1

DON'T LET COLOR PASS YOU BY

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NAME

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1

)) journal NOV./DEC. 1964

VOL.21, NO. 7

FEATURES

DON'T LET COLOR PASS YOU BY WILLIAM F. DUNN 4

THE CONAR MODEL 280 SIGNAL GENERATOR J.B. STRAUGHN 12

LEAKAGE LIFESAVER JOHN POTTER SHIELDS 20

HAMS AND THE OSCARS REVIEWED ALLENE MAGANN 23

THE LONG AND THE SHORT OF HORNS ARTHUR L. MUNZIG 30

DEPARTMENTS

DEVICE OF THE MONTH R.C. APPERSON, JR. 9

EMPLOYMENT OPPORTUNITIES 19

ALUMNI NEWS 26

WILLIAM F. DUNNEditor and Publisher

ALLENE MAGANN J. B. STRAUGHNManaging Editor Technical Editor

T. E. ROSE RICHARD STANCHIKEditor - Alumni News Art Editor

Published bi-monthly by National Radio Institute, 3939 Wisconsin Ave., Washington, D. C.20016. Subscriptions $2.00 a year. Printed in U. S. A. Second class postage paid at

Washington, D. C.Copyright 1964 by National Radio Institute. All rights reserved.

2

ON OUR COVER

The Grand Coulee Dam, shown on ourcover, is a major facility in a powernetwork along the Columbia River Basinto be linked with a microwave communi-cations system. Due for completionshortly, the system will provide facili-ties for voice and data communications,supervision and automatic control, andinclude 26 microwave relay stations ex-tending between Portland, Ore., andSpokane, Wash. It will provide 72 com-munications channels initially, with anultimate capacity of 600 channels.Lenkurt Electric Co., Inc., a subsidiaryof General Telephone and ElectronicsCorp., is engineering and installing themicrowave system under a $1.7 millioncontract for the U. S. Department of theInterior. Other substantial contractsawarded recently (a list is on Page 19of this issue) mean new jobs in theburgeoning electronics field. We willcontinue to publish such lists from timeto time.

LARGE, SELECT STOCK! DEPENDABLE, FAST SERVICE! Every tube tested In our own laboratory for mutual conductance

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Advertised tubes not necessarily new. but may be electrically per-fect factory seconds or used tubes -each clearly so marked.

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3

DON'T LET COLOR PASS YOU BY

It's A Wise Serviceman

Who Casts His Vote

To Study Up On It

BY WILLIAM F. DUNN

In the late nineteen forties and early fifties,-1- when black and white TV was still an infant,many radio servicemen who had been in busi-ness for years were reluctant to get into TVservicing. Some were afraid to tackle a TVset; others didn't want to make the effort tolearn about TV. Those who decided not togo into TV servicing thought there wouldalways be enough radio service work to keepthem busy. There are very few shops todaythat do only radio work. In most radio -TVrepair shops, the income from TV servicingfar exceeds the income from radio servicing.Today the serviceman has a similar situationfacing him. For years we've been hearingthe statement that color TV is justaround thecorner. We've turned the corner; color TV ishere. Whether you are in servicing on a full-time or a part-time basis, you can be sureyou'll be called onto service a color TV soon,if you haven't been already. Once you tell acustomer you don't do color servicing,or youcan't service a color set, the chances areyou've lost that customer forever. It's likelythat when his black and white receiver or hisradio needs servicing, he'll take it to theman who fixed his color set.

There is no reason why any technician whocan service a monochrome TV receiver can-not, with a little study on his part, learn howto service a color set. If you are a studentworking on your NRI Course, you learn allyou need to know about color TV servicingwhen you study the TV lessons in your course.If you are a graduate, perhaps you skippedover the color TV in your TV lessons; if youdid, now is a good time to review to get readyfor color TV.

THE COLOR SIGNAL

We won't go into detail about the color signalbecause it is described in detail in your les-sons. However, briefly, the color signal con-tains the same signals present in a blackand

white picture transmission plus the color sig-nal. The color information is transmitted ona subcarrier which has a frequency of 3.58mc (approx.). This subcarrier modulates thepicture carrier so it is transmitted in the TVchannel at a frequency which will be 3.58 mcabove the video carrier frequency and ap-proximately .92 mc below the sound carrierfrequency.

The 3.58 mc color subcarrier is both phaseand amplitude modulated. The phase modu-lation determines the color, for example red,green, or blue and the amplitude determinesthe saturation, for example whether the coloris a deep color or a pastel color.

In transmitting the color signal, only thesidebands are transmitted. The 3.58 mc sub -carrier is suppressed. Thus the actual colorsignal that is transmitted will be the sidebandsthat vary in amplitude and are displaced inphase from the reference color subcarrier.To detect the difference in phase between thesidebands and the color subcarrier, the TVreceiver must have some means of deter -

O

HORIZONTALSYNC PULSE

BURST OF3 58 M C.

mAN OI CYCLISI

HORIZONTAL BLANKING INTERVAL

0FIG. 1. A is the sync pulse transmitted for a black

and white picture; B the sync pulse for color.

4

mining what the phase of the subcarrier is.To do this some reference signal is neces-sary. The reference signal is transmitted onthe rear porch of the horizontal sync pulse.The sync pulse transmitted for a black andwhite transmission is shown in Fig. 1A. Thehorizontal sync pulse transmitted for coloris shown in Fig. 1B. Notice onthe rear porchof the signal there is a sine wave consistingof 8 cycles. This sine wave is calledthe colorburst --it is used to transmit to the receiverinformation on the phase of the 3.58 me colorsubcarrier so the receiver can determineany phase difference between the sideband itreceives and the color subcarrier.

The color signal and the 8 cycle referenceburst are the main differences between acolor transmission and a black and whitetransmission. The video signal transmittedon a color broadcast is the same as the videosignal transmitted in a blackand white trans-mission. This is why a black and white TVreceiver receives a black and white pictureduring a color broadcast. Bothhorizontal andvertical sync pulses are transmitted bothduring color transmissions and black andwhite programs. While the frequency of thepulses is slightly different for color broad-casts, this is of no importance either inunderstanding color or in the operation ofthe receiver. The sound transmission is thesame in both color and monochrome.

THE COLOR RECEIVER

Basically a color TV receiver is a black andwhite TV receiver with some extra stagesadded to it. In fact, some of the late modelcolor TV receivers have fewer tubes anthemthan some of the early model monochromereceivers.

Fig. 2 is a block diagram of a color TV re-ceiver. The shaded stages are the stageswhich will also be found in a black and whiteTV receiver. As you can see, many of thestages found in a color set are also found ina black and white set. The defects encounteredin these stages are the same as those foundin monochrome receivers and for the mostpart their symptoms are the same. From aquick look at the block diagram you can seethat if you can service a monochrome re-ceiver you can service at least half of thestages in a color receiver.

Now let's briefly go through the stages thatare found both in color receivers and mono-chrome receivers to point out differencesbetween the stages, and later we will discussbriefly the stages found only in color re-ceivers.

ii

5

The TunerThe tuners used in color sets are identicalto the tuners used in monochrome receivers.In fact many a manufacturer will use the sametuner in all the models he is currently manu-facturing.

Th Video AmplifierThe video 1-f in a color receiver will usuallyhave one more stage than the video i-f in ablack and white receiver. In addition it isaligned to give a somewhat wider bandwidth.In a color receiver that has a 45.75 mc pic-ture i-f and a 41.25 me sound 1-f the colorsubcarrier 1-f will be 42.17 mc. To get color,the i-f pass band must pass this frequency.

The response curve of a typical video i-f ina color receiver will look like the responsecurve shown in Fig. 3. Notice that both the

42.17 se

41.25.,

45.75oc

47.25ma

FIG. 3. Response curve of a typical video i-f in acolor receiver.

45.75 mc picture i-f and the 42.17 mc color1-f are about midway up on the response curve.

The alignment of the video i-f in a color re-ceiver does not present any special problem.If you have the instruments needed and knowhow to align a monochrome receiver youshould be able to align a color set.Of course,you never align any TV set unless you aresure it needs alignment, nor should you tryto align a TV if you do not have the alignmentinstructions and the required test equipment.

Th Video DetectorThe video detector in a color set is identicalto the video detector in a monochrome re-ceiver.

Th Sound I -F, Detector and Amp-lifierThese stages are identical In both color andblack and white. However, the 4.5 me soundis usually taken off the last video i-f stage ofa color receiver rather than at the video de-tector output as in a monochrome receiver.This is done to prevent the 4.5 mc sound

from beating with the 3.58 me color signaland producing a 920 kc signal which wouldput an interference pattern on the face of thepicture tube.

Th Video I -F AmplifierThe video amplifier in a color receiver is thesame as the one in a black and white set withthe exception of a delay line which is used incolor receivers. This is used to delay the sig-nal going directly through the video amplifierto the picture tube so it will arrive at thetube at the same time as the color signalgoing through the various color stages. Adelay line is simply a combination of induc-tance and capacity that delays the signal fora fraction of a microsecond.

Th Sync SeparatorThe sync separator stages in botlitypes ofsets are identical. They both perform thesame function. At first glance at a color setyou might think a more elaborate stage isused, but just as elaborate sync separatorsare often found in the more expensive blackand white sets.

Th AOC StagMost color sets use some form of keyed agcsimilar to that used in the better monochromereceivers. This stage, however, can be omit-ted from both types and a manual gain con-trol substituted.

Th Vortical SwpThe vertical oscillator in a color set is usu-ally the same as that found in monochromereceivers. The output stage is basically thesame, however, provisions are made for con-vergence signals. We'll see why they areneeded later.Horizontal SwpThe horizontal oscillator and oscillator con-trol stages are identical in both types. Theirpurpose and operation are the same. Thesweep output tube is a huskier tube in thecolor set because a much higher high voltageis required to operate the picture tube. Otherthan the huskier tube there is not much dif-ference between the two types of sets.

In the horizontal circuit of a color set thereare also convergence signals. We'll discussthese signals later.High Voltage SupplyThe high voltage for the color tube is obtainedfrom a flyback type of supply as in a mono-chrome receiver. However, the high voltagein a color set is considerably higher than ablack and white set --usually it is about 24,000volts.

The high voltage in a color set is regulated

6

by means of a shunt regulator that is notfound in monochrome receivers, The purposeof the regulator is simply to keep the highvoltage at a constant value so thatthe picturetube can be adjusted to give perfect colorregistration.

Also in the power supply of a color set you'llfind a focus rectifier. The modern three -guncolor tube uses electrostatic focusing. Thevoltage required to focus the tube is severalthousand volts and this can best be obtainedfrom a separate focus rectifier. It works justlike the high -voltage rectifier in a mono-chrome receiver.

COLOR CIRCUITS

Up to this point we have primarily been point-ing out the similarities and small differencesin sections and stages of color and black andwhite sets that are similar in both sets. Nowlet's briefly look at some of the circuits foundonly in color sets. Remember detailed in-formation on how they work can be found inyour regular lessons. Here we are going todiscuss them briefly and give a few examplesof what happens when a defect develops inthese stages.

