Owen,

Your formula is too short to be anything but an approximation. It may
be a very good approximation. On the other hand it may contain
exactly the same errors as whatever you may have checked it against.

The exact formula is exceedingly involved and occupies about half a
dozen lines of source code in new program SWRARGUE which by
coincidence I have just placed in my website.

You can check your formula against my program. Let us know how you get
on.
----
Reg, G4FGQ

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"Owen" wrote in message
...

Apparently, Michaels described in "Technical Correspondence" in QST
NOV 1997 a method for calculating loss on a mismatched line.

I don't have the article, and haven't been able to find it on the
net,
so I am working from references to it that I have seen, mainly in
Usenet.

Apparently, the method involves calculation of a factor (let's call
it
MR) as MR=|(Zl-Zo*)/(Zl+Zo)|, and the line loss between two points
is
given by 10*log((1-MR1**2)/(1-MR2**2)) where MR1 and MR2 are the
values for MR at points 1 and 2.

I have compared the results of this on lines with Xo0 and high
VSWR,
and the results are identical to calcuating the loss by subtraction
of
Real(VI*) at point 1 from Real(VI*) at point 2.

Has anyone a link to, or a reference to the derivation of the
formula?

Owen
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