Analysis of interference caused by interfering radio signals in communications systems with frequency separation of telephone channels and frequency modulation

Analytical formulas are derived which can be used directly to find the interference level caused by an interfering radio signal in a telephone channel at the upper portion of the group spectrum, as well as the highest interference value in any telephone channel. Formulas are derived for the signal voltages at the input to the receiver, the interference power at the output of the frequency detector and the spectral power densities of the valid and interfering radio signals. The concept of an interference attenuation factor is introduced: this factor relates the ratio of the power of the measurement signal in the circuit of the valid signal and the interference at the output of the telephone channel with the ratio of the power of the valid and interfering signals at the receiver input.