I must be an idiot.
My whole house audio, video, LAN etc distribution was self installed a few years ago. I have security cameras at the front and rear of the house and they are fed into the system with a three channel modulator at channels 93, and 95. I also have a third custom channel that adds my home theater PC's video to the cable distribution so I can watch the HTPC video at any TV in the house that was hooked up to the cable.
Because of that I took pains to insure that those signals did not propagate back out to the street and cause interference to neighbors. I only had analog cable service and didn't need any channel above 90 that was coming down the cable. So a low pass filter was installed to block my 90s channels from going back out to the street.
I'm embarrassed as hell that I forgot about that. Especially since I did all the work myself. My only excuse is I'm getting too old to remember back that far.
Any way, it was easily fixed by changing the first splitter off the input from the street from a two way to a three way and then using the unfiltered third feed to drive the Clear QAM capable tuner. (It's three way to feed my cable modem, normal cable TV and finally the new dedicated line for the new tuner) Whew !
What got me heading in the wrong direction was that Cox was telling me all along that they do NOT broadcast clear QAM signals in CT. This is false and their tech supervisors need some more training. I am now getting about 20 - 25 Clear QAM channels including all the locals. They (Cox service) obviously don't have a clue about what they actually transmit.
I post this in the odd chance it might help someone else in a similar situation. Yeah, I'm an idiot for not looking at the obvious.
But then at least now I'm a happy idiot !!