Owen Duffy wrote:
Cecil, do you have theoretical or experimental support for the
inference that insulated vs uninsulated wire will be different in
length by around 3.5%? What thickness wire / insulation?

Owen, that info came from Roy, W7EL, who built it into the latest
version of EZNEC. It has to do with the VF of insulated wire Vs
uninsulated wire which affects wire antennas as well as transmission
lines.

I discovered it for myself when I was building vertical loop
antennas many years ago. The equation 1005/f wasn't even close
using insulated wire.

For instance, my 130 foot bare copper wire dipole is resonant at
3.633 MHz according to EZNEC. Adding 0.05 inch of PE insulation
drops the resonant frequency to 3.526 MHz, about a 3% drop
according to EZNEC.
--
73, Cecil http://www.qsl.net/w5dxp