Prototype constant-efficiency amplifiers

This paper describes two constant efficiency amplifiers (CEA) using cathodes, novel grids and novel cavities similar to those used in our inductive output tubes together with five-electrode, multi-stage, depressed collectors in either poly alpha olefin (PAO) oil-cooled or forced-air-cooled versions. The air-cooled version is capable of 65 kW peak 8VSB or COFDM operation, and the oil-cooled tube will provide the performance of our higher power IOTs in either 8VSB, COFDM or NTSC service with much higher average efficiency. The PAO oil (similar to synthetic automobile engine oil) is a low-cost coolant that simultaneously solves insulation and corrosion problems. These tubes meet the expectations that were discussed in our previous papers. The design and performance are described together with application data useful to transmitter designers. Collectors may be connected together to minimize the number of independent voltages required or operated independently to maximize efficiency and minimize power supply size for a wide variety of signal statistics. A single thyratron crowbar circuit which will simultaneously short circuit up to five voltage sources is described. The CEA design and its application are covered by US and foreign patents issued and pending. Adoption of this technology will save television broadcasters in the order of one billion dollars of electrical power cost over the life of these patents.