TELSEN SONGSTER 2+TELSEN CONQUEROR 3+TELSEN COMMODORE 3+TELSEN EMPIRE 4

RADIO COMPONENTS

Incorporating the Telsen radio componentcatalogue and the Telsen circuits, togetherwith building and operating instructions.

Vol. I (First Edition) (Copyright).

"B

BUILD BETTER!UILD BETTER " has been the sloganof British craftsmen for centuries passed.Since the early days of the " guilds "

skilled workmen have pooled their know-ledge in efforts to improve and uphold theircallings. C0 Build Better " has been thewatchword of our industries with the resultthat British goods have won for themselvesa high reputation in the minds of merchantsand consumers throughout the world.

With the dawn of broadcasting, a new hobbycame to life, a new form of entertainmentdestined to give untold pleasure. Throughoutthe remarkable developments of radio it hasbeen the constant desire of every homeconstructor to " build better." From thedays of the humble crystal to the presentmulti -valve superhetrodyne receiver, theamateur has kept pace, and even anticipatedthe trend of design and construction.Throughout this hectic race the amateur hasdevoted every attention to new circuitsemploying fresh coupling arrangements, orperhaps the addition of another valve, andlittle time has been available for undividedattention to the performance and efficiencyof the individual components.

As the years pass, sensational developmentsare becoming more rare, and although it cannever be accepted that the zenith has been

reached, it must be admitted that startlingchanges in the near future are certainly notindicated.

The time has arrived for the home con-structor to improve reception, not necessarilyby a change in circuit, but by studied choiceof each individual component. Highpowered broadcasting stations have erectedtheir masts in many parts of Europe ; their

"wavelengths are separated by only a fewmetres and the problem of reception be-comes increasingly difficult.

The employment of components designed byprominent radio engineers and manufac-tured with meticulous care and precisiondefinitely assists in overcoming these diffi-culties.

TELSEN components are produced undersuch conditions. The raw materials aresubjected to the most severe tests and onlythose which survive are incorporated in thefinished product. The actual manufacture iscarried out under the strictest supervisionand TELSEN components are tested underbroadcast conditions before they leave thefactory.

Thus the famous philosophy of Emersoncan very well be applied" THEY BUILD BETTER THAN THEYKNOW WHO BUILD ON TELSEN."

Page 2 THE TELSEN RADIOMAG.

Circuits designedfor simple construction

THE Telsen recommended circuits de-scribed in this booklet are not issued askits, but are intended for construction

with standard Telsen components obtainablefrom any radio dealer. Readers who require acomplete kit set are referred to the TelsenVictor 3, described on the back cover.

Nevertheless, the circuits offer not the slightestdifficulty in construction, even to the veriestnovice. No attempt has been made to lay downexact positions and sizes to a fraction of an inch,in order that constructors may use existingpanels, baseboards, cabinets, etc. For the samereason full size blue prints have not been issued,so that some latitude may be given to theindividual constructor. The most convenientstandard sizes, however, have been indicated,likewise the best layout for easy runs of wiring.It is not recommended that smaller baseboardsare used, otherwise the layout will be found toocramped for easy wiring.

In addition to the list of components given foreach receiver, a panel, baseboard and terminalstrip will be needed, together with the necessaryfixing screws, a few yards of insulated connec-ting wire and the requisite number of terminals.The baseboard should be of wood á or z in.thick, which will usually be found included if acabinet is purchased. The panel may be ofplywood or ebonite, but not of metal as thereaction condenser spindle must be insulatedfrom earth. The terminal strip should be ofebonite, about tin. wide, and may convenientlyrun the whole length of the baseboard.

The panel will need drilling for the controls, thehole sizes for all Telsen variable condensersbeing áin. full, and for Telsen switches sin.full. Exact positions are not laid down, but theconstructor should adhere to the symmetricalarrangement shown in each illustration. Threeor four small holes along the bottom edge of thepanel will suffice for fixing to the baseboard.The terminal strip must be drilled for the de-sired number of terminals, and also for fixing tothe baseboard.

A neat job may be made of the wiring with anyof the covered connecting wires on the market,or bare tinned copper wire may be used inconjunction with a suitable size of insulatedsleeving. Point to point wiring details have notbeen given, in conformity with the generalpolicy of these recommended circuits. Thediagram is, however, very simple to follow, infact much simpler than the usual " practical "diagram for the constructor who wishes tofollow the principles of the circuit-a practicestrongly to be recommended. Soldering isunnecessary, the white dots at the junction ofwires indicating that the terminals concernedare to be joined by the shortest route.

No technical knowledge is required for theconstruction or operation of the Telsen circuits,but if any reader, owing to inexperience, hasmisgivings regarding the wiring, he is recom-mended to try the Telsen Victor 3 Kit, withwhich a point to point wiring diagram isincluded. Practically all the components can beused later for building a more ambitious circuit.The general procedure in construction is asfollows :-Mount the terminals on the terminalstrip in the correct order, and attach to base-board. Lay out all the components in theposition roughly indicated in the blue print,using the photograph as a guide to a balancedlayout. Mark through the fixing holes of thecomponents and proceed to screw them down.Suitable sizes of screws are No. 4 by 2, 8, á andtin. long. Now complete the wiring as far aspossible, before mounting the panel componentsand attaching the panel. The wiring shouldthen be completed and the connectionstightened up all round. The batteries shouldbe connected by lengths of rubber -covered flexfitted with wander plugs for the dry batteriesand spade tags for the accumulator.Special notes on the construction and operationof each individual circuit are given in thefollowing pages, and further general instruc-tions with full notes on the subject of choiceand use of accessories will be found on pages1o, 23 and 31.

RADIO ,+GOMPAN.ENTS'-,

THE TELSEN RADIOMAG. Page 3

.1ieTELSEN "CONQUEROR"

Astraight three valve receiver employ-ing a detector and two L.F. stages,the Telsen " Conqueror " three is already

achieving an enormous and well deservedpopularity.

As an up-to-date version of what is certainly thefavourite circuit arrangement of the home con-structor, it presents several points of interest.In the first place, the selectivity adjustment ofthe Telsen Aerial Coil enables exactly the rightdegree of selectivity to be obtained for thelocality and conditions in which it is used.Regional programmes can be definitely separ-ated at any distance over 5 miles, and this with-out complicating the essential simplicity of thecircuit. The amount of foreign receptionavailable naturally will depend to some extenton the distance from the " local," but under allordinary conditions the principal foreignstations come in strongly.

Another point of interest is the .0003 mfd.Condenser connected across the terminals 4and 7 of the Aerial Coil. This serves tocut out any trace of short wave in-terference on the long waveband.

31'3

The quality of reproduction will be foundsurprisingly good up to the full volume of thesuper power valve recommended. This islargely due to the employment of a stage ofchoke coupling followed by a transformer.Differential reaction is employed, giving a widerange of control and the whole of the circuit issimple and straightforward.It is not desirable to vary the specification(other than in small details), except that ifpreferred, a Telsen air -spaced tuning condensermay be substituted for the Telsen bakelitetunirt,. condenser, and a Telsen slow motiondial may be fitted to either.

Complete set of Telsen Compo'nents for the " Conqueror" Three

Page 4 THE TELSEN RADIOMAG.

As regards the L.2., if this is connected tomaximum H.T. volts, i.e., if H.T.-2 andH.T.+3 have been run into one, G.B.-ishould be given a value of -3v. bias for allvalues of H.T. between ioov. and 120v. If, onthe other hand, a separate H.T. Tapping belowioov. is used, I2v. bias is the correct value.

