"Reg Edwards" wrote in message
...
Reg, you've aroused my curiosity on three points:

Why would you use 'Smith Chart' and 'anger' in the same sentence?

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Just a figure of speech. "Anger" suggests setting about a job with
energy, determination and a sense of purpose. As distinct from mere
amusement.

And I thought I understood the English language. Obviously I miss some of the
ways you Brits use it. Thanks for the clarification--makes sense now.

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Why are there any frequencies where the Smith Chart is misleading
and useless?
Which frequencies are they?
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Depending on the size of the errors one is prepared to tolerate and on
the calculated parameter of interest -

Frequencies at which line attenuation per wavelength is not small.
Frequencies at which Zo is not purely real.
Frequencies at which CR is not equal to LG.
Frequencies at which the reflection coefficient is greater than 1.0

Comment : Zo is never purely real. CR is never equal to LG.
And the chart is good only to 2-digit accuracy anyway.

But Walt, you already know all this. Have you ever tried the Jones
Chart? ;o)

You're right, Reg, I do know this, but as Cecil has just now beat me to the
punch, the attenuation scale that goes with the Smith Chart allows the complex
impedance loci to spiral inward with line length for any given value of line
attenuation. The loci is a circle only for lossless lines, but you already know
this.
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How can you say the Smith Chart is misleading and useless if you've
never used
one, and never inspected one for more than a minute?

Walt, W2DU

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No problem! Worked it out for myself many years ago. Some years ago
I introduced to this newsgroup the excellent book "Transmission Lines"
by Robert A. Chipman, 1968. It aroused some interest. Some of you
obtained a copy.

I used the Chipman tome since around 1969, shortly after it was released.
Interesting that you introduced it to this NG in 1968, but I didn't learn of
this NG until the 1990s. I have two copies, one at each of my homes in Michigan
and Florida.

It has a whole chapter devoted to the Smith Chart and fully describes
its limitations, imperfections, short-comings and approximations.

But the reason Chipman included the chapter was because of the great
savings in labour and time (in HIS day and age) when doing approximate
calculations on short, low loss, HF transmission lines such as antenna
feedlines for which it was designed. Which is all radio amateurs ever
use it for. Hardly any amateurs ever use it in anger. It has other
applications.

I first programmed a computer for work on transmission lines around
1960. At frequencies between 0.1 Hz and 1 MHz, frequencies at which
nobody would dream of using a Smith Chart. So I never became addicted
to it.
----
Reg.

Very interesting, Reg, but of course I knew of your many years of work with
undersea lines, so use of computers around 1960 doesn't surprise me. A little
bird told me one day that those lines aren't lossless. But, shucks, I coulda
found that out if I'd only dug deeper into Chipman, couldn't I?

Thanks for the informative response, Reg,

Walt