THE WIRELESS WORLD

Otago Daily Times, Issue 22373, 21 September 1934, 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. It is necessary that such matter should reach this office by Tuesday of each week for insertion on the following Friday. 2BL, Sydney.—B3s K.C., 353 metres. 2FC, Sydney.—66s K.C., 422 metres. 3AR, Melbourne.—62o K.C., 492 metres. SLO. Melbourne. —830 K.C.. 371 metres. SCL. Adelaide.—73o K.C., 393 metres. 4QG, Brisbane.—76o K.C., 385 metres. XYA, Auckland.—6so K.C., 461.3 metres. 2YA, Wellington.—s7o K.C., 526 metres. 3YA, Christchurch.—72oK.C., 416.4 metree. 4VA Dunedin.—79o K.C.. 379.5 metres. 4YO. Dunedin.—ll4o K.C.. 261 metres, ANSWERS TO CORRESPONDENTS. G. M. D., Dunedin. — (1) It appears to be a “vibrator" type of eliminator, but the vibrator is wrongly connected. _lt would work, but there may be smoothing difficulties due to the wave form of the secondary current. (2) The degree of interference would depend on the type of set used. Without good shielding, etc., there may be trouble. (3) Yes, the insulation between the cathode and the filament of the rectifier is good enough, and the same battery can be used. (4) An ordinary voltage divided would do. “249,” Hilderthorpe.— (1) Yes. I should have them tested if I were you. A certain amount of deterioration is inevitable, and there is frequently a falling off in quality, etc., which is so gradual that it may not readily bo noticed. (2) If the noise disappears when the aerial and earth terminals are I short-circuited you can be sure that the 1 set is free from blame. If not, you . should have the set overhauled. “ Battery',” Omararaa.—B .Batteries of ' the dry cell type should when new show i an open circuit voltage of slightly over j 45 volts per black. As the batteries are ; used the voltage gradually drops until a | certain voltage is reached, then it drops . very rapidly until the batteries become useless. Before this rapid drop occurs an active chemical decomposition takes place within the batteries, and this action manifests itself by causing poor reception, weak signals, crackling noises, spluttering, etc., or a high-pitched whistle in the speaker. Replacing with new batteries is the only remedy for such noises. TALKS TO STUDENTS. The series of talks arranged by the 1 Broadcasting Board for the benefit of candidates for the matriculation examination will be continued this afternoon, when the talk on history (which was commenced last Friday) will be continued. These talks, which are of 25 minutes’ I duration, are given at 4.30 p.m., a time which should prove suitable to most students. The remainder of the schedule is as follows : English, September 24 and 28; geography, October 1 and 5; mathematics, October 8, 12, 15, and 19. NEW ZEALANDER HONOURED. Mr David M. Tombs, M.Sc., son of Mr and Mrs Harry Tombs, of Wellington, has been awarded a Robert Blair Fellowship in applied science and technology, tenable for one year to enable him to carry out his studies in research with Professor Dr Zennech, at Munich, into short-wave propagation and reception, with special reference to the problems associated with the .short and ultra-short waves that are likely to be used for television. Mr Tombs is an old boy of Nelson College, who went to London six years ago and gained his Master of Science degree at London University. For the past two years he has been engaged in the research branch of Messrs Siemens, Limited, of Woolwich, on the completion of which engagement at the end of the present month he will leave for Germany, When at Nelson College Mr Tombs was keenly interested in radio, having established the amateur transmitter 26 H, which he operated wfith quite good results. Air H. N. Shrimpton, radio operator on one of the vessels of the first Antarctic expedition led by Rear-admiral K. E. Byrd, was at Nelson College at the same time, being the operator of 281. ATTRACTIVE VOCAL BROADCAST. Madame Elsa Stralia made her broadcasting debut in New Zealand from 2YA, Wellington, last night, when ehe gave a brief recital. From the same station tomorrow evening she will occupy a prominent place on the programme of the charity concert arranged by the Broadcasting Board at the Wellington-Town Hall. Among the other artists scheduled for this concert are Mr A. Tyrer (pianist), Madame N. de Lornay, M. Scnia Chostiakoff, and the Wellington Symphony Orchestra. DOMINION LICENSES. There were 132,861 paid_ licenses for receiving sets in the Dominion at the end of July, new licenses for the month having totalled 3993, which is slightly more than the increase in the corresponding month last year. The grand total of licenses connected with radio in the Dominion on July 31 was 134,956 —over 4000 more than the previous month. Besides 132,861 receiving licenses, there are 982 dealers’ permits, 797 for transmitters, three experimental, 287 free, and 26 broadcasting. Just when New Zealand will have reached its maximum number of licenses is problematical. In England already nearly a quarter of the population have receiving sets. If that standard were attained in New Zealand, there would be nearly 400,000 licenses issued, or a total of over half a million pounds given by the public for broadcasting purposes. MOTOR CAR RADIO. New Zealand will probably experience before long a pronounced wave of popularity of radio sets in motor cars. Sets are now on the market specially designed to meet broadcast conditions in the British dominions, which are