JPH0511565U - Beat cutting device - Google Patents

Abstract

(57) [Summary] [Purpose] Automatically removes the beat disturbance in a radio receiver with a tape recorder to perform good reception of radio broadcasts. The microcomputer 30 is supplied with an AC bias signal from the AC bias oscillator 10 and an oscillation signal from the local oscillator 18 from the frequency divider 32. Then, the values of the AC bias frequency and the reception frequency are obtained from these signals, and the presence or absence of the beat fault is determined based on them. As a result, when it is determined that a beat failure occurs, the transistor Q is driven,
The capacitor C is connected to ground. As a result, the oscillation frequency of the AC bias oscillator 10 is shifted, and the occurrence of beat trouble is prevented.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a radio receiver with a tape recorder such as a radio cassette tape recorder (radio cassette player), and is generated between the harmonics of the alternating bias signal in the AC bias recording circuit of the tape recorder and the carrier signal of the radio receiver. The present invention relates to a beat cut device for reducing beat disturbance.

[0002]

[Prior Art]

 In a cassette tape recorder or the like, AC bias recording is generally used for magnetic recording of audio signals on a tape. When the cassette tape recorder has a built-in radio receiver, a process of recording the contents of the radio broadcast received by the radio receiver on a tape is performed. However, in this case, a beat occurs due to interference between the two depending on the relationship between the harmonics of the AC bias signal and the frequency of the carrier signal of the receiving station. When this beat is in the audible band, the beat sound is mixed with the broadcast signal. This is called beat failure.

A conventional beat cut device for removing this beat failure is shown in FIG. In the figure, a capacitor C is connected to the ground via a beat cut switch 14 in an AC bias oscillator 10 for AC bias recording. When the switch 14 is turned on, for example, the capacitor C influences the time constant of the oscillation frequency in the AC bias oscillator 10, and the oscillation frequency shifts by a predetermined amount. On the radio receiver side, there is a tuner 20 having a local oscillator 18, so that the reception signal of the broadcasting station selected by this is subjected to processing such as amplification and detection by the reproduction processing section 22 and reproduced by the speaker 24. Has become.

According to this conventional technique, when the user of the tape recorder with radio listens to the sound of the speaker 24 and determines that there is a beat sound, the beat cut switch 14 is turned ON. Then, the frequency of the AC bias signal in the AC bias oscillator 10 is shifted, and the beat disturbance is removed.

[0005]

[Problems to be solved by the device]

 However, in the above-mentioned conventional techniques, the user recognizes the beat sound and operates the beat cut switch 14. For this reason, if the user does not have knowledge of beat generation or does not know the existence of the beat cut switch 14, there is a case that the beat trouble cannot be eliminated. .

The present invention focuses on this point, and an object thereof is to provide a beat cut device capable of automatically removing a beat disturbance and favorably receiving radio transmission. .

[0007]

[Means for Solving the Problems]

 The present invention relates to a beat cut device for eliminating a beat disturbance that occurs in a radio receiver with a tape recorder that performs magnetic recording by an AC bias, in which the values of the AC bias frequency and the reception frequency of the radio receiver are set. The present invention is characterized by comprising a comparing means for judging whether or not a beat failure has occurred on the basis of the beat failure, and a frequency shifting means for shifting the frequency of the cross bias based on the comparison result.

[0008]

[Action]

 According to the present invention, the value of the AC bias frequency and the value of the reception frequency are input and compared with the comparison means using, for example, a microcomputer. When there is a possibility of beat disturbance between them, the frequency shift means operates to shift the AC bias frequency by a predetermined amount. This eliminates the beat failure.

[0009]

【Example】

 Embodiments of a beat cutting device according to the present invention will be described below with reference to the accompanying drawings. The same reference numerals are used for the same or corresponding components as those of the above-described conventional example.

First Embodiment First, a first embodiment of the present invention will be described with reference to FIGS. 1, 3, and 4. FIG. 1 shows the main part of this embodiment. In the figure, the oscillation signal output side of the AC bias oscillator 10 described above is connected to the input side of a microcomputer (μCOM) 30. The signal output side of the local oscillator 18 of the tuner 20 is connected to the input side of the microcomputer 30 via the frequency divider 32.

Instead of the beat cut switch 14, the collector side of an NPN transistor Q is connected to the above-mentioned capacitor C. The emitter side of the transistor Q is grounded, and the control output side of the microcomputer 30 is connected to the base side thereof. FIG. 3 shows the main operation part of the microcomputer 30. In this embodiment, the bias frequency measuring unit 30A, the reception frequency measuring unit 30B, and the comparing unit 30C perform the operation as shown in FIG.

