I was wondering myself, oxidation, etc. I went up to the attic this morning, and took my little test rig consisting of the Digital Stream converter box and a small video monitor. I came directly off the antenna with a new transformer into the converter, bypassing the CM 7777 pre. All of the UHF Springfield stations were in the 50's, and KPBI 34 came in around 60. KNWA was wallowing around at the extreme low end of the scale, barely discernible. Of course there was no signal lock whatsoever. I then took a splitter and a DC block, and came off the output of the Channel Master pre, which raised all of the signal strengths across the board about 10-15 points, but barely moving KNWA's strength at all. These represent the same numbers I'm seeing downstairs with all my splitters, etc. in the rack. So unless the antenna itself has become a low pass filter above channel 34, I'm stumped. You had mentioned that there may a problem with adjacent channel interference, which makes sense because of KNWA's sudden disappearance after being the best signal of everyone for over a year and a half. I have two possible culprits in that channel range that TV Fool says reside nearby:
K54GH Analog, out of Green Forest, AR, at an ERP of 7.5 kw, 26.2 miles from me
and KNJD-LP, analog ch. 59, out of Branson at 10.5 kw, 11.7 miles from me.
I cannot receive these stations, and it looks like they have have been operational for some time, so I don't know if they could be the culprit behind my problems starting in June with KNWA's signal. I know there are some RF gurus lurking around here, so does anyone have any thoughts on the culprit? I've resigned myself to giving up on a remedy, but I thought it might be interesting to hear some suggestions.