A Frequency Assignment Guide for Tactical FM Radios in the 30- to 76-MHz Frequency Band

A continuing requirement exists to reduce the probability of occurrence of radio frequency interference (RFI) by formulating simple rules which may be easily applied to assignment of frequencies to Army tactical frequency modulation (FM) radio nets. The possibility of formulating a rule for FM cochannel and off-channel frequency assignment to provide adequate, efficient distance separation ratios was investigated. The ratio of the distance between a desired transmitter (DS) and its receiver to the distance between an interfering transmitter (DI) and the receiver for a given probability of correct information transfer is defined in terms of the ratio of desired transmitter RF power output to the interfering transmitter RF power output (PS/PI) and the ratio of desired RF input to the receiver to the interfering RF input to the receiver (S/I) required for a desired link quality. The function relating these variables is shown to be (S/ I-PS/ P1 40 J DI/DS = 10 Graphs of this function are presented for cochannel frequency assignment at the 50 percent and 90 percent confidence level of correct information transfer and at the 50 percent confidence level of correct information transfer for off-channel frequency assignment.