Multiple diversity and equalization used on long over-water LOS path

A sophisticated line-of-sight (LOS) terminal configuration is described. The link is a 55-mile over-water path across the English Channel. The system uses quad space diversity and dual frequency diversity as well as slope equalization at intermediate frequency and transversal equalization at baseband. The complicated design was necessitated by a difficult path prone to ducting and other anomalous propagation; large waveguide losses due to tall towers; and an inability to test the full two-frequency configuration prior to cutover to live traffic. Eight receivers were used rather than four to try to obtain the best possible performance using off-the-shelf hardware. Precutover data for single-frequency operation were sufficiently encouraging to allow cutover to live traffic. Most anomalous propagation occurred from late May through August. Subsequent preliminary data showed that in the first six months of postcutover dual-frequency operation there were fewer than 32 10EXP-3 and 41 10EXP-4 error seconds