Variable frequency U. H. F. local oscillator for a television receiver

Claim 1

An oscillator including amplifying means for exhibiting gain of at least unity including means for providing regenerative feedback to make said amplifying means oscillate, and a resonant circuit coupled to said amplifying means to control the frequency at which said amplifying means oscillates, wherein said resonant circuit is responsive to a control potential to control said frequency, said resonant circuit comprising: first and second capacitance means having respective pairs of first and second electrodes between which respective capacitances are exhibited, said first electrodes of said pairs of electrodes being of the same type and said second electrodes of said pairs of electrodes being of the same type, the value of said capacitances being controllable responsive to respective potentials developed across said capacitance means, said first and second capacitance means being connected in series with their respective first electrodes connected together; an inductance to which said first and second capacitance means are connected to form a tuned circuit; and means for developing said potentials across said capacitance means including means for applying said control potential to said first electrodes of each of said first and second capacitance means so as to change the capacitances thereof in the same sense with respect to each other in response to changes of said control signal; and adjustable means connected to said second electrode of said second capacitance means for causing the potential at said second electrode of said second capacitance means to differ from the potential at said second electrode of said first capacitance means by an adjustable amount to cause said potential developed across said first capacitance means to differ in predetermined relationship from said potential developed across said second capacitance means.