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Re: [TowerTalk] 39 +j0 ohms?

To: towertalk@contesting.com
Subject: Re: [TowerTalk] 39 +j0 ohms?
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Sun, 2 Dec 2018 12:27:29 -0800
List-post: <mailto:towertalk@contesting.com>
Where are you measuring?  You'll only get the actual impedance measuring right at the feedpoint with a very short piece of coax connecting the analyzer.

Now, it IS possible to transform a measurement made at the end of a long piece of coax to the feedpoint Z, but to do that you need to save the data to a file and export to software like AC6LA's ZPlots or AE6TY's SimSmith. AND you need to know the length of the feedline, know the exact type of coax, and plug both into the software.

73, Jim K9YC

On 12/2/2018 12:07 PM, Jamie WW3S wrote:
trying to understand a 40m vertical, my Rigexpert analyzer has Z, X, R and 
C.......when I measure the vertical at 7.125 (target freq) the SWR is 1.3:1, but the Z 
is 50 ohms, I’m told the impedance needs to be 39+j) ohms? How can I read that 
with my rigexpert.....I can get around 39 ohms at 7.400.....is my vertical too long, 
or too short?
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