[TowerTalk] High Antenna Modelling

[Don Havlicek]

Pete,
Perhaps my use of the word 'excessive' wasn't quite correct for the
situation described, but the results of modelling are still IDEALIZED.

You say you don't agree .. but then you talk about a 'smooth and
predictable change in the radiation pattern' ... this is IDEALIZED .. 

As I said:

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



Pete Smith wrote:
> 
> 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
> >'excessive'.
> >
> >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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