Radio IN THE HOME

Timaru Herald, Volume CXXXIV, Issue 18849, 11 April 1931, Page 14

Radio IN THE HOME

MAN-MADE STATIC, Interference with perfect broadcast reception is enough to spoil the enjoyment of any listener. Especially is this ~.0 when headphones are used, as constant clicks or hum become highly irritating (says H. Ramford in “Popular Wireless.”) It is not proposed to deal with this subject in the usual way, by explaining how to increase the selectivity of the receiver itself, but by showing how to arrange the aerial-earth system in order to obtain specific results. Increasing the selectivity, by using aperiodic coupling, tuned aerial coupling, or any of the ordinary methods, does, of course, help to reduce unwanted “signals,” but it is presumed that the reader has already experimented with these himself. It might be mentioned, however, that tuned ierial coupling, especially with loose coupling to the secondary circuit, will often reduce appreciably the noises resulting from outside sources other than radio. Before attempting improvements, it is best to disconnect both aerial and earth from the set of terminals, and to connect each in turn, noting the difference in the amount of background noise; for it must not be forgotten that background noises are often due to a faulty grid leak or to bad or dirty connections, nor that earth currents are often the cause of the trouble. A good size of aerial for loud reception is about 50ft. long, with a downlead of 25ft., the complete aerial from the furthest insulator to the set terminal consisting of one continuous length of wire. If a certain falling off in signal strength can be afforded, however, better selectivity will be obtained by shortening this length considerably, while shock excitation from nearby transmitters will be diminished. Atmospherics cover a wide band of wavelengths, and though there are circuits designed to cut them out, they are by no means perfect, for they complicate the apparatus and greatly reduce the wanted signals as well. A short aerial is advantageous. As regards “man-made static,” which consists of noises from electrical machinery, railways, trams, dynamo-charg-ing plants, etc., the best plan is to place the aerial as much as possible at right angles to the power lines. A further remedy is to try a different earth connection, such as water-pipe instead of outside earth, or even to use a counterpoise. The latter could consist of a single wire stretched at a height of 10ft. from the ground and directly beneath the normal aerial. It w r ill have to be efficiently insulated in the same way as the aerial. An improvement on this is a number of wires, suspended in the same manner, spread out fan-wise and connected together at the near end. Often a fixed condenser inserted in the earthlead will improve matters. It should be noted, by the way, that interference from lighting mains occasionally results from too long a lead from grid condenser to grid of the detector valve, or the core of the intervalve transformer being in the magnetic field of the lighting wires behind ti?* walls. In the latter case, if it is possible to earth the core or shield the transformer in any way, do so; otherwise it will be necessary to move the set to another part of the room. Where an output transformer is used, the same applies, an additional precaution being the' earthing of one side of the secondary. A frame aerial is another solution, but because of its inefficiency it is not generally to be recommended. When the cause of the trouble is electric apparatus close at hand, the best thing to do is to go and make friends with the owner. Improved signal strength can be obtained by “pointing” the aerial toward the desired station. Curiously enough this means that the free end is furthest from the station, the lead-in end doing the “pointing.” If this is not possible, at any rate have the aerial at right-angles (broadside on) to any station that refuses to be tuned out. is, unfortunately, always with us when receiving distant stations. This is not static, of course, but is nevertheless an acute problem that many learned minds have tried to solve. There are two things that are often taken for fading. One is the results produced by a Swinging aerial. To tighten it excessively means a great strain on the wire and a great strain on the mast. This has been solved by some manufacturers, who have placed insulators incorporating springs on the market. I have never used one myself. The other is the “searching” of the next-door “fan." The trouble is most severe when one or both parties use reaction on the aerial. For best results, efficient high-fre-quency stages are needed for both parties, but by placing the aerials as far away from each other as possible, and at right angles, and by using different earths, a cure may be effected. The condenser in the earth lead as originally advocated, should result in an improvement. It is not suggested that any one of these will cure the trouble, or that even all of them together will entirely eliminate unwanted signals, but they should at little cost, make listening more pleasant. The little 50-watt station 3WR Wangaratta, has shifted its wave-length 10 kilocycles further from 2NC Newcastle. This alteration was made on Sunday nieht last.

