QUESTIONS AND ANSWERS

Radio Record, Volume V, Issue 12, 2 October 1931, Page 13

QUESTIONS AND ANSWERS

FRANK

KEE

The Technical Editor will, through these columns, be pleased to help readers experiencing trouble with their sets. Queries are limited to three-for more than this a shilling fee is charged, and a similar fee is payable for queries answered by post. Supplying layouts, circuits and solutions of intricate theoretical problems is beyond the scope of this service. A coupon must accompany all requests for information. Nonappearance of the coupon in any issue cannot be regarded as a reason for its not being used. Address all queries, The Technical Editor, Box 1032, Wellington,

t found its way to the laboratory. It appears, however, that you are getting fairly good results. You could use a shortwave converter on this, and we advise you to inquire from some of the better known dealerg to find out the cost of same, P#tTExYGOTUS (Dunedin): Your circuit is correct. It is possible that you have the connections to the detector coil reversed, and it would be well worth while trying them round the other way. If there is no improvement then revert to the original connections, If the adapter does not oscillate over the whole ranges, add a few more turns on the plate coil. You will find much to help you in the series of articles on the superheterodyne now appearing in the "R.R," A.T, (Kaitaia). We cannot pass any * comments about your set as one has 0 T. (Christchurch); I cannot apply °"B" voltage to my commercial six-

valve set. I have had transformers and valves tested, but when I use the set without bias the "B" battery runs down rapidly. There is no yolume. A.: Evidently there is a break in the grid circuit of either the first or the second audio valve. Have the secondaries of your transformers tested. Check between GB of your transformer and the "C" battery. You may possibly find a breakdown in your cable, Also check over the connection between "G" of the transformers and the valve, See that the valves are tight in their sockets. Go over the contact of the first audio jack, if it is present. 2. How is this set neutralised? ; A.: The serew type condensers are the neutralising ones, Commence with the third radio valve, that is the one nearest the detector by tuning in to a station on about 8YA’s frequency. Remove the valye and cover one of the filament legs with silk or tissue paper to prevent it coming in contact with the socket. Replace it in

the socket and adjust the balancing condenser nearest it until the signals are at minimum. Now take off the silk, replace the valve and repeat the performance with the two other valves. The two midzet condensers are to balance up on the main tuning condensers. You merely tune to a station about the centre of the dial and then adjust the two midgets until the loudest volume is obtained. In this case the valves are left in a normal operating state. 3. Where do I connect the earth-wire. as there is no earth terminal? A.: To the "A-," "B-" and "C+" connection. B.S. (Wakefield).-Your question is e outside the scope of Questions and Answers. Wxplaining how to obtain and control regeneration on & commercial receiver ig the job of an expert, and the chances are that even if we told you what to do you would not get satisfaction. In the first case you would throw the condensers out of alignment, and that would offset any gain brought about by regeneration, Often you can make a set of your type oscillate by ,carefully balancing the condensers, R DIO (New Plymouth).-What is the "capacity of the midget condenser in the aerial circuit?-A.: .0001 to .00005. 2. Why should I not arrange the set for complete sub-panel mounting? A.: There ig no reason whatever. If you depart from the layout, see that you get the vital wires short. 8. Why are the shorting condensers used across the .0001 condensers? ‘A.: In order to use the set for broadcast or short-wave work. When the .0001 condensers are in the circuit the effective capacity of the tuning condensers is reduced to about .0001, and this is admirably suited for short-wave. When the condensers are shorte@ out they assume their ordinary capacity. Am (Wanganui).-Your queries were an7 swered in the "R.R." dated September 1 E H.L. (Waitara).-No doubt power ine terference is causing the trouble about which you complain. It is strange, however, that you can use your set in the power-house and get better results than you can a few hundred yards away. he power-house may be shielding the transformers to some extent, or it may be & case of "skip distance." Take off the aerial and see what happens then. If the noise persists, perhaps to a less degree, install the filters. Better results can probably be obtained by using shielded cable for the down lead and earthing the shield to a separate earth. HIBLD (Auckland).-I have a power pack delivering voltages from 45 to 300. Would this obviate the use of resistance in the 2.c. s.g. short-wave set described in the "Radio Guide"? A.: You could take the lead direct, but it is far better to make the set exactly as deseribed. By using long separate leads you are Mable to get back coupling and ether unsatisfactory results, 2, Could my variable condensers of .0002 and .00045 be used with fixed condensers to reduce the capacity? A.: Yes; a .00083 will be required in serjes with .0002 to reduce the capacity to .00005. The .00045 to be made suitable for the tuning circuit will need ,00022. $3 Could push-pull amplification be eect-

