60_TO_72_MHz_VIDEO_AND_SOUND_RECEIVER_AND_IF_SYSTEM

Published:2009/7/17 3:34:00 Author:Jessie | From:SeekIC

This IF system uses a NE602 oscillator/mixer to convert VHF TV signals of 60 to 72 MHz (channe13 or channel4 under the U.S. NTSC) to 45 MHz. An SAW filter is used to provide bandpass filtering, followed by an LM1823 video IF/AGC/AFC/detector IC. Recovered video is fed to a sound trap and 4.5-MHz sound takeoff filter. Video is fed to the output emitter follower and is up to 1.5 V p-p into 75 Ω. An MC1357P FM IF/limiter/quadrature detector recovers audio information and provides 0.5 V p-p line-level audio. An LM555 oscillator and 1N914 diode act as a dc-to-dc converter system to derive a negative 3-V supply for the LM1823 AGC system. Both AFC and AGC voltages are available for interfacing with external down converters used for 440, 915, and 1280 MHz amateur TV reception. Operation is from a 12-V supply at about 200 mA. A complete kit of parts, including PC board, is available from North Country Radio, P.O. Box 53, Wykagyl Station, New Rochelle, NY 10804-0053A.



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