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RE: rotator



Hi Ed,

Believe it or not, the setup works quite well, even with the lack of 
precision.  I found that the pot and weight method was less accurate due to 
the weight swinging in the wind, and the friction of the pot (which 
undoubtedly could have been improved).  My BBQ grill has a beamwidth that is 
a little wider than the 10 degree index granularity, so I can always find a 
reasonable place to point the antenna.

I definitely agree with the need to keep water out of the rotor.  The 
solution I employed was very low-tech:  a plastic bag wrapped over the rotor 
and secured with string.  It needs to be replaced about once a year, due to 
the sun.  Your mileage will vary depending on where you live.

Greg  KO6TH


----Original Message Follows----
From: "Ed Krome (K9EK)" <71611.76@compuserve.com>
To: "Greg D." <ko6th_greg@hotmail.com>
CC: "Ed Krome (K9EK)" <71611.76@compuserve.com>, 
amsat-bb@amsat.org
Subject: RE: [amsat-bb] rotator
Date: Thu, 9 Dec 2004 19:58:23 -0500

Message text written by "Greg D."
>
My Az/El setup consists of a pair of index switch-type rotors.  I don't
know
the brand for the Az rotor, but I am using an Alliance on its side for
elevation.  The controller is homebrew, based on a Basic Stamp.  A
discussion of the design and source code are at:
http://home.jps.net/~gregd/hamsite.htm.<

-----------

Thoughts on using the Alliance rotors (from 10 years with one as an
elevation rotor)
- Arrange it with the side hump down. Drill a 1/8 hole in the lowest part
of the side hump
so that any water that gets in through the antenna mast sleeve drains out.
The water
will get in.
- These things are really sloppy. Mine had at least 10 degrees of slop by
the time I
sent it away. You should have seen the antennas flop in high winds.
- Counterbalance the antennas. This hurts the sloppiness referred to above,
but
keeps the gears alive
- The clicker type position control is worthless at best. And gives 10
degree increments
when it works at all. Forget it. Hose-clamp a 1-turn ball bearing
("precision") pot to the
crossboom and hang a small weight on a few-inch long arm to the rotor. As
the cross-
boom moves the weight hangs down. Use all 3 wires in a bridge indicator
circuit, which
would probably work just fine in a fedback loop.
Calibrate it. Put a small Tupperware container upside down over it. The
first one lasted
for4-5 years in Midwest winters.
Or use a selsyn. Much better.
- They do work and are useful as long as your antenna beamwidth isn't too
narrow :-)

Good luck,

Ed K9EK
----
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