Statistics of anomalous tropospheric propagation at UHF frequencies

This paper presents results from a study concerned with the impact of short-term interference due to tropospheric enhancements on UHF services. While annual and monthly path loss statistics have been gathered for long-distance paths over many years, there has been little information available regarding the short-term variability of such interference, or of its correlation between different UHF frequencies. The present study is currently logging such information for a number of mixed paths across the English Channel and North Sea, and results from the first year of records are presented. The opportunity has also been taken to review a number of existing models, from the ITU-R and elsewhere, for the operational prediction of short-term signal enhancements due to tropospheric effects including ducting, and to examine the empirical bases of these models.