Abstract: A cable television up-down tuner includes a first frequency up conversion stage in which a first local oscillator, tunable over a wide frequency range, is coupled to a ring diode mixer having individual biasing networks in series with each diode. A combination high pass and low pass filter provides a bandwidth coupling of input signals to the mixer. An intermediate frequency amplifier couples the up converted signal to a second mixer. A fixed tuned second local oscillator down converts the intermediate frequency signal to a selected television channel frequency. The first local oscillator includes a printed circuit board transmission line resonator which is tuned by a varactor diode. The two local oscillators are positioned adjacent the corners of a quadrilateral housing and are isolated from each other by three wall-type shields.

Abstract: An all-electronic television tuning system has a sequentially accessible multi-position two digit memory coupled to a viewer controlled channel number selection means for providing storage and recall of selected two digit channel numbers in a sequence established by loading selected channel numbers into fifteen of sixteen serial memory locations. The system has program and operate modes, corresponding respectively to storage and recall of channel number information, and the memory has a sixteenth, particular location accessible only in the operate mode for providing immediate all channel tuning control for the viewer irrespective of the pre-programmed channel number sequence.

Abstract: A signal recognizing television tuning system employing a varactor tuner and a channel number computer for supplying derived channel numbers and intrachannel fractions, based upon the local oscillator frequency, to a comparator which controls a ramp voltage source for the varactor tuner. A digital counter supplies a selected channel number to the comparator and the ramp voltage is changed until (1) equality exists between both derived and selected channel numbers and (2) the intrachannel fraction is within predetermined limits such that the system is tuned to receive only signals falling within a restricted frequency range. If no signal is recognized, the counter supplies a next adjacent channel number to the comparator. Signal recognition means stop further operation of the counter upon recognition of a signal within the restricted frequency range.