SHORT WAVE RADIO

Hutt News, Volume 3, Issue 24, 6 November 1930, Page 11

SHORT WAVE RADIO

(By B. J. Orbell, B. E.)

Inuring the past years it lias been, the dream of radio enthusiasts to be able to listen to programmes from stations ia all parts of the world. The ability to sit at one's receiver and svyingthe dial first to London, then to Paris, then to New York, and so on round! the world, has for many years presented a powerfal y appeal to tfce imagination. This was in the early days of radio.

More recently, the advent of short wave transmission, and a- certain little peculiarity attached to it,' has indeed rngyjjfc tMs wish come true. Experimenters oafccovered the fact that when very short "wave-length are used, the signals Jwive what is called "skip effect". That is to say, waves jump right over nearby receivers ia their Havel aiid come to •earth again ?t very great distances^ tiißß losing practically no energy by aaotion along the earth's surface.

Prior to this all-important discovery engineers built stations to operate on very long waves^in the belief that their <rifrnft]« would travel over great distances more effectively than with medium wavelengths as were used originally. In Hub assumption they were correct. It was found however, that very high .power indeed was necessary if the signals were to be heard on the other, side of the world. Another serious difficulty with the use of these ultra-long waves waa met with. This was that static interference which was found to be very much more troublesome than with the medium waves, sometimes rendering oper ation entirely impossible. Very high lattice towers were necessary and the cost of stations ran into many thousands^ of pounds.

Then the pendulum swung in /the other direction, and strangely enough itxe first to make satisfactory use of ultra ehort waves were amateur experimenters. They had been allotted the use of these very short waves by their respective (Governments who believed that these werft 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 the long waves then in use by the (tavernmentft.

Naturally all attention was turned to these short wave sets offering immense commercial possibilities. New Govern-ment-owned short wave stations grew tip almost over-night. Beam stations which concentrate the waves in one diree turn were developed and operated morse

at high speed from one country to another, fcxperimental short wave 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 Chelmsfofd, about twenty miles from London with the express purpose of conducting efxpeifanjanta^ ttransflesions to the Dominions, of the normal Londan andi Daventry programmes. Interest in these daily transmissions became worldwide, and a vast field was opened for broadcast listeners in the Dominions possessing Short wave^xeeeivers. Development in America was at the same time proceeding along similar lines. The high powered short wave stations of the General Electric Coy., 2XAF, 2XAD and 3XAL were erected at Scrnectady close to New York., Others were 9XF at Chi- j eago, BXK at Pittsburg, 6XN <afc Oakland, California. These stations, now rapidly being supplemented by numer- i ous others, continued to transmit daily | programmes, the reception of which al- | though subject to slight fading at times was found to be quite satisfactory in all quarters of the globe. Attention in Holland, Germany and Australia was also turned to short wave broadcasting till to-day the rapidly expanding list pf stations includes several hundreds of call signs. - Those possessing short wave receivers will be interested in the recent cabled -announcement from London stating that the British Broadcasting Corporation intends further to develop its service, to the Dominions by the construction of a super-station, capable of reaching al) parts of the Empire even under adverse conditions. Following on this announcement comes another indicating that Vienna> Buda pest and Warsaw are *to be connected by a relay chain with London. This will .mean, that programmes presenting the ; world's foremost continental artists will be available for transmission by the new British short wave station. The geographical position of New Zealand is ideal for reception^ from British and Contintental 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 &a 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 travelling from a transmitter in general follow great,circles on the earth's eta face. Since all great circles originating \ en. the point meet again at another point f I exactly opposite on the globe, it is not' difficult to understand then, why recep- *

tion is better at that point. That partly is what actually happens in actual practice and although refractions and reflections due to the two twilight bands somewhat modify this result, nevertheless the concentration in New Zealand of European transmissions is most marked).

During a recent trip to the Antarctic on the "City of New York" of the Byrd Expedition, the writer was able to follow closely the effect of this concentration of signals from European stations close to the Antipodes. As the ship "moved further south European stations- heeaxne weaker than in^Ne*". Zealand whereas stations : in the United States became somewhat .stronger. Incidentally this occasion made 'one realise more than ever, the incalculable value of short wave ra'dio > in maintaining contact with remote places over great distances, when long wave apparatus failed to maintain, contact with the closest land/ two way communication was carried on daily with New York as easily as over an ordinary telephone.

Regular weekly shortwave broadcast transmissions from America to the Expehdition members in. that reinoteVocality 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 Avave broadcasting is now becoming very popular with radio. listeners, it will never supereede the onger waves for siort distance transmis sions^ on account of the <fSkip effect" referred to above. The owner of a modern long and short wave receiver has the choice of either short and medium Wange programmes or long waves or extreme distance on short waves. He has either at his command and so is ena,bled to realise in fact, the dream of the early experimenters. The limit of his set is the world.

The ordinary broadcast set will not re-' ceive shortwave stations but there are one or two receivers on the market specially constructed to receive short wave as well as ordinary .broadcast programmes. A New Zealand newspaper recently published a running description of the last test match and received it direct from the Oval in England On one of these short wave broadcast receivers.