ed using an ordinary audio transformer as input with resistances between the grids and cathodes to earth, and a tapped chore as output? A.: Yes; the arrangement should work satisfactorily. EMO (Masterton).-Would it be a big improvement to the H.R. set to incorporate a stage of r.f.s.g.?-Yes. 2. Could you Jet me have "Detector’s" address to find out what results he obtained? A.:If you send a stamped and addressed, enveloped for a reply we shall send it to you, ALCON (Remuera).-Is there any way in which I can convert my seven-valve battery receiver to an all-wave set without the use of an adapter? A.: There is 20 practical way of doing so. We advise you to use the adapter. 2, Would I be able to bring in Hngland, ete., on the short-wave? A.: If your adapter is a good one, yes, 3. I am using 201A valves. Are there any other suitable valves? A.: Yes, the new 221’s are up-to-date 201A4’s, P.O. (Bluff)-Would my reception bg e improved if I erected another 40 t@ 50 feet pole alongside the house? The present aerial slopes down to a point where the lead-in enters the house 16 feet from the ground. ‘A.: Decidedly yes; it is unwise to glope your aerial down to the point where it enters the house. Always use a second mast. ECHPTIONISE (Wellington): Wouia converting my aerial from an "L" type 80 feet or 90 feet top span to a "TE" make it more selective? A.: Yes; it would shorten its effective length to about 40 feet plus the lead-in, thus reducing the pick-up. 2. What type of earth do you Fecommend when using a set on the second floor? A.: It depends, If you are near the sink or water-tap, connect to that, Otherwixe

DUDACUESUPYOCES ALGAE T AEE Information Coupon (To be used with all requests for information.) Name of set ...... eee eewevesavenes Number of valyep cccocvcescsscecenes Name Address Soe oeeoeeos sooo eGOSGSGSbOaee COSCSCHOOHOGGOOTeSOBOSORSEOF FOS ORSSOOTCOOSHDOSIOSCSSHPRAGSABOOHSERS POPS OE HOH SESE SOHEHEOHHOOCOTHSOSOORSSHORS NOM Ge DPIUME cpesgeovesecsencers To be kept in subsequent inquiries Date cacaccerecccceenss oavees. Please Note :- (1) Be specific and brief, tabulating, if possible. (2) legibly, and on one side of the paper. (83) We do not design circuits, but accept suggestions for feature articles, PEOUEALACSRSUADSESLUAESEDUSEACCOURELEREIED

run a lead of 7/22 wire by the shortest route to the ground. K™ (Waikato) -Can you refer me to an "R.R." with instructions for building a simple four or five-valve superheterodyne set? A.: Such has not yet been described. One will be described in the very near future. 2. Could you recommend suitable valves, with four-volt filaments, that would suit my present set? They must be suitable for a super-het, later on. A.: Sereen grid valye E4428, for ordinary ac, valyes, 1400. Output valve, B443. J ENTY (Kopaki): Must "B" accumulators- be discharged before adding new acid? What is the specific gravity of the new acid? A.: On the contrary they must be fully charged before doing anything to them. You add new acid until the specifie gravity reaches 1250. 2. My cells show full hydrometer test. but no meter test .and they discharge very quickly. A.: There is a defect in the battery itself. The fact that the specific gravity is correct does away with any trouble arising from the solution... Your best plan would be to have the-"B’" accumulator overhauled by an expert. 3. The plates have blistered. Do thes¢ need replacing? A.: We think that your accumulator is coming to the end of its useful life. When the plates begin to blister it is nearly time the accumulator had new plates or was relegated to the scrap-heap.