vastly different from those in the United States. In the United States, where most of the car radio sales are made in cities such as New York, Chicago, San Francisco, and others, there ate anything up to a dozen powerful stations in each city which almost any set could pick up satisfactorily. New Zealand is very similar to Australia and Canada in that there ure comparatively few stations. In consequence sets of good performance have to be installed to secure satisfactory reception when driving at distance from the location of stations. Car radios are becoming better with each model marketed, and there is now no reason why a motorist in this country should not be able to drive anywhere to the strains of music, provided he is willing to pay the price asked for a really good car set. EMPIRE TRANSMITTERS. A British official wireless message states that call signs and wavelengths in metres at present employed by the British Broadcasting Corporation’s Empire short-wave transmitters are as follow: —GSA, 49.50 metres GSB, 31.55 metres; CSC, 31.30 metres; GSD, 25.53 metres; GSE, 25.30 metres; GSF, 19.82 metres; GSG, 16.86 metres; GSH, 13.97 metres. The hours of transmission are (Greenwich mean time)o.ls to 8.15 a an., GSD and GSB; 11 am. to 1.30 p.m., GSG and GSF; 1.43 pan, to 3.45 pan., GSF and GSE; 3.45 pan. to 5.45 p.m., GSE and GSB; 6 p.m. to 10.30 p.m., GSD and GSB; 11 pah. to midnight, GSD and GSC; midnight to 1 a.m., GSC and GSA. GILBERT AND SULLIVAN RECITALS. New Zealand to-day enjoys more Gilbert and Sullivan comic opera on the air than any other country in the world. The Broadcasting Board was negotiating for over two years before it secured the broadcasting rights, but now that this has been arranged listeners certainly seem to be getting a feast of that form of entertainment: The remainder of the programme of G. and S. hours for September and October is : September 21, 8 to 9 p.m., from IYA, 2YC, 3YA, and 4YO; September 24, 8 to 9 p.m., from IYX, 2YA, 3YL, and 4YA; October 2, 8 to 9 p.m., from IYA, 2YC, 3YA, and 4YO; October 9, 9 to 10 p.m., from IYX, 2YA, 3YL, and 4YA; October 18, 9 to 10 p.m., from IYA, 2YC, 3YA, and 4YO; October 23, 9 to 10 p.m., from IYX, 2YA, 3YL, and 4YA. Grand opera broadcasts are also regular now, at least one of the four stations giving such a broadcast once a week. The schedule of future grand opera recordings is : 3YA —October 7, "Carmen”; November 4, “Faust"; December 2, “Tannhanscr”; January 6. “Aida ”; February 3, “ Rbinegold and Siegfried. ’

2YA—-October 14, “ Butterfly Novem--her 11, “ParsifarDecember 9, “La TraviataJanuary 13, “La Tosca - ; February 10, “ Carmen.” 4YA —October 21, “Rbinegold and Siegfried”; November 18, “Aida’; December 16, “Tristan”; January 30, ‘ II Trovatore February 17, “Twilight of the Gods.” 1YA —September 23, “Tristan”; October 28, “11 Trovatore”; November 25, “Twilight of the Gods’'; December 23, “La Boheme”: January 27, “Valkyrie’; February 24, “Parsifal.” DIRECTION FINDING. Prior to the application of wireless in a practical manner, navigation had reached a comparatively high state ot efficiency, but there was always the difficulty that bad weather, fog, and other natural conditions were likely to render a ship “ blind.” This possibility has been almost entirely removed by the application of wireless methods of checking position, not the least useful of which is direction finding or variations of this principle which enable a bearing to be obtained or a position to be fixed practically independent of weather or other conditions. This use of wireless has developed continuously for the last 20 years or more until it is one of the essentials in modern navigation, while its value to air services, both commercial and military, is inestimable. Although the principles of direction finding are not employed in broadcasting, they are probably familiar to many, especially those who have operated sets such a.s portable receivers in which a closed loop or frame aerial or equivalent device was used for picking np the signal. With this type of pick-up apparatus the signal from a particular station is at a maximum when the plane of the aerial is directed towards the station, the signal gradually decreasing to a minimum as the plane is rotated to a position which places it at right angles to this direction. It would seem that simple apparatus of this sort would almost lie sufficient for determining the direction in which a series of known points lie, but there are numerous practical difficulties which make more elaborate gear necessary if accurate observations are to be obtained. For one thing the direction of the transmitter can only be properly observed with aerials which are true loops, but as any loop aerial and its associated leads is also more or less effective a a a vertical aerial an error is likely fo creep in, because of the vertical pickup, and an indefinite zero position is the result. The zero or minimum position is used for obtaining the direction rather than the maximum, because near the minimum position the change of signal strength ia comparatively rapid, and may, therefore, be more readily observed. It is therefore necessary to apply some means for getting rid of the vertical pick ; up effect. One of these consists in encasing the aerial in a metal tube which has a gap therein so that the tube docs not form a closed loop similar to that of the aerial itself. There are also numerous other precautions to be taken if the