I do not believe that the radials will have an effect on the radiation
pattern.
John KK9A - W4AAA
To: <towertalk@contesting.com>
Subject: [TowerTalk] modeling compare: 80M, 2EL vs 4SQ
From: "StellarCAT" <rxdesign@ssvecnet.com>
Date: Sat, 14 Mar 2015 19:47:59 -0500
Hello all.... please forgive the rehash but I feel a bit excited, at least
for
me on finding out HOW IMPORTANT ground quality is in evaluating a 4sq.
Brief history: I had a rotary dipole in Arizona on 80 at 131' and it
performed
very well equaling and often beating out 4 sq's in the 'area' (few hundred
miles out) very often except on LP.
So I'm moving to South Carolina and planning on a station there. I'm
wondering
about 80. Do I do the rotary again? Do I do a 4 sq? (dreaming: 2 el?)
I've never seen a model of a 4 sq that included radials (EZNEC-5) ...note:
I'm
sure they're out there - just haven't seen one. So comparing to me was a bit
meaningless using the
provided 4square that comes with EZ (it has none). So I read the manual
again
and I believe figured out how to do the radials - or at least an
approximation
of them.
If I put in 17 radials that are each 0.15 WL long at 0.3 ft above ground
(the
elements starting here as well)... this allows me to provide a
non-overlapping
radial field (so no worries
about problems with EZNEC geometry check). I know, I know - short and few -
but
that is addressed later...
Using 2mS and comparing its results to a 130' high dipole the dipole is
equivalent at essentially all angles and exceeds the 4sq at 10 degrees with
more than 2db more gain at its peak of 24 degrees.
If I change to 8mS, about what I had in AZ, indeed the crossover point is
now
19 degrees and the 4sq is 5db stronger at say 5 degrees showing what I often
saw on LP and very long contacts again in AZ.
If I change to 30mS ... what some people have - wow - big difference. The 4
sq
REALLY plays well.
Going back to SC where the ground is 2mS: If I add in a 2el beam at this
same
height as the dipole and compare it to the 4sq ... well now the beam is
better
at all angles... 3db better at 5 degrees and 6db at 15 deg.
Of course I know there will be a difference in the 4sq with longer and more
radials. Where I'm stuck is how to add these with the geometry check of
EZNEC.
(Or even more complicated: how to do the '+' center connection rails often
shown for a 4 sq radial system).
If anyone can help please drop me an email at
garymyers at powerc dot net. Thanks, Gary, K9RX
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