Color AmplifierThe color amplifier is similar to an i-f am-plifier tuned to 3,58 mc and having a bandpass of from about 700 kc to 1.5 mc. Themaximum bandwidth used to transmit colorinformation is 1.5 mc. However, some re-ceivers do not take advantage of all the higherfrequency color information, therefore theamplifier bandwidth may be some what lessthan 1.5 mc.

If a defect develops in this stage that preventsthe color signal from getting through, you'llget a black and white picture, but no color.

Burst AmplifierThe burst amplifier does just what the nameimplies --it amplifies the color burst on therear pedestal of the horizontal sync pulse.This stage is biased beyond cut-off. A pulsefrom the horizontal sweep keys or turns thestage on by overcoming the bias. The colorburst arrives at the stage when the bias isovercome so it is amplified by the stage.

If the burst amplifier fails to amplify thecolor burst, the set will give you a black andwhite picture, but no color. Also, if the hori-zontal oscillator in the TV set is incorrectlyadjusted, the pulse used to key on the burstamplifier will not arrive at the stage at thesame time as the color burst; the burst willnot be amplified and again you'll be unableto get any color.

Defects in both the color amplifier and burstamplifier stages are easily isolated using acolor bar generator and an oscilloscope.

The 3.138 mc OscillatorThe 3.58 me oscillator is a crystal oscillator.A crystal is used to keep the oscillator fre-quency as close as possible to exactly thesame value as the original 3.58 mc color sub -carrier. The color subcarrier is needed forinsertion into a color detector stage. You'llremember that the color subcarrier itselfis not transmitted --only the color sidebands.To detect the color information, we must re-insert the subcarrier.

If the 3.58 mc oscillator fails to oscillate,you'll be able to get a black and white pictureon the TV receiver, but no color. You caneasily check to see if the oscillator is op-erating with an oscilloscope.

Phase DetectorThis stage compares the frequency and phaseof the color burst signal and the crystal oscil-lator. If the frequencies and phases are iden-tical the output from the stage will be zero.If the frequency or phase of the oscillatorsignal differs from those of the color burst,the phase detector will develop a signal thatis used to correct the oscillator frequencyand/or phase.

Reactance StageThe reactance or crystal control stage isused to keep the crystal oscillator operatingat the correct frequency and phase. The tubevaries the reactance in the oscillator stageand thus can make small corrections for anyslight error in frequency and phase of thecrystal oscillator. The signal which controlsthis stage comes from the phase detector.

A defect in either the phase detector or re-actance stages will permit the crystal oscil-lator to drift from the exact required fre-quency. This will cause the colors in thepicture to drift from one color to another.We call this loss of color sync. In somecases the drift is slow, while in others itoccurs quite rapidly. Defects in these stagescan usually be located with an oscilloscopeand a vtvm.

Color DemodulatorThere are two color demodulators in colorreceivers using the tri-color tube. Two colorsignals 90° out of phase are transmitted onthe color sub -carrier. These two signals arerecovered by means of the two color de-modulators. In one demodulator the colorsignal is mixed with a signal taken directlyfrom the 3,58 me crystal oscillator and inthe other demodulator the color signal is

7

mixed with a signal from the oscillator whichhas been shifted 90°.

If neither color demodulator is working you'llget a black and white picture, but no color.If only one is working, you'll get some colorin the picture, but not all the colors. If theflesh tones (red -orange) are missing, the de-modulator which takes the signal directlyfrom the crystal oscillator is at fault, whereasif the blues are missing the other detector isat fault. The detector can easily be checkedwith an oscilloscope.

MatrixThe color information is primarily trans-mitted in the color signal. When the infor-mation from the color demodulators is mixedin the correct proportions with the black andwhite signal (usually called the Y signal),three separate color signals can be produced.This mixing is accomplished in the Matrix,which consists of a number of resistancenetworks. A defect in a matrix will resultin some loss of one color. Such defects arequite rare and can usually be found with anohmmeter. However, sometimes it is quickerto use a color bar generator and an oscillo-scope to first isolate the defect to a smallpart of the matrix.

I, Q, X, Z, (R -V), G -V) Amplifiers ....The -se are all names given to amplifiers usedto amplify the color signals between the colordemodulators and the picture tube. Whenused with the correct matrix they producethe required color signals to drive the colorguns in the picture tube. They are almostidentical to wide -band audio amplifiers andshould present no servicing problem. A defectin one amplifier will affect the color gundriven by that amplifier.

The Tri-Color TubeThe tri-color picture tubes in current useare three gun tubes. Color phosphors arearranged in triangles of red, green, and bluedots. A plate (called a shadow mask) withone hole in it for each triangle of three colorsis placed near the screen. Three separateguns, one for each color, are arranged in atriangle in the neck of the tube. The electronbeams from the three guns pass through theholes in the shadow mask at slightly differentangles. The phosphor dots are arranged sothey will be struck by the electrons from onlyone gun. Thus the electrons from one gunstrike the red phosphor dots, the electronsfrom another gun the green phosphor dots,and the electron from the third gun the bluephosphor dots.

When you set up a tri-color tube you make allthe adjustments made on a black and white

tube such as height, width, linearity, po-sitioning, etc. In addition you have an adjust-ment called purity. This simply assures thatthe electrons from the red gun strike onlythe red phosphor dots, the green gun thegreen dots, and the blue gun the blue dots.Purity adjustments are usually not too diffi-cult to make correctly.

There are far more difficult and time-con-suming adjustments. These are the conver-gence adjustments. The purpose of these ad-justments is to converge the three beams sothat at any given instant they are going throughthe same hole in the shadow mask. Incorrectconvergence adjustments will result in oneor more colors being displaced so that partsof the picture will be fringed in the displacedcolor. TV set manufacturers give completeinformation on these adjustments, how tomake them, and the order in which they mustbe.made. It is almost a hopeless task to tryto converge the beams in a color tube withoutthese instructions.

This article is not intended to teach you colorTV servicing, but only to arouse your interestin, color and to show you that many of thedefects you will run int., will be the samedefects you'll find in monochrome receivers.Defects in the color circuits are usually nottoo difficult to find. A color TV is more dif-ficult to service than a monochrome receiveronly because it's bigger and has more partsin it -- the circuits in the set are not muchdifferent from those found in black and whiteTV.

SAC TV SERVICE

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8

DEVICE OF THE MONTH

FIXED CAPACITORS

R. C. APPERSON, JR.

capacitors....simple subject, isn't it?Two metallic layers separated by a dielec-

tric, used in circuits as bypasses and couplingdevices; found as filters and in de -couplingnetworks, and used to tune resonant circuits.

Right. These are the jobs taken care of bycapacitors, but do you know which type ofcapacitor to use in each instance? This is apoint that a lot of technicians overlook. Ifa bypass of .005 mf is needed, a .005 p.f capa-citor of adequate working voltage is soughtand placed in the circuit. In some cases, itmakes no difference, but in other casesdamage is done.

We will attempt to point out the various typesof fixed capacitors and how they should beused. By proper use, time on the bench issaved. This is the mark of a good technician.

The most familiar types of fixed capacitorsare electrolytic, ceramic, mica, and paper.These are categorized by the dielectric ma-terial used, each having certain characteris-tics applicable to special circuit considera-tions. After examination of each type, we'llthen touch on the newer capacitors madeavailable since the advent of the transistorand microminiaturization.

Let's examine the electrolytic capacitor first.It will be recognized schematically as this

-Tand will always have one side designated asthe positive and one as the negative lead. Itis polarized and this dictates the applicationsin which it may be used. The dielectric isthe product of an electro-chemical processand forms between the plates of the capacitorwhen a voltage is applied. This voltage isknown as the forming voltage.

A word to the wise here could save grieflater. Never connect a shelf -stored electro-lytic into a circuit and apply full voltage. Ifthe capacitor has been sitting for any lengthof time, the dielectric will have "gone back"into the metal and the capacitor appears as ashort circuit-no better than the one which itreplaced: Always apply a gradually increas-ing, forming voltage from a variable powersupply to an electrolytic that has been stored.Although new from the wholesaler, it may havebeen on his shelf for some time. Don't takethe chance.

HAS LARGE CAPACITY

We all know one very important applicationof the electrolytic. It is the filtering devicein most power supplies. The reason it is sopopular is that a large capacity can be ob-tained in a relatively small package. If alow working voltage rating is required, thepackage for a large capacity, say 100 if, willbe not much bigger than a paper capdcitor of1 µf at 400 WVDC.

Therefore, we find electrolytic capacitorsbypassing cathode resistors in vacuum tubeamplifiers when low frequency response is acriteria. Here, again, we must note that thepositive side of the capacitor connects to theside of the resistor which is tied to the cathodeof the tube. Since current flows and voltageis dropped, the cathode will be positive withrespect to ground.

USE AS SCREEN BYPASS

Electrolytes are also used as screen by-passes in certain wide band applications, sodon't think that an error has been madewhen you find one in, say, a vertical ampli-fier of an oscilloscope. Again low frequencyresponse is the deciding factor.

AC circuits are one place that electrolyticsshould never be used - as was stated earlier,they are polarized and cannot stand reversevoltage. A trick to keep in mind, though, for

9

certain applications such as low frequencytuned circuits is a back-to-back arrangement,like this

+

which allows you to get big capacity, non -polarized. This should only be used in signaltype circuitry, not where large voltages arepresent.

One important point to keep in mind when con-sidering the mica capacitor for use in cir-cuitry is its inherent low inductance. Thismakes mica one of the choices for interstagecoupling in high frequency applications. Thistype of capacitor is also used to bypassscreen grids. It may be used to tune resonantcircuits, and is used in interference filtersfor both radio and television frequency inter-ference (RFI and TVI). It is a good policy, inrepair work, to replace a mica with anothermica. The engineer probably had a reasonfor his selection.

Ceramic capacitors, both disc and tubular,also have low inductance characteristics, soceramic and mica are used interchangeablyin many places. High breakdown voltageratings are available with ceramic capaci-tors, so consider this when replacing one. Itis smarter to replace a mica with a ceramicthan vice versa, unless peak circuit voltagesare known.

Small packages with reasonably high workingvoltage ratings and capacities up to 1. µf areavailable in ceramic for transistor applica-tions. one drawback is the tolerance allowedon most of these. They are +80/-20 per cent,and if used in a circuit such as an oscillatoror one using feedback, the operation of thecircuit can be hampered. Pulse circuits,where high frequencies are involved, are onedefinite problem area when capacitor re-placement (using one of these ceramics) isinvolved.

Trial and error is the best bet here. Don't bealarmed if you suspect a capacitor is bad andthe replacement doesn't do what you think itshould. Remember +80/-20 per cent is a 100per cent capacity spread, so the stampedvalue need not be near what the actual capa-city is.

