A simple HF mini transceiver. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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A simple HF mini transceiver. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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To assemble a simple HF minitransceiver, you will need only three 2N2222 transistors (analogue - KT315) and one LM386 chip (K157UD1 can be used). In the diagram (Fig. 1), T1 operates as a generator, T2 as a mixer (in receive mode) and UHF (in transmission).

(click to enlarge)

When the telegraph key is pressed, the emitter and base T2 are connected by direct current to a common wire, when pressed, a quiescent current flows through the transistor and the emitter is the output of the mixer. T3 works as a low-frequency preamplifier, because. LM386 alone does not provide enough amplification. The transceiver can operate in different ranges, for this it is necessary to have the appropriate quartz, as well as the inductance and capacitors of the P-loop (Table 1).

Range, m	Capacity, pF	Inductance,µH
20	270	0,72
30	330	0,98
40	470	1,28
80	750	5,78

At 80 meters, 3,579 MHz quartz from an NTSC television decoder was used. The transceiver has an output power of 200 mW. To ensure the frequency separation between reception and transmission of about 1 kHz, an additional 1000 pF capacitor can be connected in transmission mode in parallel with the trimmer in the quartz circuit (Fig. 2).

Simple HF Mini Transceiver
Ris.2

The same figure shows an option to turn on the attenuator in the receive mode to improve the dynamic characteristics of the receiver. Figure 3 shows the drawing of the printed circuit board and the location of the elements on it.

Author: Radovan Vlasilik OM2ZZ; Publication: N. Bolshakov, rf.atnn.ru

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