ON ALL WAVELENGTHS

Evening Star, Issue 20310, 19 October 1929, Page 8

ON ALL WAVELENGTHS

By

BROADCASTING POLICY. Some weeks- ago a deputation from the Auckland Listeners’ League waited on the Postmaster-General (the Hon. J. B. Donald) and submitted to him a number of matters connected with broadcasting. The Minister promised a reply in writing, which has now been received by the league (states an exchange). Regarding the Broadcasting Company’s expenditure on programmes at the Auckland station, which the league suggested was less than at one southern station with fewer listeners in its district, the Minister says: “There is no departmental record of a statement that the income derived from license fees paid by listeners in the Auckland district would be allocated solely for expenditure at the Auckland broadcasting station. A strict adherence to tins principle would not be in the best interests of broadcasting. .It is reasonable that the company bo permitted to exercise a certain amount of discretion as to the allocation of funds, in order that the best results may bo achieved. At the same time, I desire to assure tho league that my department is closely watching the position, and that the interests' of Auckland listeners are being properly safeguarded.” A request by tho league that a local advisory committee bo set up docs not commend itself to the Minister, who states that tho present sectional committees —musical, religious, _ and children’s—are preferable to a single body. Ho declines to intervene in tho controversy over tho Auckland Municipal Baud, which," he says, is a matter between the company and the Auckland City Council. Mr Donald says ho _ cannot see his way to approve advertising by private broadcasting stations. The multiplication of such stations, which in most cases would be rim merely for publicity and monetary gain, would, cause mutual interference and give trouble to listeners not possessing highly selective sets. “ In conclusion,” states tho letter, “ I desire to say that 1 am keenly alive to tho importance of tho radio broadcasting service, and will lose no opportunity of securing its development, to tho highest degree of efficiency. 1 am quite satisfied, however, that the Broadcasting Company is nob endeavouring to avoid its responsibility in the matter, but is making a genuine effort to provide an efficient and satisfactory service for listeners as rapidly- as circumstances permit. “ With reference to tho formation of an advisory board, 1 purpose going into the matter with Mr M‘Namara on his return from abroad. Tho question of publication of the Broadcasting Company’s balance-sheet- and tho terms ot the agreement entered into with the company in respect of tho broadcasting service is being considered.” NATIONAL RADIO EXHIBITION. This year’s National Radio Exhibi tion was held at the Now Hall, Olym pia, London, from September 23 to Oc tober 3. Tho positions of applicants for space were, as in former years, made by ballots, one being for members of tbo R.M.A. and another for non-member applicants. All exhibits were of British manufacture. Tho conditions of the exhibition were the same as in previous years, except that special arrangements had been made whereby loud speakers, whether independent units or incorporated in receivers, could be demonstrated at certain times of each day of the show Tito use of accumulators or batteries for lighting and power was not allowed, and tho organisers arranged to carryout all wiring requirements of exhibitors both as regards loud speaker demonstrations and stand lighting. Tile layout of the ground floor ot tho exhibition was the same as last year. The gallery was devoted to ox hibitors’ stands to tho exclusion of the dancc floor and tho large space occupied in previous years by the 8.8. C Some of the additional space tlingained accommodated twenty-five specially constructed cabinets or rooms, where loud speaker demonstrations were conducted from tho common input or from gramophone records.

NOTES AND COMMENTS /

THE VALUE OF TESTING. Tho construction of a new set is finished, the components have been mounted, the wiring completed, and all connections made, but after hours of, toil, fascinating in itself, and delightful in anticipation of the wonderful results the new receiver will give, tho condenser dials arc turned from one end of the scale to the other, several times, but without result. Probably there are few enthusiastic constructors Who have not, at some time or other, groaned under this mortifying condition of affairs. What could bo more disappointing, or better calculated to arouse the latent evil passions of frail human nature ? First mount up all your components, and then wire up only tho detcctovvalvo circuit. Make a temporary- connection from the tuned-anode coil (at tho end of the coil which will later bo attached to the neutralising condenser) to L.T.—-and earth; flex and clip connections are all that need be used here. Make another temporaryconnection of the aerial to the centretapping plug which goes to the anode coil.

