Edu -Kit" C.O.D. I will pay $26.95 plus postage.

O Rush me FREE descriptive literature concerning Edu -Kit."

Name

Address

PROGRESSIVE "EDU- KITS" INC.

1186 Broadway, Dept. 513DJ, Hewlett, N. Y. 11557

11

www.americanradiohistory.com

NEWSCAN

has an electronic "bulb" which emits the

infrared light. The light is then bounced off

a flashlight -like reflector and beamed to a re-

ceiver the size of two loaves of bread end to

end. The system is unique because it has the

widest bandwidth ever reported in this type

of device -the wider the bandwidth the

greater the number of messages which can

be transmitted.

Communications with a Bounce

A small satellite communications ground

station enables an Army commander to go to

isolated trouble spots anywhere on the globe

and remain in contact via satellite with mili-

tary and government authorities here in the

U. S. or other world -wide communication

centers.

The experimental ground station provides

an answer to a problem which has plagued

military commanders throughout history -

the need of far- ranging armies to maintain

communications with their leaders back

home. This system will enable a commander

to literally take his telephone and teletype

with him wherever he goes and `plug in' to a

satellite communications network.

Details of the compact unit, the first ever

designed to be transported by helicopter,

were disclosed as the portable station was

turned over to the Satcom agency for field

demonstration at MacDill Air Force Base,

near Tampa, Fla. The ground terminal, con-

sisting of a collapsible 15 -foot antenna and a

6 -by -8 hut, is designed for use with the Syn-

com communications satellite and will re-

1 , ,,,,,,1111.1111111111111,,,,,,1,1011111111111111,.,, 1,,1 111111 1 ,,,,,, I,. IMIM,,,I

..

ceive and transmit both telephone and tele-

type messages at the same time. It will also

send and receive fascsimile pictures.

With three Syncoms in orbit, an Army

unit could be flown to any brush -fire war

area, set up its antenna in an hour, point it

at one of the satellites and immediately be

in direct voice contact with Washington.

Such satellite linkage uses microwave fre-

quencies and is not subject to the magnetic

storms which now hinder transoceanic radio

telephone transmission and often knock it out

for days at a time. Besides its use for mili-

tary communications, the unit could be em-

ployed to restore civilian communications in

areas where service is disrupted by disaster

or war. It could be used to communicate

with other ground terminals whether 10

miles away or 10,000 miles away.

The demonstration model built for the

Army consists of three units- antenna, com-

munications hut and power supply- weigh-

ing 10,000 pounds combined. It can be '

transported in cargo planes or lifted by heli-

copter into remote areas where no plane run-

ways exist. It uses a transmitter and para-

metric amplifier, both manufactured by

Hughes. The transmitter is a solid- state,

liquid- cooled unit using a klystron converter

tube with a power output of two to three

kilowatts. Excess noise temperature of the

parametric amplifier is 100 degrees Kelvin,

it is uncooled, and has two stage 40 db gain.

The receiver used with the station is a phase -

locked FM tracking receiver with two IF

bandwidths in the 30- and 10- kilocycle band-

widths, and has an IF frequency of 30 mega-

cycles.

11111111111111111111 11

12

11 11 Uli

This new portable communications

ground station has been developed

as a "space link partner" of

Syncom to enable isolated military

units anywhere in the world to

stay in constant touch, via

satellite relay, with leaders

back home of other units only 10

miles away. This first helicopter -

transportable system for use in

remote battle areas was developed

by Hughes Aircraft Company for

the U.S. Army's Satcom Agency.

The 15 -foot air -inflated collap-

sible antenna (at lower left)

is shown in symbolic relation

to the Hughes Syncom communica-

tions satellite (top right) which

would relay the ground station's

voice and teletype signals from

its synchronous orbit 22,300

miles above the earth.

M,,,,,,,10,,,,,,1,,W,M,,,,1111111111M1111111.11111111M1111111111111.111111111110...,,, ,,,111110,1M1M111111,1101111nfflUIM11111111111MHIUMM MI

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

UNUSUAL BARGAINS

Electronic Conference Room

A unique conference room that can com-

municate with its occupants has been set up

at the Federal Aviation Agency Aeronautical

Center in Oklahoma City. It's a room where

the ceilings have ears and the walls have

voices. A flick of a switch can cause the

room to dim its lights, create pictures on its

walls, draw back curtains to reveal magnet-

ic chalk- boards, and talk via audio tapes.

The room can repeat conversations that took

place within its walls only seconds before.

This conference room, with is complete com-

munications system, is a pacesetter that may

be copied widely throughout government

and industry in the next five years. It marks

the first time that audio equipment has been

used to its full capabilities in helping people

communicate.

The difficult task of designing the facility,

complete with audio -visual capabilities, was

undertaken by engineers of the Aeronautical

Center's Plant Engineering Division. They

have created a communications system that is

actually two complete sound systems within

the conference room.

The first is a stereophonic speaker system

linked to the AM- FM- Multiplex tuner, tape

recorder, phono turntable, projection TV

tuner and 16 -mm projector. Comprised of

three University Medallion speaker systems,

the stereo sound units are mounted flush with

the wall below the rear -projection screen.

The 18 -foot wide rear projection screen

may have a 16- millimeter moving picture and

two 35- millimeter slides projected simulta-

neously. The projector lenses and light

sources provide images balanced as to size

and brightness.

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SOLVE PROBLEMS! TELL FORTUNES! PLAY GAMES!

NEW WORKING MODEL DIGITAL COMPUTER

ACTUAL MINIATURE VERSION

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F rselnating new see -through model computer

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shifts, complements, carries, m emorizes, counts,

r compares, sequences. Attractively colored, rigid

plastic Intl easily assembled. x gram" x

4: ; ". Incl. step -by-step assembly diagrams.

32 -page instruction book covering operation, computer language

binary system), programming, problems and 15 experiments.

Stock No. 70,683- EK............ $5.98 Postpaid

DETAILED PROGRAMMING BOOKLET FOR EXPERIMENTS

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EXPLORE THE WORLD OF "OP ART"

Fascinating New Experimenters'

MOIRE PATTERNS KIT

Fantastic Visual Effects! Limitless Applications

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country in art, fashion, packaging industries. 1,000's

of uses for hobbyists, photographers, designers, lab

and hume experimenters. Fun: Profitable! Unlimited

potential. Here's your complete introduction kit developed by Dr.

Gerald Oster, Brooklyn Poly. Inst. Contains 8 basic patterns on both

clear acetate lantern slide size 32/4" x 4" (.020 thick) and .012"

thick white Kromekute paper 3.á' x 41 /z" (coated one side): two

piece 31/4" 4" 150 -dot screen on film, copy Dr. Oster's book, "The

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Stock No. 60,464 -EK (without book) $6.50 Postpaid

NOW AVAILABLE IN FULL COLOR

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Eight new totally different black and hile patterns: Coarse sines;

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NEW MOIRE KIT "B" IN COLOR

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Stock No. 60- 531 -EK $

MOIRE PATTERN ACCESSORY KIT

For dditional experiments. Incl. metallic balloon, calcite, two kinds

of diffracting gratings, one-way mirror film polarizing materials.

Ronchi rulings, assortment of lenses. B 00 Ppd.

Stock No. 60,487 -EK $

"Balls of Fun" for Kids

SURPLUS GIANT WEATHER BALLOONS

Panoramic view of conference

room at Oklahoma City's FAA

Aeronautical Center shows place-

ment of ceiling sound system.

Microphones are behind audio

grilles along inside edge of

lights; speakers are mounted along

outside rim of light fixtures.

Air conditioning ducts form cen-

ter of ceiling pattern.

At last available again in big 8 ft. d(am-

eter. Create a neighborhood sensation. Great

backyard fun. Exciting beach attraction. Blow

up with vacuum cleaners or auto air hose.

Sturdy enough for hard play; all other uses.

Filled with helium (available locally) use e bal-

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Amateur meteorologists use balloons to mea-

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pressure, humidity at various heights. Photog-

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Recent Gov't. surplus of heavy, black, neoprene

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Stock No. 60,568 -EK ............$2.00 Ppd.

SLIGHTLY HEAVIER RUBBER -LATER MANUFACTURE:

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Order by Stock No. -Send Check or M.0.- MoneBack Guarantee

EDMUND SCIENTIFIC CO., Barrington, New Jersey

MAIL COUPON for FREE CATALOG "EK"

.1141

EDMUND SCIENTIFIC CO., Barrington, N. 1.

Completely New 1966 Edition. 148 pages.

Nearly 4500 Bargains.

Please rush Free Giant Catalog-MC

Name

Address Zip

City State Code

JULY -AUGUST, 1966 13

www.americanradiohistory.com

NEWSCAN

The second and more complicated sound

system is designed to pick up and amplify

voices within the room and to tape record

conversations taking place at its conference

table. This second system has given the most

headaches to FAA engineers who designed

the communications network. It has been

largely a matter of experimentation, and the

approach to the acoustics problem had to be

altered several times.

This sound system includes nine University

Model 1150 microphones and seven speakers

in the ceiling, arranged so that the speakers

do not interfere with the microphones. The

microphones are special professional "car -

dioid pattern" like those used by many radio

and 'television networks.

The ceiling sound system is arranged to

cover every portion of the specially -built oval

conference table which sits in the center of

the room. Words spoken at the table are

picked up by the overhead microphones, fed

into amplifiers and back into the dual cone

speakers in the ceiling. These microphones

and speakers are engineered so that words

picked up by mikes in the front of the room

are amplified more in the speakers at the

back of the room, and vice versa. Feedback

from speakers to microphone is practically

non -existent at optimum usable loudness.

Nerve center of the sound system is a con-

trol panel on the lectern at one end of the

room and a duplicate control panel which is

recessed into the end of the conference table

opposite the removable portion.

The lectern itself has a built -in drinking

water spigot for the speaker, a motorized

height adjustment mechanism, an ash tray,

clock timer, reading light and light to illu-

minate the speaker's face. Standing at the

lectern or table control panel, the speaker

can control the room merely by pushing but-

tons. A buzzer into the projection room sig-

nals the operator to start or change the view -

graph image. A dual setup for projectuals

allows one to be switched while the other is

being shown. The room's fluorescent light-

ing can be dimmed or turned off in sections -

front, center and rear. Another button will

automatically open and close drapes along

one wall which conceal magnetized chalk-

boards. As the drapes open, lights come on

to illuminate the chalkboard image. Finger-

tip control allows the speaker to record con-

versation in the room, stop the recorder, re-

14

Pushbutton lectern - -at the FAA

electronic conference room - -as

well as control board at center

table - -puts all sound and visual

systems at the speaker's finger-

tips. Lectern raises and lowers

automatically, has built -in

lights, water spigot and ashtray.

wind it, play back what it has recorded, or

move it forward. The 16- millimeter projec-

tor can be turned on and off by push- button

control. The lectern and table panels also

control the two speaker systems (stereo and

overhead) and two 35- millimeter slide pro-

jectors. A digital selector allows random ac-

cess to each 100 -slide magazine, and both 35-

millimeter projectors can be used at once.

Perhaps the most amazing thing about the

room is that it has been put together with

fully developed, manufactured sound equip-

ment -yet its capabilities are almost un-

matched anywhere.

Electronic Lung Power

The New York Jets of the American Foot-

ball League may have solved the problem of

crowd noise that often drowns out the audi-

ble signals which quarterbacks frequently

call at the line of scrimmage to change plays

at the last minute. A specially designed hel-

met seems to be the answer. The helmet con-

tains a transistorized public address system

which boosts the quarterback's voice to about

three times louder than a TV set turned on

full blast. The Jets now have four of these

helmets ready for use.

Six transistorized radio loudspeakers,

modified by the Jensen Manufacturing Divi-

sion /The Muter Company to blare out 50

times more power than those which charm

the rock 'n' roll set, will carry the quarter-

back's normal speaking voice to the farthest

split end or flanker. The tiny loudspeakers

solved the problem raised by an American

Football League ruling which prohibited the

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

Jets from using an earlier design which

used autoradio type speakers mounted in out-

board pods on the helmet.

Jensen Manufacturing, developer of the

first pocket -radio loudspeaker, was contract-

ed by Technical Materials Inc., (developers

of the helmet amplifier) to design a speaker

system which would fit inside the helmet,

and thus conform to AFL rules. Complaints

Star player of New York Jets,

Joe Namath, points to speakers'

grill. By limiting frequency

response, speakers' (3 on each

side of helmet) rating is

boosted to about 50 times output

of average transistor radio.

from parents of teenagers aside, the tiny 2-

inch speakers used in popular transistor ra-

dios aren't very loud, because they must try

to reproduce a wide range of musical tones.

Jensen engineers restricted the range of the

speakers to voice frequencies (900 -3000

cycles per second), and thus boosted their

power to about 50 times normal ratings.

The six speakers are mounted inside the hel-

met, three over each of the quarterback's

ears. Small vents permit the sound of his

amplified voice to issue freely from the hel-

met. Padded enclosures far from the helmet

webbing protect the quarterback's head from

bumping against the speakers or amplifier.

All parts of the system, including the speak-

ers, are completely waterproofed.

When he chooses to call an audible at the

line of scrimmage, the quarterback speaks

into a small microphone fastened firmly to

the inside of his face guard. A switch cuts off

the loudspeakers while signals are called in

the huddle. More than the lungs of profes-

sional football quarterbacks will be saved by

the new helmet -countless yards lost each

year when confused linemen jump off sides

will be added to the offensive might of the

Jets and other teams.

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JULY -AUGUST, 1966

www.americanradiohistory.com

16

ELECTRONICS ON WHEELS

Make a better mouse trap and sooner or later

someone is going to add electronic circuitry to

it. The automobile is no exception -electronics

is not falling behind as Detroit runs its horse-

power race. Three new products worth knowing

about can add more oomph to the family car,

increase night visibility, and bring a "toot- toot"

to those factory installed horns.

Quartz Iodine Hi- Beams. The typical sealed

beam bulb used in automobile "brights" give

23,000 cp (candle power) of light at 100 feet -

now you can get up to 65,000 cp from new re-

placement headlamps with quartz iodine ele-

ments without drilling any holes, rewiring, or

any other modifications to your car. The new

lamps are universal replacements for cars and

trucks using 53/a -inch sealed beam bulbs. Truly

a breakthrough, the iodine quartz bulbs give

three times the light of conventional units with-

out taking any extra current from the battery -

with an added plus of longer bulb life. Since the

Quartz Iodine Hi -Beams look very much like

ordinary auto seal -beam lamps until you peek of

the back -Iodine quartz light element is removable.

quartz iodine element is a separate part of the

unit, the lamp will continue to "burn" even

when the glass lens is broken -safe driving is

possible as you wheel your way home or to a

local garage. A pair of 53/4 -inch High -Beam

Headlights with Quartz Iodine Elements (No.

89 -1716) is available from J. C. Whitney & Co.

for only $19.95. A replacement element (No.

89 -1718) is ony $4.95. Send order to J. C.

Whitney & Co., 1917 Archer Avenue, Chicago,

Illinois 60616. While you are at it, ask them to

send you their latest catalog.

Fall -Safe Ignition Converter. The one thing

that has not changed on vehicles over the years

-x,

is the ignition system (the method of igniting

the gasoline by an electric spark). The Kettering

ignition system was invented in 1911 and is still

used in almost all vehicles today. Its great virtues

xrelwMMSMeeMwswYSSlWtee.

"tIKFdFT1/M9APF,f4,ANFNi IttNG Ve

Real cool transparent packaging shows the Fail -Safe

Ignition Converter to the buyer. Nothing is left

to waste. Complete installation instructions are

on back of box -comes complete with hardware.

are its reliability and simplicity. Its greatest

weakness is the fact the points will burn and

pit after just a few thousand miles of operation,

which can throw a car's entire tune -up and tim-

ing completely off. This, of course, wastes gas,

causes mis -firing and slower starting- that's if

you start at all.

Norman Industries have changed all this with

their "Fail- Safe" solid -state ignition converter.

The device converts your car's ordinary ignition

into a solid -state system -it allows the points

to make and break contact without passing the

damaging high -voltage from the coil's inductive

Long cable and terminal strip in Fail -Safe unit

permits rapid installation without special tools.

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

kick that causes the points to arc and pit. The

heart of the Fail -Safe system is a heat resistant

SCR, which is an improvement over conven-

tional transistors and capable of handling higher

currents and voltage. The payoff comes back to

the driver in better gas mileage performance,

faster cold weather starts, 50,000 miles plus on

points and an all important feature -the unit

fails safe. In the event the unit fails the ignition

system reverts back to its original design -no

getting stuck on back roads on dark nights.

Designed for 12 -volt, negative -ground sys-

tems Fail -Safe can be installed in 10 minutes.

Sells for about $29.95 at most auto accessory

stores. For more information write to Norman

Industries Incorporated, Dept. NK, 814 Diversey

Parkway, Chicago, Ill. 60614.

Electronic Two -Tooter -New Call of the Road.

The first application of electronics to produce a

distinctive new sound in auto horns has been

introduced by Kinematix, Inc. The device, called

the "Two- Tooter ", is a tiny transistorized unit

that converts the ordinary simultaneous sound

of paired auto horns to a rhythmic alternation

of the individual high and low notes. The "Two -

Tooter" is establishing a brand -new trend in

auto horns. The bright continental Paris -Rome-

Vienna flair has already captured the enthusias-

tic support of drivers everywhere, especially

among the younger set, and your car can be

equipped, too!

Measuring only 61 inches long, the converter

mounts under the hood in minutes, requiring

only four simple connections. The compact, all -

solid state circuit contains several of the latest

type of semi -conductor devices yet retails for

under $25. The complete unit, suitable for Ilse

in both 6 -volt and 12 -volt electrical systems, also

incorporates a variable repeat -speed control in-

The "Two- Tooter" is

all solid state and mounts

under the hood -anyone can do it.

side the car that enables the driver to use his

horns as a distinctive, easily recognizable salute

or an urgent warning as needed. With no mov-

ing parts and nothing to wear out, the converter

carries a full year's guarantee. Complete infor-

mation and prices on the new Kinematix "Two -

Tooter" can be obtained by writing to: Kine-

matix, Inc., 2040 Washington Boulevard, Chi-

cago, Illinois, 60612, attention of Martin J.

Santa, Director of Sales Development.

JULY -AUGUST, 1966

now there are

time & tool-saving

double duty sets

New PS88 all- screwdriver set

rounds out Xcelite's popular,

compact convertible tool set line.

Handy midgets do double duty

when slipped into remarkable

hollow "piggyback" torque ampli-

fier handle which provides the

grip, reach and power of standard

drivers. Each set in a slim,

trim, see -thru plastic pocket case,

also usable as bench stand.

PS7

2 slot tip.

2 Phillips

screwdrivers,

2 nutdrivers

PS88

5 slot tip,

3 Phillips

screwdrivers

XCELITE INC. 80 BANK ST., ORCHARD PARK, N. Y. 14127

Please send free literature N563.

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17

www.americanradiohistory.com

Order replacements for your defective tube fg a fiat $1.00 each, plus

50 postage and handl,n for your entire order. Address Dept. SE-786.

TAF'E THIS AD TO THE BACK OF YOUR TV SET

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TEST ALL RADIO and TV TUBES!

The revolutionary new home tube tester that's

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Send certified

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TRAFFIC R f0 CO

IF YOU PREFER the twang of guitar music

with bongos á la stereo when motoring -it's

yours. A stereo tape cartridge player will "sur-

round" you with music of your choice within the

confines of your car. There are no dead recep-

tion spots, as in radio, no static, no need to take

your eyes off the road to fuss with the dial, and

even a child can start and turn off the music. So

great is the cry for travel entertainment by tape

cartridge players, three major automobile manu-

facturers will include stereo cartridge players as

original equipment in 1967 cars. Reaction to car

stereo systems has been so spontaneous that the

one millionth unit will be sold early in 1967 -

and this was made possible with the development

of the tape cartridge.

How It Works. What is a tape cartridge? And

how does it work? A cartridge is a flat, small

(about 4" x 5 ") plastic container housing, on a

single reel, an endless loop of 1/4 -inch recorded

and specially lubricated audio tape -no thread-

ing or rewinding to trouble the operator. On

insertion, the tape is automatically moved by the

player's drive mechanism from the hub or inside

of the reel past the playing head and back onto

the outside of the same reel. Use of a lubricated

tape and a loose wind on the reel eliminates

friction as tape layers must constantly pass over

each other as the tape works its way toward the

hub of the reel.

TAPE SLIPS GENTLY

FROM HUB OF REEL

OPENING FOR MAGNETIC

PLAYBACK HEAD

/ IN PLAYER

TAPE WINDS PREESRAGAINSST

BACK ON REEL DRIVE CAPSTAN IN PLAYER

Redrawn from drawing made by Audio Devices, Inc.

Four -track recordings, consisting of two pairs

of stereo tracks, were the earliest type and are

still going strong -the playing time of a four -

track stereo tape is equivalent to both sides of

an LP disc. But 8 -track stereo, which has re-

quired major development in the art, doubles

playing time on the same length of tape, and is

well on the way to becoming the accepted car-

tridge. As in all stereo production, one pair of

tracks is played at a time for the full length of

the tape. The player then automatically transfers

to each succeeding pair of tracks until the re-

cording ends, and will continue to cycle (return-

ing to the first pair of tracks) until the player is

(Continued on page 107)

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

ELE

ELEMENTARY

ELECTRONICS

ETYMOLOGY

By Webb Garrison

00 ©l91 logo

Broadcast

A Perfection of instruments and methods

by which to transmit messages without use

of wires led to a sharp break in the stream

of western speech. For though Americans

called the new medium of communication

the "radio," English technicians in the field

stubbornly insisted on referring to it as the

"wireless telegraph."

Yet even the most conservative Britishers

recognized radical distinctions in the two

media. A telegraph message (at least in those

days) went to only one receiving station. A

message transmitted by wireless radiated over

a huge area and could be received by any

number of instruments simultaneously. What

to call so public an act of communication?

Centuries earlier, farmers of Britain had

used two techniques in planting. Sometimes

they carefully dropped seeds into precise

rows, drills, or holes. But when sowing grain,

turnips, and other crops they walked through

their fields casting handfuls on both sides.

Influence of the latter practice led to wide

use of the farm -born term. Orators and writ-

ers who urged political reforms took pride in

their ability to broad cast their ideas. Fused

into a single word, the hoary tern for the act

of scattering seeds or ideas at random be-

came broadcast.

Ohm

A By the mid -point of the 19th century,

research workers realized that they needed

some unit by which to measure electrical

resistance, and a name by which to speak of

it. At the 1861 meeting of the British As-

sociation for the Advancement of Science

Sir Charles Bright suggested that the term

"ohmad" be adopted. This action, he urged,

would perpetuate the name of a pioneer.

JULY -AUGUST, 1966

MODEL

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SEA ANGLER

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2G

E/E ETYMOLOGY

Georg Simon Ohm, one of the earliest

theoretical physicists to work with electricity,

produced a great volume of published work.

Only one of his reports, issued in 1827 when

he was 40, is today regarded as marking a

milestone in the progress of science. This

brief paper presents findings that throw much

light on processes that produce electricity.

"Ohmad" proved too cumbersome a verbal

memorial to the German experimenter. But

clipped to the form of his surname, it soon

entered the international vocabulary of sci-

ence. By edict of Queen Victoria, the ohm

was legally defined as "the resistance to an

invariable electric current by a column of

mercury at the temperature of melting ice,

14.4521 grammes in mass, of a constant

cross -sectional area, and a length of 106.3

centimetres." Methods of measurement have

been greatly refined, but the name of Georg

Ohm remains basic to the vocabulary of

electronics.

Feedback

A No one knows exactly when or how radio

operators discovered that circuits can be

coupled in such fashion that part of the

energy in one is transferred to the other. In-

stead of being the fruit of costly professional

research, this was probably the result of ran-

dom experiments by amateurs.

At first it was considered interesting but

not especially important that one can feed

back current in this fashion. Important prac-

tical applications were soon discovered, how-

ever, and deliberate use of feed -back tech-

niques was coming into vogue before the end

of World War I.

Already, operators of public address sys-

tems and radios had observed that under

some conditions part of a system's output is

returned to it. It was logical to extend the

use of "feedback" to name such processes

as well as those operating by linked circuits.

Refinement of electronic amplifying sys-

tems led to recognition that feedback can in-

crease volume, decrease it, or reduce quality

of control.

Jumping from electronics into general

speech, the term came to name any return to

input of part of the output of a system,

machine, or process. Now used in such

diverse fields as biology and economics, feed-

back is a basic concept in cybernetics.

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

BY JOHN W. COLLINS

Chess columns are beginning to appear in the

most unexpected places - literary magazines,

medical magazines, religious newspapers. And

now in this electronics magazine. All to the

good, chess being, among other things, an art, an

anodyne, a way of life and a discipline. Always

eager to spread the gospel of the Royal Game,

I was delighted to accept Editor Julian Sienkie-

wicz's offer of a column in ELEMENTARY ELEC-

TRONICS. We both believe that many of those

interested in electronics are also interested in

chess. His vision and imagination are admirable.

I hope the readers who play the game will derive

enjoyment and instruction from the columns and

1 hope the ones who are unfamiliar with it will

be enticed into learning.

En Passant will appear in every issue of ELE-

MENTARY ELECTRONICS. It will present book re-

views, games, endgame studies, instruction, news

and two move problems. It will look at the

game, in its various forms, here at home and

abroad, and at its past and present.

News and Views. Grandmaster Robert (Bob-

by) J. Fischer of Brooklyn, a former prodigy

now 23, won the U. S. Championship (for the

seventh time!) last December in New York. He

scored 8t /2 -21/2, losing to R. Byrne and S. Re-

shevsky and drawing with W. Addison. In 1964,

in a somewhat weaker field, he swept the boards

11 -0. World Champion Tigran Petrosian and chal-

lenger Boris Spassky, both of the U.S.S.R., will

meet in a twenty -four game match for the world

title beginning sometime in April in Russia.

The second Piatigorsky Cup Tournament will

be played in Santa Monica, California, during

July- August. Eight leading grandmasters (prob-

ably including Fischer and Petrosian) will com-

pete for the $3,000 first prize. Gregor Piatigor-

sky is a world famous cellist and his wife Jacque-

line, a former Rothchild, is a top woman chess -

player and a patron of the arts.

Lombardy Wins. Grandmaster William Lom-

bardy of New York, a siminarian at St. Joseph's,

won the Western Open in St. Louis last July with

JULY -AUGUST, 1966

The June /July issue of Radio -TV Experimenter,

now at your newsstand, has a number of construc-

tion projects that most anyone can build from our

instructions.

One such project is an Audio Compressor that will

be of special interest to amateurs and CB'ers; the

other is a neon -bulb calculator that does simple

multiplication and is an excellent Science Fair proj-

ect.

These are just a few of the editorial features that

can be found in this issue -but typical of the fas-

cinating reading of interest to everyone, that can

always be found in each issue of RADIO -TV

EXPERIMENTER. Subscribe today.

RADIO -TV EXPERIMENTER EE793

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

Begin my subscription to RADIO -TV EXPERIMENTER

with the August September issue. Enclosed is $4.00 for

1 yr; $7.00 for 2 yrs; Bill me. (Foreign: add 75g a yr.)

Name .... ............................... (please print)

City ..

ELEMENTARY

ELECTRONICS

Tells You Why And How

If you have only a passing interest in electronics, or

on the other hand, if you have a sincere desire to

make electronics your career, either way ELEMEN-

TARY ELECTRONICS has to be "must" reading.

For ELEMENTARY ELECTRONICS is instructional in

nature -it teaches in easy -to- understand language

the basics of electronics -no matter what the subject.

And as electronics and its many by- products becomes

more and more a way -of -life, the need to acquire an

understanding of this fascinating subject becomes

even more important.

And the best way to begin to understand electronics

is through the exciting and stimulating pages of

ELEMENTARY ELECTRONICS.

ELEMENTARY ELECTRONICS EE 793

505 Park Avenue / New York. New York / 10022

Begin my subscription to ELEMENTARY ELECTRONICS with the next

issue. I am enclosing $4.00 for 1 yr.; $7.00 for 2 yrs.;

$10.00 for 3 yrs. (foreign; add 7n a year).

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EN PASSANT

a score of 8 -1 (7 wins and 2 draws). Directed

by a woman, Pearl Mann, the event had 143

entries. One of Lombardy's cleverest wins was

from Bill Bills of Houston, Texas. The opening

was a Caro -Kann Defense, Two Knights' Varia-

tion and was a 14 move miniature which went

like this-

1. P-K4 P-0B3 8. NxB

2. N-0B3 P-Q4 9. P-B3 QxN

3. N-B3 PxP 10. 0-N3 O-O?

4. NxP P-KN3? 11. QxP! ON-02

5. P-04 B-N2 12. B-K2 0-K5

6. P-KR3 B-B4 13. 0-R6 P-B4

7. N-N3 N-B3 14. N-N5! Resigns

Position after 14 N -N5!

Why did Black resign? Because he is already

a Pawn behind, he must lose either his Queen,-

a piece, the exchange (Rook for Bishop) and

because he knows he is playing a Grandmaster!

Here is the analysis -

A. If 14 ... Q -B7 15 B -Q3, N -N1 16 Q -B4

and the Black Queen is lost.

B. If 14 ... Q -B4 15 P -KN4, Q -Q4 16

B -B3, Q -Q3 17 QxQ, PxQ 18 BxR and White

has won the exchange.

C. If 14 ... QxNP 15 B -B3, N -N1 16 Q -N7

and the Black Queen is lost.

D. If 14 ... Q -Q4 15 B -B3 wins the ex-

change.

E. 14 ... Q -R5 15 P -KN3, Q -R3 16 NxBP

and White wins the Queen for Bishop and

Knight.

F. 14 ... N -NI 15 NxQ, NxQ 16 NxN#

BxN 17 BxN, PxP 18 PxP, BxP 19 0 -0 and

White is a whole piece ahead.

