What a great effort by G3TXQ and AC6LA showing how close actual resonances
are to modeled ones. Modeling has some limitations, especially NEC2, but if
done properly the results are amazingly accurate.
John KK9A
To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Change in Frequency As Antenna Height Rises
From: Dan Maguire via TowerTalk <towertalk@contesting.com>
Reply-to: Dan Maguire <djm2150@yahoo.com>
Date: Thu, 2 Jun 2016 20:30:22 +0000 (UTC)
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Steve G3TXQ wrote:
>>> Here are the resonant frequencies I measured of a 10m half-wave dipole
on a
>>> telescopic push-up mast at various heights above ground in my back yard:
Using a dipole model with a 1" diameter aluminum wire over "Very Good" EZNEC
ground, I adjusted the length to match the G3TXQ measured resonant frequency
at
the 15 ft height. That made the length 15.28 ft or ~0.47 WL. Then I
calculated the theoretical resonant frequency at other heights from 5 to 25
ft.
http://s33.postimg.org/oqqqmprhr/resonate7.png
Note that I did *not* force the almost perfect correlation at the 25 ft
height.
Dan, AC6LA
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