Heterodyne frequency meter
For tuning and servicing transceiver devices, for measuring the carrier frequencies of modulated signals, heterodyne frequency meters are useful. The frequency of the investigated signal is compared with the frequency of the signal of the local oscillator (auxiliary tunable generator) before reaching zero beats.
Zero beats indicate the coincidence of the frequency of the investigated signal with the frequency of the local oscillator. An example of a heterodyne frequency meter checked by time is a tube Volometer -14-1, used for calibration of transmitters and receivers operating with continuous oscillations. The working range of the device is from 125 kHz to 20 MHz.