THE WIRELESS WORLD

Otago Daily Times, Issue 21993, 30 June 1933, Page 3

THE WIRELESS WORLD

By Magna Vox

NEWS AND NOTES

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 ot each week for insertion on the following Friday. ■- 2BL, Sydney.—j-855 K.C., 353 metres. 21 r C, Sydney.—66s K.C., 422 metres. 3AR. Melbourne.—62o ICC., 492 metres. 3LO, Melbourne. —830 K.C., 371 metres. SCL, Adelaide.—73o K.C., 395 metres. 4QG, Brisbane. —760 K.C., 385 metres. 3VA, Auckland. —820 K.C., 365.8 metres. 2 YA, Wellington.—72o K.C., 420 metres. 3YA, Chrlstcliurch. —980 K.C., 306 metres. 4YA, Dunedin.—oso K.C., 463 metres.

ANSWERS TO CORRESPONDENTS. “Voltage,” Cavershara.—The easiest method of ascertaining _ the set s consumption is to compare it with loads oi known value, such as lamps, - with .the set only connected to the house circuit observe the number of the meter disc in. say, one minute, ihen find out the nearest value of the lamp which produces the same number of revolutions when it alone is connected. “Amateur,” Ngapara.-(l) I am afraid you would have some difficulty in obtaining a copy of the volume you mention, as it has been out of print for some time. I am forwarding you my own copy on loan, and would draw your attention to the article on pages 82 and 83. As far as I know it was a Mr Stevenson of Gore, but in this connection I would suggest that you get_m touch with the manager of 4\A, Dunedin. (31 Tor obvious reasons I am unable to discuss in this column the merits of any particular set. I would suggest that if possible you have a trial of all three.. “Motor-boat,” Milton.—Try using a decoupling circuit, as resistance of, say, 10,000 ohms and a condenser of a couple of microfarads in order to stabilise the anode circuit. Motor-boating is often experienced with the modern detector, especially if a particularly efficient intervalve transformer is used in the anode circuit. Apart from this.... decoupling circuit, however, it is sometimes useful 'to put a stopping resistance m the grid •lead to the next valve.Tollowing the detector. This, idea is particularly useful when there is only one stage—and that a power stage—after _ the detector. The resistance can conveniently have a value of about 1000 ohms.

AGRICULTURAL BROADCASTS. Following a suggestion made at a meeting of the Board of Governors of Canterbury Agricultural College, Lincoln, it is possible that the college may establish a transmitting ; broadcasting station. In the meantime the chairman of the board (Dr H. G. Denham) will consult with some _ members ot the college staff. The assistant-lecturer in chemistry, Mr E.. W. Hullett, has stated that he is willing to organise the establishment of a transmitting .station, and he asked permission of the board to continue with that work. The director (Professor R. E. Alexander) explained during the discussion that with a transmitting station members of the college staff would be able to give lectures of interest to farthers at specified, times each week. The meeting decided, that full information should be obtained of the possibilities of the suggestion made, and the question will be discussed again next month. AN UNAUTHORISED. TRANSMISSION. The funniest thing on the air .during the last week (states an exchange) wass a wrestling relay from Adelaide through 6CK. It was not the announcer that, provided the fun, but some female tans near the mike. One of these was evidently a friend of a native son who was engaged with a Frenchman, and her cnes to the referee and her advice to her friend “Billy” were unique. Put in the rabbit-killer, (Silly! Stun him, Billy! ” she screamed when the Australian was on top. “He’s choking him, Ims choking him! ” was her agonised wail when the Frenchman applied a stranglehold, This went on through the event, and had to be heard be; appreciated. PATENT RIGHTS PAYMENTS. Over £14,000 was paid to Amalgamated Wireless last year to cover the patent right contributions of New Zealand listeners. The agreement was ds per registered listener, paid from the license fees collected by the department. This agreement is now to be terminated, but it is likely that another one will be negotiated very soon. If it results in a considerable saving, this saving could be put to no better purpose than the staffing of the YA head office with a thoroughly competent, experienced programme director (states an exchange). Un the technical. side our national stations are now- in charge of capable men ot wide-training, with expert advisory engineers, but the programme side sadly lacks experienced direction in several branches. If this defect were remedied quickly there would be a marked lessening in the complaints one hears on all sides about the quality of YA evening sessions. TAGS FOR LEADS. Those little celluloid tags which you buy for slipping on to battery and other leads are very useful and look most professional, but they have an annoying liabit of getting lost when you are building a new receiver. It is a most unwise proceeding to try to connect up a set without being sure of -the correct leads at- a glance, 1 and tying a varying number of "knots in the battery cords—one for HT.+, two for G.B.—, three for L.l.—■. etc. —is not a satisfactory idea, despite its popularity. The simplest method is to beg, borrow, or steal from the family mending basket a. number of pieces of coloured wool, which can he tied round the leads and make identification a matter of seconds. Another method is to buy a dozen or so of those little circular labels which are supplied in all colours by stationers for sticking at the bottom ot important business correspondence. Uney denote enclosures or something of the sort.) When stuck round the leads these tags make most handsome identification discs, and the appropriate lettering can ■be written on in ink. THE CHILDREN’S HOUR. Every child has his hour a 8 a radio listener,'and in these youthful radio fans wd have the critical listening public ot to-morrow. The children’s hour from the British Broadcasting Corporation owes its beginning to a child-loving official who some years ago used to come to the microphone in the afternoons, and for an hour or so told children’s stones or .recited verse likely to appeal to the child mind. From such simple beginnings sprang this now famous “hour’ which aoea the even tenor of, its way from year to year, having its faithful daily audience of thousands ot children. What most appeals to these children in the way o| radio entertainment? Mr John Kettelwell, who runs the children’s hour and la anectionately known to his listeners as J .K.. says that any song or story connected in any way with animals immense favour. It is not without significance that music i s definitely growing in appeal to children. The other day there was broadcast for them a special hour of dance music, featuring the old dances, such as the polka and ‘ Sir Roger. ibe experiment was a great success. Historical plays or broadcasts from the Tower of London, or any word picture of events that smack at all of the glory that is England, strike home to the children. They like to know what manner of men aim women founded the Empire in which they live. It is intensely difficult to judge the sucess of these childrens broadcasts, so twice every year “Request Weeks” have been organised. Children are asked to vote (for the most popular items broadcast “hour” during the previous six months. Then request programmes are arranged consisting or the types of entertainment proved by this ballot to be the most well favoured. One stern fact must be borne in mind: that the children’s hour is first and foremost designed and intended for children, and not for grown-ups. It is not the fathers and mothers, but the children themselves who are regarded, and rightly so, as the final court of appeal. N LONG-DISTANCE RECEPTION. Reception of stations thousands of miles away from the receiver has always had an appeal to the majority of set owners, although it is doubtful if such long distance reception has any entertainment

