Appendix E: Watson-Watt's memorandum to the CSS AD on the state of RDF research, 9th September 1935

The proposals for detection and location of aircraft by radio led to the following of metal-framed aircraft to distances of 92 km, to their detection at distances over 60 km. In all cases where detection was possible, the distance of the craft from the observing station could be measured with an accuracy of the order of 1 km. The tests were mainly made in craft flying above 10,000 feet. The craft observed included land craft and marine aircraft.