RADIO NOTES

Dominion, Volume 25, Issue 264, 3 August 1932, Page 14

RADIO NOTES

By

"ETHER "

CURRENT TOPICS The ideal method of obtaining accurate data as to the true character of the broadcast service in different localities, the Coverage Commissioners have pointed out, would be by means of a very extended series of field strength measurements and listening tests, but it is. not perhaps generally appreciated just how extended such measurements would have to be to give an accurate indication of conditions in those areas which depend on night time sky-wave reception. In such localities it is well known that conditions vary, not only from minute to minute and from day to day, but also from season to season, and even from year to year. To get a true perspective picture of average conditions would, therefore, involve measurements carried on over a long poriod of time. The above arguments do not, of course, apply with the same force in the case of field strength measurements in the immediate neighbourhood of a transmitter where the ground wave is predominant even at night time.

Assisted by eminent radio invest!gators, the Radio Research Board of Australia has demonstrated a new method of detecting the approach of bad weather from points thousands of miles away, and not connected with any meteorological station. Static has been found to be caused by lightning flashes and practically all such atmospherics emanate from the low depressions which bring bad weather. By using a wireless direction finder, with Canberra and Melbourne as observing points, the investigators have been able to prove the feasibility of novel longrange weather forecasts. » » »

In view of the recent report of our own Coverage Commission who have turned down the idea of utilising the longer waves of 1000 to 2000 metres, it is interesting to read the suggestions put forward by Captain P. P. Eckersley, late chief engineer to the 8.8. C., as a solution to Australia’s coverage problem. He declares after careful investigation that the only way to serve 90 per cent, of the population is by means of six long-wave stations. Unless this is done, he states, adherence entirely to the normal wavelengths in the vicinity of 200-600 metres cannot possibly cover more than 14 per cent, of the area required, even if money were unlimited. Admittedly, our own problem is somewhat different. Nevertheless, if Captain Eckersley’s calculations are cor-rect-one, or at the most two, longwave stations would cover the whole of New Zealand with little difficulty. If this were a practical proposition the saving involved and the high standard of programme it would be possible to distribute would make the scheme very attractive. ».• • ■

Listeners may have noticed that there has recently been a change in the wavelength of station 4YA, Dunedin. This change has been made temporarily during the Olympic Games in order t» avoid.a possible clash with KFI, Los Angeles. During the Olympic Games, therefore, it has been arranged that Dunedin shall transmit on a frequency of 550 kilocycles or, roughly, 555 metres. This will remove all chance of the two stations heterodyning. It is hoped as a result that the rebroadcasts of results of the Olympic Games by the broadcasting stations in New Zealand will be made as clear as possible. As mentioned in the news some little while ago, the broadcasting authorities have made arrangements with station KFI to'transmit a summary of results of the Olympic Games every day at 7.30 p.m., New Zealand time. As station KFI is. probably the best, received American station in New Zealand it is considered there is every prospect of the transmissions being most successful.

The efficiency of Marconi telephone equipment: for ship-to-shore communication was fully demonstrated during a world cruise of the Canadian Pacific liner Empress of Britain, which, concluded recently after a voyage covering more than 36,000 miles and calling at 26 countries. By means of the Marconi wireless telephone installed in the liner direct conversations were carried on by passengers with. England, Italy, United States of America, Canada, Australia, Hawaiian Islands and the Philippines. Wireless telephone communication was maintained with Rugby from the time the Empress'of Britain left England until she arrived at Yokohama, and the ship was in touch with Ocean Gate, the American telephone station, until she was beyond Colombo. ' Passengers were able to speak directly to their friends ashore from their own cabins or from any room in the ship where a telephone was installed.

Something like 200 towns in both islands were visited by the Radio Coverage Commission, and representative deputations were interviewed. In addition to the places actually visited, contact was made with a number of outlying districts either by telephone or by correspondence. During the tour of both islands, which occupied about two months, a total distance of over 40<;0 miles was covered by motor-car, in addition to some steamer and train travelling in the South Island.

The tour of investigation of the Coverage Commission was very greatly facilitated by the cordial assistance provided by the telegraph engineers and postmasters throughout the country. These officers were kept advised in ad-, vance of the itinerary. They not onlyarranged meetings and deputations of representative interests, but also collected much useful information as to reception conditions iu their districts. When it is realised that, on an average, the commission travelled over one hundred miles a day, holding sometimes as many as six meetings, it will be appreciated that, but for the efficient advance staff work of the postal organisation, the task would have been quite impossible of accomplishment in anything like the time actually taken.

