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Cost effectiveness of high-power UHF-TV transmitters was and is directly linked to the selection by both broadcasters and equipment manufacturers of the main components for the high-power stages of these transmitters. While solid state is making significant inroads at low power, the most adequate component above 1 kW in UHF remains the electron tube. In the 1- to 25-kW range, the cost of energy as a part of the overall running cost of a UHF-TV transmitter, as well as the need for more reliable components used in lesser numbers, has led to the development of a new generation of power-grid tubes with high gain; high efficiency; long lifetime; and optimal design of their associated circuits and cavities. This progress was made possible through the application of new technology in the design of the power-grid tube inner components by using pyrolitic graphite grids and by increasing the tube dissipation capabilities with the liquid vapor phase cooling techniques. The prospect for newer grid tubes in the 25- to 50-kW (with one single tube) power range in UHF becomes a clear possibility in the near future. The energy cost analysis given in this paper shows that the power-grid tube gives a higher efficiency and is therefore the best candidate for present and future high-power UHF-TV transmitters.
Date of Publication: Nov. 1982