JBL_1, it's great to hear from someone involved with those sets.
The wideband IC demods were discussed in at least a couple a couple of threads here:
http://www.videokarma.org/showthread...ideband&page=2
See post #19 where I gave a quick explanation the single ended delay line, which, IMO, is
one of the cleverest inventions in analog video IC design I have ever seen.
http://www.videokarma.org/showthread...nd#post2434742
See post #132, where I talked about my analysis of a sample RCA set with the wideband circuit while I was working at Zenith. Basically, it looked like the IF couldn't support the increased bandwidth without quadrature distortion, and the high-frequency I gain seemed to be turned down to prevent visible edge effects.