Abstract: A loading coil connects between an antenna and ground and has an intermediate feed point. A conductive member opposes at least several turns of the loading coil and is disposed in distributed capacitive relationship therewith. The conductive member and coil are separated by a dielectric member. The conductive member is preferably movable with respect to the coil to change the resonant frequency of the antenna and may be a conductive ring or disk axially shiftable with respect to the coil or a vane pivotable with respect to such coil. In one embodiment, the conductive member is fixed and the dielectric member, having a dielectric constant different from air, is shiftable to change the distributed capacitance of the conductive member and coil and hence the resonant frequency of the antenna apparatus.

Abstract: In a transmitter or transceiver having alternately selectable transmission frequency channels, frequency selection switching is actuable for switching the transmitter from channel to channel and for stopping at the desired channel. A device, such as a microphone push-to-talk switch actuates the transmitter. Lock-out circuitry, interconnected with the transmitter actuating device and frequency selection switching, precludes simultaneous transmission and channel switching. In one embodiment, operating potential is removed from channel switching circuitry when the transmitter is in actuated condition and such channel switching circuitry is supplied operating potential only with the transmitter in its nonactuated condition. In further embodiments, frequency selection switching is disabled or blocked when the transmitter is actuated and only becomes enabled when the transmitter is deactuated.