HILLTOP (Wellington): My four-valve A.C. set is humming badly. Could this be overcome by smoothing condensers? If 80, of what value and where should they be inserted ? A.: Hum may be due to several causes--ie, see the article in the "R.R." on April 10 on tracing hum in A.C. receivers. We advise you.to read this article and make the tests suggested. If you cannot trace the source of the hum the best plan will be to take your set to an expert. P.U. (Auckland): How many turns of * 26 d.s.c. on a 2-ineh former will b* necessary for the r.f. coil of the "Ranger Three" if.a .0005 condenser is used? . A.: If you will refer to the artiele iv anestion vou will see the information giv: there, The tapping for the aerial will b brought in three tyrns lower than for th 000385 condenser. The usual value for a neutralising condenser is about .00005. Just ask your dealer for a neutralising con denser and you will get the right thing. TRINOA (Kaikoura): My _ telephone picks up signals from a wireless set even when the receiver is down. Can you explain? A.: The signals are being picked up either from your aerial] (a type of reradiation) or from the earth. Altering the direction of the aerial and installing a different earth would probahly have the offect of overcoming the trouble. 2. Your combination of valves is good. You might, however, use the 221 type of valve instead of the first 201A. 3. Would an extension of 70 feet with earphones to a whare have any detrimental effect ? A.: No: but it would be advisable, to instal an output filter comprising an ontnut transformer or a choke and condenser between the set and the lead to the whare. GtATIC (Westport).-We regret we do not have blue prints. of the "Outspan Five." Full details were published in our issue of February 20, and have not been repeated or elaborated in any way. IRDELESS (Oamaru).-Where could I obtain a short-wave adapter for my six-valve battery set? A.: A suitable short-wave adapter was desertbed in the 1929-80 "Radio Guide." You could have this made up or you could obtain a commercially-made short-wave adapter. Of these, the Add-phone is the only one tested, and it has been found entirely satisfactory. . 2 What are the particulars of the DX Clith ? A,: We are sending on to you a cireular telling you all about it. 3. Could you tell me how to fit earphones to my set without disconnecting the speaker? ‘ . A.: You connect them to the two terminals now going to the speaker and use a small spring to grip the phone terminals, or you can just wire them on in some way.

AMATEUR (Auckland): Would A413 be / suitable for detector and 8B405 for, ( power-valye in the "Night Hawk Two’’? A.: A415 will be quite suitable for de- N, tector. B405 would make a good second valve. You could, however, use A409, if you wished. 2. Could you give specifications for one broadcast and. three shortwave coils for this set? A.: They have all been given in the "Radio Guide." : ~ 3. Is it preferable to have the lower end of a sloping aerial toward or away from a station.one wishes to receive? A.: It is immaterial, H H.M. (Dunedin): Are the coils for the -° "Sparrow Hawk" one the same as for the Differential series ?-Yes. 2, How would I add an extra stage to the "Sparrow Hawk" one? A.: An extra stage to the "Sparrow Hawk" one would be the same as the "Differential" or "Night Hawk’ two. K A.D. (Kelburn): If I added a second e stage of audio amplification to my erystal and valve (with three-valve performance) would the result be old-fash-ioned as compared with the "Differenpial Two" and "Night Hawk Two," ete.? °b A.: No; you would have a really satis, factory set. Certainly the swinging coi method of obtaining reaction has gone out of date, but it has yet very many good points. 2. How would I connect up the extra transformer, 34-1 and valve? A.: You take a wire from the plate terminal of the valve now in the set to "P" of the transformer, ‘"B plus’ of the transformer you take to the detector voltage,

