A relatively simple design for a meteor radar interferometer with 4 receiving antennas is described. A basic 3 element interferometer provides a set of possible directions for each radio echo detected. The ambiguity is resolved using a 4th antenna, placed according to the results of a numerical simulation. Details of the procedure are provided. The resolution in echo direction is between ~1¿ and ~2¿ for altitudes (elevations) above ~30¿ at all azimuths. A general purpose meteor radar based on this principle has been in use since 1986 at Grahamstown, South Africa.