RADIO TOPICS.

New Zealand Herald, Volume LX, Issue 18585, 18 December 1923, Page 6

RADIO TOPICS.

• • ■ »t; thermion. BROADCASTING STATION. A new broadcasting station ' has commenced operations at Giaborne so that the following stations are now'in operation in New Zealand :— ■ ' <" • * • ■■•., » . Auckland Radio - Services, IYA, 260 metres, 200 watts. : v V C. H. Pearson, La Gloria; Gramophones, Ltd., Auckland, IYB, ■ 260 metres, 90 watts. ■ ■" -; f ; Gisborne Radio Co., 2YM, 335 metres, 500 watts. ' , ' . Wellington Broadcasters, Ltd., 2YB, 275 metres, 15 watts. i ' Dominion Radio Co., Wellington, 2YK, 275 metres, 15 watts. British Electrical and- Engineering Co., Dunedin, 4YA, 310 metres, 500 watts. Western Australia is to have a broadcasting station which will be controlled by Westralian Farmers, Ltd. They propose to install one of the most up-to-date broadcasting equipments and to have the station in operation within three months. The programmes will consist mainly of matter of direct interest, to farmers, pastoralists, and country residents generally. There are to be news items, market reports, musical entertainments, speeches by visitors, and church services. Australia has been somewhat slow in inaugurating broadcast service, but. once started it is apparently the intention to give a broadcast of a very high standard.A unique achievement for New Zealand was recently carried out in Wellington by the Wellington Broadcasters, Ltd., when the whole of the play, "The Cat and the Canary," was successfully broadcasted and picked up by many enthusiastic amateurs.

RADIO DEMONSTRATIONS. A demonstration was given last Friday and Saturday evenings at the Dominion Road Carnival where an endeavour was made to entertain the public with th« music being broadcasted from IYA and IYB. On Friday evening the programme from Scots Hall came through excellently j from the point? of view of volume and was easily audible a quarter of a mile distant.. On Saturday the power used by IYB was apparently insufficient to enable their broadcast to be heard at any great distance from the loud speaker. At Dominion Road the entertainments were received on a standard three-valve set having the two stages of audio frequency amplification and the output from this was applied to a Western Electric threevalve power amplifier and thence to a Western Electric loud speaker. The amplification from such an arrangement is, of courso, tremendous buC there is the disadvantage due to its inherent properties giving distortion. It is unfortunate that all such demonstrations held locally have provided distorted music and speech and the comments in the street indicated that the general public are not greatly, impressed with radio music. The uninitiated are naturally inclined to believe that all music by wireless suffers from more or less unpleasant distortion which, of course is not the . case. The trouble is due firstly to the iron-cored inter-valve transformers used, the greater Che number the greater the distortion, and secondly to the fact that ( there is no loud , speaker yet designed that will carry the large current due Ito high amplification without giving a distorted output. This second difficulty can be overcome to a large extent by using several loud speakers connected in parallel so that the load on each is reduced while the general volume is maintained. Unless demonstrations can be given having an absolute freedom from distortion, they, as a means of interesting the public generally in radio, should be entirely discontinued. They will undoubtedly do more harm than good to the radio interests.

FAULT TRACING. The jnovice usually experiences some littlo difficulty in locating faults in a receiving set so. that a few hints showing where to look for the source of the trouble may prove useful'to him. Case where 110 Signals can be heard (1). Aerial-earth circuit. Loose or dirty connections at aerial or earth _ terminal; ' poor joints between aerial wire and down-lead, or between earth terminal and waterpipe; complete break in aerial or earth wire; short circuit between aerial and earth due to faulty aerial insulation or to aerial touching trees or buildings; aerial tuning inductance or wires connected to it may be faulty duo to broken connections to studs or variable switch, or to switch arm not making proper contact with the studs; aerial condenser may be faulty due to plates -touching or dirty connecting wires to it; lead-in; insulation faulty. (2). Tuner Circuit. Inductance winding broken; plates of variable condenser short-circuited. (3). Detector Circuit. Any internal lead in the detector circuit broken, (a) Crystal set. Insensitive crystal; dust or grease" surface of crystal; rust on cat's whisker contact, (b) Valve set. Valve broken or valve legs making poor ■ contact with sockets of holder ; nigh tension battery reversed or cells run out; filament battery discharged. In addition to the above possible source of trouble on an amplifying circuit is a burn out in the primary winding of the intervalve transformer. (4). Phone . Circuit. Break in phone leads either in set or in flexible phone leads; faulty external connections on earpieces ; internal faults in earpieces due to broken windings of magnets, or to internal connections. ' .

' NOTES AND HINTS. > j : At present, in England, the practice of installing small portable receiving sets 'on motor-cars is a popular one. Many light 8.8.A. care are being thus equipped by the makers. These sets are not designed for reception while in motion, but when at rest a small length of insulated wire thrown over a tree or any convenient object serves as the aerial. The sets use two valves, the filament current for which is obtained from the car battery. Next summer when the proposed local broadcasting scheme should be in operation giving an afternoon as well as an evening entertainment portable sets should find much favour with motorists and picnic parties generally. W'th the advent ot the dry cell valve the construction' of portable sets of small size is comparatively easy.

As an entertainer of the sick radio offers a large sphere of usefulness. This • has been realised by the Wellington Hospital Board, who have purchased and installed a receiving set for the benefit of the patients in the Ewart ward. \lt is hoped to make early similar installations • in other wards. In an English hospital the arrangement is that the broadcast is received on a centrallylnsnrtled set and the output, is led to a .pair 1 of phones placed at the bed of each patient. A switch is provided fo that +h e patient can h<t«h to or switch out £10 broadcast as desired. ■ The thoriated filament of a- dry cell tube should not burn too brightly, as too large a current will release electrons so rapidly that the supply of free electrons will be more or less exhausted, and the lesult is weak signals, or no signals. If this should occur the filament can be restored to a wprking condition by allowing it to burn for an hour or so at its rated current with the B battery disconnected. A U battery should be discarded when its voltage drops to 60 per cent, of its normal value. If it is still used its largo resistance weakens the signals and causes parasitic noises. Where American valves are used the "hard" or highly evacuated type works best as an amplifier with 90 volts 011 the plate and with 45 volts as a detector. The "soft" valves, which make excellent detectors, require about 224 volts 011 the plate. . / - Both a crystal and a valve are voltage Operated devices, so that the tuning circuit connected to them should have as, much inductance and as little capacity as possible. For example, if ' signals are first heard on a coil having 25 turns and a. condenser reading about 80, increase the inductance to 35 or more turns with corresponding less capacity for louder j signals. •• j