Radio receiver on two transistors. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Radio receiver on two transistors. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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In one of the popular radio engineering magazines about twenty years ago, I saw a description of a simple direct amplification receiver based on germanium transistors. I decided to replace the transistors with more modern ones. I picked up their operating modes - and got a good receiver (see picture).

Radio receiver on two transistors

Selected by the oscillatory circuit L1C2 of the magnetic antenna WA1, the signal of the radio station enters through the coupling coil L2 to the radio frequency amplification stage, made on the transistor VT1. From the load of the cascade (resistor R2), the signal follows the detector, assembled on diodes VD1, VD2. From the load of the detector (resistor R3), the audio frequency signal is fed through the capacitor C5 to the AF amplifier, assembled on the transistor VT2. The load of the amplifier is a miniature headphone BF1 type TM-5 with a voice coil with a resistance of 210 ohms.

The receiver is powered by one disk battery, but it is permissible to use a galvanic cell. The supply voltage is supplied by the switch SA1.

Transistors - any of the KT315 series, but with a possibly large base current transfer coefficient, diodes - any of the D9 series. Trimmer capacitor C2 - KPK-2, oxide C5 - K53-1A, K53-4A or another small-sized capacitance indicated on the diagram, the rest of the capacitors are of any type, possibly smaller. Resistors - MLT-0,125. Power switch - any small-sized.

The magnetic antenna is wound on a rod with a diameter of 8 and a length of 60 mm made of ferrite 400NN or 600NN. The loop coil L1 is placed on a paper frame 30 mm wide, it contains 70 turns of PEL or PEV wire with a diameter of 0.14 mm. The communication coil L2 is wound on a movable frame 8 ... 10 mm wide and contains 15 turns of the same wire as the contour one. With these parameters of the magnetic antenna, the receiver operates in the MW range. If necessary, transfer it to the DV range, you need to increase the number of turns of the contour coil (and sometimes the communication coil).

The receiver practically does not need to be adjusted. But to obtain greater sensitivity and sound volume, it is desirable to more accurately select the resistors R1 and R4. For the same purposes, it is recommended to use an external antenna in the form of a piece of wire 1 ... 1.5 m long, plugged into the XS1 socket. and ground connected to a common wire.

Author: V.Bobkov, Novosibirsk

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Comments on the article:

Denis
Good afternoon. I'm looking for an encyclopedia. The size is large, the cover is black in the book, mainly about technology. The scheme is presumably from this book. If you know the title of the book and the publisher please let me know.

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