whatever that might be, or to the voltage that was applied to the other phone terminal. "GQ" of the valve is carried to the grid of the extra valve and "G.B." to the negative of a suitable "B" battery. "B plus" is connected to "A minus’; you take "A minus" and "A plus" to the valve socket; take the plate to one terminal of the phones. The other terminal you connect to the highest "B plus" voltage available. A diagram illustrates these connections. 2. Could I use a screen-grid valve for my second valve? A.: It would not be satisfactory to do so. You would have to employ resistance capacity coupling, and this would offset any gain due to the extra lift in the sereengrid valve. 19 (DUNEDIN): Could I use the new 230 valve with 231 in the last stage of the Radiola 20? A.: You may have some trouble with the neutralisation, but once it was. balanced up it would certainly be an improvement. 2. Would these valves operate on an eliminator successfully ?-Yes. 3. Is it necessary to make any nadition, or alterations to the set? A.: No, only ineorporating the six volts "A" battery and the re-neutralisetion. In last week’s issue we described in Questions and Answers column how to neutralise a Radiola 20. . SCILLATOR (Caversham).-By employing a .0001 mfd. double spaced tuning condenser in the "Sparrow Hawk" tue, how many turns will be required for the short-wave coils? A.: The same as specified, , 2. I have a 80 ohms rheonstat an honi, Could I use this instead of a switch in the "Sparrow Hawk’’ One?-Yes. LEBEL: (Christchurch).-My power pack delivers 90 milliamps at 300 volts, Could I use a speaker drawing 110 mils at ae Volts d.c.? : We would not recomm s fs om 4° to use this speaker with your power pack. You will burn something out. toe better plan would be to use one of the type that will operate direct from the mains.

AST HOPH (Nelson).-I wish to wind a ; broadcast coil on a Colvern former. is to tune between 200 and 700 metres. What are the numbers of turns? A.: You have not told us the capacity of the condenser or the size of the wire you intend to use, — 2. What is the better valve to. use-a 201A or a -- valve? A.: The second valve is really 201A. You have really named the maker, who is licensed under R.C.A. patent, and consequently makes the same types of valves. L C.B, (Wakefleld).-The circuit which ¢ you enclose would give about the same results as the "Outspsn Five." A gereen grid valve as detector should be followed with resistance capacity coupling as deseribed for the a.c. Advance shortwave receiver in the "Radio Guide." We pub-

lish herewith a sketch showing the connection for a s.g. detector. 2. Will the coil data of the "Night Hawk’ be suitable?-Yes. If you use a .0001 condenser, if for short-wave only, or follow out the directions given for allwave operation. 8. Can I use differential reaction?-Yes. R EH.McF. (Ngaruawahia).-I am troubled e with a persistent crackling. A.: This is either a broken down transformer, a loose connection, or a short circuit in the B battery. Your valve combina-

tion would be improved by the use of a B605 type of valve in number 5 socket. It should be properly biased, say 9 volts. Otherwise your combination is quite satisfactory. 7 IGMA (Auckland).-I wish to reduce a .0005 condenser to a .00025. How many plates must I remove. ; A.: If you want to remove plates take out half of them. A better plan, however, would be to use a .0005 fixed condenser with the existing .0005. B. (Murchison): Your circuit is not e quite correct. You will have to place the milliammetre between the plate of the valve and p of the valve socket. ‘The best size for a milliammetre is 0-10. You could arrange shunts to give you a wide range. IZ, you do not want to do this you will

find a 0-50 the next best size, If, however, you wanted test valves with a low consumption 2 0-10 and using a shunt for bigger currents, "FRURO (Auckland): Would it be possible to still further increase the volume of my set by increasing the length of my aerial? A. : Yes. You will probably get greater signal pick-ups by using a longer aerial, but the chances are the selectivity would be very much impaired. We are sorry your query was mixed up with someone else's, but these things happen even in the best-regulated services. We will not charge you the shilling for the extra six questions. . MATINUR (Dunedin): We regret we eannot give you short-wave coil specifications for the "Ranger Two." It is a broadcast set purely and simply. You could probably find all the information you wanted in the coil tables published in our issue of April 15, 1931. If you wanted an all-wave set why did you not build the Night Hawk two, for which all coil specifications were given? K.M. (Glen Matthew): I operate a e four-valve all-wave receiver which refused to function. On making an examination I found that an audio transformer had burnt out and the detector coil was charred, necessitating having it rewound. Strange to say, the valves were in good order. Upon replacing these components the set was again normal. A.: That is more than we can say, as only a careful examination of the set would reveal the cause, but possibly a short circuit occurred between the plate of the detector valve and earth. 2. How would I eliminate a deadspot on a 50-metre coil? A condenser is seriesed with the aerial, and I have alsotried varying the voltage on the detector, but without success. . A.: For the moment we cannot recall if your set has a separate primary or not. Tf it has, take off q few turns, If not, try. 2 different condenser in series with the aerial. L W. (Caversham): I have been told * that hand capacity is very bad with the differential series. Would employing a metal panel and sub-panel remedy the said defect?

