The Developmental Problems and Operating Characteristics of Two New Ultra-High-Frequency Triodes

Large values of power are difficult to obtain in the ultra-high-frequency region. At the limiting frequencies it is increasingly more difficult to find vacuum tubes that will deliver such power and perform efficiently. The principal factors that affect the design and performance of the tubes are those involving the electrical circuit, the size requirements for the power desired, and the transit time of the electrons within the evacuated space of the tube. The design principles that result from a consideration of these factors have been used in the development of two new ultra-high-frequency triodes. A triode capable of delivering approximately 700 watts at 100 megacycles is described. This tube, which is cooled by water and air, is capable of operation as a neutralized power amplifier up to 200 megacycles with an output of approximately 500 watts. A second triode is described which is a radiation-cooled glass tube with a 300-watt plate-dissipation rating. Normal efficiency is obtained up to 40 megacycles and operation as a neutralized power amplifier is possible up to 100 megacycles. The efficiency at 100 megacycles is approximately 60 per cent.