RadioBanter - View Single Post - Rho = (Zload-Zo*)/(Zload+Zo), for complex Zo

September 7th 03, 02:14 AM

In article ,
(Dr. Slick) wrote:

(David or Jo Anne Ryeburn) wrote in message
.. .
In article ,
(Dr. Slick) wrote:

Hello,

Consider a source impedance of Zo=50+j200 and Zl=0-j200.
******

(1) A *source* impedance of Z_0 = 50 + 200j is easily arranged. A
*transmission line surge impedance* of Z_0 = 50 + 200j is impossible;
surge impedances of transmission lines must have angles between - Pi/4
radians and + Pi/4 radians.

Ok, a source impedance then.

In that case you shouldn't be using a formula intended to apply to the
surge impedance of a transmission line.

I don't fully understand why your last statement needs to be so.

I assume that by "last statement" you mean

"A *transmission line surge impedance* of Z_0 = 50 + 200j is impossible;
surge impedances of transmission lines must have angles between - Pi/4
radians and + Pi/4 radians."

This follows immediately from the formula Z_0 = sqrt((R + jwL)/(G + jwC)),
the facts that none of w, R, L, G, or C are negative, the way angles work
when one divides complex numbers and takes square roots, and the fact that
the real part of Z_0 can't be negative (which decides which of the two
square roots should be used).

Where do you stand David?

I believe that algebra speaks for itself. I believe that whether a model
accurately depicts reality has to be tested by experiment. And I believe
that when many such experiments have been previously carried out, all
confirming the accuracy of the depiction, any claim that the model is
inaccurate and that another one is accurate has to be supported with
extraordinarily strong empirical evidence.

David, ex-W8EZE

--
David or Jo Anne Ryeburn

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