PRACTICAL TRANSISTOR RECEIVERS Practical-Transitor-Receiver-Book-1.pdf · least a three -gang condenser, which is both bulky and difficult to align. They are, however, slightly cheaper

PRACTICALTRANSISTOR

RECEIVERSBOOK I

30 COMPLETELY DIFFERENTRECEIVERS

by

CLIVE SINCLAIR

Complete Circuit Diagrams with list ofBritish and American Transistors

BERNARDS RADIOMANUALS

TRANSISTOR SERIES 2

PRACTICALTRANSISTOR

RECEIVERS

By Clive Sinclair

BOOK INO. 2 IN THE TRANSISTOR SERIES

CORRECTIONS

Page 17. Circuit 14: -A fixed capacitorhaving a value of 0.01mfd. should be insertedbetween the base of Trl and the tuned circuitso as to isolate the base from the negative sideof the battery.

Page 46. Circuit 36: - The letters W andZ should be interchanged on the circuitdiagram.

LONDON : BERNARDS (PUBLISHERS) LIMITED

FIRST PUBLISHED JANUARY, 1959

We invite all authors, whether new or well established, to submit manuscripts for publication.The manuscripts may deal with any facet of electronics but should always be practical. Any circuitdiagrams that may be included should have been thoroughly checked by the author. If you areconsidering trying your hand at writing this type of book we suggest that you let us have a shortsummary of the subject you intend to cover. We will then be able to let you know the size of bookrequired and perhaps give you some advice on presentation required.

Printed by V. Cooper and Partners Ltd., Flitcroft Street, W.C.2for Bernards (Publishers) Ltd., The Grampians, Western Gate, London, W.6

PREFACEThis book is the second in a new series, devoted entirely to the use of

transistors. In the near future we will be publishing further books in this series dealing

with audio amplifiers, transmitters, hearing aids, radio control, F.M. receivers,

television sets, sub -miniature radio sets, etc. All using transistors. If you would like

to write to us saving the branches of electronics which interest you most, we will be

very grateful and will be able to publish exactly the type of books you desire.

CLIVE SINCLAIR

CONTENTS

Page

INTRODUCTION ... 7

DIODE PLUS AMPLIFIER CIRCUITS 9

REGENERATIVE RECEIVERS ... 21

T.R.F. RECEIVERS ... 35

SUPER REGENERATIVE RECEIVERS 40

LIST OF BRITISH TRANSISTORS ... 48

LIST OF AMERICAN TRANSISTORS 51

INTERNATIONAL EQUIVALENTSAMERICAN SEMI -CONDUCTORS

LIST OF BRITISH, EUROPEAN AND55

PRACTICAL TRANSISTOR RECEIVERS 7

INTRODUCTION

TRANSISTOR RECEIVERS

FOR the sake of convenience this book hasbeen divided into five different sections, eachsection dealing with a different type of receiver.In each type the circuits become progressivelymore complex and thus more difficult to build ;however, all the receivers are well within thescope of the average home constructor. Atthe end of the book is a comprehensive list ofthe British and American transistors, and it ishoped that this list will serve as a useful guidewhen purchasing. Some of the transistors arenot yet on the retail market, but it is only amatter of time before every type is availableat a reasonable price.

The first section of the book deals with thesimple crystal diode plus audio amplifier typeof set which is so popular because of its lowcost and basic simplicity. The receivers suffer,however, from one or two disadvantages.Firstly, due to the non -linearity of the detector,the sets have rather low sensitivity. As thesignal strength decreases so the efficiency of thedetector also decreases until a point is reachedwhere no signal is being fed to the audioamplifier. This means that a good aerial mustbe used for best results except in areas of veryhigh signal strength where a ferrite rod orframe type of aerial usually is sufficient. Thesecond major disadvantage is the lack of selec-tivity, which means that two or more stationscan often be heard at the same time. Thisfault may be partially overcome by careful coildesign, the primary requirement being that thecrystal diode or transistor and the aerial andearth system do not put too much load on thetuned circuit. On the credit side is the ex-tremely high quality of reproduction obtainable

with a good design. Where a fixed receiver isrequired, or a long aerial is no disadvantage,this type of set is unbeatable from the pointof view of quality and economy. Because ofthe high frequency capabilities of the ger-manium diode, all the circuits of this sectionare able to operate up to 100 Mc/s or moreas long as a diode such as the 0A70 is used.The actual method of operation of each typeis described at the beginning of its respectivesection.

The second part of the book deals with theregenerative receiver as applied to transistors.This type of set, using thermionic valves, hasbeen a great favourite both for the broadcastand the shortwave bands. Its advantages arevery high sensitivity and selectivity combinedwith very low cost compared with a superhetor normal T.R.F. Unlike the valve types,where almost any valve will regenerate, onlyspecial R.F. types of transistor may be used.In the past many designs have been describedwithout actually specifying the types to be usedand this has led to disappointment and con-fusion, thus it is suggested that the componentsspecified be fairly rigidly adhered to. Themain disadvantage with the regen. is its poorquality of reproduction due to non-linearamplification. In shortwave receivers, however,this may not be very important. Another ratherannoying disadvantage, of what is otherwise souseful a circuit, is the danger of the set burstinginto oscillation and acting as a small transmitterof interference. This may be overcome byisolating the detector from the aerial by a pre-ceding stage of R.F. amplification, but thismeans losing the advantage of single tuning

8 PRACTICAL TRANSISTOR RECEIVERSwhich is by no means inconsiderable. As noalignment is required with regens. the sets maybe built without test equipment, however theyrequire a certain amount of skill for mostsensitive operation.

The third section is devoted to receivers withtuned radio frequency stages. These sets arenot very popular because for a really sensitivereceiver two or more stages of radio frequencyamplification are required and this means atleast a three -gang condenser, which is bothbulky and difficult to align. They are, however,slightly cheaper to build than the superhets andare capable of better quality. If and whentetrode transistors become available the T.R.F.is likely to be used more widely, but until thenthe superhets will reign supreme.

The circuits in section 4 will be of specialinterest to the shortwave and V.H.F. enthu-siasts as the receivers shown are capable ofoperations up to about 60 Mc/s. At first sightthese circuits will appear rather unfamiliar asvery little has been published about transistorsuper regenerative receivers in this country.Their great advantage over the other sets in thisbook is their unbelievable sensitivity and eco-nomy of components. A single stage superregen. is even more sensitive than a superhethaving three I.F. stages ; furthermore, theupper frequency limit is much higher for agiven type of transistor and does, in fact, exceedthe alpha frequency cut-off which is defined asthe point at which the gain is 3db down onthat at 1 kc/s. Because a twin gang condenseris not required, the receivers may be made verycompact without the use of specially madecomponents. The disadvantages of the superregen. are rather broad tuning, due to loadingof the tuned circuit, and their tendency toradiate interference. This latter effect is vir-tually unimportant with transistor super regens.because only a very small aerial is used and thepower of the oscillations is also small, never-theless a certain amount of caution is called for.

Unfortunately the super regen. is ratherunsatisfactory on the normal broadcast bands.The reason for this will be explained later inthe book.

The last set of circuits, those in section 5,are superheterodynes. This type of circuit isused in all the British commercial receivers forthe obvious reason that it is by far the mostsatisfactory. It is, however, also the mostexpensive.

Transistor superhets usually differ from theirvalve counterparts in that they use more stagesof I.F. amplification. The average portable,for example, usually uses two I.F. stages com-pared with one in the valve sets. This is doneto obtain sufficient sensitivity in difficult areasbut it is by no means always necessary. TheI.F. stages can, of course, be made regenera-tive.

The superhet has excellent sensitivity andselectivity and usually requires only twovariably tuned stages. The only disadvantage,as far as the broadcasting bands are concerned,is the rather high cost. This is due to the factthat several R.F. transistors and I.F. trans-formers are needed, and these are relativelyexpensive items.

It is not advisable for someone who has hadno experience with transistors to start with asuperhet as they can be somewhat tempera-mental. If some of the receivers in sections1 and 2 are built first then little difficulty shouldbe found.

Finally, a few words on the use of transistorswill not be out of place.

Despite their robust physical properties,transistors are easily damaged by heat, soalways grip the leads with a pair of blunt -nosedpliers when soldering them. Alternatively, atransistor socket may be used and, if the set isonly temporary, various transistors may betried without the necessity for unsoldering andresoldering the connection. Another way inwhich transistors may be ruined permanentlyis to connect the battery the wrong way round.So always check for this before switching a newbattery into a circuit.

Some types of transistor have glass encap-sulation and the paint may scratch or peel off.If this happens repaint them, as transistor& aresensitive to light and may pick up hum fromelectric lighting.


SECTION I

DIODE PLUS AMPLIFIER CIRCUITS

The block diagram of this type of receiveris shown in Fig. 1. The incoming signal ispicked up by the aerial and coupled eitherdirectly, capacitively or inductively to the tunedcircuit which offers a low impedance to allfrequencies except that to which it is tuned.The tuning may be accomplished by varyingeither the condenser or the coil. It is far moreusual to use a variable tuning condenser, but ifa very small receiver is required then inductiveor permeability tuning is more attractive.

The R.F. signal is now fed to the demodu-lator or detector, which may be either a crystaldiode or a transistor. The crystal diode hasthe advantage that it will operate up to veryhigh frequencies but, unlike the transistor, itgives no A.F. gain.

The A.F. signal is then amplified by a tran-sistor audio amplifier which may use anythingfrom one to six transistors, depending on theamount of gain required. If more than onetransistor is used then the form of coupling

R.F. TUNED

CIRCUIT

R.F

DETECTOR

A.FA.F.

AMPUFIER

L/SOR

PHONES

Fig. I.

I() PRACTICAL TRANSISTOR RECEIVERS

between the transistors must be decided upon.Basically there are three different forms-resistance-capacity coupling, transformer coup-ling and direct coupling. Each of these has itsadvantages. If high quality is required, thenresistance -capacity coupling should be used,but for maximum gain per transistor, trans-former coupling is unbeatable. The advantageof the direct -coupled circuit is its extremeeconomy of components, thus it is very usefulwhen building sub -miniature amplifiers andreceivers.

CIRCUITS 1 AND 2

The two simplest types of transistor receiverpossible are shown in circuits 1 and 2. Thesetwo sets are ideal for those wishing to gainexperience with transistors as they require noalignment. The entire power requirements aresupplied by a single cell which may be eithera zinc or a mercury type. The mercury cells,which are relatively new, are extremely usefulfor transistor have more or lessconstant voltage with life. Furthermore, theirweight -to -power ratio is far smaller than thatof a zinc -carbon cell.

These two sets, if used with a good aerialand earth, can give amazing headphone volume.Any make of P.N.P. junction transistor may beused. In the first set the signal is demodulatedby the crystal diode and then amplified by thetransistor, if a high frequency transistor is used,

such as the Mullard 0C45 or 0C44, then thecrystal diode may be omitted ; however, this isnot normally worth while, due to the extra costof R.F. transistors. In the second set, detec-tion takes place in the base -emitter circuit andthe resultant A.F. appears, in amplified form,

in the collector -base circuit. No crystal diodeis required because even A.F. transistors willdetect quite well in the broadcast band if usedas common -base amplifiers instead of the usualcommon -emitter amplifier. The second set has,however, somewhat less gain than the first.

