Jim Lux wrote in
:

....
Try changing the resistivity by a factor of 2 or 10 and see if the
model results change significantly. It might be a non-issue.


Thanks Jim, I did such an analysis and should have posted the results.

The majority of loss is in the interior of the transmission line as
posted. If I change the conductivity of the segments used by the coil,
total conductor loss halves, so it seems signficant.

I am thinking that with proximity effect likely to confine current
distribution to perhaps one fifth of the shield circumference, and
effects of braid on RF resistance, the effective RF resistance of the
outside of the shield might be five times or so the resistance of a
copper tube of same diameter.

I assume that NEC will not be modelling proximity effect, but I could be
wrong.

Do you have any suggestions?

Owen