Dr. Slick wrote:
As you might know, the input S11 or SWR will change when you go
from an antenna analyzer or network analyzer to measuring with the
actual full power PA and meter hooked up. This may be partly due to
the fact that the meter is usually not a perfect 50 ohm thru, and
partly due to the fact that the analyzers outputs are closer to 50 ohms
than the PA.

Sorry, that is exactly wrong. S11, SWR and the impedance itself, do
*not* change when you connect a different instrument to the same load.
All the changes you have described are due entirely to instrument
errors.

That's how the instrument errors are determined... by knowing for a fact
that, whatever all the different instruments may say, the impedance
they're trying to measure is the one thing that has *not* changed.

--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek