[AMPS]

[K0FF]

Ron, I get some nice 12VDC gearmotors from Gateway electronics. Simple way
to get position feedback is with a 10 turn pot ganged with the cap/inductor
shaft. Automatic tuning can be implemented by having that pot feed a
balanced bridge. Otherwise just have an analog or digital meter readout.
Another idea is to gang a long leadscrew to the shaft and have it run a nut
back and forth along with the rotations of the cap/inductor. You can fix
microswitches so that when the nut is near the end of the travel it will hit
the switch and keep you from over spinning the device. Another slick way to
accomplish end-of-travel limiting is to install a planetary reduction drive
on the shaft. Don't bolt the reduction drive to anything, and this way it
will act as an overrunning clutch. In other words when the end of travel is
reached it spins around on itself and removes the torque from the shaft.

Good luck. Mechanical assemblies and parts are getting harder o find all the
time.
Geo>K0FF
-----Original Message-----
From: rb <rbigg@pcola.gulf.net>
To: amps@contesting.com <amps@contesting.com>; antennas@qth.net
<antennas@qth.net>
Date: Monday, August 28, 2000 4:21 PM
Subject: [AMPS]


>
>Here's the deal:  need something to act as a primary actuator and driver
for
>rolller coils and a vacuum variable.  The problem with trying to find and
>use an AC and/or DC motor is that few if any meet the basic criteria:
>
>a.  be reversible
>b.  have plenty of shaft torque
>c.  be very slow rpm (can, of course have a reduction gear drive)
>
>One of the things that looks promising is a tv rotator control unit with
>indicator box.  The shaft size coupling/adapter is not a problem.  That can
>be accommodated.  These things have lots of torque.  They have a feedback
>cirucit and indicator to tell you where they're at.  They're reversible.
>
>Comments?
>
>73 de Ron, K5BDJ
>
>
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