o Any smooth impedance curve plotted on a
Smith chart will have maximum reactance
at a point on the curve which is tangent
to a constant-reactance curve on the
chart, or which lies at an end of the
impedance curve. Call the impedance at
the point of maximum reactance Zm.

o Clearly, it will be easier to see the
maximum-reactance point if you simply
plot the reactance versus the
independent variable (such as frequency).

o If the maximum reactance is at such a
tangency on a Smith chart, the point of
tangency will be independent of the
reference impedance to which the chart
is plotted.

o In general, the maximum-reactance point
on a constant-SWR circle which passes
through Zm will not be at Zm. Call the
point of maximum reactance on that
constant-SWR circle Zs.

o If you change the reference impedance to
which the Smith chart is scaled, clearly
Zm will still be the maximum reactance
point on the impedance curve. However,
Zm will in general have a different SWR,
and the maximum-reactance point on the
new constant-SWR circle which passes
through Zm will in general be different
from Zs.

o In other words, the SWR circles are useless
for finding the maximum-reactance point on
the impedance curve.

Example: Zm = 1000+j800 ohms
Ref. Impedance: 50 ohms: SWR = 32.82; Zs for that circle = 821.25+j819.73
Ref. Impedance: 300 ohms: SWR = 5.59; Zs for that circle = 865+j811.31
Ref. Impedance: 600 ohms: SWR = 3.; Zs for that circle = 1000+j800

(The 600 ohm case illustrates that there is no requirement that Zs and Zm differ.)


We now return you to your regularly-scheduled obfuscation.