Apparatus for transmitting bearing information

Abstract

An electronic navigation beacon, particularly for coastal navigation, in which an unmodulated carrier f.sub.c is transmitted from the first antenna of a pair of antennas, and a periodically modulated sideband f.sub.c .+-.f.sub.a is transmitted from both antennas, where f.sub.a is in the audio frequency domain. A cyclical RF phase variation is imposed on the sideband signal transmitted from the second antenna. The effect in space is that of a rotating radial having an audio frequency null, the periodic modulation providing the listener at a remote point with timing information enabling determination bearing as a function of the time of passage of the radial through the remote point relative to the start of rotation of the radial.