THE WIRELESS WORLD

Otago Daily Times, Issue 23830, 9 June 1939, Page 2

THE WIRELESS WORLD

NEWS AND NOTES By Magna Vox Items of local Interest are Invited by ‘ Magna Vox ” for publication in this column It is necessary that such matter Should reach this office by Tuesday of each week for insertion in the following Friday IYA Auckland.—6so k.c., 461.2 metres 2YA Wellington.—s7o k.c., 526 metres 2BL Sydney.—74o k.c., 405 metres 2FC Sydney.—6lo k.c., 476 metres 3AB Melbourne.—77o k.c., 390 metres 4QG Brisbane.—Boo k.c.. 311 metres 3YA Christchurch.-720 k.c. 416.4 metres 4YA Dunedin.—79o k.c., 379.5 metres 4YO Dunedin.—ll4o k.c.. 261 metres ANSWERS TO CORRESPONDENTS “Ganger,” Temuka.—(l) The capacity varies appreciably with the size, number, and spacing of the plates. Any radio dealer would, no doubt, be able to give you the capacity just by examining the condenser. (2) By tuning the coil with a variable condenser of from .00035 to .0005 mfd capacity, depending on the number of turns, gauge of wire, and diameter used, the circuit could be improved. ‘ Regenerator,” Oamaru.—Yes, this is known as electron-coupled regeneration, and by using It you will obtain very good tracking. The cathode tap should be taken off the grid-winding at a point approximately one-third to one-quarter of the winding length away from the ground end. A LEISURELY POLICY The 8.8. C. plans to replace two of its 75-kilowatt transmitters by others with an output of 120. kw„ but in accordance with its leisurely policy the change will not be made until the spring of 1940. It is one of the mysteries of radio that nobody in New Zealand has been able to pick up an English station on the broadcast band, though Continentals of lower power are heard without difficulty. NEW EMPIRE WAVELENGTHS Six new wavelengths on the shortwave bands are to be used by the Empire transmitters in the near future, bringing the total number of channels to 21 over a frequency range of 6.05 megacycles to 21.55 megacycles, or 13.92 metres to 49.59 metres. The new frequencies are:—GSJ2, 13.91 metres; GST2, 13.86 metres; GSU. 41.32 metres; GSV. 16.84 metres; GSW, 41.49 metres; and GRY, 31.34 metres. Certain restrictions have been imposed on the use of GSU and GSW, these being, in the main, a condition that these wavelengths may be employed only at defined hours of the day. At other times other stations are licensed for these waves. The wavebands utilised by the Empire stations vary with each of the six transmissions, this being necessary in order to take the utmost advantage of the vagaries, both seasonal and throughout each day, which are the bugbear of short-wave propagation. A COSTLY BUSINESS More than the customary grain of salt should be taken when reading overseas announcements that television is on the verge of becoming popular and inexpensive. Omitting, for the moment, all question of the huge cost of transmitting apparatus and the yet unsolved problem of programme material, this newest radio art is certain to prove expensive. The most modest of receivers require 16 to 20 valves, very high voltage, and expensive power pack, to say nothing of a costly and fragile cathode ray tube. In fact, a television receiver consists of two complete receivers, one for voice and the other for the image. The image portion of the outfit is exceedingly complex, and it has been found that on present systems simplification is impracticable without seriously impairing clarity of results. RECEIVER DESIGN Apart from the wider use of permeability tuning and minor refinements in circuits and apparatus, there have been no startling developments of late in receiver design and construction. The development of new valves has made possible some improvements, but in the main these have been for special types of receivers, such as those where low current drain is desirable. The push button feature is now common, and it has been improved to a “dialing” method, not greatly dissimilar to that used on the telephone, in a few of the latest models. There has been developed also a remote “tuner." This permits of tuning the receiver both as to station and volume from a remote location by" merely plugging in a special apparatus in the room from which the set is to be tuned, but this is expensive, requires specially-wired channels, and is, therefore, not likely to come into widespread use, 8.8.C.S NEW MICROPHONE The desirability of using in outside broadcasts and in studios to which audiences are admitted microphones at once highly sensitive and in conspicuous has resulted In the designing by the 8.8.C.’s Research Department of a new type of instrument that is now being put to increasing use in British programmes. Known as the Type “B ’’ BBC-Marcom ribbon microphone, It represents the result of two years’ work by the research engineers, and has proved so successful that many broadcasting organisations overseasin South Africa, South America, India, and in the Colonies, for example—have adopted it for local use. In effect, the microphone is a refinement of the British type of ribbon microphone evolved by the Research Department five years ago and which is now standard in 8.8. C. studios. Though representing a decided advance in the technique of mcrophone design—chiefly because of its bi-directional properties and tne simpler balance technique that it made possible—the original ribbontype instrument—known as Type “ A " —was not altogether ideal for broadcasts from outside sources, owing to its size Of a conveniently round shape the instrument ultimately designed to offset that disadvantage is less than half the size of the Type “A,' and has the same sensitivity and identical, if not better, all-round performance. New magnetic materials made possible the reduction in size. In the Type "A” it was necessary to use a nickel-cobalt magnet having_ a minimum path-length of about 12in, but in the Type “B” an aluminium-nickel-cobalt alloy has been used that enables the path-length to be reduced to less than six inches without any loss in sensitivity. TELEVISION DIRECTOR ON LOAN Mr D. H. Munro, Television Productions manager of the BBC, has been temporarily released to the Columbia Broadcasting System of America for work arising out of the opening of the CBS television service. He sailed for the United States of America on' May 4, and expects to be away from London for at least six weeks. Mr Munro joined the BBC in 1926 as an announcer at the Aberdeen station, came to London in 1929 as productions assistant, and was intimately concerned with development in multi-studio presentation involving the use of the then new dramatic-control panel. As the operator of an advanced type of control panel, Mr Munro was responsible for co-ordinating the “ Round the Empire broadcast of 1932, in which King George V gave the first of his memorable series of Christmas messages to the world. When Mr Gerald Cock was appointed Director of Television in 1935, he chose Mr Munro as Productions Manager. The appointment brought with it an entirely new set of problems, as no precedent existed for the organisation of a _ high-definition television service. Since the start of the service in the autumn of 1936. Mr Munro has been responsible for studio organisation and general routine and he has produced more than a hundred television programmes. HERE AND THERE After some months of research, the BBC staff announces that about 32,000,000 people listen regularly to its programmes. Of these, 7,500,000 are

