Abstract: A varactor diode tuner includes a tunable image frequency trap in its input circuit. The trap is part of a tunable bandpass filter and forms a tapped capacitance matching network for UHF television signal carrier frequencies and a low impedance shunt at image frequencies. The trap is formed of discrete capacitors, an inductor and a tunable varactor diode.

Abstract: The VHF and UHF tuners of a television receiver are coupled by a switchable diplexing circuit to a single antenna input terminal. The diplexing circuit includes a first electronic switching means responsive to a U/V bandswitch control signal connected between the UHF tuner and the antenna input terminal. A switchable low-pass filter is connected between the VHF tuner and the antenna input terminal, the switchable low-pass filter including a second electronic switching means responsive to the U/V bandswitch control signal for causing the low-pass filter to exhibit a first low-pass frequency response having a cut-off frequency fc in the VHF mode and a second low-pass frequency responsive having a cut-off frequency less then fc in the UHF mode.

Abstract: A signal splitter-balun assembly for coupling a UHF antenna and a VHF antenna to a single input terminal of a television receiver is disclosed. RF isolation is provided by means of appropriate filtering, 60 Hz isolation is provided by means by a pair of capristors, and the required impedance transformation is provided by means of a conventional balun transformer in a low cost unit utilizing a minimum number of components.