RADIO NOTES

Dominion, Volume 25, Issue 222, 15 June 1932, Page 6

RADIO NOTES

By •

“ETHER"

CURRENT TOPICS

Some people interested in radio may have already seen in "The Dominion” that the powers-that-be have recently produced a further spate of regulations connected with matters radio. In this case attention has been turned to the components incorporated in sets that derive their power from the mains. The new additions to the rules are more a matter for the trade than the listener. Nevertheless it might be wise to make inquiries if the set being purchased breaks any of the new regulations. The maximum temperature for mains transformers incorporated in a radio set has been set admittedly high at 176 degrees, but some of the cheaper sets must come perilously near this maximum. Another point in these new regulations that is somewhat vague is the rule that “reactances” must not be used to reduce supply pressures. As every mains transformer in every a.c. mains set in the world is no more than a special form of reactance this new regulation, if taken seriously, would appear virtually to make the sale of mains sets illegal in New Zealand.

Next Saturday, station 2YA is to rebroadcast opera from Sydney if conditions prevailing at the time make this possible. As this opera, “Lucia de Lamermoor,” will be picked up by the official shortwave listening posts in this Dominion on 2ME’s wavelength of about 32 metres there is very little likelihood of disappointing musiclovers. For some curious reason these short waves from Australian stations have given consistently good results on nearly every occasion, including the opening of Sydney bridge. The trouble that occurred during that rebroadcast cannot be blamed upon mother nature. Lovers of opera might therefore make a note to tune-in to 2YA at 9.30 p.m. New Zealand time this coming Saturday. It is expected that the proceedings will last some three hours.

A curious position has arisen in connection with the questionnaires distributed by the Broadcasting Board tor compilation by listeners. As was mentioned previously, May 31 was the final date for sending in the completed forms. Before that date the postbag showed that listeners were sending along some 400 or 500 forms every daj. Just after the closing date there was a slight reduction .in returns, but the cascade now shows every indication of returning to normal.- The authorities are therefore faced with the fact that while they have officially closed tor questionnaires, the public have decided to overrule the closing date. As it would be absurd to begin an analysis of these forms until the flood of 300 or 400 a day abates somewhat, the broadcast authorities are philosophically waiting for things to moderate before beginning analytical operations.

It is understood that efforts will, be made by 2YA on Sunday to rebroadcast the proceedings at the Eucharistic Congress, Dublin, Ireland. At 11.10 P-m. New Zealand time, if are suitable, the transmission from SSW, 25.53 metres, will be picked up in B elllngton and rebroadcast on the usual wave-length of 417 metres. As the time of this conference is not particularly suitable for good short-wave reception, it is possible that the authorities may not be able to do justice to the occasion. Listeners who possess short-wave sets may be interested to know that in addition to SSW the Vatican station HVJ will also be broadcasting the proceedings, which include Pontifical High Mass, on a wave length of 19.84 metres.

In a paper read recently by Mr. T. L. Eckersley, 8.A., B.Sc., before the Institution of Electrical Engineers, it was disclosed that deductions from the behaviour of short waves over long distances, when used in the Marconi facsimile method of transmitting pictures by radio, showed that waves of 15 to 50 metres normally pierce the Kennelly Heavside Layer at a height of 100 kilometres, and are reflected by tho Appleton Layer, which is electrically denser, at a height of 300 kilometres. By the way, it was stated also, that as the maximum density of the Appleton Layer is half as great again now as it was in 1928, the ultra-violet light from the sun is less intense now.

There seems to be no end to the possibilities of vacuum tubes. At a recent meeting of the American Physical Society representatives of the General Electric Company of New York announced the invention of a valve said to be 1000 times more sensitive than its predecessors in the measurement of minute voltages. This valve, with an exhaustion of one billionth of atmospheric pressure can detect voltages of one ten-millionth of one volt —which is a voltage of the order of magnitude of that which is produced by a heart beat, for the detection and recording of which a portable electro-cardiograph can now be supplied.