under 16 years of age. Programme features are rated in this ordervariety, theatre organs, military bands musical coffiedies, dance music, plays, light music, orchestral music, brass bands, talks, discussions, and. last of ah, chamber music, Latest world statistics available show that America comes first as a radio-owning nation, with 20.133 per cent, sets to population. Next come Denmark 18.99; Great Britain, 18.35; New Zealand. 17.41; Sweden. 17.05; and Australia, 14.73. Germany’s percentage is 13.39. but elaborate arrangements are made there for mass listening in streets, halls, factories, etc. Considering the value placed on radio by Mussolini, it is strange to find Italy as low as 1.89, but here again mass listening is provided for. For 1938 the income of the BBC was £3,800.000. Programmes absorbed £1,892,000, approximately half the revenue. Six short-wave transmitters, two television units, and 17 stations supplying entertainment for the British Isles had to be maintained, television being a particularly costly affair compared with the service rendered. The total number of transmitting hours for the year was 115,050, with a breakdown percentage of 0.023. The aerial for a television set hangs vertically, this being better for the reception of ultra-shortwaves than the horizontal type that is most suitable for ordinary radio. Up to the present, television in Germany has been a laboratory affair. Now it is proposed to follow the lead of England and America and establish a public service. At the outset, reception is promised over a range of 50 miles from Berlin. Sets are being produced to sell at equivalent of £SO. Jack Davey, who had been on the announcing staff of 2GB for several years has gone into business,on his own account. His plan is to record programmes which will be sold to advertisers and radio stations.