Radio-frequency interference in multi-channel telephony F.M. radio systems

An investigation is described of the effect of extraneous radio-frequency interference in frequency-modulation multi-channel radio-telephony transmission systems. The noise power ratio in the output telephony baseband due to an r.f. interfering signal is derived theoretically, and comparison is made with measured values. When the practical limitations in the method of measurement are taken into account, it is concluded that the theoretical results are valid. Results of general application in the design of radio systems are derived from the theory, and the analogy, under certain circumstances, with interference due to long-delay echo-signals is discussed.