RADIO TOPICS.

New Zealand Herald, Volume LXI, Issue 18827, 30 September 1924, Page 5

RADIO TOPICS.

*" BY THEEMION. HIGH-POWER BROADCASTING. A 1600-metre station, SXX, has '] been set np by the British Broadcasting Company at Chelmsford, in order to permit crystal reception over a s wide area, ■to allow of relaying : between existing stations by means of wireless instead of post office lines and thus avoid a good deal of distortion, and also to provide listeners-in in coastal areas where ship jamming is experienced, with a broadcast transmission free from interference. This station will be the highest-powered broadcasting equipment in the world and, provided means are found of efficiently modulating the large amount of _ energy involved,, it should bo possible to hear SXX m New Zealand. The preliminary tests havo been unsatisfactory and, with high powers, only short ranges have been covered.

The idea of setting up a central broadcoasting station of such high powers presents many new problems, and one stage in the advancement lias been the use, for the first time in England, of watercooled valves. Four of these are in the master oscillator circuit, and they pass a total current of 1700 milliamperes at a potential of 9000 volts, representing an input power of over 15 kilowatts, and an aerial current as high as 40 amperes is obtained. The circuit has a master oscillator consisting of two valves connected in parallel, and this is used to set up oscillations of the required wavelength. Theso oscillations are then amplified by two water-cooled valves. Modulation is carried out by the well-known choke control arrangement. ' After the experimental stage has been reached it is doubtful whether the station will bo allowed to continue in operation, as the post office officials have stated that the station must not produce interference on the lower wave-lengths.