Fixed! (I hope.)
I mounted the 7084 antenna today and it has many of the appearances of working, with the AP4700 amplifier in place. The weak channels are all coming in.
We'll know in a few months, when the weather changes grossly, if I have to shift the direction again. If so, then I think I have to do some major work to supply power and controls wires to put on antenna rotor.
It's much bigger than the old CA7078, so I have my fears about our high winds twisting it around.
Winegard.com is now available online, unlike a week ago. After much troubleshooting, it turns out my router went bad, so I put in a new one which seems to have solved the problem. Very odd form of failure.
Thanks, all, for your help. i couldn't have done it without you.