Just thought I'd post this for anyone else having a similar problem with their Tivo HD, and possibly other Tivos?? exhibiting intermittent breakups using a antenna.
Over the years I've had issues with a couple of channels occasionally breaking up, once every couple of hours to occasionally several times/minute. It really only happens on a couple of channels and at one time I thought it was related to leaves but it's winter now and no leaves yet I was still having the occasional problem.
I have an attic antenna which I know can be subject to multipath but none of my other devices(many TVs and several DVRs) sharing the same antenna seem to ever have the problem, not even a older('07) Sony HDTV right next to the Tivo. Over the years I've tried moving the antenna a few degrees(all I can do in the cramped attic) and I've tried various attenuators to varying degrees of success. I also tried using a indoor antenna with a backwards splitter combined with my attic antenna and again have had varying degrees of success. When I tried things it seemed to help for a bit but then I'd notice the breakups would come back.
I was reading another thread where they were talking about FM traps and decided to give it a try. I didn't have a FM filter but did have all 75 ohm FM tap, antenna in FM out and TV out. I tried this inline with my Tivo HD with a terminating resistor on the FM out and low and behold several weeks later not a breakup on any channels, it's been perfect!
It seems to me my Tivo must be prone to FM overload which caused the TV breakup. I'm about 15 miles from my cities antenna farm where everything comes from so it's not like I have a tower in my back yard but for whatever reason FM seems to be effecting my Tivo. My Tivos signal strengths are generally in the upper 80s to mid 90s.
This post is just more a FYI for anyone else having a similar problem with their Tivo HD, try a FM filter, it just may work for you