[TowerTalk] TowerTalk] Rohn 45

[Chuck Smallhouse]

Gary, Jim,

Yes the strut "guying" is the way to go and also not only provides 
the strongest support but also occupies the least amount of ground 
area, as well as the least interference with your array.  I dare say, 
with your planned medium sized 6M array of four yagis, that you might 
not need to replace your Rohn 25 with a 45, using this technique.

More than thirty years ago Lance, (now W7GJ, MT) installed a large 2M 
array using 16 long yagis (30' each?) on about a 30' tall Rohn 45 and 
supported that structure with three, about 20' long, pieces of 1 1/5" 
black pipe.  They were attached about 2/3 the way up the tower and 
about 10' away from the base.  It's still up and has considerably 
more wind loading than your 6M array will have.

I used his work/ideas for my own R & C, EME array project, consisting 
of 8 very long 2M yagis on 30' of Rohn 45, again a higher wind load 
than your array.  Instead of black water pipe, I used the top railing 
material for chain link fencing.  It's about 1 7/8" in diameter and 
relatively thin wall and light, but quite strong.   It comes in 
either 20' or 24' lengths  The top of this tubing was attached at 
about the 20' position on the the 45, using HB saddle mount brackets 
attached to the tower legs with U-Bolts.  The bottoms of these 
struts, using similar brackets, were attached to two 18" "J Bolts" 
set into concrete pillars in the ground.  These pillars were about 
14" in diameter and no more than two feet deep, and placed less than 
10' away from the tower center. This close in spacing easily allows 
the clearance of your 6M yagis when they are being elevated.  This 
array was up for at least 12 years, until I moved to this AZ QTH.

BTW, R & C stands for:  Research and Copy !

If you still want to use Rohn 45 replacement, you can consider using 
a large steel plate (3/16" to 1/2" thick) welded onto the Rohn 25 
stubs extending from the existing base.  This base plate needs to be 
and large enough in diameter, to weld the base of the 45 to, and also 
to weld strengthening stiffeners. These can be steel angle of at 
least 2" on a side, along it's outside edges to prevent oil can 
bending of the plate.  Don't ask why you need to do this !!

I have done a similar installation, to my N. CA one, at this QTH, to 
support 16 of my now 28' boom 2M yagis.

GL es 73,  Chuck,, W7CS