Operation of receivers NTV-1000 and NTV-2000 with dual-band converters. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Телевидение

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How to use NTV+ receiving equipment to receive programs from other satellites? The answer to this question is of interest to those who would like to increase the number of programs they receive, and to those who, for economic reasons, are forced to stop receiving NTV+ for the time being.

Reception by the NTV-1000 and NTV-2000 receivers of programs from other satellites (for example, from one of the five Hot Bird satellites) is possible when using dual-band (10,7 ... 11,7 GHz and 11,7. ..12,75 GHz) converters (LNB unit). However, the problem arises - how to manage the converters.

Range switching in these converters is carried out by applying a tone signal (22 kHz) through the power circuit. The receivers of the "NTV +" system: "NTV-1000" and "NTV-2000" do not provide such modes, so you will need to install a tone generator, but at the same time they must also be controlled. As for the NTV-200 receivers, this problem has been solved (see the article by V. Ivanov "Refining the tuner of the NTV + system for receiving programs from the Hot Bird satellite in Radio", 1997, No. 11, p. 14 And for the receivers "NTV-1000" and "NTV-2000" it is a little more complicated, since there is no special signal for turning on the tone generator. I propose one of the options for solving this problem.

The first thing to do is to make and install a 22 kHz tone generator. It can be assembled according to a simpler scheme (Fig. 1) than suggested in the article by V. Ivanov - based on a multivibrator based on logical elements DD1.1, DD1.2. Elements DD1.3, DD1.4, connected in parallel, perform the function of a buffer amplifier. At their output, an integrating circuit R3R4C3 is installed, which converts the rectangular oscillations of the multivibrator into exponential (close to triangular). The output signal through the capacitor C4 is fed to the control input of the voltage regulator U303 of the receiver. Practice has shown that to switch the converter, its amplitude should be 0,3 ... 0,5 V.

All parts are placed on a printed circuit board made of one-sided foil fiberglass on the side of the conductive tracks (Fig. 2).

The option of installing the board in the receiver case is shown in fig. 3.

The board is attached through a hole with an M2,5 screw to a ledge on the bottom of the receiver case, next to the heat sink of the voltage stabilizers. The power wires (pins 1 and 3 of the generator board) are carefully soldered to the pins of the microcircuit (U301) of the voltage regulator. The signal output circuit (pin 2) is connected to the output of a voltage regulator made on the U303 chip. And to output 4 of the generator board, a control signal is supplied from the receiver.

As a control signal, you can use various commands given from the control panel, which are stored in the receiver's memory. You can, for example, use commands to switch the decoder. There are four such commands: "no", "d1", "d2", "d3" - they are available on various receiver buses. If you apply a control signal from the jumper "J23", which is located next to the "CON4" connector, then the tone generator will turn on when the first and fourth of the above commands are activated.

But here one circumstance should be taken into account: if the decoder is disabled, and it is not needed, then when these commands are switched, the image and sound signals on the "TV" card and at the RF output will disappear. To prevent this from happening, on the "DECODER" scart, you need to connect jumpers to pins 1 and 2, 5 and 6, 19 and 20. But at the same time, the image brightness and sound volume may change.

For control, you can use the button and the "DEV" signal (two-stage change in image brightness), but then, simultaneously with switching converters, the brightness will automatically change. In this case, the signal to output 4 of the tone generator is removed from jumper J36, which is located next to the tuner (microwave unit) of the receiver. The generator will start working at the command "dR" and turn off at the command "br" (both are indicated on the receiver's display).

The adjustment comes down to setting the generator frequency and checking the amplitude of the output voltage. Do this before installing the generator board in the receiver. The generator frequency (22% 2 kHz) is set by resistor R1, and the amplitude of the alternating voltage at the output is set by resistor R4. After installing the board, the engine of the resistor R4 must be set to the left (according to the diagram) position and, switching the appropriate commands from the control panel, apply a log level to the control input (pin 4) of the generator. 0 and tune the receiver to one of the TV channels in the range of 10,7 ... 11,7 GHz. Then, switching commands, apply a log signal to the control input of the generator. 1. The converter should switch to another range. If this does not happen, then by increasing the amplitude of the output alternating voltage by rotating the slider of the resistor R4, achieve its switching.

Author: I. Nechaev, Kursk

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