Abstract: A radio transmitter, or transceiver, provides for single side band transmission. A first carrier frequency source provides a first carrier frequency (term the deleted carrier) for balanced modulation by at least one balanced modulator. The resulting side band signal is ultimately applied to an add mixer along with a second carrier. The add mixer ultimately feeds a subtract mixer which also receives the deleted carrier frequency and subtracts same from the side band sum signal from the add mixer to provide the side band signal at the second carrier frequency, i.e., with the first carrier deleted. Alternative embodiments provide for single side band generation by use of a band pass filter following the balanced modulator or use of double balanced modulators with phase shift networks coupling the deleted carrier source and a source of modulating signals thereto. In a further embodiment, a phase lock loop synthesizer is employed for generating one of said carrier signals.

Abstract: In a transmitter or transceiver having alternately selectable transmission frequency channels, frequency selection switching is actuable for switching the transmitter from channel to channel and for stopping at the desired channel. A device, such as a microphone push-to-talk switch actuates the transmitter. Lock-out circuitry, interconnected with the transmitter actuating device and frequency selection switching, precludes simultaneous transmission and channel switching. In one embodiment, operating potential is removed from channel switching circuitry when the transmitter is in actuated condition and such channel switching circuitry is supplied operating potential only with the transmitter in its nonactuated condition. In further embodiments, frequency selection switching is disabled or blocked when the transmitter is actuated and only becomes enabled when the transmitter is deactuated.