JPH0247650Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a tape recorder equipped with a radio receiver, and particularly to preventing interference with radio reception due to oscillation output from a recording bias oscillation circuit of the tape recorder.

(Prior Art) FIG. 1 is a schematic block circuit diagram of a conventional tape recorder with a radio receiver. This tape recorder 1 has a radio receiver section 2 and a tape recorder section 3. Tape recorder section 3
includes a recording bias oscillation circuit section 4. Note that illustration of other circuit sections of the tape recorder section 3 is omitted for convenience of explanation. In addition, the radio receiver section 2
includes an antenna circuit section 5, an amplifier 6, a frequency mixing circuit section 7, a local oscillation circuit section 8, an intermediate frequency amplification circuit section 9, and other circuit sections 10.

FIG. 2 is a specific circuit diagram of the antenna circuit section 5 of FIG. 1. In FIG. 2, 11 is an antenna tuning circuit including a resonant capacitor C1 and a tuning transformer T, C2 is a bypass capacitor, and +B is a DC power supply for supplying tuning voltage. By the way, in a circuit with such a configuration, the oscillation frequency of the oscillation output output from the recording bias oscillation circuit section 4 is 1, the radio reception frequency of the radio receiver is 2, the frequency of the interference signal is 3, the intermediate frequency is 4, It is known that when the local oscillation frequency of the local oscillation circuit 8 is set to 0, the following problems occur. That is, if the reception frequency of the radio receiver is set to 2 and you want to record a signal corresponding to reception frequency 2 with the tape recorder section 2, the antenna circuit section 5 has a signal other than reception frequency 2. Frequency 3 of said jamming signal is also received. The frequency 3 of this interference signal is given by the following equation (1) or (2).

4=(0−3)+1……(1) 4=(0−3)−1……(2) In the case of equation (1), 3 is given by the following equation (3).

3=(0−4)+1=2+1……(3) In the case of equation (2), 3 is given by the following equation (4).

3=(0−4)−1=2−1……(4) Therefore, the antenna circuit section 5 of the radio receiver
At this time, in addition to receiving frequency 2, the interference signals given by equations (3) and (4) are also received, resulting in a state of interference.

For example, if the reception frequency 2 is 1000KHz and the oscillation frequency 1 of the oscillation output of the recording bias oscillation circuit section 4 is
Assuming 54KHz, the frequency 3 of the interference signal is
It will be 1054KHz or 946KHz. For this reason, 1000K
If you are receiving a radio broadcast at 1054KHz or 946KHz and want to record it, you will need to receive not only the radio broadcast you want to receive but also the radio broadcast at around 1054KHz or 946KHz at the same time. This results in a state of interference.

(Purpose) The purpose of the present invention is to prevent the above-described interference from occurring.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 3 is a block circuit diagram of this embodiment, and parts corresponding to those in FIG. 1 are given the same reference numerals. In FIG. 3, reference numeral 30 is a tape recorder with a radio receiver of this embodiment,
This tape recorder 30 includes a radio receiver section 2,
A tape recorder section 3 is provided. The tape recorder section 3 has a recording bias oscillation circuit section 4. Furthermore, the radio receiver section 2 includes an antenna circuit section 5,
It has an amplifier circuit section 6, a frequency mixing circuit section 7, a local oscillation circuit section 8, an intermediate frequency amplification circuit section 9, and other circuit sections 10. This circuit configuration is similar to the conventional example except for the antenna circuit section 5.

This embodiment is characterized by the following configuration. That is, the antenna circuit section 5 of the embodiment includes an antenna tuning circuit section 32 corresponding to the antenna tuning circuit section 11 of FIG. 2, and a high-pass filter 33. This high-pass filter 33 converts the radio reception signal received by the radio receiver section 2 into the frequency mixing circuit section 7.
It has a characteristic of attenuating or eliminating the oscillation output from the recording bias oscillation circuit section 4 provided in the tape recorder section 3. This high-pass filter 33 is set to have a large input impedance and a small output impedance, thereby preventing the impedance balance of the antenna tuning circuit section 32 from being lost.

