Abstract: The present invention concerns circuitry for comparing the output power of an amplitude modulated RF transmitter with the supply power to the RF transmitter and using feedback from a comparator to a variable gain modulation amplifier to maintain the level of modulation constant. The scheme is illustrated for four different basic types of RF amplitude modulated transmitters.

Abstract: Apparatus for and the method of simplifying and economizing upon transmitter power amplifier output stage circuitry is illustrated. By grounding the anode of the RF power amplifier, the FCC required plate voltage meter and plate current meters can be connected to near ground potentials and the requirements for a high voltage coupling capacitor between the anode and the antenna is eliminated. Although the specific embodiment illustrated uses a pulse-width modulated cathode modulation scheme, any type of cathode modulation will perform in accordance with the concepts of this invention.

Abstract: When a pulse-width series modulator is connected to the cathode of an RF radio transmitter tube for the purpose of series modulation, filtration of the PWM switching signal is required to eliminate the switching signal from the output modulating signal. Stray capacitive effects in this filtration generate undesirable distortion in the trailing edge of the signal appearing in the last stage of the PWM thereby producing non-linearity in the modulation of the RF output tube. The present disclosure illustrates circuitry for complimentarily modifying the leading edge of the pulses so as to maintain a linear relationship in the time integral of voltage in the output signal. This modification is accomplished through a plurality of capacitive units each having different time constants for charging and discharging.