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Good Day gentlemen,
here is the GE DC restoration improvement info - see included document.
Personally, i use the NS (National Semiconductor) LM-1881 sync separator, Back Porch sampler IC for DC restoration - see included pdf.
The chip has a Burst/Back porch output, perfect for DC restoration processing.
I use this IC as French TV AM carrier modulated video uses positive modulation and many TVs sold here are lousily-adapted Euro B/G (Negative Video mod.) to French standards. Background brightness and video content contrast vary with program content: unacceptable!
Having a "BackPorch clamped" solid video reference is the only way to go for correct DC restoration, be it in B&W and more essentially for color.
If you don't want a scene where the headlights of a car at night turn "black/negative" instead of brilliantly illuminating the stage, something must be done. IC LM-1181 + some added circuitry, depending on the TV does the job.
The LM-1881 gives a stable true back porch sampled output and takes into its stride varying RF input signal intensity coming from the antenna/tuner/IF strip assembly.
Just to inform you of how complex the problem is, i learned the hard way that having a DC restored full Y/RGB chain wasn't enough: you also need to control the RF & IF AGC gain controls to keep video demodulation within the accepted signal level limits, but that is another story...
I hope this will help you,
Best Regards
jhalphen
Paris/France
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