[TowerTalk] Change in Frequency As Antenna Height Rises

[john at kk9a.com]

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 at contesting.com>
Subject:	Re: [TowerTalk] Change in Frequency As Antenna Height Rises
From:	Dan Maguire via TowerTalk <towertalk at contesting.com>
Reply-to:	Dan Maguire <djm2150 at yahoo.com>
Date:	Thu, 2 Jun 2016 20:30:22 +0000 (UTC)
List-post:	<towertalk at contesting.com">mailto:towertalk at 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