[TowerTalk] new member with tower question

[Patrick J. Jankowiak]

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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