I don't think an amp is going to help. DirecTV is a digital signal, and you should either get it or not. There should be no shadowing or fading because those are analog concepts that should not be applicable to your signal. When your signal degrades it should jump in an out, you should lose the whole thing. An 80 signal strength is the strength at your box, not on the antenna, so you should be fine. I think the problem is in your tv or in the cable from your box to the pioneer to the tv. Of course you could prove me wrong by getting better results with an amp but I doubt that you will (but of course those radio shack amps are returnable).