A simplified diversity communication system for beyond-the-horizon links

For nearly a year the US Federal TelecomMunication Laboratories have had in operation a 900 mc beyond-the-horizon two-way link between the Nutley, New Jersey laboratories and Southampton, Long Island. Early results using PTM have already been reported. Briefly, an annual median path-loss some 20db greater than that predicted by Bullington was found, but the bandwidth was adequate for pulse modulation. Since then, frequency modulation, frequency division multiplex and diversity reception have been emnloyed. This report covers the present system, with special emphasis on equipment economies achieved and an analysis of diversity combining methods.