There is an old saw among chessplayers which

warns "never take the Queen Knight Pawn!" (it

loses too much time). Lombardy exploded that

myth in this one!

Problem. Many are the ways to enjoy chess.

One is solving problems -the poesy of the game.

22

I shall give a two mover in every column, some-

times an old classic and sometimes a new orig-

inal. This first one dates to 1938, has a cross-

check theme and earned First Prize for a great

American Composer.

Problem 1.

By F. Gainage

Black

41

4 V4 II

ELL) 1

A

White

White to move and mate in two.

Solution in next issue.

Learn by Reading. A number of excellent

books are available to those who want to learn

to play chess. I recommend "An Inviation to

Chess" by Irving Chernev and Kenneth Hark-

ness. It is specifically designed for persons who

do not know one chess piece from another and

its approach is visual, pictorial, with photo-

graphs and diagrams. It has 221 pages, is pub-

lished by Simon and Schuster and costs about

$3.50.

About Our Columnist. Who is John W. Collins?

Well, he is a former U. S. Correspondence Champion,

New York State Champion, Marshall Chess Club Cham-

pion, Hawthorne Chess Club Champion and Brooklyn

Chess Club Champion. He has been secretary of the

Brooklyn Chess League and the Metropolitan Chess

League. He teaches the game privately and by corre-

spondence and he has been the early teacher- mentor

of U. S. Champion Bobby Fischer, Grandmasters W.

Lombardy, R. Byrne and D. Byrne, Senior Master R.

Weinstein and is now teaching a fourteen year old

rising star, Sal Matera. He was co- reviser of Modern

Chess Openings, 9th Edition, the so- called "chess -

player's bible." And currently he has land has had

for several years) columns in Chess Review (Postal

Games and Book of the Month) and Chess Life, offi-

cial publication of the United States Chess Federation

(GAMES By USCF Members) and is a member of the

Manhattan Chess Club, oldest and foremost in the

country. The Editors of ELEMENTARY ELECTRONICS

welcome John to the staff and we are privileged to

have him work with us.

Cartoon by Cork

ELEMENTARY ELECTRONICS

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To have a firm foundation, build

your knowledge of electronics theory

with a basic building block -the atom

Electricity,

Magnetism

and the

Atom Prepared by the

Editors of

Elementary Electronics

One of the most thought provoking dis-

coveries of modern physics is the fact that

matter and energy are interchangeable. Cen-

turies of scientific head -scratching about the

nature of matter, the mystery of fire, and the

once -terrifying crack of lightning have all

come to focus on the smallest particle that is

the building block of any given substance:

the atom. An atom is necessarily matter and

yet this atom of matter can undergo nuclear

fission and release quantities of energy that

are beyond the imagination. In the atom lies

the secret of all phenomena. One theory of

the universe, hypothesized by Georges Le-

maitre, even regards the present universe as

resulting from the radioactive disintegration

of one primeval atom!

A Monumental Discovery. By the begin-

ning of the 19th century, the atomic theory

of matter -which actually originated in 5th

century Greece when the atom was named

-was firmly established. It was due primar-

ily to the efforts of 17th century scientists

who -actually working in the tradition of

medieval alchemy- sought the prime con-

stituent of all matter. Mainly through the

work of John Dalton, whose investigations

as to how various elements combine to form

chemical compounds, it came to be regarded

that an atom was the indivisible and inde-

structible unit of matter.

This viable and working view of the inde-

structible atom served science until 1897

JULY -AUGUST, 1966

when the atom itself was found to be de-

structible! To anyone concerned with elec-

tricity or electronics, the year 1897 is a

memorable one: it was the year J. J. Thom-

son, the English physicist, identified and ex-

perimentally revealed the existence of the

first subatomic particle -the electron!

The First "Electronic" Experiment. We

blithely speak of electricity as the flow of

electrons yet, often, we are little aware of the

great body of research that went into eluci-

dating this fundamental of basic electricity.

In fact, before the discovery of the electron,

convention held that the flow of electric cur-

rent was in the direction that a positive

charge moved. This convention of positive

current, being the flow of positive charges

and opposite to the direction of electron flow,

is still found to be useful in circuit analysis

and is used even today.

Thomson's experiment established that a

particle much lighter than the lightest atom

did indeed exist. The electron, as it was

named, was the first subatomic particle to

be defined.

The experiment was conducted utilizing a

rudimentary version of a cathode ray tube -

the modern version of which is in almost

every home today in the form of the tele-

vision picture tube. Before Thomson's experi-

ment, it was discovered that when electric

current was passed through a gas in a dis-

charge tube, a beam of unknown nature

23

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ELECTRICITY, MAGNETISM

AND THE ATOM

traveled through the tube from the negative

to positive terminal (opposite to the direc-

tion conventionally held as the direction of

the flow of current) .

This "cathode ray" beam also traveled in

a straight line and was deflected by electric

or magnetic forces applied perpendicular to

the beam. What Thompson did was to use

these facts to determine for one of the mys-

terious particles comprising the beam of

cathode rays the relationship of its mass, m,

to its electric charge, e. By deflecting the

beam with a known electric force (Fig. 1)

MAGNETIC FIELD

DEFLECTION

( +1

UNDEFLECTED

POSITION

ELECTRIC FIELD

DEFLECTION -

24

Fig. 1. Electron beam, like that in a TV picture tube

(CRT), can be deflected magnetically or by an elec-

tric Held. Force needed "measured" the electron.

and then measuring what magnetic force

applied in the opposite direction would bring

the beam back to its original undeflected po-

sition, he could determine the relationship

of e to m. He established a definite value for

elm and thereby "discovered" the electron

which, as we now know, is 1,837 times

smaller in mass than the lightest atom, the

hydrogen atom. It also carries the smallest

charge that occurs in nature; every electric

charge is actually an integral multiple of the

charge of the electron.

From Minus to Plus. With the discovery

of the electron, it was still over a dozen years

into the 20th century before a graphic con-

ception of the atom evolved. Since the atom

is electrically neutral and electrons are nega-

tively charged, the existence of positively

charged particles was a necessity, and the

existence of a proton was postulated. Eventu-

ally the nuclear model of the attain was

evolved. Each atom was conceived to re-

semble a solar system in miniature. The

nucleus -positively charged -is surrounded

by a number of electrons revolving around it;

the charges balance and the atom is electri-

cally neutral (Fig. 2). Further research in

the 20th century has gone on to reveal more

elementary particles than you can shake a

Fig. 2. Charge of each electron bal-

ances that of a proton. Other par-

ticles affect atomic mass but can

be ignored in study of electronics.

stick at: neutrons, positrons, neutrinos, me-

sons, and more. The number continues to

grow and yet the ultimate nature of- matter

remains a riddle. But, in a discussion of basic

electricity, only the electron and proton need

concern us.

Electrons in Orbit. An atom of matter has

a number of electrons orbiting around its

nucleus. A hydrogen atom, for example, has

a single electron; carbon on the other hand

has 6. These electrons are arranged in rings

or shells around the central nucleus -each

ring having a definite maximum capacity of

electrons which it can retain. For example,

in the copper atom shown in Fig. 3 the maxi-

mum number of electrons that can exist in

Fig. 3. The number of electrons to

each ring are limited -2 in first; 8

in second; 18 for the third and a

total of 32 in fourth orbital ring.

the first ring (the ring nearest the nucleus)

is two. The next ring can have a maximum of

eight, the third ring a maximum of 18, and

the fourth ring a maximum of 32. However,

the outer ring or shell of electrons for any

atom cannot exceed eight electrons. How-

ever, heavier atoms may have more than four

rings. The Outer Orbit. The ring of electrons

furthest from the atom's nucleus is known as

the valence ring and the electrons orbiting in

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

this ring are known as valence electrons.

These valence electrons, being further from

the nucleus, are not held as tightly in their

orbits as electrons in the inner rings and can

therefore be fairly easily dislodged by an

external force such as heat, light, friction,

and electrical potential. The fewer electrons

in the valence ring of an atom, the less these

electrons are bound to the central nucleus.

As an example, the copper atom has only

one electron in its valence ring. Consequent-

ly, it can be easily removed by the applica-

tion of only the slightest amount of external

energy. Ordinary room temperature is suf-

ficient to dislodge large numbers of electrons

from copper atoms; these electrons circulate

about as free electrons. It is because of these

large numbers of free electrons that copper is

such a good electrical conductor. There

could be no electrical or electronics industry

as we know it today if it were not for the

fact that electrons can fairly easily escape,

or be stripped from the valence ring of cer-

tain elements.

METAL ROD

INSULATOR Fig. 4. Electroscope is a

simple device to indicate

electrical charges that

are too weak to be meas-

ured with standard meters.

Electronic Charges. If an electron is

stripped from an atom, the atom will assume

a positive charge because the number of posi-

tively charged protons in its nucleus now

exceed the number of negatively charged

orbiting electrons. If, on the other hand, the

atom should gain an electron, it will become

negatively charged as the number of elec-

trons now exceeds the protons in its nucleus.

The atom with the deficiency of electrons is

known as a positive ion, while an atom with

a surplus of electrons is known as a negative

ion. Presence of an electrical charge on a body

can be illustrated by use of an electroscope

(Fig. 4). Two leaves of aluminum or gold

foil hang from a metal rod inside a glass

case so they're free from air disturbances.

When the meal rod is touched by a charged

body, the leaves acquire static electricity of

the same polarity and, since like charges

repel, they stand apart. The greater the

charge, the further apart the leaves spread.

Electron Flow. When an electrical con-

ductor is placed between these two oppositely

JULY -AUGUST, 1966

charged bodies, free electrons are attracted

by the positive body -free electrons will

move through the wire. This movement of

free electrons will continue only until the

excess of electrons is equally divided be-

tween the two bodies. Under these condi-

tions, the charges on both bodies will be

equal and the electron flow will end.

Fig. 5. Electron flow in

any circuit is from neg-

ative to positive - this

is opposite to current,

which flows from positive

toward negative terminal.

In Fig. 5 are a battery, lamp and connect-

ing leads between the battery and lamp. In

this instance, the battery serves as an electric

charge pump -free electrons continually de-

veloped at its negative terminal by chemical

action flow through the connecting leads and

lamp back to the positive terminal of the

battery by the attraction of oppositely

charged bodies. The battery, connecting

leads, and lamp form an electrical circuit

which must be complete before the free elec-

trons can flow from the battery's negative

terminal to its positive terminal via the lamp.

Thus, the battery serves as a source of po-

tential difference or voltage by continually

supplying a surplus of electrons at its nega-

tive terminal. Summing up, we can say a flow

of electric current consists of the movement

of electrons between two oppositely charged

bodies.

We cannot progress very far into the study

of electricity without first becoming familiar

with the basic properties of electrical circuits.

Just as we define distance in feet and inches,

so do we define electrical properties in spe-

cific terms and units.

Potential. Earlier, we saw that an elec-

tric charge difference has to exist between the

ends of an electrical conductor in order to

cause a flow of free electrons through the

conductor. This flow of electrons constitutes

the electric current. The electric charge dif-

ference, or potential difference exerts a force

on the flow of free electrons, forcing them

through the conductor. This electric force or

pressure is referred to as electromotive force,

abbreviated EMF.

The greater the charge or potential differ-

ence, the greater will be the movement of

free electrons (current) through the conduc-

tor as there will be more "push and pull" on

the free electrons. The symbol used to desig-

nate electrical potential is the letter E which

25

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ELECTRICITY, MAGNETISM

AND THE ATOM

stands for electromotive force. The quantity

of EMF is measured by a unit called the volt.

Hence, the common name most often used

in place of EMF is voltage.

Current Intensity. We have learned that

an electric current consists of a flow of

charge carrriers (generally free electrons)

between two points of different electrical

potential. The rate of flow of these charges

determines the intensity or strength of this

current flow. Current strength is expressed

in units known as amperes. One ampere of

current flows in a circuit when 6,240,000,000

electrons flow out of a negative terminal,

through a conductor, and back into a pos-

itive terminal in one second. The symbol

for the ampere is the letter I which stands

for intensity.

Resistance. The flow of electric current

through a conductor is caused by the move-

ment of free electrons present in the atoms

of the conductor. A bit of thought then indi-

cates that the greater the number of free elec-

trons present in the atoms of a particular

conductor, the greater will be its electrical

cqnductivity. Gold, silver, and copper rank

as excellent electrical conductors as their

atoms readily release free electrons. On the

other hand, the atoms of such elements as

sulphur have almost no free electrons avail-

able and they are thus very poor electrical

conductors. Such materials are known as

electrical insulators. Between these extremes,

lie elements such as carbon whose atoms

have a moderate number of free electrons

available and thus are moderately good

electrical conductors.

Even the best electrical conductors offer

some opposition to the passage of free elec-

trons. This opposition is called resistance.

You might consider electrical resistance simi-

lar to mechanical friction. As in the case of

mechanical friction, electrical resistance gen-

erates heat. When current flows through a

resistance, heat is generated; the greater the

current flow, the greater the heat. Also, for

a given current flow, the greater the resist-

ance, the greater the heat produced.

Electrical resistance can be both beneficial

and undesirable. Toasters, electric irons, etc.

all make use of the heat generated by current

flowing through wire coils. Resistance is also

often intentionally added to an electrical cir-

26

cult to limit the flow of current. This type of

resistance is generally lumped together in a

single unit known as a resistor.

There are also instances where resistance

is undesirable. Excessive resistance in the

connecting leads of an electrical circuit can

cause both heating and electrical loss. The

heating, if sufficient can cause a fire hazard,

particularly in house wiring, and the circuit

losses are a waste of electrical power.

Electrical resistance is expressed by a unit

known as the ohm, indicated by the letter R.

An electrical conductor has a resistance of

one ohm when an applied EMF of one volt

causes a current of one ampere to flow

through it.

Resistance Factors. There are other

factors beside the composition of the materi-

al that determine its resistance. For example,

temperature has an effect on the resistance of

a conductor. As the temperature of copper

increases, for example, its resistance in-

creases. The increase in temperature causes

the electrons in the outer ring of the atom to

resist release to the free electron state. This

increase in resistance with an increase in

temperature is known as a positive tempera-

ture coefficient. Not all conductors show

this increase in resistance with an increase

in temperature; their resistance decreases

with an increase in temperature. Such ma-

terials are said to have a negative tempera-

ture coefficient. Certain metallic alloys have

been developed which exhibit a zero temper-

ature coefficient: their resistance does not

change with changes in temperature.

As you might suspect, the length of a con-

ductor has an effect upon its resistance. Dou-

bling the length of a conductor will double

its resistance. By the same token, halving the

length of a conductor will cut its resistance

in half. Just remember that the resistance of

a conductor is directly proportional to its

length.

The cross -sectional area of a conductor

also determines its resistance. As you double

the cross -section of a conductor, you halve

its resistance; halving its cross -section doubles

its resistance. Here again, the "why" of this

is pretty easy to see: there are more current

carrying electrons available in a large cross -

section conductor than in a small cross -sec-

tion conductor of the same length. There-

fore, the resistance of a conductor is inversely

proportional to its cross -sectional area.

Circuit Relationship. Now that we have a

basic understanding of voltage, current, and

resistance, let's take a look at just how they

ELEMENTARY ELECTRONICS

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A

= BATTERY

4VDC RESISTOR

1n

AMMETER

= BATTERY

= 8VDC RESISTOR

In.

C:. AMMETER

= BATTERY

2VDC RESISTOR

In

Fig. 6. In A, B and C,

(above left) the value

of the resistor remains

constant while the sup-

ply voltage is raised and

then lowered with a re-

sulting current change.

0

AMMETER

.BATTERY

= 4VDC RESISTOR

In.

B 8

AMMETER

= BATTERY

. 4VDC RESISTOR

1/2n

C

+

BATTERY

. 4VDC RESISTOR

2n

AMMETER

Fig. 7. Battery voltage

in A, B and C (above) is

held constant while re-

sistor is halved and dou-

bled in value. Resulting

current increase, decrease

are basis for Ohm's law.

interact under circuit conditions.

Fig. 6A shows a battery, ammeter (a de-

vice to indicate current strength), and re-

sistor connected in series. Notice that the

ammeter indicates that 4 amperes are flowing

in the circuit.

Fig. 6B shows the identical setup with the

exception that the battery voltage has now

been doubled. The ammeter now shows that

twice the original current, or 8 amperes, are

now flowing in the circuit. Therefore, we

can see that doubling the voltage applied to

the circuit will double the current flowing in

the circuit.

In Fig. 6C the same circuit appears again;

this time, however, the battery voltage is one -

half its original value. The ammeter shows

that one -half of the original current or 2

amperes, are now flowing in the circuit. This

shows us that halving the voltage applied to

the circuit will halve the current flowing

through the circuit.

All this boils down to the fact that assum-

ing the same circuit resistance in all cases,

the current flowing in a circuit will be direct-

ly proportional to the applied voltage -in-

creasing as the voltage is increased, and de-

creasing as the applied voltage is decreased.

In Fig. 7A we again see the circuit con-

sisting of the battery, ammeter, and resist-

ance. Notice that the ammeter indicates that

4 amperes are flowing through the circuit.

JULY- AUGUST, 1966

In Fig. 7B we see that the value of re-

sistance has been cut in half and as a result,

the ammeter indicates that twice the original

current, or 8 amperes, is now flowing in the

circuit. This leads us to the correct assump-

tion that for a given supply voltage, halving

the circuit resistance will double the current

flowing in the circuit.

Fig. 7C again shows our basic circuit, but

with the resistance now doubled from its

original value. The ammeter indicates that

the current in the circuit is now one -half of

its original value.

Summing things up: for a given supply

voltage, the current flowing in a circuit will

be inversely proportional to the resistance in

the circuit.

Ohm's Law. From what you have seen so

far, you are probably getting the idea that

you can determine the current flowing in a

circuit if you know the voltage and resistance

present in the circuit, and the voltage if you

know the current and resistance, or the re-

sistance if the voltage and current are known.

All this is quite correct, and is formally

stated by Ohm's Law as follows:

E

I - R

Where: E = voltage

I = current

R = resistance

Now, let's take a look at how this formula is

used:

To find voltage:

E (voltage) = I (current) x R (resistance)

To find current...

E (voltage)

I (current) = R (resistance)

To find resistance:

E (voltage)

R (resistance) _ I (current)

A handy way to remember Ohm's Law is

by means of the triangle shown in Fig. 8.

Simply cover the quantity (voltage, current,

or resistance) that you want to determine,

and read the correct relationship of the re-

maining two quantities. For example, if you

27

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ELECTRICITY, MAGNETISM

AND THE ATOM

Fig. 8. Shaded portion of triangle

indicates unknown quantity in the

formula. Visible factors appear in

their proper mathematical relation.

Just fill in the known values and go

on with multiplication or division

want to know the correct current (I), put

E

your finger over I and read -. Covering

R

E

E or R will yield I x R or -, respectively.

I

E=IR R= E

200 OHMS

T VOLTAGE UNKNOWN

0.5 AMPERE

Fig. 9. Unknown quantity,

voltage, found easily by

applying Ohm's law. Us-

ing known factors (ohms

and amperes) in a simple

multiplication process

the voltage is calculated.

Ohm's Law to Determine Voltage. Let's

delve a bit more deeply into Ohm's law by

applying it to a few cases where we want to

determine the unknown voltage in an elec-

trical circuit. Take a look at Fig. 9, which

shows a simple series circuit consisting of a

battery and resistor. The value of this resistor

is given as 200 ohms, and 0.5 ampere of

current is flowing through the circuit. We

want to find the value of battery voltage.

This is easily done by applying Ohm's law

for voltage as follows:

E=IxR

E (unknown voltage) = 0.5 (current in am-

peres) x 200 (resistance in ohms) = 100 V.

Let's go through this again, this time using

a practical illustration. Fig. 10 shows a string

r400 OHMS

I ^I

U." ü 4.1-

}

UNKNOWN

VOLTAGE

f 0.3 AMPERE

Fig. 10. Although prob-

lem looks different the

basic circuit is same as

that for Fig. 9. Putting

triangles in Fig. 8 to

use is simplest, easiest

way to determine formula.

of light bulbs, the total resistance of which

is 400 ohms. You find that the bulbs draw

0.3 amperes when lighted. Let's say you

would like to operate this string of bulbs

from the standard 120 -volt house current, but

you don't know the voltage rating of the indi-

vidual bulbs. By using Ohm's law for voltage,

you can easily determine the voltage to light

28

the bulbs as follows: E (unknown voltage)

= 0.3 (amperes) x 400 (bulb resistance) _

120 volts.

Ohm's Law to Determine Current. Now,

let's take a look at a few examples of how

5 OHMS

20VDC

JUNKNOWN CURRENT

Fig. 11. Formula needed

here is different since

current is unknown. Just

look for triangle in Fig.

8 that has I shaded and

substitute values for E

and R - simple division.

to determine the value of unknown current

in a circuit in which both the voltage and

resistance are known.

Fig. 11 shows a series circuit with a bat-

tery and resistor. The battery voltage is 20

volts DC and the value of resistance is 5

ohms. How much current is flowing through

the circuit?

Ohm's law for current I - E

R

20 (battery voltage)

I (unknown current) - 5 (resistance in ohms)

I = 4 amperes

Again to get a bit more practical, let's take

Fig. 12. Basic circuit is

same as that in Fig. 11.

Although three factors

are given, current is un-

known quantity because

120 the problem is to decide

proper rating for fuse.

a look at Fig. 12. Here we see an electric

heater element connected to the 120 -volt

house line. We know that this particular

heater element has a resistance of 20 ohms.

The house current line is fused with a 15-

ampere fuse. We want to know whether the

heater will draw sufficient current to blow

the fuse. Here's how to find this out by use

of Ohm's law for current.

15 AMP FUSE _

ELECTRIC

HEATER -h

(20 OHMS) I

L__J

ELEMENTARY ELECTRONICS

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120 (line voltage)

I (unknown current) - 20 (Heater resist-

ance in ohms)

I = 6 amperes

We find from the above use of Ohm's law

for current that the heater draws 6 amperes,

so it can be safely used on the line fused with

the 15 ampere fuse. In fact, a 10 ampere

fused line can also do the job.

Ohm's Law to Determine Resistance.

Ohm's law for resistance enables us to deter-

mine the unknown value of resistance in a

circuit. Fig. 13 again shows a simple series

UNKNOWN RESISTANCE

= 20VDC

0.5 AMPERE

Fig. 13. Most Ohm's law

problems are simple se-

ries circuits or can be re-

duced fo simple series

circuits and then solved

using the formula with

known values substituted.

circuit with the battery voltage given as 20

volts and the current flowing through the

circuit as 0.5 ampere. The unknown resist-

ance value in this circuit is found as follows:

Ohm's law for resistance R = E

I

20 (battery

voltage)

R (unknown resistance) - 0.5 (current

in amperes)

R =40 ohms

Fig. 14 is a practical example of how to

determine unknown resistance. Here, we

120

VOLTS

DROPPING

RESISTANCE

UNKNOWN

6 -VOLT

BULB

0.2 AMPERE

Fig. 14. This Ohm's law

problem is somewhat

more complex since drop-

ping resistance must take

care of voltage, from

source, not needed by 6-

volt bulb in circuit.

want to operate a 6 -volt light bulb from the

120 -volt house line. What value of series

dropping resistor do we need to drop the

120 -volt house current down to 6 volts? The

bulb draws 0.2 ampere.

We must first determine the voltage which

must be dropped across the series dropping

resistor. This is done by subtracting the line

voltage (120) from the bulb's voltage (6).

This gives us a value of 114 volts which we

JULY- AUGUST, 1966

use in conjunction with Ohm's law for re-

sistance as follows:

R (unknown resistance) -

114 (voltage

dropped by

resistor)

0.2 (bulb

current in

amperes)

R = 570 ohms

Resistance in Series. Many practical

electrical and electronic circuits use two or

more resistances connected in series. The

point to remember in this case is that the

total resistance is the sum of the individual

resistances. This is expressed by the formula:

R (total resistance) = RI + R2 + R3 + etc.

where R1, R2, R3, etc. are the individual

40A

5n 10n

Fig. 15. Resistances in series are

added. As far as voltage applied

and current flow is concerned the

individual resistors are only one.

Fig. 16. Resistors in parallel are

added algebraically - the result

will always be a value less than

that of the lowest in the circuit.

resistances. Thus, in Fig. 15 the total of the

individual resistances is R (total) = 40 + 6

+ 10 + 5 = 61 ohms.

Resistances may also be connected in par-

allel in a circuit as in Fig. 16. In this case the

current flowing in the circuit will divide be-

tween the resistances, the greater current

flowing through the lowest resistance. Also,

the total resistance in the circuit will always

be less than the smallest resistance since the

total current is greater than the current in any

of the individual resistors. The formula for

determining the combined resistance of the

two resistors is:

R1 X R2

R (total) - R1 + R2

29

www.americanradiohistory.com

30

ELECTRICITY, MAGNETISM

AND THE ATOM

1 1 1 1 1

--+-+-+...-

R R1 R2 R3 Rn

Quite often an electronic circuit will con -

Thus, in Fig. 16 the effective resistance of tain a combination of series and parallel re-

R1 and R2 is:

2X4 8

R (total) = = or 1.33 ohms.

2 +4 6

In a circuit containing more than two

parallel resistors as in Fig. 17 the easiest

way to determine the total circuit resistance

is as follows: first, assume that a 6 -volt

battery is connected across the resistor net-

work. Pick a value that will make your

computations simple. Then determine the

current flowing through each of the resistors

using Ohm's law.

6 OHMS

Fig. 17. Ohm's law can be used to

determine the equivalent resistance

of two or more resistors in parallel.

Total current -then solve for ohms.

E 6

I = -= - = 3 amperes

R1 2

E 6

I = - = - = 2 amperes

R2 3

E 6

I = - = - = 1 ampere

R3 6

Next, add the individual currents flowing

through the circuit:

2 amperes + 3 ampci-es + 1 ampere

I = 6 amperes

Inserting this 6 amperes in Ohm's law, the

total circuit resistance is found to be:

6

R=-=1ohm

6

The combined equation for determining

the total resistance of n number of resistances

would be:

Fig. 18. Series- parallel circuit is

not really difficult. Add R2 and R3

algebraically. Add effective re-

sistance to R1 for total resistance.

sistances as in Fig. 18. To solve this type

of problem, first determine the combined

resistance of R2 and R3:

6 X 12 72

R (total) _ - = 4 ohms

6+ 12 18

This total value of R2 and R3 may be con-

sidered a single resistance which is in series

with R1, and forms a simple series circuit.

This simple series circuit is solved as follows:

R (total) = 6 + 4 or a total of 10 ohms.

Power. The amount of work done by elec-

tricity is termed the watt and one watt is

equal to one volt multipled by one ampere.

This may be expressed as: P = E x I where

E = voltage in volts, 1 = the current in

amperes. Also:

E2

P = and P = 12R

R

As an example, assume that a toaster draws

5 amperes at an applied voltage of 115 volts.

Its wattage would then be:

P = 115 x 5 or 575 watts.

Magnetism and the Electron. The atom,

and a concept of its structure were a neces-

sary preface to our discussion of basic

electricity. By the same token, both are nec-

essary to understanding basic magnetism.

As we've mentioned, electrons are in con-

tinual motion about the nucleus. The orbit is,

in fact, a small loop of current and has a mag-

netic field that's associated with a current

loop. In addition, experimental and theo-

retical investigation seems to indicate that

the electron itself has a spin. Each electron,

having its own axis, is a spinning sphere of

ELEMENTARY ELECTRONICS

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electric charge. Electron spin, like the quan-

tum and wave theories of light, is not so

much a literal jnterpretation of a phenom-

enon, but a useful concept that holds water

when applied to the phenomenon of mag-

netism.

When the electron spins, the charge that is

in motion produces a magnetic field. And, to

briefly state the electronic explanation of

magnetism, it seems that the magnetic prop-

erties of matter can be attributed to the

orbital and spinning motion of the electrons

comprising the atoms of the matter.

Millennia of Magnetism. Some of the

basic principles and effects of magnetism

have been known for centuries. The Greeks

are credited as the ones who first discovered

magnetism. They noted that a certain type of

rock had the ability of attracting iron. Later,

the Chinese noted that an elongated piece of

this rock had the useful property of always

pointing in a North -South direction when

suspended by a string. This was the beginning

of our compass.

This strange stone which intrigued people

over the centuries is actually a form of iron

ore known as magnetite. Not all magnetite

shows magnetic properties. Another name

for the magnetic variety of magnetite is lode-

stone -the term lodestone being derived from

two separate words, lode and stone. The term

lode stands for guide, hence lodestone mean

"guide stone."

All magnets, whether natural or man

made, possess magnetic poles, which are com-

monly known as the magnet's north and

south poles. As is the case of the electrical

charges (which we studied earlier) between

unlike magnetic poles and repulsion between

like poles, it has been found that this mag-

netic attraction and repulsion force varies in-

versely as the square of the distance from the

magnetic poles.

The Magnetic Field. We all know how

a magnet exerts a force of attraction on a

piece of magnetic material such as iron or

Fig. 19. Lines of force around bar

magnet can be made visible by

sprinkling iron filings onto white pa-

per over magnet. Tap paper gently.

JULY- AUGUST, 1966

steel. Also, when the north poles of two

magnets are brought close together, they will

try to repel each other, while there will be

attraction between the north and south poles

of two magnets. Although it is not clearly

understood just what this force of magnetic

attraction and repulsion is, it is convenient

to visualize magnetic lines of force which

extend outward from one magnetic pole to

the other as illustrated in Fig. 19.

Permeability. Magnetic lines of force can

pass through various materials with varying

ease. Iron and steel, for example, offer little

resistance to magnetic lines of force. It is

because of this that these materials are so

readily attracted by magnets. On the other

hand, materials such as wood, aluminum and

brass do not concentrate or encourage the

passage of magnetic lines of force, and as a

consequence are not attracted by magnets.

