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Re: [TowerTalk] S21 to Rp & Cp - Equivalent Circuit

To: towertalk@contesting.com
Subject: Re: [TowerTalk] S21 to Rp & Cp - Equivalent Circuit
From: Steve Hunt <steve@karinya.net>
Date: Sun, 14 Jan 2018 15:52:38 +0000
List-post: <mailto:towertalk@contesting.com>
A couple of additional "power" signs appeared when I cut & pasted that formula from my web site into my email client. It should be:
R = (100.cos(θ).10 ^(- |S21| / 20) ) - 100

Thanks to Maximo for pointing it out.

It's exactly the same formula as Rick's for his special case of a resistive DUT, but with the addition of a cos(θ) term.

Steve G3TXQ


On 14/01/2018 13:19, Steve Hunt wrote:
The general case is simpler than I originally had it, because I'd missed a simplification using a trig identity. The revised version is here:
http://www.karinya.net/g3txq/chokes/s21.pdf

R = (100.cos(θ).10 ^(- ^|S21| / ^20) ) - 100

X = (R+100).tan (θ)

Steve G3TXQ




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