results are to be relied on for their accuracy. Many of the difficulties to be avoided are caused by the change of the direction of the signal which has to be picked up, due, for example, to the proximity of metal structures which, especially on board ship, introduces serious complications. In many cases it is necessary to make experimental observations and apply correction factors in much the same way as is necessary to adjust a ship’s compasscs_ and apply corrections before true readings may be obtained. Still further and more serious complications are introduced if the observation point is so far removed from the transmitter or is receiving signals of such a wavelength that waves returning from the upper atmosphere form either part or whole of the received signal. Such waves in the process of reflection are apparently twisted and turned to such an extent that their apparent direction of propagation may he changed. If comparatively longwavelengths are used, reasonably accurate results may be obtained for distances of 100. miles or more, hut if medium or short wavelengths are employed the effective distance is considerably reduced until it may not he possible to rely upon the accuracy of the observations tor distances of more than 10 miles —that is, when the simpler types of direction-finding equipment are used. The causes of errors are now becoming well known, and much work has been done in producing systems which ensure that the error-making influences are neutralised or removed. The problem has been mainly attacked on the basis of making use of aerial forms and systems which are unresponsive or_ less strongly influenced by the distorted signal. Modem equipment is therefore much more complicated than the simple loop mentioned above. HERE AND THERE. Dr Hopkins has invented what lie terms a “ voting machine ” for attachment to the home electric wiring- The f machine enables householders to, vote “yes” or “no” by merely pressing one of two buttons, the total vote being indicated by current recordings at the power distribution centre. This invention has been proved to be practicable, but is not likely to have widespread use. Several of the American broadcasting Stations, have, however, recently arranged for listeners approving of their programmes to switch on an additional electric light in their homos at the conclusion of items found to be enjoyable. By observing the graphs of the varying number of units distributed at the power house the broadcasting authorities have formed a really valuable idea of the popularity of the different items. * sje $ Representatives from England and seven other European wireless authorities recently met in Paris to consider the question of electrical interference as it affects radio reception. For the present the conference is concentrating on fixing reasonable standards and determining what protection can be attained practically. Ultimately it is hoped to persuade manufacturers of electrical equipment all over the world to prevent interference in excess of the amount determined. ❖ From Coventry, England, comes information as to the method employed by a vicar to overcome dfficulties arising through the breakdown of the large organ in his church. The vicar had a small portable harmonium, and to it he coupled a five-valve power amplifier working into several loudspeakers fitted in varous parts of the building. The outfit has proved so satisfactory that it is ptobable the large organ will never be repaired. * * Theoretically stations should come in on the same dial number on all machines, but in practice this is not the case. There are two main reasons for this. The first is that the dial can be fitted to the tuning condenser in practically any position, thereby changing the relationship between dial numbers and the opening of the condenser plates. Next, the effective inductance of the coils varies with the number of turns, and there is no standard coil winding. Another factor is varying designs of tuning condensers, especially in the shape of the plates. At Berne, Switzerland, recently, the International Bureau of the Telegraph Union took over control, in an international sense, of all forms of radio transmission, and adopted a new word, “ telecommunication,” as properly descriptive of all forms of telephone or telegraph, signs, signals, writings, images, or sounds, whether sent by line or radio or visually. At the same time the body altered its name to International Telecommunication Union, but retained its headquarters in Berne. It is significant that there has been little alteration in wavelength allocations apart from new reservations for short-wave broadcasting on wavelengths of 11.72 to 11.28 metres, between which limits there is room for no fewer than 100 short-wave stations without any overlapping. Although it is 12 years since broadcasting started in this country, there is no established technique of announcing, as appears to be the case in Belgium and France (says a writer in au English journal). Both countries have recently seen the establishment of schools for broadcast announcers. “In the syllabus of the Paris Ecolc du Micro, which I have been privileged to inspect, a quite elaborate course of study is laid out. The would-be announcer begins his studies with articulation, reading aloud, punctuation, and the pronunciation of foreign ; terms.” The time is rapidy approaching j when New Zealand will also have to do ' something in this direction. 1