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[TowerTalk] High Antenna Modelling

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Subject: [TowerTalk] High Antenna Modelling
From: (Don Havlicek)
Date: Sat, 02 Feb 2002 08:54:56 -0500
Comments inserted below:

Pete Smith wrote:
> At 09:13 PM 2/1/02 -0500, Chuck wrote:
> >
> >In getting back to the basics, I submit that at heights over 4 to 6
> >wavelengths above ground, the antenna is in "free space" and
> >that's why the "nulls"are filled in. Also, at these heights, in free space
> >means you have no gain from ground reflection, so they are 5-6 db
> >down from lower antennas.  How does one define free space?  How
> >high above ground would you have to be to be considered in this category?
> 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].

Don-N8DE  [BSc, MAt, ABD - 'all but dissertation' - Mathematics]

> 73, Pete N4ZR

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