Measurements of transmission loss at high frequencies over 960 km temperate-latitude path

Signal strengths measured at a number of frequencies over a short-range (960 km) path between Lerwick, Shetland Islands, and Slough, England, are compared with those given by two well known prediction methods. Some of the assumptions inherent in the predictions, and their limitations when applied to the path under review, are examined. Suggestions are made for amendments to the methods. The measured signal-strength data are used to test the validity of wave-polarisation calculations and to give estimates of the ionospheric absorption for comparison with the absorptions indicated by the prediction methods.