Paper capacitors are found extensively whereprice is a deciding factor. There are good

paper capacitors and some that are cheaperand not so good. Low frequency applications,where a larger capacitor is needed, presspapers into service. If there is a malfunctionin a circuit where one is used, experiencehas taught me to check the capacitor forpossible leakage, especially on equipmentthat is a few years old. One oscilloscope,five years old, required changing every paperin it-since then, I suspect them:

As we said before, good paper capacitorsare available and should be used wheneverreplacing a defective paper capacitor. Theyare molded plastic and do not spew wax andoil all over everything if they do malfunction.The few pennies 'difference in price will payoff with longer and more dependable service.

Paper capacitors serve more purposes incommon circuitry than any of the other types.They are used for coupling, decoupling, by-passing, and tuning low frequency circuits.Most buffer capacitors in vibrator supplyautomobile radios use paper.

A tubular paper capacitor has a marking onthe case like this

and is marked in most instances "outsidefoil." This lead should be connected to theside of the circuit which is nearest groundpotential. The capacitor is not polarized andcannot be damaged by ignoring this rule, butelectrostatic and electromagnetic couplingwill be minimized, saving much hum head-ache.

STABILITY'S A MUST

There are certain times when stability is amust and expense is entirely secondary. Inthese cases there are capacitors available,at a higher cost, that' provide very goodtemperature stability. The glass dielectriccapacitor is one and will be found in preci-sion circuitry or military gear which hasvery stringent specifications to work by.They are close tolerance capacitors. Take aclose look at the circuit and its function be-fore replacing a glass with anything except aglass. The equipment in which they are usedis expensive, so cost of the capacitor forreplacement should not sway your decision.

Now for the very special type of temperaturestabilized capacitor which will be found inmost communications equipment with con -

10

trolled frequency. It is the NPO capacitor.

This type has an absolute zero temperaturecoefficient, and capacity stays constant overan extreme range of temperature. This isachieved by using two different types of di-electric, one having a negative coefficient,and one with a positive coefficient. The co-efficients are equal in magnitude but oppositein sign, so that the sum coefficient is zero atall times. From this we derive the NPO(negative -positive -zero). If frequency drift isthe problem, check first to see if NPO capa-citors are used in the frequency affectingcircuits. If not, use them. If they are, this isa sign that one of them has gone bad andneeds another NPO in its place.

Another capacitor that is being used exten-sively today, especially in transistor applica-tions, is the Tantalum type. By electro-chemical means, a thin Tantalum oxide filmis formed which has a higher dielectricconstant, than any other material known today.

The Tantalum capacitor gives large capacityin a small space. This is essential in tran-sistor applications. Since the resistive valuesare small in the circuits, capacity must behigh to obtain proper rc constants. Then,with transistor applications being inherentlycompact, we need big capacity in a small area.

One thing to note is that these capacitors areusually polarized, as are electrolytics, andcannot stand back -voltage. In fact, they shouldhave a dc component that exceeds the ac

MS AMPMICAMIXER

signal component at all times to avoid back -voltage. If you get one in backwards, it willlet you know it because IT WILL BLOW UP.

The capacitors are available innon-polarizedconfigurations also and can be spotted by

crimps on either end of their metal case. Thepolarized ones will have only one crimp andwill be marked clearly with a + sign.

Since the discussion has been along applica-tion lines and we have talked about manydifferent types of capacitors, I have taken aschematic of a unit in which most of thecapacitors discussed are used and noted onthe diagram which type of capacitor shouldbe used in each application.

After looking it over, take a piece of equip-ment, be it TV or radio or even a test appa-ratus, and look at the actual components.Now take its schematic and figure why theengineer selected the capacitor he did to dohis Job.

We didn't cover all of the whys and where-fores of capacitors, but I do hope I havealerted you to the fact that there oan be adifference in a .05 if 500 WVDC capacitor,be it disc, ceramic, and/or inexpensive paper.

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11

The CONAR 280 Signal Generator

Precise Pre -Calibration Makes ThisOutstanding As A Kit Instrument

BY J. B. STRAUGHN

The handsome CONAR 280 Signal Generatoris shown in Fig. 1. It is a fitting companion

for the CONAR 230 Signal Tracer, and theseinstruments can be used separately or sup-plement each other.

The Model 280 is available in kit form or ata slight increase in cost can be obtainedbuiltand tested by the CONAR assembly section.Most service men hesitate to purchase asignal generator in kit form because eitherthe signal generator has no means of beingaligned for proper calibration or they do nothave the frequency standards required forprecision alignment.

Neither of these factors applies to the CONAR280. The rf coils (except the highest band)have adjustable slugs and each coil is

FIG. 1. The Conar Model 280 Signal Generator.

equipped with a trimmer. The coils and trim-mers in each kit are adjustedprecisely in theCONAR laboratories, using special jigs. Be-cause the leads for all coils and trimmers areshort and direct the distributed capacities donot vary from instrument to instrument andwhen assembled the accuracy is excellent,being in the neighborhood of 2%. This is betterthan the accuracy of many service type signalgenerators and is quite satisfactory for all

types of service applications. The accuracycan be improved to about 1% by adjustingagainst known station signals, picked up on acommunications receiver or with specialstandards, as is done in CONAR assembledinstruments. The 280 manual contains fullinstructions for those who wish to check orrecalibrate their Signal Generator. However,the improvement is a minor matter and, be-cause calibration is excellent to start with,does not materially increase the worth of theinstrument as a service tool.

Before going into the uses of the Model 280,let's take a quick look at its operation. Asimplified circuit is in Fig. 2. Only a singlerf coil is shown and the rf band switch hasbeen omitted. This switch changes the con-nections to the coils and, on the last twobands, switches out variable tuning capacitorC2 and substitutes a smaller variable capaci-tor.

The Model 280 consists of a variable rf os-cillator built around tube Vi and a fixed 400cycle sine wave oscillator built around theright-hand section of V2 (pins 6, 7, and 8).All output signals are fed to the left-handsection of V2 and are taken from its cathode.The power supply is the conventional half -wave type using a selenium rectifier.

Tube V1 operates as a standard Hartley os-cillator. The screen grid (pin 6) acts as thevirtual plate and is kept at rf ground potentialby capacitor C14. When tube V1 heats up, thecathode current flows from B- through the tapon the tuning coil and, in doing so, shock -excites the resonant circuit consisting of Ll,Cl and C2, The resulting signal is appliedthrough C3 to oscillator grid pin 1. A furtherchange in cathode current, at the frequencyof the resonant circuit, takes place and os-cillation is maintained. Oscillator bias is de-veloped across Rl.

The plate current flows through the mixergrid (pin 7), the screen grid, andto the plate.

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FIG 2 Simplified diagram of the CONAR Model 280 circuit.An rf signal is developed across plate loadR2 and is fed through C4 to the grid (pin 2)of cathode follower V2.The rf signal is developed across R10, whichserves as the Fine Attenuator Control. Byadjusting R10, any amount of the availablesignal across R10 is fed through C10 andC11 to the output cable and arrives at the hotand ground clips for any use desired. Thisis a pure unmodulated rf signal.The 400 cycle signal is produced in theColpitts oscillator circuit consisting of theright-hand triode of V2, choke L2, capaci-tors C6, C7, C9 resistors R7, R9, and R8.C8 and R5 are used to couple the audio signalfrom the oscillator circuit. In the positionshown for SW2, R5 is grounded and there isno audio output.

In the af position, the upper section of SW2removes plate and screen voltage from V1,killing the rf oscillator. The lower sectionconnects R5 to the grid of the cathode followerand the audio signal appears at the output ofthe cable.When SW2 is in the MOD rf (modulated) po-sition R5 feeds the 400 cycle signal to pin 7,the mixer grid of Vl. The rf and 400 cyclesignals are mixed in the tube and the modu-lated rf signal is fed through C4 to the cathodefollower.This explains everything about the operationof the Model 280 except switch SW1. This is

1 IGROUND

CLIP

the coarse attenuator switch, and when closedconnects a 47 -ohm resistor from the junctionof C10 and C11 to the chassis. This actioncauses a great reduction in the signal at theoutput of the cable. The signal is still con-trollable by adjusting R10. Note particularlythe presence of C11 in the circuit. This isa high voltage capacitor and makes is pos-sible to connect the hot probe to the plate ofa tube in a receiver without danger ofdamaging the set or signal generator.

CONTROLSYou are already familiar with the FunctionControl which enables you to obtain unmodu-lated rf, modulated rf and af signals, andwith the Fine and Coarse attenuator controlswhich govern the signal level at the outputof the cable. The On -Off switch is gangedwith the Fine Attenuator Control. The tuningcontrol moves the pointer across the dial andadjusts the frequency of the signal generatorover the band in use.The band switch selects one of six sets ofcoils and trimmers, thus permitting a widerange of available frequencies. The bandscover the following frequencies:

Band ABand BBand CBand DBand EBand F

170 kc - 550 kc550 kc - 1600 kc (1.6 mc)1.6 mc - 5 mc4.5 mc - 15 mc15 mc - 30 mc30 mc - 60 mc

13

USES OF THE 280SIGNAL GENERATOR

The most important questions to the pros-pective owner of a Signal Generator are"What do you use it for, and how do you hookit up to the receiver?"

The Signal Generator produces a signal whichcan be used to align the rf circuits in a re-ceiver to their correct frequency. It can alsobe used to inject signals into the receiver atvarious points to verify the operation or non -operation of the receiver stages between thepoint of signal injection and the output of thereceiver. In other words, in addition to re-ceiver alignment it is usedto localize troubleto a section and to a stage of a receiver.

The presence of output blocking capacitorC11 in Fig. 1 means that even if you make amistake in connecting the signal generatoryou will harm neither it or the receiver.

Just how to connect the Signal Generator toa set depends on the injection point you havechosen. The manual for the Model 280 con-tains detailed instructions for alignment pro-cedures, so we will only touchon them brieflyhere.

When aligning a receiver you need somethingother than your ears to check changes in out-put level which, on an AM set, should in-crease as the receiver comes into alignment.A VTVM is generally used as an output indi-cator although, if the set is an old oneequipped with a tuning eye, you can make the

FIG. 3. The CONAR Model 211 VTVM.

adjustments for maximum closure of the eye.The output indicator may be a VTVM suchas the NRI Model 2W or the later CONAR 211(See Fig. 3). This may be used as a dc volt-meter and connected across the diode loadresistor to measure AVC voltage (see Fig.4),

FIG. 4. Here the DC VTVM is connectedacross the volume control to observe theeffect of the RF signal level at the de-

tector output.

or as an AC voltmeter it may be connectedfrom the plate of an output tube to ground orin push-pull transistorized outputs across theprimary connections of the output trans-former, as shown in Figs. 5 and 6. A lessdesirable connection, because less signal isavailable, is across the voice coil of the loud-speaker. When using the AC meter for outputmeasurements a modulated signal is alwaysrequired because you are observing the de-modulated signal in the audio section of thereceiver.

A typical schematic diagram of an AC -DCbroadcast receiver is shown in Fig. 7 and wewill use it In our discussion of alignment andtrouble shooting.