A, : Although we have seen many of the differential sets, and worked several, we have never experienced this difficulty, and are inclined to think that it is due to the particular set built up, not to the circuit. Certainly employing a metal panel would remedy any tendency toward hand capacity. oe 2. Will the RF choke be suitable for th short-wave band as for B.C,? © .. A.: If you get an efficient choke, yes. J.C. (Manurewa): When. I connect: my e ghort-wave adapter to the set it squeals if the filament voltage igs at’ all nigh. P A.: This ie due to there- being. too many turns on the reaction coll. Reduce this number until the oscillation in the set is controllable. Try reversing the connections to "Aj." and "A-" on the adapter. . 2. Would the aerial as shown in my sketch be satisfactory? A.: Yes, you are showing considerable ingenuity with the proposed aerial, and it should give you very good _ results. However, by making it longer you would certainly get stronger signals, and would be better if you could raise the ‘back pole to 50 feet. D 8. (Auckland): Some time ago you e published particulars of a wavetrap suitable for 1YA. Where could I obtain a copy containing these details? A.: You eould build up the wave-trap described in this year’s "Guide," but use another formodenser instead of the fixed condenser. 2. Would the wavetrap deseribed in the issue of September 4, and which is described as being suitable for QYA and 2ZW be quite satisfactory in Auckland? ; A.: That is more than. we can say, as the number of turns are designed to suil the two Wellington stations. However, you could use the particulars given there as 2a basis for experiment. We see n0 reason why they should not be correct, as you have a formodenser which you can adjust for best results. C W.T. (Dunedin): Will the dual wavee trap described recently in the "Radio Record" be quite satisfactory for cutting out the local station while tuning for distant ones ?-: Yes, you may have to make some small alterations in the number of turns for your particular requirements, and _ the particulars given will certainly make a good basis if you are experimenting. 2. My present aerial is 25 feet long by about 15 feet high, I intend putting another one 80 feet long and approximately 50 feet high at one end, and 2 feet at the other. Would this be satisfactory for shortwave work? A.: Yes, It would be a decided improve ment over the one already in use. 3. In the diagram of a wavetrap you give a 2in, former. Could you give me the specifications for winding with a 24in, former? A.: The difference is so small as to be negligible. Keep the number of turns the same. We are pleased to hear the "Ranger Two" is giving satisfaction. Ié is no doubt a good little set. Batt (New Plymouth): Will the superhet circuit shown in the "Radio Record" of August 14 work on a B.D. set soumected direct to the aerial terminal.es. T.C. (Waipukurau): Are there any » gll-British sets on the market ?-Yes, the Ultimate-an all-wave set, the Cossor, the Rodges, and certain models of the Fadiola-45H, and others. MPERITH (Taranaki): I have con-’ structed the "Differential One" but am not able to make it oscillate. The tuning condenser has nine moving and eight fixed plates, the differential . condenser being .00015. I want it primarily for shortwave, but as yet -have not constructed those coils. A.: Try reversing the connections to your reaction condenser. It sounds very much as though they are back to. front. If this does not produce any result, increase the number of turns on the reaction eoil. 2. Would it be possible to receive Hngjand on the ’phones with the "Differential One?" A.: This would depend upon . your locality. It has been done, and there is no reason why, if you are in a. good locality, it cannot be done again... ssi

