Topband: NVIS Antenna

[Jim Brown]

Roger,

I think you're observations propagation are correct, but I strongly 
disagree with the paragraph below. My experience has been that IF the 
antenna is accurately modeled, ground characteristics accurately 
represent where the antenna is rigged, and the appropriate NEC ground 
model is selected, modelling WILL correctly predict it's performance 
over FLAT terrain. It's well known that non-flat terrain has major 
effects on horizontally polarized waves, and N6BT has recently published 
his work showing that it also strongly affects vertically polarized waves.

73, Jim K9YC

On 3/16/2020 5:52 AM, Roger Kennedy wrote:
> The only other factor I DO think is that if you have a low dipole on 160m
> but DON'T have any radials or anything underneath it, it probably radiates
> more low angle than computer-modelling software would suggest. I believe the
> errors occur on 160m because it can't properly forecast the effect of the
> REAL WORLD ground when the antenna is a fraction of a wavelength above it.