Low Power Radio Transmitters for Broadcasting

This paper discusses the place of low powered installations in the existing radio broadcast system, and the importance of apparatus for such stations meeting the present-day requirements pertaining to frequency stability, modulation capability, fidelity, and radio-frequency harmonics. The characteristics and more interesting features of a new line of transmitters covering the range of output from 100 to 1000 watts are described. The basic unit is a 100-watt transmitter employing grid-bias modulation which is novel in so far as American broadcast practice is concerned. Outputs of 250, 500, and 1000 watts are obtained through the use of a supplementary amplifier unit equipped with tubes of appropriate capacity. Radiation-cooled tubes are used throughout, and both units are self-contained, being operated direct from an alternating-current supply without the use of rotating machinery. Mechanically the units are novel in that the housings are of a cabinet form with doors which allow complete access from the front for adjustment and maintenance.