[snip all the stuff i wrote about ah-4/icom 706 problem]

problem solved. the ground for the ah-4 wasn't good enough, so i moved
it to a thicker cable and ran it directly to the chassis instead of
going the extra 12 inches to the shared ground that went directly to
the chassis. i was worried about ground loops, and still am, but it's
working much better with a fat 2 inch wide braided strap going to the
chassis.

but that didn't fix it completely ... the final answer was to put
ferrite beads on each end of the control cable that goes between the
remote display and the radio itself. the control cable was picking up
rf from the tuner and that was making the radio cut off, the beads
fixed it.

so thanks everyone for all your help (**snickers** nobody even answered
my post!)