RADIO AND ITS RECEIVERS

Sun (Auckland), Volume III, Issue 819, 13 November 1929, Page 14

RADIO AND ITS RECEIVERS

Conducted for THE SUN by

R. F. HAYCOCK,

STRANGE EXPERIENCES

; FLAME AND SMOKE IN SET • V ALVES GLOW WITHOUT BATTERIES One evening last week I was using . a short-wave set which was functiou- : ing quite satisfactorily. Suddenlj’, • there was a flash of blue flame, smoke rose in the air, and I received a shock on the head from the head- ! phones. With visions of three good | and expensive valves having ended their career, 1 hastily switched oft i the set and made a most minute exi amination of it. Nothing appeared ! to be out of order; there was no sign of anything being burned or scorched and the battery leads were as they j should be. In fear and trepidation in case of a similar happening—l i switched on the set again. With feel- ! ings of relief I found the valves were | working and the set functioning. ] though there seemed to be a little less j reaction available. I cannot say definI itely what occurred, but assume that j lightning was responsible. When the above was related to a well-known Auckland radio mechanic i he said I was lucky, as a man he knew i in the country had a set in which the ! valves lit up when no batteries were j attached! I T expressed astonishment, and he said the valves would light even if no j batteries were in the house. Seeing | my astonishment, he said that the set j was within 40 yards of a power i transformer, and despite the power ; board's assurance that the transj former was not. out of order, the j transformer was the cause of the j phenomenon. ' The same set. added my informant, j when taken to another district ‘ operated perfectly, and required bat- | teries before the valves would glow. The glow of the valves when the ! batteries were not attached was not sufficient to permit of the set being operated, otherwise the owner might have had cause to bless, instead of curse, his nearness to the power transformer. I wonder if any Sun readers have , had similar experiences to the above. The wireless station which is being j erected in the Vatican City for the use of the Pope, and the Vatican State, will embody the latest improvements, and will rival many commercial installations. Communications will be carried out by both telegraphy and telephony on all wave-lengths, including short waves. It is understood that the equipment will include a beamtype transmitter and receiver, and will have a world-wide range. i

PROGRAMME ORGANISER MR. WRATHALL OFF TO DUNEDIN Mr. Dudley Wrathall. programme organiser at IYA, has been transferred to 4YA, Dunedin, and his place will be taken in the meantime by Mr. O. Pritchard. Mr. Wrathall, during his long period of service has made himself very popular with performers, and it is largely due to his ability as an organiser that the programmes have reached the present high standard.

Mr. Wrathall is not only an organiser, but a singer of no mean note, and has greatly pleased listeners on his many appearances before the microphone. On numerous occasions Mr. Wrathall has given his services at local concerts, and his departure for the South will he a distinct loss to musical circles. FADING PROBLEMS An attempt to overcome the difficulty of “fading,” in tlie reception of j signals from distant stations, is being tried out by the British Broadcasting ! Corporation. Transatlantic programmes ! are being picked up by one station j in England at Terling, near Chelms- : ford, and also by another station at ! Keston, Kent. These two stations are I linked by land lines and each of them picks up the American signals on three different wave-lengths. The idea is that if fading affects one wave-length, both Essex and Kent will receive it on the other wave-lengths used at the same time; while if local conditions are affecting it at Terling, I Keston will carry on, or vice-versa, l j the two combined maintaining a satisfactory level of programme strength.

DETECTOR DISTORTION For small detector valve output voltages grid-leak and condenser detection has been shown to cause a loss of the higher frequencies. The input impedance of a detector valve is fairly high even when the grid-leak is brought back to the positive side of the filament, so the higher frequencies are shunted to ground by the grid condenser will lessen this effect. However, and a .0001 or .00005 mfd. grid condenser will lessen this effect. However, the loss in overall signal strength is quite noticeable, and an additional stage of r.f. amplification is generally necessary to make up for it. This method is not recommended lor a receiver whose audio amplifier has a decided peak on the higher frequencies. as the higher piano or violin notes will be over-emphasised. The quality on distant reception is also likely to be poorer, due to increased regeneration in the r.f. amplifier. The best test for the average person is to replace the present detector grid-leak in his receiver with a £ megohm size and listen for improvement or decrease in quality on local reception.