"Reg Edwards" wrote in message
...
.............................
Yes, Rho CAN exceed unity when the termination is a passive network.

For example, when on a real line, Zo = Ro - jXo and the termination Zt
= Rt + jXt then Rho can exceed unity.

Rho has an absolute maximum value which approaches 1 + Sqrt(2) =
2.4142 which occurs when the angle of Zo approaches -45 degrees and Zt
is purely inductive.

It arises because of a weak resonant effect between -jXo and + jXt.

The angle of Zo of real lines always becomes more negative as
frequency decreases. Mr Smith's Chart does not recognise this. He did
it knowingly and deliberately. There are other departures from
reality. But at least it is fit for its few intended purposes.
----
Reg, G4FGQ

That is exacly what is in a book I have.

Tam

On Sun, 19 Jun 2005 10:58:15 +0000 (UTC), "Reg Edwards"
wrote:

Rho can never be greater than one going into a passive
network. Only when you have an active device, or gain, can
you move outside of the unity circle on the Smith Chart.

Slick

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

Yes, Rho CAN exceed unity when the termination is a passive network.

For example, when on a real line, Zo = Ro - jXo and the termination Zt
= Rt + jXt then Rho can exceed unity.

Thanks Reg, you beat Tom to it. [g]

This was beaten to death (well, I guess it *wasn't* beaten to death,
here it is again) over and over again.

Chipman in section 7.6 "Complex characteristic impedance" deals with
this and concurs with what Reg says above and below.


Rho has an absolute maximum value which approaches 1 + Sqrt(2) =
2.4142 which occurs when the angle of Zo approaches -45 degrees and Zt
is purely inductive.

It arises because of a weak resonant effect between -jXo and + jXt.

The angle of Zo of real lines always becomes more negative as
frequency decreases. Mr Smith's Chart does not recognise this. He did
it knowingly and deliberately. There are other departures from
reality. But at least it is fit for its few intended purposes.
----
Reg, G4FGQ

On 19 Jun 2005 02:58:26 -0700, wrote:



Wes Stewart wrote:
On 18 Jun 2005 14:20:34 -0700, wrote:

[snip]

Rho can never be greater than one going into a passive
network. Only when you have an active device, or gain, can
you move outside of the unity circle on the Smith Chart.


You better raise your deflection shield.


No need to, i have the laws of physics
on my side!

Hint: Conservation of Energy!

Hint. Read Chipman section 7.6.


He states in part, "To establish that the principle of conservation of
energy is not violated on a transmission line even when the magnitude
of the reflection coefficient at a point on the line exceeds
unity......."

Wes Stewart wrote:
He states in part, "To establish that the principle of conservation of
energy is not violated on a transmission line even when the magnitude
of the reflection coefficient at a point on the line exceeds
unity......."

Isn't it the same principle as a capacitor in a resonant circuit
being able to develop a higher voltage than the voltage incident
upon the resonant circuit?
--
73, Cecil http://www.qsl.net/w5dxp


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That is exacly what is in a book I have.

Tam

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

Good! That proves your book is correct.

Is it by Kraus or Terman?

"Reg Edwards" wrote in message
...
That is exacly what is in a book I have.

Tam

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

Good! That proves your book is correct.

Is it by Kraus or Terman?


Adler, Fano & Chu. It is the book Chipman used in his course.

Tam

Wes Stewart wrote:
"Go ahead Tom, you have the honor. "

It's not worth the effort, Wes. He wasn't willing (or perhaps he was
just unable) to do the math last year, and I suppose he isn't this year
either. He was willing to call me a liar instead of getting ahold of
Besser himself and verifying that Besser long ago corrected that typo
about using the complex conjugate in the formula for reflection
coefficient.

Anyone willing to start with the very basic idea that forward and
reverse waves on uniform TEM lines are independent and the ratio of
voltage to current in each of them is equal to the line impedance, plus
a few other elementary ideas like the sum of currents into a node is
zero can, with a bit of algebraic facility, verify the derivation of
reflection coefficient expressed in terms of line and load impedance.
Or, they can look in the archives (via Google, etc.) to see it
presented in past threads here.

Cheers,
Tom

K7ITM wrote:
Anyone willing to start with the very basic idea that forward and
reverse waves on uniform TEM lines are independent and the ratio of
voltage to current in each of them is equal to the line impedance, ...

What? You mean reflected energy doesn't "slosh" around? :-)
--
73, Cecil http://www.qsl.net/w5dxp

K7ITM wrote:
Wes Stewart wrote:
"Go ahead Tom, you have the honor. "

It's not worth the effort, Wes. He wasn't willing (or perhaps he was
just unable) to do the math last year, and I suppose he isn't this year
either. He was willing to call me a liar instead of getting ahold of
Besser himself and verifying that Besser long ago corrected that typo
about using the complex conjugate in the formula for reflection
coefficient.


And a liar you still are, apparently.

Besser has NOT corrected it, because it isn't
a typo! The ARRL also agrees.


Slick

Tam/WB2TT wrote:
"Owen" wrote in message
...
.............................
I do note that my ARRL Antenna Handbook (18th edition) and ARRL Handbook
(2000) both use rho, however they reckon that rho=(Za-Zo*)/(Za+Zo) (where
Zo* means the conjugate of Zo). They do this without derivation, and seem
to be in conflict with the derivation in most texts. I suppose the
derivation is buried in some article in QST and in the members only
section of the ARRL website.



Thank you, Owen. Les Besser agrees with the
ARRL.

However, in almost all practical calculations,
Zo is purely real, so that gamma=(Za-Zo)/(Za+Zo) is
used in most texts, and the results are the same.




Owen,

There was a big discussion about this last year, and somebody posted that
the ARRL was going to eliminate the conjugate reference.

Tam/WB2TT



Going to? It says 2000 on that ARRL Handbook!

They are NOT going to eliminate the conjugate
reference, because it's correct.



Slick