Next, the operation of the first embodiment configured as above will be described with reference to the flowchart of FIG. Now, it is assumed that one of the broadcasting stations is received while the contents received by the radio receiver (not shown) are recorded in the tape recorder (not shown).

First, the oscillation signal of the local oscillator 18 in the tuner 20 is frequency-divided by the frequency divider 32 and then taken in by the reception frequency measuring unit 30 B of the microcomputer 30. The reception frequency measuring unit 30B measures the reception frequency of the radio receiver by using the preset intermediate frequency signal frequency of the device and each value of the frequency division ratio of the frequency divider 32 ( Figure 3 step SA).

Next, the oscillation signal of the AC bias oscillator 10 is taken into the bias frequency measuring unit 30A of the microcomputer 30 and its frequency is measured (step SB). In the comparison unit 30C, the harmonic frequency that is n times the measured AC bias frequency is compared with the reception frequency (step SC). Then, from the frequency difference between the two, it is judged whether or not the value is such that a beat is generated (step SD), and if it is not generated, the beat cut processing is ended as it is.

However, when the comparison unit 30C determines that a beat occurs, an operation control signal is output to the transistor Q (step SE). For this reason, the transistor Q is turned on and turned on, and the capacitor C is connected to the ground. Therefore, the oscillation frequency of the AC bias oscillator 10 shifts, and the condition for beat generation with the reception frequency is broken. As a result, the occurrence of beats is automatically and effectively prevented. The reception frequency setting unit 40A in FIG. 3 and step SF in FIG. 4 will be described in the second embodiment below.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. 2, 3, and 4. In this embodiment, as shown in FIG. 2, the oscillation frequency of the local oscillator 44 of the synthesizer tuner (hereinafter referred to as "synthesizer") 42 is changed based on the setting instruction from the microcomputer 40. The reception frequency is set by the reception frequency setting unit 40A of the microcomputer 40 as shown by the broken line in FIG.

Therefore, in the present embodiment, the value of the set frequency in the reception frequency setting unit 40A is directly taken into the comparison unit 30C instead of the reception frequency measuring unit 30B in the above embodiment (step SF), This is compared with the bias frequency measured by the bias frequency measuring unit 30A (steps SB, SC). The subsequent operation is the same as that of the first embodiment.

As described above, according to the present embodiment, the reception frequency and the AC bias frequency are compared with each other, and the frequency of the AC bias signal is automatically shifted depending on whether or not a beat is generated. The beat disturbance is removed regardless of the recognition of the beat disturbance, and a good radio broadcast reception condition is obtained. In addition, the beat cut switch is made into a transistor, which is advantageous in terms of design and cost.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the AC bias frequency is shifted by connecting and disconnecting the capacitor when the beat is generated, but the capacitor may be disconnected to shift the AC bias frequency. In addition, various design changes can be made, such as using inductance or switching elements with different circuit constants. Further, although the microcomputer is used in the above-mentioned embodiment, each part of FIG. 3 may be configured in a hard disk.

[0020]

[Effect of the device]

 As described above, according to the beat cutting device of the present invention, the presence or absence of a beat is determined based on the values of the reception frequency of the radio receiver and the AC bias frequency of the magnetic recording of the tape recorder, and the beat is generated. In this case, since the AC bias frequency is shifted, there is an effect that beat interference can be automatically removed and good reception of radio broadcasting can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a beat cutting device according to the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is an explanatory diagram showing operation contents of the microcomputer in the embodiment.

FIG. 4 is a flowchart showing the operation of the microcomputer in the above embodiment.

FIG. 5 is an explanatory diagram showing a conventional beat cut method.

[Explanation of symbols]

10 ... AC bias oscillator, 18, 44 ... Local oscillator, 20 ... Tuner, 30, 40 ... Microcomputer (comparing means), 30A ... Bias frequency measuring section, 30
B: reception frequency measuring unit, 30C: comparing unit (comparing means),
32 ... Frequency divider, 40A ... Reception frequency setting part, 42 ... Synthesizer tuner, C ... Capacitor (frequency shift means), Q ... Transistor (frequency shift means).

Claims (1)

[Scope of utility model registration request] 1. A beat cut device for removing a beat disturbance generated in a radio receiver with a tape recorder for magnetic recording by AC bias, wherein a value of each of the frequency of the AC bias and the reception frequency of the radio receiver is set. A beat cut device comprising: comparison means for determining whether or not a beat failure has occurred, and frequency shift means for shifting the frequency of the AC bias based on the comparison result.