If aiming isn't the problem (a friend and a pair of walkie-talkies is a great asset), and it's not the cable, then it has to be equipment.

There's the LNB, the tuner, and the TV. Since the tuner's signal-strength meter is indicating a varying signal, that leaves out the TV.

You've replaced the LNB with no difference. I'd recommend taking another tuner. That's all that's left, but my bet is still with the cable.

Larry