In a message dated 3/15/2006 1:03:33 P.M. Pacific Standard Time,
towertalk-request@contesting.com writes:
> We have an opportunity at WP2Z to put up another tower. The owner of the
house would like it to be free standing. We would like to put up a 70' tower
so we could raise the height of the 40M beam (Cushcraft 402CD is presently
at 35'). Also it would give us a higher support for 80 and 160M wire
antennas. The only experience I have had with free standing towers is the
35' aluminum Universal tower that is holding a C3E. It used to be 45' high
till a hurricane several years ago came along and ripped off the top 10'
along with the tribander and rotor and proceeded to deposit it in small
pieces a few hundred yards away.
> WP2Z is at 900' - one of the highest points on the island. And we are on
solid rock. So it will be fun to get a base dug. This QTH gets high winds a
lot. We have trouble keeping any kind of tribander on the one tower due to
the high updraft that occurs almost every night. The new tower will be about
100' away where the updraft doesn't typically occur.
You don't have to excavate for the base if it is solid rock - that'd be
a waste of time since you're just going to fill it back up again with
concrete. Drill some holes for the anchor bolts with coring bits and then
either
epoxy in the anchor bolts or use rock expansion bolts. Both have plenty of
strength.
> My questions to the group are:
> - Am I foolish to try to put up a 70' free standing tower at such a
location?
Why would it be foolish? It's just another tower - you can't have too
many of those - hi.
If you're worried about the wind, just build it hell-for-stout realizing
that there is some pretty good wind exposure which you're subject too
anyway.
> - If not what's recommended for this kind of environment especially being
so
close to salt water? I was looking at Universal Towers HD21-70, Trylon
T500-72, T400-72, AN Wireless HD-70. Are these overkill or fine or
substandard?
The Trylon is a pretty good value for a medium-duty tower - it'll
take 6 square feet @ 100 MPH. The AN towers are pretty strong - and
commensurately expensive. I'm personally not a fan of aluminum towers since
they are NOT
commercial grade.
If saltwater is a problem, I'd put another finish on the tower in
addition to the galvanizing. They make industrial epoxies that do a real good
job
of sealing them up.
Cheers,
Steve K7LXC
TOWER TECH -
Professional tower services for amateurs &
Champion Radio Products
_www.championradio.com_ (http://www.championradio.com)
Cell: 206-890-4188
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