AH HA! Ok - so there is a difference between a dipole and a yagi. Great to
know! And if indeed that new model re a yagi shows similar results that
would be quite encouraging. My apologies if I missed that distinction
declaration earlier.
Gary
-----Original Message-----
From: Dan Maguire
Sent: Tuesday, May 31, 2016 4:27 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Change in Frequency As Antenna Height Rises
http://s33.postimg.org/4yn6idnsv/resonate5.png
From a height of 30 ft to 60 ft the Fres of the *Yagi* changed from 7.278
to 7.258 MHz (-20 KHz). Over the same range the Fres of the *Dipole*
changed from 7.132 to 7.349 MHz (+217 KHz). Ground reflection works in
mysterious ways when there is also mutual coupling between multiple
elements.
Bob K6UJ wrote:
With my 2EL Force 12 40M yagi, I followed Tom Schiller's guidelines and
set it up initially at 15 feet above the ground. When I raised it up to
70 feet the resonance frequency increased by 20khz.
This is a 3L Yagi, not a 2L, but the model shows similar results. From a
height of 15 ft to 70 ft Fres changed from 7.244 to 7.255 MHz (+11 KHz).
Since a *Yagi* model seems to be in the same ballpark compared to actual
measurements I don't see why a *Dipole* would be any different.
Dan, AC6LA
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