Design considerations for an instantly operational (0.1 sec) cathode for UHF use

The critical parameters important to the design of an instantly operational cathode (0.1 sec heating time) for use in power tubes are discussed. Design information showing material selection, mechanical considerations, solution to lineal expansion problems, and methods of assisted heating are covered. The treatment of the cathode heating problem is presented in semi-normalized terms to make it more adaptable to a wide variety of tube applications. The work reported in this paper resulted in the design and construction of a low inductance instantly operational cathode (0.1 sec heating time) that could be interchangeably placed in a production 250-watt UHF tetrode. This design is shown.