Vh

Voltage applied to heater.

Ah

Current rating of heater measured in Amps

Va

Voltage applied to anode. Referenced to cathode regarded as at 0V

Vs

Voltage applied to screen grid. With respect to cathode

Vg

Voltage applied to control grid. With respect to cathode

Vosc

Voltage applied to second control grid in frequency changers

mAa

Current rating of anode circuit measured in milliamps. 1000mA = 1A

mAs

Current rating of screen grid

mAg

Current rating of control grid. This is normally very low.

ra

Anode AC resistance

gm

Mutual conductance. The change of mA of anode current that flows for a 1 volt alteration in g1 volts

rk

Cathode bias resistor

rl

Optimum output load resistance

Pdriv

The input power in Watts required to drive the valve to maximum output

Pout

The number of Watts of output power

Pdiss

The power in Watts that the anode can dissipate

D

Percentage distortion of amplified signal. Audio output valves

freq

The highest frequency in MHz that can be used at maximum output

f.max

The highest frequency in MHz at which that the valve will produce useful power