Wireless has been well represented in the applications for patents during 1931, according to the report of the Controller-General of Patents, Designs, and Trade Marks-, issued in England on June 8. Inventors seem to have concentrated on securing selectivity without sacrifice of quality, but much attention has also been given to short-wave arrangements and the redistribution of broadcast programmes by landlines. In television, efforts'have been directed to the replacement of apertured scanning discs by other scanning means such as reflectors, moving arcs, and cati>~ 1 e rays.

French listeners are renewing their hopes for the establishment of a regular broadcasting system as a result of the appointment as Postmaster-General of M. Queuille, who is expected to “rule the waves” so long as the present Government holds power. He is keenly interested in wireless as was shown when, as Minister of Agriculture, he initiated, in,1927, a vast project for the employment of radio in rural districts to check the exodus of the country population'to the towns.

RADIO AND RELIGION Miles of Loudspeakers BIG DUBLIN CONGRESS Nothing in any way comparable with the arrangements for the local broadcast throughout Dublin of the Eucharistic Congress has ever before been attempted. In size and complexity the. system is the largest that has ever been installed anywhere in the world. The svstem was devised by Mr. T. J. Monaghan, Engineer-ln-Chief of the Irish Post Office, in collaboration with Standard Telephones and Cables, Limited, London, who supplied the entire equipment and operated it in conjunction with officials of the Irish Post Office. The aim of the system was to enable every member of the vast crowds congregated simultaneously in the fifteen acres at Phoenix Park and along the processional route and the adjacent streets to hear every word of the Masses and every dote of the music by means of loudspeakers. Some 500 loudspeakers were used for this purpose, these being placed in front of the Congress altar in Phoenix Park and along nearly 13 miles of streets. The heart of the system was In Phoenix'Park. Here, to cater for the vast congregations, there was a great row of 32 powerful loudspeakers mounted In pairs on 16 poles that stretched in a line extending for about half a mile from the altar. Each speaker had an audible range of half a mile, and as the pairs pointed in opposite directions, the proceedings were audible all over an area one mile wide extending for half a mile from the altar. There was also one special loudspeaker mounted close to the altar, which was used to amplify the music of a harmonium up to the volume of an organ. This accompanied the special Congress choir of 600 singers and the children’s choir of 2700 boys and girls. • It is interesting to note that only by the use of a loudspeaker system could the singing of such a vast, congregation be properly synchronised. Without it a pronounced time lag would be inevitable, and those standing at a great distance from the altar would have been singing well behind those nearer up. The music from the altar was, however, carried by loudspeakers instantaneously to even the most dis- 1 tant speaker unit, and the singing of the whole congregation was therefore kept In absolute unison. The amplifiers for the Park system were situated in a room at the extreme left wing of the Colonnade. Some idea of the power of these amplifiers can be gained from the fact that they employed 33 thermionic valves and that there were 11 stages of amplification, requiring a power of 3 J kw. from the electricity supply mains. Six microphones'were .used,' placed in different positions in front of the altar and among the choir. The system for covering the processional route from Phoenix Park to O’Connell Bridge and the adjacent streets was divided into 10 sections, each with its own amplifier station. These stations covered in all 13 miles of streets, along which over 400 loudspeakers had been installed, so placed that there were no zones of silence between the speakers, and no "blind” spots where nothing could be heard. It was possible to use the loudspeakers in the streets for broadcasting over the city the Masses and the singing from the fifteen acres or from the Pro-Cathedral, and the closing ceremony and benediction from O’Connell Bridge. They were also employed for sending out special Instructions and notifying arrangements to the crowds. It required some 50 miles of wire to connect up all these loudspeakers with the system which, it should be emphasised, was not a system of wireless broadcasting, but one of relaying amplified sound over land-lines. A SHORTWAVE TIP Improved Reception The following short-ware tip given by “W.L.S.” in “Popular Wireless” is well worth trying. He says try, if possible, a short aerial broken in the centre with the receiver attached at the. break. That is to say, dispense with your earth, connect half of the aerial to your aerial terminal and the other half to your earth terminal. It does not matter about making the two halves exactly equal in length; one may be outside and the other running across your room away from it. But do see that the receiver is equipped with two lengths of wire, one running in each direction from it. I venture to prophesy some interesting results to.this experiment; I have certainly had some myself. ADDING REACTION Amateur designers seem often to be in doubt as to the desirability of fitting a reaction control to their receivers, and on several occasions lately advice has been asked on this subject, says an English expert. Deservedly enough, reaction has a bad name for bringing about poor-qual-ity reproduction, apart from interference with other wireless users. But it is often overlooked that it is the misuse, and not the use, of reaction that is responsible for these troubles; provided that the reaction control is handled intelligently, its presence can hardly do any haem, and, of course, it need only be used on tho.se occasions where extra sensitivity is needed. Apart from the question of sensitivity, it is often useful to have some ready means of offsetting to a great extent the necessarily heavy damping that is imposed upon a tuned circuit by the modern form of grid detector. Consequently, one is always inclined to advise the fitting of reaction control, except, perhaps, to sets with two or more H.F. stages. A SCREENING HINT The usefulness of metal-cased H.F. leads is now widely appreciated, but-lt is most unwise to apply the principle of screening indiscriminately when following a published design. By making serious'additions to the amount of stray capacity existing in the various circuits —and this addition is bound to occur, however carefully the screening may be done —it may be found Impossible to “gang” the set satisfactorily, and in any case the wave-range covered Will be considerably reduced.

