Eliminate the intrusion of the transmitter's permanent PLL system. Scheme, description

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Elimination of the penetration of a constantly operating PLL system of the transmitter through parasitic connections into the receiver channel. 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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In "RL" N 4/91, p. 9, a scheme for finalizing the transceiver designed by V. Drozdov (RA3AO) was published.

This scheme is designed to eliminate the penetration of a constantly operating PLL system of the transmitter through parasitic connections into the receiver channel. The scheme satisfies its purpose, but also introduces an undesirable effect. Applying a QSK signal to pin 2 of DD1.2 introduces additional capacitance to the generator, which leads to its detuning when transmitting at 200 ... 250 Hz. This leads to a mismatch between the receive and transmit frequencies.

I propose another scheme (Fig. 1) for improving the generator, which allows you to get rid of this effect. All designations of the elements correspond to the PCB3CH board.

Elimination of the penetration of a constantly operating PLL system of the transmitter through parasitic connections into the receiver channel

Author: S. Chizhikov (UA0JL); Publication: N. Bolshakov, rf.atnn.ru

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