[TowerTalk] Rohn 45 tower

[Pete Smith]

At 09:15 PM 8/30/03 -0500, P. Marlow Miller wrote:

>         I'm writing to the list as I have no practical experience with 
> any type of
>towers.  I picked up 6 ten foot sections plus the top section of Rohn 45.
>The use of this tower is for a small microwave antenna to reach a cell phone
>tower about a mile away.  I live in a heavily wooded area and the only way
>to get high speed internet is this microwave link.  I was told when I bought
>these sections second hand that I could go up to 55 feet without guide
>wires.  I am going to need to go up to 65-70 feet to clear the tree tops.  I
>was told initially to dig a three foot deep hole, three feet in diameter and
>drop one section in and fill it with concrete.  It's been pointed out to me
>since then that up here in the great white north (Minnesota) that three feet
>is not deep enough to get past the frost line.  I'm looking at going 5-6
>feet deep.  This will leave me about 55 feet of tower and I'm looking at
>putting a single stick for the rest of the distance to clear the tree tops.
>
>         I plan to put the tower at the end of my house, which I would be 
> able to
>secure the tower about 20 ft up to the side of the house. If I tie it to the
>side of the house would I still need to use guide wires?  Or would this be
>enough to keep the tower secure?  Any help or suggestions would be
>appreciated.
>

How much wind area does this microwave antenna have -- is it a dish or a 
Yagi type?

My Rohn catalogue does not provide data on the height versus wind area 
calculation for self-supporting Rohn 45, nor does it detail the size of the 
base that is required.  Both are critical, particularly the latter, because 
ALL the loads of a self-supporting tower are taken by the base.  Bracketing 
to your house can reduce the amount of base (and the amount of tower that 
needs to be unguyed, but then significant loads are transferred to the 
house structure, so the connection needs to be done with care.

Others may provide the info you need, but if not, I believe this subject 
has been covered in detail in the past on this reflector.  If you go to 
www.contesting.com, look in the left margin for a box labeled "list 
search," and provide Rohn 45 and self-supporting as search terms, it will 
find whatever has been written on this topic for as long as towertalk has 
been around.  A second search on bracketed or house bracket will get you 
info on those topics as well.


Best regards,

Pete Smith N4ZR