HF regenerator. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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As it became known from the article "The last of the Mohicans ...", summarizing some publications of the foreign press ("Radio", 1997, No. 4, pp. 20, 21), recently there has been renewed interest in regenerative radio receivers designed to operate in the short wave range.

This attraction to the old reception method is easy to understand by comparing the capabilities of the regenerator and the modern super heterodyne receiver. Given the high, consistent "super" gain provided by the complex, multi-element stages, the operator can only "twist" the tuning knob. The remote, barely audible station "caught" by him at the same time is by no means his achievement, but the high possibility of the equipment itself.

Another thing is a simple regenerator, where high sensitivity and selectivity, and, consequently, the effectiveness of reception, are a consequence of the operator's skill in controlling adjustable feedback. Only the reception of weak signals on the HF regenerator will bring real sports satisfaction: the simpler the technical equipment, the more valuable the “find” on the air. In addition, the significantly lower level of self-noise in comparison with the "super" makes weak signals more intelligible.

Fascinating trips "on short waves" can be made even with the help of a simple regenerative radio receiver, assembled according to the diagram shown in the figure. It contains only one oscillatory circuit, consisting of an inductor L2 and a variable capacitor C4 - this greatly simplifies the design. The receiver has one survey range - 19 ... 60 m, but if desired, the received frequency band can be changed by increasing or decreasing the number of turns of the L2 coil. Continuous tuning allows multiple amateur radio stations to be received between broadcast subbands.

(click to enlarge)

To improve the stability of the regenerative cascade and reduce its radiation into the antenna, an RF amplifier made on the transistor VT1 was introduced into the receiver. The radio signals received by the WA1 antenna are fed through the capacitor C1 to the input of the amplifier stage. The collector load of the cascade is active-inductive (resistor R2, inductor L1).

The signal selected by the oscillatory circuit L2C4 is fed through the coupling coil L4 and the capacitor C6 to the regenerative detector, made on the transistor VT2. High sensitivity is provided by positive feedback through the coil L3, included in the collector circuit of the detector transistor. The feedback is regulated by a variable resistor R6, which changes the current in the base circuit of the transistor VT2.

The 3H signal, isolated by the detector, is fed to a two-stage amplifier (transistors VT3, VT4) of audio frequencies. Variable resistor R8 adjust the volume of the sound reproduced by headphones BF1.

Coils L2-L4 are wound on a polystyrene frame with a diameter of 6 mm, equipped with a ferrite trimmer 100НН. Coil L2 contains 15 turns, L3 - 4 ... 8, L4 - 3 turns of wire PEV-1 0,31, and coils L3 and L4 are located at the end of the frame near the screw-in trimmer. The inductor L1 has 70 turns of PELSHO 0,1 wire, wound in one layer on a resistor VS-0,5 with a resistance of several kilo-ohms.

Fixed resistors - MLT-0,125, variables - SPO-0,4. Variable capacitor - two-section, with a maximum capacitance of each section of 240 ... 270 pF, the sections are connected in parallel. Oxide capacitors - K50-6, the rest - KT, KLS and others. Headphones - high-resistance, for example TON-2M. Power source - 8...10 V battery or mains adapter with good output voltage filtering. The antenna can be a wire in insulation 5 ... 8 m long, for example, stretched along the wall of the room.

Establishing the receiver comes down to setting the collector currents of the transistors VT1, VT3, VT4, equal to 1, respectively; 1,5 and 3 mA, selection of resistors R1, R9, R11. The engine of the resistor R8 must be put in the upper position according to the diagram.

To ensure smoother tuning at the radio station, it is desirable to provide a vernier device for a variable capacitor.

To eliminate non-linear distortion at low sound volume, it is recommended to turn on the variable resistor R8 according to the "classic" scheme: connect the engine to the base of the transistor VT3 through a capacitor with a capacity of 1 ... circuit output resistor R5.

Author: Yu.Prokoptsev, Moscow

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