VALVES RECOMMENDED.Detector .. .. V.I. MAZDA H.L.2.L.F. .. .. V.2. MAZDA L.2.Output .. .. V.3. MAZDA P.22o.A.

TELSEN "CONQUEROR" THREE.List of Components.

Quan- Descriptiontity

Cat.No.

Price

3 Valve Holders .. W.1o5 1 62 .0003 Mica Condensers,

with Clips W.93 1 01 .002 Mica Condenser .. W.97 6I Grid Leak, 2 meg. W. tot 9I Grid Leak, 1 meg. .. W.Ioo 9I Aerial Coil with Selec-

tivity adjustment . W.76 7 61 .0005 Bakelite Tuning

Condenser . W.134 2 01 .0003 Differential Re -ac-

tion Condenser .. W.14o 2 0I Three-point Switch .. W.Io8 1 31 Two -point Switch W.Io7 1 0

3-1 . W.66 5 61 LF. Choke, too henrys W.69 5 0I Standard H.F. Choke.. W.75 2 0I .00i Mica Condenser.. W.96 6

£1 11 3Panel 14 x 7 in.Baseboard 14 x 9 in.

The TELSEN "CONQUEROR" THREE (cont'd)

The " Ace " transformer may be substituted ifdesired by a Telsen 3-I "Radiogrand," orbetter still by a Telsen I.75-I, which will givea further slight but definite improvement inquality, appreciable to the critical listener.

If desired, terminals H.T.-2 and H.T.+3 maybe run into one, enabling the set to be workedfrom an eliminator with only two positivesockets.

The general notes on construction on pages 2and 10 and operation on page 23 should befollowed, and owing to the simplicity of this set,there are no special precautions to be added.

There is no choice offered for the valves requiredto enable this receiver to give its proper perfor-mance. A smaller power valve would be moreeconomical in H.T. consumption, but would bebadly overloaded under all normal receptionconditions, and the volume obtainable withoutdistortion would be very much reduced. Thesame remarks apply, to a less degree perhaps, tothe H.T. voltage available. I2ov. is reallydesirable if the set is to give of its best. Theproper bias for the P.22oA with I2ov. f` T. is9 volts (on G.B.-2) but an increase to Io2v.will have the advantage of somewhat reducedH.T. consumption with little falling off in thevolume which can be handled. As the H.T.battery runs - down, however, bias must bereduced in order to maintain quality. At 11ov.H.T., 9 volts bias is the most that can beallowed, and at loov. it should be 72v.

The theoretical circuit of theTelsen "Conqueror" 3.

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THE TELSEN RADIOMAG. Page 7

öeTELSEN "COMMODORE"

THE Telsen CC Commodore " Three is anadmirable set for the constructor who re-quires a highly selective receiver for a

reasonable outlay. The H.F. side of the circuitis identical in every way with the Telsen" Empire " Four, and the two tuned circuits,combined with the variable selectivity adjust-ment on the aerial coil, will give a high degreeof selectivity under all conditions. A goodrange of Continental stations can be receivedwith ample volume and clarity. The L.F.side incorporates a Telsen 7-I Transformer anda Tapped Choke Output Filter, which enableseither a Pentode or ordinary Super Power Valveto be used. Plenty of volume and splendidquality of reproduction is obtainable witheither. It will be noted on theblue print that there are two alter-native connections between theoutput choke and the 2 mfd.condenser. When using a Pen-tode, the centre connection "C"should be used, otherwise theconnection marked CQ P. & C.a."

No special instructions regard-ing the building appear to benecessary. It will be foundeasier to wire the base -boardwith the panel and screen notin position, and to add theseat a later stage when theybecome necessary in order tocomplete the wiring. Whereconnection is made to the screen

it is desirable to scrape the surface slightly toremove any trace of lacquer. It will be help-ful to read the comments on the constructionand operation of the Telsen " Empire " ScreenGrid Four on page 25 as well as the generalinstructions in other parts of this booklet.

Two terminals are brought out for the gramo-phone pick-up connection. Strictly, only oneis necessary as the other is connected directlyto the al volt tapping on the grid bias battery,and this connection may be made by means ofa wander plug direct instead of passing throughthe terminals shown. Further instructions onthe connection of a gramophone pick-up aregiven on page ao.

Complete set of Telsen Componentsfor the Commodore " Three

RADIO - COMPONENTS-

8

MAKE THE MOST OF YOUR FAVOURITE

B.T.H. " Senior" Pick-up and Tone Arm, latest modelwith ball bearing spring balance tone arm. Nickel orgilt finish, Price 45/-

B.T.H."Minor" pick-up and Tone Arm,moulded as one unitin Fabrolite com-pound, walnut brownfinish. Price 27/6.

NOWFOR THE BESTPOSSIBLEREPRODUCTION

B.T.H.

Minor"D.C."Model.

Price ,Cr 116

Minor Perma-nent Magnet

Modela

,f\

'/ REPRODUCERS1931/2 Models.Senior A.C. Model,NewReducedPrice£7 15 O. SeniorD.C. Model, NewReduced Price£5 5 0.1931/2 Senior Per-manent Magnet,New Reduced

Price £2 Io o Price £5 12 6.

RECORDSYou haven't heard your records at their bestuntil you've played them with a B.T.H. Pick-up.All these subtle inflections which the acoustic soundbox misses are faithfully reproduced. You willdiscover new beauty-a new brilliance of tone whichrediscovers even your favourite records. Leadingradiogram manufacturers pin their faith to B.T.H.Pick-ups-you too can achieve the finest possiblereproduction

with a

PICK -U Pand Tone Arm

If you want the best possiblereproduction you need an R.K.-the original moving coil speakerand still the standard of excel-lence against which other makesare judged.

There is an R.K. to suit everypurpose and pocket-from the"Minor D.C." model at 31/6to the " Senior A.C." model at£7 15s. od. Every R.K. is i00%British made.

EDISWAN RADIOAdvt. of :-' THE EDISON SWAN ELECTRIC CO., LTD.11: yo

THE TELSEN RADIOMAG. Page, 9

The TELSEN "COMMODORE" THREE (cont'd)

Of the three output valves offered as alter-natives, probably the best for all-round useis the Pen. 220 which, whilst giving excellentrange and ample volume, has the advantage ofkeeping the H.T. consumption of the set belowi0 mA. and thereby effecting considerableeconomy in battery expenditure. The Pen.220A. is a power pentode which will handle agreater power than the P. 220, and is not easilyoverloaded.

The power valve P. 220A. is recommended tothe set builder who, whilst requiring amplevolume with high quality on the local trans-missions and also on the main foreign stations,chooses a screen grid set for its selectivityrather than extreme range.Both pentodes have an extra connection, whichmay take the form of a terminal on the side ofthe base, or a fifth pin. In the latter case afive pin valve holder should be substituted forV.3. The extra connection in either case mustbe connected by means of a flexible wire to anadditional H.T. wander plug. This plug inthe case of the Pen. 220 should be connectedto 100-105 volts, and the correct value of gridbias is then -3 volts (on G.B.-2). Whenusing the Pen. 220A. the value for the extraH.T. lead is 120, and bias -'7 volts.120 volts H.T. is recommended for H.T.+3,and the screen voltage (H.T.+i) should bevaried between 50 and 8o volts for best results.

The theoretical circuit of theTelsen "Commodore" 3.

The detector voltage (H.T.+2) is not critical,and may be between 6o and 8o volts. A biasof -i4 volts should be applied to the screengrid valve (G.B.-i).

VALVES RECOMMENDED.H.F. V.' MAZDA S.G.215.Detector V.2 MAZDA L.2.Output V.3 MAZDA P.22oA., Pen. 220 or

Pen. 220A.

