Abstract: An improved preselector cavity arrangement and RF selectivity assembly includes a cast housing for the preselector with a plurality of interconnection apertures or slots, each being surrounded by a boss. Each boss is mated with a slot in an adjoining housing of an interconnected module for allowing input, output and injection connections to be made to the preselector without intermediate connections to the supporting printed circuit board. One adjoining housing may contain the RF amplifier with coupling and impedance matching to the amplifier output coil provided by a loop from the preselector input. The loop passes through the shielded aperture, couples to the output coil by passing around the coil form and then returns to ground on the preselector casting. The injection filter and tripler/mixer modules may be contained in other adjoining housings and also coupled to the preselector through shielded apertures. To minimize RF spray radiation no interconnections are made via the printed circuit board.