SU1543468A1 - Three-program receiver of wire broadcasting - Google Patents

Abstract

The invention relates to broadcasting. The purpose of the invention is to increase the noise immunity from the interfering channel. The receiver contains filters 1 and 2, transformer 3, switches 4-8 with control buttons 30-32, resistors 9-14, capacitors 15-19, field-effect transistors 20 and 21, bipolar transistor 22, parallel LC circuit 23, source 24 power, detector 25, low-frequency amplifier 26, loudspeaker 27. The goal is achieved by automatically setting the optimum sensitivity. At the same time, sensitivity adjustment is performed instantly and without external interference, thereby maintaining a constant receiver loudness volume both when switching from program to program and when the signal level changes in the radio broadcasting network. The ability of the resonant circuit to operate as an obstruction filter for the interfering channel provides a constant signal-to-external crosstalk ratio. 1 il.

Description

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The invention relates to broadcasting and can be used as a terminal device in se- and three-program wire broadcasting.

The aim of the invention is to increase the noise immunity from the interfering channel by automatically setting the optimum sensitivity.

The drawing shows an electrical circuit of a three-program wired radio receiver.

The three-program receiver of the Joro broadcast contains, the first one and second 2 filters, the transformer 3, the first - fifth switches 4-8, the first - sixth resistors 9--14, the first capacitors 15-19, the first O, and the second 21 field effect transistors , illlar transistor 22, parallel LC circuit 23, power supply 24 Yi, detector 25, low frequency amplifier 26, loudspeaker 27, first 28 and second 29 inputs of a three-program wired broadcast receiver, switch control button 32

The three program receiver of wire broadcasting works as follows.

Inputs 28 and 29 are connected to a forward link. The programs are filtered by filters 1 and 2 for high-frequency channels with their carrier frequency and amplitude-modulated signal and transformer 3 when receiving a low-frequency signal

If none of the O, 31 and 32 buttons is pressed (as shown in the drawing), then none of the programs are played.

After pressing button 31, the first low-frequency channel is turned on. The signal From the output of the transformer 3 through the switch 5 and the resistor 14 passes to the gate of the field-effect transistor 20.

Switch 6 provides the disconnection from the amplification path of the parallel LC circuit 23 and the connection of the resistor 13 to the source 24. The resistor 13 provides the linear gain of the field-effect transistor 20, which operates as a low-frequency amplifier.

The amplified signal is removed from the drain of the field-effect transistor 20 and through the capacitor 17 is fed to the base (bipolar transistor 22, working

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active detector mode. The bipolar transistor 22 opens and the capacitor 16 starts charging with the collector current of the bipolar transistor 22. Depending on the voltage on the capacitor 16, the resistance of the channel of the FET 21 used as a controlled voltage of the resistor increases or decreases, maintaining the corresponding signal at the gate of the field-effect transistor 20, and hence the constant level of the signal based on the bipolar transistor 22 "In the absence of a signal, the capacitor 16 is discharged through the resistor 10 and the field transistor Sistor 21 closes providing maximum amplification of the field-effect transistor 20. Resistor 14 serves to increase the output resistance of filters 1 and 2 and transformer 3, which is necessary for normal operation of the automatic regulation circuit. The signal thus processed is fed through capacitor 19 and the corresponding closed contacts of switch 7 to the input of low-frequency amplifier 26, amplified by it, and reproduced by loudspeaker 27. After pressing button 32, a second channel is turned on with an amplitude-modulated signal and its own carrier frequency. In this case, the button 31 returns to its original position, disconnecting the transformer from the amplifier path. Through the closed contacts of switch 4, filter 1 is connected to the input resistor 14 of the amplifier path.

The switch 6 disconnects the resistor 13 and connects the parallel LC circuit 23 to the power supply 24, which ensures the operation of the field-effect transistor 20 in the high frequency amplification mode. The drain load of this transistor is a parallel LC circuit 23 to which the capacitor 18 is connected in parallel by means of the switch 8 This switch-on ensures that the resulting resonant circuit is tuned to the carrier frequency of the second channel and serves as a blocking filter for the carrier frequency of the third channel.

