On Mon, 14 Aug 2006 14:58:32 GMT, Cecil Moore
wrote:

Reg Edwards wrote:
I don't know, never did know, how to use an old fashioned, mid-20th
century Smith Chart.

Reg, I'm curious how you would solve this stub problem
without a Smith Chart.

| 45 deg | 45 deg |
Source====Z01=========Z02====open

Stub sections are lossless. Z01 = 600 ohms and is 45
degrees long. Z02 = 50 ohms and is 45 degrees long.
What is the impedance looking into the stub from the
source?

I missed the significance of this problem Cecil.

Is it principally a theoretical (being lossless) problem that a Smith
chart can solve, or does it have some other significance?

Whilst a Smith chart is great for visualising transmission line
problems, a great way for visually mapping impedance over a range of
frequencies, it isn't the most practical way to solve practical
problems when we have access to the computing power commonly available
to designers today.

Owen

PS: I think the problem you have given can be solved with simple trig:
find the reactance of the Z02 section using one trig term, find the
length of Z01 that would deliver that reactance using one trig term,
add that length and the actual length of Z01 section, find the
reactance of the Z01 section using one trig term. I could do that in a
flash with a scientific hand calculator while you were sharpening your
pencil.

It is a trivial problem either way, and can only ever be an
approximation of a practical problem.
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