THE WIRELESS WORLD

Otago Daily Times, Issue 22723, 8 November 1935, Page 2

THE WIRELESS WORLD

NEWS AND NOTES

By Magna Vox.

Items of local interest are invited by “ Magna Vox ” for publication in tins column. It is necessary that such matter should reach this office by Tuesday of each week for insertion on the following Friday. 2BD, Sydney.—74o K.C., 405 metres. 2FC, Sydney.—6lo K.C., 492 metres. 3AR, Melbourne. —630 K.C.. 476 metres. 3LO, Melbourne. —770 K.G., 390 metres. SGL. Adelaide.—73o K.G., 411 metres. 4QG, Brisbane. —800 K.C., 311 metres. IYA, Auckland.—6so K.C.. 461.3 metres. 2YA. Wellington.—s7o K.C., 526 metres. BYA. Christchurch.—72o K.C., 416.4 metres. 4YA, Dunedin. —790 K.G., 379.5 metres. 4YO, Dunedin. —1140 K.C.. 261 metres.

ANSWERS TO CORRESPONDENTS. "Howler,” Waikouaiti —(1) Possibly, as you suggest, your coils are overcoupled, and the set has rather too much “ punch ” for stability. First of all, I would suggest placing a can over the IA6, 32, and PMIHI. See that the leads from the cape of the valves are very short, and, if you can, screen them in short pieces of copper braid earthed to the valve cans. If none of these ideas works out, send the coils to a reliable serviceman, explaining your difficulty and asking to have them tested. You may have got two-gain intermediates by mistake. (2) The last I heard of him ho was in England. I shall endeavour to procure hie address for you. (3) Thanks very much. I shall appreciate it. R. M. M‘D.. St. Clair.—The set is not very well suited for the broadcast band, as the tuning condensers are not big enough to cover it in one sweep. It would be necessary to work out coils which would do the job—probably two sets. I would suggest beginning with secondaries of about 100 turns for the lowest coil. To wind coils from 90 metres up, experiment until you get a coil that brings in the 80 metre stations with the condensers practically out of mesh. The choke could be used. “Circuit,” Gore.—(l) It is not permissible to use a screen-grid valve feeding straight into an audio transformer, as the plate impedance matching is incorrect. You would do better by connecting the plate and the screen of the

valve together, and using the valve as a triode. It will then give you better amplification and match th e transformer very much better. # The circuit will then, of course, remain just as> it is now. The condenser is there to act as an R.F. bypass for the signals flowing in the primary of the transformer. (2) Take my advice and leave well alone, unless you are absolutely confident that you can effect an improvement. After all, there does not appear to be much wrong with a set that can log the stations yours has done. LATEST LICENCE FIGURES. During the last six months there has been a remarkable increase in the number of radio listeners’ licences, the total reached on September 30 being 175,290, which exceeds the of March 31 by 22,801, representing an increase of nearly 15 per cent. Including dealers and 367 free licences, the grand total now stands at 177,683. Every part of the Dominion contributes to this progress, listeners’ licences being distributed as follows:Auckland, 51,040 (increase in six months 7402); Canterbury, 31,867 (4075); Otago, 24,342 (3378); and Wellington, 65,041 (7946).

POWER STATIONS LINKED. The Public Works Department have recently installed radio telephone sets at Mangahao and Waikaremoana. As the various hvdro-olectric generating stations are now linked for the supply of power, it is essential that communication between the stations be quickly effected at all times, and for this reason the wireless sets have been installed. During the tests excellent results were obtained, and there is no doubt that this additional medium of communication will be of considerable assistance to the Public Works Department is connection with their power supply schemes. The equipment, which was specially designed for the requirements of the department, was supplied by Messrs Amalgamated Wireless (Australasia), Limited. NO POLITICAL BROADCASTS. It must have come as a distinct surprise- to listeners to learn recently that after all the talk in the past about the “freedom of the air,” so tar ns political speeches by representative speakers of all" the political parties are concerned, that neither the Government nor the Opposition parties will avail themselves of the Broadcasting Board’s offer to broadcast political speeches during the election campaign. On the same day as this news was published there appeared in the newspapers a long cablegram stating that the leads of the parties in Eng land had delivered their election talks over the air. The natural medium of a political talk is surely over the air. Is it because at least two of the party leaders have platform personality that would not be known as a good broadcast personality? (asks an exchange.) Mora than town voters, those in the country will miss the privilege of hearing the party leaders oft the air.

THE ELECTIONS. The radio authorities have already plans well in hand for election night. Experience gained in previous elections indicates that after about 8.30 p.m. there will be very little normal programme and nearly all election news. Arrangements have been made to receive results as they come to hand. They will be broadcast from all stations as soon as received. In the early stages of the evening the news may be intermittent and interspersed with music. Later in the evening the stations will be handling election news almost entirely. Arrangements have been made to keep the stations on the air until at least midnight. If the situation warrants it, there is little doubt that the stations will close in the small hours of the morning. METAL TUKES. A good many people have asked whether the new metal tubes are better than the older glass envelope type. As the new tubes use the same filament, the same grid, and other electrodes as the older types, the functions of the two types should be similar. The metal tubes, however, have a smaller envelope*which can be used as a grounded shield, and this eliminates the ; ‘cans” of the glass type and simplifies set construction. _ Then, again, the base is smaller, and capacity and leakage can therefore be reduced. There are no reasons why the metal tubes should be worse than their predecessors and some why they may be a little better. The fact that they have not been universally adopted in American receivers for 1936 would seem to indicate that any superiority is not marked, and that some manufacturers are waiting to see how the public responds to the innovation.

