Radio Direction Finding, or "Radio Direction Finding", is the original name that the RAF and its Aeronautical Council for Research and Development established to designate an electronic detection system long-range, later called radar (radio detection and ranging). One of its greatest developers, and owner of the patent since 1935, was Robert Watson-Watt and his use, although not exclusive, for the RAF Hunting Command at the Battle of England was one of his first applications useful and with some success until that date. Until its commissioning in the RAF, the later radar was still just experiments.
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