[TowerTalk] Practical Ground Screens for NVIS antennas

[Tom Rauch]

> Seems like this problem should be an easy one to model
with AO or similar
> modeling program.
> Tell the program the antenna is in free space, then define
the antenna and
> then the screen in the Z-lane below it. The diagonal
version would be
> easiest to model. Anyone want to give it a try?

Models do the very worse jobs trying to simulate earth
effects. First, we don't know what the ground really is and
can't easily measure it. Second, the model generally treats
the earth and a homogeneous media, and it isn't. Third, the
ground will change at any location and even at the same
location with soil moisture conditions.

Make life easy. Just lay the wire down extending outside the
general area of the antenna, covering as much of that lossy
surface as you can. The idea is to spread currents out as
much as possible over the widest possible cross section of
earth, not concentrate it all in one area. The goal is to
decrease current density in the lossy media.

73 Tom