A regenerative SW receiver with automatic regeneration control

Posted on Feb 6, 2014

This is the tuned radio frequency receiver for shortwave (25 meter band, 11. 7. 12. 1 MHz). It was created as experimental design for further experiments with the autodyne synchronous receiver (see Polyakov V. T. Autodyne synchronous regenerative receiver. - Radio, 1994, N 3, page. 10. ). The circuit diagram is shown in Figure 1. The input resonant t

A regenerative SW receiver with automatic regeneration control
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ank composed of the loop antenna WA1 and capacitors C6 (the trimmer capacitor), C7 (the variable capacitor), C8 and C9. The resonant tank circuit has very high quality factor Q within the working band (11. 7. 12. 1 MHz), so the effective height of the loop antenna can be up to several tens of meters. An antenna with this parameters can receive very weak signals. The sensitivity of this shortwave receiver is limited by the noise of the transistor VT1, so it would be better to use in the first stage a low-noise RF transistor. The automatic regeneration control circuit includes the second stage of HF amplifier (the transistor VT2) and the diode based detector (C11, VD1, VD2, C13). The resistors R1, R2 and R6 provide a bias current for diodes VD1, VD2 and for the transistor VT1. From the output of the detector the DC signal corrects the regeneration of the regenerative stage, the AC component of signal goes through the capacitor C12 to the one-stage audio amplifier based on the transistor VT3. The headphones BF1 is the load of this audio amplifier. The resistance of the headphones is about 1600. 3200 ohms. The output power of the audio amplifier is about 1 milliwatt. The resistor R4 provides a feedback biasing for the transistor VT2, and the resistor R9 does the same for the transistor VT3. Match the resistor R4 to get the voltage across the collector of the transistor VT2 equals to half of the supply voltage. The coil of the...

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