ABSTRACT
Any number of configurations may be used to generate radio frequency (RF) signals using vacuum tubes. Circuit design is dictated primarily by the operating frequency, output power, type of modulation, duty cycle, and available power supply. Tube circuits can be divided generally by their operating class and type of modulation employed. The angle of plate current flow determines the class of operation:
Class A = 360° conduction angle
Class B = 180° conduction angle
Class C = conduction angle less than 180°
Class AB = conduction angle between 180° and 360°
