Direction finding apparatus

The direction finding apparatus comprises at least two spaced antennas 1, 2 each being connected to a respective receiver with its own local oscillator 8, 20. Each receiver is provided with means 16, 28 for measuring the instantaneous phase of a desired signal or component thereof over a first sampling period. A crossover switching arrangement 32 is provided for interchanging the antennas so that the measuring means can measure the instantaneous phase over a second sampling period from which a value of the instantaneous signal or component thereof is computed. These values are then used by a phase calculation circuit 30 to determine the bearing angle. The apparatus provides a simplified approach to direction finding on frequency hopping signals as well as conventional signals. The use of phase match receivers or receivers with coherent local oscillators is avoided.