[AMRadio] New Tower

[Jack Schrader]

I have a Rohn tower at 100' with a 7 element tri-bander on top.  I would not 
try to tip up more than 20' of tower as it is hard even with the building in 
the way, to stop the inertia from keeping the tower and antenna from moving 
once it is in motion.

I agree the putting the rotor down near the ground is a good idea if for 
nothing else it makes servicing  it easier. Also wherever you put the rotor 
be sure to have thrust bearings at the very least at the top and also half 
way up. This takes some of the vertical load off of the rotor.

Rohn did publish a tower manual, I have one, and I can look up specific 
questions. I could also get it copied if you want to pay the cost of copying 
and postage.

73   Jack

-----Original Message----- 
From: Rick
Sent: Friday, April 29, 2011 10:08 AM
To: 'Discussion of AM Radio in the Amateur Service'
Subject: [AMRadio] New Tower

I am erecting a new 40’ Rohn 25 tower and need some advice on how much
stress it can take while standing it up. My tower climbing days are well
behind me, so, that is not an option. I have the hinged base mounted in a 2
½’ X 2 ½’ X 3’ deep rebar reinforced block of concrete. I have a sturdy wall
bracket at about 12’ on my shed to which the tower will be mounted. I am
undecided about guy wires at this time since less than 30’ will be
unsupported. I am installing a Cushcraft A3 tri-band beam about 5’ about the
top section. The rotator will nest inside the tower. With that said, my
question is:

If I put a compound rigging with one set of pulleys attached to the shed and
the other attached to the tower, where would be the best place to mount the
tower pulleys to get the greatest leverage for lifting and still provide
adequate support for the tower as it is being raised? The tower will not  be
lying flat on the ground, of course, due to the size of the antenna. I
assume a location above the center point of the tower would be best, but how
far above do I put the pulleys without endangering the integrity of the
tower?

Thanks,
Rick/K5IAR


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