8. Is the circuit I enclose better than a erystal for volume, and what would be the size of the coils? A.; The circuit is not an orthodox one, and we cannot tell you very much about it, It should be much better than a crystal. We have no data as to the coils, and.think it would. be far better to use one of the recognised valve circuits, These fancy circuits are all right up to a point, but that point is usually pretty restricted and they don’t work. N®" OHUM (Taumarunui): I have a commercial radio set and I find that night reception is quite satisfactory, but during the day it is very weak. What can I-do to correct thie state of affairs? .- A, : Nothing; daylight reception is -ailways very much worse than night reteption, In-many districts it is almost ‘impossible to- hear anything during the daytime and you appear to be in one of these. LXer (Waihi): What are the resistance and condénser values in neutralisers, such as: phasatrols? : A. :.In a phasatrol the resistance is 2000 ohms, the condenser (usually) .06 mfds. 2. What is the formula to find the -voltage drop across a lamp or resisbance ‘a8’ in say a 230 volt 50 watt lamp? a A.: It is worked out by Ohms Law. Firstly in the case of the lamp you must find the current passing. You know that a watt is equal to a volt multiplied by an amp, therefore 50 watts must represent:the number of amps, multiplied by 280 volts. This is equal to roughly .2 amp. Now ‘we have amps flowing, we have the voltage drop, therefore we can find out the resistance. R-e.i., 280 divided by .2 is 1115 ohms. ‘The voltage drop across the resistance can be calculated directly from ohms law, in the same-way as we worked out the last part of the lamp:equation, that iss R-

When "R" is the resistance, "‘e"’. is 8 emf. dropped and "i" the current passing. 3. When neutralising s.g; and ordinary rif, valves is it correct to tune out a signal when the filament is disconnected and the reaction off? A. : Note quite. In the first place you do not neutralise a screen-grid valve and secondly, when you are using a set employing reaction, neutralising is done as was described recently in the "Ranger Three" article. L D.M. (Feilding): I have a modified e Pierce earth system employing five wires leading directly from the terminal of a lightning arrester. Would it be a better proposition to run one wire from the arrester and branch down near the pipe? A. : There is very little difference in the efficiency of both these earths; probably the first is the better; you have a lower resistance between the lightning arrester and the pipes than when you use the longer Single wire. ve VALVE (St. Albans): Would I get a better bass reproduction if I use a baffle on my speaker ? A. : Yes, a baffle would tend to bring out the bass notes, but your speaker is not particularly adapted for use with a baffle. However, if-you could manage to fit behind one, so much the better. The bass notes are not always due to the speaker alone. They, to a very large extent, depend upon the amplifier used in the set. A J.B, (Waikino): Would two variable e condensers of.00016 capacity with two -0002 fixed condensers in parallel do for the "Kestrel Three" ? A. : No; they would be more or less satisfactory without the paralled condenser for the short-wave but, if you use the parallel condenser for broadcast you would find that the band would not adequately be covered. You see you still have a residual capacity of .0002, whereas, if the condenser were acting normally you would have less than .00005. This of course, prevents you covering the band. D*2.W. (Tasman.): What would the, aerial sketched out be like? It runs from the top of a cliff about 200 feet high down to the beach? A.: The aerial would be quite satisfactory. It might be better however, if you eould get another mast up on top of the cliff and have your aerial running in its entirety along the top. It will be interesting to get this other aerial up and then compare them. 2.: The gauge of wire enclosed will be quite satisfactory for wiring your house. tis about 18 d.cc. If, however, you want to move speakers about it would be safer to use an output filter at the set itself, and then you could use fine wire for taking the leads round the house; 24 or 26 gauge would not be too fine. 8.: Is a set harmed when turned on without the speaker connected up, and if the speaker and phones are on the first jack, does it mean that the second audio is not using any current? A.: It does not harm the set to have it operating without a speaker. It all deends how your set is wired whether the ast valve is cut out when you use the first stage jack. In most outfits, the first jack euts out the last valve. If your circuit is the popular kit set type, then it will be cut out when the first stage is used. Your other point will be answered in the "Diagnosis of Radio." X2A (Auckland): Drop a note to the Technical Engineer, "Radio Ltd." Anzac Avenue, Auckland. He will probably supply you with the circuit for which you ask,

