JPS5934183Y2 - Turret type VHF tuner - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a tuning coil segment in a turret type VHF tuner, in which a tuning coil is wound in correspondence to each channel.

Generally, a turret type F tuner performs channel switching by switching and connecting tuning coils of each tuning circuit such as an input circuit, a mixing circuit, and a local oscillation circuit.

For example, usually a coil stick made of synthetic resin is provided with a coil segment 1 in which each tuning coil is wound as shown in Figure 1, corresponding to each channel, and these are switched and connected to the electronic circuit of the tuner. .

In the figure, 2 is an input circuit tuning coil, 3 is a mixing circuit tuning coil, 4 is a local oscillation circuit tuning coil, and both ends of each coil are contacts 6 implanted in a coil stick 5.
is soldered to.

Each tuning coil wound around this coil segment 1 has an inductance according to the frequency of that channel, and when selecting a channel, the contact 6 of the coil segment 1 and the fixed contact (not shown) of the TEUNA come into contact. This allows it to be connected to the tuner's electronic circuit.

By the way, in this way, each tuned circuit has a common capacitance component,
If the inductance is switched for each channel, the oscillation force of the local oscillation circuit will be weaker in higher frequency channels than in lower frequency channels.

Therefore, the frequency allocation of TV channels is roughly divided into the low channel side of channels 1 to 3 and the high quality side of channels 4 to 12. There is a large difference in frequency between the channels.

For this reason, the aforementioned difference in oscillation force appears largely between the low channel side and the high channel side.

Further, the local oscillator circuit output is injected into the mixing circuit through spatial coupling in the coil segment, and the mixing circuit outputs a frequency difference from the input circuit output.

The difference in oscillation force manifests itself in a decrease in the input to the mixing circuit in the high channel, and as a result, the output of the mixing circuit, ie, the output of the tuner, is insufficient in the high channel.

Therefore, in view of the above-mentioned drawbacks, this invention eliminates the difference in output between the low channel and the high channel by improving the tuning coil winding method of the coil segment.

That is, as shown in Fig. 2, in each coil segment of the high channel where the oscillation force is small,
The mixed circuit tuned coil 3' is wound so that the distance between it and the local oscillation circuit tuned coil 4 is narrower than that of the coil segment of the row channel.

First, if each tuning coil is wound around the coil segment 1 of the low channel at the same intervals as in the conventional method as shown in FIG.
As shown in the figure, the mixing circuit tuning coil 3' is wound closer to the local oscillation circuit tuning coil 4.

In this way, even if the oscillation force of the i channel is weaker than that of the low channel, the degree of coupling between the mixing circuit and the local oscillation distribution increases, eliminating the difference in oscillation force and making the output of the tuner uniform. can be converted into

In addition, in the coil segment 1 for the channel shown in Fig. 2, the contacts 6 at the beginning and end of winding of the mixing circuit tuning coil 3' are shifted from the actual coil winding position, but this is due to the mixing circuit tuning coil 3'. This is because the fixed contacts of the tuner to which the coils 3 and 3' are connected are the same common contacts for the low channel and the high channel.

As explained above, this invention is equipped with coil segments in which the input circuit tuning coil, mixed circuit tuning coil, and local oscillation circuit tuning coil are wound around a single stick, corresponding to each channel, and these are connected to the tuner's electronics. For those that are selectively connected to the circuit for tuning, the mixed circuit tuning coil for the high channel is wound closer to the local oscillation circuit tuning coil than the one for the low channel. Therefore, the non-uniformity of the tuner output due to the difference in oscillation power between the high channel and the low channel can be eliminated without adding a special circuit.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a conventional example of a tuning coil segment for a tuner around which a tuning coil is wound, or an embodiment of the low channel coil segment in this invention;
The figure is a front view showing an embodiment of the high channel coil segment of this invention. 1... Coil segment, 2... Input circuit tuning coil, 3, 3'... Mixing circuit tuning coil, 4... Local oscillation circuit tuning coil, 5... Stick, 6... Contact.

Claims (1)

[Scope of utility model registration request] The input circuit tuning coil, the mixing circuit tuning coil, and the local oscillation circuit tuning coil are arranged in a single stick, each with coil segments corresponding to each channel, and these can be selectively connected to the electronic circuit of the tuner. A turret type VHF tuner characterized in that a mixing circuit tuning coil for high channels is wound closer to a local oscillation circuit tuning coil than that for low channels.