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Re: [TowerTalk] wire antenna question

Subject: Re: [TowerTalk] wire antenna question
From: Steve Hunt <>
Date: Fri, 14 Nov 2008 16:12:31 +0000
List-post: <">>

I agree that for most "normal" situations minimum VSWR and resonance are 
coincident. But I have given one example, and there are others, where 
they are not.

The values I quoted were taken from EZNEC VSWR plots, and confirmed in 
the VK1OD on-line calculator.

Steve wrote:
> Steve, when I plug your numbers into a transmission line program I get 
> these results:283.8 -j23.66 = 5.72 vswr (same as your example).
> 288.2 +j0 = 5.7 vswr which is just slightly lower than example #1 but 
> illustrates better vswr when j=0.
> I did not look into the 40 +j4 case but in general, real antennas show 
> a reactance change much greater than a resistance change when they are 
> in the range of one half wavelength. I would expect a reactance of 
> maybe 20 ohms (positive) for an increase of 5 ohms in the resistive 
> value. This would show a vswr of 1.55 which is higher than the 40 +j0 
> value of 1.25.
> Perhaps someone can model a dipole to confirm or refute this.
> 73,
> Gerald K5GW


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