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Re: Driving two rotor sets



Hi Jim,

The previous version of my Uni_Trac system allowed independant
and or coupled tracking of an HF beam azimuth rotator. The demand
was so small that the feature was discontinued.

Despite all my experience in this area
I was never able to get two seperate Az/El mounts to track in sympathy.
In most trackers on the market there is only one set of sensing arrangements
measuring the feedback or angular position of the rotators. That being the
case then only one "feedback set" of say the master mount can be used.
As you point out the slave mount has to be positioned manually and
accurately to the master bearings and is outside the feedback loop. The
tracker has no idea where it is at.. I could NEVER get less than "very
flaky"
operation with this method and some quite disastrous events at times before
they started to put limit switches in the rotators..

You could of course multiplex the two mounts. I dont know how you
would automate the muliplexing rate from KCT, but it could be done
simply by hand.. All that is needed is a 12 pole change over arrangement
(relays preferably) where the entire wiring to each G-5xxx rotator set is
routed to one controller.
Some sort of logic is required to prevent the relays switching to the other
rotator set if motor drive voltages are being applied. This can be sensed
from the
8 pin Din on the  rear panel of the master controller, by sensing the up,
down,
right, left pins  which go to a LOW level when motor drive is required.
 In other words despite changing the muliplexing switch over,  the slave
or master can only read "feedback/s"  and apply motor correction AFTER
 its opposite has STOPPED.

There is a minor problem in that ONLY ONE of the rotator sets can be used
for calibration, however I have never ever lost satellite downlink data due
to slight, or even quite large calibration errors. We are not talking laser
beam alignment here. With a little patience the two mounts could be
reasonably calibrated to the mean of the two.

de
Dave Lamont       ZL2AMD

                     Uni_Trac 2000 Tracking and Tuning System
                                  www.qsl.net/zl2amd/

----- Original Message -----
From: "Jim White" <jim@coloradosatellite.com>
To: <amsat-bb@AMSAT.Org>
Sent: Friday, December 08, 2000 6:42 PM
Subject: [amsat-bb] Driving two rotor sets


> Anyone have any really good ideas about how to drive two Yasu az/el rotor
> sets from one KCT, or slave two G-5400s together?
>
> Antennas for 7 bands just won't fit on one rotor :-)
>
> Seems like, if the KCT will safely drive two relays, one could just build
a
> cable that added the relay control wires (only) to the second rotor
control
> box.  As long as they started in the same spot wouldn't they track
together?
>
> Will any of the current rotor control boxes do this the right way (looking
> at position and driving both independently) ?  Seems like a PIC or Atmel
Mc
> with a dual channel DAC could be programmed up to do this easily. . .
>
> Jim
> wd0e@amsat.org
> jim@coloradosatellite.com
>
> ----
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>

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