CIRCUIT 3

The last two receivers suffer from twodefects. Firstly, the tuning is very broad, dueto the heavy loading of the tuned circuit by thedetector. Secondly, there is no provision forvolume control. These two points are takencare of in circuit 3. The tuned circuit ismatched into the diode by means of an R.F.stepdown transformer having a turns ratio ofapproximately 5 to 1. If a commercial tuningcoil is used then approximately 10 turns of thickenamelled copper wire should be wound imme-diately above the tuning coil.

The battery supply may be anything from1.5 to 6 volts with ordinary germanium junc-tion transistors. If one of the AmericanN.P.N. types of transistor is available this maybe used equally well, but in this case the batterypolarity should be reversed.


Those of you who like experimenting can tryusing the springs on a bed as an aerial. Ifthis is done no earth is usually necessary.

Another possibility, which frequently gives verygood results, is connecting the aerial side of thecoil to earth via a water -pipe and leaving theearthy side of the coil free. A television aerialis also quite useful.

CIRCUIT 4

The fourth circuit, while embodying the im-provements of the third, has the added advan-tage of controlled base bias. For a transistorto amplify it must receive a negative (positivein the case of N.P.N. transistors) bias on boththe base and the emitter. In the first threecircuits this bias has been supplied by theleakage from the collector which exists in alltransistors to a certain extent. This, however,is rather unsatisfactory as it does not enableany control over the base bias current and,furthermore, if the transistor is to handle areasonable amount of power the leakage willbe too small and severe distortion and clippingwill result.

In this circuit the base power supply is taken,via a resistor, from the same battery that sup-plies the collector. This saves the complica-tion of a second battery. This method ofbiasing does not provide D.C. stabilisation,however, and sets which incorporate the variousmethods will be described later.

R, may have a value of anything from 100 Id/to 1 meg.Q, depending upon the power outputrequired and the type of headphones used.High impedance 'phones gives the best resultswith single -stage sets and require a high valueof bias resistance, but in very strong signalareas low impedance 'phones give good resultsand greater output. These should be used witha low value bias resistor.

The coupling capacitor should have a valueof 0.5 mfd. or greater because of the lowimpedance input of the transistor. If a valvecoupling condenser of 0.01 mfd. is used thelow frequencies will be severely attenuated,giving a ' tinny ' sounding output. 6 v.w. elec-trolytics are perfectly satisfactory because of thelow supply voltage.

CIRCUIT 5

The fifth circuit diagram incorporates a stillfurther improvement but, for the sake of sim-plicity, the volume control has been left out.In its place has been inserted a stepdown trans-former having a turns ration of 4.5 : 1. Thismatches the output of the crystal diode to theinput of the transistor and gives considerableimprovement in gain. The distortion intro-duced by the transformer is so small that it isquite unnoticeable.

The average resistance -capacity coupled stagegives a gain of approximately 20dB comparedwith 40dB from a transformer coupled stage.This corresponds to gains of 100 times and

12 PRACTICAL TRANSISTOR RECEIVERS

10,000 times respectively and the theoreticaladvantage of transformer coupling is very clear.There are a large number of different makesof transistor interstage transformers on theretail market and any of these should provesatisfactory. The ones used in the prototypeswere made by Fortiphone Ltd., type No. S1,which have a size of only 0.4 x 0.4 x 0.25 in.and are thus admirably suited to miniature andsub -miniature work.

The resistance, condenser and headphonevalues are the same as those in the last circuitand the battery voltage may again be anythingfrom 1.3 to 6 volts. Despite the increased gaina good aerial is still usually necessary, becausethere is no improvement in the detectorefficiency.

CIRCUIT 6

This circuit is rather unusual in that it usestwo transistors in push-pull. The advantagesof this are increased sensitivity, power outputand quality. Although direct coupling has beenused there is no reason why any other formshould not be used and the reader will find itsimple to adapt the transformer coupling ofcircuit 5, for example, to this circuit.

The secondary of the transformer is split intwo halves, each half feeding one side of theamplifier with a signal which is opposite inphase to that of the other. The two transistorsshould be matched, as nearly as possible, to

one another. Mullard OC72s are sold in

matched pairs under the code number 2-0072,and these are ideal. Matching the diodes is notquite so important, but a severe mismatchwould produce distortion. It is possible to useonly one diode which would be connectedbetween the centre top of the secondary of thetransformer and the positive side of the battery.

The selectivity of the set may be considerablyimproved by leaving the primary untuned andtuning each half of the secondary. For thispurpose a twin -ganged condenser is ideal, andif the two halves of the coil are wound withexactly the same number of turns no alignmentwill be necessary.

The two halves of the secondary must bewound on either side of the primary for properoperation. The two headphones are wired inseries as usual and the negative side of thebattery is taken to the wire joining them.

CIRCUIT 7

If a second stage of audio amplification isadded to the types of receiver shown in circuits1-6 a considerable improvement in volume isobtained. In areas of high signal strength, loudspeaker volume is often obtainable with thesesimple two transistor circuits, but for this trans-former coupling as is used in circuits 9 and 10is preferable.


A good aerial will be just as necessary aswith the earlier circuits because no R.F. gainhas been provided. Circuit 7 is resistance capa-city coupled throughout. This method is veryeconomical and gives good quality, but as themismatch between the two transistors is notcompensated for maximum gain is notobtained.

As in all transistor audio amplifiers the inter -stage coupling capacitor must have a high valueif the signal is to be passed without undueimpedance. A value of 6 mfd. is more thansufficient and since it need only be 3 v.w. thephysical size may be extremely small.

None of the component values are very cri-tical ; all the components may be 20 per centtolerance. With the value of base bias on thesecond transistor the headphones should havean impedance of approximately 2,000 ohms.If any other value of headphone impedance isused it may be necessary to vary the bias.

A loudspeaker, with suitable matching trans-former, may be used in place of the 'phones,but as the output is very low a sensitive speakerwith a diameter of 5 in. or more should beused. T.S.L. Lorenz speakers are ideal becauseof their high sensitivity.

CIRCUIT 8

This receiver has been fully stabilised by theconventional method. One of the annoyingproperties of the transistor is its extreme tem-perature dependence. As the external tem-perature increases the collector current alsoincreases, which, of course, causes a furtherincrease in the junction temperature and thecycle begins again. If the stage concerned ishandling a considerable amount of current tostart with, this will increase until the transistoris destroyed.

4) .11 "ale


The obvious way to prevent this minordisaster is to reduce the D.C. gain of the tran-sistor to as near unity as possible. For it is theD.C. gain that causes the collector to pass ahigh standing current.

There are several possible methods of apply-ing negative feed back to reduce the D.C. gain,but the method used in this circuit is the onethat has been generally adopted. The outputof a normal junction transistor is out of phasewith the input. Thus if a resistance is insertedbetween the emitter and ground it will applynegative feedback over that particular stage.However, this feedback would be more or lessequally effective over the entire amplified range.To prevent this the resistance is bypassed by ahigh value electrolytic condenser so that onlyD.C. is fed back.

Another method, sometimes used, is to takethe base bias current from the collector instead

of the H.T. supply. In this case the resistanceis usually divided into two halves, the centretap being taken to earth via an electrolytic.

CIRCUITS 9 AND 10

Building this receiver for the first time,people are often amazed at the high per-formance. Using a good aerial and earth30 milliwatts output is usually obtainable and,with a good speaker, this is more than suffi-cient for the average living room. The highgain of the set is due to the transformer coup-ling used between stages. With high gaintransistors, the overall power gain of this setshould be about 70dB or about 10 milliontimes.

Circuit 10 is similar to circuit 9 except thatthe diode is transformer coupled to the firsttransistor and the receiver has been stabilised_


If a loudspeaker is used in either of these cir-cuits the output transformer should have aprimary resistance of about 250 and a turnsratio of 18:1; this will match the output ofthe transistor to the loudspeaker voice coil,which should be 3 ohms. It is often possibleto purchase single balanced armature earpieceson the surplus market, and these make idealsmall speakers if connected directly to theoutput transistor without a matching trans-former.

The high value electrolytic connected acrossthe battery serves as a low impedance bypassas the battery resistance begins to rise. If it isomitted there is the chance of relaxationoscillations occurring towards the end of lifeof the battery.

CIRCUIT 11

In areas of low signal strength, the last twocircuits might provide insufficient gain to drive

a loudspeaker, even when used with an efficientoutdoor aerial. This circuit overcomes thisdifficulty by using three stages of audio ampli-fication instead of two.

The output from the diode is direct coupledinto the first transistor, the .001 mfd. capacitorremoving any residual R.F. component of thesignal. The first transistor then amplifies thesignal and feeds it, via the 6 mfd. capacitor, toTr, which again amplifies the signal. Thesecond transistor is transformer coupled to theoutput stage.

It would be possible to couple the first tran-sistor to the second by means of a transformerand this would mean an increase of about 15dBin the overall gain. It would, however, alsomean increased distortion and is thereforeundesirable.

Within about 20 miles of a transmitter it isusually possible to pick up a signal using onlya ferrite rod aerial. But in this case the set



could only be expected to feed an earpiece orpair of headphones.

If a ferrite rod is used, the case in which theset is built must not be metallic as this wouldshield the aerial and prevent it from pickingup any signal. There are a large number offerrite rods on the market and any one of thesewill work satisfactorily.

CIRCUITS 12 TO 15

One of the advantages that the transistor hasover the valve is its ability to operate well indirect -coupled circuits. Direct coupling withvalves is difficult because the grid and anodesupply voltages are of opposite polarity anddiffer from one another in value by a factorof anything up to 1,000. With the transistor,however, the situation is far more satisfactory.Both the collector and the base require negativesupplies (positive for N.P.N. transistors).Direct coupling has several advantages overother types when used in A.C. amplifiers. Asno capacitors separate the stages the frequencyresponse is usually superior and the receiver oramplifier requires fewer components and may,therefore, be made far more compact at ex-tremely low cost.

The receiver in circuit 12 is a very goodexample of the amazing simplicity that is pos-sible with direct coupled receivers. Despitethe fact that this is a three -stage receiver, notone coupling condenser or transformer is used.A careful study of the circuit will reveal thatthe second transistor acts as the collectorresistance for the first, and that the first tran-sistor acts as the base resistance for the second.Thus the collector -emitter current of the firsttransistor is always exactly equal to the base -emitter current of the second transistor.Although the collector of the first transistorfeeds into the emitter of the second and theemitter into the base, as in most common basecircuits, the second transistor is actually acommon emitter amplifier because the outputis taken from the emitter and the collector.

If the crystal diode and the .001 nifd. con-denser are removed, and an R.F. transistor isused for the first stage, then the receiverbecomes simpler still. In this case Tr, actsboth as a detector and as an A.F. amplifier.The sensitivity is usually improved by thismodification.

Circuit 13 shows another form of directcoupling. The resistances in the emitter leadsare not bypassed so there is a considerableamount of degeneration. This, however, givesthe receiver very good frequency response. Ifhigher gain is required further similar stagesmay be added without fear of instability.