POWER INTERFERENCE Problem of Reduction TROUBLE WIDESPREAD In all radio-minded countries consideration. is being given to means whereby interference with broadcast reception may be eliminated, or at least reduced to a minimum, says the report of the Coverage Commission. The elimination of atmospheric interference, or static, as it is more commonly called, has so far evaded practical treatment. Other sources of electrical interference, such as result from electric power lines and appliances connected therewith, are more or less remediable, however, and it is these sources of disturbance that are seriously engaging the attention of all enlightened countries.

This problem has more than an indirect bearing upon broadcast coverage and for this reason figured largely in our discussions with listeners and local power and lighting authorities. During our tour of investigation opportunity was taken to gain first-hand information as to the nature and extent of such interference in the different localities visited, and to encourage, as fas as possible, co-operative action between the various interests Involved. We fully realise that one solution of the problem lies in the direction of an adequate increase in the power of transmitting stations, so that the signal-to-nolse ratio would, in all cases, have a sufficiently high value. This, however, would be a very unpractical and one-sided way of overcoming much electrical interference in remote localities that is comparatively easily remedied. It is now generally recognised that the problem is one for mutual co-operation by all parties concerned.

In general It may be said that power and lighting authorities and in many cases users of interfering electrical equipment viewed the subject very sympathetically. They submit that the problem of interference location and elimination needs to be placed upon a more definite and satisfactory footing than obtains at present, where no legal responsibility seems to devolve upon anyone and where very little co-ordinat-ing action is being taken to ensure the active co-operation of the various affected parties. It is quite clear from our observations that electrical interference with radio reception is widespread throughout New Zealand; that broadcast reception is in many areas seriously affected; and that, incidentally, what may be termed the radio power and lighting load is, in many centres, seriously prejudiced by reason of the high noise level and the resulting inability to use the superior amplification of the average electric set The latter, under the circumstances, is of no more value than a low-priced, low-powered battery set. The problem is, therefore, one that affects not only the listener, but also, on the economic side, power and lighting authorities, radio dealers, and, indirectly, if not directly, the Broadcasting Board. NOISES OFF Latest 8.8. C. Ideas In the studio at Broadcasting House, London, which supplies, effects, or accompanying noises, it was odd to see the mixture of primitive and scientific devices, writes Nelle M. Scanlan. A basket of ■ broken china and glass supplied just that sound when shaken. A heavy chain lay on a pile of gravel. On a large table, divided Into sections, some covered with wood, some rubber, some metal, a knob of wood like a door handle can be manipulated to represent a horse galloping or trotting, whether on cobbles or a modern roadway. Cylinders of compressed air will hiss steam like the panting of an engine starting out of a station. A sheet of iron hung from the wall, with a large drum, gives the rumblings of thunder. A motor horn, a large bath of water, which will yield the wash of the sea to microphone ears, a host of other things, including a wind machine, were but a few of the many gadgets of the effects department Gramophone effects also they have in store; a crowd will cheer and yell; the murmur of a waiting mob; the gaiety of Hampstead Heath on bank holiday, all these can be turned on at appropriate moments. VOLUME CONTROL A Simple Solution A high-resistance potentiometer, with the aerial joined to its slider,, and the resistance element connected across the aerial and earth terminals of the receiver, makes an effective, if somewhat crude, pre-detection volume control. Provided that the resistance is reasonably high in value, the connection of this device should not introduce any appreciable loss of signal strength when the slider is set at he maximum position. UNWANTED NOISES Hints for Tracing This article, by Marcus Scroggie, gives some idea of the myriads of unwanted noises that find their way into a radio set. Writing in the “Wireless World,” he sayslf the origin of unwanted noises is not sufficiently obvious from the character of the sound it must be traced by elimination, first removing the aerial to distinguish between external Interference and internal fault, bearing in mind that certain internal faults do not give rise to noise until something is being received for tnem to work on. Apart from atmospherics there are scores of sources of interference in these days of multitudinous electrical appliances. Battery-chargers, fans, cleaners, refrigerators, signs, tramcars, violet-ray machines, automatic telephones, cinema projeeto.rs, and many other things add a background, or perhaps even a foreground, of roars, rustles, bangs, pops, crackles, and other effects. The 8.8. C. time signal has been criticised, but the same thing many times louder, throughout programmes as well as intervals, is the fate of those who live close to crossings on arterial roads which are furnished with flashing beacons. The silencing of these varied disturbances is a separate subject, which, incidentally, might with advantage be tackled in this country as energetically as in Germany. Supposing, however, that the noise originates within the receiver, it is usually a simple enough matter to locate it, gradually cutting things out from the aerial end until the noise stops, and then concentrating on that last thing.

