Before posing an unanswerable question, e.g. which array is a better choice,
let me thank the many folks who responded regarding K8UR type arrays and my
80M verticle query. Many helpful coments. The gist of things were verticle
and sloper arrays for 40M don't make it compared to 2L shortened yagis at
good heights. With that in mind, I've reconsidered my tower plans and come
back to an array that I designed about a year ago in preparation for our move
from So Cal to NC. I think it's time to build this thing and see how it
works, and will start digging holes after Floyd goes through. Assuming we
still have dirt to dig in that is.... In the meantime, I'm curious if the
collective wisdom of the group can find any obvious flaws in this array
design outlined below.
Tower: I can go to 90 feet max with guys out to 72 feet but no much more due
to lot shape. Wind here is 70 mph zone (Wake county), but folks that live
here know that peak winds in hurricane season can be much greater. I already
have 70 feet of Rohn 25G so that is the tower choice.
My first inclination was to do a pair of medium boom tribanders at 75 and 45
feet. Something like C19 or Skyhawks. These have nice gain, F/B and with
~22 foot turning radius they fit the area available very well (can go to
about 27 feet turning radius without taking out more trees and I don't want
to do that). That array is fine, but doesn't cover 40M with a yagi so I'd
need fixed wire beams or verticle arrays for that band. Due to the thickness
of the trees, wire yagis are going to be hard to get up, and limited to about
60 feet or so above ground. It would also be nice to get up closer to 1.6
wavelenghts on 20M for the top antenna.
Wanting to cover 10-40M on the tower and have a 2L rotating shorty for 40M I
have more or less settled on going to 90 feet with the 25G, guying at
30/60/90 out to 72 feet. Antenna choices will be Force 12 C4EXL at the top
and C3Es at 60 and 30 on swinging gate type mounts. Only real issues I see
is limited bandwidth from the shorty 40 and the linear loading (I can live
with that), the F/B and gain of the C3Es are less than the larger beams
(compromise of cost, rotating size and windload), and it's getting very close
to having too much on the tower. I can consider leaving off the low C3E, but
it'd be nice to have that on SA for DX events and for higher angle stuff in
domestic tests. I plan to guy with the anchors as suggested by Rohn
(concrete deadman) and will use EHS wire with insulators/preforms to break
the guys to non-resonant lengths.
This seems like a great array for a single tower station on a medium budget
but curious what do folks here think? Any obvious miss cues in there or go
for it?
Cheers,
Mark Curran
KI7WX
ki7wx@aol.com
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