The above process of automatically adjusting the input gain is repeated. Next, the signal through the capacitor 19 is supplied to

The detector 25, where the envelope of the amplitude-modulated signal is selected and filtered, is then fed through the closed contacts of the switch 7 to the input of the low-frequency amplifier 26, is amplified and reproduced by the loudspeaker 27

After pressing button 30, the third channel is turned on with an amplitude-modulated signal and its carrier frequency. Button 32 returns to the original position. Switch 4 turns off filter 1 and connects filter 2 to resistor 14. Condenser 18 is turned off by switch 8, - and drain load field-effect transistor 20 turns out to be a parallel LC circuit 23, tuned to resonance at the carrier frequency of the third channel and at the same time serving as a blocking filter for the carrier frequency of the second channel. The rest of the receiver’s operation is not tlichaets from the above-described operation in the receive mode of the second channel.

Resistor 9 determines the input resistance of the amplifying path with the field-effect transistor 21 closed. Resistors 11 and 12 and capacitor 15 determine the operating mode of the active detector (bipolar transistor 22)

Thus, when any channel is received, the output level remains unchanged even if the voltage level is underestimated in any of the channels. Sensitivity is adjusted instantly and without external interference, thereby maintaining a constant receiver loudness both when switching from program to program and when the signal level changes in the radio broadcasting network, and the ability of the resonant circuit to work as an obstruction filter for the interfering channel ensures a constant signal-to-internal transient interference ratio

Claims (1)

Invention Formula A three-program wire broadcast receiver containing the first filter, the first and second inputs of which are connected respectively to the first and second inputs of the second filter and the transformer, and are respectively the first and second inputs of three programs 50 0 five 0 five with many wired broadcast receivers, first outputs of the first and second filters and a transformer are connected respectively to the opening contact of the first switch, the closing contact of the first switch and the closing contact of the second switch, the second outputs of the first and second filters and the transformer are connected to the common wire, to which the first terminals are also connected loudspeaker, low frequency amplifier, detector, first capacitor, first resistor and power supply,. The second terminal of which is connected to the second terminals of the detector, the low-frequency amplifier, the second resistor, the second capacitor and the third resistor, the first terminal of which is connected to the second terminals of the first capacitor and the fourth resistor, the first terminal of which is connected to the emitter of the bipolar transistor, the third contact the switch is connected to the first pin of the parallel LC circuit, the second pin of which is connected to the first pins of the third capacitor and the fifth resistor, the second pin of the first resistor is connected To the first output of the sixth resistor, the fourth and fifth capacitors, the fourth and fifth switches, due to the fact that, in order to increase the noise immunity from the interfering channel by automatically setting the optimal sensitivity, the first and second field-effect transistors, whose sources are connected to the common wire and the emitter of the bipolar transistor, the collector of which is connected to the first terminals of the second capacitor and the second resistor and the gate of the second field-effect transistor, the drain of which is connected to the first A output of the sixth resistor and the gate of the first field effect transistor, a drain of which is connected to the second terminal of the parallel LC-circuit and through 0 fourth kbndensator to the closing contact of the fifth switch, the switching contact of which is connected to the second output of the detector and the switching contact of the third switch, the closing contact of which is connected to the second output of the fifth resistor, the base of the bipolar transistor connected to the second output of the first capacitor and through the fifth terminal 5 0 five 7 15434688 the detector to the input of the detector and which circuit is connected to the second terminal to the tactile contact of the fourth switch-loudspeaker, switching the end, disconnecting and switching the beat of the first switch is connected the contact of which is corresponding to the switching contact of the second pereklyuchenny to the output of the detector and input switch and the second output of the sixth do a low frequency amplifier, an output resistor.