ON THE SHORT-WAVE.

New Zealand Herald, Volume LXVII, Issue 20678, 25 September 1930, Page 3

ON THE SHORT-WAVE.

PROGRESS IN SCIENCE. RECEPTION IN DOMINION. CONCENTRATION OF SIGNALS. With tho approach of summer weather conditions for short-wavo work are rapidly improving. Now Zealand, since it is practically at tho extremity from the world's leading stations is well situated for short-wavo reception. In tho following article Mr. R. J. Orbell, 8.E., of Auckland, a well-known Auckland experimenter, and a member of tho Byrd expedition to tho Antarctic, describes tho birth of short-wavo work, and the progress made in that branch of wireless. Mr. Orbell writes:— •' During the past years it has been the dream of radio enthusiasts to be able to listen to programmes from stations in all parts of the world. The ability to sit at one's receiver and swing tho dial first to London, then Paris, then New York, and so on round the world, haß for many years presented a powerful appeal to the imagination. This was in tho early days of radio. More recently, tho advent of short wave transmission, and a certain little peculiarity attached to it, has indeed mado this wish come true. Experimenters discovered the fact that, when very short wave-lengths are used tho signals have what is called ' skip effect,' That is to say, waves jump right over near by receivers in their travel and come to earth again at very great distances, thus losing practically no enorgy by motion along thq. earth's surface, " Prior to this all-important discovery engineers built stations to operate on very long waves in the belief that their signals would travel over great distances more effectively than with medium wave-lengths as wero used originally. In this assumption they were correct. It was found, however, that very high power indeed was necessary if the signals were to be heard on tho other side of the world. Another serious difficulty with the use of these ultra-long waves was met with. This was that static interference which was found to be very much more troublesome than with the medium waves, sometimes rendering operation entirely impossible, yery high lattice towers were necessary and the cost of stations ran into many thousands of pounds. First Use o! Ultra-Short Waves. " Then the pendulum swung in the other direction, and strangely enough the first to make satisfactory use of ultrashort waves were amateur experimenters. They had been allotted the use of these very short waves by their respective Governments who believed that these were useless for commercial purposes. The amateurs communicated over astounding distances with extremely low power, with barely any static interference, and at a cost that was infinitesimal when compared with that necessary for tho long waves then in use by the Governments. " Naturally all attention was turned to theso short waves as offering immense commercial possibilities. New Governmentowned short-wave stations grew up almost over-night. Beam stations which concentrate tno waves in one direction wero developed and operated morso at high speed irom one country to another. Experimental short-wavo stations were erected in various countries for the purpose of transmitting, musical programmes to other countries, and great success was met with

"Two years ago the British Broadcasting Corporation erected a station at Chelmsford, about twenty miles from London, with tho express purpose of conducting experimental transmissions to tho Dominions of the normal London and Daventry programmes. Interest in these daily transmissions became world-wide, and a vast field was opened for broadcast listeners ill the Dominions possessing short-wavo receivers. Development in America was at the same time proceeding along similar lines. Tho high-powered short-wave stations of tho General Electric Company, 2XAF, 2XAD, and 3XAL, were erected at Schncctady close to Now York. Others wero 9XF at Chicago, BXK at Pittsburg, 6XN at Oakland, California. These stations, now rapidly being supplemented by numerous others, continued to transmit daily programmes, tho recoption of which, although subject to slight fading at times, was found to bo quite satisfactory in all quarters of tho globe. Attention in Holland, Germany and Australia was also turned to shore-wave broadcasting, until to-day the rapidly expanding list of stations includes sovoral hundreds of cull signs. Ideal Position o! Dominion. " Those possessing short wavo receivers will bo interested in tho recent cabled announcement from London stating that the British' Broadcasting Corporation intends further to develop its service to the Dominions by tho construction of a super station, capable of reaching all parts of tho Empire even under adverse conditions. Following on this announcement, comes another indicating that Vienna, Budapest and Warsaw are to bo connected by a relay chain with London. This will mean that programmes presenting tho world's foremost Continental artists will bo available for transmission by tho new British short-wavo station.'

The geographical position of New Zealand is ideal for reception from British and Continental stations, in as much as it is close to their antipodal points. Strange as it may seem at first sight, when we locate a receiver as far as is possible from a transmitter, that transmitter is actually received', many times more strongly than if it were closer. The reason for this is that waves tavelling from a transmitter in genenfl follow groat circles on tho earth's surfaco. Since all great circles originating at one point meet again at anothor point exactly opposite on the globe, it is not difficult to understand then, why reception is bettor at that point. That partly is what actually happens in actual practice, and although refractions and reflections duo to tho two twilight bands somewhat modify this result, nevertheless tho concentration in Now Zealand of European transmissions is most marked. Communication to Antarctic. "On the voyage to the Antarctic on the City of New York, of the Byrd, Expedition, one was able to follow closely tho effect of this concentration of signals from European stations close to the Antipodes. As the ship moved further south, European stations became weaker than in New Zealand, whereas stations in the United States became somewhat stronger. Incidently this occasion made one realise more than over the incalculable value of short-wavo radio in maintaining contact with remote places over groat distances. When long-wave apparatus failed to maintain contact with the closest land, twoway communication was carried on daily with New York us easily as over an ordinary telephone. Regular weekly short-wave broadcast transmissions from America to tho expedition members in that remote locality enabled the latter to hear distinctly the voices of their friends and relations at home, as well as .musical entertainments provided by these stations. "Although short-wavo broadcasting is now becoming very popular with radio listeners, it will never supersede the longer waves for short distance transmissions, on account of the ' skip effect' referred to above. The owner of a modern long and short-wavo receiver has* the choice of either short and medium range programmes on long waves or extreme distance on short waves. Ho has either at his command and so is enabled to realise, in fact, the dream of tho early experimenters. The limit of his set is the world."