Jeff wrote:
w5dxp wrote:
The Z0 of the transmission line has not changed to 100
ohms so normalizing the chart to 100 ohms is not valid.

It is just as valid as using 50 ohms, and the result is the same, a changing
vswr.

No, the center of the Smith Chart is the Z0 of the transmission
line (when used on a transmission line). One cannot willy nilly
change the reference Z0. The confusion from doing such is obvious.

I see you have not commented on the main point of my post, that being that
the smith chart shows a changing vswr when you change the source impedance.

I think I see the problem. It is an *error* to change the
Smith Chart reference point when the source impedance
changes while the T-line Z0 and load remain the same.

Hint: transmission line transformers would not work if the vswr did not
change.

Hint: A lossless series-section transmission line transformer
has a *constant SWR*. It is the *constant SWR circle* that
causes the impedance transformation.

A fixed-constant SWR on 300 ohm line looks like it changes
when measured with a 50 ohm SWR meter but that is an illusion.
The SWR meter *must* be calibrated to the Z0 of the
transmission line in order to obtain a valid SWR reading.
The impedance is indeed being transformed all around the
constant SWR circle.

With your software, you are conceptually doing the same thing
as using a 50 ohm SWR meter on a 300 ohm transmission line.
The meter reading is invalid when taken at face value. The
meter reading does NOT indicate a valid SWR on the 300 ohm
feedline and neither does your software.
--
73, Cecil, http://www.qsl.net/w5dxp