The amount of attraction a material offers

to magnetic lines of force is known as its

permeability. Iron and steel, for example,

possess high permeability since they offer

CURRENT

DIRECTION

DIRECT ON OF

MAGNETIC FLUX CURRENT

DIRECTION

Fig. 20. Direction of flux lines is

changed by direction of the current.

Heavy current is needed to make flux

lines visible with sprinkled filings.

little resistance to magnetic lines of force.

Nonmagnetic materials have low permeabil-

ity. For practical purposes, we can say that

reluctance is to magnetic lines of force what

resistance is to an electrical current.

Electromagnetism. Any electrical con-

ductor through which flows an electrical cur-

rent will generate a magnetic field about it

which is perpendicular to its axis as shown in

Fig. 20. The direction of this field is depend-

ent upon the direction of current flow, and

the magnetic field strength proportional to

the current strength. If this current -carrying

conductor is wound into a coil, forming a

solenoid, the magnetic field will be increased

by each individual turn that is added. If

an iron core is inserted in this current carry-

ing coil, the generated field will be increased

still further. This is because the lines of

force are concentrated within the iron core

which has considerably less reluctance than

the surrounding air.

31

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@/@ ELECTRICITY, MAGNETISM

AND THE ATOM

The magnetizing power of a multi -turn

current- carrying coil through which a core

is inserted is proportional to the current

flowing through the coil as well as the num-

ber of turns in the coil. The current through

the coil is termed ampere turns. As an ex-

ample, if a coil consisting of 200 turns is

carrying 2 amperes, its ampere turns equal:

Ampere turns = 200 turns x 2 amperes or

400 ampere turns

Similarly a coil of 100 turns through which

a current of four amperes flows also has 400

ampere turns.

Electromagnetic Induction. We saw ear-

lier how a current carrying conductor will

generate a magnetic field which is perpen-

dicular to the conductor's axis. Conversely, a

current will be induced in a conductor when

CIRCUIT 2

B

A

SECONDARY

CIRCUIT I E

+111111-

PRIMARY

Slew

Fig. 21. Two -core transformer is inefficient since an

air gap at either end does not have permeability of o

ferrous metal and some flux lines do not go through

core of secondary winding (8) -their effect is lost.

the conductor is passed through a magnetic

field. The strength of this induced current

is proportional to both the speed at which

it passes through the field and the strength

of the field. One of the basic laws pertaining ,

to electromagnetic induction is Lenz's law

which states: "The magnetic action of an in-

duced current is of such a direction as to

resist the motion by which it is produced."

Fig. 21 illustrates two coils, A and B,

which are placed in close proximity to each

other. Coil A is connected in series with a

switch and battery so that a current may be

sent through it when the switch is closed, and

coil B is connected with a current -indicating

DC meter. When the switch is closed, cur-

rent will flow through coil A, causing a mag-

32

netic field to be built up around it. In the

brief instant that the field is building up to

maximum, it will "cut" the turns of coil B,

inducing a current in it, as indicated by a

momentary flick of the indicating meter.

When the switch is opened, breaking the

current flow through coil A, the field around

coil A will collapse, and in so doing will

again induce a current in coil B. This time,

however, the flow of current will be in the

opposite direction. The meter will now flick

in an opposite direction than it did when

the switch was closed. The important thing to

remember is that the conductor must be in

motion with respect to the magnetic field or

vice versa in order to induce a current flow.

You can perform this simple experiment

using two coils made of bell wire wrapped

around large nails, a few dry cells in series,

and a DC zero -center scale meter.

Self Induction. As mentioned a short

while ago, a magnetic field is built up around

a coil at the application of current through

the coil. As this field is building up, its mov-

ing lines of flux will cut the turns of the

coil inducing a counterelectromotive force

Fig. 22. Toroidal core is highly efficient but is very

difficult to manufacture. Familiar C- and E -shape core

has less waste and windings are slipped over the core.

Efficiency is good -about 90 percent for most designs.

or counter EMF which opposes the current

flowing into the coil.

The amount of counter EMF generated

depends upon the rate of change in amplitude

of the applied current as well as the in-

ductance of the coil. This value of inductance

is dependent upon the number of turns in the

coil; a coil with many turns will have greater

inductance than a coil with few turns. Also,

if an iron core is inserted into the coil, the

inductance of the coil will increase sharply.

The unit of inductance is known as the henry.

The Transformer. One of the most im-

portant and widely used applications of mag-

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35

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netic induction is the transformer. Trans-

formers find the major application in stepping

up or down voltage and current in countless

applications.

Fig. 22 shows the basic construction of a

typical transformer. While two separate

windings are shown here, some transformers

can have as many as five or six windings.

A transformer consists of two or more sep-

arate windings, electrically insulated from

each other. One winding, which is known as

the primary winding, is fed from a source of

alternating current.

The alternating currents flowing through

the primary induce a current in the secondary

winding by virtue of magnetic induction. The

transformer core is constructed from a rela-

tively high permeability material such as iron

which readily conducts magnetic flux be-

tween the primary winding and secondary

winding.

The alternating current flowing in the pri-

mary of the transformer produces a variation

in the magnetic flux circulation in the trans-

former core which tends to oppose the cur-

rent flowing in the primary winding by virtue

of self- induction. The counter EMF is just

about equal to the voltage applied to the

primary winding when no load is connected

to the transformer's secondary winding. This

accounts for the fact that very little current

flows through the primary winding when no

load is connected to the secondary. The negli-

gible current that does flow under this no -load

condition is known as the transformer mag-

netizing current. As the current drawn from

the secondary winding increases, the primary

current will increase proportionately due to

the reduction in the counter EMF developed

in the primary winding of the transformer.

In any transformer the ratio of the pri-

mary to secondary voltage is equal to the

ratio of the number of turns in the primary

and secondary windings. This is expressed

mathematically as follows:

Ep Np

Es Ns

where Ep = primary supply voltage

Es = voltage developed across

secondary

Np = number of primary turns

Ns = number of secondary turns

The above formula assumes that there are

no losses in the transformer. Actually, all

36

transformers possess some losses which must

be taken into account.

Transformer Losses. No transformer can

be 100 per cent efficient due to losses in the

magnetic flux coupling the primary and

secondary windings, eddy current losses in

the transformer core, and copper losses due

to the resistance of the windings.

Loss of magnetic flux leakage occurs when

not all the flux generated by current flowing

in the primary reaches the secondary wind-

ing. The proper choice of core material and

physical core design can reduce flux leakage

to a negligible value.

Practical transformers have a certain

amount of power loss which is due to power

being absorbed in the resistance of the pri-

mary and secondary windings. This power

loss, known as the copper loss, appears as

heating of the primary and secondary

windings.

There are several forms of core loss -

hysteresis and eddy current losses. Hysteresis

losses are the result of the energy required- to

continually realign the magnetic domain of

the core material. Eddy current loss results

from circulating currents induced in the

transformer core by current flowing in the

primary winding. These eddy currents cause

heating of the core.

Eddy current loss can be greatly reduced

by forming the core from a stack of indi-

vidual sheets, known as laminations, rather

than from a single solid piece of steel. Since

eddy current losses are proportional to the

square of core thickness, it is easy to see that

the individual thin laminations will have

much less eddy current loss as compared

with a single thick core.

Another factor which effects eddy current

loss is the operating frequency for which the

transformer is designed to operate. As the

operating frequency is increased, the eddy

current losses increase. It is for this reason

that transformers designed to operate at radio

frequencies often have air cores and are void

of ferrous metals.

Theory and Practice. We've come a long

way from our initial discussion of the atom

and its importance for an understanding of

electricity and magnetism. And there's still

a long way to travel to understand all about

the subatomic nucleus and its satellites and

how they are being harnessed in an ever-

expanding electronics technology. But, we

move ahead by mixing theory with practice -

so, put your new knowledge to work in a

project or two!

ELEMENTARY ELECTRONICS

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Basics

of

RTTY

..

Speeds of 60 wpm

are attainable, with

characters typed

as fast as sent out.

"I read you five by five" is a familiar

phrase in Ham radio. But the only crowd

who can use it literally is the one on RTTY

-Ham radioteletype. These communica-

tions are by printed page, with typed -out

messages you can really read. Instead of

speaking into a mike or hitting a key, the

RTTYer sits at a machine (Fig. 1) that

looks like an overgrown electric typewriter.

There's the usual back -and -forth rag chew-

ing, but it's neither voice nor Morse code.

In the words of the RTTYer stations "print"

each other.

These are the guys responsible for funny -

sounding pulses you've probably heard on

CW -the ones that sound like a chirpy CW

signal running at high speed. And you might

have wondered how anyone could copy such

fast code. No one can, of course, since the

pulses are too fast for the human brain to

follow. But the Ham's Teletype machine

thrives on speed, and tools along at 60 words

a minute.

Is high speed the reason for hams on

RTTY? In most cases it is not. The main

appeal of RTTY is that the field is wide open

for the experimenter. It's something entirely

fresh for the natural -born tinkerer. It takes

a while to get used to the idea of putting oil

on a piece of radio gear, but once a ham gets

accustomed to this marriage of mechanics

and electronics, he seldom gives it up. For

the fellow who likes to turn thumb screws

as well as tuning capacitors, RTTY offers a

never -ending challenge. Many Hams rise to

this challenge like a rocket leaving the

launching pad, and devise original circuits

for receiving and decoding the RTTY signal

that makes the wheels go 'round.

Pulses. A Teletype machine feeds on a

special diet of electrical pulses. These pulses

trigger a mass of levers and gears inside the

machine into motion which print letters and

figures on a paper roll. As in Morse code,

there is a different combination of pulses

for each printed character, plus a few extras

for spacing and functions such as carriage

return, line feed, shifting from figures to

letters, even ringing an attention -getting bell.

For each letter, figure, or machine func-

tion, there is a set of seven pulses. First is

a start pulse which tells the machine in ef-

by Marshall Lincoln

K9KTL

JULY -AUGUST, 1966 37

www.americanradiohistory.com

@AD BASICS OF RTTY

fect: "There's a signal starting to come in.

Hitch up gears and get ready." The last pulse

is a stop pulse, which instructs the machine:

"You're done with that letter, relax for a

few milliseconds before the next one comes

along."

Those five pulses between start and stop

are the ones which determine which letter

or figure the machine will print, as shown

in Fig. 2. This is why the Teletype code used

by Hams is called a five -level code. The

intelligence- carrying job is primarily done

by various combinations of five pulses. Con-

sider it this way. Think of five zeros:

0 0 0 0 O. Each zero represents a fraction

of a second, or interval of time. Let's say

the signal for the letter R comes into the

machine. Letter R consists of a pulse in

the second and fourth intervals (with no

pulse in the first, third and fifth intervals).

You could represent the R in code like this:

O X O X O. The letter Y, on the other hand,

is just the opposite: X O X O X. So we see

that different pulse and space combinations

determine the character. Incidentally, letters

R and Y frequently are used to test Teletype

machines. They're electrical opposites, and

make the machine reverse gears, so to speak,

after each interval. This provides a good

test of all vital parts in the machine.

In RTTY parlance, the presence of a pulse

at the machine is a mark and the absence of

one is a space. The terms are carryovers

from the old days of the printing telegraph,

when dots and dashes were actually printed

by the receiving machines. Both mark and

space are referred to as pulses, but at the

machine itself a mark means pulse of cur-

rent, while a space is the absence of current

for a definite interval.

There are 32 possible combinations (Fig.

3) of these five mark and space pulses.

They cover 26 letters of the alphabet and

the mechanical machine functions already

mentioned. There are no lower case letters

on the machines -all letters are capitals. By

pressing a Figures key the machine is set up

to print figures (numerals) and punctuation

marks. Pressing a Letters key gets the ma-

chine back to letters again. Many machines

also have levers which shift them to printing

letters when the space bar is pressed.

When Hams first started using Teletype,

they simply keyed the transmitter carrier;

on for mark, off for a space. This was done

Fig. 1. Copy is actually read at this Ham shack.

There are some differences in Teletype keyboard but

if you can type you can transmit RTTY messages.

' t

f IGs -? :S3!4 8' ( ) . ,9pSi 4°57; 2/6"

L TPS ABCOEFGH I JKLMNOPQRS TUVWXYZ[-:C1

dLuw

Fig. 2. Punched tape indicates all characters available on keyboard

of RTTY printer. No small (lower case) characters are used with this five -

level code. Depressing Figures key allows you to send numerals,

punctuation marks and ring attention- getting bell used by news services. Q?á

UJJ Lt. v)

ELEMENTARY ELECTRONICS

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;'Z' E o 4)?.,

41) , 4110

- : :` ;

L_ r

ANT.

RF SIGNAL

M S M

HAM RECEIVER AUDIO SIGNAL

M S

111

M

SPKR

rapidly by the switching mechanism inside

the machine.

The Problems. Interfering signals or

noise pulses could fill in the brief interval

of "dead air" when the transmitter was off

during a space. This would make the re-

ceiving machine print garbled copy (wrong

letters).

So, they tried transmitting a signal on one

frequency for mark and on a sightly different

frequency for space. It worked well, and

that's the way it's done today. It's called

frequency -shift keying (FSK). The trans-

mitted carrier remains on continuously, but

it is flipped rapidly back and forth between

two adjacent frequencies. That's the reason

an RTTY signal sounds chirpy.

The FCC allows Hams up to 900 cycles

of shift for RTTY work. Hams have pretty

much standardized on 850 cps. This pro-

vides wide enough shift to make it fairly

easy to adjust equipment, and leaves a mar-

gin for error and still stay within the legal

limit. Some operatofs are experimenting

with narrow shift, down around 170 cps or

so. This requires better equipment to dis-

tinguish between the two frequencies so close

together, but has the advantage of being less

susceptible to interference.

Incoming. To receive an RTTY signal, a

ham generally uses an ordinary communica-

tions receiver with the BFO turned on so

JULY -AUGUST, 1966

Fig. 3. Keyboard

only needs three rows

of keys since the

twenty -six lower -case

letters of the

alphabet are not used.

Letters are in some

positions on typewriter.

Fig. 4. (below) Block diagram

for RTTY receiver.

RTTY

CONVERTER (TU)

FILTERS

/ RELAY

1

LINE

CURRENT

MSM

TELETYPE

PRINTER

Fig. 5. Teletype tape does not usually have

any printing but experienced operators often read

tape perforations across width of paper tape.

the frequency shifts of the incoming signal

produce a varying audio beat note in the

receiver. (The overall system is in Fig. 4.)

These audio notes are fed to a device var-

iously known as a terminal unit (TU), re-

ceiving converter, or demodulator. Basic-

ally it contains a pair of filters tuned to two

audio frequencies which are 850 cycles

apart. Conventionally, these are 2975 and

2125 cps. One filter accepts the mark fre-

quency (2125 cps), the other accepts the

space frequency (2975 cps) and passes them

through a stage of amplification then to a

keyer tube on relay. This controls current

to the Teletype machine. Current flows for

mark and is turned off for space. This op-

erates an electromagnet in the machine

which, in turn, triggers a series of levers

which operate type bars.

On six meters and above, Hams use a

slightly different method for sending RTTY

39

www.americanradiohistory.com

o BASICS OF RTTY

Fig. 6. Tapes can be

prepared in advance and

then zipped ouf at 60 wpm

by tape distributor

(to left of keyboard).

Fig. 7. Received copy

rolls right out of printer

that resembles typewriter.

Generally special long

lengths of paper are used

unfolding directly from

packing box into printer.

signals. Instead of shifting the carrier fre-

quency to correspond to mark and space

pulses, the steady carrier is modulated with

two audio tones -one for mark, the other

for space. This is known as audio frequency

shift keying (AFSK). Converting the re-

ceived tones to electrical pulses is done much

the same as with FSK, except the receiver

BFO does not need to be turned on. AFSK

is not permitted below 50 mc, so hams on

the lower frequencies must use FSK.

Outgoing. Transmitting Teletype signals

is relatively simple. The keyboard of a Tele-

type machine operates a set of electrical con-

tacts that open and close in sequence to form

the mark and space pulses of the Teletype

code. These contacts are connected to the

transmitter VFO (in the case of FSK) or

to an audio -tone generator (in the case of

AFSK) which feeds its output to the trans-

mitter. Many people are surprised to learn

that a Teletype actually is two separate ma-

chines in one cabinet. Although both are

driven' by the same motor, the receiving and

sending units are otherwise completely sep-

arate. They may be connected together elec-

trically so the receiving unit prints what the

40

sending unit is sending, or they may be op-

erated independently. An operator may bang

away at the keyboard, sending a message,

while at the same time monitor his sending

on the same machine. Or, he can receive a

message on one frequency while sending a

message on a different frequency -with the

same machine!

A more versatile arrangement is to use

a machine which punches holes in a paper

tape (Fig. 5.) corresponding to mark and

space pulses. This tape may then be fed

through a device called a tape distributor

which operates the transmitter the same way

as a keyboard. A tape distributor (Fig. 6.)

contains its own motor and a set of electrical

contacts like those operated by a Teletype

keyboard. As the tape is pulled across a set

of sensing pins by a cog wheel, the pins

(feeling holes in the tape) operate electrical

contacts. They create electrical pulses iden-

tical to those produced by a Teletype key-

board. The result is shown in Fig. 7.

With this set -up, a Ham can prepare a

long transmission or series of messages in

advance of going on the air. Then the tape

distributor can do the actual sending at a

smooth, constant speed. Or, he may receive

an incoming transmission on his printer

while at the same time preparing his answer

by punching a tape. When his turn comes

to transmit, he feeds the punched tape into

the tape distributor, which obediently bangs

away at an impressive 60 wpm.

If the prospect of humming machinery

wedded to electronic circuits looks inviting,

why not look further into RTTY? Part 2 of

this article tells you what you need to know

for getting a rig on the air.

ELEMENTARY ELECTRONICS

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0000 0

0

000 00 000 00

Communicate

with instant -

messages. A

typed sheet of

copy straight

from the receiver

gets those cans

off your ears and

the pencil out

of your "fist" but

RTTY's hard work.

.0

0 00.0 . . 0.0

00.00

. . 000.0 . 0. .

000.0 . 0.

You won't have to hock the family jewels

or get an engineering degree to get on radio -

teletype. If you're a ham with a reasonably

good rig, you may already own about 75%

of an RTTY station. How about the other

25% -and the myriad items you need to

know about before you can hit those 32

green keys? Before considering them, here's

the most important question of all.

Is It Your Cup of Tea? If the ink is barely

dry on your Ham ticket, better get your kicks

first on phone and CW. They provide solid

operating experience needed for more sophis-

ticated RTTY. Later, when the thrill goes

out of brass pounding, and your voice grows

hoarse from calling CQ, you're a candidate

for QSO'ing on a teleprinter machine. As

scores of once -jaded Hams will attest, it can

put the sizzle back in ham radio.

Hams who won't touch a screwdriver,

maybe cringe at the sight of an oil can, or

can't wire an AC plug, probably won't en-

joy the game. Though you need no great

skill or know -how, it's an asset to enjoy

.JULY- AUGUST, 1966

Putting

RTTY

in the

Shack

by Len Buckwalter

K10DH

fiddling and experimenting with equipment

-even if you have to go by the book. Your

RTTY machine will have a mass of mechan-

ical parts going ta- pocketa ta- pocketa, and

they need a roll -up- your -sleeves lube job at

regular intervals. RTTY is for the nuts -'n-

bolts man.

Take Stock. Some Ham RTTY rigs re-

semble the inside of the blockhouse at Cape

Kennedy. But in the beginning there's no

need for that level of complexity. Let's be-

gin with the basic rig; a receiver and trans-

mitter combination you might already have.

There is no special circuit needed inside the

receiver. Any reasonably good model fills

the requirement. About the only type that

won't give satisfactory results is the AC -DC

gutless wonder that quivers as you walk

across the room. The receiver must be fairly

stable or you'll have to do a lot of retuning to

keep the RTTY signal on the nose. But

given plenty of warm -up time, a moderately

priced set will stop drifting and provide the

required stability. Other worthwhile receiver

41

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RTTY IN THE SHACK

A typical Ham RTTY CCU can be punched into

tape. Spliced end -to -end it can be run

continuously through tape keyer for calling.

Teletype machine, in front of operator (below)

is used with units on shelves at rear. All

}hat's needed is a TU converter. The Twin City

converter -a 3 -tube job -is shown at right.

features: an easily adjusted BFO and band -

spread tuning. Exceptional selectivity in the

receiver is nice to have, but not imperative

for the beginning RTTY'er. Chances are

you'll start with standard (as opposed to nar-

row) shift operation where the signal is re-

latively wide. The only modification to the

receiver in a simple system is tapping the

incoming audio signal from the speaker ter-

minals.

The frequency bands used for radiotele-

type correspond to those of regular phone

and CW work. RTTY stations commonly use

80, 40 and 20 meters. Within each band

there are RTTY frequencies where stations

tend to cluster (like 3620, 7140, and 14,090

kc.). Some operators prefer VHF bands -

6 and 2 meters. These are valuable for

QRM -free, local contacts. Thus the regular

ham rig provides the necessary frequency

coverage on HF, with receiving converters

added for VHF, if desired.

42

Some of the Ham RTTY publications (right)

help point up the state-of-the-art of

Ham equipment and RTTY experimental units.

Transmitter requirements. No complex

circuits are needed inside the transmitter, but

it should have variable -frequency oscillator

(VFO). (Crystal- controlled oscillators don't

lend themselves to frequency -shift keying.)

You'll have to make up a simple adapter to

enable the Teletype machine to vary trans-

mitter frequency. It helps to have a stable

transmitter that won't drift and cause tuning

problems for the Ham trying to copy you at

the other end of the QSO.

On the matter of transmitter power, most

old- timers say pour on the coal. Good ad-

vice, but you can still do plenty of operating

at moderate power, especially for local rag

chewing and short skip. Try to get at least

100 watts into a good antenna. At higher

power there's more chance to work cross -

country and occasional DX. Lower power

has increased garbling, strike -overs and

missed words.

Total Tab. If you own a suitable rig, con-

ELEMENTARY ELECTRONICS

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sider next the cost of adding RTTY. The

price of a brand new Teletype machine is

about the same as a fully equipped Volks-

wagen. But incredible as it may sound, fine

Teletype printers -which function for both

send and receive -can run under $100! The

machine shown in the photos (a Model 26)

cost $60. It spews out signals as well as the

best of them. The secret is simply that Tele-

type machines are retired in sizeable num-

bers to make way for newer, faster machines

demanded by commercial and military serv-

ices. If it weren't for this cost -busting factor,

RTTY and Hamming simply couldn't mix.

How you can get these machines -and they

are not freely available except to hams -is

detailed in a moment.

After the machine, next item is the termin-

al unit (TU). This is the device which con-

verts audio signals from your receiver into

a form that can drive the Teletype printer.

.Again, the price of a commercial unit is sky

JULY- AUGUST, 1966

high, but cost is piddling if you build the

popular home -brew job known as the Twin

City converter. As shown in the photos it's

a 3 -tube chassis. All new parts cost about

$35, but a generous junkbox can slash that

figure. We built ours for some $10 in new

components.

Thus the grand total for getting on the air

with a functioning RTTY rig might dip as

low as $70. Sure you can get ritzy acces-

sories, like a scope for visual tuning of the

RTTY signal but it's not a beginner's ne-

cessity. (Later on you'll give up candy bars

to buy one.) There's one other item -the

keyer unit which enables the Teletype mar

chine to drive your transmitter as you type.

In some Ham rigs, it is done simply with the

addition of a potentiometer (with instruc-

tions provided by the manufacturer) or an

uncomplicated 1 -tube or 1 -diode circuit.

Get The Dope. Before buying any hard-

ware consider these sources of information.

They contain much valuable data on Ham

RTTY:

The New RTTY Handbook by Byron H.

Kretzman. Cowan Publishing Corp., 14

Vanderventer Ave., Port Washington, L.I.,

N. Y. 11050. $3.95. This 191 -page book

covers theory and practice. It contains the

Twin City converter circuit and construction

data. Listed are Hams in each of the call

areas who might supply you with leads on

where to purchase equipment locally.

Ham -RTTY by W2NSD /1, W4RWM. 73

Inc., Petersborough, N. H. This is another

source book; 113 pages, $2.

RTTY Bulletin. This is a monthly bulletin

published by the RTTY Society of Southern

California, 372 West Warren Way, Arcadia,

Calif. Rate is $3 per year. This publication,

by the leading ham RTTY organization, is

newsy journal of what's happening in RTTY;

from circuits to contests, and anything else

that touches the hobby. A useful feature is

the Horse Trades column. Each month it

lists a raft of RTTY equipment for sale and

trade. Ads are free to members.

Copying Commercials. It might be ap-

parent that it's possible to set up one -half

of an RTTY system -the receiving end -

and be able to copy commercial stations

transmitting press, telegrams and other traf-

fic. Several factors work against it. For one,

these stations exist out of the regular Ham

bands, although occasionally they can be

pulled in when they're close to the band

edges. But even if you tuned with a general-

coverage receiver, where such stations

43

,1;

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RTTY IN THE SHACK

abound, your machine would copy few sig-

nals. Most commercial stations have switch-

ed to newer equipment and higher speeds.

The Ham system is synchronized to 60 words

per minute and prints gibberish on most

signals other than Ham.

Tickling The Keys. While it helps to know

how to touch -type when operating a tele-

printer, there's no deterrent to the hunt-'n-

peck typist. Operating speed is not com-

parable to CW, for example, where the fast

operator must slow down for the beginner.

The reason is that the printer makes a typed

record of an incoming transmission. If a

particularly slow typist is sending, you don't

even have to sit at your machine. Fill in the

log, touch up a tuning knob or even leave

the shack for a few minutes. The machine

will clack away unattended. Thén you can

walk over to the machine and read the whole

transmission in a minute or so.

Sometimes another operator comes tear-

ing back at top speed like a typing champ.

Don't be fooled. He may be a two -finger

typist who has punched a tape during your

transmission. Played back through tape

equipment, it transmits at maximum speed.

Although this kind of snappy operation

typifies the advanced RTTY'er, manual

typing skill is an advantage and it makes op-

erating more pleasurable.

Before You Plunge. Getting a basic

RTTY rig on the air is neither complex nor

time -consuming. But there's an important

qualification: It is definitely not like build-

44

Scope (above) helps to tune RTTY signals for

best, error -free copy at advanced installations.

For trouble -free operation you'll have more

than the usual amount of maintenance work. Regular

use of the oil can, and cleaning, will be a must.

Dust and lint must be removed and oil gets gummy.

ing a kit, or even a construction project like

the ones in this magazine. There is no single

publication in RTTY literature that takes

you by the hand and tells you to hook wire A

to terminal B. And even if you are well -

stocked with diagrams, this is no guarantee

that you'll wire equipment correctly.

But there's an answer. By checking

through the publications listed earlier, and

the Call Book, you should be able to locate

an active RTTY'er in your area. If he's

typical of most hams, he'll heap you with

advice and helpful suggestions. When we

got our machine, we puzzled for hours over

some dangling leads. A phone call to an ac-

tive RTTY'er in the area solved the problem

in about three minutes. Of course, once you

get on the air, the rig becomes a direct radio

link to hundreds of fellow hams who'll la-

vish you with sound RTTY advice.

Meet You On The Green Keys. That's

one expression you'll be seeing -and printing

-if you go RTTY. Is it worth the effort and

cost? Yes, if you want to get in on one of

Hamdom's remaining outposts for the ex-

perimenter seeking an exciting and different

mode of communication. As a bonus, you'll

be able to copy news bulletins each evening

from the ARRL's station W1AW. They cov-

er everything from reports on OSCAR, the

orbiting Ham satellite, to propagation re-

ports on band conditions. And when you

work other RTTY'ers around the country,

you, too, can sign off with; "see you further

down the page. OM."

ELEMENTARY ELECTRONICS

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Using

Cross - Coupled Circuits

by Jack Brayton

Cross -coupled circuits can add, subtract,

gate, read information in or out, count, gen-

erate square waves, eliminate unwanted

pulses, shift numbers left or right, store in-

formation indefinitely, and accomplish many

other tasks far too numerous to list.

In addition to their wide use in computers,

they're also used for timing, triggering, pulse

shaping, etc. In spite of the many functions

cross -coupled computer circuits can perform,

they're not complicated, difficult to under-

stand, nor expensive to build. In fact, we'll

outline 3 experiments, all of which can be

breadbroaded (using the same parts for each

experiment and clip leads for switches) for

about $4.00. Even this low figure can be

cut in half if you have a 6 -volt DC source

and a few scrap parts.

Also, for those who want something more,

plans for a complete cross -coupling demon-

strator (Fig. 1) are included. This unit,

which costs about $8.50, makes a good Sci-

ence Fair project and includes the three

basic types of cross -coupling. That is, DC

(direct- current), AC (alternating- current)

coupling, and a combination of AC and DC

cross -coupling can be selected simply by

flipping a switch. All three circuits are

broadly classified under the multivibrator

heading. And, although the circuits look

similar, they're very different in the jobs they

perform.

Cross coupling

two single -stage

amplifiers

produces a

simple multi-

vibr ator that

can be used to

demonstrate

circuits used

in all digital

computers

Fig. 1. Demonstration unit has

three types of multivibrator

circuits easily selected by a

front panel 3- position swifch.

.ÌIIi.YAIIOIIST, 1966 45

www.americanradiohistory.com

CROSS- COUPLED

CIRCUITS

Now, let's run through each of the experi-

ments and discover exactly how they work

and why they work that way.

DC Cross -Coupling. Fig. 2 shows the

schematic used for the first experiment; a

flip flop or bi- stable multivibrator. It con-

sists of two DC- coupled, common- emitter

amplifiers. Q1, R3, R5, and Il form the

first amplifier while Q2, R4, R6, and I2

form the second. You'll notice that the

first amplifier's output is directly coupled

(through Rl ) to the input of the second

amplifier. Further, the second amplifier's

output is directly coupled (through R2) to

the first amplifier's input. This causes the

circuit to have two stable states. That is, Q1

can be conducting with I1 lighted or Q2 can

be conducting with I2 lighted. Thus the

transistors act like simple switches for the

lamps and have either a high resistance

(open) or low resistance (closed) across

their emitter /collector leads. The cross -

coupling, as we'll show, prevents both tran-

sistors from conducting at the same time.

