Detector according to an unusual scheme. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Detector according to an unusual scheme. 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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A microcircuit will get to a radio amateur - an assembly of low-current diodes, and he is at a loss - what would it be adapted to? Diodes would be more powerful for a rectifier bridge, but these? Let's tell you - such an assembly can play the role of ... a transformer in a pocket receiver, if you assemble the detector according to an unusual scheme with multiple voltage multiplication (Fig. 1).

Detector according to an unusual scheme
Fig. 1

The signal level at the output of such a diode-capacitive multiplier is noticeably higher than that of conventional one- and two-half-wave diode detectors. In addition, due to the greater input impedance, such a detector slightly loads the previous cascades of the RF amplifier and significantly improves selectivity. This is especially valuable for simple direct gain single-loop receivers. If in local conditions there is no need to increase the selectivity of reception, it is possible to significantly increase the number of turns of the coupling coil with the antenna circuit; a concomitant increase in the signal applied to the URF will in some cases reduce the number of amplifier stages. For better matching with such a detector, the first stage of the ultrasonic frequency converter should be made with an increased input impedance.

Those who would like to experiment with an unusual type of detector can assemble a simple radio receiver as shown in Figure 2.

Detector according to an unusual scheme
Fig. 2

Mounted in a small flat box, it can be your good companion. Let's talk briefly about the scheme. Transistor VT1 operates in the radio frequency amplification stage, allocated by the circuit LI, C1. Diode assembly DA1 together with capacitors C3-C6 forms a 4-stage multiplier. In the audio frequency amplifier, the first stage on the transistor VT2 provides an increased output impedance, VT3 - output, loaded with a BF1 phone. Three D-1 disk batteries or two or three elements 0,1 can serve as a power source for CD316.

Magnetic antenna rod made of ferrite grade 400NN or 600NN, 80-100 mm long. The coils are wound with PELSHO-0,2 wire, the number of turns is L1-70, L2-7. Fixed resistors of the MLT type - 0,125, radio frequency capacitors - KPM, KLS; oxide - K53-1. For tuning, it is better to use a miniature single-section KPI, but you can get by with a trimming ceramic KPK-2 with a maximum capacitance of 100-150 pF. Miniature telephone type TM-2, TM-4.

While experimenting with the detector, investigate the effect of the capacitance value of capacitors C3-C6 on the reception efficiency.

Author: Yu.Georgiev

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