Abstract: A temperature-compensated tuning screw (22) for use with a cavity filter (20) is provided. The tuning screw (22) has an elongate body (36) with a longitudinal bore (38). A compensating member (40) is positioned at least partially within the bore (38). At least one compensation bimetallic washer (44) deflects with decreasing temperature and causes the compensating member (40) to protrude further from the body (36). The compensation bimetallic washers (44) become flatter with increasing temperature and a coil spring (42) causes the compensating member (40) to be partially retracted into the bore (38). The movement of the compensating member (40) causes an overall length, L, of the tuning screw (22) to change. The tuning screw (22) can be screwed into a hole (32) in a cavity filter (20) so that the tuning screw (22) penetrates the cavity filter (20) a distance, P. A temperature-induced change in L, .DELTA.L, causes a change in P, .DELTA.P. The change in penetration, .DELTA.

Abstract: A feedforward amplifier arranged as a unitized gain block particularly suitable for use in cable communication systems. The feedforward amplifier includes a single circuit board integrally mounting the directional couplers, delay lines and attenuator circuitry in a symmetrical arrangement. The main and error amplifiers are mounted separately from the main circuit board via releasable connectors and each amplifier is arranged on its substrate as a mirror image of the other to provide a symmetrical signal path. The amplifiers and the circuit board are enclosed within a compact metal housing which provides heat sinking for the amplifiers and facilitates removal of the amplifiers for servicing.