On Mon, 29 Nov 2004 15:14:42 -0800, Roy Lewallen
wrote:
Once again, it's not clear to me just what you're trying to prove.

Hi Roy,

Troubles me too....

In the interim I have recognized where I went off the deep end in the
thread I have alluded to. The attempt there was to reproduce, in
EZNEC, results obtained at the bench and offered through various
references which demonstrate Mismatch Uncertainty. Although the model
of the transmission line was certainly of the highest quality, EZNEC
lacks the capacity to separate forward and reverse waves for analysis.
In that regard I mistakenly attributed the results I obtained to my
bench results.

Situation is that with a SWR meter moving along a line mismatched at
both ends, there is a distinct variation in the computed Power. When
I did this at the bench, I could evidence about a 30% variation which
was consistent with theory and clearly exhibits the contribution of
Source Z when it is other than 50 Ohms. When I recently attempted to
model this in EZNEC, I again saw the wild fluctuation of power that
seduced me with its complementary results into thinking I had achieved
the same results. When I revisited those results (EZNEC ones that
is), all I had done was prove the mismatch through the abstraction of
the power reported at my moving test load. When I reverse engineered
the voltages from the known R, it became obvious that the VSWR
corresponded to every expectation - or was close enough given the
degree of resolution I had available with 20 test points distributed
along the line. Chipman describes this in his late chapters - one of
which Wes has provided.

However, this does nothing to detract from Chipman's work that
includes the FULL treatment of all variables that lead to the common
usages. Such treatments include the Source with full
characterizations and goes on to discuss the R of the Source and not
just its Z. That so many texts disregard this level of examination
does not deny its importance to issues that go beyond SWR. Those
lesser texts presume Source Z unlike Chipman, and its significance is
lost to the student who hasn't been grounded in the fundamentals. And
thus we arrive at the topic at hand and listed in the Subject Line:
Additional Line Losses Due to SWR. In that regard, the Source Z is
entirely an active player and any additional mismatch that it presents
to the system eventually finds additional loss (caloric) injected into
it. Chipman's work in that regard is complete enough to offer Bob the
framework to render a complete solution and to explain how and why
this additional loss appears. It may not bear on his measurements
directly (the measure of a stub's Q as it eventually turns out), but
it is related closely enough to provide tangible leads.

73's
Richard Clark, KB7QHC