Vounsdn (Hawke’s Bay): What will be the best combination of valves to use in my five valye American battery receiver? A. : Use four 221’s and B605 in the last stage. If you use 605 in the last stage it must be suitably biased, Make quite certain that you have provision on your set for a "C" battery. If there is not, then it will be in your interest to have one put in. It is only a small job. Rocee (S. Canterbury): What adaption should be made to the "Knife Hdge Rejector" described in the 1931 "Guide" in order to discriminate between 4YA and A.: Those two stations are on frequencies very close to one another, and it is douhitful if you can get them cleanly separated even with a wave-trap. Your best plan would be to make up the "Knife Edge \sdndendndandondondaderkaubendocdonkeaenharderhadedadedededadadadad Akedodokedadodedetdokalas

Rejector," but using formodensers in both places instead of the fixed condenser recommended. The formodenser, which costs about 2/6, can be adjusted to suit any capacity required. It is not possible to use a wave-trap for more than one station, unless something more elaborate is made, such as the dual wave-trap described a few weeks back. Selectivity can often be improved by inserting a fixed condenser of .0002 or .0003 in series with the aerial. Awt4* (Roslyn): American stations can be picked up usually between 4.80 and 7.30 p.m. For more particulars see this month’s "Radio Log." P. (Gisborne): I have recently cone structed an electric set, but cannot get it to operate when I use an aerial inside an iron shed. If I disconnect the earth and connect the shed to the aerial terminal, I get more or less satisfactory results, but the stations are somewhat weak. A. : This is quite understandable. The fact that you are using an aerial inside an iron building and not getting results is due to the iron building shielding the aerial and carrying the radio waves to earth. When you cannect the iron shed to the aerial terminal, it now acts as an aerial. You can often get very good results by conecting the ground wire to the aerial terminal and leaving off the ground. In fact we prognosticate that, within a very short time, the new sets will be doing this, so abolishing the outdoor aerial. If you erected a good outdoor aerial and installed a good earth, probably your troulles would disappear. S.D. (Palmerston North): I have an ac. e receiver about 24 years old and am using four 226 valves, one 171 and a 227. Is this a good combination? A. : It is as guod as your set will allow. You could not use a different combination of valves. It is preferable, however, to have them all of the same make. 2. The earth wire is about 4 feet long, connected to a galvanised iron pipe driven 2ft. on, in the ground. Is this satisfactory A.: Yes, It may be improved by sinking your pipe a little farther in the earth and keeping it moist. Parths were very fully discussed in an article published about 12 months ago. EGINNER (Auckland): I have just erected an aerial 30 feet high with the poles 50 feet apart. I find that I get no better results from the aerial than from a coil of wire alongside the set. I get slightly better results by using the earth wire. A. : Obviously there is something wrong with your aerial installation. If you are using a lightning arrester in the set, take it out. and then try it. If your aerial is on pulleys, let it down and check up on the insulators, to make quite certain that there is not any leakage to earth. Have you checked over all joints to see that the wires come into electrical contact with one another? Many people, in erecting an aertal, forget to serape the enamel from the two wires they are joining.

