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[TowerTalk] High Antenna Modelling

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Subject: [TowerTalk] High Antenna Modelling
From: (Pete Smith)
Date: Sat, 02 Feb 2002 09:24:48 -0500
At 08:54 AM 2/2/02 -0500, Don Havlicek wrote:
>> A lot higher than 4-6 wavelengths.  I ran a 10m yagi in EZNEC at 200 feet
>> above ground, and both the deep nulls and reflection gain were still fully
>> evident.
>Obviously, the mathematical functions utilized within the modelling
>program do NOT vary when the height above ground [or HAAT] is
>This is one of the reasons that we must NOT trust the software to give
>EXACT answers, but rather to give 'idealized' situational results of the
>MATHEMATICS involved [not shouting ... just emphasis].

Sorry, but I don't agree.  This modeling software (NEC-2) would be of no
use at all if it hadn't been extensively verified against the real-world
situations that it was developed to model.  There are known limitations of
this representation of real antennas, but a yagi 4-6 wavelengths above
ground at 28 MHz isn't one of them, and certainly isn't "excessive."
Varying the height of the model yagi above ground, from less than 1
wavelength to more than 6, shows a smooth and predictable change in the
radiation pattern that is entirely consistent with experimental data 

73, Pete N4ZR

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