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