There must be NO metal and NO low-grade insulating material BETWEEN the pair
of wires as they come into the shack.

Bring the wires close together for a short distance through a relatively
small hole in the wall. At HF, the small lumped increase in capacitance
between the wires will have a neglible effect on system operation.
Equivalent to an unoticeable minor shift in tuner settings. No additional
line loss will be incurred.

Insulate the pair of wires from each other by using the inner conductors of
coax cable plus the polyethylene. Discard the outer conductor braid. To
minimise size of hole through the wall allow the polyethylene coverings to
touch each other if you like.

The main problem will be rain and weather-proofing.

For a short, indoors, distance to the transmitter or tuner, the twin
polyethylene insulated wires can be retained and allowed to separate if
convenient.
---
Reg, G4FGQ

====================================

"me" wrote -
After many years of experimenting with coax fed wire antennas I am
taking my first plunge at open wire line.

To get into shack, I need to go through exterior steel siding,
exterior wood siding & plywood, a layer of insulation, then interior
sheetrock and wood paneling. Assume I need about 4-6" of safe
feedthrough so that standoffs can be mounted on the walls oustide
and inside the shack.

I generally run 100 to 1500W output...at full legal limit probably
3KV on the feedline...am not crazy about the idea of setting my house
on fire due to HV arc over.

Am looking for the old style porcelain feedthrough isnulators, but so
far have not found same.

Local Home Depot has thin PVC tubing (as in sink/toilet stems), vinyl
tubing, welding rod tubes, etc. What are the dielectric properties of
these, and the high voltage breakdown voltage...???

Seems like glass, porcelain, or ceramic tubing would be best
feedthrough insulator, but where to find?

Are any modern day materials found in Lowes or Home Depot safe from
arcing and also efficient for RF?

Thanks in davance & 73,

Dan (K0DAN)