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Re: RF and FODtrack

Lawn, Richard wrote:
> Anyone experience any problems with ARF getting into the FODtrack
   box and creating some havoc? Any solutions? System seems to be
   working well now with FOD and SatPC32, aside from the RF problems.
> Rick
> ----

Hi John.  Yes, I had some difficulty with the FodTrack when I first
put into service.  The problem was RF getting into the box down the
rotor lines.  Put ferrite beads on all the rotor connections but
especially pins 3,4,5 and 6.  In addition, put a tiny capacitor say
220 pf to 1000 pf on these lines directly on the trace side of the
board.  There is plenty of room as a ground trace surrounds the board.
      Another modification was to put 0.1 ufd caps from pin 6 on U2B
and pin 2 of U2A to ground.  This does two things:  It will bypass
any RF getting to the OP-AMP, and slows down the feedback time from
the Az-El pots a bit.  When pots get dirty they can cause the relays
(if you use them) to chatter or SCR's to trigger needlessly.
      When you finish your FodTrack/SatPC32 installation, would you
put vital commands and suggested tips for SatPC32/FodTrack on the
AMSAT-bb?  This inexpensive, beginner combination includes Doppler
correction.  Everyone should use a form of correction eventually
while a University CUBESAT station this is now an absolute necessity!
      Cliff K7RR
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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