This report presents the results of field strength measurements on u.h.f. transmissions on 495 Mc/s and 560 Mc/s over land paths at distances up to 294 miles (473 km). These measurements extended over a period of approximately three years and have been used in the preparation of field strength/distance curves for various percentages of the overall time. The results are compared with the measurements at 180.4 Mc/s made over similar transmissions paths and reveal a significant dependence of field strength on frequency. The measurements were used by Study Group V of the C.C.I.R. in the preparation of field strength curves for troposheric propagation at distances beyond the horizon.