Novice (Takapuna): I wish to replace the valves in my set. It is at present using 226’s in all stages except the detector, rectifier, and last audio. I see that these are out of date, Are 'there any others that I can use? . A.: We are afraid not. Your set is designed for the 226 type of valve, and you must use these in all stages except the detector and last. We advise you to replace them, as you have had the set some time. Try first the rectifier and see if that makes any difference, If not, replace them all. oy W.B. (--): I am using a four-valve e Browning Drake and have re-neutral-ised it for a PMS5X, which I find more sensitive, but I cannot stabilise it below 8Y¥A. Should I remove turns on the primary coil? A, PMSdX is quite a suitable valve for the Browning Drake, Generally speaking the number of turns is the same as for the 199. Try a 2 mfds. by-pass condenser between the bottom of the primary coil and the earth. Place the condenser as near the coil as possible. It may be wise to use an r.f. choke between the point where the condenser joins the "B plus" r.f. lead and the "B" battery. This failing, you may slightly reduce the number of turns on the primary coil, as this always has the effect of making the set more stable, 2. Is it possible to switch out the r.f. valve from the panel to avoid taking it out? I have a separate rheostat for it. If so, what would be the connections to the push-pull switch? A. If the rheostat will not cut the valve out of the circuit (a rheostat can usually act as an off-on switch as well), take one of the connections from the rheostat and connect instead to the push-pull switch. Connect the other side of the push-pull switch to the rheostat. N Z.107W (Wellington): Would you supLN o ply the correct number of turns for .0005 condensers with .0002 differential condensers, to be wound on a valve base? ANSWER TO COME 3333s -2. Should a set squeal on the point of oscillation ? A. If there is a station there it will howl when it is doing this. If there is no station there the trouble is known as fringe howl, It is very annoying and makes tuning difficult. I*’rom the sketch of your layout we think that a lot of the trouble is being caused by your having a twocircuit jack on the front panel and also through taking leads from the .0001 condenser used in series with the tuning condenser on to the panel, Stray capacity is always likely to be caused by long leads, particularly with the double-circuit jack. The use of these is not at all wise unless arranged as Mr. Sellens has done in his shortwaver. Iiven then the leads must be kept very short. Is the "C" battery apart from the set itself? If so, then you have a long straggling lead from the grid return. Bring the grid bias battery into the set itself and so shorten the grid circuit. The use of a $mfd. condenser across the "C". battery may possibly help, but the best plan is to bring this battery right into the set. . 3. Could you furnish working instructions for building a moving coil loudspeaker? A.: These were published in the "Radio Record" some years ago, but unless you are very lucky you will not be able to get a copy. If you call at our office and ask to see the file copy, it is possible you will be able to jot down particulars sufficient for you to be able to make up the speaker. FOXY (Wellington).: I have a commer-cially-made a.c. receiver. What valves should I replace my present ones with when they are done? A.: We cannot tell you, as you have not stated what make your receiver is. With a.c. valves there is very little chance of variation. You must replace the valves with precisely the same type, though you may select a different make. For instance. if you are using 226 type valves, then you must replace your present ones with these. though you can use any of the several makes there are on the market. However, keep to the better-known makes, as it is not wise to use just anything in the way of valves.

2. What would be the cost of having hoody hones attached to my set? ‘ ery little. If you did the job your ed self-and the instructions were given very clearly in the "Radio Record" a little time back-the cost would be less than 10s, However, phones would not enable you to reach out much farther. What you cannot hear on the speaker with an ac. set, you rarely hear on the ‘ones, Atmospheres and set noises usually manage to drown out weak signals, MPOT. (Rangiora).: My set has dead spots over the larger portion of the dials. Could you tell me the cause and remedy ? A. Dead spots over the greater part of your dials, in a set such as the Browning Drake, are caused usually through a defective valve or through the condenser vanes touching. DWxamine your radio frequency and detector condensers very carefully, turning the vanes in and out through their whole circuit. Watch carefully to see that the vanes do not touch at any place. 2. What type of Philips valves can be used with 135 volts "B" and 6 volts "A" for a four-valve Browning Drake? A.: ist radio A609, detector AG15, audio A609, power valve B605. The last valve must be biased by 12 volts. NZAC (Christchurch): I have recenS replaced the valves in my set and nt the first time have heard three Americanf stations faintly. Is this district bad for reception ? A.: Some good logs have been put up in and about Christchurch, but as localities even adjacent vary greatly it is impossible to say if you are getting good results. It seems as though, for the type of set you are using, you are not doing at all badly. 2. Our one pole.is 40 feet high with an 80-feet aerial direct to the set. The earth consists of a 9-feet iron pipe sunk into shingle. There is an entire absence of soil. Can ~~ improve our installation in any way A.: Yes; erect another pole. It is not a good practice to have one mast and bring the aerial from that directly down to the set. If you had another mast 40 feet high, then brought a lead in from that to the set, your results would be very much improved. Furthermore, where you have shingle it is impossible to get a really good earth unless you go to some trouble by earthing an old copper or by driving several pipes into the ground six feet apart. Dress the surface near where the pipes are buried with salt and keep well watered. 3. Our set has blown two condensers in the last eighteen months, Is there a fault somewhere? A.: Yes. The condensers are not of a high enough break-down voltage, It sometimes happens that the original condensers in the set break down, but if higher test condensers are put back in the set the trouble should not re-occur.