Refinement of the DFT in the RA3AO transceiver. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Civil radio communications
Comments on the article
1. DFT coils fabricated according to the description [1] on the core of the PK150-7-11 cable did not give the desired frequency response, it turned out to be impossible to improve it by moving the turns.
It helped to change the design of the coils (Fig. 1, 2) to the movable sections L1 and L3, which ensured the desired connection and, accordingly, the required frequency response.
Material: - coil - fluoroplast, plexiglass. Axis - plexiglass, textolite, glass-testolite.
Coils L1, L2, L3 are put on the axis with friction, preload 0,01 ... 0,02 mm., for fluoroplastic and is selected empirically for another material.
2. To reduce the "scattered" inductive coupling created by rather long coil leads, and transform it into a capacitive one, it is necessary to twist the leads of all coils together, ensuring the marking of the beginning and end of the coils (Fig. 3).
The pins twisted together have a small capacitance (about 1 pF) and do not affect the setting.
Literature:
1. Drozdov V. Amateur KB transceivers. M., Radio and communication, 1988, p. 113, fig.41.
Author: A. Buzherya (UA9NM); Publication: N. Bolshakov, rf.atnn.ru
See other articles Section Civil radio communications.
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