Several older publications mention an interesting way to pass Balanced Line Ladder Line Feed in through a building’s wall and near otherwise interfering objects using a Twin-Coax RG-8 Pair system.
Two lengths about 20 ft each of RG-8
Tape the two lengths solidly together, in the fashion of ladder line, with tape wrappings every 6 inches.
Outside end is cut back so the center conductor is free to solder to one side of the Ladder Line.
The evenly cut off outer-casing, braid shield, and dielectric are sealed against weather & water with Non Conductive caulk, tape or compound.
At the tuner end, again cut back so the center conductor is free to have a connecting lug soldered on.
In this case the outer-casing is cut back so both braids can be soldered together, and a ground strap soldered to the resulting shield.
The sources suggest grounding the shield to the antenna tuner’s ground lug (which you have already hooked station ground, right?).
Will be giving this a try working to fight some fairly rough station RFI issues at a friend’s shack.
Would very much appreciate hearing anyone else’s experiences doing a twin-coax balanced feed-line pass-through.