Dr. Slick wrote:

PA----+----50 ohm line----+SWR meter+----50 ohm line----+50 ohm dummy
load
1 2 3



Once again, if you placed an SWR meter of the same output impedance
of the PA at point 1, you will measure the SWR at point 1, and it would
be akin to re-normalizing the Smith. Change the PAs S22 (and the
impedance of the SWR meter, and you will definitely change the SWR at
point 1. Do you agree with this?

What exactly do you think you mean by "change the SWR at point 1"? All
you have done is to replace one SWR meter by a second one that has been
calibrated for a different system reference impedance.

You had to *choose* a value for the new reference impedance in order to
pre-calibrate that second meter. When you re-normalize the Smith chart,
you choose the *same* new value. So of course the SWR reading on the
second meter is going to be the same as you'd calculate by
re-normalizing the SWR1 circle on the Smith chart from Z1 to Z2.

If that's all you ever meant, we've spent a week homing-in on something
that is totally obvious.

The only other problem with your example is that by mentioning the PA's
S22 value, you seem to imply that it is relevant. It isn't, because
variations in the source impedance will not change the SWR reading on
either meter. Only the load impedance can change the SWR.

Now take away all the coax and move the 50-ohm load to the outputs of
the respective SWR meters. The indicated values of SWR1 and SWR2 will be
exactly the same as before.



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