This report describes a radio propagation measurement campaign that has been performed along paths between the Netherlands and the United Kingdom. The campaign focused on UHF propagation on mixed land/sea paths. Special attention was given to calibration accuracy and validation of the measurement data. The result is a highly accurate and very extensive set of measurement data, that can be used for validation of existing propagation models and models being (re)developed. Inaccuracies in the model have been indicated by several parties since the introduction in 2001 of the propagation model of Rec. ITU-R P. 1546, specifically on paths where radio waves travel partly over land and partly over sea. This research seeks to check the existence of these inaccuracies and assess their impact. Furthermore an analysis is made of possible causes in order to initiate discussion on how to correct them. The measurement results have been compared with calculations using the propagation model of Recommendation ITU-R P.1546-4. The differences between the model and measurements have been analyzed to obtain conclusions on the existence and the magnitude of the error.