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Re: [TowerTalk] AV-640 (was GapChallenger ComparisonTesting Studies)

To: towertalk@contesting.com
Subject: Re: [TowerTalk] AV-640 (was GapChallenger ComparisonTesting Studies)
From: "Joe Subich, W4TV" <lists@subich.com>
Reply-to: w4tv@subich.com, "Tower and HF antenna construction topics." <towertalk@contesting.com>
Date: Mon, 26 Apr 2010 22:52:29 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Jim,

 > I'm not so sure I would agree with the premise that impedance matching
 > at an off-center point provides balance. Balance and VSWR are two very
 > different things, and one neither guarantees or precludes the other.

It's been 30+ years since I last read the original work but the test
plan involved current metering on either side of the attachment point.
The thesis was that when the currents on either side of the feedpoint
were the same there was no (in today's terminology) common mode current
in the feeder.  The thesis is still valid for "modern" "Windom like"
implementations (except for the Carolina Windom that intentionally
unbalances the feedpoint to force current into the coax shield as
a vertical radiator).

73,

    ... Joe, W4TV

On 4/26/2010 8:22 PM, Jim Brown wrote:
> On Mon, 26 Apr 2010 19:35:49 -0400, Joe Subich, W4TV wrote:
>
>> This made the
>> single wire a "flat," non-radiating line.  If the single wire, off
>> center fed antenna had any significant RF in the shack or feed line
>> radiation, it wasn't a Windom in your definition of the term.
>
> I'm not so sure I would agree with the premise that impedance matching
> at an off-center point provides balance. Balance and VSWR are two very
> different things, and one neither guarantees or precludes the other.
>
> 73,
>
> Jim K9YC
>

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