Synchrodyne. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / radio reception
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Below is a brief description and schematic diagram of a receiver designed to operate on the 80 m amateur band. However, with the appropriate data of the inductors, it can also be used for reception on other bands.
The synchronous dyne principle of operation is based on the joint operation of a synchronous detector and a balanced mixer. As you know, a synchronous detector is a frequency conversion device, to the input of which two high-frequency signals of the same frequency are fed. One of them is a purely sinusoidal oscillation, the other is modulated. At the output of the device, a low-frequency voltage is obtained, with which the second high-frequency signal was modulated.
A balanced mixer is a frequency conversion device, from the output of which the IF voltage can be removed without the use of selective circuits.
Synchronization works in the following way. The signal voltage taken from the input circuit L2C1 is supplied in phase to the input of a balanced mixer assembled on transistors T1, T2. The local oscillator voltage taken from the secondary winding L4, L5 of the local oscillator circuit is supplied in antiphase to the emitter circuits of transistors T1 and T2 (to the other input of the balanced mixer). As a result of the conversion, at the output of the balanced mixer, among other components, two intermediate frequencies will appear, differing from one another by a double modulation frequency.
To detect and extract the envelope of the low-frequency signal, a synchronous detector is required, assembled on transistors T3 and T4. RF signals with the same intermediate frequency are fed into the base circuits of transistors,
connected one according to the scheme with a common collector and the other according to the scheme with a common emitter, and interconnected by alternating current. Thus, the addition of the selected low-frequency component is achieved, while the high-frequency components cancel each other out. From the load of the synchronous low-frequency detector resistor R12, the signal is fed to the low-frequency amplifier.
The input circuit coil L2 is wound on a ferrite rod with a diameter of 8 mm with a PELSHO 0,15 wire. The number of turns is 60 with a branch from the 6th turn. The antenna coupling coil has 6 turns of the same wire. The coil of the L3 heterodyne circuit (the number of turns is 40) is wound on a frame with a diameter of 8 mm with a ferrite tuning rod with a PEL wire of 0,25, coils L4, L5 each have 6 turns of the same wire.
In the synchronous dyne stages, domestic transistors P403, P423 can be used, while changing the polarity of the supply voltage and electrolytic capacitors to the opposite.
Literature
- "Amaterke Radio", 1967, No. 7, 1969, No. 5.
- Radio, No. 2 1970 c.60
Publication: N. Bolshakov, rf.atnn.ru
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