JPH0649016Y2 - Small television receiver - Google Patents

Description

[Detailed Description of the Invention] [Industrial application] The present invention relates to a small television receiver, and more particularly to improvement of a small television receiver using a rod antenna.

[Prior Art] Conventionally, a small television receiver (black and white or color) using a CRT or a liquid crystal display (LCD) is used by carrying it to various places, and therefore, a rod antenna is used as a means for receiving broadcast radio waves. Most are using.

FIG. 3 is a schematic block diagram showing an example of a conventional small-sized color television receiver. In the figure, the tuner 4 is connected to the external antenna connection jack 2 and
The rod antenna 1 is connected via the signal switching contact 3. The signal switching contact 3 is provided in association with the external antenna connection jack 2 and is normally closed.
Therefore, the received signal of the rod antenna 1 is normally given to the tuner 4 via the signal switching terminal 3. On the other hand, when the external antenna connection plug is inserted into the external antenna connection jack 2, the signal switching contact 3 is opened and the reception signal of the external antenna is given to the tuner 4. The output of the tuner 4 is given to the intermediate frequency amplifier circuit 5 and separated into an audio signal and a video signal. Intermediate frequency amplifier circuit 5
Is output to the built-in speaker 7 after being amplified by the audio amplifier circuit 6. The video output of the intermediate frequency amplifier circuit 5 is given to the video chroma circuit 8. The video chroma circuit 8 performs processing for contrast adjustment, demodulation processing to color signals, and the like. The output of the video chroma circuit 8 is given to the LCD 10 via the liquid crystal display drive circuit 9 when the television is a liquid crystal television. On the other hand, when this television is a television using a CRT, the output of the video chroma circuit 8 is given to the CRT 12 via the video amplifier 11.

[Problems to be Solved by the Invention] In the small-sized television receiver as described above, it is expected that a clear image can always be obtained without selecting a place to use. However, although there is no problem when the external antenna is used, there is a limit in realizing high sensitivity and high S / N ratio with the characteristics of only the tuner 4 when the rod antenna 1 is used.

Therefore, an object of the present invention is to provide a small-sized television receiver that can always obtain a clear image even when a rod antenna is used and has a simple circuit configuration.

[Means for Solving Problems] A small television receiver according to the present invention comprises a rod antenna connected to a tuner through a signal switching contact, and an external antenna connection jack for connecting an external antenna to the tuner. Normally, the signal switching contact is closed, the received signal of the rod antenna is given to the tuner via the signal switching contact, and when the external antenna is connected to the external antenna connection jack, the signal switching contact is opened. In such a case where only the reception signal of the external antenna is given to the tuner, the high frequency amplification means for amplifying the reception signal of the rod antenna inserted between the rod antenna and the signal switching contact and the signal switching contact are used. A power supply connected to the high frequency amplification means is provided, and when the rod antenna is used, the power supply supplies the driving power to the high frequency amplification means. When the external antenna is used, drive power is not supplied from the power source to the high frequency amplifying means.

[Operation] In this invention, the high-frequency amplification means interposed between the rod antenna and the signal switching contact amplifies the received signal of the rod antenna and then applies the amplified signal to the tuner, thereby realizing high sensitivity. Further, since the power is supplied to the high frequency amplifying means through the signal switching contact, the signal switching contact can also be used as a power switch, and the number of switches can be reduced.

[Embodiment] FIG. 1 and FIG. 2 are schematic block diagrams showing an embodiment of the present invention. Note that FIG. 1 shows a state in which the rod antenna receives broadcast radio waves, and FIG. 2 shows a state in which the external antenna receives broadcast radio waves.

First, the configuration of an embodiment of the present invention will be described with reference to FIGS. This embodiment has the same configuration as that of the conventional example shown in FIG. 3 except for the following points. Corresponding parts are designated by corresponding reference numerals and the description thereof will be omitted. The first feature of this embodiment is that a high frequency amplifier circuit 13 is inserted between the rod antenna 1 and the signal switching contact 3. The high frequency amplifier circuit 13 is for amplifying the received signal of the rod antenna 1, and its output is given to the signal switching contact 3 via the capacitor C1. The second feature of this embodiment is that power is supplied from the power supply 14 to the high frequency amplifier circuit 13 by using the signal switching contact 3 and the transmission path of the reception signal of the rod antenna 1.
Further, between the input terminal 2a of the external antenna connection jack 2 and the tuner 4 and between the power source 14, a DC component removing capacitor C2 and a backflow preventing diode D1 are inserted, respectively. 1 and 2, the circuits after the tuner 4 are not shown, but the configuration may be the same as that of the conventional example shown in FIG.

