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January 29th 04, 01:45 PM

Richard Clark wrote in message . ..
On 28 Jan 2004 03:39:57 -0800, (Maurizio) wrote:

Hi all,
Is there anybody with some experience in MF antenna modelling with
ground effect included (surface wave/space wave) etc. ?
I have the need to find out if the NEC4 is able to modellize this type
of antenna in a general environment and with which performance.
Otherwise, I will have to find out alternative ways (FEM/...).

Thanks in advance for any suggestion

Best regards

Hi Maurizio,

Antenna modelers (NEC engines) render far, far field results. The
effect of ground is considered only for
1. its impact on feedpoint Z;
2. equivalent launch angle (from the perspective of very far, or DX,
receivers).

What you describe as your need sounds more like the province of
propagation modelers. There are some add-on packages that incorporate
with antenna modelers to allow for a variety of terrains; but even
those, I think, still relate to the very far, DX, receivers.

Even the propagation modelers (like VOACAP and VOAAREA) are tailored
for HF and the far, far field. Our references from the FCC for MF
broadcast stations stands as a resource. Those references go back
many years and little has advanced the science as it has served the
industry very well.

73's
Richard Clark, KB7QHC

Hi Richard,
I know that some studies have been done in the past using NEC4 to find
the ground wave/space wave fields, but my primary interest is in the
near zone modelling of such MF antennas, in particular in presence of
non-flat ground.
The scope is to make a tool to evaluate the radiated fields in
inhabited regions with limits in the maximum field amplitude.
A tool dedicated to this task would be very useful for the site
evaluation.

I have some idea on based on recent studies, but maybe (as often
happen) that others have already done something interesting.

Are these FCC resources dealing with such issues ?
And if so are they freely available?

Thanks in advance

Maurizio

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