[TowerTalk] Change in Frequency As Antenna Height Rises

[StellarCAT]

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 at 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