In this set we have two 1-f transformers,T1 and T2, tuned by trimmers C5, C6, C8,and C9. Also, we have trimmers in parallelwith the oscillator and rf tuning capacitorsmarked Cl and C2. These trimmers are notshown in the schematic. The first step is toalign the i-f amplifier at its assigned fre-quency of 455 kc.

This calls for a decision whether to use amodulated or unmodulated signal. If the re-ceiver is not extremely weak you can use anunmodulated signal. As a result, no soundwill be produced by the receiver loudspeakerduring alignment. This is appreciated bynearby workers. In such a case the outputmeter connection shown in Fig. 4 must beused. If the set is quite weak a modulatedsignal and full gain of the receiver of ampli-

14

FIG. 5. The VTVM as an AC voltmeter maybe connected from either plate to chassis.The sound from the loudspeaker can be

kept fairly low with the attenuators.

Fier may be required to give a discernibleoutput. In this case, use the connections inFig. 5. The sound from the loudspeaker canbe kept fairly low with the Signal Generatorattenuators, as a very large signal shouldexist at the primary of the output trans-former even without excessive volume.

How to connect the Signal Generator to thereceiver is somewhat a matter of preference

FIG. 6. The VTVM set for AC measurementsmay be connected to the collector leads ofoutput transistors, or you can get by with asmaller signal from either collector lead to

chassis.

and is also governed by the condition of theset. The object, of course, is to inject a 455kc signal into the circuits to be aligned. Inthe case where the set is almost dead it mightbe best to clip the hot leadto pin 1 of tube V2and clip the ground lead on B-. Tune theSignal Generator to 455 kc, found on Band A,and set the attenuators to give a reasonableoutput.

Stop the local oscillator by holding your

finger on the rotor and stator of the oscil-lator tuning capacitor. This prevents un-desired beat signals between the local oscil-lator and Signal Generator from being pro-duced. The practice of killing the oscillatorby slipping a small screwdriver blade of theset screw type between the plates is to becondemned because of the danger of bendingthe plates. A clip lead across the oscillatortuning capacitor is OK, but your finger willwork fine. Now adjust G8 and C9 in any orderfor maximum output. Cut back on the SignalGenerator attenuator settings as the outputlevel increases.

You can now connect the Signal Generator tothe receiver antenra and ground leads and,while still holding your finger on the localoscillator rotor and stator plates, adjust C5and C6 for maximum output. Now go backover all four trimmers again (any order) tosee if any improvement can be obtained. Ifyou cannot get sufficient signal, tune the re-ceiver to the low end of its dial and then theloop and its tuning capacitor, Cl, will offerless rejection to the i-f signal from the gen-erator. This completes the i-f alignment.

The case just described is extreme, wherethe trimmers had been badly misadjusted.Where volume is adequate you can make youroriginal connection to the antenna and groundleads and adjust all four trimmers (any order)for maximum output. Again kill the localoscillator.

KILLS THE OSCILLATOR

Another method is to clip the Signal Generatorhot lead to the stator of the local oscillatorand the ground clip to the oscillator frame.This kills the local oscillator and also injectsthe signal (455 kc) into the circuit - againadjust all four trimmers.

The remaining adjustments are the oscillatorand rf trimmers. Tune the receiver to thehighest frequency shown on its dial and setthe Signal Generator to produce the samefrequency. Attach the Signal Generator leadsto the antenna and ground terminals. Adjustthe receiver oscillator trimmer to bring inthe signal and then adjust the receiver rftrimmer for maximum output. This completesthe alignment.

In some sets, particularly those using a loop -stick type of antenna, no ground and aerialconnections are provided. A simple methodof signal injection is to clip the hot and groundleads of the signal generator together. Theresulting short causes a large rf current toflow in the cable and ground lead. The loopso formed can be placed over one end of the

15

loopstick antenna. See Fig. 8.

This injection system can be used for i-f, rf,and oscillator adjustments.

ROCKING PROCEDURE

In many transistor sets an extra oscillatoradjustment is provided for better trackingbetween the oscillator and rf sections. Theadjustment is generally a variable slug in theoscillator coil, whereas in some very oldtube receivers this adjustment was a variablepadder (trimmer in series withthe oscillatortuning capacitor and the oscillator coil). Inboth cases the adjustment procedures areidentical.

The rf and oscillator trimmers are adjustedat the high frequency end of the broadcastband as previously described. The rf trimmeris not to be touched after this adjustment.

Next tune the receiver and Signal Generatorto approximately 600 kc. Tune the receiverslowly back and forth across the 600 kc sig-nal, taking care not to move the receiverdial far enough to lose the signal. While doingthis, turn the oscillator slug or padder firstin and then out. Stop tuning (rocking) the re-ceiver and varying the receiver oscillatoradjustment at the point of greatest output.Return the receiver and signal generatorsettings to the high end of the dial and re-adjust only the oscillator trimmer for maxi-mum output at the correct dial setting. Re-peat the low frequency procedure. Go back

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and forth from the low to the high ends ofthe receiver dial until no further improvementis noted. This will give perfect tracking andmaximum receiver sensitivity. Disregard anyslight inaccuracy in low frequency receiverdial readings.

Space does not permit the detailed discussionof all different ways in which the Model 280Signal Generator might be used in servicing.The general technique to use is outlined inthe following section. For additional informa-tion, refer to your NRI Lessons.

Let us take common receiver troubles andsee how the Signal Generator might be usedto find the trouble in the set.

Set Dead: When the set is dead, the SignalGenerator is used to isolate the trouble to aspecific stage. First, set up the Signal Gen-erator so that an audio signal is obtained atthe end of the test probes. Do this by turningthe FUNCTION switch to the "AUDIO" posi-tion and use the FINE ATTENUATOR andCOARSE ATTENUATOR controls to vary theoutput intensity. Turn on the receiver.

This audio signal is fed to the grid of theoutput tube. If a pentode or beam power out-put tube is used (this is most common inmodern receivers), you should be able tohear a signal from the loudspeaker with theSignal Generator controls set for maximumaudio output. If you can hear a signal whenyou place the "hot" probe of the Signal Gen-erator on the grid of the output tube and the"ground" lead to the set chassis, then transfer

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FIG. 7. Schematic diagram of a typical AC -DC radio receiver.

J

16

FIG. 8. Technician Jim Johrson of NRI'sQuality Control calibrates an assembled 280Signal Generator by beating its signals against

a special crystal -controlled standard.

the "hot" lead of the Signal Generator backto the grid of the first audio amplifier tube.

If you again hear the signal here, switch theSignal Generator to "modulated rf" outputand adjust the frequency of the Signal Gen-erator to the i-f frequency of the set. Touchthe "hot" probe of the Signal Generator to thegrid of the i-f amplifier tube. You should againbe able to hear a signal from the loudspeaker.

Continue this test stage by stage until youcome to the antenna end of the set. Thenswitch the Signal Generator from the i-f fre-quency of the receiver to a modulated rf sig-nal within the broadcast band and try pickingit up on the receiver.

INDICATES TROUBLE

wnen you mat note that the signal fails tocome through the receiver, it indicatestrouble in that stage. For example, if youcannot get a signal from the loudspeaker whenfeeding the audio signal to the grid of the out-put tube, it indicates trouble either in theoutput stage, in the power supply, or in theloudspeaker itself. Check each item in turn.You can check each item in turn. You cancheck the power supply by checking for plateand screen grid voltages.

In making tests past the first audio amplifiertube and towards the antenna end, the volumecontrol of the set should be in its maximumposition. You can check the operation of thevolume control by simply connecting the audiosignal directly across the volume control andvarying the position of the center arm to seeif a variation in output intensity is obtained.

If you find that any particular stage is defec-tive, you should check operating voltages and

FIG. 9. Helen Gillespie of Assembly pre -adjuststhe trimmers to be used in a CONAR 280Signal Generator kit. Proper adjustment pro-duces a circular pattern on the scope screen

test the parts in that stage until you locatethe defective part.

If you were able to get a signal from everystage on through to the antenna, but the setis still dead, there is a good chance that thelocal oscillator is not working. The con-ventional test is to check for dc voltageacross the oscillator grid resistor. In someoscillator -mixer circuits, however, no oscil-lator grid resistor is present. Feedback maybe obtained through plate and cathode circuitsor between screen grid and cathode circuits.In a case like this, a check on the local os-cillator operation can be obtained by attachingthe antenna to the receiver and turning thedial of the receiver to a frequency of a localbroadcast station. If the set is dead, nothingwill be heard from the loudspeaker.

Then, tune the Signal Generator to a frequencyequal to the frequency of the broadcast sta-tion plus the i-f of the set. The FUNCTIONswitch will be set to the "rf unmod." positionand this unmodulated rf signal will be fed tothe grid of the converter tube. If you canhear the broadcast station coming throughnow, you can be pretty sure that the localoscillator is not working.

You have actually substituted the oscillatorof the Signal Generator for the local oscil-lator in the receiver.*

Weak Receiver: An approximate indication ofstage gain can be obtained if the Signal Gen-erator attenuator settings are left at a fixed

* If you have an NRI or CONAR VTVM youcan set it for AC and measure the oscillatorvoltage directly across the oscillator tuningcapacitor. This is frequently done in transis-tor sets.

17

position and the output level noted as the"hot" probe is transferred from amplifierstage to amplifier stage. As you pass eachamplifier stage (working toward the antenna),the level of the output signal should increase -if it does not, signal strength is lost ratherthan gained in the particular stage. (Thistest does not apply to measurement of con-version gain.)

When making gain tests ahead of the seconddetector you should check avc voltage since,where avc is used, the gain of the receiverwill tend to change as the avc voltage changes.Maximum avc voltage indicates maximumsignal strength, although the audible signaloutput may not change appreciably.

FIG. 10. Closeup showing how hot and groundleads of the 280 are clipped together andslipped over a loopstick in a transistor set.

Modulation Hum: A Signal Generator is quiteuseful for checking "modulation hum" in aset. You can recognize modulation hum by thefact that you hear a hum when tuned to a sta-tion but do not hear it when tuned off the sta-tion. To locate where modulation hum isintroduced in the set, proceed as follows:

All tubes should be checked for heater -to -cathode leakage and grid circuits should bechecked for opens. Either heater -to -cathodeleakage or an open grid circuit might wellcause hum modulation.

Then, pick up a station on which you getmodulation hum, Measure the avc voltage de-veloped. As you check from stage to stage inthe following steps, adjust the Signal Gen-erator output with the FINE ATTENUATORand COARSE ATTENUATOR controls untilat least the same avc voltage is measured.This will insure that the test signal hassufficient amplitude to cause modulation hum.

Feed an unmodulated rf signal into the re-ceiver, starting at the last 1-f stage and work-ing toward the antenna end. Use an =modu-lated signal which will feed through the set.For example, when checking the i-f stages,

you should use the i-f of the receiver. Thereceiver, at this time, is tuned so that nostation is being picked up.

