Hi, all concerned:
Is this the balun problem?

40-meter half-wave dipole with trees and 3 dogbone insulators, center-fed
directly across the center insulator with 33 feet of
RG-59/U coax, nothing special.

The thing has voltage loops at all ends, including the shack-end of the
coax-braid, correct?

Well, it would seem to have voltage loops at each end of the dipole. If the
antenna feedpoint impedance is 75 ohms non reactive and the surge impedance of
the coax is 75 ohms, then you should see 75 ohms at the shack. No voltage loop.
Do you need a balun? I would think that if everything were perfectly
balanced, and you had a perfect 75 ohm match at the shack, then no balun
needed. A perfect match at the shack indicates no current on the outer braid
of the coax because of imbalance, or rf pickup. Everything is radiated at the
antenna. That is one of my goals, along with the direction of radiation.
If changing the length of coax changes the impedance at the shack, that
indicates feedline radiation.


73 Gary N4AST