Steve (K7LXC) wrote:
> My first question is what heights it's going to be housebracketed at
> and how much tower will be above the top bracket (Rohn specs call for 2
> brackets)? The Rohn specs allow 14 feet above the top bracket and will take
> aproximately 30 square feet at 75 MPH. (Obviously you can go up a little
> higher
> while de-rating the capacity.)
Yes, Rohn 45G specs call for two brackets. For a 50' tower, upper at 36' and
lower at 18'. For 80 MPH wind, this supports 25.9 sq. ft. of antenna area. The
top bracket will be about 26'. This would put the tower height at 25' above the
top bracket and we will have < 8 sq. ft. of antenna. The wall is heavily
reinforced and we will be putting steel plates on the back side of the wall
supporting the brackets.
Thanks,
Kevin.
------------------------------------------------------
Kevin Hemsley
kev@ida.net
NF7J
----- Original Message -----
From: K7LXC@aol.com
To: towertalk@contesting.com ; kev@ida.net
Sent: Thursday, June 15, 2006 10:20 AM
Subject: Re: [TowerTalk] Bracketed 45G
In a message dated 6/14/2006 3:50:27 P.M. Pacific Daylight Time,
towertalk-request@contesting.com writes:
> I am working on plans for a 50' bracketed Rohn 45 tower. In going through
the Rohn catalog looking at foundation drawings for Rohn 45 bracketed
towers, you can either use a base plate or plant a tower section in concrete
for the foundation. Is there a reason not to use one method or the other?
This tower needs to be unguyed and will be bracketed to a brick building for
a community installation. The county wind rating is 75MPH. The antenna load
will be less than 8 sq feet. The top bracket will need to be a little lower
than the Rohn specs. 45G was selected over 25G because of this. Any
recommendations or caveats are appreciated.
My first question is what heights it's going to be housebracketed at
and how much tower will be above the top bracket (Rohn specs call for 2
brackets)? The Rohn specs allow 14 feet above the top bracket and will take
approximately 30 square feet at 75 MPH. (Obviously you can go up a little
higher
while de-rating the capacity.)
In my experience, having the bottom of the tower in the concrete is
much more stable than bolting a baseplate to the concrete but since the
brackets will be taking the side forces, it doesn't make much difference
which way
you go.
Cheers,
Steve K7LXC
TOWER TECH -
Professional tower services for hams
Cell: 206-890-4188
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