On Sun, 11 Dec 2005 15:29:20 -0700, Wes Stewart
wrote:


Importing their data into Dan's (AC6LA) "bestfit.xls" spreadsheet
shows very poor correlation with theoretical k1, k2 coefficients. I'm
observing something similar on some RG-142 that I am measuring with my
N2PK VNA. The '142 has a silver-coated, copper-plated steel center
conductor and I believe that the skin depth encompasses the steel at
lower frequencies.

I noted when I imported Davis' Bury Flex data to tllce that the
regression model correlation coefficient was lower at 0.9918 than most
other data which tends to come in better than 0.997 and mostly 0.998
or better.

One of the reasons that some lines show a very good fit to the model
(eg 5 nines) is that the measurement data was fitted to a model, and
the published figures are from the model, not the original
measurements, and the error in deriving a model from the published
figures is principally caused by rounding of the published figures.

A possible explanation of Greg's observation of low Zo is that the
foam is more dense than intended, increasing C, lowering Zo, and
increasing loss at higher frequencies.

Owen
--