TUBE 811

The 811 is a husky high-mu triode having a maximum plate-dissipation rating of 55 watts (ICAS). With a mu of 160, this tube requires no bias in class B modulator service up to a plate voltage of 1250 volts-and only -4.5 to -9 volts of bias up to 1500 volts. The remarkable ability of the 811 to "take it" is due in a large measure to its Zirconium-coated plate, an RCA development. This type of anode has very high heat-dissipating qualities and in addition functions to keep the tube hard during its entire life. Thus, the 811 is capable of withstanding heavy temporary overloads without damage to its filament emission, a feature which all amateurs appreciate. The tube has a rugged, 25-watt, thoriated-tungsten filament which insures tremendous reserve of emission. The features of zero-bias operation, 170 watts output on c.w., 120 watts output on 'phone, and 225 watts of audio in class B (2 tubes) make the 811 one of the finest values in transmitting triodes ever presented.