Forget about it....all you are getting is headaches and hassle
bycomplicating a system that does not have to be complicated.
Find your unused compass area (probably to the south) and mark your control
box meter with a "dead zone" - just don't go there...and if you do - since
you were wise enough NOT to pin the mast in the rotor all that could happen
is the mast will slip in the rotor and now be pointed in a direction other
than it should - a quick climb to reset it and you are done...
Rotors operate at 1 RPM the "perception" of slamming into the side of the
tower is over - rated. I have been turning beams on gates for years with
no reprecussions other than having to re-point them occasionally...
A bigger issue is ensuring you have the mechanics of clearance down
properly - the offsetting effect of the gate at one point makes the antennas
center less, and another more, than if the antenna were rotating about a
thorecitcal point in the middle of the tower...do some scale drawings on
your puter - or graph paper - you will see!
Sometimes it is necessary to move the center of balance of the antenna
slightly to allow the portion of the boom with no elements to be next to the
tower to be clear during its rotation....my favorite trick for balancing a
2" boom is to slide a piece of 2" PVC pipe over the boom on the side that
needs to be weight-enhanced...you can tezst the size and effect by taping
that piece below the boom to make sure you are getting the desired effect.
Be careful when you do this however as you will change the turning radius -
it is NOT measured from the center of the tower on a sidemount and the
resulting geometry is actually quite complex....once balance and anchoring
point is established then use a tape measure to find the distanc from THAT
point to the farthest element tip - usually a reflector but sometimes with
re-balancing could be your front director! YOU ARE NOT DONE YET....Then you
use that dimension as an add on to the amount of offset the sidemount
adds...but it doesn't do it in the same plane...so like I say draw it out
and you will see....you can do quick calcs on whetehr an antenna will fit
beneath your guy wires but when you start rotating things you take it to a
whle 'nother level!
Simple side mounting works good - it is basically a simple install - just a
few bumps on the way!
ON A RELATED SUBJECT:
I have bartered for some 2" aluminum electrical conduit and was debating
making a side arm assembly out of it...the guy I am abrtering with also does
heliarc welding...is it worth having him heliarc the intersections of the
vertical and horizontal components or should I just fabricate plates with
u-bolts to do this? Relative strength...would it be greater? I could avoid
worrying about all those new u-bolts at each intersection loosening upover
time...thoughts?
K4OJ
----- Original Message -----
From: "Chuck Sudds" <Chuck@dxham.net>
To: <Towertalk@contesting.com>
Sent: Tuesday, May 21, 2002 6:01 PM
Subject: [Towertalk] Swinging Gates
Greetings TowerTalkians!
After considering the pros and cons and expenses involved with the
"Christmas Tree" stack that I was thinking about doing a few days ago, I
think that I have decided on simply adding a triband yagi, such s a C3 or
XR-5, on a swinging gate assembly, at about the 60ft level of my Rohn 45G.
My question is: Since I will only have about 300 degrees coverage, is
there any modifications that one can do, and are they published, as far as
limiting the travel of the CDE series of rotors, such as the Ham IV, T2X,
etc.??? I would think that moving the limit switches would accomplish this
purpose. I would hate to try to turn it too far!
Thanks again!
Chuck KØTVD
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