Abstract: Improvements are made in a dual frequency echo cancelling assembly for mounting in a hole in the subreflector of a Cassegrainian antenna. Subreflector echo returned to the feed system is cancelled in two frequency ranges by a reflection from the echo cancelling assembly which includes a flat plate, a guard ring surrounding the plate, and a conductive grid between the plate and the feed system. The improvements include wide, thin grid conductors electrically connected to the guard ring and a ring of reflective or absorptive material surrounding the guard ring to cover the subreflector hole edge. When the improved assembly is adjusted for best performance, a stronger reflection in the direction of the feed system is obtained for echo cancelling without sharp resonance peaks. The required diameter for the improved dual frequency echo cancelling assembly is smaller, minimizing blockage of the subreflector and undesirable scattering.