JPS63206019A - Preset device - Google Patents

Abstract

PURPOSE:To make the reception frequency band equal to each other by connecting plural preset variable resistors having a sufficiently small residual resistance in parallel via a semi-fixed variable resistor of a comparatively large resistance from a main variable resistor having a comparatively large residual resistance. CONSTITUTION:A DC voltage is supplied to an oscillation circuit comprising a coil 1 and a varactor diode (VC) via a resistor 3 and a changeover switch (SW) 7. The SW 7 is thrown to a contact (a), a main variable resistor (MVC4) is adjusted to obtain a position from which a maximum and a minimum voltage are applied to the VC 2. Comparatively large residual resistances 4a, 4b are connected to the MVC 4. Then the SW 7 is thrown to a contact (b), a preset variable resistor (PV) 5 having a small residual resistance is adjusted to generate a maximum voltage, and a semi-fixed variable resistor 8 having a comparatively large resistance is adjusted to produce the same maximum voltage as that for the MVC 4. Then the PV 5 and the semi-fixed variable resistor 9 are used to obtain a minimum voltage equal to that of the MVC 4. The similar adjustment is applied to the PV 6. Thus, the width of the reception frequency band is arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a receiving frequency presetting device using a variable capacitance diode used in television receivers and radio receivers.

2. Description of the Related Art In recent years, preset devices have attracted attention as a device that relieves the user from the troublesome task of selecting broadcast stations.

An example of a conventional presetting device will be described below with reference to the drawings.

FIG. 2 shows a resonant circuit of a local oscillator circuit of a conventional preset device. In Figure 2, 1 is a coil that constitutes the local oscillation circuit, 2 is a variable capacitance diode that determines the oscillation frequency of the local oscillation circuit in combination with the above coil 1, and 3 is a resistor that applies DC voltage to the above variable capacitance diode 2. , 4 is a main tuning volume that applies a voltage corresponding to its variable position to the variable capacitance diode 2, 4-a and 4-b are residual resistances of the volume 4, and 6 and 6 correspond to the desired reception frequency. A preset volume 7 for presetting the local oscillation frequency includes contacts a and b for switching the voltage applied to the variable capacitance diode 2 to correspond to the main tuning volume 4 or the preset volume 5.6.

It is a switch with

The operation of the preset device configured as described above will be explained below using FIG. 2.

First, in order to match the preset frequency, switch 7
switch to the contact point, change the main tuning volume 4, change the voltage applied to the varicap 2, and tune to the desired broadcast frequency. Next, the switch 7 is switched to the contact position, and the preset volume 6 is varied so that the same broadcast frequency as that set by the main tuning volume 4 can be received. Furthermore, another broadcast frequency is received with the main tuning volume 4, and the preset volume 6 is adjusted using the same procedure.

Once the above settings are completed, the desired broadcast frequency can be received by closing the switch 7 or switching it to C.

Problems to be Solved by the Invention However, in the above configuration, the main tuning volume 4 uses a volume with large residual resistance in order to ensure linearity with respect to frequency. Preset volume 6 is higher than the reception bandwidth of volume 4.
．． 6's reception band has expanded, and West Germany's FT
This had the problem of not being able to satisfy Z regulations and the like.

In view of the above problems, the present invention provides a preset device that can make the reception band of the main tuning volume and the reception band of the preset volume the same.

Means for Solving the Problems In order to solve the above problems, the presetting device of the present invention includes a coil and a variable capacitance diode that determine the resonant frequency of the local oscillation circuit, and a variable capacitance diode that varies the voltage applied to the variable capacitance diode. A main volume having a relatively large residual resistance with respect to the variable width of the main body, and a plurality of preset volumes having a sufficiently small residual resistance with respect to the variable width of the main body and connected in parallel to the main volume, A semi-fixed resistor corresponding to the residual resistance of the main volume is connected between the common connection portions of the raw volume and the preset volume, and the outputs of the main volume and the preset volume are switched by a switch and applied to the variable capacitance diode. It has the following configuration.

Effect of the present invention With the above-described configuration, by connecting a semi-fixed volume corresponding to the residual resistance of the main volume between the main volume and the preset volume, the variable range of the voltage applied to the variable capacitance diode by the main volume and the preset volume can be adjusted. The variable range of the voltage applied to the variable capacitance diode can be adjusted to be the same, and the reception band band by the main volume and the reception band band by the preset volume become exactly the same.