TEL SEN "COMMODORE" THREELIST OF COMPONENTS

Quan-tity Description

Cat.No. Price

I " Radiogrand " 7-1 Transformer W.60 12 61 Tapped Output Choke, 20 henrys ... W.72 8 61 Binocular H.F. Choke ... ... W.74 5 0I Standard H.F. Choke W.75 2 01 Aerial Coil with Selectivity Adjust.

W.76 7 61 2 mfd. Mansbridge Type Condenser W.77 3 01 I mfd. Mansbridge Type Condenser W.78 2 32 .0003 mfd. Mica Condensers ... W.93 1 01 Grid Leak, 2 meg... .-. ... W.101 93 4 -pin Valve Holders ... ... W.105 1 61 Two -point Switch ... ... ... W.107 I 02 Three-point Switches W.108 2 62 .0005 mfd. Logarithmic Condensers W.132 9 02 Slow -Motion Dials ... ... W.141 5 01 Fuse Holder ... ... ... W.146 62 Grid Leak Holders ... ... ... W.148 1 01 H.F. Coil ... ... ... ... W.154 5 61 Screen .. .. ... ... W.166 2 01 .1 mfd. Mansbridge Type Condenser W.82 1 92 .001 mfd. Mica Condensers ... W.96 1 01 I meg. Grid Leak W.98 9I .00015 mfd. Differential Re -action

Condenser ... ... ... W.139 2 0

£3 16 0

Panel size 18 x 7 in.Baseboard size 18 x 10 In.

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Page I THE TELSEN RADIOMAG.

Hints and Tipson construction

THE following notes on constructionshould prove very useful to the amateurwho is building one of the Telsen circuits.

FIXEDCONDENSERS.A point whichmay not be quiteclear from theblue prints is theconnection of thefixed mica cc n-

densers carrying grid leaks. The Telsen.0003 Mica Condenser is sold with patent gridleak clips which may be mounted to give eitherseries or parallel connection. In the Conqueror3 and Songster 2, condensers are used with theseries arrangement. It is important to note thatone clip should bemounted facingthe front of thecondenser, usingone of the sparenuts, and the otherfacing the back,using the sparescrew, nut and terminal. The exact arrange-ment used in the Songster 2 is shown in Figurei. Figure 2 shows the arrangement in theConqueror 3. It does not actually matter whichclip faces forward, so long as that is the oneconnected to the G terminal on the valveholder, and the other to F.

USING A GRAMOPHONE PICK-UP.Any of the circuits in this book may be used toreproduce gramophone records by the simpleconnection of a gramophone pick-up. In theEmpire 4 and the Commodore 3, terminals arebrought out for this purpose, but additional

information on this point may be useful.Figure 3 shows the pick-up connected in itssimplest form. G is the grid connectionto a valve, usually the detector, and GB repre-

sents a wander plugFIG. 3 o P which may be per-

manently plugged intothe bias battery. Inthe case of the detectorvalve, i¡ volts is thecorrect amount of biasunder all normal cir-cumstances. In the

Empire 4 the grid of the first L.F. valve is used,because the full amplification of two L.F.stages, fed from a sensitive pick-up, will causebad overloading of the output stage and there-fore distortion, unless a volume control is used.The same applies toalmost any circuitusing two stages ofL,F. as in the Con-queror 3. When usingthe first L.F. valve,which is alreadybiased negatively, theother connection tothe pick-up is madeto the existing bias connection, which in theEmpire 4 is GB -2.

A simple 2 -point switch may be inserted in thegrid .circuit to avoid the necessity of dis-connecting the pick-up when it is not in use.If the detector valve is the one concerned, thewire from its grid to the switch or terminal mustbe as short as possible.

Figure 4 shows how a volume control is con-nected with a switch included as describedabove. Both may be conveniently mountedon the panel.

TELSEN "RADIOGRAND" L.F.TRANSFORMERS

Telsen "Radiogrand " Transformers havesignified to expert designers and enthusiasticconstructors all that is finest in British radiocraftsmanship. Every " Radiogrand "Transformer is built on the soundest engin-eering principles and tested under broadcastconditions for immaculate performance andenduring efficiency.Ratio 3-1. No. W.59. Ratio 5-1. No. W.58.

Price 8/6

TELSEN"RADIOGRAND"

RATIO 7-1TRAN SFOR M E RThis transformer is designedto give extra high amplifica-tion on receivers employingonly one stage of L.F. amplifi-cation.Following the detector inthe popular screened grid threearrangement it will give sufficientpower to load fully the outputvalve. It is not recommended foruse in receivers employing two L.F.Stages as overloadingis likely to occur.

No. W.60.

Price 12/6

TELSEN "ACE" L.F.TRANSFORMERS

Similar" Radiogrand" Transfor-mer in its life -like repro-duction and capacity forreliable service, the Tel-sen "Ace " is eminentlysuitable for receiverswhere highest efficien-cy is required at a lowcost and where spaceis limited.

Ratio 3-1 No. W.66Ratio 5-1 No. W.65

Price 5/6

TELSEN "RADIOGRAND" INTER -VALVE TRANSFORMER, RATIO

1.75-1For use in receivers employing two stages of L.F.amplification, where exceptionally good quality isdesired. The somewhat lower step-up ratio is amplyoffset by the - extra power available under modernreceiving conditions. When used following an L.F.stage employing choke coupling it will be found togive ample volume with remarkable reproduction.

No. W.61.

Price 12/6

1

TELSEN OUTPUT TRANSFORMER,RATIO I - I

This Transformer is intended for connecting theloudspeaker to the output stage of the receiver.Its object is to avoid saturation of the loudspeakermagnet system, by isolating the direct current fromthe speaker windings. This produces a remarkableimprovement in the quality of reception. It alsoserves to keep H.T. voltage from the speaker andits leads, which is especially important when usinga D.C. Eliminator. The primary terminals shouldbe connected to the original loudspeaker terminalson the receiver, and the loudspeaker should then beconnected across the secondary of the transformer,which may be mounted inside or oustide thereceiver.

No. W.62.

Price 12/6

TELSEN MULTI RATIOOUTPUT TRANSFORMERThis is designed for use with MovingCoil Loudspeakers having low im-pedance speech coil windings. It hasthree ratios, 9-1, 15-1 and 22.5-1.The primary is connected in theanode circuit of the output valveand the speech coil of the lbud-speaker is connected to two of thesecondary terminals. The choiceof three ratios enables the cor-rect matching of speakers ofwidely varying characteristics.

No. W.63.

Price 12/6

TELSENPÉNTODE OUTPUTTRANSFORMERThe purpose of the TELSEN pentodeoutput transformer is to prevent directcurrent passing through the loudspeaker,and also to match the speaker to the pen-tode valve, which is essential for goodquality reproduction. It should be con-nected in the output circuit where the out-put valve is a pentode. By using this trans-former the quality obtained with the pentodevalve becomes quite equal to that expectedfrom a normal super power valve.

No.W.64.

Pace 12/6

{i

TELSEN INTERVALVE L.F.COUPLING CHOKES

These popular L.F. Chokes are primarily intendedfor use as coupling chokes in the anode circuits ofmodern radio receivers, but may be used in anycircuit not carrying more than the stipulatedmaximum current. The 100 H. type should beconnected in the anode circuit of an H or HLtype valve. The 40 H. type is designed for usewith an L type valve. Either is highly suitable forpower grid detection where the anode current doesnot exceed the specified limit.