To explain, let's trace the circuit's action.

When power is first applied to the circuit,

one of the transistors will turn on faster

than the other, which causes this transistor

to conduct while the opposite transistor cuts -

off. We'll assume Q1 conducts while Q2 cuts

off. When Q2 is cutoff its collector rises to

-6 volts. This results from the fact that the

resistance of Q2's emitter /collector junction

is then much higher than the series circuit

composed of R4 and the lamp. Thus, al-

most the full battery voltage appears across

Q2. However, some current flows through

R2, R5, and the emitter /base junction of

Q1. This current, although not large enough

to light I2, is large enough to cause Q2 to

saturate. Thus, Q l's emitter /collector re-

sistance becomes much lower than that of

R3 and Il. This being the case, most of

the battery voltage is dropped across Il and

R3. This, in turn, causes I1 to light. Q2

cannot conduct, under these conditions, be-

cause Q1's collector potential is at, or near,

ground and hardly any current flows through

Rl, R6, and the emitter /base junction of Q2.

The circuit can be switched from one

state to the other merely by closing the input

switch to the transistor which is conducting.

46

Fig. 2. DC or direct coupled bi- stable multivibrator

circuit will let but one lamp light at a time.

Pressing pushbutton (SI or 52) grounds base and

transistor jumps to cutoff and other transistor

jumps into saturation and is held there by the

high -negative bias applied to base connection.

Fig. 3. Charge and discharge of Cl and C2 cause

lamps II, 12 to blink, alternately, on and off.

For example, if I1 is lit and Q1 is conducting

we would close S1. This switch momentarily

shorts the current flowing through R2, 125

and the emitter /base junction of Q1 to

ground. Thus, the base current of Q1 is

removed and Q1 is cutoff causing its col-

lector to go to -6 volts. Now, current can

flow through R1, R6, and the base /emitter

junction of Q2. Q2 saturates and its collector

voltage goes toward ground potential, re-

moving the forward base bias from Q1. Hav-

ing switched states, the circuit will hold or

"remember" its new state until the opposite

switch (S2) is closed momentarily. This

action, of course, closely resembles that of

a latching relay except the circuit switches

much faster, has no moving parts to wear

out, and usually costs less than electro-

mechanical relays.

AC Cross -Coupling. Fig. 3 shows the

second experiment; an astable or free -run-

ning multivibrator. This circuit is similar

to the first circuit except there are no input

switches and the resistors (Rl and R2, of

ELEMENTARY ELECTRONICS

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the first circuit) have been replaced by ca-

pacitors Cl and C2. This causes the circuit

to oscillate and the lamps to blink on and of

alternately. It also causes a square wave to

be produced at both collectors. To find out

how this is accomplished let's take a closer

look. Again, we'll assume Ql conducts and

Q2 is cutoff when the power is first applied.

Also, we'll assume C2 was previously dis-

charged.

When Q2 is cut off its collector rises to

-6 volts and, since C2 has already been dis-

charged, it offers almost no resistance to cur-

rent flow during the first instant. Thus C2

starts to charge through I2, R4, R5, and the

emitter /base junction of Ql. This causes

Ql to saturate; its collector goes toward

ground potential; and Il lights. At the same

time, Cl starts to discharge through the

emitter /collector resistance of Q1 in satura-

tion; R4, and the back resistance of Q2's

emitter /base junction. It's important to note

that C2 is charging and holding Q1 in sat-

uration while Cl is discharging and holding

Q2 cutoff. Thus, the circuit is at a standstill

for a length of time determined by the

charge and discharge times of Cl and C2.

(This time can be altered simply by increasing

or decreasing the size of these capacitors.)

When C2 has finished charging, current

flow through the capacitor stops, which

means Q1 is no longer forward biased. Thus,

Ql is cutoff causing Il to go out and its

collector potential to go to -6 volts. Cl

having discharged -either partly or fully -

starts to charge to this higher collector po-

tential. It does this through Il, R3, R6, and

the emitter /base junction of Q2. Q2, in turn,

saturates causing I2 to light and its collector

to go toward ground potential. Now C2

starts to discharge through Q2's emitter -col-

lector resistance in saturation, R5 and the

back resistance of Ql's base -emitter junction.

Again the circuit is at a standstill until Cl

and C2 have charged and discharged. Then

the entire cycle repeats itself, endlessly.

Because the collector potentials are con-

stantly changing from ground to -6, stay-

ing at -6 for a length of time, then returning

to ground, a square -wave is produced at each

collector.

Before we go on to the next experiment,

it should be noted that Cl and C2 do not

have to be the same value. Making them

different will cause one lamp to stay on

longer than the other. With the values shown

the lamps blink on and of about twice a

second.

JULY -AUGUST, 1966

Fig. 4. Pressing SI sends Q1 to cutoff. 12 will

remain lighted until Cl charges. Both lamps

will remain dark until SI is released -then 11

will light and remain lit while S1 is open.

AC /DC Cross -Coupling. The third circuit

(Fig. 4) is really a combination of the first

two. That is, one AC and one DC coupled

amplifier is used to form a one -shot or mono-

stable multivibrator. The one -shot -as its

name implies -provides one cycle for each

input pulse.

When power is first applied to this circuit,

I2 will always light for an instant because

Cl allows a heavier base current to flow

through Q2 than resistor R2 allows in Q1.

However, 12 will not stay lit very long be-

cause as soon as Cl has charged Q2's base

current drops to zero and that transistor is

cutoff. This, of course, causes a heavy base

current to flow through R2, R4, and the

emitter -base junction of Ql. Ql saturates;

Il lights and stays lit, indefinitely.

Of course, momentarily closing S1 will

cause Q1 to cutoff; Cl to charge; Q2 to

saturate; I2 to light and stay lit for as long

as it takes Cl to charge. After that Q2 will

cutoff and the circuit will return to its orig-

' Iit49 íI49 12 G)

R4

R3 68A

-

68A

300MF DECK -An DECO)! C2 300MF S3

+ 1 __

R1 a S4 2 R2

It 1.8K a -- s 1.8K. 02 e

12t1322 2N32Zj'

b Bi

á7on I

116

e 6T

470lL '

Fig. 5. Double -pole, 3- position switch changes

the connections to the different circuits. For

some demonstration purposes a neatly breadboarded

circuit can use clip leads in place of S4.

47

www.americanradiohistory.com

48

CROSS- COUPLED

CIRCUITS

1e"

9

16 az DIA.(2 REO)

sá1DIA.(4RE)) ÿ DIA.

é 2.DIA

4

2"

o

16

11

DIA 16'

(24 REQ)

' 45

2DIA.

4"

Fig. 6. Front and sloping panel layout for the

cabinet calls for 4 -inch width since rounded edges

of some cabinets do not leave more usable width.

Rubber cement or tape full -size template to panel.

PHENOLIC BOARD

S3

01

final state. Thus, as we've already mentioned,

one input pulse generates one output pulse.

About The Demonstrator. Looking at the

demonstrator's circuit shown in Fig. 5 we

can see that it's exactly like the experiments

except we've included all three types of cross

coupling and provided a means of switching

from one to the other. Thus, the demon-

strator works similar to the experiments and

its theory is identical.

Construction. Laying out the chassis is, of

course, the first step and this is done accord-

ing to Fig. 6. The layout should be drawn

on graph paper then taped to the front panel

and the hole- centers punched.

The slot for the lever switch can be easily

made in the following manner. First, drill

the 1/4 -inch hole at the slot's center as shown.

Then, using a keyhole hacksaw, cut the slot

and file the edges smooth. Since the slot

only has to be about Ms -inch wide, very little

(Continued on page 110)

C2 Ci

R1

R4

Ir .-,r -.--. , 0.

R2

02

; -:--- R6

R5 * . ..-.

étRt

i. i < I"

I1

NOTE I"

SPACERS

Fig. 8. Perforated phenolic board

is ideal for assembling this small

circuit. Wiring is not critical

since feedback from stray capacitance

is not likely in this low- impedance,

low -frequency multivibrator circuit.

Fig. 7. With the sloping panel down,

all major components are visible -

none hidden. Transistor circuitry

is on phenolic board with leads

going to switches and lamps on panel.

R3

PARTS LIST

B1 -6 -volt battery (Burgess, Z -4 or equiv I

Cl, C2- 300 -mf., 6 -volt electrolytic capacitor

(Sprague, TE -1106 or equiv.)

I1, 12 -Pilot lamp, 2.0 -volt, 0.06 amp.,

bayonet base. (type 49 or equiv.)

01, Q2 -pnp transistor, 2N322, 2N188A,

2N241 A, 2N270, 2N404A or equiv.

R1, R2- 1800 -ohm, 1/2 -watt resistor

R3, R4 -68 -ohm, 1/2-watt resistor

R5, R6-470 -ohm, 1/2-watt resistor

Si, S2- S.p.s.t., momentary contact pushbut-

ton switch (Leecraft, 7 -1 1 or equiv.)

53- S.p.s.t. toggle switch (Cutler- Hammer,

8280K14 or equiv.)

S4 -2 -pole, 3- position, positive index, lever

switch (Centralab, 1454 or equiv.)

1- Battery holder (Keystone, 175 or equiv.)

2 -Pilot lamp sockets ILeescraft, 7 -11 or equiv.)

1- Sloping -panel utility box (41/2 "H x 41/4 "D x

4- 3/16 "WI (Premier, ACPC -1200, or equiv.)

Misc.-Perforated-phenolic board (2- 7/16" x

33 /e "); machine screws; spacers; flea clips;

wire; solder, etc.

Estimated construction cost: $8.50

Estimated construction time: 2 hours

ELEMENTARY ELECTRONICS

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Buîld'em

Good

by John D. Lenk

Any electronics kit, built in the home

workshop, can look just as professional as

those factory -wired jobs. Those squared -off

wiring turns and neatly positioned resistors

and capacitors don't just happen by accident,

though. It does take a little more effort and

some know -how to keep that chassis from

looking like a "ball of snakes" from which

all wiring emanates.

Of course we're referring to that other

fellow's projects, not the ones you've built.

Your kits never have panels that were

scorched by hot soldering irons or scratched

by a slipped screwdriver -they never look as

if they were built using a blowtorch, pipe

wrench and a sledge hammer. Do they?

Well, here are some tips you can pass on

to those less adept constructors when they

ask you for your secrets of producing finished

gear (kits or home brew) that not only

works well but looks good -inside.

JULY- AUGUST, 1966

Tips on soldering and

tools for good-looking

electronics projects

The Facts. We contacted the service rep-

resentatives of various kit manufacturers to

find out where most home workshop kit

builders go astray. The consistent repair

problems are those caused by improper work

habits, incorrect use of tools, poor wiring and

soldering practices and the inability to follow

instructions exactly.

Introduction To Soldering. Before going

into the practical side of electronics wiring

and construction, let's go over the funda-

mentals of soldering.

Soft solder, which is used in all electronic

construction except for a few specialized ap-

plications, is a fusible alloy, consisting essen-

tially of tin and lead. (We could tell you in

technical jargon that its purpose is to join

two or more metals at temperatures below

their melting point. Soft solders secure at-

tachment by virtue of a metal solvent or in-

termetallic solution action that takes place

49

www.americanradiohistory.com

BUILD 'EM GOOD

Pencil -type soldering irons are popular with numerous

technicians as well as hobbyists. Temperature -

selection iron is Heathkit GH -52 -has 8 ranges.

at relatively low temperatures. But that won't

help you make a better -soldered joint.) Soft

solders are not to be confused with hard

solders or brazing alloys whose action in-

volves the formulation of a fusion alloy with

the metal that is joined; nor are they to be

confused with welding alloys, whose action

again involves actual fusion with the respec-

tive metals. Soft solder secures attachment

by dissolving a small amount of the two

metals.

A soldered joint is chemical in character

rather than purely physical. Therefore, the

properties of a soldered joint are different

from those of the original solder alone be-

cause of the soldering process. The solder

is partly converted to a new and different al-

loy. Thus, a soldered connection is con-

tinuous in intermetal continuity while an un-

soldered one is discontinuous. When two

metals are soldered together, they behave like

one solid metal, but when bolted, wired, or

otherwise physically attached, they are still

two pieces of metal, and often they are not

even in direct physical contact with each

other due to the extremely thin insulating

film of oxide on the surfaces of one or both

of the metals.

When tin is added to lead, which melts at

621 °F, it lowers the melting point of lead.

Also, when lead is added to tin, which melts

at 450 °F, it lowers the melting point of tin.

The alloy of tin and lead with the lowest

melting point of the combined metals is

known as the eutectic composition. It con-

sists of 63% tin and 37% lead, and has a

sharp and distinct melting point of 361°F.

50

Lead is wrapped around

tie -point lug (above)

before applying heat to

lug (right) -close to

wrapped lead end.

Solder is applied to

lug -not to soldering

iron tip. Only when

lug is hot enough to

melt solder can you

be sure of good joint.

Except for this eutectic alloy, all tin -lead

solders are mixtures which do not melt sharp-

ly at any one temperature, but will pass

through an intermediate range of plasticity in

cooling from the liquid to the solid state.

Any solder containing less than 63% tin is

said to be eutectic plus lead while a solder

containing more than 63% would be eutectic

plus tin. Both melt at a higher temperature

than the eutectic composition.

Commercial solders cover the entire range

of tin -lead ratios from pure tin to pure lead.

A 50/50 (50% tin, 50% lead) or a 40/60

alloy is typical for electronic solders. Most

commercial solders in common use also con-

tain impurities. In special cases, other ele-

ments are added to the solder to change its

characteristics. Such elements include silver,

antimony, bismuth and cadmium.

The Flux of the Matter. All common

metals are covered with a non -metallic film

known as an oxide, which forms an effective

insulating barrier that prevents metals from

touching each other. As long as this non-

ELEMENTARY ELECTRONIC$

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Properly soldered connection

(top left) uses little

solder. Poorly soldered

connections (below) are not

smooth, have excessive

solder and may not even be

good electrical connections.

metallic oxide barrier is present on the sur-

face of metals, the metals themselves can-

not make actual metal -to -metal contact, and

as a result intermetallic solvent action (sol-

dering) cannot take place.

The soldering fluxes remove the metallic -

oxide film from the surfaces of the metals

and keep it from re- forming during the sol-

dering operation, in order that the clean free

metals may make mutual metallic contact.

Soldering flux has the same effect as scraping

a metal just before soldering. The flux does

not constitute a part of the soldered joint.

After soldering, the flux residue (still re-

taining its quota of captured oxides) lies

inert on the surface of the soldered joint.

Soldering fluxes are available as a paste

which is applied to the metals just prior to

soldering, or can be contained within the

solder as a core. Wire solder with a flux core

is the most common form of solder for elec-

tronic wiring. The paste is used primarily

to tin or prepare the surface of a soldering -

iron tip, or where a large surface must be

soldered.

Fluxes can be divided into three general

groups: (1) the chloride or acid type, (2)

the organic type, and (3) the rosin or resin

type. The acid or organic types of solder are

used mostly in sheet metal and plumbing

work and should not be used in wiring. In

With printed- circuits, soldering technique is about

the same. Pigtail lead is inserted and bent

fo a slight angle. Foil and lead are heated

together. Foil, being thin, heats rapidly.

Excessive heating can loosen foil from board.

fact, the kit manufacturers will void your

guarantee if there is evidence of soldering

with anything but rosin type solder.

The chloride or chemical acid fluxes con-

tain a strong acid that cuts the oxides quite

nicely, but the remaining acids will continue

to corrode the metals after the soldering

process is completed.

Organic fluxes contain mild acids that do

not tend to corrode the metals. However,

organic fluxes are unstable in the presence of

high temperatures, and some of them leave

a sticky, greasy, residue.

The rosin fluxes are ideally suited to elec-

tronic work for two reasons. First, the rosin

will act as an acid, to cut the oxides, only

when heated. The rosin returns to its nor-

Solder is applied to junction of soldering -iron

tip, foil and lead. Since junction of this foil

and fine wire heats rapidly, solder is applied

only a fraction of a second after heat. Very -thin

solder (20 gauge) is preferred by professionals.

51

www.americanradiohistory.com

(gAg BUILD 'EM GOOD

mal, non -acid, state when cool. This prevents

corrosion of the metals. The other reason

for the use of rosin flux is that it has a very

high electrical resistance (3300 trillion ohms

per cubic inch!) .

Putting the Heat on. No matter what type

of solder and flux is used, much of the suc-

cess in soldering is dependent on heating the

metals and solder. Part of the application of

heat is dependent upon the soldering tech-

nique (which will be discussed later). The

other part of the heat problem is selection of

the soldering tool. While many tools, meth-

After lead is soldered, clip it off close to board.

It is best to insert a group of components, solder,

then clip them. Doing individual components

will slow down assembly considerably -but the best

advice is to follow the manufacturer's instructions.

ods, and processes are used in industrial and

commercial work, either the soldering iron

or soldering gun are used almost exclusively

in electronics work. Actually, the term iron

is a hold -over from sheet metal soldering

methods. The soldering tools usually have

copper tips -some are plated on top of the

copper to prolong the life of the tip.

The ideal soldering tool should produce

enough heat for "high- heat" soldering (like

chassis solder lugs) but should not be too

hot for "low- heat" soldering (like circuit

board connections). A small efficient solder-

ing iron (also called a soldering pencil) with

a Vs - to 1/4-inch diameter tip is ideal for

most circuit connections. Soldering irons are

inexpensive and have the advantage of being

hot (if they're plugged in) whenever you

need them.

Poorly soldered boards are not a lost cause -

they can be repaired if you work carefully. Heat,

reapplied to the joint on bottom board, will

flow solder properly if lead is clean. At top,

excess solder can be removed with stiff brush.

Soldering Guns. These are generally used

as repair tools rather than for initial con-

struction. This is because they develop high

heat quite rapidly and cool off just as fast.

This high heat will quickly melt previously

soldered connections for removal of parts

or wires.

Most soldering iron tips are pretinned.

That is, the tip has been "wetted" with a thin

film of solder. When the iron heats, the

solder melts and transfers heat to the sur-

faces that are to be soldered. Unless you are

using a plated tip, it may be necessary to re-

tin the tip from time to time. The tinning

process is similar to that of soldering. The

tip (or surface that is going to make contact

with the metals to be soldered) is cleaned

of oxides by scraping, filing or with fluxes -

then solder is applied to the cleaned tip.

Once a thin film of solder is formed over the

tip, excess solder is wiped off.

A popular misconception is that the watt-

age of a soldering tool is the most important

characteristic to look for when considering

a new purchase -it's not.

Tip Temperature. Far more important is

the heat available at the working end of the

soldering iron. This is directly related to

the shape and size of the tip and how . the

heat is applied to the working end.

Different designs of the heating elements

have great effect, too. Some of the 60 -watt

economy -type soldering irons are no hotter

than the 231/2 -watt combination element -tip

units that thread into their special handles.

Probably the best example of the relation of

ELEMENTARY ELECTRONICS

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tv-

Most electronics kits can be built with these few

hand tools and a soldering iron. Ruler, at fop,

is used to measure lead lengths. Small screwdriver

is used mostly for tightening knob setscrews.

design to tip temperature is the catalog data

for one brand element.

When the tip and element are made in one

permanent unit, the 231 watt tip (depending

upon shape) teaches a temperature of 650°

to 700 °F while the same wattage element

with a thread -on tip is rated between 600°

and 650 °F. This 50 °F difference can be

quite important when working in an area

that is cool or drafty.

Heat Transfer. Getting heat to the joint

to be soldered is the most important part of

the process. A clean hot iron will transfer

heat the fastest. Clean does not mean dry -

clean means free from oxidization and

charred flux. For maximum heat transfer in

the shortest possible time the tip must be

wet with solder -this makes better contact

between the tip and the joint.

To some extent a low -heat soldering iron

can damage more components than a mod-

erate -heat iron. The faster a joint heats the

less time the heat has to be applied. With a

sufficient heat (and soldering experience)

you can solder a joint and get the soldering

iron away before the heat has a chance to

creep up the lead. Take a good look at that

production -wired printed- circuit board -

there just isn't any space to get a heat sink

on the component leads. Besides, most heat

damage to transistors and diodes occurs only

when current is flowing through them -just

make real sure that they have cooled off com-

pletely before you apply power to the circuit.

Wiring And Soldering. The service

centers of kit manufacturers spend much of

their time unscrambling home kit builder's

butchered wiring and soldering. Except for

not following instructions precisely, poor

soldering is the major cause of kit failure.

And it has proven by actual record that a

,TIILY-AIIGIIST, 1966

Soft -plastic tool (lower left) is used to start nuts

in difficult places. Nutdrivers (socket wrenches) do

an expert job of tightening. Wire strippers are

adjustable. Slip -joint pliers are often handy, too.

sloppy kit- wiring job goes hand in hand

with intermittent or poor performance. In

any case, the poorly wired kits seem to find

their way into the service shops more often.

The following steps may seem quite basic,

but they can't be over- emphasized:

Wiring must be mechanically secure on

the terminal before applying heat or solder.

Pass the wire around and through the termi-

nal, then crimp it with needle nose or long

nose pliers. Clip off any excess lead length.

Make certain not to drop the wire bits back

into the chassis. Small lengths of wire make

excellent shorts between power leads and

ground.

Apply heat to the terminal, not just to the

wire. The soldering -iron tip should be placed

on the joint so that heat will be transferred

through the terminal to the wire. Use the

correct amount of heat. Too little heat can

cause a cold -solder joint (poor electrical con-

tact), and will cause the solder to appear dull

or crumbly after it has cooled. The correct

amount of heat produces a bright solder

connection. Naturally, too much heat, ap-

plied too long, will damage surrounding

parts. Some solder must be applied to the iron -

too much can run into the terminal before

it's properly heated. This can cause 'either

poor electrical connection, or a cold -solder

joint, or both. It goes without saying that you

must use a good grade of rosin core. (To re-

move excess flux clean the connection with a

small stiff -bristle brush dipped in a non -in-

flammable solvent, immediately after the

connection has cooled.)

Once you have mastered the basic solder-

53

www.americanradiohistory.com

54

®/@ BUILD 'EM GOOD

Resistors and capacitors above are neatly positioned.

Often this is not practical in high- frequency work

where leads must be kept as short as possible or cut

to an exact, specified length to prevent trouble.

Jumble of parts (below) looks like someone dropped

a handful out of a bog. Excessive lead lengths

help create short circuits and often break easily

from vibration. There is no excuse for sloppiness.

Carefully checked and placed kit components are easy

to find and less likely to be lost or damaged.

Cabinet, dial parts and knobs are left wrapped until

all other work is finished -this prevents scratches.

ing theory and technique, you are well on

the way to becoming a good craftsman in

the art of electronic construction. Here are

some additional tips that should make life

a.lot easier on your next construction job.

Follow Instructions. This is one rule that

those experienced in electronics (engineers,

technicians and old -time Hams) often break.

They often start at Step 15 or so, instead of

Step 1. The kit manufacturers go to great

lengths to - prepare the instruction manuals

so that all parts would be mounted and wired

Some of the many types, shapes and styles of com-

monly used capacitors. Individual units are described

or illustrated by kit manufacturers to prevent the

mistakes possible by selecting wrong unit.

in a specific order. (The same is true of

many construction articles found in maga-

zines.) By not following this order, you find

that some particular part will not quite fit as

indicated in the instructions. So you stick it

in at the next best spot. The kit may work

that way, but the net result is a jumble of

parts that mark the unit as home -made.

Have A Place For Tools. Select all of the

tools you will need before you start. Lay

them out in a readily accessible spot on the

work bench (unless you have a peg board or

rack for. them). Do not mix tools in with

the kit parts. Once you have used a par -

ticular tool, lay it back down (or hang it

up) in the same place. This will not only

make life easier, but it will prevent a kit part

from being scraped by a screwdriver blade.

Protecting Parts. Don't dump all of the

parts into one big box. After you have

checked parts against the packing list, set

aside those that will not be used right away -

remove them from the work area. Group all

ELEMENTARY ELECTRONICS

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WRONG! Sloppy work (be-

low) will give a /ot of heart-

ache. Shorts and intermittent

operation will give poor

results that are often blamed

on kit manufacturer since

constructor will seldom admit

to faults being in work.

Side view of printed- circuit

board (above) shows IF

transformer, resistor and

capacitors properly

inserted. Leads are bent

slightly to prevent

components from falling

out before soldering.

Solder -then trim leads.

of the remaining parts by type (resistor, ca-

pacitor, etc.) Note the recommended method

of using the edges of a corrugated carton

(shown in photo) for parts storage during

assembly.

Make certain that you know the electrical

values of all parts. This is necessary even

with kit parts, but is especially important

with home -brew construction.

Resistor Values. Resistors are identified

as to value and tolerance by color-code

bands. Kit instructions usually explain the

color -code system. Sometimes, however, the

bands are not clear, or have been rubbed off

(or you might even be color blind without

knowing it). To better learn the color -code

check all resistors with an ohmmeter. If you

plan on much electronics building in the fu-

ture, you will find that an ohmmeter (com-

bined with a volt and milliammeter -a multi -

tester or VOM) is a handy instrument to

have, and well worth the small investment.

Fixed capacitors may be identified as to

value by a color code similar to that used

for resistors although most capacitors are

stamped as to value and tolerance. If these

markings are not clear, it will be necessary

to check the capacitor on a capacitance

bridge. Once identified, the capacitors should

be marked -with a pen, grease pencil or on a

tab of adhesive -backed tape.

Check for Polarity. Electrolytic capacitor

leads are marked as to polarity (+ or -) .

Unlike most other types of capacitors, the

leads of an electrolytic must be connected

as indicated in the instructions. If not, the

equipment will not operate properly, and the

JULY- AUGUST, 1966

Pigtail leads are cut at short arrows. Long arrows

indicate distance between terminal lugs. Allow

some lead length for dressing components for neater

layout. Use sleeving or spaghetti where needed.

capacitor will most likely be damaged.

Batteries are clearly marked as to polarity,

too. However, instructions sometimes re-

quire that you connect leads to battery termi-

nals and then route the leads to other con-

nections. This can cause confusion if the

leads are not tagged (at the open end) when

first connected to the battery. A small strip

of masking tape makes a good tag since it

can be removed easily once the lead is sol-

dered in place.

The Outside. Since a finished project is

going to become part of your home decora-

tions, its outward appearance is just as im-

portant as proper operation. That quality

look can be achieved, or preserved by using

a little extra care during assembly.

The outside parts (panels, cases, etc.) of

kits are usually given extra protection when

packed for shipment. Since these parts are

not required until the last steps of assembly,

they should not be unwrapped and left ex-

55

www.americanradiohistory.com

56

@AD BUILD 'EM GOOD

posed to hot soldering irons and sharp tools.

Leave such parts in their wrappings, and

store them away from the working area.

Use the correct mounting hardware, and

in the correct assembly order! Although this

may seem obvious it's often overlooked and

it is usually not spelled out in magazine con-

struction articles (they assume that you will

know the right way to do it!). Properly pre-

pared kit instructions call for a flat washer

under the attaching nut of panel- mounted

controls. Lockwashers, if any, are placed

on the control -shaft bushing behind the pan-

el. If a lockwasher is used outside, its prongs

can crack, gouge or otherwise scar finished

surfaces.

Leads are bent slightly to keep component body

perpendicular to tie strip. Lead to tie -strip lug

is wrapped -lead to smaller tube -socket lug

is not. Close spacing makes shorts more likely.

Never use pliers to tighten control mount-

ing nuts against the panel! This is a very

common fault, and even the old timers are

guilty. It's quite human to get used to . a

particular tool, and use this tool for every-

thing. Unfortunately, pliers were not de-

signed to tighten nuts. One slip, and you'll

have a gouge or scratch that can't be covered

up easily. And if it happens to be the front

panel you'll have a permanent record right

out where everyone can see it.

A socket wrench of the correct size should

be used to tighten nuts, both inside and out.

But it is of particular importance for nuts

which tighten against the outside panels. Do

not over -tighten nuts, and do not press on

the socket wrench, scraping against the panel

while turning.

Although few people are ever going to

look inside your kit or other construction

project, the mark of a good craftsman is neat

work -both where it does and does not show.

. s-t7se

Sleeving or spaghetti is used on one lead to prevent

its touching other tie -strip lug. Where practical,

dress leads to prevent soldering -iron damage that

can occur if it's ever necessary to replace part.

Signal -carrying leads should be as short and direct

as possible. Power leads, both AC and DC, can be

squared off and kept away from low -level signal points.

Besides, proper placement of parts and wire

routing can improve performance. Improp-

erly routed wires can cause hum pickup and

signal loss.

Kit instructions are usually quite specific

on the method of mounting components.

They usually caution you to make sure the

(Continued on page 112)

ELEMENTARY ELECTRONICS

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B/B COMMUNICATIONS

HARTMAN MODEL MC -62

SW /Solid -State

Ship -to -Auto Converter

For no other reason -other than it's logi-

cal -one would assume that what takes place

on the marine frequencies is of interest only

to someone on a boat. However, this is not

always the case. Just as SWL's (short -wave

listeners) like to hear what's going on in the

world, boat enthusiasts like to know what's

going on even when they're not cutting a

wake through King Neptune's domain.

Many times a lot of aimless preparation

and sailing is saved by hearing the marine-

band chit -chat -about good fishing grounds,

choppy seas, or a bunch of juvenile delin-

quents with a 100 -hp. motor on the back of

a rowboat -while driving to the boat yard.

For just this purpose (eavesdropping on

the marine band), Hartman, a manufacturer

of marine radiotelephones, makes available

a Ship -to -Auto Converter Model MC -62.