One telephone lead is joined to the low-potential terminal of the H.F. choke, and the other to H.T.-fl. Join up the L.T. accumulator and H.T,—, and all is ready for an effective test of your detector valve. If anything is wrong here, yon have quite a simple circuit to check over; and as soon as you are satisfied that it is working*efficiently, you can go ahead with the wiring of the next circuit. The H.F. circuit is the best one to tackle next. After tho wiring is completed, the first two valves are easilytested by reconnecting the batteries and phones, and by joining up aerial and earth, this time to their proper terminals. Again, if anything is wrong, you know the detector circuit is all in order, and the trouble is localised in the H.F. end. The ILF. valve may also be neutralised conveniently- at this stage of tho work. Then your L.F. valve can be wired up, the phones discarded, 1 and the whole set tested on the loud speaker. Any* failure. of tho sot to operate properly- again involves tbo testing of only a few simple connections or components. It should be pointed out that there is no need to adhere quite rigidly to the wiring of each valve separately; for instance, it is often more convenient to complete the whole of the_ filament wiring in “one go.” Tills is not inconsistent with the general idea of the scheme. It means that after wiving tho complete filament connections, the grid and plate connections of the detector valve will bo finished off, and this valve tested, before tackling other grid and plate connections With H.F. coupling by means of tuned transformer the plan is, of course, still easier to put into effect, because one end of the transformer secondary, which has to be at earth potential, can bo permanently connected, and the only temporary connection required is the aerial to the secondary winding.

The only limitation occurs when re-sistance-capacity coupling is used on the L.F. side (on the H.F. side it is hardly ever used). If the valve, which is R.C. coupled, has a separate H.T. tapping, phones can be connected in place of the anode resistance and the H.T. reduced to a suitable value for testing purposes; otherwise, it is advisiblo to omit a. separate test of the R.C. coupled valve. AERIAL TELEVISION. Something now in the development of television, an apparatus designed to transmit aeroplane views of panoramic scenes to a ground receiving station, is under construction at Washington. The “ aerial television eye,” will record the visual scenes by means of a scanning disc, light-sensitive cell, and broadcasting apparatus, and will bo received on regular television machines, It is believed that the invention would bo of great value in time of war. General headquarters of an army would be put within range of actual operations at the front. STRAY SPARKS. Another excellent programme came from 4ZM last Tuesday evening, according to many reports received. On this occasion tiio Mosgiel Woollen Mill Choir, assisted by two or three local artists, contributed a programme that in many ways was superior to some wo have heard from other stations. Many wireless set users have a vacuum cleaner in the house, and while one does not usually think of running the vacuum cleaner over the wireless set, it should not bo forgotten that practically all of these useful domestic instruments have a “blower” attachment by which a strong jet of air can be projected through a nozzle at the cud of the tube. This jet of air is of great use in removing dust from a set, and particularly for cleaning the spaces between the vanes of variable condensers. * * » » A paper declares that New Zealand is missing a lino opportunity for cheap national advertising, and suggests that the Government should erect a powerful short-wavo broadcasting transmitter, through which information about New Zealand could be spread all over tho world. Such a station, it is thought, would do more than anything else to put New Zealand “ on the map.” The matter may be worth considering. CORRESPONDENCE. “ M.J.” (Dunedin) writes inquiring as to tho keeping of tho B battery in order, and how to go about emptying tho battery and renewing the acid. Tho correspondent also asks how long an A battery will last. If thb B battery has sediment on tho bottom of the jars and really needs cleaning, tho safest way to have it done is by taking it to a service station. Always keep tho level of tho acid just above tho plates, but do not add new acid unless any is spilled. Only distilled water should be added, and this is procurable at any of the service stations, Distilled water will keep for any length of time. It cannot be said what the. life of au A battery will be unless it is known what types and number of tubes it is working. • WIRELESS MAGAZINE.’

Last month’s edition of ‘ Wireless Magazine ’ covers 190 pages with useful and instructive information for the radio man. An interesting article by Dr Alfred Grademvitz deals with the teaching of music by radio, while the construction of a three-tube receiver is fully explained, there being diagrams that, are easily followed by the amateur. In tho gramo-radio section of the magazine more is said about tho reproduction of bass notes and other matters in connection with tho radiogramophono combination are touched on. Obtaining tho grid bias from the electric mains is another phase of radio forming a subject for W. James on winch to write. Other features are included in tho magazine, a copy of which lias been received from Driver’s bookshop.