VHF Tropospheric Overwater Measurements Far beyond the Radio Horizon

Using a high-power radar-type transmitter near Boston, Massachusetts, point-to-point measurements have been made at a frequency of 220 mcps on 200- and 400-statute-mile overwater paths extending along the east coast. Comparisons are made with similar data available for overland paths. Correlations between the shorter path field-strength data and sea echo back-scatter near the transmitter site are indicated. Airborne field-strength measurements have also been made out across the North Atlantic Ocean to a distance in excess of 400 miles; the variation of field strength with distance is graphically displayed by this technique.