Communication transmitting apparatus with carrier level control

摘要

Low level amplitude modulated radio transmitting apparatus employing a DC control loop from the output amplifier to the audio modulating stage for maintaining the carrier output level constant. The audio signal to be transmitted is superimposed on the DC control signal and the resulting signal is applied to an operational amplifier that controls a current driver supplying operating potential to the modulating stage. A DC limiter at the input to the operational amplifier limits the DC control signal to the operational amplifier thus preventing continuous overdriving of the RF elements in the event of a disruption in the DC control loop. An audio by-pass permits the audio signal to by-pass the DC limiter and be summed with the limited DC control signal at the input to the operational amplifier.