FIG. 4 shows the antenna tuning circuit section 32 of the embodiment.
FIG. 3 is a specific circuit diagram of a high-pass filter 33 and a high-pass filter 33. FIG. The antenna tuning circuit section 32 includes a resonant capacitor C1 and a tuning transformer T for supplying tuning voltage. The high pass filter 33 includes a field effect transistor TR and a chiyoke coil L. C
2 is a bypass capacitor. Therefore, this high-pass filter 33 first filters the frequency component 2 of the received signal to be received by the antenna circuit section 5 and the recording bias oscillation circuit section 4 of the tape recorder section 3 in the same manner as described above. frequency component
1 is input. Frequency component 1 from recording bias oscillation circuit section 4 has a relationship of 2>>1 with respect to frequency component 2 of the received signal. The inductance of the choke coil L of this high-pass filter 33 is such that the frequency component 1 can be ignored. For example, if frequency component 1 is 54KHz, it is about 27μH. Then the frequency component
1 is grounded via the chiyoke coil L and the bypass capacitor C2. On the other hand, the frequency component 2 of the received signal is made to have a slightly larger impedance, for example, an amplification degree of 1 for the frequency component 2, with respect to the high-pass filter 33's chiyoke coil L. Therefore, the signal is not grounded by the choke coil L or the like and is passed through the amplifier circuit section 6 to the frequency mixing circuit section 7. Therefore, according to this embodiment, when recording a reception signal received by a radio receiver, the oscillation output from the recording bias oscillation circuit section 4 of the tape recorder section 3 causes the radio receiver to interfere with the reception. This eliminates interference. Note that a diode D is inserted between the drain of this transistor TR and the high-pass coil L as shown in FIG. It may be arranged so as not to interfere with the processing.

As described above, according to the present invention, a tape recorder equipped with a radio receiver is provided with a high-pass filter inserted into the antenna circuit section of the radio receiver, and this high-pass filter is used for receiving signals by the radio receiver. The radio reception signal transmitted by the radio receiver is passed through the frequency mixing circuit section, but it has the characteristic of attenuating or eliminating the oscillation output from the recording bias oscillation circuit provided in the tape recorder. If the tape recorder section also attempts to record the radio broadcast while receiving a broadcast, the antenna circuit section receives the frequency of the interference signal in addition to the reception frequency, but this interference signal is transmitted to the high-pass The signal is attenuated or eliminated by the filter, thus eliminating signal interference at the radio receiver section.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of a conventional example, FIG. 2 is a specific circuit diagram of the antenna circuit section of FIG. 1, FIG. 3 is a block circuit diagram of an embodiment of the present invention, and FIG. A specific circuit diagram of the antenna circuit section of the embodiment,
FIG. 5 is a circuit diagram showing another modification of the antenna circuit section of FIG. 4, particularly the high-pass filter. 3
0 is a tape recorder with a radio receiver, 2 is a radio receiver section, 3 is a tape recorder section, 4 is a recording bias oscillation circuit section, 5 is an antenna circuit section, 6 is an amplifier circuit section, 7 is a frequency mixing circuit section, 8 9 is a local oscillation circuit section, 9 is an intermediate frequency amplification circuit section, 33 is a high-pass filter, TR is a transistor, and L is a chiyoke coil.

Claims (1)

[Claims for Utility Model Registration] (1) A tape recorder equipped with a radio receiver is provided with a high-pass filter inserted into the antenna circuit section of the radio receiver, and this high-pass filter is provided in a tape recorder equipped with a radio receiver. Recording bias oscillation, characterized in that it has a characteristic of allowing the received radio reception signal to pass through the frequency mixing circuit section, but attenuating or eliminating the oscillation output from the recording bias oscillation circuit provided in the tape recorder. radio reception interference prevention circuit. (2) The radio reception interference prevention circuit using recording bias oscillation as set forth in claim 1 of the utility model registration, wherein the high-pass filter includes a chiyoke coil.