what sort of adjustment speed do you need. A 8 or 16 pulse per rev disk and
an optical encoder driving a suitable low impedance device (open collector
type scheme) or even 8 magnets and a reed switch, might work just fine. RF
immunity is more a matter of reasonably careful design, particularly for a
low rate pulsed/contact closure type signal.
If you want something more elaborate, you could make a standalone little
controller using a PIC or Rabbit, driving a suitable motor with encoders,
that all sits inside a metal box on the cap, and you use optical fiber (or,
at least optical isolation) to send control signals/telemetry back and
forth. Or, put all the electronics in a box and use a dielectric rod through
a hole in the side of the box as your actuating shaft.
----- Original Message -----
From: "Dennis Ashworth" <K7FL@arrl.net>
To: <towertalk@contesting.com>
Sent: Saturday, July 26, 2003 9:14 AM
Subject: [TowerTalk] Motor drives for vacuum caps
>
> Has anyone discovered a reliable scheme for remote adjustment of vacuum
> variables? I have two antennas with vacuum variables at the base and would
> very much like to tweak them from the shack. I'd need the ability to
> reverse direction and ensure I didn't go beyond the acceptable travel of
> the capacitor (maybe some limit switch or turn counter arrangement?). I'd
> prefer to stay away from LED/encoder wheels, etc in my high RF
environment,
> but that may ultimately prove the best solution.
>
> Ideas welcome!
>
> Thanks,
> Dennis, K7FL
>
> _______________________________________________
>
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>
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