Direct conversion receiver 1. Diagram, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Direct conversion receiver. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / radio reception

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Recently, "short-wave direct conversion receivers" have become widespread. The figure shows a schematic diagram of one of these receivers, designed to operate in the 3.5 MHz band. An ohm consists of a high-frequency amplifier, a balanced mixer, a low-pass filter and a low-pass amplifier.

(click to enlarge)

The RF amplifier is made on a field-effect transistor T1. Its load is the LIC3 circuit. From a symmetrical coil L3, the signal is fed to a balanced mixer, consisting of diodes D3, D4 and a tuning resistor R3. Filters are included at the output of the balanced mixer.

On the field-effect transistor T3, a master oscillator of the local oscillator is made (according to the capacitive three-point scheme). A buffer stage (transistor T2) is connected between the master oscillator and the mixer. The supply voltage of the local oscillator is stabilized.

The low frequency amplifier is made on transistors T4 - TS. You can connect high-impedance headphones to its output.

On transistors T7 and T8 (of different structures), the final stage of the amplifier is made. It is necessary when using low-impedance headphones or a direct-radiating driver with a voice coil impedance of 8-30 ohms.

The receiver is mounted in a metal case measuring 105X90X50 mm. Coils L1, L2 and L3 are wound on frames with a diameter of 9.5 mm. and chokes Dr1 and Dr2 - on ferrite ring cores with a diameter of 10 mm. In the manufacture of coils L1 and L2, 40 turns of PEV 0.31 wire are first wound (turn to turn; coil L1). A layer of PEV 0,23 wire is wound over this layer (wound in two wires; coil L2). Coil L3 contains 40 turns of PEV 0.31 wire (turn to turn is wound).

Choke inductance Dr1 - 1 mH, Dr2 - 60 mH.

Editorial note. The receiver can use transistors KP303 (T1, T3). KT315 (T2, T6, T7). KT342 (T4, T5), KT361 (T8), diodes KD512A (D1. D2). KD503A (D3, D4). D101 (D5, D6), Zener diode KS156A (D7).

Literature

"Radio communication" (England), 1975, No. 2
Radio No. 7, 1975

Publication: N. Bolshakov, rf.atnn.ru

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