Thanks for the response Bob.
I found the problems, and here are the solutions (for the record):
- My system had a ground isolator, which was the common denominator not checked previously. Removing the Ground Isolator cleaned up the cable signal, but brought a hum back into my preamp. It appears that the ground isolator turned the subsequent cabling into an antenna -- only the local channels had the noise.
- To remove the hum from the preamp, I found the ground bond on the outlet bank to be faulty. Refurbishing this ground connection lowered the noise floor. Additional troubleshooting found much oxidation on the house main ground on water pipe and also at the ground rod for the cable. I was able to see about 400mV of noise traveling on the ground with an Oscope. Installation of a new water pipe ground connection, grounding rod and clamp for the cable system caused the entire ground system to have no detectable noise with the an Oscope measurement.
After a test of all channels on the HT, the picture on all household TVs are perfect (better than they were before). The audio is also improved due to the lower noise floor, increased dynamics, and more subtle detail which is now present.
I guess the devil is in the detail, and this problem has continued to grow over a period of time, changing with weather conditions and other factors I had not been able to quantify. Now it all makes sense. I had reached my frustration point after 20hrs of weekend troubleshooting.