Methods for Calculating Distance Separation for Noninterfering Transmissions

Methods are presented for computing the distance required between transmitters with co-channel frequency assignments so that interference between them may be held below a specified level. Separate consideration is given to utilization probabilities resulting from communications traffic volume and to factors which are a function of the transmission medium and equipment characteristics. A graphical-analytic method is developed which reduces the usual path attenuation vs distance charts to normalized form. This permits rapid translation of the prescribed path attenuation into distance for any combination of antenna heights and wavelength in the line-of-sight region. The normalized charts also facilitate establishment of a probability, due to lobing, that path attenuation in a given region will be above or below a specified value when the transmitters or receivers are in motion. The basic methods are developed for distances well within the line-of-sight region, but special consideration also is given to distances near the horizon where the usual approximations do not apply.