The MC -62, priced at $19.95, is a solid -

state device which converts a standard AM

auto radio into a marine -band receiver. It

is powered by a built -in 9 -volt battery, so it

can be used with any auto radio (tube or

solid- state) and with any auto battery voltage

or polarity. Other than the antenna connec-

tion, the MC -62 requires no direct connection

to the radio or the auto's electrical system.

Stow It. The Hartman MC -62 mounts

under the dash with a single screw which

is factory attached to the cabinet. To use it,

you simply unplug the antenna cable from

the radio and insert it into the matching an-

tenna jack on the rear of the MC -62. Then

you connect a supplied cable between the

MC -62's output jack and the auto radio's

antenna jack. Finally, you adjust the radio's

antenna trimmer (an accessible user adjust-

ment) for maximum sensitivity. The power

Jut.Y-Auevsx, 1966

so,, ro

sure

6N

Y1tvAY4Mli YNN.' . .. ..

n ss 18 ss il@ IN t00

2000 71I

IS7U

I830

rARfNf OPERATOR

MARINE FREQUENCIES Men Mc-62

1883

1182C0

switch determines whether the converter or

the antenna is connected to the radio. (The

converter does not interfere with normal

radio reception.)

Unlike many converters, the Hartman

MC -62 is not tunable: the AM radio is used

to tune the marine band. The MC -62 is a

broadband device with its oscillator fre-

quency fixed at 3.5 mc. Marine -band fre-

quencies beating against the 3.5 -mc. local

oscillator produce a difference frequency

which falls in the AM broadcast band. For

example, WWV at 2.5 mc. beating 3.5 mc.

has a difference of 1,000 kc. Therefore, if

the user tunes the auto radio to 1,000 kc.

he will hear WWV (which originally started

out at 2.5 mc.). Similarly, any signal on the

marine band between 2 mc. and 3 mc. will,

by beating against the 3.5 mc. oscillator,

appear at a standard broadcast frequency.

Mounted under the dashboard with a single wingnut

the Hartman MC -62 can be installed by anyone. Only

wire connections it requires are for the antenna.

57

www.americanradiohistory.com

SHIP -TO -AUTO

CONVERTER

The MC -62 has a front panel chart (made

to look like a slide -rule dial) which lists the

common marine frequencies -including the

marine operator -at their broadcast -band

dial settings. For example, if you were in-

terested in hearing 2830 kc., you would check

the chart and determine that it falls between

60 (600 kc.) and 70 (700 kc.) on the AM

radio dial. Tuning the radio to this setting

would bring in 2830 kc.

Performance. The Hartman MC -62 did

exactly what it's supposed to do. We picked

up the marine band with average sensitivity

(comparable to inexpensive SW receivers).

There was no noticeable leakthrough of

broadcast signals. Though atmospheric in-

terstation noise was somewhat high, this is

true of any receiver not equipped with a

noise limiter (a limiter can always be added

to the auto radio).

Our unit pulled exactly 0.4 ma. from its

battery, indicating that the battery should

Readily available transistor -radio battery powers the

solid -state circuitry of the Hartman MC -62 converter.

Jacks are for auto -radio antenna and jumper to radio.

last its normal shelf life of 6 to 12 months

even with frequent use.

The MC -62 cannot be used to convert a

table radio (or any loop antenna equipped

radio) to the marine band, as just the shortest

exposed antenna lead will result in severe

broadcast signal leakthrough. The STAC

requires the complete antenna system shield-

ing common to auto radios.

For additional information write to Hart-.

man Marine Electronics Corp., 30 -30 North-

ern Blvd., Long Island City, New York

11101. While you are at it, ask them to send

information and specifications on their com-

plete line of converters.

BLOCK THAT LEAK

Checking the DC resistance of a capacitor

using the high -ohms range of a .VTVM is

often unrevealing due to the low voltages

used in the meter circuit. The DC resistance

may be unacceptably low when tested at high

voltages.

Coupling and bypass capacitors are easily

checked for leakage using a DC voltage

range.

In the diagram, the DC voltage appearing

across Rg is due to leakage through coupling

(or blocking) capacitor C and any grid cur-

rent that may flow through the grid resistor.

Remove V2 to prevent grid current and

measure the voltage across Rg using a low

DC range of the VTVM.

For a more stringent leakage test discon-

nect C from Rg and connect the VTVM to

the free end of C. You can calculate the

equivalent DC resistance (Rc) of C at test

voltage Va, by formula: Va - Vb

Rc = Rm Vb

Where Rm equals the input resistance of

the VTVM and Va and Vb are the measured

DC voltages at points A and B.

Reject capacitors giving erratic readings,

as these introduce noise and instability into

the next stage.

Coupling or blocking capacitors in TV

horizontal and vertical oscillator and output

stages, video output, DC restorer and sync

stages produce a host of troubles when leak-

age is erratic or high.

Consider its function in the circuit before

you reject a capacitor. For example, paper

and ceramic bypass capacitors shunted across

relatively low -value cathode resistors need

not meet the very -low leakage needed for a

blocking use.

VI

Vacuum -tub,, voltmeter connec ed at point B to meas-

ure DC voltage due to leakage through capacitor C.

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

Breaking

the

Crysta

Barrier

by Robert E. Reiland

JULY -AUGUST, 1961

Simple 1- transistor

amplifier boosts the

weak audio output.

Heathkits' popular crystal

radio, the CR1, has probably

been a major contributing

factor in getting many people

initiated into the field of

electronics. The radio has

excellent selectivity, but its

sensitivity, like most all crystal

sets, leaves much to be desired.

The addition of a single stage

transistor amplifier to the

radio will increase the vol-

ume of weak stations and

will enable you to "operate"

with a shorter antenna. Full

details for making the modi-

fication are given in this

article.

Only a few inexpensive

electronics parts

59

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60

if')o

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

Complete circuit of

modified Heath CR -1 kit.

Crystal -type phones

can be used across points

A and 8 but phones of

2000 to 5000 -ohms resist-

ance are required for

collector circuit.

ANTENNA

RF TRANSFORMER

Ll iii

CRYSTAL DIODE

DI + C5

C2 A .01MF

365MMF

Soldering gun is

heating coil lug.

Emitter lead has a

heat sink to prevent

overheating junction

inside transistor

even though lead is

special low -heat-

conductance alloy.

AMPLIFIER

INPUT

HIGH - IMPEDANCE

PHONES

(see parts list) are all that's needed to

make the modification. No chassis drilling

or cutting is required, so it shouldn't take

the most wary experimenter any more than

a couple of hours to complete the job. The

exterior appearance of the radio is not

changed in any way as all new parts mount

neatly inside the case.

The modified schematic is shown above;

pictorial diagram shows arrangement of

parts. As you can see from the photos and

pictorial a few of the existing components

must be shifted around to make room for

connecting the new ones.

First move the grounded end of capacitor

C4 from the grounded phones jack over to

the ground lug of the Gnd jack. The

grounded end of. L2 is shifted at the same

time to the same lug. Crystal diode D l is

unsoldered from the Phones jack lug and left

free until the terminal strip is mounted.

The grounded Phones jack and its asso-

ciated soldering lug must be insulated from

ground. This is the most important step.

However, this is an easy task, as you follow

JULY -AUGUST, 1966

GE2

PARTS LIST

B1 -1.5 -volt dry cell (AA -size penlight cell)

C5- .01 -mf. disc capacitor

Q1- Transistor, p -n -p audio (General Electric

GE2, 2N107, 2N241A, 2N404, 2N525A or

equiv.)

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

Misc. -Terminal strip; #6 flat fiber washer,

wire, solder, etc.

Estimated construction cost: $2.00

Estimated construction time: 1 hour

the same procedure used to insulate the other

jack when you first constructed the Heath

CRI, that is, you mount a flat insulating

washer between the chassis and the lug and

secure the assembly with the nut. An insu st-

ing washer is already provided on the top

side of the chassis. Make sure the jack and

lug are insulated from the chassis. (You can

test with an ohmmeter -meter prods placed

between the lug and ground should give an

infinite -resistance reading on the meter.)

The three -tier upright terminal strip is

mounted next. Remove the retaining nut

61

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BREAKING THE

CRYSTAL BARRIER

Original Heathkit CR -1

Crystal Receiver will

not look any different

after the paris in

front of it are wired

into the existing

circuitry. All parts

are shown except

insulated washer and

the few short

lengths of wire needed.

from the second phones job (which is al-

ready insulated from ground) and mount the

terminal strip between the soldering lug and

the fiber washer. The lower lug on the ter-

minal strip may be removed as it is not used

in this modification.

The AA penlight cell is soldered into the

circuit and is supported by a piece of heavy

copper wire. There's plenty of room to mount

a battery holder, but this will mean drilling

mounting holes. Besides, when the battery

is expended it is only necessary to unsolder

it and solder in a fresh one. When soldering

in the battery you will find it easier if you

first clean the ends of the battery with sand-

paper or steel wool.

You can now start soldering in the other

parts. The main thing to be careful with here

is the transistor and diode; use a heat sink to

prevent any damage to them. Follow the

pictorial and photos and the job should be

finished in short time.

Put the radio back in the case, attach the

antenna and phones. You'll be receiving sta-

tions with much more volume -you may

even hear some new ones. To turn the radio

o)i remove one of the headphone pin tips;

62

I.SV TERM. STRIP

Power switch is not needed. Transistor draws

little current and disconnecting headphones opens

the circuit preventing all current drain from

single penlight cell that is sole source of power.

a separate switch thus won't be needed.

Of course this amplifier can be added to

any crystal -radio circuit, like that sold by

Allied Radio as catalog number 85U024

AMW or to your favorite home -brew set. Just

connect the amplifier input (points A and B)

to the earphone connections and tune the set

the way you always have. Good listening!

ELEMENTARY ELECTRONICS

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There's a lot of

bounce in those DX

signals- here's why!

The

Angles On

DX

by C. M. Stanbury II

Originally DX simply meant distance and even today,

when DX now means rare or unusual reception, distance is

still an important factor. "Of course!" you say. But it's not

quite that simple. For example, below 7 mc. a radio station

2500 miles away can be easier to log than one which is

1900 miles away. No, to cope with distance, a straight line

approach won't do. You must play the angles.

But let's start at the beginning and that beginning is the

ionosphere, the four layers of ionized gasses which surround

the earth. As many of our readers already know, it is these

layers which reflect radio waves back to, and around the

curvature of, the earth. If it were not for the ionosphere,

there would be no radio reception beyond the horizon. A

more detailed picture of the ionosphere layers above the

earth appears in the illustrations.

It should be noted that every time a radio wave tangles

with the ionosphere, it's not only reflected (at least we hope

it's reflected) but also weakened. (Technically, the signal

(Continued Overleaf)

JULY- AUGUST, 1966 63

www.americanradiohistory.com

(Di@ ANGLES ON DX

Roughly these are the

positions of the layers

during the day and at

night -they are not to

scale. F layer is low

during the day and

rises at night. E layer

does not always exist

in a given area. Bends

or ripples in the layer

act like curved mirrors

fo concentrate or spread

reflected signals.

F LAYER

res- 222 N!,

DAY

F2 LAYER

F3 LAYER

035 -145 H1)

spoRAO(G E LAYER

(55 -65 MI)

layer- anyhow the received signal is weak-

ened when it tangles with the ionosphere.)

Therefore, when transmitting from one point

on the earth to another, the signal should

strike the ionosphere as few times as possible.

Or, putting it another way, there should be a

minimum of hops or reflections.

For geometric reasons, due to the height

of the reflective layers and the earth's curva-

ture, the maximum single -hop distance is

about 1900 miles. On the basis of this (ig-

noring the antenna height and averaging the

layer height), radio stations of the same ef-

fective radiated power (e.r.p.) that are lo-

cated between 1500 and 1800 miles away

should be received with about the same signal

strength but a transmitter of the same e.r.p.

2000 miles away (beyond the 1 -hop limit)

will be noticeably weaker as are stations less

than the 1500 -mile distance that cannot be

received by a direct or ground -wave signal.

Therefore a station outside the 1 -hop area is

Angles of Arrival Via the F layer

Angle

(deg.) Hop Length

(miles) Angle

(deg.) Hop Length

(miles)

5° 1900 8° 1575

6° 1772 9° 1500

7° 1650 10° 1400

an even betterDX plum; for this station will

be a rare one in your area.

All Hopped Up. This 1500 to 1800 -mile

distance figure is for reception via the F lay-

er at night. This is the only layer which reg-

ularly affects reception during the hours of

darkness. During the daytime there are ac-

tually two F layers (F1 and F2) and, even

more important, an E layér.

If radio wave reflection takes place via the

E layer, maximum hop distance is only 900

miles. Under certain abnormal conditions

the E layer does not dissolve with the coming

of night. Such a sporadic E layer is even

capable of reflecting VHF signals. Thus, 900

miles can also be considered a step on the

DX ladder -for VHF.

The Angle. Both our barriers of 900 and

1800 miles are based on an angle of arrival

of 5 degrees above the horizon. The longer

the hop the smaller the angle of signal ar-

(Continued on page 114)

IONOSPHERE F LAYER

RADIO WAVES

61

This drawing is nearer to scale.

At too sharp an angle the radio

waves pass through layer -too

shallow angle and reflections

do not return to earth.

Although it's not to scale this

will give you an idea how

waves can bounce from either side

of ionized layers for DX.

ELEMENTARY ELECTRONICS

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0/8 COMMUNICATIONS

KNIGHT -KIT SAFARI I.

23- Channel, 5 -Watt

CB Transceiver

While Knight -Kit's Safari I (Allied Radio)

CB Transceiver is another of the so- called

high -performance rigs, for a change, high -

performance really refers to performance in

measurable terms, rather than a slew of gen-

erally unneeded features and fancy chrome

plating, for the Safari I includes not a single

useless feature; every single feature con-

tributes directly towards better communica-

tions. What's in the Box. The Safari I is fre-

quency synthesized to cover all 23 channels

on á single selector switch. While frequency

synthesis does not mean one iota of better

performance, it does, because fewer crystal

are needed for complete coverage, result in

considerably reduced cost. Naturally, the

receiver uses double conversion with two

stages of 455 kc. IF amplification. A front

panel ANL (automatic noise limiter) on -off

switch is provided as well as a PA (public

address) on -off switch which allows the

transceiver to be used as a PA amplifier. A

terminal strip is provided on the rear apron

for the external speaker. The S -meter doubles

as a relative RF output meter when the trans-

ceiver is switched to the transmit mode.

To insure reception of received stations

which may be off the center channel fre-

quency, a front panel control allows the re-

ceiver to be tuned 1 kc. off -channel.

Wired In Quality. Most of the extras

have gone into the transmitter, in fact, into

the modulation. The mike is a rather good

quality noise -cancelling type. A front panel

microphone gain control is provided which

adjusts the microphone sensitivity from full

oll to at least twice as sensitive as the aver-

age transceiver.

In short, whether you roar like a lion or

squeek like a mouse you can tailor the mike

gain to your specific need.

Two modulation indicators are provided,

and unlike other modulation indicators which

simply flicker to indicate you're talking, the

Safari I's indicators are calibrated. The Nor-

mal modulation indicator goes on only when

the percent modulation reaches 50 %. A red

Overmodulation lamp flickers only when the

percent modulation exceeds 85 %. (For all

practical purposes 85% modulation equals

100 %.) Maximum undistorted modulation

is obtained if the mike gain control is ad-

justed so the 50% lamp is on most of the

time while the 85% lamp flickers occasion-

ally. To avoid sideband- splatter and its inter-

ference, caused by overmodulation (in ex-

cess of 100 %), the modulator limits the per-

cent modulation to slightly less than 100%

regardless of the sound level into the mike or

the setting of the microphone gain control.

Performance. While anyone can build -in

the features required for high -performance,

it's another thing to actually get it. But the

Safari I actually delivers all the performance

built into it.

Transistors on back panel are for the DC power

supply -no vibrator is used. TVI trap will

make operator popular with local TV sef owners.

CRYSTAL BANKS

12 VOC

POWER SUPPLY

TRANSISTORS

JULY-AuCUSx, 1966 65

www.americanradiohistory.com

(DM KNIGHT -KIT SAFARI I

Finger points to calibrated

overmodu/ation lamp which

indicates when modulation

peaks exceed 85 per cent.

Control to the right of

the microphone connector

adjusts mike gain from full

on to full off.

FUSE

ANL SWITCH r PA SWITCH

MIC GAIN

CONTROL

S -METER ZERO ADJ.

EXTERNAL

SPEAKER

TERMINALS TRANSMITTER

TUNE

Measured input sensitivity for a 10 db

signal + noise to noise ratio (a much

tougher test than just signal to noise or usable

sensitivity) was 0.65 microvolts at the an-

tenna terminals (anything lower will pick up

Mars' probes). Adjacent channel rejection

through the front end was -42 db on both

sides of center channel -better than the

Knight specs and indicating a good, balanced

IF amplifier design. Image rejection, again

better than Knight's specs, was -53 db. AGC

action, indicating the difference in output

level, for a change in input signal of 54 db-

representing an increase of signal strength

from 2 to 10,000 microvolts -was 11 db. (In

practical terms meaning that if you have the

gain cranked open to hear a weak signal you

won't be blasted out of your seat if a very

strong signal comes on the monitored

channel.)

RF output into 50 ohms was 2.4 watts; the

transmitter's pi -net tuning controls are on the

rear apron. Modulation was exceptionally

clean with no trace of distortion (on an oscil-

loscope) up to the test value of .85%

modulation.

Summing up Performance. As you can

see, not only is the Safari I's performance

good (if not outstanding, but in almost all in-

66

NORMAL

MODULATION LAMP MODULATION LAMP

OVER

Terminal strip al extreme left is the remote

speaker output. Transmitter is tuned

by adjusting two pi- network capacitors through

holes at right. Power plug permits rapid

conversion from 12 -volt DC fo 115 -volt AC.

stances Knight's claims are pessimistic, and

our test unit actually outperformed the specs.

The only negative aspect we could find was a

slight residual loudspeaker hum (but no

modulation hum); though not unusually high,

it can be somewhat distracting in a very quiet

room. However, once a signal breaks the

squelch the hum is "buried" under the re-

ceived signal.

Construction. Instead of commenting on

the construction we'll report on an unusual

"test." The unit was severely damaged in

transit from workbench to test lab, and the

entire panel was stove in. Even with a ham-

mer we could not straighten the panel or the

speaker mounting to original form without

leaving a few scars and scratches. Yet this is

the same unit that delivered the performance

given above. (We can't think of a better

testimonial.)

What you get. The Safari I is supplied

with 23 channel coverage and both the AC

and DC cables. (The 12 VDC supply is

solid- state, no vibrator.) Also a gimbal

bracket for mobile mounting or tilted base

mounting. It is priced at $129.95 in kit

form. For additional information, write to

Allied Radio, Dept. 20EE, Chicago, Illinois,

60680.

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

SCR

Slot Car

Starter

by Herbert Friedman This electronic

referee will

settle your

Slot -Car race

starting disputes

as quick as a

wink

ASURE WAY to create an argument is to

call out Ready, Set, Go when starting a

race. First thing you know someone yells

"You fudged "; another claims you didn't

start the stopwatch in time, or someone -to

be polite -will say, "I didn't hear you say

go." And if you do any serious slot -car rac-

ing, where a split second makes the differ-

ence between winning and losing, you know

that every race leads to an argument. But all

the arguments are really unnecessary if you

steal a trick from the commercial drag strips

and use a starter -in this instance RAnto -TV

EXPERIMENTER'S SCR Slot -Car Starter -to

start your slot races.

The SCR Slot -Car Starter is an automatic

device that signals when the race begins. If

anyone "jumps the gun" a penalty light goes

on to indicate that someone has cheated. The

exact penalty should be settled before the

racing begins. Either the culprit can be

banned from the track (rather severe pen-

alty), can be fined one lap, or can be penal-

ized one or more car lengths for the next

race. To avoid disagreements over whether

the Start signal is early or late the entire

control -from Start signal to penalty light -

is automatic. When S2 is set to the Time posi-

tion the Mark light goes on. After about 2

seconds the Ready light goes on; and finally,

after another 3 seconds or so the Go light

illuminates. If any car attempts to roll be-

fore the Go light a Penalty light goes on in-

dicating which track jumped the gun. At the

JULY- AUGUST, 1966 67

www.americanradiohistory.com

68

SLOT -CAR STARTER

instant the Go light flashes on the penalty

circuits are locked out. In short, there is no

more room for human error. If you get a

Penalty light you cheated -it's that positive.

To avoid having the slot racers anticipate

the timing of the Start light the time sequence

between Mark and Ready is shorter than

between Ready and Go. The slight hesitation

before the Go light goes on is deliberate, so

don't attempt to change the timing circuits

so Ready and Go have the same delay. Many

is the racer who is going to mentally time

the Go signal only to find he's earned a

penalty.

The unit shown will accommodate any

slot track using a 10- to 18 -volt power sup-

ply. If your track uses a track voltage lower

than 10 volts simply change K2 and K3 to

their 6 volt equivalents and substitute 6 volt

lamps for I4 and I5.

Construction. Note that there is no com-

mon connection to the metal cabinet. For

maximum safety, since the circuit is con-

nected directly to the AC main, be absolutely

certain no wire or component touches the

metal cabinet.

The unit shown is built in a Bud SC -2132

Cowl Type Minibox, which, like all other

components used in this project, is standard

stock from Allied Radio. Since parts layout

is not critical any other type of housing can

be substituted.

D.p.d.t. relay K1 may be rated either 115

VAC or 115 VDC, whatever you have or

can get. If you use the DC relay, diode D8

must be used; if you use a 115 -VAC relay,

eliminate D8. Diode D8, like diodes DI to

D7, can be the cheapest diodes you can get

-as long as they are rated a minimum of

200 PIV at 400 milliamperes.

Relays K2 and K3 are the 12 -volt DC

models for slot tracks having a 10- to 18 -volt

DC power supply; use their 6 volt equiva-

lents if the track uses 10 volts or less. Either

way, a Potter & Brumfield (P & B) type

RS5D relay is used, and since their wiper

contact is common to the mounting frame

they must be insu'ated from the cabinet.

Mount the relays on a piece of perforated

wiring board, as shown, then mount the

board in the cabinet with '/4 -inch insulating

spacers between the board and the cabinet

at each mounting screw.

Neon pilot assemblies I1, I2 and I3 are

cttikst'

I I4 K3 K2

T81

K1

SCR2

D6

D?

St

DS

SCRI

01

04

Only K2 and K3 are mounted on the perforated

phenolic. Other components are wired to

terminal strips attached to base of metal

cabinet with machine screws. Additional

perforated -phenolic board can be used to hold

the resistors, capacitors, diodes and SCRs

wired to terminals inserted in the perforations.

Other -end view of the completely wired Starter

(above, right) shows rest of components.

Both /4 and IS should be positioned so that

filament of lamp is centered on pilot jewel.

PARTS LIST

C1 -2 mf., 450 -WVDC electrolytic capacitor

C2-4 mf., 150 -WVDC electrolytic capacitor

D1- D8-400 ma., 200 PRV (PIV) or higher

rating rectifier diode

I1, 12, 13 -Neon pilot lamp (see text)

(Snaplight, Allied Radio 7U758 or equiv.)

14, 15 -12 -volt pilot lamp (type 1487, 18151

K1- D.p.d.t., 115 -vac relay (Knight, Allied

Radio 74U657 or equiv., see text)

K2, K3- S.p.d.t., 12 -vdc relays (Potter 8

Brumfield RS5D, Allied Radio 75U504 or

equiv., see text)

R1 -100 -ohm, 1/2 -watt resistor

R2- 330,000 -ohm, 1/2 -watt resistor 3

R3- 220,000 -ohm, 1/z -watt resistor

R4, R5- 1,000,000 -ohm, 1/2-watt resistor

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

52-4 p.d.t. rotary switch (Mallory 3242J or i

equiv.)

SCR /, SCR2- Silicon controlled rectifier C68

(General Electric)

TS1-4 or 5 terminal (screw type) barrier strip

1 -3 x 8 x 6 -inch cowl -type chassis box (Bud

SC -2132 or equiv.)

Misc.-Pilot lamp assemblies; perforated

phenolic board; terminal strips; assembly

hardware; wire; solder; etc.

Estimated Construction Cost: $18.00

Estimated Construction Time: 6 hours

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

1{f

SCR2

K1

TSf

K2

shown in a box in the schematic diagram be-

cause they come with built -in current limit-

ing resistors. If you attempt to cut costs by

using standard NE -2 lamps, make certain you

connect a 100,000 -ohm series resistor.

Switch S2 is a 4.p.d.t. rotary -do not

substitute two separate D.p.d.t. switches as

all circuits must be activated simultaneously.

Note the connections carefully; all circuits

shown in the schematic are in the Standby

1

117

VAC

II

D2

RI I+

00r

+ D1

r

R2

330K

+e

1

I21

1

S2B SCRI a

position. For clarification, to avoid wiring

errors: S2A turns on the Mark light while

S2B and S2C activates the Ready and Go

timing circuits (do not attempt to save on a

switch by connecting the S2B and S2C cir-

cuits together; it won't work). S2D closes

the penalty circuit and then clears the Penalty

lights when S2 is reset to Standby.

The penalty lights, I4 and IS, are 12 -volt

types for tracks using 10- to 18 -volts and the

6 -volt type for tracks using under 10 volts.

Whether they are screw or bayonet base

doesn't matter as long as they match the

lampholder. However, in the 12 -volt type

it is easier to obtain a bayonet base, so fig-

ure this in when ordering the parts.

The connections shown to terminal strip

TS1 are only for clarification. The exact

layout of the TS1 connections will be de-

termined by what is most convenient for

your track layout.

To avoid soldering -heat damage make cer-

tain you use a heat sink when soldering to

the diodes and SCRs.

Connecting to the Track. First, note that

at TS1 the two main leads from the slot car

power supply are labeled A and B; this is

for wiring reference only and has no rela-

tionship to the actual polarity of the power

supply. The B connection is that power

supply terminal connected to the common

track connection -whether it is actually posi-

tive or negative doesn't matter; you are only

D +

R4 k

+

r

D5

* RES STORS PART OF LAMP

ASSEMBLY - SEE TEXT

a

(GROUNDED TO CASE)

Lead connected to 3 on TSI is A lead -B lead connects to 4. Relays isolate track from SCR circuitry.

JULY- AUGUST, 1966 69

TRACK. TRACKs2

SLOT -CAR

POWER

SUPPLY CONTROLLERS

TO TRACK

COMMON

4

D8 +

T

KI

- S2D

K2

K3

I4

I5

TSI

www.americanradiohistory.com

SLOT -CAR STARTER

`K3

Relays K2 and K3 are mounted on perforated

phenolic because frame is electrically connected

to the movable contact on the armature.

Rear view (top, right) shows location of

power on -off switch and terminal strip TS1.

SI could be installed on front panel.

Front -panel layout (right) is uncluttered.

S1 could be mounted to the right of S2. 14 I5

Hi.

SI TSI

concerned with that it goes directly to the

tracks (one leg of track #1 and one leg of

track #2). The A connection is whatever

power supply terminal is connected to the

controllers. The controller connection, TS I

terminals 1 and 2, are connected after the

controllers where they are attached to the

track (generally at the track connecting

block); do not cut into the controller wiring.

The connections from TS1 terminals 3 and

4 go directly to the slot -car power supply.

Checkout. Set power switch Si to Off,

S2 to Standby (the position where S2A is

on the unused terminal) and plug PLI into

the AC outlet; then turn Si On. After a few

seconds turn S2 to Time. The instant S2 is

closed D. should light; after a couple of sec-

onds I2 should light; and after another three

seconds or so, 13. If all three lights go on at

once check for a wiring error, particularly

reversed polarity on diodes D4 and D6. If

I3 lights before 12 either Cl and C2 are

interchanged or R4 and R5 are interchanged;

or, you have reversed the 12 and 13 mounting

positions.

If 12 and 13 don't light, in addition to the

usual problems of wiring errors or defec-

tive SCRs, check that Cl and C2 are installed

with the correct polarity -the positive ca-

pacitor terminals to the common buss. If

the three neon lamps operate correctly con-

nect the slot starter to the tracks and per-

form the following tests.

70

It I2 I3 S2

iii 1,1111111,11111111111,,,,111,,,,11111,,,,,,,111,1,,,,,,111111111111,11,,,111,,,,,,,,,,,,=

Set S2 to Standby for a few seconds then

flip it to Time. After I2, the Ready light,

goes on, but before 13, operate both track

controllers; if the unit is wired correctly both

penalty lights should go on and then stay on

even after I3 lights and the controllers are

released. If the Penalty lights fail to latch,

that is, if they go out after 13 lights or after

the controllers are released, check the con-

nections to K2 and K3's wiper contacts. If

the Penalty lights fail to go on under any

condition check that K1's contacts are

normally closed until I3 lights.

If both Penalty lights operate properly

reset S2 to Standby for a few seconds then

set S2 to Time. After the Go light, 13, goes

on, operate the controllers. If the unit is

wired correctly neither Penalty light should

go on. If the Penalty lights go on when the

controllers are triggered after the Go light,

13, goes on, check that Kl is operating in

step with I3 -the contacts should open when

I3 lights.

The Race Is On. Turn power switch Si

On and set S2 to Standby- thereby clear-

ing all lights. When you're ready to race

flip S2 to Time. When Go light I3 goes on

it's down on the controllers. If anyone jumps

the gun -if they start before the go signal -

their respective Penalty light will flash on;

and regardless how loud they shout the slot

starter doesn't lie -if they get a penalty light

they cheated. U

ELEMENTARY ELECTRONICS

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Go mobile with

your hi -fi. Once this

unit is on wheels you

can listen to your

favorite discs in

comfort, anywhere,

anytime, without

disturbing anyone:

The

Stereophone

Server

You'd like to relax and enjoy your favorite

stereo and mono discs, but it's getting late

and your neighbors have retired? Just roll

the Stereo Server over to your easy chair or

bed, and serve yourself some stereo at it's

best, and without disturbing anybody! This

feature makes it ideal for use in hospitals,

libraries, record shops, radio stations, and in

similar situations.

