BITS ABOUT BROADCASTS.

Manawatu Standard, Volume LVII, Issue 209, 4 August 1937, Page 3

BITS ABOUT BROADCASTS.

TELEVISION IN LONDON. (By “Microphone.”) “Television Ims become firmly established as a practicable means of telecommunication and already the provincial cities are looking forward to the time when they will 'share London’s privilege of having a broadcast television service. It is probable tliati eventually there will be a network of television cables interconnecting the studios and transmitters throughout the country, similar to the grid . of programme circuits which now exists for sound broadcasting; much, how-

ever, remains to he done before that stage is reached.”

This is the considered opinion of a London engineer with which ho concludes a very interesting survey of the television situation in England at the moment, a survey that is enlightening in its -revelation of the remarkable progress already established. In Loudon’s streets there are over 14 miles of | cable linking the more important build- | ings and {joints of interest w ith Broad- [ casting House, in Portland Place. From Alexandra Palace a section is ! laid to Broadcasting House and from there the route lies along Oxford Street, Marble Arch, Hyde Park (lor- ( ner, Piccadilly Circus, Shaftesbury - Avenue, Trafalgar Square to the Whitehall telephone exchange, there tlm ■ route forks, one cable going to West- : minster Abbey and the other via St. ! James’s Palace and Buckingham Palace | to Victoria. At intermediate) positions i plug points have been provided so that, j the camera may be brought into the j circuit. I Public interest in television was I stimulated last November by tho inj auguration of a regular high-quality I broadcast service from the Alexandra I Park station and was further whetted by the successful broadcasts of tno , Coronation procession. In February the | 8.8. C. adopted as standard tile Mar-coni-JC.M. 1. system of 405 lines with 50 frames p,v second. Television is analogous to telephony; in telephony the voice sou nils are converted hy tne microphone into equivalent alternating currents, which are transmitted to the loudspeaker, where they arc converted back to voice sounds. Similarly, the visual image is converted by the television camera into equivalent electric currents, which are carried to the receiver, where tho cathode ray tube converts them back to the visual image. In both cases the transmission between sender’and receiver may be over a metallic circuit, by radio, or a combination of the two methods. 11l tho first ease a co-axial cable is used; consisting of a solid wire within a tube formed concentrically around it. The 8.8. C. recently described at some length the mobile unit brought into operation tor the Coronation in conjunction with the tvibles. The inojvile jiart consists of three vehicles, each about the size of a single-deck bus. Between them they carry all the apparatus necessary to pick up and deal with tho outputs trom three cameras and the output from four microphones, which pick up the background,. announcements, etc., for the sound part of the television station. By liuvuis of special cables, the cameras may work at distances from the unit up to 1000 feet, the limiting radius of operations previously in the grounds of the station at Alexandra Palace. One of the three vehicles is connected to the cameras through the special cables, e.-ich of which is of the multiple type and contains 27 insulated and carefully screened leads, including a pair of low-capacity lines to carry the extremely high-frequency impulses from the camera. The conductors carry, among others, the power supplies to the cameras and to the “head amplifiers,” which are mounted alongside the cameras. The apparatus inside this first vehicle weighs in all eight and a-half tons, and is mounted in a dozen racks. The equipment also, enables the operating engineers to see the picture tha.t is being transmitted at tlie time and also to obtain a “pre-view” of a picture provided by a camera other than that which is actually in use, so that they may determine if it is suitable for' transmission. The amplified and controlled output from tho first yehicle is led to the special permanent cable if it is available. If not, the second vehicle is used. This contains a j complete ultra-short wave- transmitter of ope kilowatt output feeding a highly I directional aerial on tho roof of. the van. Its signals are picked up bv a I special , aerial placed above the ordin- ! ary transmitting aerials at the main j station. To avoid interference between the main signal and that used by tlie mobile unit, different wave-lengths are used, as well as special filter arrange-

mentis. The third vehicle of the unit is a self-contained power station, designed to supply all the power required l>y the other two and render them independent of outside sources. LONDON SCHEDULE CHANGED. Listeners will have noticed a change in., the schedules lor Transmission 1 from London, although so far the other transmissions have not been altered. The time has.been amended to the extent of half >.an hour so that the session for New Zealand commences at ■1.30, instead of 4 p.m., and continues till 6.45. The' following four waves are

G.SO and GSG appear to be giving the best service at present. The former signal is sent from Daventry in a south-westerly direction and the latter north-easterly. The other two transmissions are directed east and west from the station. It has been contended tlv't the signals heard here most successfully come via. the South Pole. THROUGH THE MICROPHONE. Early morning short-wave reception is excellent, more than compensating for tile seasonal defections in the evening. Europe is well to the fore with splendid signals. Among the most powerful stations is that of Czechoslovakia, OLU4A Prague, on 25.34 metres, 11.84 m.c.'s, which announces in several languages, including English, at 7.30 a.m. Hand and orchestral music is played at lull speaker strength. The power varies from 24 to 34 kilowatts, according to wave-length, and OLR would appear to be working at its maximum on this transmission.

Two 11 stations of long standing have been closed down for good. They are 4ZO Dunedin, which came on the air in October, 1928, and had transmitted for 10.465 hours- 2ZD Masterton, which had been in operation for 11 years. The only 13 stations remaining on the air so far without change ot control are stated to be 2ZM, 2ZO, 4ZAI and 4ZC. The Australian Cabinet has decided to retain as an historical record the radio equipment which enabled the first divided meeting ever to have been held by radio. Sliortly before Air Lyons, AJr Casey and Sir Archdale Parkhill left London, a meeting of the remaining members of Cabinet in Canberra was maintained in communication with them for more than half an hour by wireless telephone. One of the most entertaining Pacific transmitters is IvZRM Alanila on 31 metres; at 10.30 here it is 7 p.m. in' the Philippines, but for a couple of hours prior to that splendid volume is usually obtainable. The Spanish session commences at 10 p.m. While Tokio is being heard to advantage on tlie short-waves in the evening attention might be given to the broadcast hand stations. China is contributing its portion, also, and novel entertainment is assured from about 11 p.m. The following stations have been reported at good volume: JOAK-1, Tokio, 590 kilocycles, 150,000 watts, 12.30 a.m.; XGOA, Nanking. Kiang-su, 660 kilocycls, 75.000 watts. 2.10 a.m.; JODK-2 Seoul, Korea, 710 kilocycles, 10 000 watts, 12.30 a.m. ; XHHG, Shanghai, Kiang-su, 1020 kilocycles, 100 watts, 5.-30 a.m.; FEZ, Shanghai, Kiang-su, 1400 kilocycles, 250 watts, 1.30 a.m. Very severe interference on the broadcast and short-wave bauds from electrical sources continues to thoroughly spoil reception for long intervals in the Central suburb, militating against otherwise enjoyable programmes. The lower end of the broadcast band suffers especially, blotting out reception of the American and Australian police stations on 1500 kilocycles which are heard after dark.

i-till employed: GSG ... ... 16.86m., 17,790 k.c GSt) 19.76m., 15,180 k.c GS!) 25.63 m., 11,750 k.c GSB 31.55m., 9,510 k.c