Smith Chart Amusements

The Smith chart is just a map of the function

rho = Z-Z0/(Z+Z0)

that is, reflection coefficient rho to load impedance Z (Z0 is the line impedance). The rectangular coordinates in the Smith chart represent the real and imaginary parts of the reflection coefficient and the sets of perpendicular circular arcs give you the load impedance. So if you fire up Matlab, IDL, or Octave or some language that has complex numbers you can just do the math and forget Smith.

Paul Probert

If you want real amusement, make a circuit so the pattern is very reminiscent of Mickey Mouse...

Yeah, and the Rosetta Stone is just a big rock. :-)

That's probably fine for Jim's case, but in general one can gain a lot of insight into how a circuit is behaving and how to tweak it by watching it on a Smith chart, since it's simultaneously telling you impedances, reflection coefficients, SWR, and Q, and you know how changes will change all of these since you know what their contours look like. I think all the RF guys would really start screaminig if network analyzers and RF design software no longer had the option to display results on a Smith chart!

Yep. It's also valuable on paper. I remember a flight of several hours, to a client. Finding the problem and possible solutions took under half an hour, thanks to a stack of Smith charts. I forgot how many hours they had already spent writing MatLab routine but it was a lot.

Oh, and on account of the TSA I had to buy compasses at the next Walmart along the freeway. The $1 school edition in blue plastic :-)

Jim,

For you, the best way to re-capture what a smith char is, and then be plottting circles, semicircles etc, would bst be dome over a beer witha fet smih charts..then we can use smith chart software, and some exemplrary problem and "draw then out" on the elelconic smith chart.....

I'm sure Thompson remembers when that was made. (Ducking and running).

Jim? I thought the running gag these days was McCain's age...

Tim

-- Deep Fryer: A very philosophical monk. Website @

Naaah! Slowman wasn't old or senile... he was just incompetent ;-)

...Jim Thompson

Every conservative should remember that stone since the emperor of Egypt declared on it taxes that are to be repealed. Ain't happening much these days. Heck, even AMT isn't repealed even though it's unfair.

The interesting fact is that back in the old days they had to publish in three languages while we need "only" two ...