Normal Max.Rating Current Current No.40 H. at 5 mA. .. 8 mA. W.68

100 H. at 3 mA. .. 6 mA. W.69

Price 5/-

TELSEN HEAVY DUTYPOWER GRID L.F. CHOKEThis choke is designed to fill thedemand for an intervalve chokewhich will carry the heavyanode current of indirectlyheated valves in Power GridDetection circuits. It is alsosuitable for second -stagesmoothing in circuits notcarrying more than 12 mA.40 henrys (at 12 mA.).

No. .W.73.

Price 8/-

TELSENOUTPUT CHOKES(Tapped and Plain)

Designed for use as Output FilterChokes in conjunction with a con-

denser of not less than 2 mfd. thesechokes are highly suitable with any power

or super power valve taking up to 25 mA.The centre tapped choke may be used with

pentodes, or where the loudspeaker imped-ance is appreciably lower than that of the

valve, so that closer matching is obtainable.The plain choke is also suitable for smoothing

currents up to 25 mA.Telsen Output Choke (plain), 20 henrys (25mA)

No. W.71 .. .. .. Price 8/-Telsen Output Choke (tapped), 20 henrys (25mA)

No. W.72 .. .. Price 8/6

TELSEN BINOCULAR H.F.CHOKE

In H.F. amplification the performance of a chokeis of supreme importance. The Telsen BinocularH.F. Choke is called for wherever the highestefficiency is required. Its high inductance (180,000micro -henrys) and exceptionally low self -capacity(.000002 microfarad) ensure a very high impedanceat all wavelengths, and its excellent efficiency curveproves that it is free from parasitic resonances.These qualities, together with the restricted field dueto the binocular formation, make it the ideal chokefor a high class circuit.

No. W.74.Price 5/ -

The curve below, published by courtesy of AmateurWireless, represents the efficiency of the TelsenBinocular Choke over the broadcast band.

IOÓ

Co

80

TELSEN STANDARD H.F. CHOKEThe Telsen Standard H.F. Choke, whichutilises the minimum baseboard space, is de-signed to cover the whole broadcast band andhas the very low self -capacity of .000008microfarad. It is highly suitable for reactioncircuits. The inductance is 150,000 micro -henrys and the resistance 400 ohms. It hasproved very popular and has been incorpor-ated by set designers in many of the leadingcircuits.

No. W.75.

Price 2/-

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200 400 600 800 1000 1200 400 1600 1800 2000

TELSEN AERIAL COILThis is the latest development in dual -range aerial coil design ; it incorporatesa variable series condenser which canbe set to give any desired degree ofselectivity, making the coil suitable forall districts whatever reception condi-tions may be. This adjustment alsoacts as an excellent volume control, andis equally effective on long and shortwaves. The waveband change is ef-fected by means of a 3 -point switch. Areaction winding is included. Full par-ticulars with wiring diagram are in-cluded with every Telsen Aerial Coil.

No. W.76.

Price 7/6

TELSEN H.F. TRANSFORMER ANDAERIAL COIL

This coil is primarily designed for H.F. amplification inconjunction with screened grid valves. It is arrangedso that it can be connected as an H.F. Transformer oralternatively as a tuned grid or tuned anode coil. It alsomakes a highly efficient aerial coil where the adjustableselectivity feature is not required. A reaction winding isincorporated. When used as an H.F. Transformer thewave change is effected by means of a 2 -pole switch, suchas the Telsen No. W.153; when connected Otherwise useTelsen 3 -point switch No. W.108. Full particulars withwiring diagram are included with every Telsen H.F.Transformer and Aerial Coil.

No. W.154.

Price 5/6

0.

TELSEN BAKELITE DIELECTRIC CONDENSERSThese condensers are of a new and improved type and of exceptionallycompact dimensions. The rotor vanes are keyed to the spindle andfitted with definite stops. The vanes are interleaved with finest qualitybakelite. Fitted with pigtail connection to rotor. Supplied completewith knob.

TELSENBAKELITE DIELECTRICTUNING CONDENSERDesigned and constructed on the sameprinciples as the Telsen Bakelite Di-electric Differential and Reaction Con-densers. The connection to the rotoris made by means of a phosphorbronze pigtail so that no cracklingdue to rubbing contacts is possible,The connection to the stator vanesis absolutely positive. Suppliedcomplete with knob.Capacity .0005. No. W.134.Capacity .0003. No. W.133,

Price 2/-

TELSEN LOGARITHMICVARIABLE CONDENSERSThe Telsen Variable Condenser is builtto stand years of service. The sturdyframe is braced by three solid pillars andthe effective clamping of the vanes, eachheld at three points, makes distortion im-possible. The rotor also is built into a rigidunit, the vanes being held at both ends.Generous bearings provide against backlashor end play and the spacing will remain ac-curate as long as the condenser is in service.Capacity .0005. No. W.132.Capacity .00025. No. W.130.Capacity .00035. No. W.131.

Price 4/6

Differential Condensers.Capacity

.0003

.00015

.0001

No. PriceW.140

W.139

W.138

2/ -

Reaction Condensers.Capacity No. Price

.0003 W.137

.00015¡

W.136 } 2/-.0001 W.135

2/6.00075 W.158 t.0005 W.157 f

TELSEN. PUSH-PULL SWITCHES(Prov. Pat. No. 14125/31)

The Telsen Push -Pull Switches are designed on sound engineeringprinciples. They employ the " knife " type of self-cleaning contact,as used in electrical powerwork, and a positive snap action. Thenickel silver bridge piece is driven between the springy " fixed "contacts, and the wedge-shaped plunger squeezes the inner con-tacts outwards, closing the jaws in a firm grip. The series gap reducesself -capacity to a minimum, and the spindle is insulated from allcontacts.

Three-point. No. W.108.

Price I /3

Two -point. No. W.107.

Price 1 /-

TELSEN FOUR -POINT " TWO -POLE " PUSH-PULL SWITCH

(Prov. Pat. No. 14125/31).Designed on exactly the sameprinciples as the Telsen two -point and three-point switchesdescribed above, this model is atwo -pole switch highly suitablefor use in wave changing on twocoils or an H.F. Transformer.

No. W.153.Price I /6

TELSEN SLO WMOTION DIAL

Beautifully moulded in black orbrown bakelite, the Telsen Slow Motion

Dial has an exceptionally smooth actionwith a ratio of approximately 8-1.There is no toothed gearing, so that

it is impossible to strip the dial. Thefigures are clearly marked and are ar-

ranged to provide for right or left handrotation. Supplied complete with screws

and nuts for fixing to the panel.No. W.141.Price 2/6

TELSEN LOUDSPEAKER UNITThe Telsen Loudspeaker Unit has earned unstinted praise from all quarters It provides at a popular price a reliable unit which gives a very line per-formance pleasing to the most sensitive ear. The natural resonances havebeen adjusted so that a good balance of tone results, and the unit gives, forall its compact dimensions, a surprising depth of tone without losing thecrispness necessary for good reproduction. A detachable cone rod, chuckand washers are included, also -brackets for mounting on any standardchassis.

No. W.54.Price 5/6

This sketch shows the methodof fixing the Telsen LoudspeakerUnit to the Chassis with theangle brackets and screws pro-vided.

TELSEN LOUDSPEAKER CHASSISThe fully floating cone of specially prepared damp resisting material ismounted on a flexible felt surround in a rigidly constructed, light,pressedaluminium frame. The material and proportions of the cone have beenselected to give an exceptionally natural balance of tone free from objec-tionable resonances. The cone is fitted with cone washers and chuck to takethe loudspeaker rod, and the frame is pierced for easy attachment to mostof the popular loudspeaker units. Combined with the Telsen Unit it formsan ideal inexpensive combination, which, for natural reproduction and allround performance, rivals the highest priced units.Telsen " Major " Loudspeaker Chassis, diam. 141 ins. No. W.170.

