Questions and Answers

Radio Record, Volume VI, Issue 29, 27 January 1933, Page 20

Questions and Answers

"(VUALITY" (Devonport): I am not ; getting much satisfaction from my pickup, which I am using with a ninevalve set. The set is functioning perfectly, and the pickup was recently adjusted by a serviceman. Could the volume be increased by coupling.a transformer between the pickup and the set? I have tried: a 2-1 audio transformer, but without success, A.: Try a higher ratio, say 5-1 or even 73-1. Volume will be improved, but the tone will- suffer a little. 2. Is it likely that the pickup is eapable of greater output and needs attention? A:: Very likely. The pickup you are using is extremely sensitive, and is one of the best on the market. ai B.H. (Dunedin): I wish to use an * a.c. set in a room where there is no _ electric iron or heating plug. Is there. any legal method by which I can connect it to:the ordinary light socket, or wires? A.3 Yes, you may connect it at the ceiling rose, provided there is no switch on the set. 2. I wish to install serials in two different parts of the house, but using the same pole for them. Only one will be in use at a time, (See diagram.) Will this arrangement interfere with ‘the efficiency of either of them? , A.: No, but don’t earth the aerial not in use, , S G. (Bay of Plenty) : I recently erected ° a counterpoise aerial under my original one, which js about 150 feet high at one end, running down to about 50 feet, length 200 feet. The counterpoise I have insulated, but it is not earthed or connected to anything. Is this correct? A.: No, disconnect your ordinary, earth wire and connect the counterpoise td this terminal, ai O.N, (Ohaupo): I have a five-valve e American battery set which is fairly heavy on B current. It uses potentiometer bias in the r.f. stages. If I cut out the potentiometer and connect the grid leads to A-, what is the best method to control oscillation? ' A.: The present method is quite good for the type of set you are using, and to employ any other would mean drastic alterations, : ; 2. I have no negative bias on the audio "stages, because when I connect it up marked distortion and loss of volume results. Would this be due to the 90 volts B voltage being run down to about 50 volts? A.: Certainly it would. Bias is undoubtedly needed. Place about 3--44 volts on the first audio valve, and 6-Ov.. on the second. Also, your results would be improved if you used a proper output valve, say of the type B603. The heavy B drain taken by your set may be due to a partially broken-down by-pass condenser, This is a very common fault in the older American sets. I F.L. (Christchurch): Your present 4° aerial is quite efficient, and results would not be improved by erecting the twin wire aerial as you suggest. Me. X. (Wellington): L recently cover4t&. od the wire holding my insulators together with insulating tape, to prevent rust. Would this act as an earth? A.: No. 2. I have several Jarge scratches on my set cabinet. Could I hide them in any way ' A.: Any ecabinetmaker would provide you with a suitable filling for this. However, try filling them up with putty coloured with stain to match the cabinet, and then give the whole cabinet to coats of varnish,

aaa _ 8 About once a month my set. goes dead when switched on, although all valves light up, By moving the volume control backwards and forwards, the set suddenly bursts into action. A.: Probably a defective volume control. You could prove this by putting a pickup on your set to test the audio stages. B5™. (Nelson): The circuit you send "" of the short-wave adaptor is O.K., except that a .0005 mfd. tuning condenser is much too large for short-wave work. Try a .00015 mfd. T H.H. (Christchurch) : When my com- . 4¢ mercial a.c. set is turned on, and just when music is commencing to come through, the set seems to "backfire" (loud noises are heard for a few seconds). This occurs whether the set is hot or cold, A.: This may be anything, a faulty bypass condenser, resistance, audio transformer, ete. Take the set to the agents for servicing, "QHORT-WAVE" (Auckland): I wish to make short-wave coils. wound on ‘valve bases, for my set, which employs a 00085 tuning condenser. Could you give me the turns for primary, secondary and tickler windings? A.: You will need to use five pin valve bases. The turns are as follow :- Band Aerial. Grid Reaction 20 metres ceceee 2 4 4 40 metres ..o00. 38 10 6 80 metres ...... 6 16 8 ed H.S. (Waihi) : Could you give me the * specifications for short-wave coils using .00035 tuning condenser? I intend making 3in. diameter plug-in coils, using 18-gauge enamelled wire. A.: Follow the specifications given the above correspondent. 2. Where could I get instructions to make a three-valve all-wave battery set? A.: The Night Owl Three described in the "R.R." dated November JB, 19381, pDwNeco (Auckland) : Can earphones be used in the "Outspan Two" without alteration to the circuit?-A.: Yes, . Can four-volt valves be used with the "Outspan Two" without ‘alteration to the circuit?-A.: Yes. 3. Is the "Outspan Two" capable of getting results outside of New Zealand? A.: At. present the Australians should come in at good phone strength, while in the winter the set will operate a small speaker on these stations. You certainly cannot expect any more, Your ° aerial system is satisfactory. AR NORTH (N,. Auckland): Do you recommend Osram 22 valves for the "Outspan Four’? R A.: Yes.. Use 22’s rf. and S215 detecor, 2. The under baseboard diagram shows RS 2 meg., RO .1 meg., R10 5 meg., yet your parts list only shows 2 megs. and ow megs. A.: Do you not realise that .1 meg. is equal to 100,000 ohms? 3. This is R9. 4. C3 is shown on top of C4. [ take it that both are connected to R2? .: Yes. 5. Which one is earthed? A.: It is immaterial. It is better to connect your dial light direct to one of the filament terminals that does not go ‘through the rheostat. . . 6, The fuse is shown in the "B" battery circuit. A.: This is the correct place. ; i. is the bulb the same as for the dial ight ‘ wA.: Yes, both are 60 m.a. fuse bulbs. 8. Is the fuse affected by the altera-

a tions mentioned in the~ ‘December "Times" ?-No. . WwW R. (Wellington): My dial is mark-) *ed from 0-100. What do these degrees represent? A.: They are purely a relative division of the broadcast band and do not represent wavelength or frequency except indirectly. 2. Wellington comes in on 70 and Christchurch on 40. How do I get k.c.’s and metres? . ‘ A.: You cannot ¢alculate them from your dial readings, but you could quite easily use these two stations as’ guides, For example, Wellington is on 720 k.c. and Christchurch on 980. If you draw a graph plotting kilocycles or metres . against the dial divisions, you mark in these two stations and draw a line connecting them; then, knowing the frequeney of any station, you can read off the dial reading or vice versa. "sy, \

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