Several of the big electrical concerns in the United States either have already, or have applied for, experimental licenses for television. Television in the home, according to many wellknown American engineers, is reckoned to be at least three, if not live years in the future. Some even go so far as to put the time when television will be in any sense a useful, practical home entertainment as far as ten years ahead. The television licenses granted by the Radio Commission arc on an experimental and temporary basis. This is because, whilst the Commission thinks that experiments in television should be encouraged, they do not see their way to grant a permanent license which would he based upon "pub; lie interest, convenience or necessity." « * * Paris listeners are suggesting that the local broadcasting authorities should go to Morocco to learn how a go-ahead broadcasting service should be conducted. It appears that “Radio Maroc” has outstripped all other French stations by its enterprising developments within the last year, particularly in the direction of educational transmission. Every school in French Morocco now has its own receiver in addition to a cinematograph installation, radio lessons being illustrated by Hints forwarded in advance by the Public Education Department. * * * On April 1, 1932, the wavebands open for amateur telephony in U.S.A, were alloted as follow: — (a) Open to any amateur: 1875 to 2000 kc/s (IGO to 150 metres) ; 50,000 to 60,000 kc/s (53.57 to 50 metres), (b) Open only to amateurs specially licensed for unlimited radio telephone operation: 3900 to 4000 kc/s (76.9 to 75 metres) ; 14.150 to .14/150 kc/s (21.20 to 91.05 j»9tre«l c

BAND PASS TUNING

Famous Expert’s Opinions The following remarks on band pass tuning may be scathing, but coming as they do from the late chief engineer of the British Broadcasting Company, Captain P. P. Eckerslie, they are well worth considering. Writing in “Popular Wireless,” he says: Some of these band-pass units are a. snare and a delusion. A reliable friend told me he had measured up one or two and found not only the primary intended response, but one fifty kilocycles away from that response as well! To my mind, “band-pass” is a muchabused term. It usually means an asymmetric response, too wide for modern conditions, and requiring an accuracy and skill in adjustment outside the powers of most people who operate the set. The theoretical value of band-pass is that you get more upper frequencies and a flatter response. Few people realise that the loudspeaker response is such as to compensate for the theoretical bad qualities of peak tuning. Again, the peak tuning, device particularly where reaction is used, has the profound merit of increasing the intensitivity of the local or wanted carrier. This, in turn, gives a much better detector efficiency, and, in creating strong demodulation effects, gives an enhanced selectivity provided the low-frequency response cuts off quickly above 6000 or so. And In modern conditions this must be done. The band-pass so called may even reduce carrier-wave strength and give too little bass to a loudspeaker already deficient in that quality.

MUSIC COMPETITIONS

List of Prize Winners The following is a list of the prizewinners in the Music Lovers’ Competition, recently broadcast from all the Broadcasting Board’s stations:— IYA: First, The McEwen Family, 180 Renall Street, Masterton; second, B. Lawrence, 1 Ferguson Avenue, Mairehau, Christchurch; third, Miss Jean Bailey, “Farleigh,” Union Street, Rotorua. 2YA: First, L. W. Coker, Parker Street, Blenheim; equal second, Miss Mara Mackie, Otakcho, Hawera, and Mrs. J. A. Pettigrew, Main South Road, Otakeho, Hawera. 3YA: First; Alf. Lawrence, junr., 39 Cornwall Street, St. Albans, Christchurch; second, W. Adorian, 236 a Oxford Terrace, Christchurch; third, Arthur E. Brightling, 40 Middleton Road, lit ecar ton, Christchurch. 4YA: First, A. G. Williamson, 54 Evans Street, Opoho, Dunedin; second, The McEwen Family, ISO Renall Street, Masterton; equal third, Mrs. Emmerson, 54 Driver Street, St. Kiida, Dunedin, and Miss D. B. Beck, care P.O. Box 25, Dunedin.

RADIO HANDBOOK

Facts for Listeners The 1932 Radio Handbook Annual, published in Christchurch by H. G. Farnall and Co., contains an immense amount of information upon every modern feature in radio. This volume is not intended only for technical-minded enthusiasts. Others will find between its pages all manner of information upon receiving matters. The article on the choice of a receiving set should appeal to a large number of individuals at present on the brink of owning receiving sets. Some interesting maps arc given to indicate the probable crystal range for the various YA stations. Incidental to the main articles are numerous tables, charts, and diagrams, that give information on practically everything In radio worth knowing.

