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.
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