Another extremely simple circuit is shownin circuit 14. The receiver uses what is knownas a tandem amplifier. The first transistordemodulates the R.F. signal and also suppliessome amplification. Tr, acts as a commoncollector amplifier and thus has a high input


1..µF

C> r_+

-4-- I<,,,c.c

10.K.O.

O2.K.f1.

1.K..Q.

O2.K.n.

Circuit. 13.


and low output impedance ; this means that notap is required on the coil for correct matching.Tr, also serves as the base bias for Tr whichis a normal common emitter amplifier. Tr,supplies current gain and Tr, supplies bothcurrent and voltage gain. The battery voltageis in no way critical but should not exceed6 volts with normal transistors.

Circuit 15 is a combination direct coupledand r -c coupled receiver. The first transistorserves both as detector and audio amplifier, forbest operation this should be an R.F. type suchas the 0C45. Tr, serves to match the highoutput impedance of Tr, to the low inputimpedance of Tr,. Thus Tr, does the samejob as a 4.5:1 stepdown transformer except thatthere is very little voltage loss and the overallgain of the receiver is greater. Tr, and Tr,may be any low signal A.F. P.N.P. transistorsuch as the 0071. The headphones or earpieceshould be about 1 kc2 at 1 kc/s.

CIRCUITS 16, 17 AND 18

It may be some time yet before the transistoris capable of doing all the jobs that valves can,but there are some fields in which the transistorcan do things which are quite impossible forvalves. A good example of this is the tran-sistor's ability to operate well at amazing lowlevels of power. This makes possible thedesign and construction of free power receivers,that is receivers which require neither internalbatteries or connection to the mains but obtaintheir power from some free source such as

sunlight. As silicon cells, which convert opticalinto electrical energy, are not generally avail-able, there is little point in discussing them inany detail. It is sufficient to say that, withcertain limitations, they may be wired intoreceivers in place of the more usual batteries.

There is, however, another form of freeenergy which is readily available and easilyconverted into usable form, namely, electro-magnetic radiation from all forms of broadcast-ing stations. If a good outdoor aerial is fedinto an ordinary crystal set the demodulatedoutput is usually capable of feeding a pair ofheadphones without further amplification. Ifthe headphones are removed and a smoothingcircuit put in their place, a source of D.C.potential becomes available and may be usedto power any single transistor receiver. Thisform of power supply is illustrated in circuit 18.

If the receiver is to be tuned to a strong localstation, an external crystal set may be unneces-sary, as is the case in circuit 16. In this setthe diode supplies both the signal and thepower to drive the transistor. The collector ofthe transistor is connected to the output of thecrystal diode via the headphones so that partof the current available is used to power thetransistor.

Circuit 17 shows another receiver whichoperates in a similar manner. There the tran-sistor is operated as a common base amplifierand the emitter -base junction acts as a diode,charging the 1 mfd. capacitor and thus produc-ing the energy for the collector. Either aP.N.P. or an N.P.N. transistor may be usedin this circuit.



SECTION II

REGENERATIVE RECEIVERS

All the receivers in the last section sufferedfrom lack of sensitivity and selectivity. Thisis overcome in the receivers in this chapter byfeeding energy from the output of the detectorback to the input.

A R.F. transistor is used as the detector. Aswell as detecting the signal and giving A.F.amplification, the transistor amplifies at R.F.The output of a junction transistor is out ofphase with the input so some method must be

used for changing the phase while the signal isfed back. If this is not done, the feedback willbe negative and will tend to cancel out thesignal at the input.

If too much signal is fed back the receiverwill burst into oscillation and cause inter-ference in nearby sets, so some means of con-trolling the feedback is required. As theoutput is normally coupled to the input bymeans of a winding on the tuning coil, the

RF. TUNEDCIRCUIT

PHASE

CHANGER

TRANSISTORDETECTOR

RE4111

R.F.

A.F AFAMPLIFIER

USOR

PHONES

Fig.2.


feedback may be varied by varying the coup-ling between the two coils. Alternatively, avariable condenser may be included in thefeedback loop. Another system which hasthe advantage of improved stability is to fix thepercentage feedback and to vary the gain ofthe transitor by altering either the base or thecollector bias.

The effect of the positive feedback is to raisethe Q of the tuning coil by tending to cancelout the resistances in the circuit. Thus the

regen.' has very good selectivity. The dis-advantages of the regen. are the danger ofcausing interference with other receivers andrather poor quality of reproduction.

CIRCUIT 19

The receiver in circuit 19 uses V, as acommon emitter regenerative detector. If thereceiver is to be used without an aerial or earth

then the coil should be wound on a ferrite rod.Even if an aerial is used, a ferrite rod is stillan advantage as it has an extremely highand thus gives the set maximum sensitivity.L, should have 'approximately 60 turns of 44or 46 d.c.c. copper wire wound in three layers.The input tap is taken at the 10th turn fromthe ground end of the coil. L2 consists of 20turns, wound in the same way, alongside L,.It is best to make L2 capable of sliding alongthe ferrite rod as this will give a form of presetcontrol over the regeneration.

The output from the coil is coupled to thefirst transistor by means of the .01 mfd. con-denser. Once adjusted, the coupling betweenthe two coils is left alone and the regenerationis controlled by controlling the gain on VI.This is done by varying the base bias resistanceand was found when tested to give a verysmooth control. V, should be a high grade


R.F. type of transistor such as the Mullard0C44 or 0045 ; alternative types are shown inthe list at the end of the book.

The A.F. output from V2 is resistance -capacity coupled to V,, which should now berecognised as a common emitter amplifier.

In the circuit a 1.5 volt battery is shown ;however, there is no harm in using any voltageup to about 6 volts. In fact, some R.F. tran-sistors will not operate at this frequency withonly 1.5 volts.

Should an external aerial be found necessaryit may be connected between the coil and.01 mfd. coupling capacitor. Do not makethe aerial too long as it tends to damp downthe tuned circuit and make oscillation difficult.

When the set is completed, switch on andconnect a few feet of aerial. Now turn thetuning condenser until a local station is heard.

Vary the 1 mega pot. until the receiveroscillates, then readjust it until the set is justoff the point of oscillation. This is the mostsensitive setting. If oscillation is impossibletry reversing the connections to L2, as this maybe providing negative feedback instead of thepositive feedback required.

CIRCUIT 20

In areas of low signal strength the receiverin circuit 19 may not have sufficient gain todrive the earpiece to a satisfactory volume. Ifthis is the case, another stage of audio amplifi-cation is often sufficient to overcome the prob-lem. Circuit 20 shows a set of this type, theregenerative detector is basically similar to thatof the last set but is controlled in a differentmanner. Instead of using a variable base biasresistor, and thus controlling the transistor

Olo

411,

0C44.

C

OD

OC.70

Circuit. 20.

3.V.


gain, the current through the feedback loop isvaried. If there is too much feedback and theset oscillates the resistance across the coil isreduced and less current flows through this coiland more through the resistance. If, on theother hand, there is too little regeneration thevalue of the resistance is raised and morecurrent flows through the coil.

The coil winding details for this set are thesame as for the last one, and if desired the samemethod of regeneration may be used. Thesecond stage is stabilised in the conventionalway, that is with D.C. feedback applied by aresistance in the emitter lead. The last stage,however, is stabilised by means of a feedbackresistor. As this resistor feeds back A.C. aswell as D.C. there is some loss of gain, but thismay be overcome by splitting the resistanceinto two halves, each of 15 ko and shortingthe junction of the two halves to earth (as faras A.C. is concerned) via a 6 mfd. electrolytic.

If desired, a small loudspeaker may be usedwith the set ; the transformer for this shouldhave a turns ratio of about 18 : 1 if it is tofeed into a 3 ohm loudspeaker.

CIRCUIT 21

Wrist radios have long been featured inscience fiction and comic strips, but it was onlythe advent of the transistor that made thedesign of such sets possible. This remarkablysimple receiver was originally designed byLieut. Paul Cooper and Joseph O'Brien of theAmerican Signal Corps Engineering Labora-tory.

According to the designers, the set is tune-able from 1 Mc/s to 1.6 Mc/s and hasthe remarkably high sensitivity of 50 microvolts.

The first stage acts as a common baseregenerative R.F. amplifier with the regenera-

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tion controlled by the 2 hi potentiometer inthe collector lead.

In strong signal areas no aerial is needed,sufficient signal being picked up by the coilsthemselves, but normally a foot or so of wireis required. If the set is built as a wrist radiothen the aerial may be wound on to or in thestrap ; there would then be a capacitativecoupling between the wearer and the tuningcoil of the receiver so that, in effect, the owner'sbody acts as an aerial.

The amount of regeneration obtained de-pends somewhat upon the position of the tuningcondenser, so the regeneration control shouldbe readjusted each time a station is tuned in.

The original receiver used a point -contacttype of transistor for the first stage, but if aP.N.P.-R.F. junction type of transistor is usedthe supply voltage may be reduced to 1.3 or1.5 volts.

CIRCUIT 22

The main disadvantage of using a transistorin the common -emitter mode at high fre-quencies is that the maximum frequency ofoperation of the transistor is not obtainable.For example, the Mullard 0C44 has a fre-quency cutoff of 15 Mc/s, which means thatwhen used in the common -base mode the gainat 15 Mc/s is 3dB below the gain at 1 kc/s,and with careful design the transistor willoperate as a common -base amplifier up to thisfrequency. In the common -emitter mode,however, the position is far less satisfactory,the cutoff point being reached at approximatelythe alpha frequency cutoff divided by the betacurrent gain. With the 0C44, the beta currentgain has a value of approximately 100, thusthe cutoff is reached at 0.15 Mc/s or 150 kc/s.The transistor will, however, operate at reducedgain, somewhat above the cutoff value.

The receiver in circuit 22 takes this intoaccount and is designed to operate at maximumfrequency for any given transistor. The turnson the coil are shown in the diagram formedium wave -band. The coil should be wound

on a ferrite rod aerial about 6 to 8 inches long.If it is desired to use the set on any other wave-band then the appropriate number of turnsmust be used, but maintain the ratio of 6 to 1between the upper and lower halves of the coil.Two methods of controlling the reaction areprovided, the 470 ku base resistance and the50 pf. trimmer. The pot. is first adjusted toobtain roughly the correct setting, and then thetrimmer is adjusted for the final setting.

The first transistor is coupled to V, via aradio frequency choke and the 6 mfd. electro-lytic. The choke ensures that the R.F. is fedback to the tuned circuit and not lost in thenext stage.

V2 feeds into a phase -splitting transformerwhich couples it to the push-pull output stage.The advantages of this type of output areincreased fidelity, output power and batteryeconomy because the current drawn from thebattery is proportional to the input signalinstead of inversely proportional, as is the casein a single -ended output stage.

CIRCUITS 23 AND 24

These two receivers are merely variations onthe preceding sets and they introduce no reallynew ideas. Circuit 24 is interesting, however,because the feedback winding is tuned insteadof the base -emitter winding. The signals arepicked up by the ferrite rod and tuned to L, ;as L, is tightly coupled to L2 only the requiredsignal is amplified and detected by the tran-sistor. As L, is not the tuning coil it may bewound to provide a correct impedance for thetransistor and should have one -sixth the numberof turns that L, has.

In neither of these circuits are the supplyvoltages very important, but it is preferable touse mercury cells as these have far more con-stant voltage with life than the zinc ones have.

