Four band VHF varactor tuner to cover extended CATV band utilizing two switching diodes per resonant circuit

Claim 1

In a television receiver tuner operable for tuning a plurality of television signal bands, the improved apparatus comprising: bandswitch means having a plurality of output conductors for developing a different set of bandswitch control signals defining each of said television signal bands; a tuned circuit including a first band-switchable inductive network and a varactor diode, said first band-switchable inductive network being responsive to said bandswitch control signals for assuming a different effective inductance for tuning each of said television signal bands; a mixer transistor having an input electrode; capacitance means coupled in series between said input electrode and said tuned circuit; and a second band-switchable inductive network coupled to said input electrode and responsive to said bandswitch control signals for connecting a different value of effective inductance in shunt with said input electrode for each of said television signal bands, each of said different values of inductance of said second inductive network providing, in association with said capacitance means, a resonant frequency below the lowest channel frequency of the corresponding one of said plurality of television signal bands for matching the impedance coupled to said input electrode with the impedance of said mixer transistor at said input electrode at the low end of the respective television signal band.