Philip H. Smith, Fellow IEEE, was born 101 years ago this Saturday and died
in 1987. Delevoped the Smith Chart for matching transmission lines (also
developed the cloverleaf antenna.)

Smith did not invent the Smith Chart. He simplified, for HF use only,
charts which had been in existence since the Victorian Age, which
covered all transmission line frequenies down to telephone and power
frequencies.

You should be warned against using Smith Charts at frequencies less
than about 1.5 or 2 MHz. Errors can be introduced of which you may be
unaware.

On the other hand, at higher frequencies, the Smith Chart is an
accurate time saver when making ordinary engineering transmission line
calculations.

But now very much superceded by small computer programs which exceed
the Smith Chart in both user time and accuracy,
----
Reg.

Smith did not invent the Smith Chart. He simplified, for HF use only,
charts which had been in existence since the Victorian Age, which
covered all transmission line frequenies down to telephone and power
frequencies.


That is not quite correct, what Smith did was to take to concept of the
pre-existing equations and a rectangular chart which covered a limited range
of impedances and develop them into a circular, more complex chart, that
covered a full range of impedances. See the Introduction to Smith's book
"Electronic Applications of the Smith Chart".

Regards
Jeff

"Jeff" wrote
Smith did not invent the Smith Chart. He simplified, for HF use
only,
charts which had been in existence since the Victorian Age, which
covered all transmission line frequenies down to telephone and
power
frequencies.


That is not quite correct, what Smith did was to take to concept of
the
pre-existing equations and a rectangular chart which covered a
limited range
of impedances and develop them into a circular, more complex chart,
that
covered a full range of impedances. See the Introduction to Smith's
book
"Electronic Applications of the Smith Chart".

Regards
Jeff
=========================================

Agreed. Your description of what Smith did is more accurate than
mine.
----
Reg.

"Reg Edwards" wrote in message
...
...
You should be warned against using Smith Charts at frequencies less
than about 1.5 or 2 MHz. Errors can be introduced of which you may be
unaware.... ----

Reg.

I'm curious. Would you briefly summarize the type/cause of the Medium
Frequency errors.

73, Steve, K9DCI

-- If you are unaware of the errors at low frequencies, it may well not
make much difference whether you are using the Smith chart or not.
Those errors may still bite you.

-- If your computer isn't powered up and you have a quick calc to do,
the "small computer program" may very well far exceed the Smith chart
in user time!

-- Though a program may provide more accurate calculations for the
given input values than a Smith chart, it would be unusual that you
KNOW the impedances, line lengths, inductances, etc. that you are
working with to the accuracy to which they can be plotted on a
decent-size Smith chart. It's easy to plot things to within 0.01
reflection coefficient units on such a chart, and it's very likely that
the "50 ohm" coax you are using will be further away from 50 ohms than
that. To quote some famous guru, 'Have you never heard of the word
"approximation"?'

-- For those of us who appreciate that sort of graphical
representation, a Smith chart can be a wonderful visualization tool.
To me, that's its strongest point. Forget using it to DO the
calculations; let a computer program or a vector network analyzer do
the calcs or make the measurements. It's still worthwhile to me to
have the results presented on the Smith chart overlay of complex
reflection coefficient. (Note that a Smith chart is 'just' grid lines
on top of a linear graph of reflection coefficient referenced to the
normalization impedance you're using.) And of course it's useful for
far more than just transmission lines.

For those who always have an appropriate calculating engine at hand and
don't get anything out of a graphical representation of the results,
toss the Smith chart out the window. But don't assume it's not still
_very_ useful to those who see things easily from the graphics. Can
YOU look at a table of 100 values of complex reflection coefficient
versus frequency for a component and summarize them in your mind as
rapidly as you can by looking at the same values plotted on a Smith
chart? If you can, that's great. I can't. Thank you, Mr. Smith.

Cheers,
Tom

On 28 Apr 2006 09:42:16 -0700, "K7ITM" wrote:

-- If you are unaware of the errors at low frequencies, it may well not
make much difference whether you are using the Smith chart or not.
Those errors may still bite you.

-- If your computer isn't powered up and you have a quick calc to do,
the "small computer program" may very well far exceed the Smith chart
in user time!