CIRCUIT 25

This circuit is analagous to the well-knowntuned-grid-tuned anode valve oscillator. Withtransistors this is known as a tuned base -tuned


emitter oscillator. This set is prevented fromoscillating (or allowed to oscillate as the casemay be) by the 500 pfd. variable condenserwhich controls the amount of signal fed to thetransistor.

The first transistor is not a regenerative detec-tor, as were all the others in the section ; it is,in fact, a regenerative R.F. amplifier, thus acrystal diode is required for detection.

This system has several advantages over pre-vious circuits. First, as there are two tunedcircuits instead of one, the selectivity is stillbetter, and secondly, the transistor gives highergain because of the greatly increased collectorimpedance.

After the tuned circuit the receiver followsthe same lines as those in section one, and anyof these circuits may be used instead of the oneshown if desired.

When building this set, considerable caremust be taken to ensure that there is no induc-

tive coupling between the two coils, eithershield them from one another or mount themso that their axes are at right angles. The twotuning condensers should be ganged togetherand the set must be aligned in the same waythat is used in valve circuits. For this purpose,trimming condensers must be connected inparallel with the tuning condenser.

CIRCUIT 26

Circuit 26 is an example of the shunt -fedHartley type of circuit being applied to a tran-sistor receiver. In this circuit the tickler coilis in series with the coil feeding into the tran-sistor and a single coil with a tap take the placeof two separate coils. The coil thus functionsas an auto -transformer. The amount of feed-back will depend, not only on the setting ofthe feed -back condenser, but also on the posi-tion of the tapping. The nearer the tapping to

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The advantage of using the shunt -fed Hartleyrather than the more usual series -fed Hartleyis that the R.F. feedback does not have to passthrough the battery and is thus independent ofthe battery's resistance.

It is not necessary that the two halves of thecoil should be inductively coupled as they arecapacitively coupled by the 500 pfd. tuningcondenser ; however, in practice there is boundto be some inductive coupling as the two halvesof the coil will be wound on the same former.It is worthwhile experimenting with the posi-tion of the tap, but it should be approximatelya quarter of the way from the base end of thecoil.

CIRCUIT 27

This receiver is unlike all the others shownin this respect, it has no feedback coil. Asecond transistor does the job instead.

A transistor used in the common emitterconfiguration inverts the signal between its baseand collector. That is, the output is 180° outof phase with the input. Thus, if there is somedirect feedback from the collector to the base,this will be negative feedback instead of thepositive feedback required for regeneration.Normally this difficulty is overcome by invert-ing the signal on its way back with a coil.However, a second transistor may be usedinstead with very good results, the advantagebeing that control of the reaction has little orno effect on the tuning.

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The first transistor amplifies part of the R.F.and detects the rest passing the resultant ampli-fied A.F. on to V, via the R.F. choke. TheR.F., however, is prevented from reaching V,by this R.F. choke and is fed to V,, where it isinverted and fed back to the base of V1 viathe 15 pfd. trimmer. It may be necessary toalter the maximum value of this trimmer tobring the transistor to its most sensitive point.No definite value can be laid down because ofthe variations in transistors.

V1 and V, must both be R.F. transistorshaving an alpha cutoff value of at least 10Mc/s. V, and V, may be any P.N.P. tran-sistors.

The output transformer should have a turnsratio of about 18 : 1 if it is to feed into anormal 3 ohm loudspeaker, but this value isnot particularly critical.

CIRCUITS 28 AND 29

This receiver and the variation of it shownin circuit 29 was developed by Mullards Ltd.

Circuit 28 is a single station pre -tunedreceiver designed to tune in the Light Pro-gramme on the long wave. As R.F. transistorsare still somewhat expensive, this set is moreeconomical than usual, using, as it does, onlyan A.F. transistor in the R.F. section.

The first stage is a common base regenerativedetector which detects the R.F. signal and pro-vides R.F. positive feedback which reduces thedamping of the tuned circuit and thus enablesthe transistor to achieve high gain. R, and R,provide the base bias and, together with R2,D.C. stabilise the transistor.

Maximum sensitivity is achieved when thereceiver is near the point of oscillation withoutinstability. This was taken into considerationwhen the receiver was designed.

The first stage is coupled to the second bymeans of an 8.5 : 1 step-down transformer.The gain of the output stage is increased bymeans of A.F. positive feedback.

Circuit 29 is merely the front end of circuit28 feeding into the Mullard 6V, 200 milliwattsamplifier. With this combination a first-classpocket receiver can be built capable of sufficientoutput to fill a fair-sized room.

...

Valve and Television Tube

Equivalents ManualBy B. BABANI

The only up-to-date and complete publication giving details of more than 12,500valves with all their equivalents covering receiving and transmitting types, Army,Navy and Air Force types and all Television tubes and their equivalents.

Completely cross indexed for easy use. The only publication which includes allBritish, French, German, Italian, other Continental and American types. An essen-tial work of reference for every home constructor, radio amateur, service engineerand technician in any branch of the electronic industry.

No. 144 10" x 7k" PRICE 5s.


SECTION III

T.R.F. RECEIVERS

The tuned radio frequency receiver, usingvalves, has been, perhaps, the most populartype with the more advanced constructor eversince the principle was first discovered, and itwould seem natural that this should also betrue with transistors. This, however, is by nomeans so. Present-day R.F. transistors haveless gain than their valve counterparts and somore R.F. stages are required for equivalent

sensitivity which, in turn, means more variablytuned stages to complicate the alignment.Furthermore, the transistors presently availableare all triodes and therefore require neutralisa-tion if used in the common emitter configura-tion. (The common base configuration pro-vides less gain and still more stages arenecessary to obtain a satisfactory degree ofsensitivity.)

R.F. TUNEDCIRCUIT

R.F.R.F.

AMPLIFIER

R.F. TUNEDCIRCUIT

R.F.

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Fig.3.

36 PRACTICAL TRANSISTOR RECEIVERSFor these reasons the author has not devoted

more space than is necessary for comprehen-siveness to T.R.F.s. The types of circuit usedin R.F. amplifiers are, of course, the same asthose for I.F. amplifiers, and examples of theseare shown in Section 5.

The block diagram for these sets is shown inFig. 3. The difference between these receiversand those shown in Section 1 is that the signalis amplified before it reaches the detector, witha resultant increase in sensitivity. As there areseveral tuned circuits the selectivity is normallyvery good.

CIRCUIT 30

This little receiver is perfectly straight-forward. V, acts as a R.F. amplifier withoutany D.C. stabilisation. The 50 pf. trimmer isused to provide neutralisation, that is to neu-

tralise the internal feedback which is due tothe internal capacitances of the transistor.

To avoid feedback between the coils, bymutual inductance, they should be separatedfrom one another as much as the case permits.If a very small case is used it may be necessaryto use a metal screen and to mount the coilsso that their axes are at right angles to oneanother.

If high quality loudspeaker operation isrequired the crystal diode may be followed bya three -stage audio amplifier with push-pulloutput.

The set, as shown, will work with only aferrite rod aerial in almost any area. Thesecondary of this coil should be about 15 turnsof fairly thick insulated wire wound alongsidethe tuned winding. A metal case must not beused, as this would shield the ferrite and pre-vent any signal pick-up.

Circuit. 30.

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CIRCUIT 31

This receiver is similar to that shown incircuit 30. The main difference is the inclu-sion of D.C. stabilisation in the R.F. stage. Asthe coils for this and the last set are identical,circuit 30 may easily be converted to circuit 31.As has been mentioned before, the type ofaudio amplifier used is entirely up to the con-structor, and if circuit 30 is converted theoriginal amplifier may be retained.

A transistor having an alpha cutoff of atleast 6 Mc/s must be used for the first stage,as this uses a common emitter amplifier.

CIRCUIT 32

This ingenious circuit, which has been usedin slightly modified form by kit suppliers inGreat Britain and America, is capable of goodloudspeaker operation with only a ferrite rod

aerial, and yet it uses only two transistors anda single tuning condenser.

The set is a four -stage receiver, V, being areflex stage amplifying at both R.F. and A.F.without regeneration.

The signal is picked up by the ferrite rod,tuned by L, and the 400 pf. capacitor andcoupled to V, by L2. V, then amplifies theR.F. signal. The amplified R.F. is blocked byL3 and passed by C5 to the diode detector.The resultant A.F. is developed across the 5 k1potentiometer, R8. R8 serves as a volume con-trol, the output being fed back to V, via C,0which has a value of 5 or 6 mfd. V, thenamplifies the signal gain, this time at A.F. L3

offers a low impedance to the A.F. output,being an R.F. choke which should have a valueof approximately 1 mh. The small amount ofsignal that does bypass C, is prevented fromreaching the diode by L, which offers a lowimpedance path to earth.

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PRACTICAL TRANSISTOR RECEIVERS

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The output from V, is fed to V2, the audiooutput stage, which is transformer coupled tothe loudspeaker. The output transformershould have a turns ratio of about 80 to 1 asit must match the 20 ku output from thetransistor to the 3 ohm voice coil of thespeaker.

Despite its apparent complexity, this is anideal receiver for the inexperienced constructor

as there is no reaction to control and no align-ment problems. The only disadvantage is thesignal tuned circuit, which makes the tuningsomewhat broader than would normally bedesired.

In difficult areas, it may be necessary to addan earth and an aerial of between 10 and 15feet.

INTERNATIONAL RADIO TUBE

ENCYCLOP/EDIATHIRD EDITION 1958-9

By BERNARD B. BABANI

Now High GradeLibrary ClothAvailable Binding

The Encyclopa-dia contains data on more than 27,500 tubes of all types includingdiodes, triodes, tetrodes, pentodes, heptodes, hexodes, tuning indicators, regulators,thyratrons, rectifiers, sub -miniature tubes, T.V. cathode ray tubes, industrial andmilitary type transmitting triodes, tetrodes, pentodes, cathode ray tubes, klystrons,magnetrons, T.R. tubes, A.T.R. tubes, co -axial velocity modulators, travellingwave tubes, pulse -gas switching tubes, noise sources, microwave oscillators, reflexvelocity oscillators, cavity tubes, pre T.R. tubes, counter tubes, forward waveamplifiers, magnet focused amplifiers, continuous wave amplifiers, frequency multi-pliers, etc., that are manufactured in the major countries of the world, such as,Great Britain, U.S.A., France, Germany, Italy, Holland, Switzerland, Poland,Czechoslovakia, Belgium, Japan, South Americas, Australia, Spain, Canada,U.S.S.R., etc.

In order to increase the value and use of this third edition to the maximum thesection containing the technical matter and instructions for using the data tableshas been translated by native technicians into the following 14 languages inaddition to English:-

CZECH HEBREW RUSSIANDANISH ITALIAN SPANISHDUTCH NORWEGIAN SWEDISHFRENCH POLISH TURKISHGERMAN PORTUGUESE

SIZE 10" x 7k" PRICE 63S. 768 PAGES


SECTION IV

SUPER REGENERATIVE RECEIVERS

The super regenerative receiver is the mostsensitive type ever designed. Furthermore, ithas the advantages of single tuning, basic sim-plicity, economy and reasonably high fidelity(this last point depends upon the type of superregen. used). It would appear at first sightthat this is then the ideal circuit, and yet ithas never achieved the widespread popularityit deserves, and is very rarely used in any

commercial equipment. The reasons for thisdo not really lie in the circuit, but in the peoplewho first tried to use it without really under-standing it sufficiently. The result of this wasthat the super regen. earned itself a name for atendency to oscillate and be uncontrollable. Itwas thought far to unstable to ever be used inany really good mass-produced equipment.However, during the last war the super regen.

