RADIO TOPICS.

New Zealand Herald, Volume LXIV, Issue 19658, 9 June 1927, Page 16

RADIO TOPICS.

I ANNOUNCER'S RESIGNATION I

VIEWPOINT OF LISTENERS. WIDESPREAD INDIGNATION. BY THERMION. Concern at the prospective return to Australia of Mr. J. M. Prentice is the sole topic of conversation among local listeners, "who are viewing with alarm and indignation tlio retrograde step of the Broadcasting Company in agreeing to the loss of the services of so able an expert. Mr. Prentice has the complete confidence of Auckland listeners. One cannot believe from the nature of local broadcasts that full advantage has been taken of his organising experience, but the items which he has personally conducted have called forth expressions of unstinted appreciation. In view of this and the fact that manv new licensees were obtained as a result of the appointment of Mr. Prentice, listeners have a right to demand, and no doubt will do so, most searching inquiry into the events leading up to the tendering of his resignation, its acceptance, and the remarkable action of not retaining his services until the expiration of the time of his notice. A large number of listeners communicated with the writer by telephone yesterday expressing concern at the present position and urging that a public meeting of protest be called. It should not be imagined that the executive committee ot the Auckland Listeners' League is idle, since it is already taking stops to arrange for a public meeting and to deal effectively with the action which has lost to them, the services of the one man whom thev "believed could raise the standard oi broadcasting in New Zealand. It is felt generally that the latest broadcasting impasse will be the culminating point in listeners demanding a complete revision and reorganisation of the present broadcasting system, which in two years of operation has antagonised rather tnan satisfied listeners. A RADIO PIONEER. During the sitting of the Australian Royal Commission on wireless the president of the Association for the Development for Wireless in Australia, Mr. G. A. Tavlor, urged that mor6 attention sTioiiicl be" given to encourage development of radio, particularly from the experimental point of view. He considered that Australia could obtain excellent results, as it had already led the world in certain sections of radio research, such as being the first in the world to institute radio transmissions to and from i-ailways in motion, the driving locomotives, the transmission of pictures in colours by radio, as well as winning earliest success in transmitting across the world messages on short waves with low power. Australian experimenters should get more freedom than they do at present. They should be permitted to transmit news of general importance, such as fire, police and weather reports, or other informations of immediate necessity, such as railway or other accidents. And although it is considered that giving such liberties to experimenters may be overdone, yet there should be u certain amount of trust placed in experimenters, who should hold some definite rank of qualification before receiving experimenters' licences. Mr. Taylor's remarks might apply also to New Zealand experimenters, who have been seeking recently increased scope for their activities. EMPIRE BROADCASTING. Regret was expressed last week by the writer that it was through a Dutch, and not a British, broadcasting station that it has been possible to hfear 2LO, London, and there has since been received a leading English radio journal which comments editorially on the position as follows: " For the second time in the short history of broadcasting it has been left to Holland to steal a march on this country and, in fact, on Europe generally. It will be remembered that some long while before broadcasting hero was introduced British amateurs were accustomed to listen to the Dutch broadcasting station at the Hague, which sent out regular Sunday afternoon concerts, mainly for the benefit of listeners- here. Now again Holland sets the example by leading the way in short-wave broadcasting. On March 15 the station PCJJ, in Holland, communicated by wireless telephony with the Dutch station at Bandoeng, in the Dutch East Indies The transmission was carried out on a wave-length of approximately 30 metftes. " Since that initial success fairly regular broadcasting has been conducted. Now comes the announcement that the Sydney station, 2BL, has successfully rebroadcast one of the programmes. We congratulate Holland, and the Philips Company in particular, on tlio enterprise shown in establishing this broadcasting record, more especially so as the purpose is apparently to provide a means for long-distance broadcasting, and advantage has been taken of the peculiar suitability of the 30-metro wave-length. "It will be interesting to observe whether this example set by Holland will be followed by other countries in Europe. ... It is a matter for regret that we should so far have neglected to take advantage of the wonderful opportunity which broadcasting provides for communication with the outlying sections of the Empire. When we know that wireless sets arc being bought in places as far distant as India and Irak, in the hope of being able to pick up the transmissions from Daventry once in a while for, perhaps, no more than a few minutes, we can form some idea of the enthusiasm which would be created if a short-wave British, station were established in this country of sufficient power to bo heard more or less consistently." Since the abov,e was written it has been stated that an experimental shortwave station is to be erected in England. NEW RADIO MARVELS. All the North American radio stations have been heard on a crystal set in the north of Ireland. This remarkable achievement was effected by using, instead of the usual type of aerial, a wire 2500 ft. long, which was raised by a portable box kite. A simple crystal set costing 7s 6d was used. In such an experiment care must be taken to earth the wire to an iron polo embedded in the ground, as strong atmospheric currents may occur in the wire.'

