THE WIRELESS WORLD

Otago Daily Times, Issue 21975, 9 June 1933, 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. 'lt is necessary that such matter should reach this office by Tuesday of each week for insertion on the following Friday. 2BL, Sydney.—Bss K.C.,'353 metres. 2FC, Sydney.—66s K.C., 422 metres. 3AR. Melbourne—G2o K.C., 402 metres. 3LO, Melbourne. —830 K.C., 371 metres. SGIj, Adelaide.— 73o K.C., 395 metres. 4QG, Brisbane.—76o K.C.,'385 metres. IYA, Auckland. —820 K.C., 365.8 metres. 2YA. Wellington.—72o K.C., 420 metres. 3YA, Christchurch. —980 K.C., 306 metres. 4YA, Dunedin.—6so K.C., 463 metres. ANSWERS TO CORRESPONDENTS. “Home-made,” Mosgiel.—l know only too well the difficulty of fastening oft neatly 7/22 copper wire after it has been threaded through or around an insulator. Try this method: Separate the wires after they come through the insulator, and lay them along the main part of the wire; then, starting with one wire, twist it round and round the separated wires and the main wire close up to the insulator. “ Farad,” Waimate —(1) Connect across the loudspeaker or from any a.f. circuit to the filament, a condenser With or without a resistance in aeries. Values will depend upon the characteristics of the existing components and the degree ot control required. A variable 25,000-ohm resistance and a .01 mfd. fixed condenser across the speaker would be suitable. (2) I am doubtful whether you would find the job within your powers. It is a complicated arrangement, and I should advise you to consult an expert. (3) Messrs Whitcombe and Tombs, Ltd., Princes street, Dunedin. G. R. M., Dunedin.—Automatic tons control is not very well known in this part of the world, although manufacturers and designers of sets are now giving this matter a good deal of attention. A set so fitted automatically varies the range of audible frequencies so that it can reproduce as the strength of the signal changes. Thus, when the signal from a station is strong enough to overrule a 1 “noises” maximum fidelity is provided, in that all high notes are produced. When the signal is relatively weak the higher frequencies, and hence a certain pioportion of noise and “ mush, ’ is also cut out. THE 8.8.C.’S INCOME. Last year the British Broadcasting Corporation had a net revenue ot £1 628,738, which was £203,388 more than in 1931. Even this large sum does not enable all difficulties to be overcome, ns the report states that there is not yet a solution of the problem of conveying humour purely by oral methods witnin the limitations of microphone and programme policy.” This problem is not peculiar to Great Britain. LICENSE RENEWALS.

There were more renewals of radio licenses in April, the first month of this financial year, as compared with the number which expired on March 31, than ever before. Renewals never equal the total of those which have expired, but this year’s decrease of 14.4 per cent, is the lowest on record —last years figure being 15.4 per cent. The decreases in the previous four years *ere: 1931 26 6 per cent.; 1930, 26.7 per cent.; 1929, 19 per cent.; 1928, 24 percent. The number of licenses renewed in April was 81,75.), compared with the 95,580 expired on March 31. Of the 81,759 licenses 80,246 are for receiving sets, there being b7U dealers', licenses, 563 transmitting, one experimental, two special, 246 freeand 25 broadcasting. A total of 23,026 of the paid receiving licenses are from the Auckland district, the other totals being. Wellington, 32,467; Canterbury, 14,007, Otago, 10,746.

