"Owen" wrote in message
...
On Wed, 6 Jul 2005 21:23:52 -0400, "Walter Maxwell"
wrote:


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, I don't think that Xo=0 implies zero attenuation, but it is true
that if the line has zero attenuation that Xo=0.

I think the method in your appendix is true when Xo=0, and an
approximation where Xo!=0.

I have just added a function (DLoss) to calculate loss as per your
appendix to the graphic at http://www.vk1od.net/temp/LineLoss.htm ,
and it can be seen that in this (perhaps extreme) case, it is not a
very good approximation.

I also added the same calcs for f=100MHz and Zo is much closer to
real, and it can be seen the approximation is much closer.

Owen

I'll have to study your math, Owen, to let it sink in. I don't get it on the
first glance.

Walt