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at last came into its own as it was used in radarand I.F.F. receivers with first-class results. Forany given valve or transistor, a super regen.may be designed to operate at a far higher fre-quency than with any other circuit. Thismakes it especially useful with transistors as itis vastly more economical than, say, a superhetwith comparable performance.

The super regen. is really a development ofthe regenerative receiver. The sensitivity of thelatter is limited by the point at which it burstsinto oscillation. The super regen. consists of aregen. R.F. amplifier or detector which is ad-justed so as to be near the point of oscillation.The detector may now be switched in and outof oscillation by varying any of the supplycurrents a small amount. In operation thistransistor or valve is switched in and out ofoperation at supersonic rate by anotheroscillator which is designed to vary either thebase or the collector bias and is known as thequench oscillator.

Now, the R.F. oscillations may start fromany level but will always build up to the samepeak value (this value being the limit that thetransistor used can handle). The time it takesthe oscillations to build up to their peak willdepend on the amplitude of the modulatedsignal picked up by the aerial, then the varia-tion in the start to peak oscillation times willbe, in some way, proportional to the originalmodulation signal.

If the oscillations are always allowed to reachtheir peak before being quenched, then theoutput will be logarithmically proportional tothe input and not really suitable for the recep-tion of words or music. If, however, theoscillations are always quenched before theyreach their peak then the output will be linearlyproportional to the input. The gain achievedin this way may be 100 million times for asingle stage.

Whether the set operates in the linear orlogarithmic mode depends upon the amplitudeand frequency of the quench oscillator, and sothe adjustment for this is somewhat critical.

The oscillations induced by one quench cyclemust always die away before the next cyclecommences. If this does not happen then thenext cycle will build up from the cycle beforeand not from the signal. For this and otherreasons the wavelength of the quench oscillatorshould normally be at least 100 times that ofthe signal frequency oscillator. This makes thedesign of a medium wave super regen. ex-tremely difficult. It is not, however, impossible,as is so often stated, and very good results havebeen obtained from the circuits shown in thissection.

Although the quench oscillation is often aseparate transistor it is possible to make thesuper regenerative detector supply its ownquench frequency, and some of the receiversare of this type. The operation of a self -quenched super regen. detector is somewhatdifferent from that of the other types mentionedabove. In this case the bursts of oscillationmaintain the same amplitude, but the timebetween each one varies as the input signalvaries.

Owing to this somewhat complex mode ofoperation, the reader is not advised to attemptthe construction of a super regen. until he orshe has built some of the circuits in Sections1 and 2.

CIRCUIT 33(Based on American Patent No. 2,821,625).

This rather unusual and original receiver isdesigned to operate on the medium waveband.As has already been mentioned, the design ofa satisfactory broadcast band super regen. is byno means simple. The quench frequency hasto be kept to a minimum to give the oscillationstime to build up and decay in each cycle ;furthermore, the quench frequency must notencroach upon the medium waveband.

In this circuit V, is the quench oscillator andoperates approximately at 10 kc/s, which isjust at the limit of most people's hearing range.This oscillator is a capacitatively tappedcolpitts and the frequency may be adjusted by

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varying the values of the two condensers inparallel with the choke. If any adjustment ismade it should be slight and both condensersshould be adjusted to the same extent.

V2 is the super regen. detector. This is per-manently adjusted so as to be almost on thepoint of oscillation by varying the couplingbetween L, and L,, L, and L, are allwound on a ferrite rod and should have ap-proximately 80, 15 and 20 turns respectively.As the transistor is just on the point of oscilla-tion a slight variation of the base bias will alterthe gain of the transistor and bring it either inor out of oscillation. But the base of V2 iscoupled to the quench oscillator, V,, and soV2 super regenerates. There is nothing unusualabout the design of this second stage and almostany regenerative detector, shown in Section 2,would serve equally well.

The output from V, is transformer -coupledto the audio amplifier. For the sake of sim-plicity only one stage of audio amplification hasbeen shown, and in most cases this will beinsufficient to drive the loudspeaker to a satis-factory volume ; however, any audio amplifiermay be used, either valve or transistor.

When constructing this set, keep the coils,transformers and choke as far apart as possibleto avoid interaction. As there are three dif-ferent frequencies at any one moment, inter-action is liable to cause disastrous instabilityand distortion, so the receiver is really unsuit-able for miniaturisation ; however, with suitablescreening it could be made small enough to slipin a pocket.

As this receiver oscillates at signal fre-quencies during operation no aerial should beused. The danger of causing interference withneighbouring receivers is, however, very small,because of the amplitude at which the transistorconcerned operates.

CIRCUIT 34(Based on American Patent No. 2,751,497).

Unlike the last circuit, this receiver uses noseparate quench frequency oscillator.

V, acts as both super regenerative andquench oscillator. L, and L, are identical coilswound on top of one another on an adjustablecore which is used to vary the tuning. Whenthe connections to L2 are correct the transistoroscillates at signal frequency. These oscilla-tions are rectified by the base emitter junctionof V, and the resultant D.C. charges C, viathe 170 ohm resistance. Eventually sufficientcharge is developed to bias the transistor insuch a way as to prevent further oscillation.The charge then leaks away via the resistanceuntil oscillation recommences and the cyclebegins again. The wave form of this oscilla-tion is approximately sawtooth and, withproperly chosen values, occurs at a supersonicrate.

A short aerial of only a few feet of wire mustbe used but because of the receiver's high gain.this is no disadvantage.

In order to achieve maximum gain, a highfrequency cutoff R.F. transistor has been usedin the common emitter mode. Because of thevariation in transistors it may be necessary toalter the values of R3 and C, for proper opera-tion.

The audio output of V, is amplified by V2and V3 and transformer coupled to the loud-speaker. With only the three transistors usedin this circuit the audio output of the set issimilar to that of the small 5 transistor super-hets-now on the market in this country and,although the selectivity is definitely inferiorfrom a theoretical point of view, in practiceonly one station is heard at any time as thesuper regen. oscillations always build up fromthe strongest signal passed on by the tunedcircuit. In the absence of any signal, a' shushing ' noise is normally heard from thespeaker. This illustrates the fantastic amplify-ing capabilities of the super regen. as itoriginates from the random motion of electronsin the first parts of the circuit.

As this set does not use a choke in thequenching circuit, it may be made far smallerthan the last one without fear of instability.

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CIRCUIT 35

This circuit and the two that follow it makeuse of surface barrier transistors for their superregenerative detectors.

Surface barrier transistors are manufacturedin England by Semiconductors Ltd. of Swin-don. The transistors have several considerableadvantages over the normal junction type oftransistor. They have a far higher cutoff fre-quency and are capable of operation up to,and sometimes above, 60 Mc/s. Furthermore,as they have comparatively low current gainstheir performance in the common emitter con-figuration is vastly superior to other types.Another advantage of the S.B. transistor is itsamazingly low power requirement ; it canoperate well on one -tenth the power requiredby a normal junction type.

The transistor is formed by electrolyticallyetching a thin wafer of germanium, which acts

as the base. After a certain time the currentis reversed and the emitter and collector elec-trodes are plated on.

It must be remembered, when using S.B.transistors, that they operate at very lowvoltages and anything greater than a 4.5 voltbattery will ruin them. The maximum collectorcurrent is 5 ma. and this must also not beexceeded.

This receiver consists of a simple one -transistor super regen. detector followed by theMullard 4.5 volt A.F. amplifier. The 20 kIlvariable resistance controls both the emitterbias and the quench frequency. It should beadjusted for maximum sensitivity. The set isideal for operation on the 28 Mc/s amateurband and, for those who have never used asuper regen. before, the sensitivity is almostincredible.

The letters W, X. Y and Z are for use withthe next set.

V

20.pFL.2. 15.pF

10:1

0-004.C.I. 0.05.

Ts

SB. 344.

R.3. R.2.

Circuit. 36.


CIRCUIT 36A somewhat more complete circuit than the

last is shown in circuit 36. The letters referto connections to the amplifier in the lastcircuit. Any other amplifier may be used pro-viding that it has sufficient gain.

For 30 Mc/s operation, L, should be 7 turnsof 22 -gauge wire space -wound to a length of

inches on a 1 -inch former. L, should be2 turns of the same wire, wound close to thecollector end of L, and L3 should consist of3 turns wound the opposite end of L2.

R, varies the amount of regeneration appliedand is adjusted for maximum sensitivity. Itshould be readjusted for each station. R.,

varies the quench frequency and should alsobe adjusted for maximum sensitivity, but onceset may be left alone. In some cases changing

the value of C, may improve the performance,but the value ought to be between 0.015 and0.1 ilfd.

The quench oscillations are controlled by CT2 and T3. Initially the transistor oscillates atthe frequency of the tuned circuit. Theemitter -base diode rectifies this R.F. currentand charges C, via the feedback winding of thecoil. Eventually the charge on C, becomesgreat enough to prevent the transistor fromoscillating any further and the charge begins toleak away through R2 and As the chargeon the condenser drops, the bias on the emitterreturns to its original value and the transistorbegins to oscillate again.

Using only a 4 -yard aerial and no earth,amateurs have been picked up from a distanceof 2,000 miles.

NEW BERNARDS BOOKS TO BEPUBLISHED IN 1959

PRACTICAL RADIO INSIDE OUT. No. 150. Price 3s. 6d.This book describes all the types of components commonly used in radio and televisionreceivers. Complete and practical circuit diagrams are given for various pieces of test equip-ment and the methods of using the equipment to evaluate the performance of any component

PRACTICAL STEREO HANDBOOK. No. 149. Price 3s. 6d.This is the book that every audiophile and home constructor has been waiting for. It dealswith every aspect of stereo and explains the advantages and disadvantages of the variousmethods of reproduction. A large number of practical stereophonic amplifier circuits are giventogether with full constructional details.

PRACTICAL TRANSISTOR RECEIVERS. Book H. Price 5s.This is the continuation of the book you have just read and is presented in the same style.The receivers described are all superhets but superhets with a difference. An amazing numberof different types are shown ranging from a tiny single transistor superhet to a full blowneight transistor car radio with four watts output.

SHORTWAVE CONSTRUCTORS MANUAL. Price 3s. 6d.There has long been a demand for a really up to date book dealing with practical receiversand equipment for the shortwave enthusiast. This is it. Special emphasis is placed onsimplicity of construction in all circuits described but absolutely no sacrifice of performanceis made.

CAR RADIO FOLDER.Bernard's are putting themselves to the front as usual with this up to the minute folder. Itmakes use of the amazing new Mullard 12v valves and the high power 0C16 to enable extrahigh performance and amazingly low consumption.

SUB -MINIATURE RECEIVERS MANUAL. Price 5s.Multum in Parvo could well be the title of this manual which we hope to have ready forthe 1959 Radio Show. If suitable transistors are available by this time we will include theworld's first pocket F.M. receiver complete with loudspeaker.