METAL BASEBOARDS

Beware of Shorts When making up a. set on a metal base, or upon a baseboard covered with a metal sheet, it is pretty obvious that special care must be taken to avoid any short-circuits or accidental contacts. But it is surprising how easy it is to make an accidental contact without knowing it, and really you should take extra special eare to examine every component which you fit on to the metal base so as to make sure that there is proper clearance between all the parts.

UNIVERSAL TIME

Many wireless problems might be solved with the adoption of universal time, as suggested by a correspondent in the "Morning Post.” “Now that wireless is a universal factor, particularly on short wavelengths,” he writes, "and that the matter of longitude makes timekeeping between transmitter and receiver end always one of difficulty, would it not be possible to adopt a Standard Universal Time what 1 might call ‘Earth Time,’ based on the diurnal 21 hours? There are so many systems of Standard Time that they are apt to be confusing. What I suggest is simply this: The World Standard Hour would start at Greenwich, and all wireless equipment would take its time from it, so that, say. one o’clock Earth Time at Greenwich would be oue o’clock all over the world.” British listeners would certainly benefit by the new order of things, but it is doubtful whether America, for example, would submit to the confusion of sitting down to afternoon tea at 10 p.m. and tuning into the nightly dance music at 4 o’clock in the morning. And would Russians consent to go to bed at 7 o’clock in the evening?

As we stand to-day we have to face the fact that broadcast transmissions and gramophone reproduction are tending to swamp every other form of musical entertainment, so that the generation now growing up is likely to have little opportunity of hearing music direct, and will take as a standard the quality of electrical reproduction, says the “Wireless World.” All this brings us to the conclusion that we have either to try to copy the standard which direct musical performances provide, as far as practical limitations permit, or we must be content to adopt a new standard with a convenient arbitrary cut-off in the frequency rangi and cease to worry about striving to attain uerfect reproduction of the originalperforroanc®. Whists 5® It to bs?

AMPLIFICATION FACTOR

Theory and Practice Many amateurs think that the total magnification which is obtainable should be proportional to the amplification factor of the valve. This is not surprising, because, after all, to the average person the phrase “amplification factor” means what it seems to say, and that is, a simple measure of the total amplification obtainable. The fact is, however, that the magnification depends not simply upon the particular factor defined as the amplification factor, but upon a number of others as well, of which the most important is the impedance. The impedance, in fact, is quite as important as the amplification factor. Then you might think that if you had two valves of the same impedance but of different amplification factors, the one with the greater amplification factor would give the greatest overall magnification. If the two valves were used alternately in the detector position it is probable that the above would be true, but there are some cases where it would not be true. For instance, In a screengrid stage, of two valves otherwise equal, but one having a greater amplification factor, the latter would quite possibly give inferior results to the former owing, for instance, to the circuit being rendered unstable. If Instability set in, it would complicate the tuning, and in order to get out of these difficulties you might reduce the screen-grid voltage so as to bring back stability, but then the total amplification might be no more than (or even less than) that which you would obtain with the other valve. Not only this, but with a correspondingly reduced grid-bias voltage you might also have overloading and distortion.

ANODE BEND DETECTORS

Impedance Hints Talking about valve impedances, a writer in an English paper states that when a valve is used for anode-bend detection the impedance of the valve is often greater than the specified value, owing, of course, to the different conditions In which it is used. The specified impedance is often taken at zero grid bias at a standard H.T. voltage of, say, 100 volts. When the valve is used for anodebend detection it has a negative bias applied, and the result of this is that the working point of the valve is moved toward the lower curved part of the characteristic curve. The impedance, nevertheless, is greater than the specified value, and it is therefore important when considering the use of a particular valve for anode-bend detection to have in mind very carefully the type of coupling which will be used with it. For instance, a different type of valve will be needed for transformer coupling from that required with resistancecapacity coupling. If a valve has a fairly low impedance transformer-coup-ling will probably be quite satisfactory, but if the Impedance of the valve is high, it may be preferable to use a resistance coupling.