THE WIRELESS WORLD

Otago Daily Times, Issue 21431, 4 September 1931, Page 5

THE WIRELESS WORLD

NEWS AND NOTES By Magna Vox. Items of local interest are invited by “ Magna Vox ” for publication in this colupin. It is necessary that such matter ► should .reach this office, by Tuesday of each week for insertion on the following Friday. Metres. 7ZL, Hobart , .. .. .. 535. 3AR, Melbourne ■ . . _ 484 4VA, Dunedin ... .. ... 4G3 2FC, Sydney .. .. 442 2YA, Wellington , ... .. 420 4Q6, Brisbane ... .. .385 3LO, Melbourne .. .. 371 V2AB, Sydney .. .. .. 310 , 2KY, Sydney .. .. --.. 280 _■ ULTRA-SHORT WAVES. gestibn in an article in' the Observer, Captain E. H. Robinson states that two possible remedies are . well known. One is the, use of only half tae carrier wave of each transmitting station, and the other is the substitution ot frequency modulation for the present amplitude modulation of the carrier. Either is possible, but either would, mean the scrapping off all existing receivers. A third avenue of escape has been opened by the work on ultra-short wave , speech transmission now being carried on in Germany and to some extent in the United States of America. These ultrashprt waves have properties which make them' . peculiarly suitable for speech transmission, the most important being that their range is comparatively short, and that they can give the utmost service area of which they are capable by the use of quite low power. The apparatus necessary for their reception differs so little from that in use for broadcast reception as we now know it that the alterations of existing receivers would be a cheap and simple matter. The lelefunken Company have shown that speech and music of-, a remarkably high quality can be put on seven metres and absolutely confined to an area roughly 20 miles in diameter. The possibilities of this system are at once apparent. Each densely populated neighbourhood in any country could be served with a short-wave transmitter which, with the present high development of landliue working, could be supplied from a central studio. It desired, these ultra-short’ wave stations could be worked bn exactly the same frequency. Probably they would Have to hoof the same frequency, for the work ot the German high frequency engineers tends to show that only a. very narrow wavelength band is- suitable for this method of transmission. Associated with the ultra-short . wave stations, which would supply the greater percentage ot the population in each country, there would be a few high-power stations for the benefit of those outside the normal urban service areas. Theqe would be so few- in number that they could be arranged in the available spectrum with very little chance of mutual interference. These ultra-short waves are practically immune from the ordinary kinds of static interference. BULGARIAN STATION. Bulgaria’s first transmitter _ has been opened in Sofia. Messrs Philips inform us that the station is installed in a bank building, has a power of 1 kw, a wavelength of 319, metres,' and uses the call “Rodno Radio.” . ■ ■ FRENCH RAILWAY EQUIPMENT. The State Railway, have now equipped 22 trains with broadcast receiving equipment, which enables passengers to listen to concerts transmitted from French and foreign stations, and also to hear gramophone records played on the trains themselves. NEW GERMAN RELAY. The new two-kilowatt (aerial) relay transmitter to be installed at Trier (Germany) will be fed by the Frankfurt-on-Main studio,, and will work on a common wavelength (259.3 metres) with this station when the new 25-kilowatt plant for the latter city has been erected. INDIAN LICENSES;'’.' , ; . A correspondent in India reports that the number of licenses of all kinds increased all round; broadcast receiving licenses rose, from 6400 to 7700. The [numbers of. fixed stations and mobile startions.. licensed were ,171 and 31 respectively.. Permission to broadcast was given to the Corporation of Madras. FREE LICENSES' FOR UNEMPLOYED. •“From March onwards the German Post dffice is giving unemployed listeners receiving unemployment payj,,;free listening 'licenses. The only condition attached is that they must have been listeners for at least three months before becoming unemployed, and they must prove by the 25tb of C/ich month that they are still unemployed for the gratis licenses to be continued. i SCREENING. Constructors do not always realise that it is just as necessary to screen condensers as well as all coils on the high-frequency side of a set. The potential variations on the vlines of a tuning-condenser set up spreading fields of static force, which are just as liable to give rise to back-coupling as the magnetic flux from a high-frequency coil. This liability to elcctro-static interaction between different circuits is, of course, greatly increased when several condensers are “ganged” together in close proximity to one another, so -that care should always be taken to see that they are adequately screened from one another. ICELAND’S PROGRESS. „ ' A mountainous country of some 05,000 square miles, with a population of. 100.000, needs a powerful long-wave station. .Weather news is still radiated