BRITISH TRANSISTORS

This list of current British transistors hasbeen compiled to enable the reader to rapidlycheck the characteristics of any transistors hemay have or obtain. In some cases it is impos-sible, as yet, to obtain these transistors on theretail market ; however, most firms are willingto supply them directly through the post. Thereader is advised to write to the firm concerned

to ensure that they are willing to do this beforehe sends his order.

This is by no means a complete list of tran-sistors manufactured in this country, as thereare many special types made only for industrialuse, such as in computers, and it was notthought worthwhile to include these.

Number Powerand OutputType (MW)

EDISWAN MAZDA

VC.Max.(volts)

lc. Max.(mA)

Beta Alpha cutoff Notes and Comments

XA101 90 16 - 35 5 N4c/s Low gain R.F. transistor.(P.N.P.)XA102 90 16 - 60 8 Mc/s High gain R.F. transistor.(P.N.P.)XB102 90 16 - 30(P.N.P.)XB103 90 16 - 66(P.N.P.)XC101 165 16 66(P.N.P.)

MULLARD

0C16 6,250 32 1,500 45 .2 Mc/s Very high power transistor.(P.N.P.)0C44 20 10 5 100 15 Mc/s Good high frequency resistor.(P.N.P.)0C45(P.N.P.)

20 10 5 50 6 Mc/s High frequency transistor de-signed mainly for use in I.F.amplifiers.

0065(P.N.P.)

25 5 10 20-40 Subminiature transistor de-signed for use in hearingaids (similar 0070).

0066(P.N.P.)

25 15 10 30-80 Subminiature transistor de-signed for use in hearingaids (similar 0071).

0070(P.N.P.)

50 20 10 20-40 Low noise A.F. transistor de-signed for first stages of anyA.F. amplifier.


NumberandType

Power VC, lc. Max. Beta Alpha cutojjOutput Max. (mA)(MW) (volts)

0071 50 20 10 30-76(P.N.P.)0072 100 32 125 70 350 kc/s2-0072(P.N.P.)0073(P.N.P.)0076(P.N.P.)0077(P.N.P.)

50 30 10

75 32 125

75 60 125

BRIM AR (STC)TS7(P.N.P.)TS8(P.N.P.)TS13(P.N.P.)TS14(P.N.P.)TS15(P.N.P.)

B.T.H.GT1(P.N.P.)GT2(P.N.P.)GT3(P.N.P.)GT11(P.N.P.)GT12(P.N.P.)GT13(P.N.P.)

G.E.C.GET3(P.N.P.)GET4(P.N.P.)GETS(P.N.P.)GET6(P.N.P.)GET15(P.N.P.)GET16(P.N.P.)GET20(P.N.P.)

30-65

715

45

70 12 - 35 4.5 Mc/s

70 6 - 60 8.5 Mc/s

70 20 55 800 kc/s

70 20 - 35 700 kc/s

70 45 - 40 750 kc/s

125 9

125 9

125 9

100 9

100 9

100 9

20

40

60

30

60

100

800 kc/s

900 kc/s

1 Mc/s

4 Me/s

6 Mc/s

9 Mc/s

100 15 250 55 1 Mc/s

50 30 70 50 1 Mc/s

200 30 350 1 Mc/s

50 12 50 50 1 Mc/s

600 15 350 70 .95 Me/s

600 30 350 60 .9 Mc/s

600 30 500 60 1 Mc/s

Notes and Comments

A.F. transistor designed foruse in A.F. amplifiers.

High gain transistor availablein matched pairs for push-pull output.

A.F. transistor.

Medium power A.F. tran-sistor.

High voltage, medium powertransistor.

Bidirectional R.F. transistor.

Bidirectional R.F. transistor.

Good A.F. transistor.

Low gain A.F. transistor.

Medium gain A.F. transistor.

Subminiaturetransistor.

SubminiatureA.F. transis

Subminiaturetransistor.

Subminiature

low gain A.F.

medium gaintor.high gain A.F.

R.F. transistor.

Subminiature R.F. transistor.

Subminiature R.F. transistor.

Medium gain output tran-sistor.

Medium gain A.F. transistor.

Medium power transistor.

Low power A.F. transistor.

High gain power transistor.

High gain, high voltage powertransistor.

High gain, high voltage powertransistor.

50

NumberandType

HIVAC

XFT2(P.N.P.)


Power VC. ic. Max. Beta Alpha cutoff Notes and ContinentsOutput Max. (mA)(MW) (volts)

50 12 10 49 460 kc/s Subminiature medium gaintransistor designed for hear-ing aids.

NEWMARKET-PYE

V10/15A 100 10 30 20 16 Mc/s Low gain A.F. transistor.(P.N.P.)V10/30A 100 10 30 40 .7 McIs Medium gain A.F. transistor.(P.N.P.)V10/50B 100 10 30 75 1.2 Mc/s High gain A.F. transistor.(P.N.P.)V6/R2 25 6 12 25 3 Mc/s Low gain R.F. transistor.(P.N.P.)V6/R4 25 6 12 50 5.5 Mc/s Medium gain R.F. transistor.(P.N.P.)V6/R8 25 6 12 80 10 Mc/s High gain R.F. transistor.(P.N.P.)V15/10P(P.N.P.)

10,000 15 3,000 18 Low gain, high power trati-sistor.

V15/20P(P.N.P.)

10,000 15 3,000 24 Low gain, high power tran-sistor.

V15/30P(P.N.P.)

10,000 15 3,000 38 Medium gain, high powertransistor.

V30 /10P(P.N.P.)


V30/20P(P.N.P.)


V30/30P(P.N.P.)

10,000 30 3,000 38 Medium gain, high powertransistor.

SEMICONDUCTORS

SB344(P.N.P.)

20 5 5 11-33 50 Mc/s Surface barrier transistor foruse at high frequencies.

SB345fP.N.P.)

20 5 5 25-110 50 Mc/s Surface barrier transistor foruse at high frequencies.

SB346(P.N.P.)

20 5 5 10 min. 75 Mc/s Surface barrier transistor foruse at high frequencies.

2N128(P.N.P.)

30 10 5 65 Mc/s Surface barrier transistor foruse at high frequencies.

2N129(P.N.P.)

30 10 5 65 Mc/s Surface barrier transistor foruse at high frequencies.

2N240(P.N.P.)

10 6 15 16 30 Mc/s Surface barrier transistor foruse at high frequencies.

2N293 50 6 50 60 Mc/s Micro -alloy transistor.(P.N.P.)


AMERICAN TRANSISTORS

Plumber Powerand Max.Type (MW)

CBS-HYTRON

VC.(volts)

lc.(mA)

Beta Alpha cutoff

3N38A 50 20 8 18

(P.N.P.)2N80 20 25 2 80(P.N.P.)2N82 35 20 15 60(P.N.P.)2N108 50 20 15

(P.N.P.)2N116 50 20 8 18

(P.N.P.)HA 1 & HA8 50 20 8 40(P.N.P.)HA2 & HA9 50 20 8 30(P.N.P.)HA3 & HA10 50 20 12 35(P.N.P.)HD197 500 40 10 150 kc/s(P.N.P.)

GENERAL TRANSISTOR CORP.

2N63 33 22 10 22 .8 kc/s(P.N.P.)2N64 33 22 10 45 .8 kc/s(P.N.P.)2N65 33 22 10 90 .8 kc/s(P.N.P.)GT14 70 25 28(P.N.P.)QT20 70 25 45(P.N.P.)GT24 40 6 45(P.N.P.)GT34 70 25 15

(P.N.P.)GT38 40 6(P.N.P.)CIT81 70 25 65(P.N.P.)GT81h 40 6 90(P.N.P.)

Notes and Comments

Audio transistor designed foruse in hearing aids.

Audio transistor designed foruse at high temperatures.

Audio transistor designed foruse at high temperatures.

Audio transistor designed foruse in output stages.

Low noise audio transistor.

Audio transistoruse in hearing



Medium powersistor.

General purposesistor.







Audio transistorhearing aids.

Audio transistor.

Audio transistorhearing aids.

designed foraids.designed foraids.designed foraids.audio tran-

audio

audio

audio

audio

audio

tran-

tran-

tran-

tran-

tran-

designed foraids.audio tran-

for use in

for use in


Number Power VC. lc. Beta Alpha cutoff Notes and Commentsand Max. (volts) (mA)Type (MW)

GENERAL ELECTRIC2N43 150 45 50 1 Mc/s High gain A.F. amplifier.(P.N.P.)2N43A 150 45 50 - 1 Mc/s Medium power transistor.(P.N.P.)2N44 150 45 50 - 1 Mc/s Medium power transistor.(P.N.P.)2N45 150 45 50 - 1 Mc/s Medium power transistor.(P.N.P.)2N76(P.N.P.)

20 10 - 1 Mc/s General purpose audio ampli-fier.

2N78(P.N.P.)

50 15 20 - 4 Mc/s General purpose R.F. tran-sistor.

2N123(P.N.P.)

75 20 20 - 6.5 Mc/s General purpose R.F. tran-sistor.

PHILCO2N47(P.N.P.)

50 35 20 .8 Mc/s A.F. transistor designed foruse in hearing aids.

2N49 50 35 20 - .8 Mc/s Low noise audio transistor.(P.N.P.)RCA2N77 35 25 15 55 .7 Mc/s Low power A.F. transistor.(P.N.P.)2N104 150 30 50 44 .7 Mc/s Low power A.F. transistor.(P.N.P.)2N105 35 25 15 55 .15 Mc/s Low power A.F. transistor.(P.N.P.)2N109(P.N.P.)

50 20 50 70 - Medium power A.F. tran-sistor.

RAYTHEONCK721(P.N.P.)

180 15 10 45 .8 Mc/s General purpose A.F. tran-sistor.

CK722(P.N.P.)

180 22 10 22 .7 Mc/s General purpose A.F. tran-sistor.

CK725 180 12 10 90 .9 Mc/s High gain A.F. transistor.(P.N.P.)CK727 180 6 10 25 .8 Mc/s Low noise A.F. transistor.(P.N.P.)2N63 100 22 10 22 .7 Mc/s General purpose transistor_(P.N.P.)2N64 100 15 10 45 .8 Mc/s General purpose transistor.(P.N.P.)2N65 100 12 10 90 .9 Mc/s High gain A.F. transistor,.(P.N.P.)2N106 100 6 10 25 .8 Mc/s Low noise A.F. transistor.(P.N.P.)2N112 100 6 5 40 5 Mc/s High frequency transistor..(P.N.P.)2N113 100 6 5 45 10 Mc/s High frequency transistor.(P.N.P.)2N114 100 6 5 65 20 Mc/s High frequency transistor.(P.N.P.)

NumberandType

SYLVANIA2N34(P.N.P.)2N35(N.P.N.)


Power VC.Max. (volts)(MW)

50 25

50 25

TEXAS INSTRUMENTS200(N.P.N.)201(N.P.N.)202(N.P.N.)210(N.P.N.)220(N.P.N.)221(N.P.N.)222(N.P.N.)223(N.P.N.)300(P.N.P.)301(P.N.P.)350(P.N.P.)

