Hi All
I've been licensed for 5 years now and have done a fair amount of
operating, especially contesting, but only with wire antennas. I've
finally bought a new house where I can put up a tower and beam. I've
read as much as I can on eham.net and the manufacturer's site, as well
as the Towertalk archives, but I'm wanting to canvass as much advice as
possible as this is probably the only opportunity I'll ever have to
build my antenna system from scratch.
My primary requirement is to build the best possible contest station
that my 13,000 sq. foot suburban lot, XYL and limited budget will allow.
Due to budget limitations, I may have to build it over several years.
I'm planning a 15m tower, probably self-supporting (unguyed). The height
limit is because towers taller than 15m require an Environmental Impact
Assessment process, which could be costly and which effectively gives
any nearby neighbour the right to veto the project. So to keep it
simple, I'll stick to 15m, then I only require building plan approval,
but no EIA.
I'm planning to start with a tribander, and stack a 2 element 40m beam
in a year or two. The two tribanders that I'm mostly considering are the
F12 C-19XR and the Bencher Skyhawk. It seems to me that the Skyhawk
probably has the performance edge, and is possibly more sturdily
constructed. The C-19XR has the benefit of reduced weight, which means I
can still stack a 2 el 40m Yagi and stay more or less within the limits
of a Yaesu G-1000DXC rotator (the 240 V version of the G-1000DXA).
Although I can turn the Skyhawk by itself with the G-1000DXC, I would
need a G-2800DXC or similar to stack the 40m beam. The other advantage
of the C-19XR is that I believe one can use 3 feedlines with it,
allowing single-operator-two-radio or multi-op-two-radio contesting with
the appropriate antenna switches and filters.
The other option would be a single 4-band beam. The F12 C-39XRN is just
too big for my small lot, so that leaves something like the C-4SXLD.
essentially this would involve some compromise in gain on 20/15/10 in
exchange for gain on 40.
One thing to consider is that, living in South Africa, spares are
difficult to get and may take weeks or months to arrive, so a sturdy
installation is important. Regarding weather, we don't generally have
snow or icing problems. However in the summer (November-February, which
coincides with many important contests) we get tropical thunderstorms
that often have hail and winds gusts of around 50 kts (60 mph) are not
uncommon. I don't know what the maximum windspeeds recorded are, but
would like to exceed the fairly common 60 mph gusts by 50%, for a
planned wind speed survivability of 90 mph (hence the "D" rating on the
C-4SXLD). Lightning protection is also important, as Johannesburg has
one of the highest incidences of lightning strikes of any city in the
world - again during the November-Feb contest season :)
Sorry for the long post. Any advice, comments or suggestions will be
greatly appreciated!
73
Andrew ZS6AAA
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