Dr. Slick wrote:
When was the last time you used
"G = C * R / L" for anything?

Yesterday.

Dear Reg,

The Smith Chart only constrains the normalizing quantity to be purely
resistive - not the characteristic impedance of a particular
transmission line being shown on that chart. My program, SmartSmith,
for example, allows the user to specify both an Ro and an Xo term for
all transmission line sections.

Bob, W9DMK, Dahlgren, VA

===================================

Hi Bob,

But your program is not a Smith Chart. It's probably better than a Smith
Chart.
----
Reg.

Bob, your program can probably calculate the input impedance, Rin + j*Xin,
of a line having Zo = Ro + j*Xo, with given attenuation Alpha dB, and given
phase-shift Beta radians, with a terminating impedance Rt + j*Xt.

Which is a commonly needed quantity on the way to calculating the ultimate,
all-important, single number, transmission efficiency.

But can you do it with nothing at hand except a Smith Chart?
----
Yours, Reg.

On Fri, 26 Nov 2004 22:05:13 +0000 (UTC), "Reg Edwards"
wrote:
But can you do it with nothing at hand except a Smith Chart?
Turn the chart over and write the math on the back - GEEZ

Turn the chart over and write the math on the back - GEEZ

===========================
Can you do it yourself within 3 months? It will take that long to dig out
the formulae.


I've just realised this is the first occasion I've ever been at the bottom
end Z of a newsgroup message listing. You can't get any lower!
----
Yours, Punchinello.

On Fri, 26 Nov 2004 22:05:13 +0000 (UTC), "Reg Edwards"
wrote:

Bob, your program can probably calculate the input impedance, Rin + j*Xin,
of a line having Zo = Ro + j*Xo, with given attenuation Alpha dB, and given
phase-shift Beta radians, with a terminating impedance Rt + j*Xt.

Which is a commonly needed quantity on the way to calculating the ultimate,
all-important, single number, transmission efficiency.

But can you do it with nothing at hand except a Smith Chart?

And the answer is...







an unequivocal NO.

However, just to satisfy my curiousity, exactly which of your
beautiful, zipped up Pascal programs will do that for me?
Bob, W9DMK, Dahlgren, VA
http://www.qsl.net/w9dmk

Bob, your program can probably calculate the input impedance, Rin +
j*Xin,
of a line having Zo = Ro + j*Xo, with given attenuation Alpha dB, and
given
phase-shift Beta radians, with a terminating impedance Rt + j*Xt.

Which is a commonly needed quantity on the way to calculating the
ultimate,
all-important, single number, transmission efficiency.

===============================================

Bob asked -
However, just to satisfy my curiousity, exactly which of your
beautiful, zipped up Pascal programs will do that for me?

===============================================
Bob,

I thought nobody would ever ask. But they've been available from my website
for years.

Look at Programs -

RJELINE2
RJELINE3
RJELINE4
COAXPAIR
COAXRATE

and give yourself a few practical examples.

There is a one-line description after each program's name on the download
page in my website.

The above programs are dedicated to transmission lines. Input data includes
one or two physical dimensions which avoids restriction to particular
type-of-line numbers. Users are given a free hand to design cables to their
own specifications. Nevertheless, they are practical in nature and simple to
use. There are other programs which incorporate the same calculations but
which are not explicitly apparent to the user.

They use exact classical transmission line formulae and so are as accurate
as the input data over the stated frequency ranges. Usually from power
frequencies up to UHF. They take skin effect and the increase in inductance
at low frequencies and other subtle factors such as conductor proximity
effect in twin-lines in their stride.

They are good enough for the highest precision engineering applications. I
have not disclosed the source code to prevent it falling into the hands of
argumentative vandals, so-called guru's, and technically ignorant old-wives
who would ruin the programs' reputation, not forgetting mine, for
RELIABILITY. Reliability is Quality versus Time.

For references I quote my only tutors - Ohm, Ampere and Volta.

When considering transmission lines you can check your's and other programs
against mine for accuracy with confidence. You will discover the effects of
both your known and other, unsuspected approximations.

Readers should bear in mind I'm not getting paid for this.

Bob, I'm on MontGras, Chilean, Reserve Merlot, tonight. Nuff said.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

For those with a mathematical bent, alternatively stated, for the angle of
Zo to be zero, or for Zo to be purely resistive -

L * G = C * R

or

L / C = R / G

which relationship is derived from -

Zo = Squareroot( Z / Y )

Where line series impedance Z = R + j * Omega * L

and line shunt admittance Y = G + j * Omega * C

provided the angle of Z is equal to the angle of Y.

Which makes Zo = Ro + j * ZERO

QED
------
Reg, G4FGQ