THE RADIO WORLD

Southland Times, Issue 19279, 25 June 1924, Page 9

THE RADIO WORLD

(By “Reflex”). The revised radio regulations issued by the P.M.G. in Great Britain contain the following new paragraphs:—(l) Spark transmission is prohibited; (2) transmission on the amateur 40-metre wave length is prohibited during broadcasting hours; (3) a further wave length band from 115 to 130 metres is allotted to amateurs. The British Broadcasting Company’s proposed 25-kilowatt broadcasting station is to operate on a wave-length of 1600 metres, so that it could not interfere with the present band of broadcast waves of 300 to 500 metres. A stir has been caused lately in England and America by an invention that adapts the ordinary house lighting electricity for supplying current to radio sets for both filament and plate potential. It is reported to be silent in operation. China has placed an embargo on radio broadcasting, the official opinion being that it may become a powerful weapon in the hands of opposition, An ambitious American firm announced that it intended to inaugurate a broadcasting service in China, but evidently changed its mind when the Customs Commissioner at Shanghai gave out the information that all such apparatus would be seized as contraband of war. By the aid of receiving sets and loudspeakers, 10,000 school children in 60 schools in and around London recently listened intently to an afternoon address on “Music and School Life,” by Dr Sir Walford Davies, broadcasted by the big London station, 2LO. Some 25 boys and girls were seated in the broadcasting studio behind the microphone, and were greatly interested in what they saw. As a result of this initial experiment addresses on subjects of interest to the children are now being given by radio regularly during school hours.

A member of the radio trade cites instances where radions of lengthy experience and possessing first-class tuning equipment complain that certain amateur transmission is completely spoiling concert reception. The trouble threatens to become a set-back to the industry, and unless some steps are taken shortly to remedy the evil the' trade proposes to justify the complaints, and members of the trade are prepared to afford a test for the Post and Telegraph Department officials to witness for themselves.

During the last six months eleven, new broadcasting stations have been installed—five in Ontario, one in Nova Scotia, one in Quebec, two in British Columbia, and two in Alberta. This makes a total of fortyfive stations now in operation. A new amateur station has appeared on the air lately, using the call sign 4AR, and since this call has not yet been assigned to anyone the radio inspector is rather curious to know who 4AR can be, says a Dunedin paper. His wave comes in well with an A.C. hum, and from the strength of signals the station is probably outside the city. THE TBANSVERTER. i A SURPRISE MACHINE. A great deal of interest has been aroused by the production of a surprise machine by the English Electric Company, and up to the present all inquiries have failed to elicit any definite information concerning it. For the first time the apparatus has been exposed to puttie gaze at the Wembley Exhibition. The machine is the invention of Mr W. E. Highfield, who has to his credit several notable inventions, and its function is to convert alternating current power at any supply voltage to direct current at voltages of the order of 100,000 volte or so. Its application to radio for plate supply of high-power valves is assured, as well as its even more important application to 'power transmission. Briefly, the action is as follows:—A.C.

power, three phase at supply voltages is transformed through three transformers to 36-phase power, and each of the 36 phases is connected to each of 10 commutators on a shaft driven by a motor operated from the same source of supply. Each commutator transforms the A.C. to D.C. at 10,000 volts, and since the 10 commutators are in series the total voltage may be 100,000. Further details of the apparatus are looked to with interest, since the problems involved are of considerable magnitude, and it may, on a smaller scale, be of use for even small transmitters, convert ing the 230-volt supply to any voltag from 100 to 1000 with steadier output the. the usual D.C. generator or rectifier A.C. A GOOD RECEIVING SET. HOW TO MAKE IT. One of the questions most asked by those taking up radio is: What is the best receiver to get ? and there is no more difficult question to answer. The reason is that so much depends on factors over which the manufacturer has no control. One of the leading American concerns has analysed the factors contributing to a successful set, and though I have not the figures at hand, from memory I think the proportions allotted to the various factors were: Aerial 10 per cent., tuner 20 per cent., valves 5 per cent., wiring and mounting 5 per cent., batteries 5 per cent., personal ability 40 per cent., other causes 15 per cent. These figures may be rather different, but the importance of the various factors was approximately as I have given above. From this it is obvious that when nearly half the success obtained from a set depends on the operator two sets identical in construction can hardly be expected to give the same results in the hands of different operators. Each and every enthusiast stands by his particular fancy, anti in most cases he is quite justified, since he operates this type of set better than he can handle other types. To make a really good receiver it is esesntial (1) to have it built for local conditions. Most imported sets are not suitable for use in New Zealand. (2) Use only the best parts; the cost will be greater, but results will be correspondingly increased. (3) Learn how to tune in effectively. (4) Erect an aerial suitable for the broadcasting wave lengths, with an efficient earth. A high-class set cannot be turned out in a few days, and a great deal of patient adjustment is required before every part is functioning to best advantage. Personally, I believe in the owner trying systematic alterations until maximum efficiency is obtained, since it is hardly likely that anyone else will have to try each part out completely. As a guide to maximum efficiency, I would say that when, using the detector valve alone, you can tune in 2BL (Sydney) so that the words of the speaker are distinct and free from carrier wave distortion your set is working well. You cannot do this unless each part is functioning at a reasonable efficiency, and in my own case it took manv nights of careful work before

I was satisfied with the detector. Of course, there are many people—in fact, most people—who have not time, knowledge, or desire to make their own set, and these have simply to place themselves in the hands of some reputable amateur who knows their requirements.