It's nice to have everything in one package

and ready to use where and when you want

it. No need to rig up your stationary hi -fi

sound system for headphone use, and use a

lot of power just to drive the phones.

As shown in the illustrations, the Server is

simply a wheeled cart with a push -handle.

The turntable and stereo pickup go on top;

the stereo headphone amplifier goes on the

shelf; and the records and headphones go in

the large partitioned space in the bottom.

The back of the record space is closed to help

keep out dust, but the back of the amplifier

space is left open to make it easier to make

the rear -panel connections.

Construction. The Server in the photo-

graph is 181/2 inches high, 15 inches wide, and

12' inches deep. The amplifier shelf is 4

JULY -AUGUST, 1966

inches below the top, and the balance of the

space below easily takes 12 inch LP's in their

record jackets. But you may want to alter

some of these measurements to fit your own

equipment.

Lumber used for the server is 5 -ply ply-

wood 1/2 -inch thick. Cut to size and sanded,

it was put together with small finishing nails

and good quality hide glue. The nail heads

were sunk below the surface and the holes

filled. The assembly was sanded overall,

dusted thoroughly, and sprayed with several

coats of thinned light -brown lacquer.

Partitions for the record cabinet are four

3/16 -inch diameter metal rods about 14

inches long, mounted as shown. Space the

rods two in front, and two in back, as shown.

The push -handle is a 33 -inch length of 3/8-

inch OD aluminum tubing bent and screw -

fastened to the side of the cart. If you make

large, round bends in the aluminum tubing

it will not flatten at the bends as it will if you

try to make sharp, square bends. The alu-

minum tubing can be polished and given a

coat of clear lacquer so it doesn't blacken

your hands when handled.

Four ballbearing swivel casters are at-

71

www.americanradiohistory.com

72

,1,,,,,1/,,,,,,0,11,,,,,,,,w0m111111uo a,umnmulmwn..ampanniimm,,.

TOP

OH HANDLE.

OB BACK

O

ACORN OR

CAP NUTS

Plan shows simplicity of the

construction. Casters should be

21/2 to 3 -inch tea -wagon type if

you have to roll Server over

carpeting, or use outdoors on a

patio. Largest wheels roll best

and are less likely to bind or

jam against small objects.

PARTS LIST

TOP -15 x 121/2 x 1/2 -inch 5 -ply veneer

BACK -15 x 14 x % -inch pressed hardboard I8 i

SHELF-121/2 x 14 x 1/2 -inch 5 -ply veneer

SIDE-171/2 x 121/2 x 1/2 -inch 5 -ply veneer (2

required)

BOTTOM -15 x 127/2 x 1/2 -inch 5 -ply veneer

DIVIDERS -14 x 3/16 -inch rod (4 required)

HARDWARE -Acorn or cap nut, 1 -inch flathead

machine screw, 6 -32 thread (4 required)

HANDLE -33 x % -inch OD aluminum tubing

(to be bent as shown)

CASTERS -2 -inch wheel surface mount (4 re-

quired)

STRIP -6 x 1 x % -inch hardboard

Misc. -Glue, finishing nails, wood screws, sand-

paper, wood filler and finish coat (stain, ^) A GLUE

varnish, enamel or lacquer). WOOD SCREWS STRIP

STEREO SERVER

You don't have to be an

expert cabinetmaker to

put this simple unit

together -it's little

more than a crate

with a shelf and a few

rods for supporting

the records. If the

cabinetry is beyond

your shop facilities

some lumber dealers

will cut stock to sire

for a small fee. You

might also find an

unpainted nighttable

or telephone stand of

suitable dimensions.

15.

i5 DRILL

i

ELEMENTARY ELECTRONICS

i

www.americanradiohistory.com

11 111111110 II 1111 1/III

STEREO RECORD PLAYER

STEREO HEADPHONE

JACKS (2)

PHONO

CHANNEL I

PHONO

CHANNEL2

,,,,

TURNTABLE

POWER CORD

(

SWITCHED

AC OUTLET

.-PM SPEAKER

3-CIRCUIT

PLUGS

Connections for the author's hi -fi

equipment consist of inserting

plugs into the appropriate jacks.

Other hi -fi equipment will have

similar connections that are

generally outlined in the manual

supplied with the instrument.

Connecting speaker to 3 -con-

tact plug is simple. An

additional speaker can be

used in place of the 10 -ohm

resistor if you want to hear

both stereo channels -use

separate cabinets for stereo.

11100111.1111111.1111111111111111111111,161,111,1111111111111 ti 011111111111111111110

v TO

117 VAC, 60,v

JENSEN MODEL

HS-2 STEREO

HEADPHONES

Completed Stereophone

Server is ready for the

hi -fi equipment. If a

vacuum -tube amplifier

is used make sure there

is enough ventilation

-leave back of shelf

open or drill holes.

10-OHM, 1-WATT

RESISTOR

iii I

11711666611410.1 121 14

2

3- CIRCUIT STEREO)

PHONE PLUG

SMALL PM SPEAKER

tached to the bottom, using four 3/s -inch

long round -head wood screws for each cas-

ter. For heavy duty, use flat -head machine

screws -heads flush; nuts on bottom.

The back of the record cabinet is covered

with a 15 by 14 by 1/2-inch sheet of pressed

wood. This can be screw -fastened, or glued

and tacked.

The connection diagram shows how the

author's hi -fi system is hooked up in the

Server cart.

Speakers. While the 20 milliwatts per

channel isn't going to break any leases you

can use it to drive speakers just as easily as

you drive the earphones. A pair of good

quality, high- efficiency speakers will give

you good listening in a quiet room.

One 3- circuit (stereo) phone plug can be

used for the stereo speakers. One lead from

each of the speakers is connected to terminal

1 of the plug. The other lead of one speaker

goes to terminal 2 and the second lead of the

second speaker goes to terminal 3 of the

stereo plug.

JuLY-Aucusx, 1966

Even if you don't want to go in for a

stereo speaker set up, a small monitor speaker

comes in handy at times. Just mount a 3 -inch

PM speaker in a small plastic, wood, or

metal box, and wire the speaker to a 3 -cir-

cuit (stereo) phone plug. Since this is a

single speaker plugged into a 2- channel

stereo output jack, it might be well to use

a load resistor in the unused channel, as

shown. The 10 -ohm, l -watt resistor can be

wired into the circuit inside the speaker box.

Use light -weight flexible 3- conductor cable

to wire the speaker and resistor to the phone

plug, as shown. If the shell of the plug is

large, the resistor can go inside.

Well, there's the idea. Now some of you

expert woodworkers, with small children in

the house, might want to add hinged doors

to the front and a hinged cover on top-to

keep out dust and the little tots' inquisitive

fingers. Or you can simply cover the turn-

table and pickup arm with thin plastic sheet-

ing when the Server is not in use. Good

listening!

'13

www.americanradiohistory.com

By Charles Green W3IKH

A shop you can set up

room, while traveling,

Nowadays most people seem to be on the

go. Traveling is part of many jobs and those

of you who relax by building some electronic

project leave this form of recreation at home.

Since everything else has become compact,

why not a compact workshop, too? Just pack

everything into an inexpensive suitcase.

How can a complete electronics workshop

fit into a suitcase with space for storing the

construction project? The trick is in the se-

lection of tools for the project construction.

Since the project can be broken down into

three stages of construction -chassis fabrica-

tion, the wiring, the testing -tools and ma-

terials can be separated into three packages.

Here, three metal boxes, sold as cash boxes,

fit neatly into a large suitcase. A cardboard

box is used to fill in the remainder of the

space. Use this space for a small folding

high- intensity lamp, the construction project

and a short electrical extension cord.

A section of hardboard is cut to fit in the

lid of the suitcase. The hardboard is a work

area and a divider for the suitcase to provide

additional storage space in the lid. Here you

can store your manuals, a few scraps of per-

forated phenolic board and some sheet alu-

minum.

Don't just rush out and buy the first things

74

anywhere -in a motel

or a small apartment.

you see. Check what you have, and leave

room for the things you plan to get. Check

what is available in the stores and make a few

measurements of the tool, file card and tackle

boxes you see. Planning will get more into

the space you have.

Cash boxes are used instead of adding compartments

to suitcase. Labe" boxes or buy different colored boxes.

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

High -speed hand grinder drills (above),

routs as well as grinds metal, plastic

and wood. Delicate bits and burrs can

be protected in plastic box. Many of

the tools (left) are unnecessary for

"breadboarding" experimental circuits.

Supply of hardware (left) is a

must. Rubberbands around boxes

will prevent accidents. A thin

sheet of sponge -like foam in the

cover will keep washers and lugs

from adjoining compartments when

you are traveling. Typewriter -

ribbon spools and boxes can be

used for wire, tape and solder.

Sponge -like foam pads box (below) to protect compact multi -

meter and grid -dip oscillator during travel. GDO is useful os a

wide -range signal generator (left) and, with adaptors, can be

used to measure inductance and capacitance. If VOM doesn't

have an off or transit position set selector to lowest current range

and put a shorting jumper across input jacks to protect meter.

JULY- AUGUST, 1966

www.americanradiohistory.com

Tv

on the

- go

76

by Harold E. Holland

Jack up the

truck? Gee,

boss, I thought

you said, "back

up the truck! !"

"Seriously, boss,

isn't it time

you considered

a truck for this

sort of thing ?"

Rnoo

Fy-EAS

\C l CO

RADIO AND TV SERVICING

Now don't get all upset, boss,

this is my own set."

ELEMENTARY ELECTRONIC$

www.americanradiohistory.com

Zener diodes do

their job at the

low voltages -

where gaseous

reference diodes

are useless.

JULY -AUGUST, 1968

The Zener diode -solid state's answer to

the voltage regulator tube -can work mira-

cles in experimenter circuits. It'll pin down

a swaying supply voltage that's causing drift

in an oscillator, or neatly string out voltages

in a power supply. These are just a few ap-

plications of the versatile Zener, whose cir-

cuit simplicity and wide range of voltage

ratings put the old tube regulator to shame.

Like any simple component that performs

a sophisticated job, the Zener must be fitted

carefully into the circuit. There are several

calculations to be sure, but you won't need

a slide rule to do them. Before considering

the steps, here's a fast refresher on what

the Zener does.

The Beneficial Breakdown. Zeners are

similar to conventional diodes; they pass

current in only one direction. When the

diode's polarity is matched to that of the

circuit, current flows pretty much as though

the diode weren't there. But reverse the diode

in the circuit and it Iooks like a high re-

sistance. Little circuit current squeezes

through.

Let's leave the diode connected in that re-

verse, or high- resistance direction -and raise

circuit voltage. At some point during voltage

increase, the diode breaks down -not in a

puff of smoke -but electrically. Current

shoots up fast as resistance drops to nearly

nil. This effect, created by a process of elec-

tron multiplication in the semiconductor

material, is called the breakdown, avalanche

77

www.americanradiohistory.com

78

@/@ ZENER DIODES WORK

or Zener voltage. And it happens to all

diodes, regardless of type, at a particular

value of reverse voltage. But the Zener is

no ordinary diode. Due to careful manufac-

turing techniques, it goes through the break-

down phase far more sharply than run -of-

the -mill diodes. It functions more nearly like

a switch. Now to put the Zener in a circuit

that not only prevents excessive reverse cur-

rent -and possible burn -out -but one that

provides voltage -regulator action.

Shown in Fig. 1 is one of the most im-

SERIES

RESISTOR

CATHODE

6 -VOLT

SOURCE 4.7 VOLTE)

ZENER

4.7 VOLTS

TO LOAD

Fig. 1. Current drawn by Zener diode drops

voltage from 6 -volt source to rated value of diode.

Improper design can ruin diode if load is

disconnected when power remains on at source.

portant Zener circuits you'll use. It's the

shunt regulator, a nifty way to tame or drop

voltage to some value required by a tran-

sistor radio, a test instrument or some other

project that misbehaves with varying voltage.

Here we're assuming that the supply is the

6 -volt source, and the device (load) to be

powered operates on steady 4 volts.

The first choice of components is simple;

it's the 4.7 -volt rating for the Zener diode.

This is chosen to agree with the voltage you

wish to apply to the device. Since Zeners

are not available in every possible voltage

rating, you'll have to pick one that most

closely approximates the desired load volt-

age. You'll find, however, that most elec-

tronic devices can function at voltages with-

in 20% of their specified value. Thus the

load in Fig. 1 may actually require 4 volts,

but can function at 4.7. It's usually voltage

variation that causes trouble. Let's examine

how the Zener operates in the shunt regulator

of Fig. 1.

A Shunt Regulator. For one, we see that

the diode is wired into the circuit in a re-

verse direction; if you look at the Zener

symbol, you'll note that the bar, representing

the cathode ( -) , is connected to the posi-

tive leg of the circuit. (Some Zener diodes

are marked with this symbol, others identify

the cathode by a rim, or hex nut.) Also ap-

parent is that the diode is wired in shunt, or

parallel, across the + and - legs of the

power source.

If the circuit of Fig. 1 is considered to

be in operation, the Zener is now in its

breakdown condition. This is because the

6 -volt power supply voltage is higher than

4.7 volts. But for the system to operate, an-

other component is brought into play. It's

the series resistor. As the Zener conducts

reverse current, it is pulling that current

through the resistor. And as Ohm's Law

dictates, current through a resistor means a

voltage drop occurs across that resistor. This

is how the 6 -volt supply is cut down to size.

What's more, if any up or down shifts occur

in the supply voltage, the Zener automat-

ically applies a correction. It happens this

way: If the supply suddenly rises to 7 volts,

additional current flows through the Zener.

This, in turn, raises the voltage drop across

the series resistor. That extra volt is dropped

by the resistor and never reaches the load.

Conversely, a dropping of supply voltage also

tends to be equalized by the Zener. The diode

pulls less current through the resistor, there-

by lowering its voltage drop. Thus the sys-

tem provides regulation. Large fluctuations,

as might occur in the electrical system of a

car, are neatly smoothed before application

to the load. Hi -fi manufacturers of solid -state

tuners use a similar Zener arrangement to

keep transistors from drifting with line volt-

age chañges.

We've seen that the series resistor plays

an important role in smoothing out voltage.

But it supplies another important function.

It limits the maximum current that may

flow through the Zener. As with resistors,

transformers and other components, a Zener

has a maximum wattage rating that is not to

be exceeded. Otherwise its silicon material

will heat excessively. This calls for some

calculation.

Figuring Circuit Values. Let's determine

the rating of the series resistor. Before its

value in ohms can be selected, you'll have

to get out the multimeter and run some

measurements on both the power source and

the load, or device, you wish to power. Let's

say you have a small transistor transmitter

or handie -talkie that works on a 9 -volt bat-

tery. You want to operate it in your 12 -volt

automobile using the car's battery. This is a

fine application for the Zener. For not only

will it help reduce car's battery voltage to

the right value, but will iron it out.

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

Larger -wattage Zener diode can be mounted on

chassis or proper heat sink. This oversized view

shows Zener fo be identical fo conventional

diodes. Low -wattage units have pigtail leads.

First measure the power source. Since it's

the car's electrical system, run a voltage

check on any 12 -volt lead. You'll find that

if you race the engine, voltage can soar up

to 15 volts. This figure, the highest possible

supply voltage, we'll call VIN -for input

voltage. It is the unregulated source.

Next value is V.-the Zener voltage. As

mentioned earlier, the diode's voltage rating

is selected to match that of the load. Since

we need 9 volts, in this case, we could select

the closest standard Zener value of 9.1 (ac-

tual examples would be a Motorola 1M9.Z

or IR 1N3019). The power rating of the

Zener, in watts, is shown in a moment.

Now to find out the amount of current

consumed by the load- another job for the

multimeter. In the transistor radio, this is

simply done by operating the set on its reg-

ular battery and disconnecting one battery

clip. Insert the meter probes (with meter

set to read ma.) at the break. The radio will

play and you'll see current consumption. Try

all operating conditions -like changing the

volume control setting -and observe the least

amount of current drawn by the radio. We'll

assume that it is 20 ma. That number, writ-

ten as amperes (.02 A) is IL, or load current.

What this whole procedure is leading to

is a set of operating conditions for the regu-

lator that produces the greatest stress for

the Zener. Once they are known, it's an easy

matter to design into the circuit an ample

JULY-AUGUST, 1966

safety margin and avoid burnout.

The final figure we'll need is IZ-or Zener

current. It is recommended that a Zener be

operated at no more than about 20% of its

maximum rated current. If we consult the

spec sheets and select a 9.1 -volt Zener diode

rated at 1 watt, the maximum current rating

might be stated as 90 ma. This figure is

divided by five to determine Zener current

in the practical circuit. This gives an Iz of

18 ma.

Figuring the Formula. Once you've deter-

mined each of these circuit values it's pos-

sible to plug the numbers into a formula and

come up with the required series resistance.

Let's continue with our example, whose

values are shown in Fig. 2.

The formula: R. = VIN - VZ

IZ + IL

Inserting the values:

Rs 15 -9.1 =5.9 =150

.018 + .02 .038

The answer, 150, is the series resistance Rs

in ohms. By coincidence, this is a standard

resistance value. In other cases, use the near-

est value.

Rs 150n

Fig. 2. Calculations for Zener -regulated 9 -volt

battery substitute operated from 12 -to -1S volt DC

automotive electrical system. Current drawn

by Zener will vary with input voltage and load.

From the same formula, resistor wattage

is also calculated. Just multiply top and bot-

tom figures of the formula, which are re-

sistor voltage and current: 5.9 X .038 = .22

watt. Double the wattage to .44 for safety

and use a .5 -a standard half -watt resistor

of 150 ohms.

Circuit Features. This, then, is the basic

shunt regulator. It will automatically keep

voltage to the radio at a constant, correct

value regardless of car speed. By using this

approach you can design the Zener into

other applications for the control and regu-

lation of other DC- supply voltages. There

are, however, certain features of the shunt

design which should be considered.

In general, the shunt circuit is used where

a fairly large voltage drop is needed between

source and load. Also, the shunt arrange-

ment regulates not only during shifting sup-

ply voltages, but changing load current, such

as occurs in the transistor radio.

T9

www.americanradiohistory.com

80

ZENER DIODES WORK

In Series. Another Zener circuit is the

series type, shown in Fig. 3. This system,

however, is limited. Since the Zener must

handle both resistor and load currents, the

diode's wattage rating can run to high, im-

practical values. Also, the series circuit regu-

lates only the effects of changing load cur-

rent, and can't smooth out power supply

fluctuations. It may be found useful, how-

ever, where voltage difference between sup-

ply and load are small (as illustrated in Fig.

3) and the supply voltage is constant.

;,,,,,1111111111111,111,11111111,,,,11111,,1111,, ,,,,,,,,1,,,,,,,,,11,,,,,,,1, ,,,,1,,,,11, 111111,1111111111,,,111111111111,.1,

PARTS LIST

C1- 30 -mf., 150 -volt electrolytic capacitor

C1- 50 -mf., 150 -volt electrolytic capacitor i

D1- 100 -ma., 300 -pry (pivl silicon diode

L1-9-henry, 50 -ma filter choke

R1-47 -ohms, 1/2 -watt resistor

Rs-see text

51- S.p.s.t. on -off switch

T1 -117 -volt primary, 125 -volt, 50 -ma second-

t ary power transformer

Z1 -27 -volt Zener diode, 1N1781 or equiv.

Z2 -22 -volt Zener diode, 1N1779 or equiv.

Z3 -18 -volt Zener diode, 1N1777 or equiv. i

Z4 -12 -volt Zener diode, 1N1773 or equiv.

Z5 -9.1 -volt Zener diode, 1N1770 or equiv.

Z6 -6.8 -volt Zener diode, 1N1767 or equiv.

28V 4V ZENER

INPUT

24V

OUTPUT

Fig. 3. Series -connected Zener diode will

provide a constant voltage drop. If voltage goes

fo 29 volts, voltage across output will rise

to 25. Circuit has many limitations- seldom used.

Fig. 4. Diodes can be wired

in any order that gives

the greatest number of usable

voltages for your use.

Additional diodes can be added

as long as DC across

circuit is increased in like amount.

SPST

ON -OFF SWITCH

-4 T1

POWER

TRANSFORMER

117VAC

DI

Handy Power Supply. Here is a versatile

source of power for the experimenter. Based

on Zener diodes it provides a number of use-

ful functions around the workbench. Not

only will it act as a voltage reference for

checking calibration of a meter, but can

supply a large number of regulated -DC volt-

ages for powering small transistor projects.

We'll give a basic circuit here, but you can

easily vary it to suit a particular need.

The complete supply appears in Fig. 4.

The section on the left is a conventional

half -wave transformer supply operated from

AC line voltage. Suitable values are shown

next to each component. Ratings for the

silicon diode are minimum and you can use

a larger (and more common) unit. The ca-

pacitors may be one dual -section electrolytic,

the kind usually sold for replacement.

The output of the supply utilizes a group

of six Zener diodes connected in series across

the DC output of the supply. Although out-

put voltage from supply is over 100 volts

DC, each diode will display its own Zener

voltage across its terminals. Not only can you

obtain six different output voltages, but

various combinations.

By connecting across the terminals of any

single diode you'll obtain its specified Zener

voltage. Hook across two or more Zeners

and you'll get the additive voltage among

them. For example, hook to the top of Z2

and the bottom of Z3 and you'll obtain 40

volts. Thus there is a remarkable number of

voltage possibilities -plus the full output of

the supply. Note that in hooking across any

Zener or combination, the positive side of

the circuit is the upper connection; the nega-

tive is the lower terminal.

We've shown a typical assortment of Zen -

(Continued on page 110)

TO

27V

L1 Rs $0

R1 (SEE TEXT) 22V

47f1 to

18V,

Zio

Z20

Z30

240

250 0

+ Cl + C2

30MF 50MF

Z6

12V

#o

9.1V

$0

s.8V

lo

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

Expensive chemicals and elaborate equipment

are not always needed for many electroplating jobs

Most of the articles dealing with electro-

plating will tell you to go to the drugstore,

or some chemical supply house, to purchase

chemicals to use in the electro -bath; not so

with this type. You need only tap water,

sugar, and a pinch of salt, and the results are

comparatively good, especially for small

articles found around the house or work-

shop. This type of plating will probably in-

trigue the do- it- yourselfer, if for no other

reason than its sheer simplicity.

Almost any type of plating, within reason,

can be done this way: copper on iron or

brass; silver on brass or copper; gold on cop-

per or brass; and yes, even stainless steel on

brass or copper. The nicest part of it is that

you can steal the metal to be deposited from

discarded objects around the home or work-

shop. For example, if the distaff side of the

family should become tired of the color of

her earrings, why not plate them with a coat-

ing of stainless steel which is not unlike that

of silver? Or, if you should have some gold

plated objects no longer useful, why not give

the earrings a plating of gold?

To start, select a small drinking glass or

any similar vessel and heat it to a point

where it becomes uncomfortable to hold.

Fill the glass half full with warm water.

Pour in a teaspoonful of sugar and stir. In-

sert into the liquid the metal you wish to

plate. For example, say you want to do

copper plating. Then, the positive electrode

will be some form of discarded copper, and

the negative electrode will be the object you

wish to plate.

Connect these to one of the circuits given.

Be sure to observe the proper diode polarity.

After all connections have been made, drop

a pinch of table salt into the warm water.

Wait for about ten seconds and observe the

light bulb. If after ten seconds there is no

glow, drop another pinch of salt into the so-

lution. Continue until you observe even the

faintest glow. Cover the solution with a

cardboard to prevent the bursting bubbles

from splashing. Let the plating continue for

a while, checking it periodically. Always dis-

connect the power when you do your check-

ing. In less than an hour you should ob-

serve a deposit building up along with a

discoloration of the electrolyte -in this case,

a light blue.

Using the same circuit and a new solu-

tion, you can plate with almost any discard-

ed metal. The object to be plated will always

be the negative connection. The author used

gold from an old watch case to plate a set

of earrings, stainless steel from an old knife

to plate some Fahnestock clips, and silver

from a discarded spoon to plate some elec-

trical- contact points.

The obvious advantage of this type of

plating is that special chemicals are not re-

lil iIIrII:IIIiIIIIIIIII,111111 I I 11 1 1

'444.444444444444444,444t44444t144444- 1

1 41111111111111IIIIi11111illlllltlllt I

....4..+,t.

1 ; 1111111111111111111#1111#111111111111 E1

Pti t4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 t4 4 14 1114 4 4

111 111111 1 1111 11 1 1 1111111111 1 111 i 1 1 1 i 11

,++.....1..t.. .;

I 11111111111t111111t111111111111111tt1

t it ' 44444ttttttt1 1'ti itt

lilt It RI it rl t 1 1! 1 1 I ! !E1{ 11,18

***4 44.. for the Hobbyist

by Martin H. Patrick

JULY- AUGUST, 1966 81

www.americanradiohistory.com

( ( ELECTROPLATING

quired and that the same basic procedure is

followed with all metals.

The quality of the electroplating depends

directly on the preparation of the object to

be plated. The object must be thoroughly

cleaned of grease and oil, and if a shining

result is desired, it is necessary that the ob-

ject be buffed and polished before plating.

If objects made of iron fail to take a plating,

try copper plating it first. Then follow by

plating with first selected plating metal.

PARTS LIST

B1, 82 -1.5 -volt dry cell (Number 6)

D1- 750 -ma, 300 PRV (PIV) or higher rating

silicon diode (1N539, 1N1489, 1N1763 or

equiv.)

D2- 750 -ma, 50 PRV (PIV) or higher rating

silicon diode (1N536 or equiv.)

I1 -15 to 50 -watt, 110 to 125 -volt light bulb

12- 250 -ma, 6 to 8 -volt pilot lamp (type 44,

46 or equiv.)

M1 -0 to 1 -amp DC panel meter

R1 -15 -ohm, 25 -watt rheostat

T1 -117 -VAC to 117 -VAC isolation transformer

(Lafayette 33R7502 or equiv.)

T2- 6.3 -V, 1 -amp centertapped filament trans-

former, any inexpensive unit will do

Misc.- Socket, clips, wire, scraps of precious

and semiprecious metals, water, salt, etc.

12mm

T2 1

1N539 PLATING

METAL

(ANODE)

ISOLATION

TRANSFORMER

SMALL DRINKING GLASS

OBJECT TO BE PLATED

(CATHODE)

Even using a 1:1 isolation trans-

former does not make the circuit

above safe -117 volts is quite a

jolt even when current is limited

by 11. Without T1 it is really a

death trap -don't eliminate TI.

Setup with T2 is quite safe. The

lamp (12) limits current to pro-

tect the transformer, and whether

the full 6.3 volts or the center -

tap value of 3.15 volts is used,

touching the bared wires produces

little more than a strong tingle.

3.15V

CT --1

3.15V I

FILAMENT

TRANSFORMER

RI

PLASTIC ROD OR WOOD DOWEL

STRONG THREAD

ANODE

SATURATED

COTTON WICKING

OR

FROM

+ -

FROM BRUSH \\

82

BATTERY CLIP SURFACE

TO BE PLATED (CATHODE)

CATHODE

DRINKING

GLASS ANODE

ITEM TO BE PLATED

Dry cells are safe, too. For ex- 3

tensive electroplating use large I

cells (or filament transformer

circuit at top). For one small job

you can even use the penlight

types of cells. Electroplating re-1

quires current -the larger the

surface the greater the current

needed. Too little current in-

creases the time required while

too much current causes excessive

bubbling at immersed electrodes.

11111117111M MHZ

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

Those

Fabulous

duel Cells

by Len Buckwalter

Reverse electrolysis

generates the power

instantaneously -

as long as fuel

and oxidizer are

supplied to cells.

No moving parts to

wear out -silent

operation that

provides pure water

as a waste by-

product. And it's

80% efficient.

Any high school science student can

probably tick off a half -dozen ways for pro-

ducing electricity. There's the spinning coil

inside a magnetic field (generator), chemicals

reacting in a container (battery), heating

metals (thermoelectricity), friction (static

electricity), squeezing a crystal (piezoelec-

tric) or light waves on semiconductors

(photoelectric) .

Now There's A New Way. It's the fuel

cell; a compact package that surrenders more

electricity per pound than any other source -

except nuclear energy. So promising is this

neat electrical device that researchers have

already racked up some remarkable suc-

cesses. Chrysler Motors can point to a

model automobile that's buzzed around a

test track with an engine that neither growls

nor spits exhaust. Power is by fuel cell and

electric motor.

Allis- Chalmers won a place in history

JULY- AUGUST, 1966 83

www.americanradiohistory.com

84

FABULOUS FUEL CELLS

Cutaway view of General Electric fuel cell shows

ribbed current carrier, hydrogen inlet and purge tubes.

Cell is about 7 x 8 inches -96 cells are in a battery.

when its full -size tractor, power by fuel cells,

wound up in the Smithsonian Institution.

Even now, the military services use them to

power small field -type radar sets. Gone is the

gas- engine generator whose noise might warn

a nearby enemy.

But the most dramatic use of the new pow-

er source is in space. Those weeks -long

Gemini flights just couldn't have been made

without the light weight and efficiency made

possible by fuel cells.

Reversed. If you've ever seen the classic

experiment in chemistry -the electrolysis of

water -you witnessed the operation of a fuel

cell, but exactly in reverse. This is the

demonstration that proves water is actually

made of the gasses hydrogen and oxygen. To

conduct the experiment, a current of elec-

tricity is passed through water. As water

molecules (H20) absorb energy, they split

apart into component parts. The wet stuff

disappears and two gasses are created.

Reverse That Process. Begin with the

gasses hydrogen and oxygen, cause them to

combine, and they'll not only form water,

but release electrical energy as well. That's

the heart of the fuel cell and, in fact, many

practical fuel cells do just that. There are,

to be sure, some exotic chemical techniques

to aid the process. Catalysts (platinum for

example) must coax the gases into com-

bining. And special membranes keep the

reacting agents free of contamination.