The stage at which you first notice the humcoming through is the stage that is defectiveand this is where modulation hum is beingintroduced. You should go over all solderedconnections and check parts in that stageuntil you locate the defective part or con-nection.

Intermittents: The best way to use the SignalGenerator on an intermittent receiver is tomake a permanent connection and wait forthe intermittent to occur. (It is difficult tofeed from one stage to another while theintermittent is in progress, as the surge dueto connection might clear up the defect.) Wewill assume that the intermittent conditionis one in which the set will stop playing forawhile - start, play for awhile and stop again.

To use the Signal Generator in servicing anintermittent set, feed a modulated rf signalthrough the receiver from the antenna, andconnect a de voltmeter to read ave voltage.Turn up the set volume control until the audionote can just be heard in the speaker,

Leave the set and Signal Generator on untilthe intermittent condition occurs. When theset goes dead, immediately check for avevoltage at the meter. If the avc voltage hasnot changed in value, the trouble is in theaudio stages. If there is no avc voltagepresent, or if the ave voltage has changed,the trouble is in the rf or i-f stages. Youhave thus effectively isolated the trouble toone section of the receiver. Concentrate onthe defective section. Inject the test signalat various points and again wait for the inter-mittent to occur. In this way the intermittentstage can usually be isolated. Suddenly in-creasing the output of the Signal Generatorwill frequently cause the intermittent to showup and may save much time.

You should precede any tests of this sort withthe conventional "brute force " test. To use thebrute force test, a pair of longnose pliers isused to wiggle each part and connection in theset until you find the particular part whichwill cause the intermittent condition to oc-cur. That part is defective and should be re-placed. If the defect is due to a loose con-nection, the connection should be resoldered.

All in all a Signal Generator is an extremelyvaluable service tool and is one of the firstto be purchased by the newcomer to theservice field.

18

EMPLOYMENT OPPORTUNITIESMajor contracts ($1 million or more) were recently awarded by govern-ment agencies or major contractors to the Electronics firms listed here.Such large orders frequently require the hiring of additional personnel.Those interested in possible employment should contact the companies.

Collins Radio Co., Dallas, Texas.General Dynamics/Convair, San Diego, Calif.Stelma, Inc., Stamford, Conn.Beckman Instruments, Inc., Fullerton, Calif.Sylvania Electric Products, Inc., Mountain

View, Calif.Emerson Electric Co., St. Louis, Mo.Honeywell, Inc., Hopkins, Minn.IBM Corp., Rockville, Md.Fairchild Stratos Corp., Hagerstown, Md.International Telephone and Telegraph Corp.,

Fort Wayne, Ind.General Precision, Inc., Glendale, Calif.Ling-Temco-Vought, Inc., Dallas, Texas.American Bosch Arma Corp., Long

Island, N. Y.North American Aviation, Inc., Automation

Div., Anaheim, Calif.General Dynamics Corp., Pomona, Calif.Univac Div., Sperry Rand Corp., St. Paul,

Minn.RCA Services Co., Camden, N. J.Atlantic Research Corp., Duarte, Calif.Martin Marietta Co., Denver, Colo.Varo, Inc., Garland, Texas.Sperry Gyroscope Co., Great Neck, N. Y.FMC Corp., Minneapolis, Minn.General Motors, AC Spark Plug Div.,

Milwaukee, Wis.Bell Aerospace Corp., Wheatfield,N.Y.Kollsman Instrument Corp., Elmhurst, N. Y.Nortronics Div., Northrop Corp., Palos

Verdes, Calif.Bell Aero Systems Co., Buffalo, N. Y.Maxson Electronics Corp., Scranton, Pa.ITT Federal Laboratories, Nutley, N. J.Fairchild Space and Defense Systems,

Syosset, N. Y.Sperry Rand Corp., Washington, D. C.General Electric Co., Schenectady, N. Y.Collins Radio Co., Richardson, Texas.Westinghouse Electric Corp., Pittsburgh, Pa.Aerospace Corp., El Segundo, Calif.Interstate Electronics Corp., Anaheim, Calif.Collins Radio Co., Cedar Rapids, Iowa.General Atronics Corp., Philadelphia, Pa.Geotechnical Corp., Garland, Texas.Defense Electronics, Inc., Rockville, Md.General Electric Co., Philadelphia, Pa.Model Engineering and Mfg. Corp.,

Huntington, Ind.Texas Instruments, Inc., Dallas, Texas.Hughes Aircraft Co., Los Angeles, Calif.Philco Corp., Palo Alto, Calif.

McDonnell Aircraft Corp., St. Louis, Mo.Bendix Corp., Teterboro, N. J.Scientific Data Systems, Inc., Santa Monica,

Calif.General Precision, Inc. Aerospace Group,

Pleasantville, N. Y.Bendix Corp., Radio Div., Baltimore, Md.Electronics Associates, Inc., Long Branch,

N. J.Hughes Aircraft Co., Culver City, Calif.Raytheon Co., Norwood, Mass.Ladoie Laboratories, Morganville, N. J.Martin Company, Baltimore, Md.Bogue Electric Mfg. Co., Paterson, N. J.Carrier Corp., Syracuse, N. Y.Northrup Corpis Ventura Div., Newbury Park,

Calif.Sylvania Electric Products, Inc., Waltham,

Mass.General Precision, Inc., Binghampton, N. Y.Philco Corp., Philadelphia, Pa.Aero Geo Astro Corp., Alexandria, Va.Philco Corp., Aeronutronics Div., Newport

Beach, Calif.Energy Systems, Inc., Palo Alto, Calif.Electronic Communications, Inc., St.

Petersburg, Fla.Western Devices. Inc., Burbank, Calif.Ryan Aeronautical Co., San Diego, Calif.Sperry Rand, Salt Lake City, Utah.Brown Engineering Co., Huntsville, Ala.General Telephone and Electronics Corp.,

Williamsport, Pa.TRW -Technology Laboratories, Inc.,

Redondo Beach, Calif.Western Electric Co., New York, N. Y.Western Electric Co., Burlington, N. C.Cutler -Hammer, Inc., Deer Park, N. Y.Sperry Rand Corp., Great Neck, N. Y.Giannini Controls Corp., Durarte, Calif.Eitel-McCullough, Inc., San Carlos, Calif.Kellsman Instrument Corp., Syosset, N. Y.Sylvania Electric Products, Inc., Williams-

port, Pa.Radio Corporation of America, Moorestown,

N. J.Reynolds Metals Co., Richmond, Va.Lundy Electronic and Systems, Inc., Glen

Head, N. Y.Burroughs Corp., Detroit, Mich.Radiation, Inc., Melbourne, Fla.Westinghouse Electric Corp., Baltimore, Md.General Precision, Inc., San Marcos, Calif.Raytheon Co., Bedford, Mass.

19

george finds a transistor checker can be a

LEAKAGE LIFESAVERBY JOHN POTTER SHIELDS

I t was just a bit after 5:30 on a snappierthan usual late October afternoon that

found George Bensen easing his little foreigncar into the garage after a day of instructingat the Gateway Electronic Institute.

"It's a good thing that I don't have any anti-freeze problem with the air-cooled engine inthis little buggy," George mused, as hestopped to note that the mercury in the ther-mometer mounted on the garage door wasslipping rapidly below the freezing mark.

"Hey, George, did you get a chance to stopoff at Electronic Emporium downtown?" hol-lered a familiar voice, as George turned tosee his quite -a -bit -younger red-headed cous-in come loping across the short back -yardthat separated their two houses.

George, who was the senior electronics in-structor at the tech school, held a number ofoperating licenses, both commercial andamateur. The combination made him a never-ending source of inspiration to his youngcousin, who had just obtained his NoviceLicense and who now worked, ate, and sleptHam radio.

"I sure did: This must be your day, as those50 -meter crystals that you had on order camein today. Come on into the lab and I'llseparate them from the bunch of goodieswhich I picked up."

Harry eagerly followed George into the lab,which consisted of a converted bedroomequipped with an impressive array of testgear, a complete SSB Ham station, and per-haps most important to Harry, a larger thanaverage junk box whose contents were asource of delight to him.

George set to unpacking the two cartons,while Harry perched himself on one of thenearby bench stools.

"Now, there's a gizmo I've never seen before.What are they?" queried Harry as he watchedGeorge checking a number of small socket -like items against the packing list.

"Transistor sockets, and you'll notice thatthey are of the 'universal' type which willaccept either the inline or triangular leadarrangement," George pointed out as hehanded one to Harry.

"Very nice, very nice, but why so many? Ididn't know that you had hoarding instincts."

"No," chuckled George, "I'm building up atransistor characteristic demonstrator formy course in semiconductors which will becoming up in about a month."

"Hmmm, sounds interesting-tell me more,"perked up Harry as he deserted the some-what uncomfortable bench stool in favor ofa nearby easy chair.

"Okay, you asked for it-and by the way,I'm pleased that you are showing some in-terest in semiconductors. Before you knowit, our Ham gear will be loaded with them.As you know, right now they're finding wideuse in DC to DC convertors in mobile rigsas well as modulation stages in low -powerrigs. Well, back to the project at hand,"continued George, as he picked up a scratchpad and pencil, "Here's the dope on this littleproject.

"What I'm building up are units that willdemonstrate relative gain and leakage ofvarious transistors. I'm going to mount theuniversal transistor sockets, toggle switch,potentiometer and terminal strips on thesepieces of pegboard, like so." George sketchedas he continued. "Now here's the schematicfor these little units. The collector contactof the transistor socket goes to one meterterminal; the other meter terminal to onebattery terminal and the other battery ter-minal to the emitter contact on the socket.The base contact on the socket goes to oneterminal of the SPST toggle switch; whilethe other switch terminal goes to the arm ofthe potentiometer, which in turn is con-nected across the battery terminal."

"One question," broke in Harry, who was nowwatching intently over George's shoulder,

20

"What kind of range meter are they going touse with these testers?"

"I plan to let the fellows use their multi -meters which they completed last month,"returned George.

"While the range will depend upon the parti-cular transistor, I would say that the 0-20or 0-50ma range will be used most often.

"Here's a unit that I made up as a model ofthe demonstrator. Would you like to see it inaction?"

Harry nodded as George reached across thebench for a small pile of transistors. "Firstof all, before inserting a particular transis-tor in the socket it is necessary to determinewhether it is a PNP or NPN unit," notedGeorge as he picked up a transistor from thepile.

"Let's see now, if I remember right, the PNPtransistor requires negative collector supplyvoltage, while the NPN requires a positivecollector supply."

"I see you actually did glance through thetransistor manual I loaned you," applaudedGeorge."By the way, an easy way to remem-ber the correct battery polarity is by themiddle letter. For example, in a PNP unit,the N can be figured as representing a nega-tive collector supply while just the reverseis a NPN unit.

"Well, let's see how she works," continuedGeorge, as he inserted the transistor in thesocket, connected a multimeter, switched tothe 0.25 ma scale to the meter terminal anda 6 -volt battery to the battery terminals."First, we'll check the transistor's leakageby leaving the toggle switch open. This, ofcourse, leaves the transistor's base circuitopen or floating."

don't see much action," commentedHarry. "The multirneter's pointer hasn'tedged up more than half a division or so."

