Hi All: The OTA sensitivity of my AM21 and my tv's OTA tuner have always been quite comparable, even on the respective signal meters. Over the past two weeks or so, however, I think something has happened that has reduced the sensitivity of my AM21. If it makes any difference, I believe this happened before the June 12 DTV switch date, and none of these stations switched channel assignments or anything like that at the DTV switch date. I have an antenna going into an A-B switch box for switching between my tv and my AM21. On my three distant channels (at night), I'm getting signal strengths of 45, 55 and 88 on my tv's signal meter and all three stations come in fine using the tv's tuner. All three of these stations used to also come in on the AM21, with approximately the same signal strengths. Now, two of these three stations don't come in at all on the AM21, and the third station (that registers an 88 on my tv's meter) comes in at 40-43 on the AM21. I knew that the two tuners were quite comparable previously because the two weakest of these stations would always appear in the evening at exactly the same time on both my tv's tuner and the AM21, as signal strengths came up (meaning that both tuners had approximately the same reception threshold based on signal strength). To check for possible connection problems, I reversed the A-B switch, took the switch out of line, substituted the short coax going to the AM21, checked the cable going from the AM21 to my HR21, did a full reset followed by a new OTA setup, but couldn't trace any problems. This is an all-of-a-sudden performance drop for my AM21. Could something have happened to my AM21 (heat?) that would reduce its sensitivity? Thanks in advance for any comments.