Abstract: A television tuner combining a UHF tuner and a VHF tuner employs a single mixer circuit such that a signal amplified by a UHF amplifier circuit or a VHF amplifier circuit is selectively inputted through a switching diode to this mixer circuit where it is mixed with a local oscillator signal from a UHF or VHF local oscillator circuit and converted into an intermediate frequency signal.

Abstract: An RF converter circuit of a simplified structure includes a tuner circuit, an intermediate frequency amplifier circuit and a frequency conversion circuit connected in this order. An automatic gain control circuit is provided for reforming an intermediate frequency signal from the intermediate frequency amplifier circuit and transmitting the reformed signal to the tuner circuit such that an intermediate frequency signal can be directly converted into a RF signal.

Abstract: Disclosed is a manufacturing method for a tuner comprising the steps of temporarily fixing both chips and discrete parts by using an adhesive and soldering said chips and discrete parts on said substrate when solder-dipping said substrate and a chassis.

Abstract: A bandpass filter for a CATV converter is of the structure with a low-pass filter section with low-pass filters connected longitudinally in a plurality of stages and a high-pass filter section, and comprises a variable trap circuit including a varactor and an inductor, and another varactor connected to one of the capacitors belonging to the low-pass filter section. Capacitances of these varactors are controlled by a tuning voltage so as to eliminate the various problems which would occur in a double-balance mixer to be connected at a later stage in the CATV converter.

Abstract: An RF signal variable attenuation circuit is disclosed having an input terminal for inputting RF signals, an output terminal for outputing attenuated signals, a transmission line connected between the input terminal and the output terminal, first and second PIN diodes inserted in the transmission line in series, a power supply source for supplying a voltage to the first and second PIN diodes, and a control circuit for controlling the conduction of the first and second PIN diodes according to the voltage supplied from the power supply source.

Abstract: A wide-band type high-frequency amplifier circuit characterized in that a voltage feedback circuit is connected across a base and a colletor of an amplifier transistor, a current feedback circuit is inserted into an emitter circuit, and a damper resistance and a condenser having a small capacity are connected to a balun transformer of a collector circuit in parallel.

Abstract: An oscillation circuit includes as its principal components a Clapp capacitor and two feedback capacitors connected to each other and a resonance coil. A first series circuit including a first variable-capacitance diode and a first DC cutoff capacitor is connected in parallel with the resonance coil, while a second series circuit including a second variable-capacitance diode and a second DC cutoff capacitor is connected to a first diode such that a certain polarity terminal of the second variable-capacitance is faced against the same polarity terminal of the first diode. One end of the second DC cutoff capacitor in the second series circuit is connected to the one of the feedback capacitors. Furthermore, means is provided at the joint of the first variable-capacitance diode and the first DC cutoff capacitor for applying a DC voltage to enable the first and second variable-capacitance diodes.