"Yeah, that's a pretty good unit. Very lowleakage. Now let's get some idea of its gain."George flipped the toggle switch to the closedposition and slowly advanced the potentio-meter. As he did so, the multimeter indi-cated a sharp increase in collector current.

"Looks like you've got a live one there. Inotice that you've just barely turned thepotentiometer and the meter's reading fullscale."

"That's right," George answered. "You can

get a pretty good comparison of the gain ofvarious transistors of the same type by usinga unit you know is good as a reference. Simplyuse a calibrated scale around the potentio-meter and note the setting of the potentio-meter which produces, say, half -scale read-ing on the meter with the reference transis-tor, and note the meter reading.

"Isn't this gadget useful then as a simpletransistor checker?" queried Harry.

OSOROKS TRANSISTOR CHECKER

"That's right; in fact, almost all of the in-expensive transistor checkers on the marketuse the same principle."

"What's this I understand about the leakageof a transistor increasing as its ambienttemperature increases?" quizzed Harry.

"Here, I'll show you." George rummagedthrough a drawer until he came upon a par-ticular transistor. "Here's one that I've beenintending to return to the manufacturer. It'sa new unit, but its leakage is a shade higherthan the specs call for. I picked it for thislittle demonstration because its increasedinitial leakage current will make the meterreading a bit easier."

George inserted the transistor in the demon-strator's socket and applied operating volt-age.

"Notice that the leakage current is about 1mill. Now watch as I grasp the transistorbetween my fingers."

"I'll be darned," exclaimed Harry. "The oleneedle is really climbing up scale."

21

"It sure is," commented George. "This littledemonstration vividly illustrates a funda-mental property of transistors that must betaken into consideration when designing cir-cuits around them. Unless suitable pre-caution such as bias -stabilizing networksand sometimes temperature -compensatingresistors are employed-especially in poweroutput stages-a condition known as thermalrunaway can occur.

"That is, as the transistor's temperatureincreases, its leakage current will increase.This increased current flow through the tran-sistor will cause further heating, which inturn will cause more leakage currentto flow.The whole thing continues in a vicious circle,with the end result that the transistor can bedestroyed.

"It looks like all is not lost. I actually learnedsomething today," Harry grinned. "I'll haveto keep that in mind when I get around tosome actual transistor circuit designs-withyour help.

"Say, by the way George, I picked up a bunchof bargain transistors when I was downtownlast week. Could I borrow that little demon-strator to check them out this evening? Onesmall point, though, my multimeter is backat the factory getting some new bearings."

"Sure thing, Harry. Only one problem, I'mgoing over to troubleshoot an electronic tri-plate counter at the plant near the school to-night, and I'll have to take the multimeterwith me. I have an idea though. If you'll set-tle for a 'go, no go,' setup, I can fix you upso that a bell will ring if a particular tran-sistor that you're testing is excessively leaky.This will at least let you separate the wheatfrom the chaff."

"Ha, automation at last," chuckled Harry."Sure, that will be fine. I can at least tell theones that are too leaky to be on any value,and then later check out the others whose leak-age is low enough not to ring the bell."

George walked over to a small cabinet andpulled out a drawer marked Relays. Afterfumbling about for a few minutes, he pulleda small relay out of the drawer and placedit on the workbench.

"Here's just the ticket. It's a small sensitiverelay of the type used in model plane radiocontrol works, and designed to pull in at about2ma. We'll substitute it for the meter in thecollector circuit of the demonstrator, so thatit will pull in if one of the transistors whichyou are testing has more than around 2maleakage. All that remains is to connect this

small door bell and drycell in series acrossthe relay's normally open contacts so that thebell will ring when the relay closes."

Harry left the lab and trotted across the yardinto his own home and down to his den base-ment lab.

Rummaging through his considerably lesspretentious junkbox, Harry assembled a smallpile of transistors on his workbench and setup his "automation" transistor checker.

Somewhat later he had completed his task,the checker operating in great form. The tran-sistors were now neatly grouped in two piles;unfortunately the larger pile contained the bellringers due to excessive leakage. Somewhatreluctantly, Harry filed this pile in the trashcan.

It must have been around 3 a.m. that Harryawoke to the sound of a bell ringing someplace.At first, he couldn't quite make it out, but ashe became wide awake, he realized that it washis transistor checker in the basement. Hur-riedly, he grabbed a robe and rushed down-stairs to silence the gadget before it awokethe whole household.

As he neared the top of the basement stairs,he stopped as a touch of panic gripped him.Curls of smoke were coming from beneaththe cellar door and it was hot to the touch.Knowing that it is foolhardy to open the dooras the hot smoke and gasses behind it couldquickly suffocate him, he raced to waken hisfather, who immediately called the local firedepartment.

After the smoke and excitement had clearedit was found the damage had been confined toa small closet under the basement stairs. Ap-parently the fire had been started by the spon-taneous combustion of some linseed oil soakedrags which Harry's father had been using inpainting and had tossed in the small closet.Harry was considerably relieved to find thathis section of the basement had been sparedwith the exception of a bit of water damage.

As he walked over to his bench he found hischecker, which now was silent. As he stareddown at the little gadget, it finally dawned onhim what had happened. In his somewhatsleepy state before retiring, he had forgottento remove the last transistor which he wastesting. Although at the time he was testing itits leakage was low enough so as not to ringthe bell, the heat of the fire had caused itsleakage current increase to the point wherethe relay was actuated, ringing the bell. "Well,I guess you might be called a 'leakagelifesaver ' " , grinned Harry, patting the gadget.

22

0l

The incredible excursions in the field ofspace technology over the past seven years

have happened so fast that there has beenlittle time for reflection: first, Sputnik, thenlunar probes, manned orbital flights, theMariner series, Tiros satellites, and activeand passive communications satellites....other than those directly involved in theirplannings and launchings, who has had timeto ponder?

But now that a plateau has been reached, withall of the experimental firsts launched, itseems time to consider and review whathas been done, as well as where we're going.

In line with this, Stanley Leinwoll, RadioFrequency and Propagation Manager forRadio Free Europe, has made It easy for uswith his new book, "Space Communications."The book is concise and informative, andsince it's based principally on fact and datasheets released by National Space and Aero-nautics Administration, quite authoritative.

It covers, step by step, the processes andoperations involved in all U. S. launchingsfrom our Sputnik follow-up through early1964, with results and effects, in compre-hensible and readable terms i.hat make thewhole thing seem almost as simple to thenontechnical layman as a two -egg cakerecipe to the seasoned housewife.

His launching pad for the book --the reasoningas to why the communications satellites es-pecially are so important --evolves aroundthe overcrowded shortwave (high frequency)

'Hams' And

The OSCARs

Reviewedportion i Lne radio spectrum in the rangefrom 3 to 30 megacycles, with its steadilyincreasing usage, and concurrent diminishingspectrum space due to the nadir of sunspotactivity, which in turn determines the rangeof frequencies the ionosphere will reflect.(Talk about population explosion --it's fright-ening to think about all these little micro-waves bumping into each other!) There aremany good approaches to the problem ofconservation and reduction of interference,also increasing, in progress. Leinwoll con-curs with most communications experts inthe opinion that the final solution lies incommunications satellites, plus improvedconditions in shortwave bands.

The book, he says, is not intended primarilyfor technical people in the field, who pre-sumably are already aware of the conditionsin this International Year of the Quiet Sun(IQSY), and are working on remedies. Instead,he says, the book is meant to be one of practi-cal interest to the nontechnical layman, theradio amateur, and the shortwave listener; inshort, anyone interested in knowing moreabout space communications in a worldwhere it is becoming more and more im-portant. As such it is a valuable compilationof events that seem to have occurred almostdaily.

Perhaps it's not fair to Leinwoll to give shortshrift to all this, but of particular interest tothis reviewer were the chapters on the roleof radio amateurs and their "piggyback"satellites, the OSCARs (Orbiting SatelliteCarrying Amateur Radio). He tells the story

23

in detail, aided by records of organizationsand individuals who helped the project to getoff the ground.

The role was indeed a massive one, consider-ing that it was done entirely on the hams' freetime from regular jobs (he estimates a con-servative 40,000 hours) and financed entirelyby them, at no cost to the government. Butthen, as Leinwoll says, so has their role al-ways been. "From the time of Marconi to thebeginning of World War II, every major ad-vance in long-distance wireless communica-tion was discovered by radio amateurs.During that period all the great laboratoriesand research centers of the world were only

KEYINGPULSE

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5

72

track, compute orbits, etc., to be sure ofsuccess. Many exhaustive tests were held,including those for shock, pressures, tem-perature, and the like, and the package wasalso flown over several California areas,monitored from the ground. So that otheramateurs throughout the world could partici-pate, the committee was reorganized to theProject OSCAR Association, and its planswidely disseminated.

On December 12, 1961 --exactly 60 yearsafter Marconi transmitted a signal acrossthe Atlantic Ocean --OSCAR I was launchedaboard Discoverer XXXVI at Vandenburg,Calif., and soon thereafter its friendly "HI"

Sync

0 001

.1.0 001

FREQ. MULT.

369L2

L3 R

VCI

DECIMAL VALUES OF CAPACITANCE ARE INpf-I8V + OTHERS ARE IN pelf EXCEPT AS INDICATED.L i - 9 toms. tapped at 3 and 61/e turnsL2 - 9 turns, centertapped

- 31 turns, centertoppedL, - 7 turns, tapped of 2-34 turn.

VC, - Variable -capacitance diode (Pacific semiconductors 115-10/Tuning capacitors: Roof trimers. Rf toils wound with No. 72 tinned wire threaded 20turns per in.

The OSCAR transmitter circuit.

able to refine the work of these adventurous was carried throughouthobbyists."

And in the space age, the hams, whose hobbyis the only one provided for by internationaltreaty, have kept pace, as is evidenced by thestory of the OSCARs.

It started with an article in CQ Magazine, inwhich the author, Don Stoner, queried: "Cananyone come up with a spare rocket for orbit-ing purposes?"

A ham, Fred Hicks, W6EJU, asked for moredetails, started talking it up to other hams,and eventually wound up as chairman of thepreliminary Project OSCAR Committee,composed mainly of hams from several ofthe large radio clubs on the West Coast.

It took thousands of letters, phone calls,door -knockings, buttonholing of governmentofficials. Backing of the American Radio Re-lay League, in March, 1961, probably helpedmost to secure interest and approval of thenecessary government agencies, which finallyhappened in September.

Meantime, the hams had to design, build,

total of three weeks.

