Maintaining frequency accuracy in single sideband repeaters

摘要

A system for maintaining an accurate frequency source in a single sideband repeater employs an ultra stable station control reference (SCR) frequency generator. A first frequency synthesizer for a local oscillator of the repeater phase locks to the output of the SCR normally, but is free running upon failure of the SCR. A second frequency synthesizer for another local oscillator phase locks to the output of the first synthesizer. Upon failure of the SCR, the system of synthesizers can provide a satisfactory frequency reference for the repeater. Disclosed are phase lock loop filter time constant design considerations for achieving proper operation.