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From: donty <donty@PRODIGY.NET>
To: <towertalk@contesting.com>
Date: Wed, 24 Jan 2001 15:57:45 -0700
To: <towertalk@contesting.com>
Subject: Alpha Delta DX-A Field Testing
Hi to all,
I have been following the comments on the DX-A Twin Sloper and wanted to
pass along our 15 years of field testing here at Alpha Delta comparing
slopers to dipoles to ground mounted verticals---both quarter wave and "half
wave". The sloper, whether commercial or homebrew, is often a misunderstood
and improperly installed antenna. When done right, it can be a real barn
burner on DX. Our experience in A/B testing over the years matches the
comments in the newest ARRL Antenna Handbook.
To work correctly, these rules need to be followed:
A. Put on a metal tower with an HF size beam on top to serve as a
"capacity hat".
B. Decouple the coax at the feedpoint with an RF choke (eg. 8 turns, 8
inches dia.)
C. Make sure there is excellent ground return integrity down through
tower, to ground rods or radials.
D. Guy wires, if any, must be broken with insulators, use no other wire
antennas on same tower, keep sloper wires away from gutters, metal fascia,
etc.
E. Keep 10 to 12 feet under beam, so as not to overcouple to either one.
A sloper works extremely well in the typical "home" site---not big gun
site---meaning a typical house lot and a 35 to 45 foot or so tower with a
tribander. When comparing a sloper under these conditions with an inverted-V
at the same height, I have found S-meter improvements of 5 to 10 dB favoring
the sloper on 80 and 160. (I know this is subjective as S meters are
inaccurate, but is real world). This is after HOURS and YEARS of testing at
sites into Europe and Asia from both Ohio and Arizona. Again---from average
installs---not big gun. Why not big gun? When you put your inverted-V up at
70, 80, or 90 feet the advantage of the sloper diminishes or goes away due
to the more favorable angle of the dipole. there is no free lunch! At the
typical home site, not sea side with elevated radials, the vertical doesn't
even come close to either the sloper or dipole. It "dies" on 80/160.
Bottom line: The sloper is a great 80/160 antenna for the typical "home"
site when mounted correctly. I had a typical home site in Ohio and worked
over 100 countries with it on 160. By the wat, I understand big gun sites--I
have one at my mountain home in northern Arizona. Oddly, my little C3SS up
there does about as good as anything. It's the site!!
Good DXing to all,
Don Tyrrell, W8AD, Alpha Delta Comm, e-mail: donty@prodigy.net
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