Title: Filter stabilized single oscillator transceivers

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Abstract: A transceiver, adapted for use as either a master or a slave in a duplex pair, has a single, voltage-tunable, solid-state oscillator to provide the carrier frequency wave, a small portion of which is mixed with the received wave and applied therewith to a single ended mixer; an automatic gain-controlled loop cancels transmitter input modulation from the receiver output. The desired oscillator carrier frequency of the master transceiver is locked to a frequency within the pass band of an RF filter at the receiver input and separated from the center frequency of the filter by one-half the receiver IF frequency. The slave transceiver is first locked to a frequency within the pass band of the filter on the opposite side of its center frequency and separated therefrom by one-half the IF frequency (the slave thus offset from the master by their common IF frequency). Thereafter, upon sensing output from its IF amplifier (from the master), the slave is switched to operate in response to AFC developed by the received signal, such that the master and slave transceivers are locked together at frequencies differing by their common IF frequency. The RF filter also limits the signals to which the receiver can respond. An integrating amplifier provides demodulator and AFC filtering and, together with a bistable device, initial sweeping of the oscillator control voltage in respective directions depending on being in the master mode or the slave mode. Internal auxiliary modulation provides for pre-transmission transmitter modulation cancellation and frequency stability.


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