by the old Reykjavik plant. The new-station is situated on a, hill five miles east, has 500 ft masts, a power of 11 kw., and a 1200 m. wave-length. It commenced to operate ui ■December, 1930, cost £35,000, and listeners are expected ultimately to number 10,000; at present they total about one-third of that figure, and each pays 27s a year. The managing director is responsible to a'-State board of five members. HUGE RUSSIAN TRANSMITTER. Broadcasts from the Moscow Trades' Unions studio are simultaneously transmitted on 1.304 and 50 metres. Plans for -the development of the Soviet radio system call for II 100-kilowatt • and 38 10-kilowatt transmitters to be in operation by the end of 1936. It is proposed to use the 500-kilowatt transmitter now in course of erection at Noginsk (near Moscow) solely for international -propaganda. A new 75-kilowatt station is nearing completion at Kolpino. CURBING THE CONTROL ROOM. How much a control room engineer may interfere with the output from the orchestra in the studio has long been a bone of contention between the musical and technical staffs of broadcasting organisations. Apparently the discussion will be at an end so far as the new Budapest transmitter ia concerned,-for.the plans include the provision of a soundproof glass case to accommodate the conductor, who will hear hie orchestra as it is heard by the radio listener. JAPANESE REGULATIONS. The Nippon Hoso Kyokai (Broadcasting Corporation) is a State concern, the Tokio,' Osaka, and Nagoya undertakings having been handed over to the Government in 1925. The board of directors is re-elected every two years; there are seven service areas with headquarters at Tokio. On February 27, 1931, Tokio (JOAK) had 344,113 listeners, Osaka (JOBK) 235,478, and- Nagoya (JOCK) 83.000, apart from those of minor stations. Each listener has. to, register at the Bureau of Communications, the fee being 2s in addition to a monthly subscription of 2s, with a penalty of £IOO and/or imprisonment. A crystal, receiver costs about £l, and the cheapest loud-speaker I set about £3.

REORGANISATION IN FINLAND. Apart from the relay taken by the Lahti high-power transmitter, the Helsinki .(Finland) ' broadcasts are now available through Viipuri,- where a new 13.2 kilowatt (aerial) ‘transmitter, working on 29T metres, has been' installed. Finland a radio system-has-been'.completely reorganised at a cost of some. 15,000,000 Finnish marks. FREE BRITISH LICENSES. The grant of receiving-licenses to permanently bedridden • persons in Great Britain by .the Postmaster-general without payment of any fee is the; aim of the Wireless Telegraphy (Bedridden Persons) Bill, the text of which was issued on March 11. , The issue of such licenses would be optional and under such conditions, and restrictions as the Postmastergeneral may think fit. The measure would not apply to persons.resident;in,a public or charitable institution or. a school. INTERNATIONAL" TELEPHONY. In addition to the.two,telephone cables already in use between Warsaw; and Berlin, via Posen, 1 two pew high frequency aerial lines: are: shortly to be installed, each of which will allow of several conversations being carried on simultaneously. The. extension of the service is necessitated not only by, its increased use between the two countries, but also between Poland and Great Britain, France, Holland, etc. -V | ' . t ( ■ . • CANADIAN CONTROL. Radio has presented Canada with a constitutional problem, namely, whether its control and regulation comes within the jurisdiction of the Dominion or the provinces. For three days counsel dealt with the intricacies of the question before the Supreme Court of Canada, and at the conclusion of the argument judgment was reserved. A wide range of subjects was traversed during the hearing. The case involved primarily the interpretation of those sections of -the British North America Act which defines the scope of governmental authority between the provinces and the. Dominion, but also embraced discussion of such technical matters as the nature of radio waves and the uses 'to which radio is put now or may b 6 directed in future. Up to the present the Dominion Parliament has assumed control, and has entered into international treaties and agreements respecting the allocation of wave lengths. It has enacted a law prohibiting the operation of a radio receiving set without a license. The province of Quebec challenged the Dominion’s right to controlbroadcasting, and the Dominion Government referred . the question to the Supreme Court of Canada. Qntario and New Brunswick generally supported the contention of Quebec. INCREASED GERMAN POWER. The construction of new stations in Germany has been under consideration by the Post Office authorities for, some months past. Sufficient funds have now ben granted, according to an announcement by the Minister of Posts, for the work to be carried out this year. Alterations at Konigs Wusterhausen have already progressed so far that the increase of the Deutschlandsender’s power by five kilowatts is likely to be achieved by the end of April. The Langenberg new 75kw transmitter has been built,, and will be ready this autumn. - A