A squelch system controlled by signal-to-noise ratio
W.G. Klehfoth · IRE Transactions on Vehicular Communications · 1955
Since the quality of communications is a function of signal to noise ratio, it follows that a squelch system will perform its intended function more proficiently if it operates directly as a function of this ratio. The threshold of operation of the commonly used carrier-operated system varies widely with changes in ambient noise conditions and receiver gain. This squelch system overcomes these objections to the carrier-operated squelch and may also prove useful for suppressed carrier systems. Formulas applicable to circuit operation and practical circuitry which will provide consistent operation for signal plus noise to noise ratios as low as 2 db are given. Results of field tests are also included.