April 1968 | NTIA Technical Memo ERL TM ITS 140

Required protection radios for frequency sharing in a VHF air traffic control commun­ications system with a satellite terminal

Robert W. Hubbard; Donald V. Glen

Abstract: This report presents the results of laboratory tests conducted to make preliminary determination of the required protection ratios for satisfactory sharing service in a VHF ATC communications system. The data given may be used to predict a quantitative measure of performance for any voice communication system in the VHF band and including a satellite terminal. The principal results of the work are data from performance tests on typical ATC equipment to determine required desired-to-undesired signal ratios (DIU) for various grades of service. Percent intelligibility is plotted against DIU. The ATC controller is very skilled in reading typical ATC messages under severe interference conditions. There is a sharp threshold in intelligibility followed by rapid degradation in performance for both AM and FM systems.

Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

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