Abstract: A frequency control circuit for a single sideband receiver is disclosed wherein the local oscillator is swept at a first rate to enable the acquisition of a transmitted signal. When the signal is acquired, the local oscillator is swept at a second rate in an indicated direction in order to center the signal. Upon centering, the local oscillator is maintained at a frequency which centers the signal in response to the activation of a squelch detector.

Abstract: An automatic frequency control circuit for a single side band receiver employing a split-loop phase locked loop system is disclosed. Initially, both a first and second voltage controlled oscillator lock to a received pilot taken after the IF strip of the SSB receiver. Once lock is achieved, a sample is taken of the control line voltage of the first VCO whereafter the first VCO control line is held at the sampled voltage and will no longer track the received pilot until such time as the second VCO deviates from a predetermined range. Simultaneous to switching the first VCO, the loop filter of the second VCO is adapted to maintain identical loop dynamics both before and after switching control of the first VCO.

Abstract: A single sideband communications system conveying a message through a transmitter to one or more predetermined receivers which are enabled by a coded squelch signal unique to the predetermined receivers is disclosed. The transmitter comprises means to angle modulate both the pilot signal and the information bearing single sideband signal with the coded signal at a predetermined deviation and to transmit the resulting signal.Each receiver frequency control means tracks the frequency excursions of a selected portion of the transmitted signal up to predetermined limits so that the message can be demodulated without frequency distortion being introduced. Each receiver demodulates the coded squelch without interfering with the message demodulation or tracking functions and activates the receiver squelch of those preselected receivers.