RADIO-INTERFERENCE PROBABILITY AND ITS EFFECT ON SITE-SEPARATION STANDARDS AND FREQUENCY ASSIGNMENT OF VHF AND UHF CHANNELS.
FEDERAL AVIATION ADMINISTRATION WASHINGTON D C SYSTEMS RESEARCH AND DEVELOPMENT SERVICE
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In this report equations are developed which permit computation of the probability that radio interference will occur in ATC communications. It is shown that the probability of simultaneous occurrence of desired and undesired transmissions utilization probability is a dominant factor affecting the presence or absence of interference. Utilization probability, in turn, is a function of the duration of ground-based and airborne emissions. Transmitter site separation is now the primary consideration for interference control although utilization and other factors are considered informally. Site separation is shown to provide little air-to-air protection under the derogated standards which must exist in congested areas. The fact that communications have not been seriously affected under these conditions is attributed to the existence of a low utilization probability, for which rough estimates are given. Site separation computations are based on worst-case situations which have a very low probability of occurrence. These separations must be violated in practice. Insufficient statistical information is available concerning the present status or projected failure point of the system.