SU57735A1 - Device for receiving telegraph signals - Google Patents

Description

During multiple telegraphing by radio, as well as during reception with a narrow bandwidth of signals, at the reception signals, passing through filters with a narrow band, are converted from rectangular signals into signals with a very rounded top and a merged base. So, at work speeds of 250 words per minute and more and at a filter bandwidth of 500 Hz, only the First Harmonic passes through the filter at pai6oTe at the points, and the signal has a form with an envelope - a sinusoid.

The foregoing explains FIG. 1 of the drawing, in which the upper part a shows the waveform before the filter, and the lower part b shows the waveform after the filter with a bandwidth of 500 lane / sec, during telegraph operation at speeds greater than 250 words per minute.

At the receiving end, the signal has one more unpleasant feature: due to fading, the amplitude of the signal varies within large limits (tenfold) several times per second. All this creates great difficulties in receiving such signals; in. Radiobureau need to send

signals of unchanged form (rectangular), of the same amplitude and without the sign predominating over the pause.

The proposed device for receiving telegraph signals is intended to convert signals of rounded shape and smaller amplitudes (fading) into signals of rectangular shape and constant amplitude.

This is achieved by applying to the grid a limiting lamp of two voltages opposite in sign, one of which sends a rectified signal voltage and monitors all its changes during fading, and applies a delayed filter signal to the rectified voltage signal in the circuit of the rectified signal. signal for a time sufficient to increase the bias voltage to the required value after a long pause.

The scheme of the proposed device is shown in FIG. 2 drawings. As can be seen from this circuit, in the case of receiving multiple operation, the signal from the receiver output I goes to narrowband splitter filters Φ, each of which has its own low-frequency amplifier unit Y, ending with an output transformer having one primary winding I and two secondary windings Exits II and III.

Winding II develops a signal voltage, which is rectified by diode A and fed to an HF delay filter with output load.

.

Winding III develops a bias voltage, which is rectified by diode B and fed to capacitor SEM

with output load.

Voltage on si ™. should be twice the voltage at RCM.

The voltage received on the voltage folded with the opposite sign, m on Rc ", is fed to the grid of the restrictive stripes O.

If we cut out the middle part (in amplitude) of the tone signal, the envelope of which is a sinusoid (the limiting case), then the signal (point) and pause will be equal in duration to

In the described scheme, this is done: since the grid of the limiting lamp O receives an offset equal to half the amplitude of the signal (i.e. the bias voltage), the signal (signal voltage) will begin to affect the grid of the limiting lamp only from that moment how the signal voltage will exceed the bias voltage; it is only necessary that the bias voltage be increased earlier, ahead of the appearance of the signal on the limiter grid.

With large amplitudes, the arrival of xx signals, the voltage of the signal,

reaching a value of y and opening the lamp (restrictive), later, due to the grid currents in the limiter, will drop by R ogre. As a result, on the anodio “load of the limiting lamp, an almost rectangular signal will take place. The diagram shown in FIG. 2, ends with a limiting lamp, but under actual conditions the circuit may end with a building tone or a DC amplifier, depending on the requirements of the Radio Bureau.

Regardless of the magnitude of the amplitude of the signal arriving at the grid of the limiting lamp, its middle part will be affected. With fading, when the signal amplitude falls, the bias voltage also decreases proportionally; in this case, it is only necessary to observe the condition that the constant time of the discharge of the circuit Sem - cm is small enough to follow the sinking.

The retarding filter ZF delays the appearance of the signal on the grid of the limiting lamp O until the bias voltage increases to the norm | (half of the signal amplitude), which is especially important when a signal appears after a pause, when the voltage on C cm is already discharged It was possible that O would cause a positive predominance of the first sign of the signal, since, in the absence of a moderator, the voltage of the signal could open the restrictive lamp at the moment of its occurrence, i.e., starting from a fusion base, which is graphically shown in FIG. 3 drawings.

FIG. 4 of the drawing shows the same case, but with a retarder in the circuit.

The subject matter of the invention.

A device for receiving telegraph signals with a limiter, characterized in that, in order to convert a rounded waveform to a rectangular signal, a delay filter is included in the straightened signal voltage circuit, the decelerating signal is straightened by the time required for the increase of the bias voltage to required value after a long pause.