Hi All,
I cannot improve, or add much to, the excellent commentary provided by Jim
Brown and others. However, I can say that my "experience" tends to confirm
a lot these findings.
First, I originally had an R7 vertical ground mounted. Performance was
"O.K.", but certainly not very exciting. Later I elevated that antenna to
about 15 ft. above ground, and the improvement was very noticeable.
Subsequently I have replaced the R7 with an F8 (acquired in an estate sale),
and the results are very much the same--the antennas are not all that much
different anyway, but the R8 is a bit taller, and does cover 6 meters (after
a fashion!). If you look at the study Ward Silver, N0AX, did many years ago
on various vertical antenna systems, the R8 is rated one of the very best.
In any event, I've worked well over 100 countries QRP on 40 meters using
this arrangement.
After hearing Rudy Severns' presentation about ground systems at Pacificon
several years ago, I began elevating radials when using my portable antenna
systems while camping. Most of this was done using either an MP-1 or a
Biddipole configured as a Buddistick. Again, the results were very
rewarding. As Rudy indicates, elevating your radials even just a small
amount can result in significant benefit. Usually I try to deploy 4
elevated radials. Sometimes, though, only 1 or 2 are practical under the
circumstances. Still, it helps!
I also acquired a used Sigma 40XK, and now use it as my primary 40 meter
antenna at home. That antenna is raised about 6 feet off the ground, so the
overall height is about 20 feet or so. I wish I could go higher, but
neighborhood restrictions prevent that. I get a 1 to 3 Db improvement with
this antenna over the R8, measured by comparisons using the RBN system.
I've become a big fan of vertical dipoles! When I go QRO (500 watts for
me), I get some reports from DX stations that I consider to be exceptional.
I also monitor myself on the RBN, so I have some idea as to who might hear
me and who can't. It's almost better than trying to interpret some of the
propagation software.
I also have one of N6BT's Bravo 7 antennas, which he calls vertical dipoles
also. By the way, N6BT also designed the Sigma 40KX when he owned Force 12.
Anyway, the Bravo 7 works pretty well as a portable system, but I'm not
quite as happy with it as a 40 meter system. Still, it is very portable,
and easy to put up and take down. N6BT makes some pretty aggressive claims
about the performance of this system, but I am pretty sure most of his
"testing" was done over salt water. In any event, the higher up I deploy
that system, the better it seems to work. I think Jim Brown's suggestion of
adding a better radial system to vertical dipoles may be exactly what I need
to try and do with the Bravo 7, particularly for 40 meter operation.
Soil conditions here in Arizona are pretty awful. It's not very often that
I go camping anywhere that offers anything much better. Deploying elevated
radials can be problematic, but it certainly seems worth the effort most of
the time.
Dave W7AQK
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