let me rephrase:

PA--+SWR meter1+--50ohm line--+SWR meter2+--50ohm line--+50 ohm
(same Z as PA) (50 Ohms) dummy
load
1 2 3


If you measure the SWR at point 1, you let Z1 (Zload) be 50 ohms,
and Zo is the output impedance of the PA. SWR meter1 should be
characterized to Zo.

I've agreed that SWR meter2s SWR reading (at point 3) will not
change as you change PAs impedance, but the SWR at point 1 definitely
WILL.

So, Does the SWR change as you change the source impedance? IT
DEPENDS ON WHERE YOU MEASURE IT! Right at the output of the source,
it will!

From Pozar's Microwave Engineering (Pg. 606):

Reflection Coefficient looking into load = (Zl-Zo)/(Zl+Zo)

It should be easy to see from this well known equation that a
perfect 50 Ohm Zl will definitely change SWR as you change Zo away
from 50 ohms.


Slick