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

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