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A design of an inexpensive multi-mode tracking feed antenna, for a circularly polarised signal is described. It uses the TE11 and TM01 modes, in a smooth circular waveguide, to obtain the sum and difference patterns. The higher order mode, TM01 generated within the feed is separated from the dominant mode, TE11 by using the resonant mode filter printed on a thin dielectric material. The design of the resonant mode filter is described in some detail. The use of a printed resonant ring with a dual mode horn makes the design particularly inexpensive. Sum and difference patterns with both the dual mode and the corrugated horn are presented for comparison.