Price 10/6Telsen " Popular" Loudspeaker Chassis, diam. 11 ins. No. W.159.

Price 5/6

This shows the Telsen Chassiswith Unit attached, screwed to abaffle board by means of woodfixing screws placed through thepierced holes provided in theouter rim of the Chassis.

TELSEN MANSBRIDGE TYPECONDENSERS

The following capacities are accuratewithin 5 per cent. of the stated values.

Cap.Mfd.

500 volt testCat. No. Price

1,000 volt testCat. No. Price

.01 W.83 .. 1/6 W.90 2/6

.04 W.81 .. 1/9 W.88 .. 2/9

.1 W.82 .. 1/9 W.89 .. 2/9

.25 W.80 .. 2/- W.87 .. 3/-

.5 W.79 .. 2/3 W.86 .. 3/31.0 W.78 .. 2/3 W.85 .. 3/62.0 W.77 .. 3/- W.84 .. 5/-

TELSEN MANSBRIDGE TYPECONDENSERS

These are made from the finest materials it'is possible to obtain. Manufactured by the

most advanced processes known, they aresubjected to the most stringent tests.The test peak voltage is discharged bydirect short circuit before the insula-tion tests are made and the higheststandards of insulation are adopted.Telsen Mansbridge type self-sealingcondensers are absolutely non -induc-tive. They are dehydrated in ahigh vacuum, impregnated andsealed, so that their high efficiencywill endure indefinitely. Forcapacities and prices see tableabove. The illustrations showTelsen 1 mfd. and 2 mfds.Mansbridge Type Condensers.

TELSEN FIXEDMICA CONDENSERS

(Prov. Pat. No. 20287/30)The Telsen Fixed Mica Condensers aremade in capacities up to .002 mfd.Careful design and manufacture result inthe H.F. losses being practically neglig-ible. The .0003 Telsen fixed mica con-denser is supplied complete with patentgrid leak clips for series or parallel con-nection. All sizes may be mounted up-right or flat.Cap. Mfd. No. Cap. Mfd. No.

.002 W.97 .0003 W.93

.001 W.96 .0002 W.92

.0005 W.95 .. .0001 W.91.0004 W.94

Price 6d.

TELSEN VALVE HOLDERS(Prov. Pat. No. 20286130)

Telsen valve holders incorporate a newdesign embodying patent metal springcontacts, which provide the most efficientcontact with split or non -split valve legs.The metal springs are extended in onepiece to form soldering tags. Telsen valveholders have a very low capacity and areself -locating.4 -pin. No. W.105. 5 -pin. No. W.106.

Price 6d. Price 8d.

1/411F,700 .FR

.TCf

TELSEN GRID LEAKSThese are absolutely silent, and prac-tically unbreakable. Telsen gridleaks do not vary in resistancewith application of different volt-ages. They are non -inductiveand produce no capacity effects.

Cap.Megohms. No.

5 W.1044 W.1033 W.1022 W.1011 W.100

W. 99W. 98

Price 9d.

TELSENPRE-SET CONDENSERS

The very low minimum capacity ofthe Telsen pre-set condensers gives awide range of selectivity adjustment

when used in the aerial circuit. Theyare substantially made, easily adjusted

and provided with a locking ring. Highinsulation and low loss.

Max. Cap. Min. Cap. No.Mfd. Mfd..002 .00025 W.149.001 .000052 W11.50

.0003 .000016 W.151

.0001 .000005 W.152

Price I /6

TELSEN SCREENSThese are beautifully finished, anda series of holes is provided for fixingin different positions the movableterminals which are supplied.In model No. W.167 a hole is providedfor mounting the screened grid valvein a horizontal position.

No. W.166. No. W.167.Price 2/- Price 2/6

TELSEN FUSEHOLDER

A neat and inexpensive devicewhich should be incorporatedin every receiver as a precau-tion against burnt out valves.The terminals are easily ac-cessible and the fuse bulb isheld firmly, giving a perfectcontact which cannot be-come loose.

No. W.146.Price 6d.

Note. -The illustrationshows the TeIsen fuseholder in use with thestandard type fuse.

TELSEN GRID LEAKHOLDER

This will hold firmly any standardsize or type of grid leak. The springcontacts are extended in one pieceto form soldering tags, and the ter-minals and fixing holes are acces-sible without removing the gridleak.

No. W.148.

Price 6d.

TELSENSPAGHETTI FLEXIBLERESISTANCES

These resistances are made from the finest nickel -chrome wire wound on a pure cotton core, stoved

/dal,

and impregnated so that moisture cannot attackthe wire and cause corrosion. The bending of the

resistance will not alter its value. The tags arefirmly clamped to the element and are clearly

marked with the value after stringent test.Made in the following values :-ResistanceMaximumPcfce

Ohms. Current30060042 mA. }6d.750 1,000 42mA.1,500

2,00023mÁ.3,0004,00023-mA.9d.5,00023 mA.0,00015,0006 mA.,00025,0006 mA.I /-,0006 mA.00060,000 3 mA.l(600 100,000 3 mA, j

THE TELSEN RADIOMAG. Page 23

Makingreception simple

WHEN the batteries and loud speakerhave been connected, insert the valvesaccording to the list recommended with

each circuit and the set will be ready forreception.First turn the reaction control to the left as faras possible, which is the position for minimumreaction ; also turn to the extreme left the knobon top of the Aerial coil, which is the positionfor maximum input or minimum selectivity.Now pull out the switches on the front panel.The right-hand two -point switch makes thevalves alive, and the three-point switches, whenpulled out, set the coils for reception of thelower Broadcast band. On turning the tuningknob or dials slowly, reception of the localstation should be heard if it is transmitting atthe time. In the case of the Telsen " Com-modore " S.G.3. and Telsen " Empire " S.G.4.where there are two tuning controls, it will benecessary to keep them in step, starting at thelower end. On receiving signals, adjust eachdial separately to the position of maximumstrength. If reception is now too loud thevolume may be reduced by turning the knobon the Aerial coil slowly to the right. ,Adjustslightly the tuning if necessary.This procedure is essential for cutting outinterference from one station while receivinganother. With the set tuned to the station youare wanting to receive, turn the selectivitycontrol slowly to the right until the interferingstation disappears, at the same time slightlyadjusting the tuning if necessary. If volume isnow insufficient it may be made good by theuse of a little reaction. A setting will usuallybe found for the selectivity control which givesbest all round results, and continual adjustmentshould not be necessary.The reaction control should be used sparingly.On turning this control slowly to the right onany station, volume will be found to increaseup to a point at which distortion sets in andfinally the set goes into oscillation. It must notbe left in this condition.

It cannot give you proper entertainment andif increased range is desired the only satis-factory solution is to build a more powerfulset. Generally speaking, use as little reactionas possible to give the requisite volume.To receive long waves, push in the three-pointswitch or switches and proceed as before.

