The 4W20000A or 8173 is a 20,000 watt, water cooled, tetrode with full power to 250 MHz. First announced in 1951 by Eimac, there have been several shape changes. The original was all glass and had a narrow plate insulator and a long filament extension (17" overall length). The version of 1953 was refered to as a radial-beam tube, had a ceramic plate insulator and a shorter filament extension . About 1961 the ceramic plate insulator was widened, the shape of the water cooler was changed and the length of the water lines was shortened as is shown in this example. This tube was designed for cavity circuits in TV visual transmitters.
Length = 15.20" Diameter = 5.00"
Max voltage = 8000
Max current = 15 amps
Fil voltage = 10
Fil current = 30 amps