Hi Mark and Amsat,
Just wanted to report that I heard AO51 come over nicely this morning (2011-01-06 at around 1420z). I put out a quick call, nice audio on downlink, and heard Loren K7CWQ come back. On my return to him, the bird suddenly disappeared about 10 seconds in .... Loren replied, it cut off on him after about 5 seconds ... and on my repeat reply, it cut off after about 3 seconds. Didn't hear it again on that pass. Sounded just like someone trying to transmit with an HT on low batteries! :-)
A quick check showed AO51 was barely in eclipse (screenshot from my SatPC32 below):
http://3.bp.blogspot.com/_JEsfS-puDmk/TSXUKQFKhEI/AAAAAAAAATc/bsapXtrj1cM/s1...
So this sounds exactly like the behavior Mark was describing AO51 would do. Even though the bird was heard at first, I flagged it as "not heard" on the oscar.dcarr.org page just to note that it dropped off early during the QSO.
73 all!
Dave KB5WIA / CM88