Frequency control for radio relay station - avoids unwanted frequencies using phase discriminator to compare mixer with crystal and tune free-running oscillator

摘要

The frequency control has the receiver's free running oscillator (G) connected via a mixer (M3) and a coupler (K) to the line leading to the transmitter's oscillator (B). The mixer produces a signal whose frequency is the difference between the receive frequency (fE) and the transmit frequency (fS) and passes this difference to a phase or frequency discriminator. The discriminator produces a control signal when the difference deviates from a second signal supplied by a crystal oscillator (Q). The control signal is passed to the receiver's oscillator to adjust its frequency. The receive and transmit paths are decoupled by directional lines (J). The coupler is directional.