Investigation of Frequency-Modulation Signal Interference

The cause and mechanism of interference between two frequency-modulation signals are analyzed. It is shown that, while the interference of two frequency-modulation signals on the same channel is practically independent of receiver design, off-channel interference depends on the shape of discriminator curve beyond 120 kilocycles off resonance. Methods are developed to calculate the amount of interference for a given receiver, in terms of the relative strength of the interfering signal. Receiver design modifications, which will reduce the amount of interference from different channels, are indicated.