Coax for radio is routed as from factory (DG). I haven't touched any of
this wiring. It doesn't look to be routed parallel to anything except
TE and volume flask tubing.

The problem seems very sensitive to the routing and type of wire used
on the power lead to the vario (shielded worse). I put a ferrite core
on this lead and it significantly reduced the problem, but it still
exists as compared to running the b40 off of the battery with external
no power leads attached.