Re: [amsat-bb] 2.6 FODTRACK Board Questions

["George Hoffman" <rainbow@xxxxxxxxxxx>]

See below-  This info was received from Manfred  XQ2FOD some time ago.


> There was a post a while back that addressed a problem of rotor
> "oscillation" -
>
> >"Den Spiess" <dspiess@t-3.cc> wrote:
> >Date: Sun, 3 Jun 2001 05:44:01 -0400
>
> >I just made the FODTracker board to control a G-5400. Currently just
using
> >the FODTrack 2.6 software to 'test' the circuit.
> >The azimuth rotor moves to the correct position the oscillates back and
> >forth about 5 degrees. The elevation side works OK.
> >The board looks like everything is in place. Switching the rotors gives
the
> >same response using the elevation rotor on the azimuth side.
> >Anyone have any ideas or has seen this?
>
> I don't remember seeing a reply to this query,  but there is an adjustment
> that can be made as per the documentation.  It requires adjusting the
> "dead zone" by changing the value of a particular pair of 1 megaohm
> resistors.
>   There are 4 of these resistors in the circuit (located at U2A and U2B).
> My question is, which ones change the gain, or "dead one"?


On the elevation side the one that defines the dead range is the 1 MEG
resistor  between pins 6 and 7 of U2B .  The resistor at pin 5 compensates
so that the overall range spread is correct.  Suggest you replace the one at
6 and 7 with 470 K for a 3 deg. dead range.  You could go lower.  when you
get it right you can replace the one  tied to pin 5 with one of equal value.
The Azimuth side works the same way.  It is a very solid tracker.  I use it
with the 'Station" program.    Good luck!

George

W2CID

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