The 8891 or 4CX18000A is a 20000 watt tetrode for use in VHF-TV applications up to 400 MHz. These tubes were used in the RCA TT-30FH, F-line paralleled back up transmitters at KOVR channel 13 in Sacramento. The first example is a tube made by Brule, the second by RCA and the third by Eimac (4CX18000A). The last views are of the tubes in the transmitter and an 8891 being extracted.
Length = 7.10" Diameter = 8.29"
Max voltage = 10000
Max current = 6 amps
Fil voltage = 9.5
Fil current = 147 amps