[antennaware] RE: SWR from R,X,Zo

[Dallas Carter]

Dave, Thanks a million for the help.  That's exactly the formula that I have been searching for.
It is correct and plugs into basic very nicely.  Now I can continue with my xmission line
matching and find values that yield acceptable matches with the help of W4RNL's fine
tutorial on the subject.  73  Dallas  W3PP

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From: 	Leeson[SMTP:leeson@earthlink.net]
Sent: 	Wednesday, August 04, 1999 9:02 AM
To: 	Dallas Carter
Subject: 	SWR from R,X,Zo

Here's the formula derivation for SWR from known R, X and Zo:

Reflection coefficient  refl = sqrt[((R-Zo)^2 +X^2)/((R+Zo)^2 +X^2)]

SWR = (1+refl)/(1-refl)

You can combine these two formulas into one for SWR

SWR = {1+sqrt[((R-Zo)^2 +X^2)/((R+Zo)^2 +X^2)]}/
                        {1-sqrt[((R-Zo)^2 +X^2)/((R+Zo)^2 +X^2)]}

Try this out with various values for which you know the SWR to be sure
I've gotten all the details right.  For example,

For R = Zo, X = 0, refl = 0 and SWR = 1

For R = 0, X = Zo, refl = 1 and SWR = infinity

For R = X = Zo, refl = 0.45 and SWR = 2.62

Give this a try...

73 de Dave Leeson, W6NL/HC8L
leeson@nova.stanford.edu




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