I was also thinking about water piling up in the tower legs. I have seen
bases for Rohn towers that sit on top of the concrete foundation, and I
suppose the water if any runs out the bottom there?
The tower will be more than its height away from any lines. I have room
for about 2X. If the tower went towards the lines, it would land on the
house first. What I have is a 50x150 lot with power lines at the very
front, and the possibility to put the tower about 55FT from the back of
the lot. The "shack" is a 30x40 building at the back of the lot.
Here's my deal:
I really -need- a dipole of about 100FT length. The guys tell me it
needs to be 40FT high at the center and at least 20-30FT high at the
ends for the kind of propagation I can live with.
I really -want-:
stacked 6M beam, 2M beam, 440 beam
225-400MHz discone,
108-140MHz discone.
- and I don't think I can put those on the center pole with the dipole!
But they need to be up at least 25-30FT and that would be mediocre
because my site is in a slightly low lying area with alot of trees. Some
of the trees are going to be whacked soon. Of course I could put up a
small pole farm, and get away with alot of this, not sure about the
beams on a push up pole with a rotor, that is a bit heavy.
My total budget is about $1500 (less the antennas, co-ax, etc)
Patrick
Jim Hoge wrote:
> Patrick,
>
> There is another issue you must contend with- drainage of water and
> condensate from the tower legs of any tubular tower. I am a tower monkey in
> the DFW area and I cannot begin to tell you how many freeze splits I have
> seen in the tower legs because of inadequate drainage. I removed one Rohn 25
> tower that was very similar to what you have proposed. The tower base was dug
> down about 2 1/2 feet until the caliche was hit. The tower legs rested on the
> caliche rather than a bed of gravel and the concrete was poured. The freeze
> split on one tower leg was 4 1/2 feet above ground, far above the normal 1
> foot I see in the area. Rohn specifies a gravel bed for drainage for this
> very reason. By only digging down until you hit the caliche, you are
> compromising the mass of the base and if you put in the gravel, even more so.
> The caliche can be dug out with effort, something you will need to do for the
> guy posts anyway. A hammerdrill can be used to to start a hole and once you
> have an
> area to break off the caliche into, it will break. One step up the tool
> ladder is a demolition hammer. The bottom line is don't cut corners on the
> installation. Follow the manufacturer's specs. They are there for a reason.
> If you can't make it work, don't guess, get a engineer involved. BTW, do you
> have overhead powerlines or a drop nearby? My personal safety factor is 2
> times the height of the tower to the nearest line.
>
> 73 es gl,
> Jim W5QM
> _______________________________________________
>
>
>
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>
>
--
kind regards,
Patrick Jankowiak
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