CONDENSER SIZES Price and Ratings Ratio The difference between a paper condenser rated to work at 250 volts and one rated for 500 volts lies almost entirely in the paper used to insulate one set of foils from the other, says “The Wireless World.” It is fairly evident that the thicker the paper, others things being equal, the greater is the voltage necessary to puncture It and allow a current to pass. In consequence, condensers are made with various thicknesses of dielectric material in order that, whatever the voltage they may be called upon to withstand in the set, a suitable pattern may be obtained. One might quite reasonably ask whether it would not be enough to take into consideration the highest voltage ever met with in any receiver, and make all condensers with paper thick enough to be safe from breakdown on that voltage. If it were only a question of the paper that simple arrangement would probably be found extremely convenient, but there are other factors.

If, say, a 4-mfd. condenser is taken to pieces, and then rebuilt with a paper four times as thick as that previously used, it is true that the condenser will now stand without breakdown about four times the voltage that could safely have been applied to it before the alteration. But its capacity will now be 1 mfd. owing to the greater separation between the foils. If we want to retain the original 4 mfd. while increasing the safe voltage four times, we shall therefore have to rebuild four low-voltage 4-mf<L condensers and connect them in parallel The resulting block will now contain sixteen times as much paper (four times the original area, and four times as thick) as the original 4-mfd. low-volt-age condenser. While the rebuilding process just described is hardly practical, the description of it does bring out that in making the condenser safe for a higher voltage a great deal more is involved than the mere substitution of one thickness of paper for another. In terms of price, one would expect that a 2-mfd. condenser rated to work at 800 volts would cost about twice as much as one rated to work at 400 volts. Reference to catalogues issued by manufacturers shows that, generally speaking, this price-relationship is not far wrong. MODERN SALESMANSHIP The super-salesman of the future, flying in his own aircraft from terri-' tory to territory, and gathering information by wireless, is foreshadowed by the report that the Shell Company has ordered Marconi apparatus to be installed in one of its aircraft The Shell Company has for some time used aircraft to increase the speed and mobility of its selling organisation, and the addition of wireless will be a further aid in facilitating safe and rapid movement by air from one country to another. The Marconi equipment selected, known as the type A.D. 228., is extremely light and compact, and has been specially designed for convenient use in light • aircraft It is a telephone set, and no previous experience of wireless is necessary for its operation. Incorporating a transmitter as well as a receiver, this equipment not only enables the pilot to receive the weather and landing reports which are .now regularly broadcast from aerodrome ground stations, but also gives him the means of telephoning to the ground stations and asking directly for any special Information that he may require, such as directional assistance in conditions of bad visibility. <