JPS58210727A - Medium wave receiver - Google Patents

Abstract

PURPOSE:To perform reception of good sound quality with high fidelity in the daytime when radio interference disturbance is less and to improve interference exclusion characteristics in the nighttime, by selecting an intermediate frequency band narrowly in the nighttime and widely in the daytime. CONSTITUTION:Each day is divided into the time when radio interference disturbance and bead trouble increase and the time when they decrease, which are set in a control circuit 9. The control circuit 9 detects a clocking circuit 10 reaching the former set time and outputs a control signal at the same time so that while the intermediate frequency band of an intermediate frequency amplifying circuit 3 is narrowed down, a switch circuit 5 is operated to pass the detection signal through a bead eliminating filter 6. Therefore, the propagation state of a radio wave is improved and this time is set to the nighttime when receivable stations increase in number, performing reception free of radio interference from other stations and bead trouble. At the latter set time, the control circuit 9 outputs a similar control signal and while the intermediate frequency band of the intermediate frequency amplifying circuit 3 is widened, the switch circuit 5 is operated to allow a radio wave to by-pass the bead eliminating filter 6. Consequently, the reception of excellent sound quality corresponding to the reception states is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a broadcasting receiver for use in a vehicle, for example.

In conventional medium wave receivers, the performance is determined by the main purpose of use, such as whether to use wideband intermediate amplification based on sound quality or narrowband intermediate amplification based on high sensitivity reception. I've been exposed to it.

However, the former method is susceptible to interference and beat interference at night due to the radio wave propagation characteristics of medium wave broadcasting, while the latter method reduces interference and beat interference, but has the disadvantage that the sound quality is always inferior.

This invention was made to eliminate these drawbacks, and provides a medium wave receiver that can receive high-fidelity sound quality during the day when there is little interference, and has good interference rejection characteristics at night. It is intended to.

Embodiments of the present invention will be described below with reference to FIG. In the figure, (1) is an antenna, (2) is a frequency conversion circuit including high frequency amplification, (3) is an intermediate frequency amplification circuit that can vary the intermediate frequency band, (4) is a detection circuit - (5) (6) is a beat removal filter, (7) is a low frequency amplification circuit including a control circuit for volume, sound quality, etc., and power amplification circuit. In the circuit, (8) is a speaker. (9) is a control circuit that is composed of a microcomputer and the like and detects various signals and outputs control signals; (9) is a clock circuit; (6) is a display circuit for frequency, time, etc.

Next, the operation of this receiver will be explained. First, the control circuit (9) is set to a time on -day when interference and beat disturbances increase and a time when they decrease. Clock circuit 1
The control circuit (9) detects that the set time of the intermediate frequency amplifier circuit (3) has arrived, and simultaneously outputs a control signal.
) and narrow the intermediate frequency band of the beat removal filter (
6) The switch circuit (5) is fully operated so that the detection signal passes through. Therefore, by setting this time at night when the radio wave propagation conditions are good and there are many stations that can be received, good reception without interference from other stations or beat disturbances is possible.

On the other hand, when the latter set time comes, the control circuit (9) outputs a control signal in the same way as described above, and this time the intermediate frequency amplifier circuit (3
), and at the same time, the switch circuit (5) is fully operated to bypass the beat removal filter (6). This enables reception with good sound quality corresponding to one reception state.

As described above, according to the present invention, the reception circuit can be automatically switched at a set time, and a good reception condition is always maintained, and there is no need for any switching operation, making the medium wave receiver particularly suitable for use in vehicles. can be provided.

[Brief explanation of drawings]

The drawing is a block circuit diagram showing one embodiment of a medium wave receiver according to the present invention. (3)...Intermediate frequency amplification circuit, (9)...Control circuit, α0)...Clock circuit. Agent Shin Kuzuno (1 other person)

Claims (2)

[Claims] (1) An intermediate frequency amplification circuit that can fully vary the intermediate frequency band;
It includes a clock circuit and a control circuit that detects when the clock circuit's time reaches a set time and issues a control signal,
A medium wave receiver characterized in that the control signal allows selection of a narrow intermediate frequency band during the night and a wide intermediate frequency band during the day. (2) The intermediate frequency receiver according to claim 1, wherein the detected output of the intermediate frequency passes through a beat removal filter during the night and bypasses this filter during the day.