AERIAL AND EARTH.For general purposes an aerial about 6o feet long andas high as possible will give greatest range. Whenclose to a powerful. Broadcasting station-say withinio miles, it may be helpful to cut the length down tohalf, though the selectivity control on the TelsenAerial Coil will compensate for all but extreme cases.(The use of the selectivity adjustment is somewhatequivalent to reducing the size of the aerial). Theaerial should be kept as far as possible from trees,chimneys, etc., and the down lead should be wellclear of the wall. It must be well insulated whereverit is suspended or passes into the house.The earth lead should be as short and direct aspossible. A main water pipe makes the best earth ofall, but if this is not convenient an earthing tubedriven into soil (which is kept damp in dry weather) isthe next best. The connection to the earth tube isusually a weak point and should be inspectedoccasionally.The aerial will normally be attached to the terminalmarked At on the blue print (in conformity withusual practice) but connected to terminal 2 on thecoil. When in this position, the selectivity control isin operation. Maximum input (and minimumselectivity) is obtained with the coil knob turned tothe left.If the set is used some distance from a powerfulstation, or if the aerial is so short that no interferenceis obtained even when the control is all "in," the aerialmay be connected to Az (terminal t on the coil) whichwill give slightly greater range. This, of course, putsthe selectivity control out of action. In extreme cases',as when an indoor aerial is used on a set of moderatepower, not close to a Regional station, the aerial maybe tried on terminal 8 of the aerial coil. This will givemuch increased power, but tuning would be too flatexcept under the conditions described. There is noharm in trying the different aerial connections.When using a D.C. Eliminator it is advisable tokeep to At as first described.

RADIO COMPONENTS

MAKE CERTAIN OFGOOD RESULTS

use these superquality batteriesThere is an added liveliness about the set fitted withEdiswan Batteries. A sense of crispness-a new fullness oftone-a sharpness of tuning, which were not there with theold H.T. and L.T.Made by an entirely new process at Ponder's End,Middlesex, Ediswan Radio Dry Batteries will give you longeruseful service than other types are capable of-and they costno more.Ediswan Accumulators, too, give you definite advantages intheir paste retaining grids of specially strong constructionand the famous Ediswan dry charge process which abolishesthe tiresome and prolonged first charge.

EDISWANRADIO DRY BATTERIES & ACCUMULATORS

PRICESRADIO ACCUMULATORS

B.W.G. 224 AMPERE HOURS .. 8,9

B.W.G. 336 AMPERE HOURS ..11/9

B.W.G. 448 AMPERE HOURS ..13/9

MAJOR70 AMPERE HOURS .. 11' -

PRICES

RADIO BATTERIES

60 VOLT 10 M/A .. .. 7/9

66 VOLT IO MA .. .. 8/6

120 VOLT 1O MA ,. ..14/660 VOLT SUPER POWER

20 M/A..15/6120 VOLT SUPER POWER

20MA..31.

THE TELSEN RADIOMAG. Page 25

//

eTELSENRE4uuuoluuu

II Il

THIS is the circuit for the constructor whorequires long range and a big reserve ofpower with really high quality reproduc-

tion. This powerful circuit employs a stage ofscreen grid H.F. amplification and two stages ofL.F. There are two tuned circuits employingthe new TEL SEN Dual Range Coils which areseparately tuned to give the greatest efficiencyand ease of control, at the same time relievingthe constructor of any ganging troubles.Additional selectivity is provided by theselectivity adjustment on the Aerial Coil, whichnot only contributes to eliminating interference,but also enables the excessive power of the localstations to be kept fully under control. Thescreen grid valve is biasedby the common GridBias battery, and thebiasing lead is decoupledto eliminate any possi-bility of feed -back at thispoint. The screening gridis decoupled by a i mfd.condenser, and a separateH.T. lead is provided forit to give a wider controlof stability.

Passing to the other sideof the screen, the H.F.valve is coupled to thedetector by the tunedgrid method. Reaction isapplied through a differen-tial condenser fed fromthe detector plate. TheL.F. side is interesting byreason that it employs a

RADIO COMPO

uu,1,,,n,p,,,,1,,,si11¡

stage of choke -coupled amplification followedby a Telsen 1.75-I transformer. This arrange-ment, together with the choke output filter,combine to give complete L.F. stabilitywithout the necessity for decoupling, andexceptionally rich and natural reproduction.In spite of the splendid results obtained fromthis powerful circuit it presents no difficultywhatever in construction. The general pro-cedure outlined on page 2 can be followed withconfidence. After attaching the terminal strip,which may be in one piece, or in two sections asshown in the photograph, the baseboard com-ponents should be laid out in the positionsindicated by the blue print, but following thephotograph as an indication.

Complete set of Telsen Cornpo-nents for the " Empire " Screen -Grid Four.

s'p^,"SEY\,

l'_''

Page 26 THE TELSEN RADIOMAG.

THE TELSEN " EMPIRE" FOUR (cont'd)

Space should be left for the screen, but itshould not be put on at this stage, as thewiring of the baseboard will be easier withboth the panel and screening absent.These may be added afterwards when theswitches and variable condensers have beenmounted. Where connections are made to thescreen it is advisable to scrape the surface toremove any trace of lacquer. The slow motiondials present no difficulty, but it will be necessaryto mount the tuning condensers with one edgevertical as shown in order to clear the dialfixing screws, and also in one case to giveclearance from the screen. It is not advisableto vary the specification ; the L.F. side willnot be improved by attempting to get a higherratio of amplification. The arrangement shownis sufficient to load fully the super power valveunder all normal conditions, and even ondistant stations.The H.F. side will be found quite stable asarranged, provided suitable values are chosenfor H.T.+ i and H.T.+2. If these are too highthe set may be found slightly unstable at thetop of the long wave scale, and the voltagetappings should be reduced until completestability is obtained. This will be round about6o volts in each case, H.T.+i being moreimportant than H.T.+2.(cont'd on page 32)

TELSEN "EMPIRE " S.G. FOUR.List of Components.

Quan- Description.City.

Cat.No.

Price

1 "Radiogrand " 1.75-1 Transformer W.61 12 61 Output Choke, 20 henrys ... ... W.71 8 01 L.F. Choke, 100 henrys ... ... W.69 5 01 Binocular H.F. Choke ... ... W.74 5 0I Standard H.F. Choke ... ... W.75 2 01 Aerial Coil with Selectivity adjust-

ment. ... ... ... ... W.76 7 61 1 mfd. Mansbridge Type Condenser W.78 2 31 .1 mfd. Mansbridge Type Condenser W.82 1 92 .0003 mfd. Mica Condensers ... W.93 1 01 .002 Mica Condenser ... W.97 62 .001 Mica Condensers ... ... W.96 1 01 Grid Leak, 1 meg. ... W.100 91 Grid Leak, 2 meg. ... ... W.101 91 Grid Leak, } meg. ... ... ... W.98 94 4 -pin Valve Holders ... W.105 2 o1 Two -point Switch ... ... ... W.107 1 02 Three-point Switches ... ... W.108 2 62 .0005 Logarithmic Condensers ... W.132 9 0

1 .00015 Differential Reaction Con-denser ... ... ... ... W.139 2 0

2 Slow-motion Dials ... ... ... W.141 5 01 Fuse Holder ... ... W.146 63 Grid Leak Holders ... ... ... W.148 1 61 H.F. Coil W.154 5 61 Screen ... ... ... ... W.166 2 01 2 mfd. Mansbridge Type Condenser W.77 3 0

£4 2 9Panel size 21 x 7 in.Baseboard size 21 x 101 in.

000

IMF

0005

Ó

-JJJtMbWV ` ^ '25 Mdl GB -I r -

MT+1 SCREEN,/MT+2

0

M FC

HT+3

0

MFc 100 H

002 175-1

n7;

'001

GB -2

n

GB -3

20 M

RJ 341LS

The theoretical circuit of the Telsen "Empire" 4.

