Continuous tuning arrangement for a multiband television receiver

A tuning system for continuously tuning a television receiver to various channels in a low VHF band, a high VHF band and a UHF band, comprising:

• a frequency tunable circuit;
• voltage variable means for determining the frequency to which said tunable circuit is tuned in response to a tuning voltage, said tuning voltage having first, second, third, fourth, fifth and sixth magnitudes corresponding to the lowest frequency channel in said low VHF band, the highest frequency channel in said low VHF band, the lowest frequency channel in said high VHF band, the highest frequency channel in said high VHF band, the lowest frequency channel in said UHF band and the highest frequency channel in said UHF band, respectively, said voltage variable means having a voltage versus channel characteristic which is nonlinear in at least one of said bands;
• means for developing first, second, third, fourth, fifth and sixth voltages corresponding to magnitudes of said tuning voltage slightly less than said first magnitude, slightly greater than said second magnitude, slightly less than said third magnitude, slightly greater than said fourth magnitude, slightly less than said fifth magnitude and slightly greater than said sixth magnitude, respectively;
• a dielectric substrate;
• first, second and third electrically separate sections of resistive film formed on said dielectric substrate in a circular path in the order named, first and second points along said circular path defining the beginning and end, respectively, of said first section, third and fourth points along said circular path defining the beginning and end, respectively, of said second section, fifth and sixth points along said circular path defining the beginning and end, respectively, of said third section;
• first, second, third, fourth, fifth and sixth means for developing first, second, third, fourth, fifth and sixth voltages corresponding to said first, second, third, fourth, fifth and sixth magnitudes of said tuning voltage, respectively, at said first, second, third, fourth, fifth and sixth points;
• a movable contact;
• means for moving said movable contact across said first, second and third sections along said circular path;
• said tuning voltage being developed at said movable contact;
• and
• the one of said sections of resistive film corresponding to said one of said bands having a nonlinear voltage versus channel characteristic being shaped to compensate for said nonlinear voltage versus channel characteristic so that points along said one section corresponding to adjacent channels are separated by substantially equal angular increments.