I'm pretty sure that antenna impedance will be the most affected for 
antennas less than a quarter wave above ground, and will go up and down in a 
damped sinusoidal pattern as it is raised further. You would probably need 
to be up 3 wavelengths or more to have minimal interaction.  If you're 
talking about radiation angle, it is most affected if the ground is very 
conductive.  As you get higher than a half wavelength above a conductive 
ground, you begin to develop lobes and nulls in the elevation pattern.  If I 
had some time, I would obtain a copy of EZ-NEC or a similar program and see 
if I could read any of its output.

-----Original Message----- 
From: Dave Marthouse
Sent: Tuesday, November 13, 2012 12:39 PM
To: [log in to unmask]
Subject: Antenna Interaction

Hi Gang,

I should remember this but I am putting this theory question out to the =
group.  What is the minimum altitude when an antenna stops reacting or =
interacting with ground?  Is it a half wavelength or a full wavelength?  =
Naturally for the purposes of this discussion I am leaving out ground =
mounted verticals.  It has been a while since I visited this segment of =
antenna theory.  Any info is appreciated.


Dave Marthouse N2AAM
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