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March 7th 06, 10:09 AM posted to rec.radio.amateur.antenna

On Mon, 6 Mar 2006 20:20:14 -0600, (Richard
Harrison) wrote:

Owen Duffy wrote:
"In formula 4-22b of my copy of Terman, the term on the lhs is |rho|
which is the magnitude of the reflection coefficient."

In my copy, 4-22b gives the "absolute value" of the reflection
coefficient (it is embraced with bars) which I believe means the
"absolute value" of a number or a symbol without reference to its
algebraic sign.

(4-22b):
+or- reflection coefficient=
SWR-1 / SWR+1

Richard, you seem to be dealing with reflection coefficient as a real
number when in fact it is a complex number. Your definition of |rho|
is inadequate when rho is complex.

Terman actually says in the preceding text "The standing wave ratio S
is one means of expressing the magnitude of the reflection
coefficient; the exact relationship between the two is..."

Your statement "On page 99 of Terman`s 1955 edition of "Electronic and
Radio Engineering" (my textbook was an earlier edition) is found the
formula to convert the reflection coefficient into SWR or vice versa.
These two parameters are innexorably locked together by formulas
(4-22a) and (4-22b)." is wrong where it says "convert the reflection
coefficient into SWR or vice versa" in respect of the "vice-versa"
because you ignore the fact that the reflection coefficient is a
complex quantity, and that the "magnitude of reflection coefficient"
is not the same thing as "reflection coefficient. You cannot calculate
the reflection coefficient from the SWR (except of course the special
case where SWR=1).

You have cited Terman in support of your own loose words, but Terman's
words are more carefully chosen and correct, yours are not, and the
Terman reference does not support your misconception at all.

Owen
--

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