The excellence of the fuel cell lies in its

ability to convert energy- chemical to elec-

trical-in a surprisingly direct manner. Far

cry from the traditional method of power

generation; say, burning coal to produce

steam, to spin a turbine, to turn a generator,

and so on. Although we get much electrical

power this way, efficiency is a meager 40 %.

Fuel cells, on the other hand, reach up in the

80% efficiency region. But before you call

your utility company and have the house cur-

rent turned off, look at costs. Fuel cells pro-

duce a huge number of watts -per -pound, but

cost is still prohibitive for residential or com-

mercial use. If your monthly electric bill is

now $10, it would skyrocket to about $100

if fuel cells ran lights, TV and other house-

hold appliances. But in military and space

applications, performance, not cost, is the

boss. In one case, a 55 -pound fuel cell

eliminated 1000 pounds of ordinary storage

batteries (like the one in your car). This is a

bonanza for rocket -powered vehicles where

weight is reckoned by the ounce.

It might seem the fuel cell bears some re-

semblance to any ordinary battery. It does up

ANODE

GAS CHAMBERS

SOLID POLYMER

ELECTROLYTE

CATHODE

FUEL

(HYDROGEN)

CATALYTIC

ELECTRODES

OXIDIZER

(OXYGEN)

H2O

Fig. 1. Simplifed diagram of fuel cell indicates fuel

and oxidizer inlets, gas chambers, electrolyte and the

catalytic electrodes. Inset circles diagram action

that produces electricity, a pure -water by- product.

to a point. Both fuel cell and battery are

fundamentally devices which depend on

chemical reactions to obtain electrical power.

But here the similarity ends. A conventional

battery is considered a storage medium of

energy. It is limited by the extent of its

primary charge or by frequent recharging.

But fuel cells continue to operate so long

as fuel and oxidizer (hydrogen and oxygen,

for example) are fed in from an external

source. Another big difference is that ma-

terials which make up the fuel cell do not

change as they process fuel into electricity.

What's more, a by- product of fuel -cell opera-

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

Photos courtesy of General Electric

Clean -room assembly

of fuel -cell batteries

rivals cleanliness

of hospital operating

room at General

Electric's Direct

Energy Conversion

Operation at Lynn, Mass.

Cutaway mockup of

Gemini fuel -cell bat-

tery is displayed

by Roy Mushrush, Man-

ager of General

Electric's Direct

Energy Conversion

Operation. One fuel -

cell stack is held

in his right hand.

Toughness of solid polymer electrolyte is demon -

strafed by Dr. Russell Hodgdon of General Electric's

Fuel Cell Laboratory. New electrolyte, developed by

GE, has increased cell life expectancy four times.

tion is water, suitable for drinking or cooling.

Here's How. Fuel cell operation is illus-

trated in Fig. 1. The cell consists of a num-

ber of basic elements: anode and cathode, an

electrolyte to act as a transportation medium

between electrodes and the fuel oxidizer.

Note that the two gasses are seen entering

the center portion of the cell. Near the lower

left of the drawing is a blow -up of what

happens when hydrogen gas (2H2) reaches

the anode. The reaction causes the gas mole -

clue to surrender electrons. These negative

charges ( -) travel upward and constitute

the electric current flow to the load (which

might be a lamp, radio, etc.) As hydrogen

supplies electrons to the load, it becomes

ionized (4H+) and travels into the electro-

lyte solution between the electrodes. Hydro-

gen ions reach the cathode where they com-

bine with electrons returning from the load,

and ogygen entering the fuel cell. The inset at

JULY- AUGUST, 1966

lower right illustrates the chemicals com-

bining, which produces water. Note that

H50 (water) drains from the bottom right.

A valuable feature of the cell, in addition

to high efficiency or watts -per -pound, is that

it's "self- throttling." It consumes fuel only

as required. Power can be switched off in-

stantly by opening the load circuit. This

stops the chemical reaction.

As in conventional battery systems, the

fuel -cell type consists of a cell which is

usually combined in series or parallel to ob-

tain voltage or current (or both). An opera-

tional cell made by GE, for example, typical-

ly produces rather low voltage, somewhat

less than one volt. Wattage depends on the

surface area of the cell and may be up to 75

watts per square foot. Several of these cells

are connected in series to form a module

or battery of approximately 30 volts output.

Three such modules can then be placed in

85

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86

FABULOUS FUEL CELLS

parallel for high- current output. The final

package is then termed a fuel -cell battery.

Performance ratings of a one -thousand watt

unit, used in spacecraft, is shown in Fig. 2.

It may be seen that as the current drain

(amps) rises, the output voltage of the bat-

tery drops slightly, but remains in the 30 -volt

region.

More complete specifications for this fuel -

cell battery, and a smaller version, rated at

35-

30-

25-

w 20-

1_115-

o

10-

5

o 10 Ì5 2b 25 30 35 40 4&

CURRENT (AMPS)

Fig. 2. Voltage -current curve of typical fuel -ce11

battery. A few calculations will show that

battery's internal resistance is less than 0.2 ohm.

350 watts, are given in the table. You can

see, for example, that to produce one thou-

sand watts for one hour, the 1 -KW unit re-

quires about .1 pounds of hydrogen; and .8

pounds of oxygen.

The Future. Today's techniques of fuel -

cell operation are by no means final. There

are plenty of other experimental approaches.

One is the hydrocarbon concept. Instead of

gases, tanks are filled with common hydro-

carbons, like gasoline, or kerosene. Then,

acting like a miniature chemical plant, the

hydrocarbon fuel is split into gases which

enter the cell and generate electricity. Only

problem here is that plenty of heat is needed

to convert the hydrocarbon fuel into gas

form. Yet there is hope; primitive models

using this principle needed some 1000 de-

grees F, but recent versions can do it at 150

degrees F. If the scientists ever do it at room

temperature, it could rock our concept of

how to propel the family car.

Experts in the field wort name the day

they'll start production, but they've already

stroked in outline designs of a fuel -cell pow-

ered car. For one, the efficiency of such a

vehicle would be about three times higher

than that of the present automobile power

plant. They envision small electric motors

mounted in each of the car's wheels, with

electrical power generated by fuel cells. This

does away with bulky transmission, radiator

and big engine compartment. Air pollution

problems simply don't exist -the exhaust is

water! Even the car's braking system is

radically changed -to a type now used on

both trains and tape recorders. It's called

electrodynamic; the spinning car wheels ro-

(Continued on page 111)

TYPICAL FUEL CELL CHARACTERISTICS

1 KW FUEL CELL BATTERY

Contains 3 modules of 32 fuel cells, pressure

regulators and sensors, product water separator.

Fuel: Hydrogen, approx. 0.1 lbs /kwhr

Oxidant: Oxygen, approx, 0.8 lbs /kwhr

Output: 1 kw peak

By- product: Water, approx. 1 pint /kwhr

Weight: 70 lbs. approx.

Size: 12.5" dia., 25" long

Cooling need: Liquid coolant. Temperature at

inlet: 400-100 °, 75° avg. Higher

temperatures tolerated for brief

periods.

Efficiency: 50 % -60%

350 W FUEL CELL BATTERY

Contains one 32 -cell module with pressure regu-

lators and sensors, product water separator.

Fuel: Hydrogen, approx. 0.1 lbs. /kwhr.

Oxidant: Oxygen, approx. 0.3 lbs. /kwhr.

Output: 350w peak.

By- product: Water, approx. 1 pint /kwhr.

Weight: 35 lbs. approx.

Size: 14" die., 16.5" long.

Cooling need: Liquid coolant. Temperature at

inlet 40° -100 °, 75° avg. Higher

temperatures tolerated for brief

periods.

Efficiency: 50 % -60%

ELEMENTARY ELECTRONICS

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You don't need any

special powers to

operate this switch.

Touch it with your

finger, elbow or

even with the back

of your hand.

SCR

Touch -Control Switch

by Lester Escargot

Most science- fiction super heroes have the

power of the universe at their fingertips; they

simply point and buildings collapse, the sun

darkens, and the vilest of enemies are ban-

ished to the sixth dimension. You've got pow-

er in your fingertips, too; not enough to de-

stroy buildings, or get scantily -clad girls to

throw themselves at your feet, but enough

to forever eliminate turning knobs, throwing

switches, and even fumbling in the dark for

the light switch.

Yes, the power is there -it's the residual

AC voltage picked up by your body from

the power lines in the immediate vicinity;

just concentrate the power to your index

finger, say the magic word "Zotz," and voila,

you can turn anything on or off by just point-

ing your finger. Got a ham rig? Just touch

the mike stand and the transmit relays snap

to attention. Fumble for the keyhole after

a few slurps of the sauce? Just put some tin-

foil alongside the door and your index finger

will turn on the porch lights until you enter.

Use CB? Just point your finger when you're

ready to talk and you're on- the -air. In fact,

you can control anything that goes on and oft

.JULY -AUGUST, 1966

by just pointing your finger.

Of course, some of us haven't yet mastered

the art of concentrating power to the finger,

so you'll have to use a finger -power concen-

trating amplifier, otherwise known as a Touch

To- Operate SCR Load Control, (which we

will naturally refer to henceforth as the SCR

Control.)

What Is It? The basic SCR Control -

courtesy of General Electric -is shown in

Fig. 1. C2 is a fixed capacitor of approxi-

mately 25 mmf. and Cl supposedly repre-

sents the capacitance of the body to ground.

When a finger is touched to point X the body

completes the capacitive voltage divider

across the AC power line, C2 starts to charge,

and when C2's charge reaches the ionization

voltage of neon lamp NL1, the lamp con-

ducts, C2 discharges into the SCR gate, the

SCR is triggered (conducts) and power is

applied to the load. The SCR will conduct as

long as the finger (or hand, or any part of

the body) contacts point X.

If the load is a 117 -VAC relay the relay

will operate in step with bodily contact to

point X. If the load is a lamp it will go on

87

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@Ag SCR TOUCH- CONTROL

POLARIZED

ANODE GROUNDED TO CASE

Fig. 1. Cl is capacitance between human body and

earth ground. If direct contact fo point "X" is

possible T1 (below) must be used in circuit.

Fig. 3. Components used here are identical to those

used in the other circuits except for TI.

TO LOAD

117

VAC

TO

POWER - ON

INDICATOR

and off with point X. If an impulse relay is

used as the load a touch to point X will

turn the relay on, and it will stay on until

a second pulse is applied through contact to

point X.

Where to Use It. Fig. 2 suggests possible

applications of the touch control. Fig. 2A

is an SCR substitute for the old capaci-

tance- operated relay (which used an RF

oscillator and cost at least 5 times the price

of SCR control). The load in this instance is

a porch light, and point X, as shown in the

photographs, is connected to a large strip of

aluminum foil tacked to the doorframe op-

posite the doorlock. As you reach for the

keyhole at night your hand will brush the

foil, tripping the SCR and turning on the

porch light until you enter.

Fig. 2B is a touch -to -talk circuit. It could

be used by Hams and CB'ers. Relay K1 con-

trols the transmitter or transceiver's push -to-

talk (PTT) circuits -either relay or elec-

tronic switching. A little metal foil can be

cemented to the mike base or a length of

bare wire can be stapled to the edge of the

88

POLARIZED

117

VAC -

TINFOIL

"X PLATE

AMP

T2

II

SCR

R2

Fig. 2. With aluminum or tinfoil plate attached fo

the inside of a showcase this circuit is quite safe,

for use without transformer 71. Linecord plug

polarity is still important for the operation of

the circuit. Showcase glass acts as dielectric

of capacitor -foil is one electrode and body

capacitance (C1 in Fig. 1) completes circuit fo

ground. Circuit 28 (below) is mors -or -less

identical to 2A (above) except That the lamp is

replaced by the relay coil in the circuit.

POLARIZED

PLUG K1

TO

CIRCUIT

CONTROL

a

operating desk and connected to point X.

Whenever the foil or wire is touched the rig

switches to transmit; when the hand is re-

moved the rig switches back to receiving.

For latching control, simply use the cir-

cuit shown in Fig. 2B but substitute an im-

pulse relay for K1. An impulse relay "trips"

and stays tripped until a second pulse is ap-

plied. To trip the impulse control you'd

simply touch the wire or foil connected to

point X and then remove your hand. The

single pulse will cause the impulse to close.

To open the relay you'd touch point X again.

While the SCR results in DC flowing

through the load, you can use an AC relay

of the same voltage rating. If the input volt-

age is 117 VAC the relay can be rated 117

VAC or 117 VDC. If there is severe chatter

when using an AC relay connect a 400 PIV,

500 ma. silicon rectifier across the load with

the anode connected to the SCR side of the

load. Carefull As you probably have noticed

the G.E. circuit can be a death trap as you

must be absolutely certain the ground side

ELEMENTARY ELECTRONICS

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ninnianitisnntnnitin an 11 Inmum,,,n,,u,,,,,,,,,,ni,,unnn n 11 1111111111

T1

SCR1

Transformer TI is the largest item in

the SCR Touch -Control Switch. The

completed unit (left) shows the layout =

of components, which is not critical. 1

While perforated- phenolic board is

used here the layout could be on plain

stock and holes drilled to suit the

components. Flea clips are inserted

in the perforations -only holes that

need be drilled are for the transformer.

When connecting the SCR be sure to 3

locate the proper leads in relation

to the dot on the molded case.

Il

R2

C2 R1

PARTS LIST FOR SCR TOUCH-CONTROL SWITCH

C1-25-mmf., 500-VDC disc capacitor C601 B (G.E.)

I1-Neon Lamp, NE-83 or NE-211 (see text) Tl-Transformer (see text)

R1-100,000-ohm, 1/2-watt resistor Misc.-Perforated board, flea clips, etc.

£ R2-5600-ohm, 1/2-watt resistor Estimated construction cost: $5.00

SCR1-Silicon controlled rectifier, C6B or Estimated construction time: 1 hour

; ninnonnnamannn nounninnunnninnonninnion tan

of the AC line is connected to the grounded

side of the SCR control. If you put a non-

polarized plug on the SCR control you may

go before the fuse. For maximum safety,

use an isolation transformer as shown in Fig.

3. And it is not necessary to ground the line

at the load. The voltage picked up by the

body is sufficient to trip the SCR without

the ground connection. A typical SCR con-

trol is shown assembled on a section of per-

forated board in the photo above.

The SCR control shown is a light -duty

model. Transformer T1 is a standard power

transformer with 6.3 volt at .6 amp and 125

volt at 15 ma. secondaries. While 15 ma.

will certainly not light a lamp it is sufficient

to trip a sensitive AC relay -the 6.3 -volt out-

put is used to power a pilot lamp. Naturally,

T1 must be able to handle the load, and since

isolation transformers of any substantial rat-

ing can be expensive, you could use a pair

of heavy- current surplus filament transform-

ers back to back. (In a sense the SCR con-

trol is experimental, so do as you please.)

If you want to control a heavy load such

as a 500 -watt bulb it's best to have a light

duty SCR control with a sensitive relay for

the load -then have the relay turn the lamp

on and ofj.

A sensitive SCR is needed, otherwise the

JULY -AUGUST, 1966

"power in your body" is not going to trip

the gate. The SCR to use is the General Elec-

tric type C6B or C601B. Both models han-

dle up to 0.6 amperes without a heat sink,

the difference being the C6B has leads while

the C601B has tabs (for perf -board and

printed circuit mounting). Do not substitute

the G.E. experimenter SCR, the X5 -its

voltage rating is only 50 volts.

Neon Lamp I1 should be the NE -83, a

special neon made for use in the dark (no

light). If you cannot obtain the NE -83 the

more or less standard NE -2H can be substi-

tuted though there may be a slight loss in

sensitivity if the SCR control is placed in a

cabinet (dark).

If you experiment with the circuit, and

you should as that's what it's for, you'll dis-

cover you can get astounding sensitivity if

your finger is placed at the junction of R1

and C2 instead of at point X. Don't do it as

a matter of course. R1 is a protection device

that isolates you from the AC line should

C2 or I1 fail; it also keeps you isolated

from the SCR gate.

We've shown just a few uses for SCR

Touch Control; we'd like to see what ideas

you readers out there in magazine land can

develop. If it works well and is safe, how

about scratching it out and passing it along?

89

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TV Schooling

for Hospitalized

Students

Television can be

more than cowboys,

comedy and

commercials.

As the shut -in's

window -on- the -world

it can prevent

boredom or help

continue education.

90

Young school -age patients at the Massa-

chusetts Hospital school, Canton, Mass.,

don't fall behind in their school work. They

attend classes without leaving their beds -

thanks to a closed- circuit television (CCTV)

system.

The hospital school is world famous for

the treatment and education of handicapped

children. It now accommodates about 150

children but capacity will be 230 -after the

completion of the building addition.

If they're able, young patients attend class-

room sessions. However, many are confined

to the hospital beds for lengths of time vary-

ing from a few days to months. Prior to in-

stallation of CCTV, bed students averaged

20 minutes of individual tutoring each day.

These youngsters still receive tutoring, but

they also share the educational climate of

the classroom with their fellow hospitalized

students.

A standard curriculum, in grades 1 to 12,

is offered at the school. Any student, whether

he's in bed or in the hospital classroom, may

take advantage of any course taught. CCTV

cameras scan classroom sessions and relay

them to bedside TV receivers. A two -way

communications system between teacher and

the bed -student and the bed -student and the

classroom lets anyone ask or answer ques-

tions, at any point in the lesson, just as

though the patient was present in the class-

room. Recorded Material. Much of the material

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

has been previously recorded on Ampex

Videotape television recorders for showing

at class time. As the teacher wishes, she may

show students a lecture (recorded months

ago and many miles away) by an expert on

a particular subject, an experiment per-

formed in the laboratory class hours be-

fore, or any other presentation.

According to Dr. Margaret Brayton, the

Director of Education at Massachusetts

Hospital School, "The Videotape recorders

are expected to play an important part in

the school's new educational system. For

instance, cost might prohibit bringing an out-

standing lecturer here from the West Coast.

By recording the lecture on video tape and

having that shipped to the school, our stu-

dents will have the benefit of an educational

experience otherwise unavailable."

Ampex Corporation's Videotape recorders

are key elements in many CCTV systems-

JULY-AUGUST, 1966

Classroom (above) does not have hospital

atmosphere. Teacher Eleanor Woods prepares

to playback previously recorded material for

bedridden and classroom students alike.

Science teacher, Donald Gay (top left) points

out parts of the human anatomy to classroom

students -those in bed view scene with help

of CCTV camera on wall, at top center, which

scans classroom activity.

Key elements in this 16- channel system are two

90 -pound Ampex Videotape recorders.

Equipment used to transmit motion -picture film

and slides, as well as monitoring equipment

are packed into control room shown at left.

Recording tape is on wide reels.

preserving moving pictures on magnetic tape

much as sound is recorded. A 90 -pound

portable recorder, used at the Massachusetts

Hospital School is a direct descendent of

larger models used to record network TV.

Dr. Brayton added. "You don't mind

spending time and energy on a project if

you know it won't be lost as soon as it's pre-

sented. With our television tape recorders

we can play back a recorded presentation as

many times as we desire. The original value

of the presentation is expanded many times."

Massachusetts Hospital School's $170,000

CCTV system was engineered and installed

by Lake Systems Corporation, Watertown,

Mass. The system permits 16 channels to be

telecast to individual bedside receivers

throughout the hospital area. Also, as soon

as the day's schooling is completed, com-

mercial off -the -air TV programs are avail-

able on the same receivers.

91

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Calibrated

Attenuator

by

James A. Fired

When we turn the knob on the volume

control of a radio, TV set or hi -fi amplifier

little do we realize the care that has gone into

the selection and design of this component.

When choosing the value and taper of the

control the design engineer must decide what

volume of sound he wants for each degree of

control rotation. The process of making the

sound softer is called attenuation.

A modern American dictionary defines

attenuation as, "1. to make or become thin,

2. to weaken." So in technical language we

attenuate a signal when we make it weaker.

We hope to fill a twofold purpose: 1, to

show the relationship between the resistance

taper of a variable resistor and its attenuation

curve, and 2, to show how to design a con-

trol for any desired amount of attenuation

and to build a 60 -db attenuator using the

principles discussed.

Before we go into the actual design of an

attenuator let us first find out something

about variable resistors. If you consult cata-

92

A fortune is not

needed to have a

calibrated control

instead of a plain

volume control on

your amplifiers,

recorders and hi-

fi equipment units.

Circuit changes

are slight - only

a small resistance

has to be added to

the layout to make

calibration easy.

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

J1 J2 R1 J4 J3

/ I 1 1

1 "sue

Front panel (above) shows all components except R2

which is mounted on R1's terminals inside case.

logues of such variable- resistor manufactur-

ers as Centralab, Clarostat, and Mallory you

will find two terms used to describe variable -

resistor characteristics. One term is overall

resistance and the other is taper. Overall re-

sistance means just what it says, while the

taper indicates how the resistance varies with

rotation. For example, some variable resistors

may have only half the resistance in the

circuit when turned 80% of the way on

(clockwise), and compress the other half of

the resistance into the last 20% of rotation.

If the resistance varies directly with rotation

(25% of the rotation equals 25% resistance,

50% rotation equals 50% resistance, etc.)

the manufacturer calls it a linear taper or

simply linear.

Volume control characteristic curves are

usually drawn showing percent of resistance

versus percent of rotation. This allows for

quickly comparing one control against an-

other without regard for resistance. The taper

is usually specified as being a certain per-

centage of resistance at 50% of rotation,

so 5 percent of resistance at 50% of rotation

is usually referred to as a 5% taper. Of

course each manufacturer has his own

identifying symbols for his own tapers. A

cross reference of tapers and designations for

three companies are listed in the table titled

"Resistance Tapers."

Two variations of the term that you will

find in catalogs are left -hand and right -hand

tapers. If you hold a variable resistor with the

end of the shaft facing you and the terminals

down, the left -hand terminal will be the coun-

ter- clockwise (CCW) terminal and the right -

hand terminal will be the clockwise (CW) ter-

JULY -AUGUST, 1966

.:1111111111111111/2111

,, : , 111111111/M11111111111

111111211111111111111111

,

11/1111111111111111=ó,o

MIR11111111111111111111

10 20 30 40 50 60 70 80 90 100

PERCENT OF ROTATION

Characteristic curve (above) will vary from one

control to another depending on quality.

Reverse resistance (below), measured from CW

terminal is mirror image of curve of normal

control- measured from CCW lug, curve

is pivoted top -to- bottom.

100

9

1

-°

a

`,°'o

\oo i Pp.I,ÌI

P

Z

QhI

.,,///.33

AL,

Ariii,

;,,1,

/ MINN

.R' I,L'V®'

,%1

oV

?

/%í' _', /- _ . :. e

PERCENT OF ROTATION

minal. Normally when the contact arm (in

the variable control) is at the CCW terminal

you think of the control as being off, and

when the contact arm is at the CW terminal

you think of the control as being full on.

Left -hand tapers are most commonly used

in electronic equipment.

Design An Attenuator. Now that we

have learned about controls in general let us

use this knowledge to design and build a sim-

ple attenuator. This attenuator is basically

a potentiometer connected to the grid circuit

of a tube. Actually a potentiometer or varia-

ble resistor can be used in many circuits. To

be most effective the resistance of the var-

able control should be nearly the same as the

impedance of circuit to which it is connected.

In other words if you were building a grid -

circuit attenuator the resistance would be

93

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CW r ".1

J31

CCW

AUDIO

GENERATOR OR

0- I011/60 CYCLE AC _ J AC VTVM

ATTENUATOR OR DB METER

Internal wiring of attenuator

(above) is contained within the

dotted lines. Connections to

equipment shows calibration

setup. Some of the controls

tested are shown at left with

screwdriver -adjusted resistor

connected to potentiometer lugs.

Typical volume -control circuit,

used in most inexpensive radios,

is shown at upper left.

94

.1 11,11111111111111111111111111111111111111111111.

PARTS LIST FOR 6

J1, J3 -Red 5 -way binding post (Lafayette

99G6233)

42, J4 -Black 5 -way binding post ILafayette

99G6233)

R1 -1 -meg potentiometer (Centralab C2; Mal-

lory M201; Clarostat Y)

R2- Trimmer resistor (Mallory MTC -see text)

RESISTANCE TAPERS

General Centra -Claro- Mallory Mallory

Description lab stat Dist. Co. Conts. Co.

Linear C-1 S 4 M-101

5% Audio Y M-201

10% Audio C-2 Z 1 M-204

15% Audio M-205

20% Audio C-4 W M-206

25% Audio M-207

30% Audio M-208

40% Audio C-6

Right hand T Reverse

30% Audio M -208

Right hand C -5 V Reverse

20% Audio M -206

Right hand C -3 2 Reverse

10% Audio M -204

o

..,, E ii/I

PZjEN/ \. . d Il I P %

FA MIMI

Q,4,`' ..

10 20 30 40 50 F,() 70 A0 90 100

100

83 Q1A-,

66 6

w

50 LL o

33w

16

PERCENT OF ROTATION

Curves of resistance and attenuation do not coincide

except at minimum and maximum points on graph.

0 -DB ATTENUATOR

1- Plastic box (Harry Davis Molding Co., type

220; Newark Electronics Corp., 26F1451

1 -Knob (Mallory 368 -1)

1 -Dial plate (Mallory 390)

Misc. -Sheet aluminum for box cover, wire,

solder, etc.

Estimated construction cost: $4.00

Estimated construction time: 1 hour

ABBREVIATED TABLE OF RATIOS

Resistance

Ratio db

Voltage

Ratio

Resistance

Ratio db

Voltage

Ratio

1.0 0 8.0 18.06

2.0 6.02 9.0 19.08

3.0 9.54 10 20.00

4.0 12.04 100 40.00

5.0 13.97 1000 60.00

6.0 15.56 10000 80.00

7.0 16.90

very high, while if the attenuator were used

in a speaker circuit its resistance would be

very low.

A Ratio. The total attenuation of a varia-

ble resistor is determined by the ratio of the

residual resistance at the CCW end (which is

the Minimum resistance of the control) and

its total overall resistance. In other words a

one -megohm variable control with a mini-

mum resistance of 1000 ohms would have a

ratio of 1000 to 1. By consulting the volt-

age -ratio column of a standard db chart you

would find that a ratio of 1000 is equal to 60

db. (You may have some objections to the

above statement because we are converting a

ELEMENTARY F.I.&CTRONICS

www.americanradiohistory.com

resistance ratio to decibels. This method is

perfectly logical and has been confirmed ex-

perimentally.)

Due to manufacturing processes all var-

iable resistors have wide variations in actual

resistance values. The most common resis-

tance tolerance is ±30 %, while ±20% is

often used, but ±10% is available only on

special order. The only way to design an at-

tenuator for an exact amount of attenuation

is to look up the voltage ratio for the db at-

tenuation you want. Then carefully measure

the resistance of the control you intend to

use and divide by the voltage ratio previously

used. This answer will tell you the CCW end

resistance needed. If the measured end (resid-

ual) resistance is less than that needed you

can add a trimmer resistor to make up the

difference. Adjust the trimmer until the CCW

end resistance is cgrrect. The circuit diagram

will help you here. Refer to it on the page

opposite.

Any technician or experimenter can use

the methods outlined in this article to make

attenuators of any desired resistance or

range. By using the following example you

can get a better idea of what we mean. The

photograph shows a plug -in 60 -db attenuator

built and used by the author in experimental

audio work. A dial plate allows the control

to be set for each 10% of rotation and a

calibration chart supplies the amount of at-

tenuation. A 0 -10 -volt AC voltage source is

needed for calibration as shown in the cir-

cuit diagram.

This supply can consist of a 12 -volt fila-

ment transformer in series with a variable -

voltage transformer or, in a pinch, a tube

tester could be used to supply the necessary

voltages for the setup.

The control used measures 1,113,000

ohms overall, so a trimmer resistor was

added, in series, to adjust the CCW -end resid-

ual resistance to 1,113 ohms. The control has

a 5% audio taper and by looking at the graph

titled "1 megohm, 5% Audio Taper Carbon

Control" you can see both the resistance and

attenuation curves. The attenuation curve is

far from linear. By measuring all the con-

trols shown in the photograph we were able

to determine that a control with a 21/2 % au-

dio taper would give a nearly linear attenua-

tion curve.

The parts needed to make the attenuator

shown are in the parts list. The suggested

variable resistors specified will give nearly

linear attenuation curves. This small device

can be used in the circuit shown for the grid

potentiometer attenuator. It can be used be-

tween the output of an audio signal and an

audio amplifier when plotting a response

curve.

Note! Potentiometer, variable resistor, and

variable control all mean the same thing and

are used interchangeably. So don't do any

betting about which is right!

SPEEDY READIN'

The National Cash Register Co., a major pro-

ducer of computer systems, makes a high -speed

unit that prints 1,000 lines (of 120 characters each),

in a minute -starting and stopping the paper at

least 1,000 times a minute. Otherwise the lines of

characters being printed would be blurred, unread-

able smudges.

Special silicon -alloy steels from Allegheny Lud-

lum Steel Corp., Pittsburgh, Pa., are used in parts

of the drive units that bring paper tape to a halt

for the fraction of a moment needed to read the

tape or print the answer.

Computers can deposit worker's pay directly to

their bank accounts, eliminating payday lineups

and individual distribution of checks at the plant.

Think what would happen if the computer informa-

tion were not legibly printed so it could be under-

stood. Chaos would occur if the tapes and papers

that whirl through printer and reader systems were

not accurately controlled -and NCR engineers say

still higher speed is needed to record and recall in-

formation to reduce computer- services costs.

The tape in the NCR computer unit is read

at a rate of 1,000 lines per minute.

High -speed is made possible by special

silicon -alloy steels made for the electrical

and electronics industries. These special

"electrical" steels are used in clutch plates

and brake shoes requiring high performance

and exceptional wear resistance.