50 30

50 30

50 30

50 30

50

50

50

50

50

50

50

X-2 350(N.P.N.)903 75(N.P.N.)904 75(N.P.N.)905 75(N.P.N.)904A 75(N. P.N.)700 50(N.P.N.)

TRANSITRON2N34 125(P.N.P.)2N36 125(P.N.P.)2N37 125(P.N.P.)2N38 125(P.N.P.)

30

30

30

30

30

30

30

35

30

30

30

30

30

5

5

5

5

5

5

5

5

10

10

75

10

10

10

10

k. Beta Alpha cutoff(mA)

8 40 .6 Mc/s

8 40 .8 Mc/s

9 .9 Mc/s

19 1.1 Mc/s

49 1.3 Mc/s

9

19

25 20 55

25 20 60

25 20 35

25 20 22

3 Mc/s

3 Mc/s

3 Mc/s

8 Mc/s

.8 Mc/s

.8 Mc/s

.6 Mc/s

.5 Mc/s

Notes and Comments

A.F. amplifying transistor.

Similar to above, but withreversed polarity. Usefulfor comp. symmetry circuits.

Low gain A.F. amplifier.

Low gain A.F. amplifier.

Medium gain A.F. amplifier.

Audio amplifying transistor.

I.F. amplifying transistor.



Osc. Musier transistor.



A.F. transistor available inmatched pairs for push-pulloutput.

Medium power transistor.

High gain transistor for smallsignals.

High gain transistor for smallsignals.

High gain, small signal tran-sistor.

High gain, small signal tran-sistor.

Tetrode transistor designed foruse in A.V.C. circuits.

High gain audio amplifier.

High gain audio amplifier.

Medium gain audio amplifier.

General purpose audio ampli-fier.

54

Numberand

Type


Power VC. k. Beta Alpha cutoff Notes and CommentsMax. (volts) (mA)(MW)

2N43 375 45 50 50 .7 Mc/s High gain audio amplifier.(P.N.P.)2N44 375 45 50 22 .5 Mc/s Medium gain audio amplifier.(P.N.P.)2N45(P.N.P.)

375 45 50 19 .4 Mc/s General purpose audio ampli-fier.

2N63(P.N.P.)


2N64 125 25 20 45 .7 Mc/s Medium gain audio amplifier.(P.N.P.)2N65 125 25 20 90 1 Mc/s High gain audio amplifier.(P.N.P.)2N76(P.N.P.)


2N85(P.N.P.)

750 45 100 45 .8 Mc/s Medium power audio ampli-fier.

2N86(P.N.P.)


2N87(P.N.P.)


2N88 25 12 10 35 .5 Mc/s Subminiature audio amplifier.(P.N.P.)2N89 25 12 10 35 .5 Mc/s Subminiature audio amplifier.(P.N.P.)2N90 25 12 10 50 .5 Mc/s Subminiature audio amplifier.(P.N.P.)2N83 10,000 45 1 amp 20 .2 Mc/s Tetrode transistor.(P.N.P.)2N84 10,000 30 1 amp 20 .2 Mc/s Tetrode transistor.(P.N.P.)

TUNG-SOLI)R126(P.N.P.)

50 10 8 25 A.F. transistor designed foruse in hearing aids.

DR128(P.N.P.)

50 10 8 40 A.F. transistor designed foruse in hearing aids.

DR129(P.N.P.)

50 25 8 33 .9 Mc/s General purpose, low gain,A.F. transistor.

DR130(P.N.P.)


DR131(P.N.P.)


DR154 50 25 8 100 .7 Mc/s High gain audio transistor.(P.N.P.)DR155 50 25 8 33 1.4 Mc/s Low R.F. amplifier.(P.N.P.)


INTERNATIONAL EQUIVALENTS LIST OF BRITISH, EUROPEAN AND

AMERICAN SEMI -CONDUCTORS

Types without brackets are direct equivalents.

Types shown in brackets have comparable characteristics, and can be used with themajority of circuits with very minor component value changes.

Type Equivalent Type Type Equivalent Type Type Equivalent Type

N34 (0A85); (1N478) 1N127 (0A95); (1N618) 2N86 (0072)

N34A (0A85); (1N478) 1N128 (0A95); (1N618) 2N87 (0072)

N38 (0A85): (1N478) 1N135 (0A85); (1N478) 2N88 (0065); (0066)

N38A/B (0A85); (1N478) 1N191 (0A86); (1N480) 2N89 (0065); (0066)

N43 (0A85); (1N478) 1N192 (0A87); (1N490) 2N90 (0065); (0066)

N44N45N46N47N48N50N51N52N54N 54AN57

(0A85); (1N478)(0A85); (1N478)(0A85); (1N478)(0A85); (1N478)(0A85); (1N478)(0A85); (1N478)(0A85); (1N478)(0A85); (1N478)(0A85); (1N478)(0A85); (1N478)(0A85); (1N478)

1N1981N2701N2771N2951N4761 N4781N4801N4901N5411N5421N616

(0A95); (1N618)(0A5)(0A5)(0A70)0A81; 1N4760A85; 1N4780A86; 1N4800A87; 1N4900A79; 1N5412-0A79; 1N5420A73; 1N616

2N942N94A2N962N1042N1052N1062N1092N1132N1142N1152N116

(0C45)(0C45)(0071)(0071)

(0071)(0072); (2N281)(0C45)(0C44)0C16; 2N115(0065); (0066)

N58N58AN60N61N62N63

(0A85); (1N478)(0A85); (1N478)(0A70); (1N87)(0A85); (1N478)(0A85); (1N478)(OA85). (1N478)

1N6171N6182N272N282N342N34A

0A91; 1N6170A95; 1N618(0071)(0071)(0072)(0072)

2N1232N1302N1312N1322N1332N135

(0076)(0065); (0066)(0065); (0066)(0065); (0066)(0065); (0066)(0C45)

NMN65N66

(0A70); 1N87A)(0A81); (1N476)(0A85); (1N478)

2N362N372N38/A

(0072)(0072)(0072)

2N1362N1372N138

(0C45)(0C44)(0072)

N67/AN68N68A

(0A95); (1N618)(0A85); (1N478)(0A95); (1N618)

2N412N432N43A

(0065); (0066)(0072)(0071)

2N138A2N1392N140

(0072)(0C45)(0C44)

N69 (0A85); (1N478) 2N44 (0072) 2N145 (0C45)

N70 (0A85); (1N478) 2N44A (0072) 2N146 (0C45)

N75 (0A85); (1N478) 2N45 (0072) 2N147 (0C45)

N81 (0A85); (1N478) 2N46 (0065); (0066) 2N155 (0C16)

N86 (0A85); (1N478) 2N47 (0065); (0066) 2N156 (0C16)

N87/A 0A70: 1N87A 2N48 (0065); (0066) 2N158 (0C16)

N88 (0A81); (1N476) 2N49 (0065); (0066) 2N166 (0C45)

N89 (0A85); (0A95) 2N54 (0072) 2N167 (0076)

N90 (0A95); (1N618) 2N55 (0072) 2N168 (OC45)

N95 (0A85); (0A95) 2N56 (0072) 2N168A (0C44)

N99 (0A85); (0A95) 2N62 (0072) 2N169 (0C45)

N111 (0A85); (1N478) 2N63 (0072) 2N169A (0C45)

N112 (0A85); (1N478) 2N64 (0072) 2N170 (0C45)

N113 (0A81); (1N476) 2N65 (0072) 2N172 (0C44)

N114 (0A81); (1N476) 2N76 (0071) 2N173 (0C16)

N115 (0A81); (1N476) 2N77 (0071); (0066) 2N175 (0065); (0066)

N116N117N126

(0A85): (1N478)(0A85); (0A95)(0A95); (1N618)

2N782N792N85

(0C45)(0071)(0072)

2N1762N1802N182

(0C16)(00721(0076)


Typz Equivalent Type Type

2N183 (0076)2N184 (0076)2N185 (0072)2N186 (0072)2N187 (0072)2N188 (0072)2N189 (0072)2N190 (0072)2N191 (0072)2N192 (0072)2N194 (0C44)2N195 (0072)2N196 (0072)2N197 (0072)2N198 (0072)2N199 (0072)2N200 (0071)2N204 (0071)2N205 (0071)GSD 5/2 (0A90)GT14 (0072)GT14H (0065); (0066)GT20 (0072)GT2OH (0065); (0066)GT38 (0071); (0066)GT81 (0072)G T81H (0065); (OG66)GT109 (0072)GT122 (0076)GT2/2 (0071)GT759 (0C45)GT760 (0C45)GT76I (0C45)GT762 (0C44)HAl (0071); (0066)HA2 (0071); (0066)HA3 (0071); (0066)HA8 (0065); (0066)HA9 (0065); (0066)HAIO (0065); (0066)HD2053 (0A85); (1N478)H D2057 0A85) (1N478)HD2060 0A85) (1N478)HD2063 0A85) (1N478)HS3 (0076)HS4 (0076)11 (0072)J2 (0072)J3 (0072)JP1 (0072M550A (0A85)) (1N478)MS 50B (0A85); (1N478)M3100 (0A85); (1N478)MN24 (OC I 6)MN25 (0C16)MN26 (0C16)NU34 (0A85); (1N478)NU38 (0A85); (1N478)NU58 (0A85); (1N478)0A5 OAS0A7 0A70A9 0A90A31 0A310A47 0A47 T34B0A50 0A81; 0A85 T34C0A51 0A81; 0A85 T34D0A52 0A81; 0A85 T34E0A53 0A81; 0A85 T34F0A54 0A81; 0A85 T10400A55 0A81; 0A85 T1041

Equivalent Type

0A81; 0A850A81; 0A850A81; 0A850A700A810A70; 1N87; (0A90)0A810A720A73; 1N6160A81; 0A850A79; 1N5410A81; 1N4760A85; 1N4780A86; 1N4800A87; 1N4900A900A91; 1N6170A95; 1N618(0A81); (0A85)(0A73)(0A70); (1N87)(0A85); (1N478)(0A72)0A2000A2010A2020A2100A2110A214OAP120C16; 2N1150C300C440C45005700580059006500660070; 2N2790071; 2N2800072; 2N281007100750076; 2N28400770C170(0070); (2N279)(0071)(0072); (2N281)(0065); (0066)0071ORP30OR P90(0A81); (1N476)(0A81); (1N476)(0A70); (1N87A)(0A81); (1N476)(0A81); (1N476)(0A81); (1N476)(2-0A79)

0A560A570A580 A600A610A700 A710A720A730A740A790A810A850A860A870A900A910A950A1500A1590A1600A1610A1720A2000A2010A2020A2100A2110A214OAP120C160C300C440C450057005800590065006600700071OC 7200730075007600770C17000601006020060400624OCP70ORP30ORP90RL3 IRL32RL41RL43RL44RL143RL231RL232/B (2-0A79)T34A (0065); (0066)

(0065); (0066)(0065); (0066)(0072); (2N281)(0072); (2N281)(0072); (2N281)(OC I 6)(2-0C16)

