Tuning voltage tracking arrangement

Claim 1

In a superheterodyne radio frequency (RF) receiver having a plurality of selectable tuning bands and including a tuning voltage source for providing a tuning voltage variable over a predetermined voltage range for selecting channels in said tuning bands, voltage controlled RF means for selecting an RF signal from a plurality of received RF signals corresponding to respective ones of said channels in response to an RF tuning voltage, local oscillator (LO) means for generating a LO signal having a plurality of frequencies corresponding to respective ones of said channels in response to an LO tuning voltage, mixer means for mixing said selected RF signal and said LO signal to produce an IF signal, tuning circuit means associated with said RF means for tuning said RF means in said tuning bands in response to said RF tuning voltage, and a selection signal source for providing a selection signal voltage to said tuning circuit means for selectively causing said RF means to be tuned in one of said tuning bands, a tuning voltage tracking arrangement comprising: coupling means for coupling said tuning voltage to an RF tuning voltage input as said RF tuning voltage and to an LO tuning voltage input as said LO tuning voltage; selectively enabled voltage modifying means coupled to said tuning voltage source and being responsive to said selection signal voltage for selectively modifying said RF tuning voltage relative to said LO tuning voltage and for providing said modified RF tuning voltage in said one band only when said tuning voltage provided by said tuning voltage source is within a predetermined portion, less than the whole, of said predetermined range so that said RF signal selected by said RF means and the frequency of said local oscillator produced by said local oscillator means track one another to correspond to the same channel for each one of said channels selected throughout said bands.