OSCAR I statistics:

ANT

GR0TO

CASE

the world, for a

Apogee of orbit (point farthestfrom earth):app. 268 miles.Perigee of orbit (point closest to earth):app. 153 miles.Orbital period: began at 92 minutes, endedat 89.Maximum doppler shift: 7.5 kc.Distance traveled while in orbit: more than20 million miles.Range of signal to radio horizon: app. 1400miles on overhead passes.Internal temperature: average temperaturewithin satellite 127°, corresponding to a HIrate of 10 per 6.5 seconds.Power supply: three 18 -volt mercury cellsin parallel, with estimated life period ofthree weeks.Dimensions: canister, 12 in. X 10 in. x 8 in.(Shown on Page 23.)Weight: 10 lbs., low -weight magnesiumalloy. (Container was plated with gold toreflect the most heat of the sun, partiallypainted to maintain heat balance.)

24

Launching vehicle: launched as ballast inAgena-Discoverer satellite, boosted intoorbit by Thor. (Attached by explosive boltholding an ejection spring under compres-sion, mounted on an adapter near rocket'smotor housing.)Transmitter: transistor crystal oscillatoron 72.5 mc (constructed on glass epoxyprinted wiring board), transistor amplifierand Vari-cap diode doubler on 145 mc.Keyer of transistor multivibrator andcounters of diode logic. Oscillator keyed inbase circuit. Entire internal structure en-capsulated in epoxy foam for thermal in-sulation.Orbit: North/South, 81.2° inclination toEquator.Frequency: app. 144.983 kc.Power output: 100 mw.Antenna: 1/4 -wave monopole, 19 in. long.Modulation: C. W., keyed with series ofHIs in Morse Code.Call sign: None for satellite. Ground sta-tion control assigned W6EE. Tracking andreception reports received: 5200 from ob-servers in 25 countries.

In June, 1962, OSCAR II, utilizing informationgained from the first one, was also launchedsuccessfully, with even better reception,world-wide interest and support.

OSCAR III, an active satellite, and the next

logical step for the hams, will be launchedthis winter. It will be a vhf translator satel-lite with storage batteries charged by solarcells, expected to orbit for several months,and designed to enable many more amateursin the 2 -meter band to participate.

In the Washington area, OSCAR East, a simi-lar project for the East Coast, is projectedfor 1965 under the direction of Capt. DavidJ. Veazey (USN). He feels that there is "somuch wonderful talent" in this area that acoordinated group of hams could rival orsurpass what has been done by the WestCoast. (He and several others here workedon the West Coast OSCARS.)

Capt. Veazey and the others who are con-templating the do-it-yourself project feelthat it would result in a tremendous amountof knowledge and experience gained, and thatthere are probably many opportunities---dead-load space available ----in which sucha vehicle could be launched. Yet the projectis somewhat in a dormant stage.

What is needed most now, though, he says, issomeone "to take hold of the program full-time," coordinate the efforts of those who areextremely interested but are hampered bylack of time away from their employment.

ALLENE MAGANN-

CONAR, ORDER BLANK SO

DIVISION OF NATIONAL RADIO INSTITUTE, 3939 WISCONSIN AVE., WASHINGTON 16, D.C.

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.1

25

It was known from the beginning that thebid for the Presidency of the NRIAA for

1965 would be a hotly contested race, whentwo such strong and popular members asDave Spitzer of the New York City Chapterand Howard Tate of the Pittsburgh Chapterwere the contenders for the office. DaveSpitzer finally squeezed through as thewinner.

Three old-timers are back on the slate ofofficers as National Vice -Presidents. Theyare the ever -popular and dynamic JulesCohen of the Philadelphia -Camden Chapter;F. Earl Oliver of the Detroit Chapter, whohas been elected to National Office moreoften than any other member of the AlumniAssociation; and Joseph Stocker of the LosAngeles Chapter, who was a Vice -President

ALUMNI NEWSJ. Arthur Ragsdale PresidentHoward Tate Vice PresidentFrank Zimmer Vice PresidentEugene DeCaussin Vice PresidentJules Cohen Vice PresidentTheodore E. Rose Executive Sect.

in 1957 and the chief organizer of the LosAngeles Chapter in that year. We have onenew member who is serving as a NationalOfficer for the first time and he is fully de-serving of the honor. He is James L. Wheeler,Chairman of the Pittsburgh Chapter. Ourcongratulations to these successful candi-dates for National Office.

Born in Brooklyn, N. Y., in 1908, President-Elect Dave Spitzer completed courses atthe Mechanic's Institute in draftsmanship andmechanical drawing, but never worked at itbecause he did not like sitting at a desk. In-stead, even as a child, he was interested inanything pertaining to electricity. He builtone of the first crystal Radio sets in hisneighborhood. Until Radios became common,his house was the meeting -place for friends

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Enclosed is a down payment of $ on the equipment I have listed on the reverse side. Beginning 30days from the date of shipment I will pay you $ each month until the total payment price is paid. Youwill retain title of this equipment until this amount is fully paid. If I do not make the payments as agreed, you maydeclare the entire unpaid balance immediately due and payable, or at your option, repossess the equipment. Youracceptance of this will be effected by your shipment to me of the equipment I have listed.

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26

Dave Spitzer is your new president

and neighbors anxious to see the "box" andhear what came out of it.

Spitzer's chief occupation is as a heatingEngineer specializing in oil heat. He tookthe NRI course only as a hobby at first,graduated in 1950, but has been doing Radio -TV Servicing as a sideline ever since. Hejoined the NRI Alumni Association while stilla student and has been one of the most activeand industrious members of the New YorkCity Chapter. He was elected to the ExecutiveBoard for two years, then served as Secretaryfor two years, and is now in his fifth year asChairman. He was also a National Vice -President of the Alumni Association for twoyears.

In addition to his responsibilities and activi-ties in the New York City Chapter of theAlumni Association, he is an Officer on theExecutive Board of the Coney Island Rod andGun Club, and does quite a bit of deep-seafishing. He has still another hobby, photog-raphy.

Current National President J. ArthurRagsdale will vacate his office on January 1,1965, whereupon Dave Spitzer will take over.

CHAPTER CHATTER

DETROIT CHAPTER's first meeting of theyear was taken up exclusively by a discus-sion on programming for the season. Allmembers of the Chapter are earnestly re-quested to submit any suggestions they mayhave. Here is an opportunity for all members

to do something about getting the kind of pro-grams they want. Take advantage of the op-portunity; send in as many suggestions as youlike.

FLINT (SAGINAW VALLEY) CHAPTER'sprogram was a full one in September. First,the Chapter was invited to attend a meetingheld by General Electric, which was devotedto the servicing and repair of the GE 11 -inchTV set. Then, on September 14B and K stageda meter check at one of the leading localelectronic supply houses, Taylor Electronics.Many members of the Chapter brought theirVOM and VTVM for checking on the Elec-tronic standard calibrator check.

Following this, the Zenith Company invitedthe Chapter members to Utley Town Hall atBurch Run, Mich., for the introduction of thenew Zenith receivers and Stereo. This wasfollowed by a supper and floor show, trulyan enjoyable evening.

HACKENSACK CHAPTER is one of thoseChapters that continued with its meetingsright through the summer. More power toyou, fellows: The meetings were given overprimarily to the repair of sets brought in bymembers and there was general agreementthat this was time well spent in spite of thehot weather.

Harold Jenkins demonstfated using a B andK Television Analyst on a set that was out

A hello -to -fall picnic was held jointly by theDetroit and Flint Chapters at KensingtonPark. At one table were, from right, seated,Mr. and Mrs. James Kelley and their daughterand Mrs. Andrew Jobbagy: standing, John Nagy

and Mr. Jobbagy.

27

of sync. The members derived a great dealof benefit from this demonstration. It wasthe first time most of them had seen theinstrument used for this purpose.

SOUTHEASTERN MASSACHUSETTS CHAP-TER has for some time been planning on thepurchase of a color TV receiver for use atthe meetings. The Chapter now has it, a 1964Admiral, It will be used for troubleshootingand to give the average member confidencein Servicing color TV. This will add tre-mendously to the value of the chapter's meet-ings. Members can now get a wealth of practi-cal instruction and help on servicing colorreceivers at the meetings.

The first demonstration was conducted byManuel Figueiredo and Manuel Sousa on howto converge colored TV. The members pres-ent were highly pleased with this demonstra-tion, particularly since each member had achance to do it for himself.

The Chapter has adopted a program underwhich a special meeting will be held betweenregular meeting nights. Each of these meet-ings will be devoted to the different phasesof color TV. All members who possibly canshould avail themselves of this chance to learnall they can about servicing color receivers.

All members of the Chapter, please note:The December meeting would normally fallon December 25th, but since that will beChristmas Day, the meeting will be held onDecember 18.

The Chapter wishes also to call attention tothe fact that it is in the market for a used16mm sound projector. If you have one you'dlike to sell, or know someone who wants todispose of one, drop a line to the chairman,Mr. George Schalk, P. 0. Box 1, Ridgewood,New Jersey, 07451.

LOS ANGELES CHAPTER has had all of itsequipment up for sale. Presumably, by thetime this issue of the Journal is published,some -- maybe all -- of it may have beensold. However, anyone interested should dropin at a meeting to see if any of it is left.

Graham Boyd is converting a 24 -inch PackardBell TV receiver from 24BP4 to 24CAP4.Harry Matsukane reported on his visit toWashington, D. C. He not only visited NRIbut also the U. S. Senate.

Chairman Eugene DeCaussin gave a demon-stration on his new B and K TelevisionAnalyser and promised additional demon-strations on the use of this instrument atfuture meetings.

PHILADELPHIA -CAMDEN CHAPTER mem-bers were much impressed with a talk givenby a representative of the Philco Corporationon transistors. In this talk the speaker tookan entirely new approach to the transistor,made it easier for the members present tounderstand and to work with.

The members were also scheduled to beguests of the Philco Corporation in Phila-delphia for a tour of the factory, with specialemphasis on seeing how the Television setsare made. This tour was in the making fora long time. The tour was to be made in themorning followed by luncheon as guests of thecompany.

The Chapter has had quite a few such toursand visits to factories and probably will con-tinue to have them. All of them are interest-ing and instructive. Members should takeadvantage of this opportunity to get a first-hand knowledge of the "works" in manu-facturing, broadcasting stations, etc. Thisis only one of the many benefits of member-ship in this large and very active Chapter.

SAN ANTONIO ALAMO CHAPTER ChairmanSam Dentler brought in some RCA ServicingManuals that he ordered for the Chaptersometime ago. He let the Chapter membershave them at cost. They served as the basisof an interesting discussion.

Harold Wolfe, who is an expert Auto RadioServiceman, discussed the servicing of AutoRadios. Johnnie Noll, a Telephone Companyrepairman, was scheduled to deliver a talkon the telephone distribution system. Prob-ably this lecture will have been deliveredby the time this issue is published.

John Chaney has been preparing a lectureon the fundamentals of Radar. Though fewservicemen work with Radar, it is verysimilar to Television and a talk on the sub-ject should be interesting.

