Radio Review

Evening Star, Issue 19894, 16 June 1928, Page 17

Radio Review

[By “HENRY.”]

Flashes from Everywhere.

THE SERVICE FROM 4YA. evcral correspondents to the ‘ EvcnStar ’ this week have deplored the tact that our station, 4YA, did nothing frr us so far as the Pacific flyers were concerned. The correspondents were justified in speaking their minds, for it is 4YA that is kept on the air by the license holders. We pay thirty shillings a year for our broadcasting fare and receive; about twenty-one hours’ transmission a week in return, nothing more, nothing less. The question then arises: Do we get our thirty shillings’ worth? That will always bo a debatable point, for, while many may say that we don’t, there is always the person who is of the opinion that we do. However, the fact remains that we got nothing from 4YA about the flight ? but had to turn to an amateur station, 4ZM. As 1 write these lines 1 have before me a copy of Tuesday’s ‘ Star,’ in which is a letter from Mr W. L. Shiel, who states that he actually offered 4YA the chance to rcbroadcast the landing of the Southern Cross at Brisbane. The offer was turned down. It may have been that the offer was too lato in forthcoming, as I have heard, that anything done of that nature at 4YA has first to be referred to the head office. If I am wrong in that statement I am open to correction. Mow, Mr J. D. M'Eweu. wlio operates 4ZM, does not receive anything from the license fees paid—he runs the station with his own money, and must therefore suffer a loss every time he goes on the air. Nevertheless, he was prepared to run for hours in order to give listeners a rebroadeast of the landing of the Southern Cross last Saturday morning. Working in conjunction with Radio Service, Ltd., all listeners in Dunedin and its surrounding districts, whether working witli a valve sot or the hnmblo crystal, were given the opportunity of listening to the description of the landing of the airship. Not only did we get, the landing, but during the intervals a number of short wave stations were tuned in and rebroadcast. Then on Sunday 4ZM again took the air for the chief purpose of giving a rcbroadcast of the short wave Sydney station, 2ME, which was to give a description of the landing of the aviators at Sydney. For over four hours on Sunday afternoon Mr M‘Ewon tried his best to robroadcast Sydney, and, although he was not successful, thanks are duo to him for his work. Meanwhile 4YA plods along, starting and stopping at regular hours, with the same classes of programmes week in and week out. In the ‘ Radio Listeners’ Guide,’ recently published, there is a little paragraph in the middle of the column, and it should interest local listeners. It says: “On October 1, .1927, tho old 4YA, having been remodelled and made up-to-date, was brought into operation pending the erection of a new station in Stuart street, Dunedin, to he completed and officially opened during 1928.” Now that wo arc to have a new 4YA, it is to he hoped that the company will take a little interest in it and make it a worth while station. If this was done I should not be in the least surprised to sec tho licenses in Otago mounting up in dozens. , LOCATION WANTED. Most of the Dunedin people who puck up 2XAF notice that the station has a very bad habit of “ swinging,” and certain people; in this town arc anxious to know ..if there .is any. locality where the short-wave station does not “ swing.” If there is anyone who knows of such a locality, would they please communicate with tho writer. Such information, it is hoped, will benefit all listeners in a few' week’s time. TELEVISION. The progress that tho radio engineers of the world aro making towards_ the development of a television transmitter which will' really televise, is remarkable. Within the last few weeks a Melbourne audience was treated to a demonstration of telephotography and a lecture on television by Donald MacDonald, M.IJR.E. (says the ‘Home Beautiful’).’ Already much has been done to transmit moving pictures -by radio. John Baird, the British inven■.or, has succeeded in bridging the Atlantic. Of course, telephotograpliy, vhich is the transmission of “still” hetures by wire and radio, is a much iirnplcr matter, and is at j present in practical use in both America and the Continent. The Radio Corporation of America operates a radio picture service -.'between London and New York, and a land lino service between the Eastern and Western States of the United States of America.

vision is so long in coming, but that so much has been done in such a short tune. Of course it is understood that the first television transmitters marketed will be comparatively crude. Such ivas the case with the first- radio receiver, it is necessary only to go back five years to realise the improvements which have been made in broadcast receiving apparatus. With the popularising of broadcasting came tho improvements which have made the receiving set of to-day tire high-class instrument it is. Such will inevitably bo the with the television receiver, ana rithin loss than five years it is safe to predict that from being a miracle at which we marvel, it will become a commonplace, at which we grumble. BROADCASTING MERGER.

' A further stage in the co-ordination of broadcasting services in Australia was reached last month when the Broadcasting Company of Australia Proprietary, Ltd. GILO), announced that arrangements had been made whereby that company obtained tho controlling interest in the Adelaide station (SCL). It has taken some time lor the companies concerned to come to an amicable agreement as requested by the Postmaster-General some time ago. The effect of the co-ordination of tho services of the two stations will bo that it will be possible for artists to be engaged for a longer period than was the case formerly when tho companies were under different management. The full benefit of the co-ordination will not be experienced immediately as sometime is necessary _ before the coordinated services aro in full, working order.

