Skin effect can, of course, be easily calculated if the conductor
diameter is at least several skin depths. If you can't make that
assumption, the calculation is much more involved, but not difficult for
a computer, involving modified Bessel functions.

There's a graph of a proximity effect factor in Johnson & Graham,
_High-Speed Signal Propagation: Advanced Black Magic_, p. 43. The
caption says it's derived from Terman's _Radio Engineer's Handbook_
(1943), p. 43. An approximate equation for calculating proximity effect
appears on p. 8-51 of Kaiser, _Electromagnetic Compatibility Handbook_
(CRC Press, 2005). It's a bit involved to try and duplicate in ASCII.

Roy Lewallen, W7EL

Owen Duffy wrote:
Can anyone point me to information on calculating the effective resistance,
including proximity effect, of conductors in a two wire open transmission
line.

Owen