JULY -AUGUST, 1966 95

www.americanradiohistory.com

Using questions

typical of the type

asked for all FCC

exams (commercial or

amateur) you can

prepare yourself for

that big day.

by

Carl L. Henry

96

FCC

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

Here we are going to discuss questions you

will encounter on tests for all classes of FCC

operator's licenses, whether amateur or com-

mercial. The questions will be of the type

asked by the FCC on its exams; the answers

will be in depth. Rather than the convention-

al type of question and answer, we intend

to cover each subject with answers that will

help you to learn the subject fully.

For a beginning we are going to discuss

FCC questions covering the single most im-

portant part of the transmitter, the oscillator.

It is evident that the frequency determining

element of a transmitter is its most important

section, since without accurate frequency

control communications would be at best in-

termittent and at worst impossible. Most

questions asked on the FCC exams, about

oscillators, are concerned with testing: 1.

do you know what an oscillator is? And: 2.

do you know how to keep it on frequency?

The new terms Hertz (Hz), KiloHertz

(KHz), and MegaHertz (MHz) are given

after the long -used terms cycle -per- second

(cps), kilocycle -per- second (kc), and mega-

cycle -per- second (mc) to familiarize you

with them.

Q. What is the relationship between fre-

quency and wavelength?

A. Frequency, in cps (Hertz) = 300,000,-

000 /wavelength (in meters), or frequency,

in mc (MHz) = 300 /wavelength (in meters).

This is a simple relationship that you should

memorize. The second formula is the one to

remember. You will use this most, and the

other can be developed from it. As a further

aid to memory, recall 30 mc (MHz) equals

10 meters, or 300 mc equals 1 meter.

Q. Why should an oscillator, in a typical

transmitter, have a separate plate -supply?

A. Using a common plate -voltage supply in

a transmitter can cause frequency modula-

tion of the oscillator. Variations in the plate

voltage, due to variable loading (current

drawn) on the power supply by the final

amplifier. This does not mean that an en-

tirely separate power supply must be used,

just that the section supplying the oscillator

should be isolated from the balance of the

supply by a regulator. This can be a tube,

such as an OD3. In this manner the voltage

variations (due to the loading on the supply)

will not be reflected to the oscillator.

Q. Draw a diagram of a crystal -controlled

oscillator.

JULY- AUGUST, 1966

A. Study Fig. 1 carefully. Generally on

questions such as this a diagram will be given

that is incorrect, and you must correct it.

This circuit may be redrawn several ways,

but basically the plate (and screen if it is a

pentode) must be connected to the B +, the

cathode to the B- or ground; and the crystal

either as shown, grid to ground, or for a

Pierce circuit, grid to plate. There must be a

plate load, either a resistor, a choke, or a

tuned circuit. An important point to remem-

ber about crystal oscillators is that this is the

only type of oscillator for a Novice.

Q. A crystal for the 80 -meter band is spec-

ified to be within 0.05% of its stated fre-

quency. What is the lowest frequency you

should order to stay within the lower limit

of the band, allowing an additional 1.0 kc

(KHz) for temperature and circuit parame-

ter variations; assuming you wish to operate

just inside the band at this lower limit.

A. A simple formula to solve this problem is:

frequency (lower band limit)

1 - crystal tolerance + 1.0 kc (KHz)

Using this formula:

3500 kc (KHz)l

1 - 0.0005, + 1.0 kc

= 3501.6 + 1 or 3502.6 kc (KHz)

If the question is specified to the nearest kc

(KHz), the answer would be 3503 kc. If

the answer had been 3502.4 kc to the nearest

kc, the answer would still be 3503 kc. Since

the FCC expects any operator to err toward

the direction of maximum safety.

Q. A 3800 kc (KHz) low -drift crystal hav-

ing a negative temperature coefficient of

5 cps (Hz) per mc (MHz) per degree Centi-

grade is started in operation at 40- degrees

Centigrade. If the relationship is linear,

what will the frequency of the crystal be at

65 degrees?

A. Negative temperature coefficient means

that the crystal will shift down in frequency

XTAL

RF

OUTPUT

TANK

CIRCUIT

B+

SCREEN BYPASS° `SCREEN DROPPING

CAPACITOR - RESISTOR

Fig. 1. Diagram of a crystal- controlled oscillator.

97

www.americanradiohistory.com

FCC Q &A

Fig. 2. Bask diagram of ECO and

AM defector Frequency Meter.

%L1

I

C)

e SCREEN

BYPASS

CAPACITOR

vl

SCREEN

DROPPING

RESISTOR

with increasing temperature. Here it is speci-

fied as 5 cps /mc /degree. The temperature

change is 25 degrees, so the frequency shift

is: -5 X 25 X 3.8 mc, or - 475 cps (Hz).

So if the relationship is linear, the new fre-

quency will be 3799.525 kc (KHz).

Q. Draw a schematic of a simple heterodyne

frequency meter with provision for monitor-

ing transmitter output.

A. The circuit in Fig. 2 is of an electron -

coupled oscillator. /The frequency of the os-

cillator is determined by the parallel LC net-

work in its grid circuit. (These components

must be selected for high stability for use in

a frequency meter.) The output of V1 (the

ECO) is coupled to the input of V2, the sec-

ond stage, which is an AM detector. The

signal to be measured is also coupled to V2's

input, and the beat between the ECO and

the frequency being measured is heard in the

earphone. The ECO is adjusted for zero beat

with the transmitter's frequency, and the ac-

curately measured frequency is read off the

ECO dial. Transmitter output (modulation)

can also be monitored by V2, which is then

acting only as an AM detector.

Q. What device is used to derive a 10 -kc

signal from a I00 -kc oscillator?

R

SIGNAL INPUT

IC

PLATE

LOAD

RESISTOR

B+

V2

CATHODE

BIAS RESISTOR

HEAL,-

PHONE

A. The device is called a frequency divider.

(See Fig. 3.) This is a type of multivibrator

(RC oscillator) that will lock -in on a sub -

multiple of an input signal supplied to it.

The values of resistance and capacitance are

calculated to cause oscillation at the desired

frequency. A known- accurate signal is then

applied to one of the grids at some multiple

of the desired output, in this case 100 kc (or

KHz). If the input signal amplitude is great

enough the output signal will lock -in with

the input at some submultiple, and this out-

put signal will have the same percentage of

accuracy as the input signal.

Q. Draw a schematic of a basic multivibra-

tor.

A. See Fig. 3. The test will have a diagram

such as either of these, with something miss-

ing or drawn incorrectly. Study the sche-

matics carefully. Both circuits are identical

and both methods of drawing are correct -

either may be used.

Q. For maximum stability, how should the

tuned circuit of a crystal be tuned?

A. At the exact plate -current dip point, or

resonance, the oscillator will be critical, and

slight circuit changes may cause it to stop

oscillating. If the tuned circuit is adjusted

Fig. 3. Basic multivibrator circuit can be drawn in more than

one way. In amplifier -like layout (below) Cl handles

feedback. Cross -coupled layout (left) is correct too.

98 ELEMENTARY ELECTRONICS

www.americanradiohistory.com

to slightly above the resonant frequency, this

instability will be reduced or prevented.

Q. What advantage has a mercury thermo-

stat (used for temperature -controlled crys-

tals) compared to a bimetallic thermostat?

A. Mercury contacts are not subject to pit-

ting or corrosion.

BIAS RESISTOR

V1

RFC

PLATE

COUPLING

OUTPUT ;

Fig. 4. Hartley oscillator has tapped coil for

feedback voltage divider. Remember H for Hartley,

and H for Henry (unit of inductance in a coil).

Q. Draw a diagram of a Hartley and a Col -

pitts oscillator.

A. The Hartley oscillator is given in Fig. 4-

the Colpitts in Fig. 5. These are shunt fed

oscillators. The diagrams on the test may be

either shunt or series fed. The tube may be

a triode or a pentode ECO.

Fig. 5. Colpitts oscillator has series capacitors in

feedback voltage divider. Remember C for Colpitts,

and C for Capacitor and you can't go wrong.

Q. What precautions should be taken to

prevent a crystal from oscillating at a fre-

quency other than its fundamental?

A. 1. Use a buffer amplifier between the os-

cillator and its load.

2. Regulate the plate voltage supplied to

the oscillator.

3. Keep the temperature of the crystal

constant.

4. Keep feedback in the oscillator to the

minimum needed to maintain oscilla-

tions.

5. Keep all parts of the oscillator me-

chanically rigid.

JULY- AUGUST, 1966

Q. At what frequency will an X -cut, 600 -kc

(KHz) crystal oscillate when it has been cali-

brated at 50- degrees Centigrade, has a

temperature coefficient of -20 parts per

million per degree, and its temperature has

been raised to 60- degrees Centigrade?

A. It will oscillate at 599.88 kc (KHz). The

temperature coefficient is -20 cps (Hz) per

mc (MHz) per degree. It will shift -200

cps per mc, or -200 X 0.6 = -120 cps.

Subtract this from the original frequency.

Q. What are the operating characteristics

of the electron -coupled oscillator?

A. The electron -coupled oscillator has its

input (or grid) circuitry buffered from the

variations in load which occur in the output

(plate) circuitry -a tube with a screen and

suppressor grid is used. Interaction from out-

put to input circuitry occurs through the

grid -to -plate capacitance of the tube. The

addition of the other grids substantially re-

duces this capacitance. Hence the stability

of the ECO is better than other types of LC

oscillators, but it still has less stability than

a crystal oscillator.

Q. Using a frequency meter known to have

a possible error of 0.1%, what is the highest

frequency on the 3500 -4000 kc band to

which an amateur transmitter can be safely

set?

A. The same simple formula that we used on

the crystal band -edge problem can be used

here:

frequency (indicated by meter)

= 4000/1 + 0.001

or for the low end of the band:

frequency (indicated by meter)

= 3500/1 - 0.001

Do not add an error factor of 1.0 this time

since it was not specified.

Q. Why are quartz crystals sometimes oper-

ated in temperature controlled ovens?

A. Since the frequency of crystals vary with

temperature, the crystal temperature is kept

constant by enclosing the crystal in an in-

sulated box (called an oven) which contains

a heater and a preset thermostat. Ovens are

usually purchased with the controlled tem-

perature specified. Usual practice is to keep

the crystal temperature above the highest

possible ambient temperature that the unit

will encounter, in order to give the oven

thermostat a good control margin.

99

www.americanradiohistory.com

GAD hear a flutter as the secondary standard beats

FCC Q &A with the modulated carrier. Slightly adjust

the secondary standard until the flutter is as

slow as possible. (In some cases, an oscillo-

scope can be used to see the beat directly.)

Q. What procedure should be followed if Now zero beat the secondary standard with

it becomes necessary to replace the tube in the oscillator's frequency, following the man -

a heterodyne frequency meter? ufacturer's instruction for using the second -

A. Changing any of the oscillator compo- ary standard. Use an oscilloscope to obtain

nents will affect the calibration. It should be an exact zero -beat at the output of the mixer

checked and recalibrated if necessary. in the secondary standard. If interpolation is

necessary, such as when the secondary stand -

Q. Explain, in detail, how oscillator fre- and is crystal controlled and not variable,

quency is measured, using a secondary feed the output of the mixer into the vertical

frequency standard. input of an oscilloscope. Connect an accu-

A. The first step is to verify the accuracy of rate audio oscillator to the other horizontal

the secondary standard. Tune in one of the input of the oscilloscope, and adjust the os-

standard- frequency station on a receiver, cillator to get a known ratio Lissajous pat -

and loosely couple the secondary standard tern on the screen. Add this interpolated

to the receiver antenna. When the trans- frequency to the known frequency of the

mitted modulation goes off the carrier zero- crystal. Using this method it is necessary to

beat the secondary standard against the car- have a rough idea of the oscillator frequency

rier. When the modulation returns, you will before making the measurement.

$

lt's a

Woman's

World?

by

Jack Schmidt

" . and where

did you get

that kit ?"

ff

. i 33 -

n ç

3

ç I

\\

100

"OK, you can get the antenna rotor... .

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

Civilian plans

for this

SATCOM

network are

still up in the

air but easily

set up units do

promise better

education for

under-

developed

areas around

the world.

Was a day when you could build a radio

network and it would stay put. But that day,

alas, is now part of a dim and mildewed

past. For the new mode in networks is the

portable look. A network with transmitting

and receiving terminals that can be folded

up like a tinker toy, loaded on a plane, flown

half way round the world, unloaded, reas-

sembled, and put back in business within 48

hours.

Come Fall of this year, a fleet of commu-

nication satellites will be launched into space

by the United States Army. These -the first

world -wide satellite communications -will

relay radio, teletype messages, and facsimile

photographs to portable terminals spotted

round the world. And each portable rigged

to transmit and receive over four voice

channels, four teletype channels at the same

time. Designed and built by Hughes Aircraft

Corporation, the new type network is in

the Army now, but when it changes to civ-

vies, it might well do its bit to aid the world.

For its principles converted to telecasting

might prove the missing lint in finishing the

needed world -television network.

For when SYNCOM became operational,

international television was feasible techni-

cally. But there was an important handicap.

One of the major motives in creating such a

network would be the intention to telecast

JULY-AUGUST, 1966

education to peoples in hungry areas of the

world, to help people help themselves.

For the screen could teach people to read,

write, and use simple tools in areas where

illiteracy breeds poverty. It could show the

people how to increase the yield from the

land, multiply their food supply to help meet

multiplying population needs.

But one thing lacking was the means to

place receivers in the backward areas, areas

handicapped by insufficient power supply,

and limited or non -existent transportation

facilities. Once this portable "network" de-

sign could be transferred to transmitting the

television picture, portable receiving stations,

transported by plane, could reach these re-

mote areas.

Until we can see a portable television net-

work, the new restless network will have to

win its stripes as the first world satellite com-

munications network, limited now to military

use but promising all sorts of implications in

the future.

How the idea was conceived. It hap-

pened like this: With today's constantly

changing political, economic and military

climates, communications can no longer stay

static.

One day a transmitting- receiving "station"

may be needed in Alaska. A few weeks later,

one may be necessary in a remote spot in

Africa, or in the Far East. A few months

101

www.americanradiohistory.com

Q NETWORK ON PROWL

AA111

later, none of these terminals may have any

use at all in their areas. But the Army cannot

travel around the world, building and then

abandoning transmitting- receiving stations.

The only practical solution: a portable

broadcasting network.

Hughes built a terminal station consisting

of a 40 -foot diameter parabolic antenna, the

largest of its kind in the world. Each antenna

is protected from hostile weather conditions

by a dual -wall inflatable radome 58 feet in

height. In operation, each antenna can with-

stand winds of 60 mph; when not in opera-

tion, it can withstand winds of 120 mph.

Three thirty -foot mobile vans service each

terminal, and three 100 kva Diesel genera-

tors supply power. An operations van car-

ries control console and electronic equip-

ment. A cargo van, the radome and reflector;

the maintenance van, spare parts and test

equipment.

One terminal is ready, built at Helemano,

Hawaii, 20 miles north of Honolulu. This

one will broadcast between Hawaii, and the

United States, serve as relay to and from

terminals spotted through the Western Pa-

cific. Another portable -also in the Army, and

also a brainchild of Hughes Aircraft -

doesn't need a plane to get around. It travels

on the back of a soldier, has 10,000 voice

channels, and can strut its stuff in the dens-

est jungle.

102

Cocoon -like radome, with one section peeled

open, houses ground -link terminal of SATCOM net.

Technicians, dangling in bosun chairs (left),

are dwarfed by 40 -foot diameter parabolic antenna.

Air -transportable terminal is set up in 48 hours.

Called "Manpack," it is transistorized,

weighs a neat 29 pounds with wet cells, is

18 inches high, 12 inches wide, and 334

inches thick. The solid state pack has a 2

to 12 megacycle range, its channels offering

a frequency flexibility meant to confuse any

jamming enemy.

The portable's high frequency signals re-

flect from the ionosphere, to give longer

range than line -of- sight, so that its HF sig-

nals are effective in the most difficult moun-

tain or jungle country where very high or

ultra -high signals would fail. Reason for its

plus portability is it can run on ordinary

flashlight type dry cell batteries or on wet -

cell batteries.

According to field tests, its influence

reaches far. Not around the world as the

portable network will, but one test broad-

cast succeeded between points 500 miles

apart. And Senior Vice -President of Hughes

Aircraft, C. Harper Brubaker, says, "We

even have received clear transmission at our

Fullerton (California) facility from a 'Man -

pack' broadcasting from more than 7500

miles away."

When this distance "Manpack" and the

traveling network turn civilian, will we see

a world -wide satellite network that will rele-

gate our presentday stay -at -homes to an

antiquated past? A network that will broad-

cast from the most remote areas, hop around

the world at will.

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

DX

CENTRAI,

REPORTING

Here we are again with a report on the

most interesting aspect of short wave listen-

ing, the "utility" stations. This includes all

radio transmitters with the exception of

broadcast stations and Hams.

Just for kicks this month, let's look at

some of the more interesting stations oper-

ated by U.S. and Canadian federal and state

governments.

For instance, there's a "mystery" net of

government stations which we keep hearing

on 5422.5 kc. Calls are KAE310 (in New

York), KAE311 (Boston), KAE312 (Mi-

ami), and others in San Juan, San Francis-

co, Honolulu, Seattle, San Diego, Chicago,

New Orleans. See if you can figure out who

operates this net. We know that it's the gov-

ernment, but which agency?

NBS. Do your friends have QSL cards

from the National Bureau of Standards sta-

tion WWV? You can send them into tail-

spin by betting that you know NBS (Nation-

al Bureau of Standards) stations which they

can't name. First they'll say WWVH (Ha-

waii), then WWVB and WWVL (Colora-

do). You'll still be two up on them. It's

never before appeared in print, and it isn't

generally known, but the NBS operates sta-

tions KGD28 (7975 kc) and KGD29

(10687.5 kc) in Sterling, Va. These aren't

WWV -type stations, but regular 2 -way

'phone stations used to communicate with

the NBS office in Boulder, Colorado. An-

other little -known NBS station is KQ2XAU

(6080 kc) in Cincinnati, Ohio. Lord knows

why the station exists, but they can often

be heard with a "dead carrier" on the fre-

JIILY-AIICIIBT, 1966

quency when it isn't being used by the Voice

of America station in Bethany, Ohio. The

callsign, KQ2XAU, is sent each half hour in

CW. They run 1,000 watts into a vertical

antenna. A QSL can be obtained by sending

a detailed reception report to the National

Bureau of Standards in Cincinnati.

The Canadian Government has a well

known "time" station which sends out a

nifty QSL. Station is CHU which operates

on a 24 -hour basis as follows 3330 kc (300

watts), 7335 kc (3 kw.), and 14670 (300

watts). Their time signals consist of a series

of CW dots, with voice announcements each

5 minutes. Send your reports to: Station

CHU, Dominion Observatory, Department

of Mines and Technical Surveys, Ottawa,

Ontario.

Weather. Stations of the United States

Weather Bureau offer interesting listening,

especially during the hurricane season. The

hurricane net operates on 2776 and 6977.5

kc and is really in full swing when the big -

blow is at its height. Listen for these stations:

KAE46 Athens, Ga.

KAE51

KEB86

KEB87

KGD64

KGD68

KGD72

KID75

KOE26

KC6222

Nantucket, Mass.

Cape Hatteras, N. C.

Athens, Ga.

New Orleans, La.

Washington, D. C.

Nantucket, Mass.

New Orleans, La.

Mobile Station #2

There are plenty of other Weather Bu-

reau stations besides this particular net, but

they aren't reported as frequently.

Right after a hurricane or any other major

emergency, you can dig the sounds of the

massive Civil Air Patrol radio network. The

CAP stations may be heard on 2374, 4467.5,

4507.5, 4585, and 26620 kc. Most of the

time the stations use "tactical" (name) calls

such as "Yellow Jacket 205," "Beaver Bird

(Continued on page 107)

CHU

THANK YOU FOR YOUR

REPORT OF THE DOMINION

OBSERVATORY'S VOICE

TIME SIGNAL OW-

3330 kc.

7335 ke.

14670 ke.

DOMINION OBJERVATORY

OTTAWA CANADA

Nifty QSL from Canadian "time" station isn't hard

to get if you're set up in o good reception area.

103

www.americanradiohistory.com

104 ELEMENTARY ELECTRONICS

www.americanradiohistory.com

Electronic "brains"

make the split -second

decisions for these

high -speed

passenger trains

for Canada.

JULY -AUGUST, I966

For the first time in the long history of

transportation, we will apply "brains" to

running our railroads. For a new pushbutton

train, the first of its kind, a train that will

first a series of new -era models, will soon

make its debut.

When the World Exhibition in Montreal,

Canada, opens next year, a sleek, new six -

car automated passenger train, named Expo

Express, will pick up visitors at the Mackay

Pier in Montreal Harbor, speed them by

"brainpower" to the Fair site on an island

in the St. Lawrence River.

A streamlined job that will carry as many

as 30,000 passengers an hour, it will run on

electronic judgment and power 99- 44/100's

of its time, relying on the more fallible hu-

man variety for the remaining fraction.

The Thinking Man's Train. To get low-

down details on this exciting new train trend,

we went to VIPs in the Union Switch and

Signal Division of the Westinghouse Air

Brake Company, pappa- creator of the new

train. And we were told the master key to

the eight -car Montreal model will combine

electronic with human brain at the main con-

trol center.

A key dispatcher, or supervisor, will push-

button the system of eight trains at the Fair

from a computer console. A huge illuminated

map hanging high on the center wall will

show where each train is at each second,

show its direction, destination and speed.

When the dispatcher sees Train A should

head for location B, he will press a button

that will light a sign standing on the plat-

form next to the train signalled. The attend-

ant in the train's cabin will watch for this

go- ahead, let passengers board, close the

elevator -type doors automatically, then push

still another button.

In response to this signal, wayside trans-

mitters will send low- voltage, audio -fre-

quency impulses down the uninsulated steel

rails. Impulses will be picked up inductively

from the rails by electronic hardware inside

the train, automatically controlling start,

speed and stop when preset destination is

reached.

The on -train mechanism that controls

propulsion power and brakes the train is a

servo -mechanism, a velocity control pro-

grammer answering commands from cab,

speed and wayside control. The attendant

inside his cab can watch speed on an indica-

tor panel, check with the main console center

through a voice -communication set -up.

At the end of each system at the Fair, there

105

www.americanradiohistory.com

GM HAVE BRAINS

will be track stub -end terminals with dia-

mond cross -over, switch -over set -ups. Inter-

locking will also be automatically controlled

so that trains will have their chosen station

berths as they move into terminal, the

switches positioned automatically for in -and-

out moving. This speedy system, WABCO

experts believe, will accommodate the most

passengers in the shortest period of time,

dispatching a train every 150 seconds.

The Weak Link -Man! Though Westing-

house Air Brake engineers claim they can

fully automate their wonder train now, they

have, in this generation stage, resorted in a

moment of temporary weakness, to limited

human assistance. For each attendant is

trained to take over manually in case of

what WABCO calls "abnormal" electronic

behavior assuring a "fail- safe" system for

passengers.

But while Expo will be faster, safer and

miles ahead of the chugging furnace that

first panted across the continent in the

eighties, its sophisticated ways will only fore-

runner "brainy" jobs we'll see in the future.

Things to Come. Next on the passenger

list, according to U. S. Department of Com-

merce sources, will be a fully- automated

whippet, absorbing many Expo tricks, that

will race across the country at speeds of 200

miles an hour and up. To travel such fan-

tastic speeds, railroaders feel automatic

switch -over is a "must." The human brain

just can't think fast enough to guide a train

that determined. Only the electronic quiz -

kid can catch hep when serious problems

arise such as passenger jam -ups during storm -

time, or after a major sports event, or meas-

uring distances between the speed demons,

106

Carryphone, a

2 -way radio unit

to be used for

communications be-

tween dispatcher,

station areas

and train personnel.

An artist's overall view of the WABCO

transit control center. A small control

console (lower right) faces the large

map display of the transit system. New

information is indicated automatically.

Position and speed of all trains can be

seen and changes made by pushbutton.

or stopping the racers without lurch when

destination is reached.

Too, with multiplied populations in offing

within the next few years, creating megalo-

politan areas where cities will blend into

cities from Boston to Washington, automatic

rendezvous will be needed. An express may

rendezvous often with spur trains moving in

on the main trunk line, or link with other

expresses, or switch to a separate track to

avoid a local.

To achieve such high -paced juggling, train

technicians say they intend to borrow from

space technology, adopt techniques learned

in the Gemini rendezvous program. Then

smaller- branch train -sections can link up

with mainliners regardless of pace. Though

train experts expect linking trains may well

prove more difficult than space maneuvers.

For a Gemini rendezvous is but a single

maneuver while an automated high -speed

train system will need make flawless rendez-

vous many times in 24 hours, regardless of

atmospheric conditions.

But when space technology does rendez-

vous with automated Expo systems, we will

see fantastic speed -up in service that will

make today's train as past -tense as the horse -

and- buggy. And while no one reálly expects

a future train to travel the speed of sound,

we can happily promise models that will at-

tend the funeral of the old black monster we

know today.

And we predict it won't be two -three dec-

ades before today's archaic beast will only be

seen under the shed of a museum. While a

new robot -run fellow will race across the

country, run by pushbutton, one that will al-

ways keep its electronic head.

ELEMENTARY ELECTRONICS

www.americanradiohistory.com

MAD ABOUT MOD

A tiny solid -state device that virtually elim-

inates heat problems in microwave com-

munications systems has been developed by

Sylvania Electric Products Inc. The device,

a MOD (Microwave Oscillating Diode),

smaller than a shirt button, will give en-

gineers considerable latitude in designing and

packaging short -range, low -power micro-

wave radar systems that can be used by as-

tronauts during "docking" of space ships at

satellite stations. The MOD also could be

applied in automobile and boat collision -

control units; missile radar systems and for

transmitting television signals between orbit-

ing spacecraft.

The experimental system's low -power mi-

crowave beam is generated by a tiny solid -

state device which is powered by a standard

30 -volt battery. Together, they represent ap-

proximately 1 /50th the weight of comparable

equipment presently used to produce a mi-

crowave signal in commercially available

systems. The laboratory model was designed

by General Telephone & Electronics Labo-

ratories Incorporated.

lM1 t :i

othullt11,1111111111n111111111111111111111111111,111,,,111,1111.,n1, 1$1111111111111,li,liiili,licilollloili11111111.11,1111,,,,,,,,iiiiiii.ttI.tiiii.iiiiiii,i,;,,,.,.ninim,

DX Central Reporting

Continued from page 103

23," "Star Fish 57," etc.

thousands of stations in There are probably

operation on these

frequencies and you can make an entire DX

career out of listening to the CAP alone.

To the Rescue. The Royal Canadian

Mounted Police do quite a bit more than

chase Snideley Whiplash, you can even listen

to Dudley Doright (ta- tahhhh!!!) and his

friends conducting "Mountie" communica-

tions on a number of frequencies. Most fre-

quently heard "Mountie" stations seem to be

reported on 4785 and 4895 kc. Most stations

heard are in the western provinces.

Getting Out. Getting away from the con-

tinental United States, the U. S. Navy op-

erates station NGD at McMurdo Sound,

Antarctica. They were recently reported on

13874 kc around 0610 GMT working New

Zealand.

Another military station at a distant

"rare" location would be ABK in the Mar-

shall Islands. Operated by the U.S. Army,

they are being reported on 9910 kc (0730

GMT), 13570 kc (0538 GMT), 16370 kc

(0420 GMT), and 17690 kc (0055 GMT).

You can take a whack at getting a QSL,

but there aren't any guarantees about get-

ting one. Try: Chief Operator, Station

ABK, United States Army, Eniwetok, Mar-

shall Islands.

We are looking forward to receiving re-

ports from our readers concerning reception

of "utility" stations on either 'phone, SSB,

or CW. Please include the callsign, frequen-

cy (or approximate frequency), time (in

GMT), etc. You might even send along a

photo of your SWL shack. Who knows, you

might even become immortalized in our

pages.

I111111111111111111111111111111111111111,

Traffic a Go Go

Continued from page 18

turned off or the cartridge is removed.

What's Available? There are already over 20

makes on the market today with new units pop-

ping up like dandelions. They vary from the

simple, early non -stereo 4 -track hang -on models,

which cost approximately $60 installed, to recent

8 -track hang -on types offered at prices up to

$155 installed. Factory -installed cartridge tape

players are available in certain cars for about

$130 -get the exact price from your new -car

dealer.

Tape cartridges have a bright future. Public

acceptance with its mass purchasing has lowered

the unit cost for cartridges to a level which is

competitive with LP's. The demand for home

units is on the increase -more and more tape

cartridges will be made, lowering the price to

where the LP will give ground and eventually

yield to the magnetic ,audio tape.

JULY -AUGUST, 1966 107

www.americanradiohistory.com

HEAiHi<iT 1966

ALL/Ela

.&GRRr+sf.:

Literature Library

ti'r Starred items indicate ad-

vertisers in this issue. Consult

their ads for additional infor-

mation and specifications.

LAFAYETTE

ELECTRONIC PARTS

1. Allied's catalog is so widely used

as a reference book, that it's regarded

as a standard by people in the elec-

tronics industry. Don't you have the

latest Allied Radio catalog? The sur-

prising thing is that it's free!

*2. The new 510 -page 1966 edition

of Lafayette Radio's multi -colored

catalog is a perfect buyer's guide for

hi- fi'ers, experimenters, kit builders,

CB'ers and hams. Get your free copy,

today!

4. We'll exert our influence to get

you on the Olson mailing list. This

catalog comes out regularly with lots

of new and surplus items. If you find

your name hidden in the pages, you

win $5 in free merchandise!

*5. Unusual scientific, optical and

mathematical values. That's what Ed-

mund Scientific has. War surplus

equipment as well as many other

bard -to -get items are included in this

new 148 -page catalog.

*106. With 70 million TV's and 240

million radios somebody somewhere

will need a vacuum tube replacement

at the rate of one a second! Get Uni-

versal Tube Co.'s Troubleshooting

Chart and facts on their $1 flat rate

per tube.

7. Whether you buy surplus or new,

Elementary Electronics 1966 07 08

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