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Re: [TowerTalk] Choke on feed point of dipole

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Choke on feed point of dipole
From: David Gilbert <ab7echo@gmail.com>
Date: Tue, 13 Jan 2026 14:53:16 -0700
List-post: <mailto:towertalk@contesting.com>

I already explained all of that.

Default ground specs were used.  (0.005/13 over Real/MININEC)

The ground plane antenna had four 1/4 wave horizontal radials 4 feet off the ground.  The bottom of the vertical dipole was also 4 feet off the ground.

Yes, the vertical dipole had greater field strength at low levels, but as I stated the difference was only a few degrees ... the max was at 17 degrees for the vertical dipole and 23 degrees for the ground plane and there was barely a couple of tenths of a dB difference at the two maximums.

You can easily model this yourself (I used EZNEC Pro/2+ v2 with NEC5) if you don't believe me ... but I suspect that you already have in the past so I don't understand the questions.

Dave   AB7E



On 1/13/2026 1:21 PM, Jim Brown wrote:
On 1/13/2026 11:09 AM, David Gilbert wrote:
but the maximum gain is almost identical.

How did you model ground loss? What radial system? Any vertical with a current maxima near the ground will need a return, and current in that return has some loss.

Once you've done all that correctly, save the vertical pattern of one, then compute the vertical pattern for the other, and add the saved plot to it. The half-wave antenna will have greater field strength at low angles, and depending on your soil, may have less ground loss.

http://k9yc.com/AntennaPlanning.pdf

73, Jim K9YC

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