"ON THE AIR"

Poverty Bay Herald, Volume LV, Issue 16958, 23 May 1929, Page 9

"ON THE AIR"

I WORLD TUNES IN ON 20.C00.000 KUITOPJG MAS .MURE HIGHPOW&RED STATIONS I rnc first radio census ever undertaken to cover tin: entire work! shows !iO,OOO,CCO receiving sets in use, extending from Green/and to Ceylon and Jugoslavia to China, while radiocasting stations are now operating from the Arctic circle to the equator. Nearly one-halt' of all radio sets in use, according to Lawrence D. Batsun, of the electrical equipment division of the Department of Commerce, who made the world survey, are in the United States. Salient facts disclosed by the survey j are:— 1. Radio has penetrated to the four I corners of the globe. 2. Outside the United States, radio entertainment programmes are almost universally supported by license fees collected on sets, ranging from as low as 4 cents in France to 18 dollars in San Salvador. 6. The most powerful radiocasting stations on earth are in Europe, Russia and Finland leading the world. 4. Approximately 90 per cent, of all 5' radio equipment is made by America, j England, and Germany. j Analysis of world markets for radio ' equipment by the Commerce Department shows that radio has covered the world in short time, and the nations of the earth to-day are tuning in sets to "catch practically the same type of programmes as are given in the United States." Great Britain and Germany have about 2.500,000 sets each: France has 1.250.000. Japan 550,000, and Argentina, 530,000. The United States is believed to have 10,000,000 sets, j Practically every foreign country, the report states, governs radiocasting by regulations. The largest Buropean I countries own and operate the stations themselves. Sweden grants a concession to one company to operate the main stations, while the smaller onesare owned by radio clubs. Tn North and South America broadcasting stations with few exceptions are privately owned and operated) Australia and New Zealand grant concessions, but the former country is now preparing to take over the high-powered stations. I (Vutside the United States it is the I general rule for owners of radio sets to pay a license fee to their respective 1 governments, these taxes ranging from as low as Four cents 'in France to 18 'dollars in San Salvador. The British fix is about 10s. the German £1 ss, the Australian about £1 12s 6d. while the Japanese owner of a radio set must pav in the vicinity ot" £2 ss. | The highest . powered 'foreign broadcasting stations are all in Europe, the report, shows. Russia and Finland each maintain stations of 40.000 watts. There are more than ?0O broadcasting stations in F.urone; South America has 62; Australia 25; while Japan has seven. RADIO AS .STORM FORECASTER BROADCASTING WEATHER CHARTS i LONDON. April 6. ' Atmospherics, the bugbear of radio '■ broadcasting reception throughout the * I world, may prove the means of fore- • casting thunder storms and consequent ' ! hailstorms" which do such damage nt < •times on the prairies. Such is the con- < elusion of 31. A. Watson Watt, super- « inte.ndent of the radio research station I at Slough, who has been conducting 1 scientific investigations into the reia- < tions between radio and the J j Radio, he insists, can have no effect ' whatever on the weather, but as atmo- < spherics originate in thunderstorms, ex- £ perimerits have shown that it is possible to locate thunderstorms by radio even c when they are 2000 miles away. Radio j direction finders, therefore, would probably in future be utilised to indicate the J direction in which storms were moving, and thus give accurate information which, over great areas of country, cwould allow of precautions being taken, e . Broadcasting of charts of the weather * in the Atlantic and over Europe by J television method ought to be attempted in Great Britain from the great sta- * tion at Daventry. * CHANGING- VALVES t c . t A great many radio receiver owners f change from one class of valve to an- ( other for no reason than that they con- v sider the newer type of valve will give f better strvice. This may be quite cor- c rect, but it will frequently entail the r changing of transformers to suit the 1 particular type of valve if best results { are expected. It must be remembered 1 that when valves are changed they will probably require an adjustment of plate pressure to ensure their correct functioning. For example, an old valve which has been used as a detector maygive very satisfactory results with a plate pressure of from 45 to 60 volts, \ whereas a new detector valve may require a pressure somewhere in the region of only 22i volts in order that it may give satisfactory service In re- j placing the audio-frequency valves by ] newer tvpes it will probably be found j that the grid bias pressure is incorrect. ( There is no more satisfactory method of j adjusting the grid bias than to employ ( in the plate circuit of the valve in c question a D.O. milliammeter, with the receiver tuned to the strongest signal; ( a very small movement of the meter ( needle should result if the bias is cor- ] rect. If the. needle jumps upwards it ( is an indication that the bias pressure is too low; on the other hand, if it jumps downwards the bias pressure is too high. With the correct adjustment, if there is any movement at all of the | needle, it should bo equal in both ' directions. When the signal is detuned . the plate current indicated by the meter Khoiild remain substantially the same when the bias adjustment is correct. j

BY "BCL*

CHANGING FBCBI "B" BATTERIES TO "B" ELIMINATOR

Alaiiv people will probably decide for a. change from B battery supply to B battery eliminator (says a Melbourne paper.) A B battery eliminator usually gives a much higher pressure than a battery-led set has been accustomed to. This may cause all sorts of complications, which invariably result in imperfect reproduction. ' The grid bias pressure will almost certainly require re-adjusting, and here again the D.C. meter should be used for its correct adjustment. It is quite impossible to relyon the ear as a means of ascertaining whether the tube is behaving correctly or otherwise. The meter is the only positive indication, and it will come as a surprise to most people to find just how far out they are in the adjustment of their bias pressure. Very little difficulty will be experienced. in adjusting the pressure of the first audio stage, but the adjustment of the late stage. which should employ a power tube, is more difficult, but. vitally important. The valve of grid bias, which is indicated on the package in which the tube is sold, is usually a fair average, but

cannot by any means be taken as a reliable value. For instance it is suggested that the meter be employed. If a bias adjustment is impossible which causes a steady indication on the meter the operator can be certian that the tube in question is overloaded; it should he replaced by one of greater handling capacity.