FOSE0,0O GB*

Q NT -

O/ LTp i- +

.......:

u

THE TELSEN `EMPIRE' S.G.4

W 61

P

TELSENRADIOGRANDRATIO I75 -I

G GBu-,

4

:W105

T-I

1.) Zm3mor

0TzmocnZ

YI

W132 n

W 1012 MEG

W148

W105

W146 W77 -- >----;

II

ó bb á bHT- + -3 LS

GB

V3

L

L---

W93

-0 '0003

W105

V2O_ --}-ttnzti.+ '

{WI08

(

W154

W97

W 75

W69

W74--

I 4 ----,I

ó óo ó bGB -2 GRAM HT+2 HT+3

W96

W96

To 5G.ANODE

E-W166

W I 32 n

W98

W 93

-b 0003 0---4

W 76

w

----II48 -- .

W78 W82

HTU+I GB-I

t-{--

w

S

b bA2 Ai

WIRING DIAGRAM

W107

THE TELSEN 'SONGSTER' 2

W96-- -0 00IMFD. o-

W I05

V2

454-.

W65

(t\I 1

- --n n ----

ftvw I05c. .. `.lc

`--- W93

LTt - t +2 +1 - t LT- HT-LS HT GB

W I08

'W93'0003MFO.

W76

O OA2 ?i

WIRING DIAGRAM

THE TELSEN RADIOMAG. Page 29

TELSEN SONGSTER"e.N0ui u,

THIS is a simple but highly efficient twovalve receiver which will appeal to many,not only for its low first cost and economy

in upkeep, but for the satisfying loudspeakerreception which it will give. Owing to theincorporation of the TELSEN SelectivityAerial Coil it will definitely separate Regionalprogrammes at any distance over five miles.This set, therefore, is all that is necessary forsatisfactory reception of the local transmissions,which is the accepted sphere of the two valvereceiver. Nevertheless, when operated nottoo close to the local station, foreign receptionmay certainly be expected with a good aerial.The Telsen " Songster " Two is also perfectlysuitable for reproducing gramophone recordswith the aid of a pick-up. Full instructions willbe found on page to. A volume control acrossthe pick-up would be desirable. The qualityof the reproduction, both on radio and gramo-phone, is very good and worthy of a goodloudspeaker.Construction and operation are simpli-city itself and reference to thegeneral instructions given in thisbooklet covers everything thatneed be said.Very little alteration is possiblewithout detracting from theessential simplicity of the ar-rangement. If desired, thebakelite tuning condenser maybe replaced by an air -spacedlogarithmic variable condenserand a slow motion dial may befitted to either. A Telsen"Radiogrand " 5-1 Trans-former, or better still, a Telsensuper ratio 7-I "Radiogrand"

may be fitted in place of the Telsen " Aceand will, of course, give an audible differencein performance. These matters are open to thepreference of the individual constructor.A matter worthy of attention is the choice ofoutput valves offered together with the con-ditions required to get the best out of the setwith each.The P.220 is suitable where local stationreception at normal volume is the mainrequirement and where the nearest regionaltransmitter is within, say 25 miles. The

Pen 220 is a Pentode which will giveconsiderably more power for

the same input, andwill therefore

Complete setcf Telsen Componentsfor the "Songster" Two.

RADIO COM PON ENTs

Page 30 THE TELSEN RADIOMAG.

THE TELSEN " SONGSTER " TWO (cont'd)

increase range somewhat, as well as poweravailable on local stations, but in order to getthe best quality it is desirable to use a highimpedance loudspeaker, or a tapped chokeoutput filter, as in the Telsen " Commodore " 3.The detector voltage (H.T.+-1) is not critical,and any tapping between 6o and 8o volts will benear enough. Some variation in the strength ofreaction can be obtained by altering thedetector voltage.

At least ioo volts is necessary for H.T.+2 to getsatisfactory volume without distortion, and 120volts is better. The amount of grid biasapplied is very important, and depends on theH.T. volts. With the P.220 and 120 volts onH.T.+2, -41 volts bias is required. At 100volts, this should be reduced to -3, and itshould be remembered that when a 12o -voltbattery has "run down " to some extent it willbe necessary to reduce bias to 3 volts tomaintain good quality.

The Pen 220 has a fifth connection, which maybe in the form of a fifth pin or a terminal onthe side of the base. In the former case, afive -pin valve holder should be substituted fqrV.2. In either case the extra contact must be

TELSEN "SONGSTER" TWO.List of Components.

Quan-Descriptiontity

Cat.No.

Price

2 Valve Holders .. .. W.io5 1 02 .0003 mfd. Mica Con-

densers .. W.93 1 01 Grid Leak 2 megohm W.IoI 91 Aerial Coil with Selec-

tivity adjustment .. W.76 7 6I .0005 Bakelite Tuning

Condenser .. W.134 2 0I .0003 Differential

Reaction Condenser.. W.14o 2 0I 3 -point Push-PullSwitch W. 1o8 1 3I 2-pointPush-Pull Switch W.1o7 1 01 "Ace" Transformer,ratio

5-1 .. .. .. W.65 5 6I H.F. Choke X..75 2 0I .001 Mica Condenser.. W.96 6

£1 4 6Panel size 12 x 7 in.Baseboard size 12 x 7 in.

connected by a piece of flex to an additionalwander plug at 100-105 volts. The correctgrid bias is then 3 volts. Never adjust thebias or H.T. plugs without switching off theset, and especially when using a pentode.

Theoretical circuit of theTelsen Songster" Two.

00030003

HTtI

VALVES RECOMMENDED FORTHE TELSEN "SONGSTER"

TWO.Detector V.I. MAZDA L.2.

Output V.2. MAZDA P.220 orPen.22o.

O08+ HT- + LT -

RADIO COMPONENTS

THE TELSEN RADIOMAG. Page 31

Do yoÇconsideryour accessorieso

THE accessories used with a radio receiver playan important part in its performance. A poorvalve or a weak battery does not contributeto perfect reproduction.

The following notes on these essential accessoriesshould prove interesting to the home constructor.

VALVES.No set can be expected to do itself justice withvalves that are old or unsuitable. Although they maynot have deteriorated to a great extent, such bigimprovements have recently been made in thecharacteristics of valves that it is no exaggeration tostate that the performance of a receiver fitted withvalves eighteen months old would not be recognisableif fitted with a new set of 1932 valves. This appliesparticularly to the new Mazda range of 2 -volt valveswhich are recommended exclusively for the Telsencircuits. Since the 1932 range of valves were firstintroduced, ample opportunity has been afforded tomake extended tests, and Mazda have been selected"because it was found that they give definitely betterresults.The same remarks apply to the individual types ofvalve. There are often two or three choices ofvalve of one make for a given position in the receiver,and although some result may be obtained by anyof the possible combinations, careful selection afterextended tests is certain to give a more reliable result.

BATTERIES.However good the receiver and however good thevalves, they are both strangled if 11,ót supplied withproper battery power. To fit a ser with inadequatebatteries is a very false economy, and to let themcontinue in use after they have run down is to wastemuch of the time and trouble spent in building thereceiver-this is an aspect not properly appreciatedin many cases.

H. T. BATTERY.The H.T. Battery is very important, and it is herethat false economy is so often practised. An inferiorbattery may be slightly cheaper, but its useful life is somuch shorter that actually it costs more for worseservice. The same applies to using a good batteryabove its recommended discharge rate. The Ediswanstandard capacity battery is rated to carry up toto milliamperes, and is very suitable for the TelsenSongster Two, which when properly biased willconsume less than 1om.A. Long and satisfactoryservice may therefore be expected with this battery.The remaining Telsen circuits consume much more

OJ T

than to m.A., and this cannot be avoided if goodquality is to be maintained. (A possible exceptionis the Telsen Commodore Three when used with aPen. 220 valve). It is safe to say that the principalcause of the poor standard of quality suffered bythose who presumably have not heard better, isinsufficient H.T. A power valve which will giveadequate volume without overloading (which meansdistortion), cannot serve its purpose if there is alack of high tension supply.With these circuits therefore, the smaller type willnot give its proper life, and the inferior " standardcapacity" batteries which are usually useless over acurrent consumption of 7 to 8m.A., will only last apatter of weeks. It is, therefore, recommended thatthe Ediswan Heavy Duty type is used, which israted to carry zom.A. This will then be workingwithin its capacity and will give months of servicewithout excess voltage drop, loss of volume ordistortion and crackling, which are signs of anoverworked or run down H.T. Battery. 120 volts ismuch to be preferred to loo volts, the difference inpower and quality being well worth the extra fewshillings.