Further, the preset volume has a sufficiently small residual resistance compared to its variable width, and even if there are a plurality of preset volumes, the above reception frequency band can be obtained with only the above two semi-fixed volumes.

Embodiment Hereinafter, a preset device according to an embodiment of the present invention will be described with reference to the drawings.

First, FIG. 1 shows a resonant circuit of a local oscillation circuit of a presetting device according to the present invention. In FIG. 1, 1 is a coil that forms a resonant circuit of a local oscillation circuit, 2 is a variable capacitance diode that forms a resonant circuit with the coil, 3 is a resistor that applies a DC voltage to the variable capacitance diode 2, and 4
is a main tuning volume; 4-& and 4-b are residual resistance components of the main volume 4; 6 and 6 are preset volumes; 7 is a switch for selecting the source of voltage applied to the variable capacitance diode 2; The above is the same configuration as the conventional example. 8 and 9 are semi-fixed volumes having a value larger than the residual resistance of the main volume.

The operation of the preset device configured as described above will be described below with reference to FIG. 1.

First, switch 7 to contact a, and set main volume 4 to the position where the voltage applied to variable capacitance diode 2 is maximum.
to be fixed. Next, switch the switch 7 to the contact position, set the preset volume 6 to the position where the voltage applied to the variable capacitance diode 2 is maximum, and then turn the semi-fixed volume 8
Turn the voltage so that the voltage applied to the variable capacitance diode 2 when the switch 7 is set to the contact a is the same as the voltage applied to the variable capacitance diode 2 when the switch 7 is set to the contact.

Next, switch the switch 7 to contact & again, set the main volume 4 to the position where the voltage applied to the variable capacitance diode 2 is the minimum, and switch the switch 7 to the contact, the voltage applied to the variable capacitance diode 2 will be the minimum. Adjust the preset volume 6 and turn the semi-fixed volume 9 to match the value of the minimum voltage applied to the variable capacitance diode 2. With the above adjustment, the voltage range applied to variable capacitance diode 2 is the same as when using main volume 4 and when using preset volume 5.
You can do exactly the same thing as when using .

Also, when the switch 7 is switched to the contact point C, the residual resistance of the preset volumes 6 and 6 is sufficiently small compared to the variable width of the main body, and the residual resistance of the main volume 4 is 4-& or a-.
Since it is negligibly small compared to b, the voltage range applied to the variable capacitance diode 2 is the same value as when the switch 7 is switched to contact a or b.

As described above, according to this embodiment, the residual resistance 4 of the main volume 4 is located between the main volume 4 and the preset volume 6.6.
By connecting two semi-fixed volumes 8.9 corresponding to -a and a-b, the variable range of the voltage applied to the variable capacitance diode 2 by the main volume 4 and the variable capacitance diode by multiple preset volumes 5゜6. The variable ranges of the two applied voltages can be adjusted to the same value. As a result, the reception frequencies of the main volume 4 and the preset volume 6.6 become exactly the same.

Effects of the Invention As described above, the present invention provides a main volume having a relatively large residual resistance relative to the variable width of the main body, and a plurality of main volumes having sufficiently small residual resistance relative to the variable width of the main body connected in parallel to the main volume. A semi-fixed volume corresponding to the residual resistance of the main volume is connected between the main volume and the preset volume, and the output of the main volume and the preset volume is switched with a switch to locally control the volume. Depending on the rate applied to the variable capacitance diode forming the resonant circuit of the oscillation circuit, it is possible to make the reception frequency bands of the plurality of preset volumes and the main volume the same.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a resonant circuit of a local oscillation circuit of a preset device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a resonant circuit of a local oscillation circuit of a conventional preset device. 1... Coil forming a resonant circuit, 2...
... Variable capacitance diode forming a resonant circuit, 4...
...Main volume, 5.6...Preset volume, 7...Selector switch, 8,9...
...Semi-fixed volume.

Claims (1)

[Claims] A main volume that has a relatively large residual resistance with respect to the main body variable width, a plurality of preset volumes that have a sufficiently small residual resistance with respect to the main body variable width and are connected in parallel to the main volume, and the above preset volume. semi-fixed volumes each connected in series between the common connection part of and the main volume, a switch for switching the output of the main volume and the preset volume, and a variable capacitance diode to which the DC voltage taken out through the switch is applied. and a coil that constitutes a local oscillation circuit through parallel resonance with the variable capacitance diode.