AF_LOW_PASS_FOR_CW

Published:2009/7/3 2:20:00 Author:May | From:SeekIC

Design using 10% tolerance components gives sufficiently wide bandwidth while maintaining steep skirt re sponse for CW reception in direct-conversion communication receiver. Filter has five identical three-transistor sections, each peaked at cutoff frequency. a of each section is about 1.9, which gives 6-dB bandwidth of about 200 Hz. With center frequency at 540 Hz attenuation is 75 dB at 1200 Hz. Net gain of system is 28 dB at resonance. NPN transistors are 2N3565,2N3904, or similar; PNP transistors are 2N3638, 2N3906, or similar.-W. Howard, Simple Active Filters for Direct-Conversion Receivers, Ham Radio, April 1974, p 12-15.



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