Important aspects of transhorizon propagation at 2 GHz over the English Channel

Three 2 GHz radio paths have been established in the British Channel Islands to study the characteristics of long-range UHF propagation over the sea. Enhanced signal strengths (ESS) have been observed on all three radio links, predominantly in the late afternoon and evening periods in the spring and summer months. Relevant over-sea propagation mechanisms (e.g. low-lying evaporation ducts and higher-level ducting structures) have been identified and suitably modelled. The evaporation duct appears to be the primary propagation mechanism during most periods of normal reception. However, our analysis suggests that specifically during periods of signal strength enhancement, higher-level ducting structures become more dominant. In this paper, various statistical data related to tropospheric ducting in the region have been presented to confirm these observations.