ANSWERS TO CORRESPONDENTS

Radio Record, Volume I, Issue 18, 18 November 1927, Page 15

ANSWERS TO CORRESPONDENTS

(By

Megohm

Browning:Drake, A Whangarei constructor has built the Browning-Drake 4-valve set and }: gets good results from New Zealand stations, but Australians only at ’phore strength. The valves used are not as specified, so that a little more trial and experiment must be expected before the best results are obtained, but that results will be good is certain. ‘The primary and tickler turns are important and are only found by actual trial, in the case of the primary to suit different valves from those specified, and in the case of the tickler the number of turns to secure oscillation on the high wave-lengths, which means increasing the number of turns until this is effected. The weakness of Australian reception appears to indicate a poor earth, and this matter should be investigated. ‘he dry weather is coming on, and no earth connection is better than one or two kerosene tins with connecting wire soldered on, buried down several feet where the ground is always damp. Coke placed round the tin helps to attract and hold moisture. The increasing loud note you mention is probably caused by microphonic valves set in vibration by the sound from the speaker, which canses ‘‘booniing.’ The remedy is to. turn the Bpeaker facing away from the set and not to have it too near, The valves specified do not give this microphonic trouble, R.L. (Christchurch) hooked up his Browning-Drake components roughly as a preliminary test and had _ surprisingly good results, both as to quality and volume. A few queries are now asked in connection with final construction. In the R.F. stage 201A is preferable to 199. A good combination for American 6-vyolt valves would be 201A, 200A (det.), 201A, and 112 or 171 power valve in last audio. Grid bias at 90 and 135 volts on 201A is 44 and 9 volts; on 112 for same voltages 6 and 9 volts, and on 171 for same voltages 164 and 27 volts. Loudspeaker Connections, S.W.A. (Waikato) finds that he la* been running his loudspeaker for some time with cotrinections reversed. Correct this and the plate current from your three-valve may slowly restore any strength ot magnetism that has been Jost, provided a choke filter is not in use, in which case no harm would be done either way. The clattering sound you have recently noticed may be caused by small pieces of paper or other foreign substance that has found its way in and rests on the diaphragm. All speakers should be cleaned cccasionally to get ¥id of such possible source of trouble. Liuff can accumulate in time sufficiently thick to muffle sound when the space between the diaphragm and top cover is very limited. Distance on Crystal. J.A.J. (Christchurch) gets poor reception of 2YA on his crystal set, nsing earborundum crystal. Reception is near-; ly as good without earth as with it. ‘he earth is evidently a poor one, and instead of using the water-pipe, bury a couple of kerosene tins with soldered connecting wire. SYA can be received around Wellington on the ‘Record’ erystal set with carborundum and no battery, but other conditions must of course be good for such distance on any erystal set. A Wellington listener writes to know why he cannot get LYA and 3YA on his erystal set on 2YA’s silent night. ‘The’ tuning coil of this sct is wound. upon u 34in. wooden former covered with celluloid, and then wound with 273 turns of 20’s enamelled wire, the length of coil totalling 10 inches. A coil of such dimensions should be equal to any contingency, but in actual practice 200 turns conld be dispensed with and the "dead end’’ losses caused by the extra wire would then be cut ont. The inquirer should make up the "Record" erystal coil as already described, 70 iurns, space-wouud on celluloid strips, using the wire he has. Wet the slider work close up against one of the strips. It could have a notch filed in to allow it to rest on only one turn et once. These coils ¢re more suitable for condenser tuning, in which case the numher of turns would be about 50. Reception of LYA and 3YA on a crystal near Wellington demands good conditions in every way, and much depends upon the situation, Searching for KEON. N.M. (Greymouth): It is impossible to give dialings for any particular set as" varying factors alter readings. KIFON. is on 233 metres, so would be on a low ‘reading, say about 20. KFON is three metres above Palmerston North’s wavelength, and considerably below the old 2YK wave-length, Changes of wavelengths are now being made in U.S.A., which will prohally affect a good many stations,