SAN FRANCISCO CHAPTER members werehost to Guest Speaker Peter Wiwel, who hasspent twenty-seven years in the Electronicsbusiness. He talked very freely to his audi-ence about his experiences in Radio -TV.Among other things he told the group howimportant it is to listen carefully to cus-tomers' complaints and to adjust the com-plaints as nearly as possible to the customers'satisfaction. The members expressed theirgratitude to Mr. Wiwel for his valuable talkand invited him to speak at another meetingin the future. He promised that he would.

At the very next meeting he offered his helpas instructor to Chapter members in trouble -

28

shooting the tough dogs. The chapter acceptedhis offer with enthusiasm. He has scheduleda series of practical demonstrations on re-ceivers.

Directory of Local ChaptersLocal chapters of the NB! Alumni Association cordiallywelcome visits from all NM students and graduates asguests or prospective members. For more informationcontact the Chairman of the chapter you would like lovisit or consider joining.

CHICAGO CHAPTER meets 8:00 P. M., 2ndand 4th Wednesday of each month, 666 LakeShore Dr., West Entrance, 33rd Floor,Chicago. Chairman: Frank Dominski, 2646 W.Potomac, Chicago, Ill,

DETROIT CHAPTER meets 8:00 P. M., 2ndand 4th Friday of each month. St. AndrewsHall, 431 E. Congress St., Detroit. Chairman:James Kelley, 1140 Livernois, Detroit,Mich., VI -1-4972.

FLINT (SAGINAW VALLEY) CHAPTERmeets 8:00 P. M., 2nd Wednesday of eachmonth at Andrew Jobbagy's Shop, G-5507S. Saginaw Rd., Flint. Chairman: HenryHubbard, 5497 E. Hill Rd., Grand Blanc,Mich., 694-4535.

HACKENSACK CHAPTER meets 8:00 P. M.,last FridayCor. Lodi and Holt St., Hackensack, N. J.Chairman: George Schalk, 471 Saddle RiverRd., Ridgewood, N. J.

HA GE RSTOWN (CUMBERLAND VALLEY)CHAPTER meets 7:30 P. M., 2nd Thursdayof each month at the YMCA in Hagerstown,Md. Chairman: Francis Lyons, 2239 BeverlyDr., Hagerstown, Md. Reg 9-8280.

LOS ANGELES CHAPTER meets 8:00 P. M.,2nd and last Saturday of each month, 4912DeCaussin, 5870 Franklin Ave., Apt. 203,Hollywood, Calif., NO 4-3455.

MINNEAPOLIS -ST. PAUL (TWIN CITIES)CHAPTER meets 8:00 P. M., 2nd Thursdayof each month, at the homes of its members.Chairman: Paul Donatell, 1645 SherwoodAve., St. Paul, Minn., PR 4-6495.

NEW ORLEANS CHAPTER meets 8:00 P.M.,2nd Tuesday of each month at Galjour's TV,809 N. Broad St., New Orleans, La. Chairman:Herman Blackford, 5301 TchoupitoulasNew Orleans, La.

NEW YORK CITY CHAPTER meets 8:30P. M., 1st and 3rd Thursday of each month,St. Marks Community Center, 12 St. MarksPl., New York City. Chairman: David Spitzer,

2052 81st St., Brooklyn, N. Y., CL 6-6564.

PHILADELPHIA -CAMDEN CHAPTER meets8:00 P. M., 2nd and 4th Monday of each month,K of C Hall, Tulip and Tyson Sts., Phila-delphia. Chairman: John Pirrung, 2923 Long -shore Ave., Philadelphia, Pa.

PITTSBURGH CHAPTER meets 8:00 P. M.,1st Thursday of each month, 436 Forbes Ave.,Pittsburgh. Chairman: James L. Wheeler,1436 Riverview Dr., Verona, Pa. 793-1298.

SAN ANTONIO ALAMO CHAPTERmeets 7:30P. M., 3rd Wednesday of each month, Beetho-ven Home, 422 Pereida, San Antonio. Chair-man: Sam 0. Dentler, 329 Southcross, SanAntonio, Texas. WA 2-8682.

SAN FRANCISCO CHAPTER meets 8:00 P.M.,1st Wednesday of each month, 147 Albion St.,San Francisco. Chairman: Peter Salvotti,2543 Great Hwy., San Francisco, Calif.

SOUTHEASTERN MASSACHUSETTS CHAP-TER meets 8:00 P. M., last Wednesday ofeach month, home of Chairman John Alves,57 Allen Blvd., Swansea, Mass.

SPRINGFIELD (MASS.) CHAPTERmeets 7:00P. M., last Saturday of each month at shop ofNorman Charest, 74 Redfern St., Springfield,Mass, Chairman Steven Chomyn, Powder MillRd., Southwich, Mass.

HOLIDAYS,

HAPPY

29

THE L 0 N G AND THE short

OF 'HORNS'PAY OFF IN DB AND BROAD FREQUENCY RESPONSE GAINS

BY ARTHUR L. MUNZIG

Did you ever wish it was practical to use a"horn" antenna? The dimensions for a horndesigned for TV low frequencies are almostprohibitive for mounting on a roof -top.

In Fig. 1 is shown a conventional design for

DIRECTIONOF

RECEPTION

FT

300 OHMFEED POINT

FIG. 1. Conventional design having "chicken wire"netting as the conductor.

a horn for TV -FM reception having "chicken -wire" netting as the conductor.

The gain of a conventional horn can be practi-cally doubled if the horn (as shown in Fig. 1)is rotated 90 degrees, as shown in Fig. 2.The "long horn" now has an upper and lowerplate but with an aperture (opening) of only4 ft. The size is still impractical for mount-ing in an attic or on the roof.

However, this is now a thing of the past.Presented herewith is the author's versionof a SHORT -HORN antenna designed for TV -FM reception having a flat frequency re-sponse from 54 mc to 890 mc, and a con-sistent 10 db gain. It can be mounted con-veniently on your roof -top or in the attic.

Shown in Fig. 3 is a design for a short -hornantenna. It now has been shortened to 4 ft.and the aperture has been reduced to 2 ft.The short horn still has a flat frequencyresponse from channel 2 through 83, and aconsistent 10 db gain. However, the inputresistance has been reduced to 150 ohms.This isn't too bad a miss -match, and can betolerated with the high gain and broad fre-quency response advantages.

Mounting should now be a simple matter. Thereader can easily improvise a frame out ofdry wood, or reinforce the edges of thechicken wire by soldering to a narrow metalstrap around the outer edges, and supportingwith polystyrene strips for insulation.

FIG. 2. Conventional horn rotated 90 degrees. FIG. 3. Design for a "short -horn" antenna.

30

STATEMENT OF OWNERSHIP, MANAGE-MENT AND CIRCULATION (Act of October23, 1962; Section 4369, Title 39, United StatesCode)

1. Date of Filing; October 1, 1964.2. Title of Publication; NRI Journal3. Frequency of issue; bimonthly4. Location of known office of publication;

National Radio Institute, 3939 Wisconsin Ave.,N. W., Washington, D. C. 20016.

5. Location of the headquarters or generalbusiness offices of the publishers; NationalRadio Institute, 3939 Wisconsin Ave., N. W.,Washington, D. C. 20016.

6. William F. Dunn (editor and publisher),6314 Tulsa Lane, Bethesda, Maryland;managing editor, Allene Magann 220 E.Windsor Ave., Alexandria, Virginia

7. Owner (If owned by a corporation, itsname and address must be stated and alsoimmediately thereunder the names and ad-dresses of stockholders owning or holding 1percent or more of total amount of stock. Ifnot owned by a corporation, the names andaddresses of the individual owners must begiven. If owned by a partnership or otherunincorporated firm, its name and address,as well as that of each individual must begiven.)

Emma Smith Stuart, 59 Nacional St.,Salinas, Calif.

Susan Smith Bartlett, 1 Highland Ave.,Dover, Delaware.

Elsie Smith Davis, RFD 1, Rochester, NewHampshire.

Carol Smith Galbraith, 430 E. LedbetterDrive, Dallas 16, Texas.

Michael Morrison Galbraith, 3550 LakeShore Dr., Apt. 2508, Chicago 13, 111.

The National Radio Institute CharitableTrust, % J. E. Smith, 4521 Crest Lane,McLean, Va.

Gail Galbraith Peek, 305 N. Virginia Ave.,Falls Church, Virginia.

James E. Smith, Sarah Morrison Smith,4521 Crest Lane, McLean, Virginia.

James Morrison Smith, Lee MorrisonSmith, James Morrison Smith, Jr., TerryMorrison Smith, 4523 Crest Lane, McLean,Virginia.

Marjory M. S. Sarich, Charles B. Sarich,James R. Sarich, 4525 Crest Lane, McLean,Virginia.

David H. Smith, RFD 1, Rochester, NewHampshire.

8. Known bondholders, mortgagees, andother security holders owning or holding 1percent or more of total amount of bonds,montages or other securities (if there arenone, so state); none.

9. Paragraphs 7 and 8 include, in caseswhere the stockholder or security holder ap-pears upon the books of the company as trustee

or in any other fiduciary relation, the nameof the person or corporation for whom suchtrustee is acting, also the statements in thetwo paragraphs show the affiant's full knowl-edge and belief as to the circumstances andconditions under which stockholders andsecurity holders who do not appear upon thebooks of the company as trustees, hold stockand securities in a capacity other than that ofa bona fide owner. Names and addresses ofindividuals who are stockholders of a corpo-ration which itself is a stockholder or holderof bonds, mortgages or other securities ofthe publishing corporation have been includedin paragraphs 7 and 8 when the interests ofsuch individuals are equivalent to 1 percentor more of the total amount of the stock orsecurities of the publishing corporation.10. This item must be completed for all

publications except those which do not carryadvertising other than the publisher's ownand which are named in sections 132.231,132.232, and 132.233, postal manual (Sections4355a, 4355b, slid 4356 of Title 39, UnitedStates Code)

A. Total No. copies printed (Net PressRun) Nov. 63 thru Sept./Oct. 64: 307,105;average No. copies each issue during pre-ceding 12 months: 38,388; single issue near-est to filing date: 38,000.

B. Paid Circulation1. To term subscribers by mail, carrier

delivery or other means; average No. copieseach issue during preceding 12 months: 186;single issue nearest to filing date:231.

2. Sales through agents, news dealers,or otherwise: none.

C. Free distribution (including samples)by mail, carrier delivery, or by other means:average No. copies each issue during pre-ceding 12 months: 38,202; single issue near-est to filing date 37,779.

D. Total No of copies distributed; averageNo. copies each issue during preceding 12months: 38,388; single issue nearest to filingdate: 38,000.I certify that the statements made by me aboveare correct and complete.

NATIONAL RADIO INSTITUTEAllene Magann, Managing Editor

The wise men of antiquity, when theywished to make the whole world peacefuland happy, first put their own states intoproper order. Before puttingtheir statesinto proper order, they regulated theirown families. Before regulating their ownfamilies, they regulated themselves. Be-fore regulating themselves, they tried tobe sincere in their thoughts. Before beingsincere in their thoughts, they tried tosee things exactly as they really were.

Confucius.

31

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239