"Owen" wrote in message
...
On Wed, 6 Jul 2005 20:06:13 -0400, "Walter Maxwell"
wrote:


As I understand it, Owen, a line has to be lossless for Xo to be 0, while
distortionless lines have loss but have equal series R and shunt G. All

Walt, I learnt that a distortionless line is one where attenuation and
phase velocity are constant for all frequencies, and that requires
that R/XL=G/XC in the RLGC model of a lines characteristics, and the
result is that Zo is purely real.

A lossless line is a special case of a distortionless line.

lines that I've measured have a small negative X, that would be zero if
the
line were lossless. So I'd have to say that the material in Appendix is
is
correct for standard lines. Distortionless lines are normally found only
in
long-distance phone lines used at voice frequencies, not RF. Or am I
missing
something?

If you like, I am saying your approach is valid for lossless lines, it
is also valid for all distortionless lines, but I think it is not
accurate for lines in the general case because it isn't correct if
Xo!=0.

Owen

Owen, if X = 0 there is no attenuation, but you're saying my material is
invalid if X is not 0? I'm sorry, but I'm confused.

Walt, W2DU