Dr. Slick wrote:
Roy Lewallen wrote in message ...

. . .

If *you'll* review the Smith chart again, you'll find that *if* you set
the reference impedance to the Z0 of the transmission line you're
analyzing, then the SWR, impedances, and so forth that your read from
the Smith chart are correct. If you set the reference impedance to some
other value, an SWR read from the chart certainly isn't the SWR on the
transmission line.




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?

Absolutely not. The SWR meter will measure the SWR at point 1 only if
it's the same impedance as the *line*. If the PA has a different
impedance than the line, and the SWR meter has the same impedance as the
PA, it will not be reading the SWR on the line.

If you want to use a Smith chart to see what the SWR is on the line, you
must normalize it to the impedance of the line. Change the PA impedance
all you want. Change the Smith chart normalization all you want. Neither
will have any affect on the SWR on the line. Changing the meter
impedance won't have any effect on the SWR on the line, either, although
it'll change the reading on the meter so that it's no longer indicating
the SWR on the line.

I've already agreed with you that the SWR at point 3 won't change
in theory, as it is surrounded by 50 ohms. What is it about this
simple concept that you cannot seem to understand?

?

Thank you, although I'm not an expert at using the Smith chart, I know
my way around the circle.



It's obvious you don't. Time to read up on it, Roy.



I am always interested in learning. I don't use a Smith chart a great
deal,



Obviously.

I see you're reduced to insults now. Time for me to really leave this
thread. I'll leave you with your conception of how things work, hoping
only that the other readers aren't left with them also.

Roy Lewallen, W7EL