In a message dated 6/11/2008 2:19:18 P.M. Pacific Daylight Time,
towertalk-request@contesting.com writes:
> I am getting ready to install 90' of Rohn 25, base section is all
done,concrete etc and so are the guying stancheons that are set in concrete
as well. I
have the first 10' up and hopefully in a few weeks or so will be ready for
the rest of the installation. My question is what is preferred, steel guying
cable or Phillystran cable. One of my concerns ( maybe it should not be) if
I
use steel guying installation, should I be concerned about resonance based
on
the lengths of guying cable. The tower will have a 4 el steppir at approx
98',
below that there will be a 3 element 40 meter monobander, prosistel rotator
and fed with LMR400. Will I need to break up the guys? It seems like it
would
be a lot of work if I had too or should I just go for the Phillystran and
don't be concerned. This is my first guyed tower as I have always have had
crank ups. I have seen a lot of pictures that have been on this forum and
was
wondering what most everyone else uses for guying their towers. The guying
lengths will be as per Rohn specs, 80% of total height to calculate guys
lengths.
FIRST THINGS FIRST. Litchfield County is an 80 MPH windspeed zone. Your
local building department may have it rated higher. Nonetheless 90' of 25G @
80 MPH is rated roughly at 10 square feet of windload. You have already
exceeded the rating so feel free to reevaluate your proposed installation.
Personally there's no way I'd install a 3L 40M beam on 25G unless it was a
Force 12
version (which IMO doesn't work that great anyway).
And don't violate the LXC Prime Directive to "DO what the manufacturer
says" without being prepared to suffer the consequences. (I just made a post
on an insurance topic which means I can do the insurance estimate for you if
you ever need it.)
Guy material post to follow.
Cheers,
Steve K7LXC
TOWER TECH -
Professional tower services for hams
Cell: 206-890-4188
**************Vote for your city's best dining and nightlife. City's Best
2008. (http://citysbest.aol.com?ncid=aolacg00050000000102)
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