[BC] Directional Antenna Proofs - Ground systems.

[Robert Meuser]

Richard,

That would be a good question to post on Topband. I bet there are one or 
two serious people there who could actually do a real world test.

On 6/21/12 1:36 PM, Richard Fry wrote:

> Having finally acquired a license for NEC-4.2, I modeled a 1/4-wave,
> series-fed monopole (1500 kHz), driven against just two 1/4-wave  horizontal
> radials 90 degrees apart, and buried 1 meter in 6 mS/m dc 13 earth.  The
> model was constructed per the rules for NEC4, and had no geometry or
> segmenting errors.  The calculated h-plane pattern was perfectly
> omnidirectional.
>
> At first I was skeptical, but now I'm thinking that result might be
> correct -- because all of the useful radiation from this system still
> originates from the r-f current that flows along the vertical conductor,
> which radiation would be omnidirectional in the horizontal plane.
>
> The loss in the ground plane within about 1/2 wavelength of the monopole
> controls the amplitude of the displacement/conduction currents in that
> region that return to the transmit system  That loss is relatively high in
> this 2-radial case, and antenna system efficiency is reduced.
Just wondering what others might think about this. Have real-world 
measurements of the groundwaves of single monopoles shown directional 
effects within a few kilometers from the site due to buried radials 
missing over large sectors?