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[TowerTalk] 40 meter problem

Subject: [TowerTalk] 40 meter problem
Date: Tue, 10 Jan 2006 09:11:03 -0600
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Greetings fellow TT members,


I may have posted something about this before but I have a situation in
which I am looking for a creative fix this time.  It is my OptiBeam OB17-4
beam.  For about 2 months now the 40 meter portion has an intermittent
problem. When it hits the SWR spikes to about 2.5 or 3 to 1 and it is
normally flat.  The other bands are not affected. I have it set in the CW
portion of 40 meters.  When it acts up (not very often) I can begin to
rotate the beam and as soon as it starts to move the problem corrects.  I
have tried to track when and how it happens and can find no definite
pattern.  The 40 meter section has 3 elements.  The driven element has been
taken down and checked carefully.  Tom, the owner of Optibeam suspects it is
something loose in the reflector.  


The Optibeam is a 17 element beam and it is on a mast with a Force12 WARC-7
about 12 feet above the Optibeam.  The tower is a Rohn 45G - 80 feet.  (78'
actual with about another foot or so to the antenna boom).  


I first happened when the temp dropped to 8 degrees F and it does not happen
(that I have noticed) when the temp is warmer.  That would lead me to think
one of the element transition bolts have come loose?  An intermittent
problem is so difficult at times to trace.


To take the antenna down to the ground and check everything would mean I
bring in an expensive crane.  However, I can get a bucket truck for much
less money.  The antenna weighs 215 lbs and is on a 40 foot boom so I don't
want to risk using a bucket truck to bring the antenna to the ground.
However, the bucket truck (antenna is 80 feet up) could take a person up to
the reflector and director to allow work up there.  If it is something
simple like a loose bolt it could be fixed from there.  However, if it is
still not clear I am wondering about a creative fix?  What if each joint
were taped with aluminum tape?  I could cut it to about 1 inch strip and it
weighs almost nothing.  Then if there is some odd temperature related
movement between any of the transitions that would fix it I would think?  Or
is this a crazy idea?


Lastly, is there someone on TT that is comfortable working from a bucket
truck at the 80 foot level within easy driving distance?  I am about 70
miles North of Dallas, Texas.  I can rent a bucket truck that goes to 103
feet so at 80 feet I would think it is quite stable. I am not physically
able to do that work myself.  So, is taping the elements a crazy fix or a
reasonable idea?


The other idea is to get a new radio - a Ten Tec that handles 3 to 1 SWR
without any problem :-)  Anyone have an Orion for a good price?


Thanks for your input,


Gary, N5PHT



Gary Stone, BA, LCDC

Case Manager, Bonham DSAP

Sam Rayburn Memorial Veterans Center

(903) 583-6411




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