CANINE ADDRESS. A unique “ public address ” installation ha s been fitted at the greyhound kennels at Northaw, Herts. Each of the 900 kennels contains a loud speaker operating either as a microphone or is a reproducer. When a dog creates a disturbance he unwittingly lights a warning lamp in the central control room, to which all the loud speakers are wired, and a keeper can at once address him individually with a few well-chosen words. NICKNAMES' PROHIBITED. The 8.8. C. has issued a now list of prohibitions on artists appearing before its microphones. No mention is to be made of trade activities or firms, or of theatres or institutions with which the artists are connected. Religion, political personages, infidelity, all forms of immorality, bodily defects, and * incurable diseases arc not to be referred to, and the peoples of countries are not to be given nicknames such as Yanks, Japs, Taffies, etc. NEW EMPIRE STATION. Extensive buildings and an elaborate new aerial system are to be constructed by the 8.8. C. for the Empire station at Daventry. These are to serve the two additional short-wave transmitters, contracts for which have lately been signed. The existing building at Daventry, which accommodated the old SXX national transmitters, will also be used for Empire equipment. Many programme improvements are being carried out, so that the 8.8. C. short-wave service, both technically and as regards material, will be second to none. Mr J. C. Macgregor has been appointed Empire programme director in succession to Mr J. B. Clark, who has become Empire service director. Mr Macgregor was educated at Edinburgh University and Trinity • College, Oxford. The number of recorded programmes introduced in the Empire transmissions is being reduced, and considerable attention paid to presentation. When it is necessary to “ dip ” into the home programmes, efforts are being made to ensure that items are not cut short at either end. Experimentally, a children’s hour is being introduced, and no programme is to exceed an hour. To avoid unduly long items, a play, such as “ Bulldog Drummond,” will be divided into two parts, transmitted at the same hour on successive days. Among the features being introduced to enliven the Empire programmes is one called “ High Spots,” in which commentators will ascend high buildings and towers throughout Britain

to give their impressions. The first talk wil come from the top of Albert Hall, which is 120 ft high. Among other “high spots ” to be visited are Blackpool Tower, Canterbury Cathedral, Edinburgh Castle, (he 8.8. C. transmitter at Moorside Edge, Greenwich Observatory, and the Eddystone lighthouse. 8.8. C. engineers now regularly study the sun from Broadcasting House through a telescope to chart the position of sunspots and note their effect on the Empire transmissions. On the information thus obtained it is possible to vary the wavelengths and obtain the best possible reception throughout the 24 hours. RECORDING PROGRAMMES. In general, there are three main methods of recording programmes or other material, namely, the magnetic wire or tape, the film, and the so-called gramophone record. The first of these has been used with considerable success in sundry parts of the world, and while it has many advantages, it has against it the fact that the tape or wire upon which the material is magnetically recorded is difficult to handle, both for rewinding and storage purposes. Film methods have reached a high degree of perfection in talking picture production, but for ordinary purposes are expensive, the deveolpment of the negative and the printing of positives being somewhat lengthy and skilled processes. The disc type of record in its usual form requires complicated and expensive apparatus and processes in the many steps that are necessary between the original performance and the final commercial product. In recent times the last type of recording has been developed and simplified, with th® result that it is now possible to cut a record, which, within a few minutes of production, may be used for reproduction. It is the latest applications of this method which are now finding most favour with broadcasting authorities. The popularitv of these methods is mainly due to the advance that has been made in the production of material from which the record is made, which results in a disc which can be rapidly and accurately cut and prepared for replaying,. and which wih give high quality results for a reasonable number of performances. Thq mechanism necessary for recordings of this type is. briefly, a constant speed drive for the turntable upon which the blank record is placed, and equally constant means for feeding the record-cutting mechanism across the face of the blank, and a cutting stylus or needle operated by the incoming electrical impulses and mounted upon the recording machine. These parts of the mechanism are not very different from those in the production of the commercial type of record, but, whereas the makers of these require master records and various intermediate matrices before the final pressing die is obtained, the apparatus used for programme purposes make’s its recording upon the disc which is subsequently used for the reproduction. There are many forms of material now available for this purpose. One of them is a disc of glass or aluminium coated with a gelatine compound. Another makes use of a solid foundation covered with a resinous type of compound, which, after being cut, is hardened by baking. Another form consists of an aluminium disc coated with various cellulose or acetate compounds, which, after being cut, is coated with a chemical solution, the effect of which is to harden rapidly the outer, surface and allow the recorded material to be reproduced within a few minutes of the cutting. Compared to the processes by means of which ordinary types of records are reproduced, these methods are at a disadvantage in that copies can only be obtained by making more than one recording at the same time or by making further records from the original, but for the ordinary purposes of broadcasting they fulfil requirements, providing a system which will give good reproduction with freedom from extraneous noise at a low running cost, combined with the production of a record which can be used almost immediately, and which is capable of being easily stored and is not liable to damage. Up to 50 reproductions can be obtained at a relatively low cost each. Many broadcasting authorities overseas have arranged mobile apparatus of this type which is able to attend at place and at times which would otherwise be inconvenient, and take a record which can be broadcast on suitable occasions later.