• Within four days of TLO’s representative assuming control of the SCL studio, fire broke out and completely destroyed the studio and office. The outbreak occurred at 11. TO p.ra., and ai 7.45 a.m. tho next day a gramophone had been installed at tho station, ami a programme was put on the air instead of tho ordinary break fasthour session.

When word was received in Melbourne of the (ire arrangements wore made with (he Postniastcr-Genoral’s Department for the use of a telephone line until such times as the studio was rcbnlit. A temporary service was then arranged for SCL, which broadcast 31.0’s studio concerts.

RADIO COMPLAINTS. Some little time is likely to elapse before a basis for the improvement is agreed upon. Negotiations arc being carried on between tho PostmasterGenera I’s department and the “ A ” class .stations of Sydney and Melbourne on tho subject, but it is reasonable to assume that the existing arrangements of the 2EG aud 31.0 stations cannot be modified without tho fullest consideration being given to tho relative merits of the items broadcasted (says a Melbourne paper). Mr Condor, managing director of 3LO, it is understood, has indicated to the department that tho quality of the musical items and the putting on tho air of sporting fixtures, birthday greetings, and other items alter 7 p.m. could bo curtailed or eliminated if the public showed its dissatisfaction in any tangible degree. The department’s pica that all should bo conducted in accordance with the regulations has also been a subject of negotiation. What the Postmaster-General's Department must particularly insist upon now “A” stations have been amalgamated is that advantage should bo taken of tho opportunity presented for alternative radio programmes, if tho listener desires to switch from one station to another. The Director of Postal Services (Mr Haldane) was not prepared to state how far the negotiations with the broadcasting companies had proceeded in the matter, but lie declared definitely tho attitude of the department in saying that the two “A ” class salions "in Melbourne received IT20,1)00 a year of the listeners’ licenses, and the latter were entitled to something good for that. A suggestion by 3UZ that the “A ” stations "take a popular plebiscite in regard to their programmes has been brought under tho notice of the department. “Wo would have no objection to taking a plebiscite if they ask ns.” commented Mr Haldane. “ Better still, we would be prepared to accept a joint counting of votes in favour of particular programmes if conducted by the companies themselves.”

RADIO ON AEROPLANES. There appeared in an American publication of some months hack a description of the radio apparatus used on the Dallas Spirit in the tragic search for the two lost ’pianos in their flight to Honolulu. A wind-driven generator furnished the power for the filament and plate circuits of the transmitter installed in the cockpit of the ’plane. The circuit was of the tuucd-grkl-plate typo. The transmitter was of the fixed tuning type, adjusted to .Til metres, and the Lining control which was tho grid tuning condenser, was adjusted permanently. The aerial system consisted of the frame of the ’plane ns a counterpoise, and a 2Sft wire weighted down by a lead fish on _ the end, for the antennal. Snare aerials wore carried in case the original one was carried away.

Some of the greatest minds the electrical 1 world has known are at work on the problem of television, and the success which has already attended their efforts augurs well for the future. The marvel is not that tele-

The generator had two armatures, one for 10 volts (240 cycles) to light tho filament of the tube and furnish power for the lights on Jibe instrument board, and one for 65 volts (240 cycles) to supply the plate power. Tho generator was driven by an 18in propeller, and was mounted on tho forward edge of the luselago in the slip stream, so that at the normal speed of the ’plane (about 100 miles an hour) the frequency of the generator would be 240 cycles. _ . ! Keying was accomplished in the primary of the power transformer, two kevs being used; one in the forward cockpit for the driver and tho other in the rear compartment whore the navigator had his charts. The entire transmitter and generator weighed but 001 b. While the ’plane was out searching .for the lost aviators it was in continual comniunication with land._ The Dallas Spirit had been in the air six hours when the tail spins came. The whine of , the' generator rose to above 600 •; cycles." indicating that the .’plane;, was." travelling, at over 200'miles an hour.' 1 .Throughout both tail spins the generator functioned perfectly, the voltage regulators preventing the filament of the tuho\from being burnt out. Tho transmitted wave remained as steady as a rock. Tho fact that Eichwaldt (the operator) remained at the key sending out tho dots and dashes of his last message while tho ’plane was hurtling down at a sickening speed is an everlasting tribute to his courage and presence of mind, even ip tho faco of certain death. Those whoh listened on shore heard the howl and a 1

" Henry " will t>a pleased to answer any questions through this column relating to the fascinating hobby. Each emreepondent must sign bis bubs and address (not necessarily for publication). Newsy items will be welcomed.

amplifying the electro MAGNETIC PICK-UP.

screech of tho note ns KGGA (tho ’piano’s call sign) was no more after a life of a little over sis hours. The above notes on tho transmitter used on the Dallas Spirit should bo interesting to listeners at present^as they also apply to the transmitter lilted to tho Southern Cross.