Type Equivalent Type

1S161TS462TS163TS165TS166TS620TS621Z1132N2062N2072N207A2N207132N2152N2172N2182N2 I 92N2202N2312N2322N2332N233A2N2342N234A2N2352N235A2N236A2N2372N2382N2412N24 1 A2N2422N2522N2532N2542N2652N2682N2692N2702N2792N2802N2812N2822N2832N2S42N284A2N2922N2932N2962N2972N3012N301A2N3022N3032N3072N3112N3152N3162N3172N3222N3252N3262N3522N3532N3782N3802N3862N3942N3952N3962N397

(2-0072)(0071)(0071)(0072) (2N281)(0070) (0065)(0065) (0066)(0065); (0070)(0072)(0071)(0065); (0066)(0065); (0066)(0065); (0066)(0071)(0072)(0C45)(0C44)(0065); (0066)(0C45)(0C45)(0C45)(0C45)(0C16)(0C16)(0C16)(0C16)(0C16)(0065); (0066)(0072)(0072(0072(0C16(0C44)(0C45)(0C45)(0072)(OC 16)(0076)(0072)0070; 2N2790071; 2N2800072; 2N2812-0072; 2N2820071; 2N2800076; 2N2840077; 2N284A(0C45)(0C45)(0C16)(0C16)(0C16)(0C16)(0076)(0076)(0C16)(0076)(0076)(0076)(0076)(0072)(0C16)(0C16)(OC 16)(0C16)(OC I 6)(OC 16)(0C16)(0076)(0076)(0076)(0076)

Type

PRACTICAL TRANSISTOR

Equivalent Type Type Equivalent Type

RECEIVERS

Type Equivalent Type

2N402 (0071); (0072) 350 (0072) CV488 (0A81); (1N476)2N403 (0072) 352 (0072) CV1353 0A81; 1N4762N404 (0076) 353 (0072) CV2389 (0071)2N405 (0071) 830 (0C44) CV2400 (0071)2N406 (0071) 1032 (0072) CV3934 (OVA 55); (1N478)2N407 (0072) 1033 (0072) CV51052N408 (0072) 1034 (0072) DP6 (0A85); (1N478)2N409 (0C45) 1035 (0072) DP6C (0A85); (1N478)2N410 (0C45) 1036 (0072) DR126 (0065); (0066)2N411 (0C44) 1320 (0072) DR128 (0065); (0066)2N412 (0C44) 1330 (0072) DS60 (0A85); (1N478)2N413 (0C45) 1340 (0072) DS61 (0A85); (1N478)2N413A (0C45) 1350 (0072) DS6I A (0A85); (1N478)2N414 (0C45) 1360 (0072) DS62 (0A85); (1N478)2N414A (0C45) 1390 (0C45) DS604 (0A81); (1N476)2N425 (0076) 1400 (0C45) DS611 (0A81); (1N476)2N426 (0076) 1410 (0C45) DS621 (0A81); (1N476)2N427 (0076) A01 (0C45) G26 (0A85); (3(1N478)2N428 (0076) CGI-E (0A81); (1N476) GD I E (0A85); (1N478)2-0A72 2-0A72 CG4-E (0A81); (1N476) GDIQ (0A85); (1N478)2-0A79 2-0A79; 1N542 CGI 2-E (0A73); (0A90) GD2E (0A85); (1N478)2-0C162-0C30

2-0C162-0C30

CK705CK707

(0A85); (1N478)(0A85); (1N478)

GD2QGD3

(0A85); (1N478)(0A70); (0A73)

2-0072 2-0072; 2N282 CK708 (0A85); (1N478) GD3E (0A85); (1N478)13D (0C45) CK713A (0A85); (1N478) GD4E (0A85); (1N478)8E (0C45) CK721 (0071) GD5 (0A79)8F (0C45) CK722 (0071) GD6 (0A70)206 (0071); (0066) CK725 (0071) G D8 (0A81); (0A85)207 (0071); (0066) CK727 (0071) GEX34 (0A90)208 (0071); (0066) CK751 (0072); (2N281) GEX35 (0A73)222 (0C45) CK759 (0C45) GEX44 (0A81)223 (0C44) CK760 (0C45) GEX45/1 (0A85); (1N478)225 (0C45) CK761 (0C45) GEX45/2 (0A85); (1N478)228 (0C44) CK 762 (0C44) GFT20 (0072)300 (0072) CK766 (0C44) G FT26 (0C16)301 (0072) CK766A (0C44) G FT44 (0C45)302 (0072) CV425 (0A81); (1N476)310 (0072) CV442 0A73; 1N616

57


INTERNATIONAL LIST OF TRANSISTOR MANUFACTURERSAND THEIR ADDRESSES

Amperex Electronic Corp., 230, Duffy Ave., Hicksville, N.Y., U.S.A.Bogue Electric Mfg. Co., 52, Iowa Ave., Paterson, 3, N.J., U.S.A.British Thomson -Houston Co. Limited, Rugby.British Tungsram Radio Works, Limited, West Road, Tottenham, London, N.17.CBS-Hytron Div., Columbia Broadcasting System, Inc., 100, Endicott Street, Danvers, U.S.A.Centralab Div., Globe -Union Inc., 914 Y, East Keefe Ave., Milwaukee, 1, Wis., U.S.A.Clevite Transistor Products, 241-257, Crescent Street, Waltham, 54, Mass., U.S.A.Delco Radio Div., GM Corp., 700, East Firmin Street, Kokomo, Ind., U.S.A.Fretco Inc., 406, North Craig Street, Pittsburgh, 13, Pa., U.S.A.General Electric Co. Limited, Magnet House, Kingsway, London, W.C.2.General Electric Co., Semi -conductor Products, 1224, W. Genessee St., Syracuse, N.Y., U.S.A.General Electric Co. Ltd., of England, 80, Shore Road, Port Washington, N.Y., U.S.A.General Transistor Corp., 130-11, 90th Avenue, Richmond Hill, 18, N.Y., U.S.A.Hivac Limited, Stonefield Way, Victoria Road, South Ruislip, Middlesex.Hoffman Semi -conductor Div., of Hoffman Electronics Corp., 930, Pitner Ave., Evanston, Ill.Hughes Products, Div., of Hughes Aircraft Co., Los Angeles, 45, Calif., U.S.A.Lansdale Tube Co., Div. of Philco Corp., Church Road, Lansdale, Penn., U.S.A.P. R. 'Mallory and Co., Inc., 34, S. Gray Street, Indianapolis, 6, Ind., U.S.A.Minneapolis -Honeywell Regulator Co., Semi -conductor Div.,

2753, Fourth Ave. South, Minneapolis, 8, Minn., U.S.A.Motorola, Inc., Semi -conductor Products Div., 5005, E. McDowell Road, Phoenix, Arizona, U.S.A.Mullard Limited, Mullard House, Torrington Place, London, W.C.1.Newmarket Transistor Co.. Exning Road, Newmarket, Suffolk.Nucleonic Products Co., 1601, Grande Vista Ave., Los Angeles, 23, Calif., U.S.A.Outronic Semi -conductor Corp., 525, Broadway, New York, 12, N.Y., U.S.A.Radio Corporation of America, Electron Tube Div., 415, South 5th Street, Harrison, N.J., U.S.A.Radio Development and Research Corp., 100, Pennsylvania Ave., Paterson, 3, NJ., U.S.A.Raytheon Mfg. Co., 55, Chapel Street, Newton, 58, 'Mass., U.S.A.Red Bank Div., Bendix Aviation Corp., Eatontown, N.J., U.S.A.Semi -conductors, Limited, Cheney Manor, Swindon, Wilts.Standard Telephones and Cables Ltd., Connaught House, 63, Aldwych, London, W.C.2.Sylvania Electric Products, Inc., 1740, Broadway, New York, 19, N.Y., U.S.A.Technical Apparatus, 109, Liberty Street, New York, 6, N.Y., U.S.A.Texas Instruments, Ltd., Dallas Road, Bedford.Texas Instruments, Inc., 6000, Lemmon Ave., Dallas, 9, Texas, U.S.A.Transitron Electronic Corp., 168, Albion Street, Wakefield, Mass., U.S.A.Tung -Sol Electric. Inc., 95, Eighth Ave., Newark, 4, N.J., U.S.A.Twentieth Century Electronics, Ltd., King Henry's Drive, New Addington, Surrey.United States Dynamic Corp., 1250, Columbus Avenue, Boston, 20, Mass., U.S.A.Westinghouse Brake and Signal Co. Ltd., 82, York Way, Kings Cross, London, N.1.Westinghouse Electric Corp., P.O. Box 868, Pittsburgh, 30, Pa., U.S.A.Westinghouse Electric Corp., Electronic Tubes Div., P.O. Box 284, Elmira, N.Y., U.S.A.

BERNARDS RADIO BOOKSNo.35. Dictionary of Mathematical Data 2/-65. Radio Designs Manual ... 2/666. Communications Receivers' Manual 2/668. Frequency Modulation Receivers' Manual 2/673. Radio Test Equipment Manual 2/678. Radio and Television Laboratory Manual 2/683. Radio Instruments and Their Construction 2/686. Midget Radio Construction 3/696. Crystal Set Construction 1/-97. Practical Radio for Beginners, Book 1 3/-99. One Valve Receivers 1/6

100. A Comprehensive Radio Valve Guide, Book 1 5/-101. Two Valve Receivers ... 1/6102. 40 Circuits using Germanium Diodes . 3/-103. " Radiofolder " A. The Master Colour Code Index for Radio and Television 1/6104. Three Valve Receivers 1/6106. Radio Circuits Handbook No. 4 2/6107. Four Valve Circuits 1/6108. Five Valve Circuits 2/6112. " Radiochart " Electronic Multimeter Construction 2/6115. Constructors' Handbook of Germanium Circuits 2/6121. A Comprehensive Radio Valve Guide, Book 2 5/-123. " Radiofolder " F. The Beginners' Push -Pull Amplifier 1/6125. Listeners' Guide to Radio and Television Stations of the World 2/6126. The Boys' Book of Crystal Sets 2/6127. Wireless Amplifier Manual No. 3 3/6128. Practical Transistors and Transistor Circuits 3/6129. Universal Gram -Motor Speed Indicator 1/-131. " Radiochart " Guide to Modern Valve Bases 2/6132. Reactance -Frequency Chart for Designers and Constructors 1/6133. Radio Controlled Models for Amateurs 5/-134. F.M. Tuner Construction ... 2/6135. All Dry Battery Portable Construction 2/6138. How to make T.V. and F.M. Aerials Bands, 1, 2 and 3 2/6139. Practical Radio for Beginners, Book 2 3/6140. Television Servicing for Beginners, Book 1 4/6141. Radio Servicing for Amateurs 3/6142. Modern Television Circuits and Fault Finding Guide 4/6143. A Comprehensive Valve Guide. Book 3 5/-144. The New " At a Glance " Valve and Television Tube Equivalents 5/-145. Handbook of AM/FM Circuits and Components 2/-146. High Fidelity Enclosures 5/-147. Practical Tape Recording Handbook 5/-148. Practical Transistor Receivers, Book 1 5/-149. Practical Stereo Handbook 3/6150. Practical Radio Inside Out 3/6

Documents

PRACTICAL TRANSISTOR RECEIVERS Practical-Transitor-Receiver-Book-1.pdf · least a three -gang condenser, which is both bulky and difficult to align. They are, however, slightly cheaper