If you really want to get accurate ground modeling,
you need to follow N6LF's procedure. He installs low
dipoles at various heights over his ground and
measures their impedance and resonant frequency.
He then models them on NEC4 and tweaks the ground
parameters to get the model to agree with the
measured data. This is repeated on each band
of interest.
The other problem is that the ground may not
be homogeneous, in either the horizontal direction
or the vertical direction. Not to mention
seasonal moisture effects.
If you can manage a low dipole, there is a good
chance you reconfigure it as a T-top loaded vertical with
a few elevated radials. That is likely lead to
a worthwhile improvement in performance over any
kind of ground.
73
Rick N6RK
On 11/7/2018 3:19 PM, Roger Kennedy wrote:
Actually, I'm rather sceptical about the accuracy of theoretical antenna
modelling software generally on 160m. (as per my recent discussion on a
well-known Forum)
I'm not convinced that the various programs (which all seem to give
different projections) properly take into account the different kind of REAL
ground under the antenna . . . particularly with a low Dipole like I use -
which is equivalent to a 20m Dipole just 3ft off the ground ! (and
therefore the ground has a HUGE effect on the antenna)
Roger G3YRO
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
|