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Re: [TowerTalk] Ladderline - what are the facts??/

Subject: Re: [TowerTalk] Ladderline - what are the facts??/
From: Steve Hunt <steve@karinya.net>
Date: Thu, 07 May 2009 19:20:15 +0100
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Rob,

Unfortunately you wont be sure!

The MFJ meter only compares the magnitude of the current in the two 
wires; crucially it doesn't look at the phase. So when the meter 
indicates "balanced" any one of the following might be true:

* The line is indeed balanced
* The currents are equal magnitude, but the line is unbalanced because 
they are not 180 degrees out of phase
* The line is unbalanced, but the meter is at a null in the common-mode 
standing-wave pattern

The most extreme example would be a line carrying all common mode 
current (no differential mode) split equally between the wires - the MFJ 
would tell you that was balanced!

73,
Steve G3TXQ

Rob Atkinson wrote:
> Anyone
> uncomfortable with these assumptions can get a parallel wire RF amp
> meter from MFJ and check their line to be sure, and try making
> adjustments if the line turns out to be extremely unbalanced.
>   

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