Next, the operation of the above embodiment will be described.

First, the operation when the rod antenna 1 receives a broadcast wave will be described with reference to FIG. In this case, since the external antenna connection plug 15 is not inserted in the external antenna connection jack 2, the signal switching contact 3 is closed and connected to the input terminal 2a of the external antenna connection jack 2. Therefore, the reception signal amplified by the high frequency amplifier circuit 13 is transmitted to the tuner 4 through the capacitor C1 → the signal switching contact 3 → the input terminal 2a → the capacitor C2. For reference, the flow of the received signal at this time is shown by a dotted line. On the other hand, power is supplied from the power supply 14 to the high frequency amplification circuit 13 through the path of the power supply 14 → diode D1 → input terminal 2a → signal switching contact 3 → high frequency amplification circuit 13. Therefore, the received signal and the DC power supply voltage are superimposed on a part of the transmission path of the received signal. However, since the DC voltage component from the power source 14 is removed by the capacitors C1 and C2, no problem occurs in the high frequency amplifier circuit 13 and the tuner 4. For reference, the power supply path at this time is shown by a chain double-dashed line. As described above, when the rod antenna 1 is used, the received signal is amplified by the high frequency amplifier circuit 13 and then the tuner 4 is used.
Therefore, high sensitivity and high S / N ratio can be realized. Further, the power supply to the high frequency amplifier circuit 13 is
Since the same path as the transmission path of the reception signal of the rod antenna 1 is used, it is not necessary to provide a dedicated power supply line, and the circuit configuration can be simplified.

Next, the operation when an external antenna is used will be described with reference to FIG. In this case, as shown in FIG. 2, the external antenna connection plug 15 connected to the external antenna (not shown) is inserted into the external antenna connection jack 2. At this time, the signal switching contact 3 is opened by the pressing action of the tip of the external antenna connection plug 15, and the signal switching contact 3 is brought into a non-contact state with the input terminal 2a. Therefore, the connection between the high frequency amplifier circuit 13 and the tuner 4 is disconnected, and the high frequency amplifier circuit 13 is disconnected.
The connection between 13 and the power supply 14 is also disconnected. At this time, the reception signal of the external antenna input via the external antenna connection plug 15 is input to the tuner 4 via the path of the dotted line shown in FIG. In this way, by opening and closing the signal switching contact 3,
Since not only the reception signal is switched but also the power supply to the high frequency amplifier circuit 13 is turned on / off, it is not necessary to provide a dedicated switch for turning on / off the power supply. Therefore, the configuration of the device can be further simplified. Further, when the external antenna is used, the power supply to the high frequency amplifier circuit 13 is cut off, so that the power consumption can be reduced.

[Effects of the Invention] As described above, according to the present invention, high sensitivity and S / N can be achieved by providing the high frequency amplification means for amplifying the reception signal of the rod antenna, and the reception signal can be switched. By using the signal switching contact for turning on / off the power supply to the high frequency amplifying means, the circuit configuration can be simplified.

[Brief description of drawings]

1 and 2 are schematic block diagrams showing an embodiment of the present invention, FIG. 1 shows a state in which a radio wave is received by a rod antenna, and FIG. 2 shows a broadcast wave by an external antenna. The state of receiving is shown. FIG. 3 is a schematic block diagram showing an example of a conventional small-sized television receiver. In the figure, 1 is a rod antenna, 2 is an external antenna connection jack, 3 is a signal switching contact, 4 is a tuner, 13 is a high-frequency amplifier circuit, 14 is a power supply, and 15 is an external antenna connection plug.

Claims (1)

[Scope of utility model registration request] 1. A rod antenna connected to a tuner via a signal switching contact, and an external antenna connection jack for connecting an external antenna to the tuner, wherein the signal switching contact is normally closed. The received signal of the rod antenna is given to the tuner through the signal switching contact, and when the external antenna is connected to the external antenna connection jack, the signal switching contact is opened and only the received signal of the external antenna is received. In a small-sized television receiver as provided to a tuner, a high-frequency amplifying unit for amplifying a received signal of the rod antenna inserted between the rod antenna and the signal switching contact, and the signal switching contact are provided. Is connected to the high-frequency amplification means via a power source for driving the high-frequency amplification means, During Ddoantena use supplies drive power to the high frequency amplifying means from said power source, characterized in that so as not to supply the drive power to the high frequency amplifying means from said power source when the external antenna used, small television receiver.