EMPIRE SHORT WAVE SERVICE. With regard, to the Empire service on the short waves, the experts, both in England and New Zealand, are mutually aware that reception conditions in tms part of. the world are bad. In fact it has been decided from June 1 to make drastic alterations in the times of transmission. A tentative scheme has been arranged whereby transmission will take place on 25 and. 32 metres at the following revised times:—-June and July> i to 0 p.m.; May and August, 4.4.) to 6.4. i; April and September, 5.30 to 7.30; March and October, 6.30 to 8.30; Februaiy and November. 7 to 9; January and Decembei , 7.30 to 9.30. It is known as a result or •tests that signals will be at;-their, best during those hours. Unfortunates the programme value of the Transmissions a those' 'hours is practically nil. A ROYAL BROADCAST. The opening of the World Economic Conference by His Majesty the King u London, transmitted on short wave, and rebroadeast by the four national New Zealand stations, will be heard by Dominion listener's at 5.30 p.m. (New Zealand time) on Tuesday, June 13. His Majesty’s voice was last heard by N Zealand listeners on the occasion ot the Christmas Day broadcast last year. Owing to the fact that the Kings speeches timed to he delivered at approximately 130 a.m. New Zealand time, the radio ■authorities have decided not to broadcast the speech direct. In coming to this decision the authorities have been faced not only with the awkward time but with the fact that during those early morning hours the chances of receiving short-wave radio from England are practically nil. Arrangements have bee i made, however, to broadcast a lecoidecl version of the speech at 5.30 p.m. om June 13 There is not the slightest doubt that in’ making this decision the radio authorities have adopted the correct tactics. Admittedly a .recorded version of an event is not so thrilling as the event itself. But it is certainly better than asking listeners to sit up into the small hours 6 of the morning to be regaled with world samples of static. PAPER CONDENSERS. A small point with regard to paper condensers of high capacity may be responsible for uncertainty when a stocic of existing components is to be used in building a new receiver. The non-in-ductive condenser has only been manufactured in large quantities during the last few years. Condensers or earlier vintage will probably be inductive, and, unless they can be guaranteed as tree from this property, there may be a natural hesitation to use them, even though they may be rated to withstand the voltages existing in the receiver, these doubts may be set at rest by saying that there is very little risk of Double through using inductive condensers in any position except where hi. currents are to be dealt with. Accordingly, old condensers may be employed in l.f. circuits for by-pass and decoupling purposes, ana also for smoothing, but they should not be inserted in the anode, grid, or screenin«r grid circuits of the h.f, amplinci. With regard to the detector-anode circuit, where both hi. and l.f. currents are handled, the position is not quite so clearly defined, but as a general rule the use of inductive condensers is not likely to do serious harm. Any paper condenser of high capacity will almost invariably be on the “ dead ” side of any hi. filter that may be included in the circuit. A DIFFICULT AUDIENCE. “The British race are an extraordinarily difficult people to entertain, declared Sir John Keith, director-general of the British Broadcasting Corporation, in London recently, at a luncheon ot the Thirty-two Club —a club composed mainly of Socialist candidates defeated at the last general election. “We all know the English take their pleasures sadly, salt Sir John. “Go into a fashionable hotel and watch people dancing, wearing a vacuous artificial grin or perhaps the furrowed brow and the air of anxious concentration appropriate to a serious or even agonising operation. Is that pleasure? I feel in magnificent form when a good dance, tune is supplied on the wireless, although I abominate the socalled ‘hot’ jazz music. A tune like ‘ Hallelujah ’ is as good for me, and as stimulating to any kind of effort, as anything I ever hear. I sometimes wish it were possible to introduce a kind of Continental gaiety—at any rate on occasions. Can you imagine London going carnival for n day or two? Would it not be a good thing? ” Turning to the constitution of the British Broadcasting Corporation Sir John said: “One of the theories I propound is that whether or not one may believe as I do in the democratic 1 manciple, one will not achieve it by demo-

cratic methods. The 8.8. C, ig an exceedingly interesting and important experiment in public management. Devise if you can a democratic method of running the 8.8. C. What you have is obviously the possibility of public control over!major policy, initially in the shape of a charter or a license. The public interference in management—can you have that? Don t criticise the 8.8. C. constitution because the programmes are in your opinion rotten, and don’t consider the programmes rotten because you dislike the form of control.” Sir John vigorously defended the 8.8. C. against ehai'ges of deliberate political bias. “On the matter of political bias the 8.8. C. will not submit to the charge of anything deliberate, either in that or in any other sphere, and every elfort is made to obviate the charge of bias in the political or any other field,” he added. y SHORT WAVE HINTS. It is true to say that the main factor governing the choice of any type of broadcast receiver is the question of the power supply available, and this is not less true for a short-wave receiver. If the supply is alternating current the most convenient type of short-wave receiver is one which takes its supply from the mains without the use of batteries. The actual current consumption of a wireless set is very low, being only of the order of 40 to 60 watts, i.e., that taken by an ordinary electric lamp. If electric mains are not available at the point where the receiver is to be used, but if either _ electric mains or battery charging equipment is available at a short distance from the place where the receiver is installed, a good solution to the power supply difficulty would be to install accumulators both for low tension and high tension supply. Another method is to use a large capacity low tension accumulator, which not only provides the low tension supply direct, but which is also used to drive a small rotary converter which provides the high tension supply. Special precautions have to be taken to prevent the converter from creating electrical disturbances which interfere with reception, but machines are now available which are specially designed for the purpose, and which incorporate the necessary silencing device to suppress this interference. It is, of course, necessary that there should be no serious difficulty in recharging the low tension accumulators. This method has the advantage that the heavy duty low tension accumulator is very much more robust than the small high tension accumulators, and is less likely to be damaged in transit for recharging. Indeed, the normal type of accumulator battery, fitted as a starting and lighting battery on a motor car, is entirely suitable for this purpose, let another method of obtaining high tension supply is by the use of dry high tension batteries. ’The initial cost of these is considerably less than that of high tension accumulators, but they cannot be recharged when exhausted, and have to be thrown away. It is not possible to judge the performance of high tension batteries in hot climates merely from a knowledge of their performance in a temperate' climate, where they are used in very large numbers and with entire satisfaction for this purpose. In tropical and humid climates it may be found that a type of cell known as the “inert” cell may be advantageous. This type of cell is not rendered active until it has been filled with water.