Then, too. researches are now being conducted into the location of water and precious ores by* wireless devices and airships. Scientists are working out ways and means for making rapid and complete surveys for unknown mineral sources. The surveys will be conducted from airships carrying special types of wireless apparatus now being developed for the purpose. Initial experiments have demonstrated the practicability of the idea—in fact, two different methods have been found : —so that tlie results of one will provide a check on the other. The use of radio in this direction may reveal and open up unknown water resources assuredly existing beneath great desert tracts which to-day are uninhabitable. In the pioneer development of new countries, the planning of new railways, and in other initial developments, instead of relying solely on surveys of the superficial resources of the land there will be the advantage of a preliminary knowledge of the subterranean wealth and possibilities. SHORT-WAVE RECEIVING SET. Due to the general interest in the specialised type of receiving set required for the reception of distant short-wave broadcasts there is published below an excellent circuit which will be found most effective. Some general requirAients of such a set were mentioned last week in Radio Topics, so that only brief details of the various components need now be given. The variable condenser, J, should have a maximum capacity not exceeding .00025 mfd., and its function is to tune the grid inductance. The amount of reaction is- controlled by the variable condenser, K, which may have a maximum capacity of .0003 to .0005 mfd. The usual grid condenser and leak are shown at M, L, and the grid-leak should be about 7 megohms. A variable rheostat, N, controls the filament current of the detector valve, while a fixed or variable resistance, R, may be used for the amplifying valve. An audio-frequency transformer, A.F.T., is shown as well as a switch, S.W., so situated as to break both battery circuits. To the terminals, T, may be attached a loud-speaker, headphones, or an additional valve amplifier. The radio-frequency choke, R.F.C., is an important component and may consist of 200 turns of wire on a former l£in. in diameter if short-waves only are to bo received. To make the choke compact, enamelled or silk-covered wire of No. 34 or finer gauge should be used, and the choke should be mounted so that the connection from it to the plate of . the detector valve is short, while at the same time the fields of the choke and the main coils do not interact. If plug-in coils are to be used so that higher wavelengths may be tuned too about 400 turns of wire or more will be required on the choke. THE TUNING COILS. The aerial inductance, P, should have about three turns of D.O.C. wire of, say, No. 18 gauge, and provision should be made for varying its coupling with the inductance, S, or, if wound on the same former as the secondary coil, S, the coupling should be kept loose. The former should be of the skeleton type for preference and the secondary inductance should have seven turns of No. 18 wire, the turns being wound so that there is a space between turns equal to the diameter of the wire. The tickler, T, will have three or four turns of, say, No. 26 D.C.C., depending upon the capacity ,of the condenser, K, and should be about 3-Bin. from the secondary, and wound in the same direction as the other coils. Rotating the dial of the condenser, K, so as to increase its capacity, will increase the regenerative effect. With these specifications the tuning-range will be from about 26 to 70 metres. With a little ingenuity the set may be designed with coils to ping into sockets so that other coils may be interchanged when it is desired to receive other wavelengths. For example, with P and S having respectively 20 and 80 turns of No. 24 D.W.S. wire and the tickler with 12 turns of No. 26 or 28 D.C.C., the tuning range would be from about 200 to 600 metres. On the ordinary broadcasting wave-lengths with the two-valve as shown it will be found possible to obtain good loud-speaker reception of the local station and the Australian stations may be heard well in headphones and on the ' loud speaker with the addition of an extra amplifying valve. NEWS FROM ALL QUARTERS. An excellent programme was broadcast from IYA on Tuesday evening. A certain amount of generator hum was noticeable. Conditions for the reception of overseas' broadcasting were excellent over the weekend and particularly praiseworthy was the relays on Saturday and Sunday evenings of special concerts at Wollongong by 2BL, Sydney. The Dutch broadcasting station, PCJJ, transmitting on 30.2 metres, may be heard etfery Wednesday and Friday morning from 4.30 to 7.30, New Zealand time, and proposes to relay frequently 2LO, London, on these mornings. Railway travel in Central Europe is losing its tedium. Several of the trains on tlio railway routes leading to Vienna have been equipped with wireless receiving apparatus. The aerial, which consists of a single wire about 50ft. long, is carried above the roof of the radio coach with a clearance of about Ift. The aerial is coupled to an eight-valve super-hetero-dyne, placed in a special compartment. The earth wire is attached to the metal frame of the coach. Each coach is specially wired and in each compartment there are distributing boards to which can be attached, if necessary, six pairs of headphones. A number of experienced travellers on the routes are said to make straight for the "radidwagen." Each listener has a numbered voucher and the cost of listening. is about 7d. The clarity of reception is said to be something of a surprise to those well acquainted with the troubles surrounding installations near electric generators. There was no difficulty in hearing the special test, transmission last Sunday from the American short-wave station. 2XAF. The writer heard the broadcasts clearly in _ the afternoon and evening on a receiving set similar to that described above.