The 70' of Rohn 45 in the catalog is guyed with 3/16" EHS cable and has
a base reaction of 3,470 pounds. If you go to a 300' tower the base
reaction is 14,520 pounds.
I think the guy wire size could be significanly increased with the
resulting increase in wind load capability at the top of the tower.
Please consult with a local engineer.
de n0yvy steve
Steven H. Sawyers PE
ARRL Volunteer Consulting Engineer
> In a message dated 97-06-17 17:24:57 EDT, you write:
> > >> Guyed Rohn 45, 70', 70MPH is only rated for 17.5 sq.ft.
> > >
> > > Actually, if you add in the 8.0 sq.ft. that Rohn has deducted for a
> > >commercial antenna mount, you get 23.5 sq.ft. Just FYI.
> > No, 17.5 is including the 8.0 side mount. Rohn specifies 9.5 sq.ft. in
> > the catalog.
> My mistake - I didn't look it up. For your example above (70' @ 70
> MPH), the Rohn spec shows 15.9 sq.ft. Adding the 8.0 sq.ft. already netted
> out gives you a total capacity of 23.9 sq.ft.
> The 9.5 sq.ft. figure you cite is in the rectangular box meaning that
> it is the figure for "flat member" antennas. You should more properly use the
> other figure, the one that is in the rounded box; this is the one for "round
> membered" antennas. Amateur yagis are round membered antennas.
> The only truly flat antenna that I've ever seen is a flat piece of
> material that is used as a microwave path reflector (it functions like a
> mirror and you can change the path with it). Every other antenna has been
> round membered (FM broadcast, cellular, microwave, paging, amateur, etc). My
> suggestion is to use the round member figure unless you feel for whatever
> reason that it isn't valid.
> 73, Steve K7LXC
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