-- Though a program may provide more accurate calculations for the
given input values than a Smith chart, it would be unusual that you
KNOW the impedances, line lengths, inductances, etc. that you are
working with to the accuracy to which they can be plotted on a
decent-size Smith chart. It's easy to plot things to within 0.01
reflection coefficient units on such a chart, and it's very likely that
the "50 ohm" coax you are using will be further away from 50 ohms than
that. To quote some famous guru, 'Have you never heard of the word
"approximation"?'

-- For those of us who appreciate that sort of graphical
representation, a Smith chart can be a wonderful visualization tool.
To me, that's its strongest point. Forget using it to DO the
calculations; let a computer program or a vector network analyzer do
the calcs or make the measurements. It's still worthwhile to me to
have the results presented on the Smith chart overlay of complex
reflection coefficient. (Note that a Smith chart is 'just' grid lines
on top of a linear graph of reflection coefficient referenced to the
normalization impedance you're using.) And of course it's useful for
far more than just transmission lines.

For those who always have an appropriate calculating engine at hand and
don't get anything out of a graphical representation of the results,
toss the Smith chart out the window. But don't assume it's not still
_very_ useful to those who see things easily from the graphics. Can
YOU look at a table of 100 values of complex reflection coefficient
versus frequency for a component and summarize them in your mind as
rapidly as you can by looking at the same values plotted on a Smith
chart? If you can, that's great. I can't. Thank you, Mr. Smith.

Right on.

And another handy feature is the ability to see what elements of a
matching network are doing. Lines of constant Q drawn on the chart
can also keep one out of trouble.

I remember one thread about 3 years ago wherein someone (he knows who
he is) stated that fewer matching elements -always- provide a lower
loss solution than more elements do. A few minutes with a Smith chart
with some constant Q circles and I found an example where that is not
the case.

N7QR wrote:

Philip H. Smith, Fellow IEEE, was born 101 years ago this Saturday and died
in 1987. Delevoped the Smith Chart for matching transmission lines (also
developed the cloverleaf antenna.)



I fell in love with his chart in my college days.

For my transmission lines courses we were offered the option of using
the chart or doing the math. If we chose the chart, the only credit was
for a correct answer. If we chose the math, we could get partial credit
based on proper process. The exam was scheduled for 3 hours. Two of us
left the exam room in 20 minutes with perfect scores on the final exam.

That was 48 years ago. I wish I could remember everything I've
forgotten. Heck! I wish I could remember 10% of it!!!!

In article , "Reg Edwards"
g4fgq,regp@ZZZbtinternet,com wrote:

"Jeff" wrote
Smith did not invent the Smith Chart. He simplified, for HF use
only,
charts which had been in existence since the Victorian Age, which
covered all transmission line frequenies down to telephone and
power
frequencies.


That is not quite correct, what Smith did was to take to concept of
the
pre-existing equations and a rectangular chart which covered a
limited range
of impedances and develop them into a circular, more complex chart,
that
covered a full range of impedances. See the Introduction to Smith's
book
"Electronic Applications of the Smith Chart".

Regards
Jeff
=========================================

Agreed. Your description of what Smith did is more accurate than
mine.
----
Reg.

Hello, and there appears to be faulty logic here. Any other form of chart
not in Smith's format or variants thereof (e.g. a Carter Chart) cannot be
a Smith Chart. The fact that Phillip Smith's and similar types of charts
are all based upon the transmission line equations is irrelevant to giving
due credit to their respective developers. Smith recognizes (pg xv, intro
to Smith's book) that similar charts (and their respective limitations)
formulated by others inspired him.

Do we say that since a couple of brothers from Dayton, Ohio leveraged
then-existing aviation technologies and ideas developed by others (e.g.
gliders) the Wrights shouldn't be given credit for inventing a successful
human carrying, heavier-than-air, propeller-driven aircraft?

And for the flip side, while many readily identify Marconi, DeForest, J.
Fleming and sometimes Tesla as radio pioneers how many can recall Edwin
Armstrong? Sincerely, and 73s from N4GGO,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

On Fri, 28 Apr 2006 19:55:19 -0400, Dave wrote:


That was 48 years ago. I wish I could remember everything I've
forgotten. Heck! I wish I could remember 10% of it!!!!

Thanks for that.
Now I know, I am not alone.

w.

--
Too much space is not good for my health,
said the astronaut and returned to Earth.