My original post was:
I need some advice from the tower gurus. I am planning on erecting a 50 foot
Rohn 25 tower on my city lot in such a way that will require one anchor point
to
be the house itself. I am looking for advice from someone that has done
something similar and opinions from anyone else.
Here's the deal. The lot is 160x90 feet and is relatively flat even though
this is a
mountainous area. To keep neighbors and wife somewhat happy with this setup I
have decided to locate the base at the side of the house along the centerline.
This
puts it 25 feet from the side lot line. The house is a rectangular two story.
(32x26
feet and 27 feet tall at the peak)
The Rohn book calls for two sets of guys at 23 and 45 feet. For the lower guy
point I thought I would use a house bracket and reinforce the attachment point
similar to this month's QST article written by Tony Brock-Fisher, K1KP. For
the
top guys I will run two wires away from the house to elevated guyposts. The
third guy will run back inline with the peak of the house. I propose attaching
it to a
mast that runs vertically down through the roof peak. The mast will sit on an
assembly of wooden 4x4s that are attached to the ceiling joists and rafters.
Suggestions on mast material and diameter? No waterpipe, right? It would
probably be
6 feet tall.
I haven't heard of or seen a setup like I have suggested but it seems like it
would
be safe if properly designed and constructed. Your thoughts?
***************************************************************
I asked for advice and I got loads of it. Thanks to all that contributed. I
haven't made up
my mind about the setup to use but here some of the ideas presented:
1. Don't go through the roof of the house to guy the tower because:
*The chance of causing a perpetual leak is always there.
*A lightning hit could be conducted into the house.
*A professional structural analysis of the anchor support will probably be
needed.
*Insurance companies may take a dim view of this method if damage does occur.
2. Try to avoid using guys and go the self-supporting route if possible. A
number of
hams use Rohn HDBX towers and I think most ignore the 10 foot boom limitation
set
by Rohn. As I understand it that type of tower is susceptible to twisting
failure. I live
in the mountains of Idaho and as Steve, K7LXC, pointed out this area is a low
rated
75 MPH region but I am more worried about the squirrely winds around here. I
seem
to get strong gusts from different directions quite often. Another suggested
putting up
50 feet of 25G without guys but with an oversize base. It works for him. Sorry
but I
don't have the guts to do that.
3. Another approach suggests that since I'm not going that much above the roof
I could
just rely on the reinforced house bracket in the attic and have 23 feet of
unsupported
tower above the house bracket. Doing this with 45G would be the preferred
solution.
( The top house bracket will be at 27 feet) Tony Brock-Fisher's August 1996
QST
article is the basis for this solution.
4. Another solution was to use a 4 guy system. That would clear the house but
I would
run into a garage on the other side. My wife would put up with 3 guywires but
4 is
probably unacceptable.
So I'll probably go with idea number 3. If I use 25G then I can get an antenna
up right
away. If I go the 45G route then I'll end up with a tower only because of the
price
differential. The antenna will have to wait.
Anyone know where to find 45G sections in southeast Idaho?
Thanks again for the help
Bill Frede AA0WO
Pocatello, ID
bfrede@poci.amis.com
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