Toko, Inc.

Matsushita Electric Industrial Co., Ltd.

Matsushita Electrical Industrial Co., Ltd.

Hajime Yokoyama

Noboru Takada

Takashi Ikegame

Yusuke Okamoto

Makoto Torakawa

In an electronic tuning circuit for AM receiver including a radio-frequency tuning circuit and local oscillator circuit each using a variable capacitance diode, the local oscillator circuit comprises an oscillation coil; a padding capacitor connected in series with the oscillation coil; a first variable capacitance diode connected at one end in series with the oscillation coil; a first and a second fixed capacitor connected at one end in series with each other; and a second variable capacitance diode connected in parallel with the second fixed capacitor. The second fixed capacitor has its other end connected to a connection point between the padding capacitor and the first variable capacitance diode. The first fixed capacitor has its other end connected to the connection point between the oscillation coil and one end of the first variable capacitance diode. A tuning voltage is applied to the first and second variable capacitance diodes, thereby reducing tracking error over the entire receiving frequency band.

Electronic tuning circuit for AM receiver

An electronic tuning circuit for AM receiver is disclosed which is so designed that tracking errors are minimized by increasing the accuracy of constants for tuning coils, oscillation coils and capacitance elements incorporated in an antenna tuning circuit, a high-frequency amplifier circuit and a local oscillator circuit which constitute the electronic tuning circuit. After the electronic tuning circuit has been mounted in place, tracking adjustment is effected at one point of the receiving frequency band, or alternatively no such adjustment is required.

Electronic tuning circuit for AM receiver which is easy to effect

A receiver equipped with an electronic tuning circuit which uses voltage-variable reactance elements such as variable-capacitance diodes or the like in the radio-frequency tuning circuit and oscillation tuning circuit thereof. The oscillation tuning circuit includes a novel padding capacitor constituted by a composite circuit of a variable-capacitance diode and fixed capacitors connected at the position where a conventional padding capacitor is connected. With such an arrangement, it is possible to make tracking error negligibly small over a frequency band ranging from a low receiving frequency to a high receiving frequency, by applying a tuning voltage to the composite padding capacitor.

Electronic tuning receiver

In a tuning circuit for AM receiver, tuning coils, oscillation coils and capacitance elements of an antenna tuning circuit, a radio frequency amplifier circuit, and a local oscillator circuit are accommodated in discrete shield casings for high frequency coils; and the discrete shield casings are disposed in a row and united with each other in the form of blocks, thereby eliminating the necessity to effect tracking adjustment.

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Saitama, Japan

Hajime Yokoyama