Double impedance choke coupled amplification is recommended for the amplification of tho impulses generated in the electromagnetic pick-up, but quite good results aro obtaining with the throe stage resistance amplifier blocks now used in ' many receivers. Usnallv the pick-up does not require a booster battery, and the impulses can be impressed upon the grid of the first amplifier by connecting the lends from the pick-up in place of tho grid resistance situated second from the end. The volume control resistance is then connected across tho leads from tho pickup.

POWER SUPPLY SYSTEMS. Oiio of ilie biggest problems in the operation of receiving apparatus is the supply of suitable power for both the A and 15 circuits of the set in an easy and economical manner. The solution of this problem has not been made any easier by the great range, both in the size and typo of the various sets and accessories available (write N. M. Goddard, in the 'Sydney Morning Herald ’). In the average set operating with valves, which require a direct current for filament heating purposes, the filament battery voltage may vary from ono volt to 0.5 volts, and the current from .06 amp. to .5 amp. per valve. Those valves will need anything from twenty volt.s to 180 volts on the plate, and when used as amplifiers will require a grid bias of from 1-J- to 22£ volts, and the plate current may bo milliamps in the case of a detector to about 15 milliamps in the case of a power valve. Again, those valves may be used together in any number from ono up to nine, so that the maker of power supply devices has not a very easy task when bo tries to turn out something which will suit every requirement. For tho purpose of lighting filaments tbo power supplied must bo unfluctuating direct current, or a direct current which only fluctuates n very small amount. This requirement is necessitated by the fact; that as tbo temperature, of tbo filament varies the characteristics of tho valve also vary, and tl lis may ho demonstrated very easily by turning down tho rheostats. For this reason alternating current cannot ho successfully used with ordinary valves, although of late years it has come into use with a special typo of valve having a thick filament through which heavy currents at a low voltage pass. In this case tho filament acts as a reservoir of heat by reason of its relatively great size, and so the current fluctuations are rendered less noticeable, and in the “heater” typo of a.c. valve tho filament is used indirectly to heat np another element which is tho roai source of electrons.

Alternating current or heavily fluctuating direct current will not only set up an audible note, but it may in certain cases produce a modulation of the speech or music winch is really a variation in the intensity of the signal at tho frequency of the fluctuating current. The effect is as if someone were continually applying a soft and loud pedal, and is very objectionable. Tho power used for B supply must be smooth direct current. Alternating current is out of the question, because a positive potential must at all times bo applied to the plate. Even the smallest fluctuation or variation other than that caused by the station makes itself known in tho speaker, and causes a hum. 'fho B supply must be smoother than the A supply, because there is no moans of storing heat energy as in tho filaments.

0 supply is only a question of voltage or pressure, as there is no current in the grid circuit. No energy is, therefore, supplied, but the pressure of the 0 supply must always bo constant, as any variation in pressure applied to the grid of a valve shows up many times as much in the plates circuit of the same valve. Alternating pressure is therefore excluded, and C supply pressure must have only a very infinitesimal amount of fluctuation.

At tho present time there arc many sources of A supply available, the commonest being primary batteries, _ secondary or storage batteries, A.C. lighting mains, D.C. lighting mains, motor generators, and rectifiers. The primary battery is most familiar to everyone in its “ dry ” form, and does good work in supplying power for filament purposes. The secondary battery or accumulator is probably the most widely used of all the methods, and provides a beautifully quiet ami steady flow of cun-cut. The action in this case is a chemical one, but it is reversible in t hat when it has been completed a current in the opposite direction will restore tho battery to its original chemical state. A.C. lighting mains are not used for filament purposes, except with the special typo of valve, without the intervention of some rectifying and smoothing device. Direct current mains also arc not used very widely, for the reason that although the current is unidirectional and is not by any moans unfluctuating, there is always a “ripple” in it, and tho removal of this “ ripple ” involves the use of an expensive filter system. Rectifiers are widely used not only for supplying current direct to the filaments, hub also for supplying unidirectional current for charging secondary batteries. There are many types, of these, tho commonest being tho valve rectifier and tho electrolytic rectifier. The valve rectifiers are of two types—viz., those with filaments and those without. Rectifiers do not produce an unfluctuating current, so that additional apparatus in the form of chokes and condensers is necessary if a steady output is desired. All tho power systems used for A supply are also available for B purpose, except the unrectified current from the A.C. lighting mains, hut dry and storage batteries are the only sources of unfluctuating direct current, and are most extensively employed. Of nil the other means of supply, rectifiers combined with fillers are most used owing to the widespread use of alternating power supply systems.

Quite, a number of crystal Users at the south end of the town are complaining bitterly of a station that takes the air on Sunday nights while 4YA is broadcasting. The programme from 4VA was completely spoiled last Sunday by the row. made by the offending one. stated one listener "'this week. “1 mpo lie will be quiet this Sunday.” ho iddcd.