New 120-kW thermonic valve

There has been a rapid increase in the power of broadcast transmitters during the past few years and there exist stations which radiate 120 kW carrier power and in which the peak power in the aerial may reach even 480 kW. In the last radio-frequency stage of such transmitters it is customary to employ say 12 valves of 40-kW each in parallel, and it has been found that unless extreme precautions are taken many troubles arise. These are discussed by the authors, and details are given of a new 120-kW valve which overcomes such difficulties. In the course of the investigation information was collected which appears to indicate the possibility of constructing a 250-kW valve based on the same principles. The small dimensions of these tubes and their ability to withstand appreciable overload make them suitable for even the largest transmitters.