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RE: Portable AZ-EL Rotator?

 > From:          Mark Fossum <mark@willetransport.com>
 > To:            "'Roy Welch'" <rdwelch@swbell.net>, Carl Lefebvre <Carl2@gte.net>
 > Cc:            AMSAT BB <amsat-bb@AMSAT.Org>
 > Subject:       RE: [amsat-bb] Portable AZ-EL Rotator?
 > Date:          Tue, 17 Aug 1999 17:14:10 -0500
 > Organization:  Wille Transport, Inc.

 > I've always wondered if it would be possible to homebrew a small AZ/EL for 
 > arrow style antennas out of those little electric srewdrivers that Black & 
 > Decker sells for $14.95. The gearing is almost perfect if it were combined 
 > with a screw gear. But then there's the control side and I'm not the one 
 > for that job.
 > Come on guys! This would make a nice project article in the Amsat Journal!
 > Mark

Dear Group,

Electric screw drivers are used for remote tuning of a popular mobile HF antenna.
They work so well that the antenna itself is refered to as "screw driver!"  The first
application that comes to my mind is elevation control.  The screwdriver would be
used to turn a threaded rod, making a simple linear actuator.  

I have used this method for elevation control for years on my AO-10/13 array.
In my case I used a linear actuator off of a old TVRO dish.  It runs on 24 VDC
and direction is controlled simply by reversing the polarity.  The screwdriver
due to its lower power would be even easier to control with a simple "H"
bridge circuit.

I'm surprised that TVRO linear actuators are not used for elevation control.
Mine can lift 200 pounds with no strain at all!  They are simple and cheap at
hamfests.  It was easy to connect by means of a simple crank arm to my 
dialectric cross arm (made from a pressure treated wood 2X4).  Two metal
door hinges (big ones) allow for rotation through 90 degrees.  None of this
takes any fancy metal work or special tools.

Azmuth is a little more difficult.  I use a old Ham-M rotator and it works fine.
I also have some simple (but clever) metering designs for the indication of
elevation and azmuth I might publish some day.

--73-- David WA0AUQ

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