value. Yet an opportunity of picking up American or Japanese broadcasting stations operating on the medium wave band is never lost. Reception of this kind has been made much easier of recent years because the power used by broadcasters has, in most instances, been considerably increased, while receivers of the modern multi-valve variety are generally extremely sensitive. Nevertheless, it is necessary, if a station is to be picked up, that its signal strength should be in excess of a certain minimum value, otherwise the unpleasant electrical disturbances commonly known as “ noise ” will override and drown the signals, in which case no amount of sensitivity in the receiver will help. It is not always the most powerful station that is heard best, while at certain intervals, generally of some years, results improve considerably. It has been - found that these favourable conditions for long-distance broadcast reception occur at certain staged of sunspot activity, viz., the time when they are at their minimum. They are in this condition now. and were in 1923. The manner in which signals arc conveyed away from a transmitter is complicated. Part of the signal energy travels out along the ground, while part goes upwards into the sky. The relative amounts which take these two paths are determined by many things, among which the design of the transmitting aerial plays an important part. The ground wave, due to the resistance of the soil and rocks of the country over which it passes and its nature both ae to shape and degree of dampness, dies away comparatively rapidly, and ultimately ceases to exist. The part of the signal which travels upwards, of course, is useless for reception purposes, at any rate in districts close to the transmitter, but in its upward journey it ultimately reaches a layer of atmosphere about 60 miles from the surface of the earth._ In daylight this layer of air or gas is affected by the rays from the sun in such a manner that the sky wave, on reaching this layer, is ’either absorbed, in which case its energy is almost entirely used up, or is reflected in such a w’ay that it does not reach very great distances. At night time when the sun’s rays are removed this layer undergoes a change, and complete absorption of the waves does not take place. They are then free to travel on to greater heights until they meet another layer some ISO miles or so above the earth. This layer, due to difference of atmospheric pressure and other conditions, differs from the first, and The waves are deflected from their straight paths and are ultimately bent back to such an extent that they travel again towards the earth, meeting it hundreds of miles away from the station to provide unexpectedly strong signals. At the surface of the earth the wave is again reflected and goes up again, to meet with further reflection at that distant part of the sky to return again to the earth at a distance equal to about twice that of its first return. The process is re-, peated again and again, but at each reflection, either at the earth or in tlje sky. some strength, is lost, and it sooner or later becomes useless for the purpose of reception. The condition of the reflecting layer up above the earth undergoes daily r variation and seasonal variation, and also the much slower variation in step with the sunsoot cycle of ten or eleven years. .Improved reception at long distances is consequently obtained as night replaces day, and still further improvement is noticed as the night proceeds. Also in winter, when the sun has less time to make its presence felt upon the atmosphere, signals qre audible at greater distances, while, since the effect of the sun ia determined to an extent by the sunspot activity, still further improvement may be expected at a period of sunspot inactivity, such as exists to-day. The wavelength of the signal has an important bearing _ upon the behaviour of the wave after it has left the transmitter, and the features mentioned above are not associated with all frequencies, while all sorts of unpleasant effects, due! to interference of different * waves commonly known as fading, make themselves felt, and on occasions spoil reception.