In a message dated 96-10-07 14:48:10 EDT, you write:
>I want to put up a conservatively rated 30 foot tower for satellite
>tracking (elevation and azimuth rotation) antennas and tower-mounted
>equipment. I live in Minnesota so 1/2 radial ice is part of the wind-load
>equation. In talking with Rohn, they say that for 80 mph, 1/2 radial
>ice for a self-supporting with a balanced windload on a 10 foot crossboom
>(minimal twist) with 25 sq ft of antenna would require 65G. However,
>they indicated that any rotor plate or thrust bearings would have to
>be custom.
Hi, Paul --
For a FREESTANDING tower with ice, the factory knows best. Adding a
housebracket changes EVERYTHING. For example, 40 feet of 45G bracketed at
30 and 15 feet comes in at 27.4 square feet with no ice at 80 MPH (you're in
an 80 MPH wind zone, BTW). Freestanding, it is only rated at 1.4 square feet
- big difference.
Forty feet of 55G in the same bracketed configuration is rated at 54.5
square feet with no ice. Freestanding the load spec is 8.0 sq.ft.
>The location is next to my house so, in theory, I could connect to the eve
>16 feet up with a house bracket. Of course, that requires some "enhancement"
>of the house's structure.
>
See Tony's, K1KP, recent article in QST on installing a
well-engineered housebracket that was PE designed.
I don't think you need 65G if you're going to housebracket your tower.
Do you have the Rohn catalog? All of this information is in there. TOWER
TECH has the Rohn Catalog available for $5.00 to cover S&H. There is a
little phamplet called "Manufacturer's Technical Information for Bracketed of
Self Supporting Towers" that has all of this info in a nutshell.
Apparently you didn't ask for a price on the 65G; if you had, you
probably wouldn't have posted this inquiry.
73, Steve K7LXC
TOWER TECH -- professional tower supplies and services for amateurs
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