BRITISH BEOADCASTING CO. A suggestion has been made that the control of broadcasting should be plac- ‘ ed under a body similar to the 8.8. C. A sketch of this body's history, as given in the 8.8. C. Year Book, 1930, is of direct interest; — “On 4th May, 1922, the PostmasterGeneral, the Right Hon. F. W. Kellaway, M.P., announced in the House of Commons that he had decided to permit the establishment cf a limited number of broadcasting stations, and that to this end he was calling together a conference of those interested. The first meeting took place on 13th May, was attended by representatives of twenty-four firms engaged in the manufacture of wireless apparatus, and was important in that it recognised the desirability of co-operation between the various firms who wished to have transmitting licences. These firms accordingly went into committee and endeavoured to produce a scheme . for the joint conduct of broadcasting in Great Britain; but after many meetings there ! still remained two schools of thought, which appeared to be irreconcilable, with the result that the committee reported that, whereas one organisation appeared to be impossible, it might be that broadcasting could be conducted through two separate concerns. “The Postmaster-General agreed, if necessary, to grant not more than two separate licences but exhorted the conflicting groups to find a solution in complete agreement. Accordingly a sub-committee was formed of two men, each representing his group as in single combat, and after considerable negotiation they achieved a satisfactory result and reported to their colleagues a basis on which could be formed a single broadcasting company. The Postmaster-General, on receiving from the committee their report, agreed to grant such a company an exclusive right to operate broadcasting stations within the United Kingdom, provided that an adequate service could be guaranteed for a reasonable period of time. This guarantee was provided by six firms, namely, the British Thomson Houston Company, the General j Electric Company, the Marconi Company, the Metropolitan Vickers Electrical Company the Radio Communication Company, and the Western Electric Company, who undertook to finance a service for a period of two years, and thus may be said to be the father of British broadcasting. The authorised capital of the new company was £IOO,OOO, £60,000 being subscribed by these six companies in equal proportions, the remaining £40,000 being made available, at first to other British manufacturers of wireless apparatus, and subsequently to wireless dealers. Of this sum £11,536 was actually issued 1 and subscribed, the number of shareholders eventually rising to 1700. Mem- ! bership of the 8.8. C. could be obtained | by the purch' ' one £1 share, which ; entitled the . iolder to the use of the stand (8.1.vJ mark. WAVELETS. The Australian stations broadcast j some fine programmes during the Easter season, with a strong leaven of sacred items. The “Yanks” came tumoling over one another over Easter. Although reception was rather rough on longdistance at times, volume was good. Some Asiatic stations not on any of the charts could be picked up on the early hours of the morning. Japanese stations, which had been rather quiescent for some time, have been much in evidence lately. Jap. programmes soon pall on listeners unacquainted with the native lingo, and it is unfortunate that they are superimposed on the principal Australians. 2BL, 4QG, 3LO, and 3AR particularly suffer at times from heterodyning from Japan. One of the things “that neve: - would be missed” is the DX competitions idea. The promoters of one organised in New Zealand stated that the principal New Zealand and Australian stations were excluded, so that the oscillators would not annoy other listeners. It was overlooked, however, that practically every main station in Australasia has a Yank on or near its wave- ! length, and it is reaching for these with pony sets that are responsible for a lot of howling. Following are the closinj times of some of the principal Australians stations:—2FC. alternate nights 10 and 12.30 (New Zealand time*; 2BL. 10 or 12.30; 2NC. 12.30: 2GB. 12.0; 2TJW, 12.0; 2UE. 11.45; 2HD. 10 30; 3LO. 11.0; 3UZ. 12.30; 4QG, 12.30; 3AR. 12.0; 4BC. 11.30; 4BK. 11.30; SCL. 1.0: SKA, 11.45; 7ZL. 12.30; 6WF. 1.45; 2AY. 12.0; 7LA. 12.0. On Saturday nights many stations run for an extra half-hour. The question of wave-length of New Zealand B stations demands some attention by the Post Office. There are two or three stages in the broadcast band where the air is cluttered up by a nest of small stations. Things are bad enough when these keep to their allotted wave-length, but some of them have a habit of wandering over a few metres. Australian stations also are located on these wave-lengths, and there are times when only super-hatA. can separate the different transmissions. Even super-hets. cannot cus out heterodyning whistles.