GRID BIAS.Maintenance of correct grid bias voltage is possiblymore important than anything, and as it is not aquestion of expense there is no excuse for not givingthe matter proper attention. A few volts error ingrid bias tappings will cause horrible distortion, mayrun down the H.T. battery in half its proper life,and in extreme cases may shorten the life of thevalves. The figures for correct grid bias underdifferent conditions are given on a leaflet with eachvalve sold, and these recommendations should becarefully noted. Where alternate figures are given,as " 9 -toy volts, it may be assumed that thehigher figure is the best one for economy in H.T.current and the lower for best volume and purity.This applies mostly to the power valve. The firstL.F. valve must also be biased to exactly the rightamount, but the economy question hardly arises-try both values given and use which sounds best on aloud passage. For S.G. valves, 11 volts bias isalmost invariably correct.The values of grid bias have been given in relation toeach circuit and from these it will be seen that a9 -volt battery will suffice-provided that the H.T.battery is up to its work. If an H.T. battery notcapable of supplying 2om.A. is used, grid bias mustbe increa d a little, and the next size bias batteryused. T ugh there is no current taken from a grid bias

RADIO COMPONENTS i//111111D/

Page 2 THE TELSEN RADIOMAG.

battery it will deteriorate in time, and taking accountof its low cost and the expensive results of deficientbias, it is worth while having the voltage of the biasbattery tested whenever the H.T. Battery is replaced,and if there is any doubt, renewing it.Suitable 9 -volt batteries are Ediswan 9 VG and9 VFG (which only differ in shape) and for thehigher bias voltages, Ediswan 15 VG.

ACCUMULATOR.A choice of two volt types is permissible but the" mass -plate " type has the advantage that it willstand up to longer periods without charging-acertain amount of overcharging and other forms ofabuse which it often receives. With regard to theupkeep, it should be taken at regular intervals of twoor three weeks to a reliable charging station whetherit is run down or not.For. the Telsen Songster Two, the accumulatorrecommended is the Ediswan " Little Loten,"which is adequate, but for the remaining Telsencircuits, the Ediswan CQ Loten Minor " or typeXG442 is advisable.

LOUDSPEAKER.Some choose their loudspeakers by price, some bysize, name, appearance, or even by the allegednumber of poles ! There is only one test whenchoosing a loudspeaker-hear it-at the same timeas the others under selection, i.e., one after the otherwithout too much delay. The set supplying thetest music should be free from distortion, and volumeshould be neither too loud nor too soft. Radio isbetter than a gramophone. Do not choose a speakerthat is too deep toned-it will soon become tirir*This is really a form of distortion, and it can becor>,more maddening than shrillness, which is the otherextreme. Choose the speaker that sounds the mostnatural, especially on speech. For an inexpensivecombination, it will be found very difficult to betterthe Telsen Loudspeaker Unit with the TelsenMajor Cone Chassis. Insist on hearing one. Itshould be mounted in a cabinet or on a baffle to gettrue results.

H.F.DetectorL.F. ..Output ..

THE TELSEN " EMPIRE FOUR "(cont'd from p. 26)

The use of the reaction Condenser and selectivitycontrols is exactly as described in the generaloperating instructions on page 23. Adjustment ofreaction will usually mean a slight adjustment in theright-hand tuning condenser, and adjustment of theselectivity control will probably necessitate a smallcorrection of the aerial tuning condenser.There is no object with this set in using a largeaerial, 5o feet is ample for all conditions, andexceedingly good results can be obtained on a smallor even an indoor aerial. In the latter case, it maybe found advisable to use terminal A.z. for theaerial. This cuts out the selectivity control and wouldonly be used when some distance from the localRegional station, where this extra selectivity wouldnot be necessary. A fuse holder has been fitted as arefinement to prevent the possibility of damageto valves or batteries through a short circuit orwrong connection. This must be fitted with a properradio fuse of the 6o or Ioo milliampere type. Aflash lamp bulb, though similar in appearance,is not suitable, as it will afford no protection to thevalves. If at any time the set should appear com-pletely dead, although everything else is in order,the fuse should be suspected and a spare one putin to determine whether that is the cause of thetrouble. Terminals are provided for use with aGramophone Pick-up, and further instructionson this point are given in the article on page so.

For suitable battery voltages, see table below.

VALVES RECOMMENDED FOR THETELSEN " EMPIRE " 4.

VI. MAZDA S.G.215V2. MAZDA H.L.2.V3. MAZDA L.2.V4. MAZDA P.22oA.

BATTERY VOLTAGES.recommended for the Telsen circuits.

Position. Songster Conqueror Commodore EmpireTwo. Three. Three. Four.

H.T.-{- 6ov. 6ov.-8ov. 50V. -80V. 5ov.-8ov.H.T.-!-2 I OOV.-I20V. 8ov.-r2ov. 6ov.-8ov. 6ov.-80V.H.T.-}-3 I00V.-I2OV. I20V. I20V.

3v.-4fv. I Iv. -3v. Irv. Iv.

G.B.-2 yv.-IOv. See text. 3V.

G.B.-3 9V.-IOÉV.

N.B.-The Telsen Electric Co., Ltd., cannot undertake to test or service home -built Receivers,and will not be in any way responsible for Sets sent in for this purpose.

MASTERPIECESTYPE PRICE

H.210 - 8/6HL.210 - - 8/6

t* HL.2 - - - 8/6L.210 - - 8/6

t*L.2 - - - 8/6t P.220 - - 10/6t P.220A - 13/6

P.240 - 13/6PEN.230 - 20/0PEN.220 - - 20/0PEN.220A 20/0

t 5.0.215 - 20/0* S.G.215A 20/0* S.G.21 SB 2010

* MetallisedtSpecified for the Telsen Circuits

LOOK FOR°EDDY" INYOUR DEALER'SWINDOW

Since 2 -volt valves were made, never has there been soamazing a range as this - so much evidence of brilliantengineering - so many valves with outstanding character-istics. Instance the Pen. 220; or pentode, which at oncepresents the solution to the output stage problem in portablesets, for it gives an astonishingly large output for a combinedscreen and anode current of under 5 mA. It is a valve H.T.dry battery users have longed for. It is typical of all Mazda2 -volt valves. Mazda 2 -volt valves, both metallised andclear bulb types, are sold by all good radio dealers.

THE AMAZING

MAZDA PEN. 220Characteristics : -

Filament Voltage - - 2.0 volts Anode Current (Max) - 12 mAFilament Current - - 0.2 amps. Screen Voltage (Max) ISO volts

Anode Voltage (Max) - IS0 volts Mutual. Conductance -2.5mA/VAt Ea - 100; Es - 100; Eg . - O.

PRICE 2O/0

The Edison Swan Electric Co. Ltd.

BRITISHVALVES

155 Charing Cross Road, London, W.C.2vi35

Printed by JAMES COND LTD., at 1-18-149, Great Charles Street, Birmingham, and Published by the ProprietorsTELSEN ELECTRIC CO. LTD. Aston, Birmingham England.