Vhf-uhf varactor tuning system incorporating automatic frequency control with equalization

Claim 2

A VHF-UHF television tuning system of the type incorporating automatic frequency control with AFC equalization for VHF and UHF tuning, and having a pair of varactor tuners, one for VHF tuning and the other for UHF tuning, each comprising at least one varactor tuned stage and a varactor heterodyne oscillator for selecting a particular broadcast channel comprising at least a video modulated carrier and for deriving therefrom an intermediate frequency signal having a video component of a desired frequency which system comprises: a low impedance tuning voltage source supplying voltage to each said varactor tuned stage for establishing said tuned stage in a tuned condition; means including an unbalanced discriminator network responsive to said intermediate frequency signal for developing a control voltage the magnitude of which is dependent upon the deviation of the actual frequency of said video IF component from its aforesaid desired frequency; control voltage equalizing means comprising a voltage divider permanently connected across said unbalanced discriminator network and having high and low voltage terminals; and said VHF varactor heterodyne oscillator being permanently connected between said high voltage terminal of said control voltage equalizing means and said tuning voltage source and said UHF varactor heterodyne oscillator being permanently connected between said low voltage terminal of said control voltage means and said tuning voltage source to effect control of said varactor tuners in an equalized manner and to maintain the frequency of said video intermediate frequency component at its aforesaid desired value by affecting only said varactor heterodyne oscillators independently of said tuned stages.

Claim 3

A VHF-UHF television tuning system in accordance with claim 1 wherein said tuning voltage source comprises a variable resistor and a Zener diode.

Claim 4

A VHF-UHF television tuning system of the type incorporating automatic frequency control with AFC equalization for VHF and UHF tuning and having a pair of varactor tuners, one for VHF and the other for UHF tuning, each comprising a plurality of varactor tuned stages and a varactor heterodyne oscillator, said tuned stages and said varactor heterodyne oscillators each comprising a varactor diode having an anode and a cathode, for selecting a particular broadcast channel comprising at least a video modulated carrier and for deriving therefrom an intermediate frequency signal having a video component of a desired frequency, which system comprises: a low impedance source of tuning voltage comprising a variable resistor and a Zener diode coupled to the cathodes of the varactor diodes in said tuned stages for supplying voltage thereto and establishing said tuned stages in a tuned condition; means including an unbalanced discriminator network responsive to said intermediate frequency signal for developing a control voltage the magnitude of which is dependent upon the deviation of the actual frequency of said video component from its aforesaid desired frequency; a voltage divider including a pair of resistors permanently connected across said unbalanced discriminator network and having a high and a low voltage terminal, said low voltage terminal being the junction of said resistors; and the anode of said VHF oscillator varactor diode being coupled to said high voltage terminal and the cathode of said VHF oscillator diode being coupled to said tuning voltage source, the anode of said UHF oscillator varactor diode being coupled to said low voltage terminal and the cathode of said UHF oscillator varactor diode being coupled to said tuning voltage source to effect control of said varactor tuners in an equalized manner and to maintain the frequency of said video component at its aforesaid desired frequency by affecting only said varactor heterodyne oscillators independently of said tuned stages.

Claim 5

A VHF-UHF television tuning system of the type incorporating automatic frequency control with AFC equalization for VHF and UHF tuning and having a pair of varactor tuners, one for VHF and the other for UHF tuning, each comprising a plurality of varactor tuned stages and a varactor heterodyne oscillator, said tuned stages and said varactor heterodyne oscillators each comprising a varactor diode having an anode and a cathode, for selecting a particular broadcast channel comprising at least a video modulated carrier and for deriving therefrom an intermediate frequency signal having a video component of a desired frequency, which system comprises: a low impedance source of tuning voltage comprising a variable resistor and a Zener diode coupled to the cathodes of the varactor diodes in said tuned stages for supplying voltage thereto and establishing said tuned stages in a tuned condition; means including an unbalanced discriminator network responsive to said intermediate frequency signal for developing a control voltage the magnitude of which is dependent upon the deviation of the actual frequency of said video component from its aforesaid desired frequency; a voltage divider including a pair of resistors permanently connected across said unbalanced discriminator network and having a high and a low voltage terminal, said low voltage terminal being the junction of said resistors; and the anode of said VHF oscillator varactor diode being coupled to said high voltage terminal and the cathode of said VHF oscillator diode being coupled to said tuning voltage source, the anode of said UHF oscillator varactor diode being coupled to said low voltage terminal and the cathode of said UHF oscillator varactor diode being coupled to said tuning voltage source to effect control of said varactor tuners in an equalized manner and to maintain the frequency of said video component at its aforesaid desired frequency by affecting only said varactor heterodyne oscillators independently of said tuned stages.