> Date: Sun, 13 Jul 1997 02:09:57 -0700 (PDT)
> To: Bruce Makas <firstname.lastname@example.org>
> From: email@example.com (Stan Griffiths)
> Subject: Re: [TowerTalk] stacking antennas & Rohn specs
> Cc: firstname.lastname@example.org
> >I am installing several Rohn towers and want to stack antennas on the
> towers. Being a "good" amateur engineer, I intend to follow the specs in the
> Rohn catalog. My question is about the allowable projected area that is
> called out by Rohn. For example, if I were to put up 130 foot of Rohn 45G in
> a 90 mph area (coastal Maine), the book says that 12.3 sq ft of projected
> area of round elements is allowable (C870478R1). I assume that is at the top
> of the 130 foot tower.
> >Now, I want to stack antennas; say one at 60 feet, one at 100 feet and one
> at 130 feet. How do I calculate what is the allowable sq footage? Is it as
> simple as summing the moment arms (height x sq ft of each antenna compared
> against 130 ft x 12.3 sq ft) or is it more complicated?
> >For example, a 205CA specs out at 9 sq ft, I would hope that I could put at
> least three of these, and 3 155CA's (5.2 feet each) on the tower, but it
> doesn't look it.
> > ((60x9)+(100x9)+(130x9)) > (130x12.3) ........... for just the
> > 205CA's
> >If this is true, how can anyone stack more than 3 large antenna's per
> tower? Even a 55G installation only allows 14.8 sq ft @ 130 feet.
> >What am I doing wrong?
> >Thanks in advance for your ongoing support of my antenna project. 73, Bruce
> Hi Bruce,
> I have yet to meet the guy on this reflector who will admit he knows how to
> properly answer your question. Rohn can answer it for you but it will cost
> you lots of money, somewhere in the thousands of dollars. It takes an
> experienced structural engineer to really engineer a project of the kind you
> are describing.
> But, you say, you know other hams who have put up such installations. How
> did they determine they were safe? I'll bet they didn't. Most of them have
> looked at similar installation that have been up a long time so they used
> them as good examples. They have also studied all the data they could get
> on failures so they would know what to avoid doing. You either have to step
> up to a large engineering bill or take some risk. Studying what has worked
> what hasn't will minimize your risk.
> Good luck.
> Stan email@example.com
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Since I have addressed this before I will be brief: on a 190ft rohn
45 i have 2 5 ele 20m - 44 ft boom es 3 4 ele on 26 ft booms; on a
rohn 25 180 ft i have 2 6 ele on 40 ft booms and 6 4 ele on 22 ft
on 10m i have 4 6 ele on 26 ft booms- on 40m full size 3 ele over
a klm 4 ele on a rohn 45 up 170 ft--- my point is simply to say
these towers will hold up much much much more than you would expect
with proper guying... no engineering-- i just keep adding antennas
73 es have some fun
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