I don't think the line amp was a bad idea because it did give you decent signal quality, but I still don't understand the problem. Go back and read the first post; there was some kind of interaction between the receivers that is not explained by just a bad amp.

You changed LNBs, so that is not likely the problem. I am stumped.

You still have a problem because a signal at 60 is likely to freeze, and bad weather will lower the signal even more.

The interaction you described is gone?

Did you ever just swap the location of the Sony and the Philips receiver? Remind me -- what happened with/to the problem?

Especially confusing is that the problem only occurred when someone was watching the Philips for a while, because the voltages on a satellite receiver are always going up to the LNB, whether it is on or off, watched or not! That is why I thought there might be some interaction between halves of the LNB.

But if removing the amp TOTALLY resolves symptoms, then the LNB is good and I am out of answers. Maybe you could put the amp back in place, but with a 3 to 6 dB satellite attenuator between it and the dish? This is a wild stab at getting the signal level back up but avoiding the problem.

Maybe it is worth calling DirecTV for some service, because 100 feet of wire should not drop the signal to 60 on any transponder. I don't know what they charge, but if it is a single charge to fix the problem no matter what, they will have to run it to ground and SOLVE it!