An RF filter assembly comprising a substrate, an RF waveguide filter mounted on the substrate and a pair of alignment/mounting/RF signal transmission pins extending from respective apertures in the substrate into respective through-holes in the RF filter. In one embodiment, the RF waveguide filter is comprised of first and second blocks of dielectric material coupled together in an abutting side-by-side relationship and the pair of through-holes are defined in the first and second blocks respectively. In one embodiment, respective RF signal transmission pads defined on the respective first and second blocks of dielectric material are abutted against respective RF signal transmission pads defined on the substrate and interconnected by an RF signal transmission line in the interior of the substrate for transmitting the RF signal between the first and second blocks of dielectric material.