new high-power station will be built at Breslau, some 14 miles from the present station, also a new large station at Leipzig, and the power of the Frankfurt-on-Main transmitter is to be increased to 25kw. The two latter stations will exchange wave lengths when reconstruction is completed in 10 or 11 months’ time (says World Radio). The Post Office has decided to erect a relay station at Trier (Treves) this year, and it will be linked up with the Cologne or Frankfurt-Muehlacker group. SOUTH AFRICAN SERVICE. A wireless telephone service between South Africa and England will shortly be opened, according to an announcement made by the Minister of Posts in the House of Assembly. He said that the Government could not at present take the risk of spending large sums of money on the erection of wireless stations in view of recent inventions and constant changes; fit proposed eventually to erect its own station The Government had’-’rid intention of departing from its policy of keeping wireless as a State monopoly, but the Imperial Communications Company hud approached the Government and asked for permission to experiment with a limited service between Capetown and England. The Government proposed to allow the company to conduct a limited service without interfering with the Government’s right to, start its own service at any time, or to call upon the company to desist. CAN SETS BE SEIZED? Radio receivers, the- Danish Government has decided, belong to the category of articles which cannot be seized for debt. This repeats a recent German ruling on the point. According to a correspondent, a Berlin court has declared that a wireless set must be regarded as a “ household utensil ” legally exempt from seizure, since it fulfils an indispensable function in modern life. .We hear of a further curious case of special .interest to the set constructor.. A German amateur’s home-built receiver was recently held for ■ debt, but the seizure was regarded as irregular for two reasons; first; because it was a household article, and secondly because the price, obtainable at a public sale would not nearly correspond with the value of the work expended upon it by the constructor. SHORT WAVE TELEVISION, ' The German Post Office has - always displayed a great interest in television, and it is therefore noteworthy that quite recently they should have inaugurated a new scries of experimental television transmissions through the short wave .station at Doberitz. The station lies about halfway between Nauen and Berlin. Tele-cine apparatus is employed, as the Germans still have a great partiality for this side of the science. The transmitter is built up on normal lines, horizontal scanning being employed with a picture ratio of four horizontal by three vertical. Since the short waves are utilised—the station wavelength is actually 142.9 metres (2100 kilocycles)—a larger sideband spread is possible. This is taken advantage of by using 48 lines per picture (3072 pictures points), while the number of images per second is 25; that is, twice that, used in England. Flicker .in the resultant image is, in consequence, reduced, while a greater amount of detail can be shown. Reception tests within a small radius of the station have so far proved satisfactory, but one drawback is the weak modulation. A figure of 10 per cent, has been employed so far. The difficulties of wireless reception are greater than is the case on the medium broadcast band, bin, that is mainly a question of manipulation practice. - The power of this station is rated at 5 kilowatts, but the transmission times are indefinite. When “on the air,” however, the broadcast starts between 5 and „6 p.m., and continues till between 8 and 9 p.m., but so far there are no reports of signal reception having been undertaken in Great Britain. UNINSULATED WIRE. . No useful purpose is served by using insulated wire for the aerial or for the down lead. The only reason why enamelled wire is used on aerials is to avoid weathering wearing out the wire. Unless one is situated very close to the sea a bare aerial should last several years. The coating of oxide that forms on a bare aerial does not lower its efficiency. Copper wire has a lower resistance to high-frequency currents than any other metal except silver. The use of tinned aerial wire is not so good. High-fre-quency currents flow for the most part on the outer surface of wires. It flows along the tinned portion of 1 a tinned aerial. Tin has a resistance many tunes that of copper. The size of wire used in an aerial makes very little difference for reception purposes provided it is larger than 22 gauge. The 7/22 copper wire sold for aerials is very suitable for the purpose. If anything, it errs on the heavy side. Very few people have either the space or the money to erect 50-foot masts 300 feet apart. An aerial of this type, however, should be able to pick up 4YA, Dunedin on a crystal set in the Dunedin district. On exceptionally good nights it should be possible to hear some of the stronger Australian stations on a crystal. If any reader is able to indulge himself in such an aerial the results he obtains' would be interesting to hear about.