This letter describes an investigation into the feasibility of using the bias voltage as the phase-varying parameter in an array of synchronised Gunn oscillators to steer an antenna. The variation in bias changes the frequency of an unsynchronised oscillator, which, when locked, becomes a change in phase while it is oscillating at the pilot frequency. A simple experiment is described in which the interference pattern from two horns is made to sweep through a fringe wavelength with a voltage variation of 400mV in the bias of one oscillator.