I think both John's and Gary's commemnts square with the series on
radials that was on NCJ a few years ago. The message I took away from
those articles is that if your actual ground characteristics are good,
the improvement with radials, no matter how many, will be quite limited,
while if your ground isn't good to start with, radials can make a lot of
difference in the pattern, especially at low angles.
73, Pete N4ZR
Check out the Reverse Beacon Network at
http://reversebeacon.net,
blog at reversebeacon.blogspot.com.
For spots, please go to your favorite
ARC V6 or VE7CC DX cluster node.
On 3/14/2015 10:59 PM, john@kk9a.com wrote:
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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|