See...
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> Newsgroups: alt.binaries.schematics.electronic Subject: Smith Chart
> Amusements - SmithChartDoodles.JPG Message-ID:
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>
> I'm trying to remember from 40+ years back, when I last used a Smith
> Chart... what do the circular patterns mean?
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> I suspect that they are perhaps due to a distributed R-L-C network?
>
> What think ye all?
>
> ...Jim Thompson
It seems that nearly everything maps onto circles on the Smith chart -- changing transmission line length, varying one of resistance, inductance, or capacitance while holding the others constant, stability circles -- they could all be made with a compass and pencil.