In a message dated 99-06-20 22:18:01 EDT, firstname.lastname@example.org writes:
> Finances aside when building a tower, I am planning on putting up a
> GM Enginnering RT-424 (the 4.5' model -- hope the model # is right)
> with a Cushcraft A3S on top of it.
> Both Cushcraft and GM say that this is an acceptable combination
> the mechanical specs of the A3S and what the tower is rated for, my
> windzone of 70MPH. The caveat of course is I must meet or exceed their
> installation reccomendations (which I of course intend to do...)
> Does anyone feel I'm in left field here....? I know that one of the big
> rules is following the manufacturer's specs and they're in agreement with
> what I'm doing but I'd like some opinions on this....comments?
Sounds okay to me. I've installed over a half dozen GME roof towers and
they can be sturdy antenna supports if installed properly. The roof-top tower
is rated at 6 sq.ft. @ 87 MPH so you're not violating anything I can see.
The crux of course is anchoring the tower to the roof. I don't use the
lag screw method that the GME tower feet are drilled for. Rather I use one
piece of all thread that goes through the foot and roof and then through a
backing plate inside the attic. This gives you a roof truss sandwich with big
washers and nuts on both ends. If you're not sure that the roof structure is
strong enough, add some more braces and reinforcing. The forces and bending
moment of your proposed installation is reasonably small so adequate
engineering should be easy.
The majority of roof mounted systems I've installed have been the
9-foot tower and a Force 12 C-3, C-4, C-3SS, etc. This system has the
potential to perform better than your proposed system so would be worth
Cheers, Steve K7LXC
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