Adjusting Encoders to Minimize PN3DB Errors
Updated December 5th, 2001
You will need:
#2 Philips screwdriver
Tiny flat-blade screwdriver
True RMS AC Voltmeter 0 to 2.5000V
Procedure:
Disconnect power and fiber from encoder
Remove cover from encoder

You will be making the adjustments on the FINE AND FIBER XMIT card:
Handy picture of where adjustments will take place

Move jumpers JP1 and JP2 to CAL
Reconnect the power cable

Adjust NULL pot (RI-4) until NULL LED comes on:
Null Adjustment

Connect a true RMS AC voltmeter to SIN (TP3) and COM (TP5)
While moving antenna or rotating encoder shaft very slowly, find the maximum voltage

Adjust the SIN pot (R6) until the RMS AC voltage is 2.0000V:
SIN Adjustment

Move the antenna or encoder shaft through several peaks to make sure that the maximum RMS AC voltage is 2.0000V
Now connect the voltmeter to COS (TP4) and COM (TP5)

While moving the antenna, adjust the COS pot (R11) until the voltage peaks at 2.0000V:
COS Adjustment

Disconnect the power cable
Move the jumpers JP1 and JP2 to RUN
Put cover back on encoder and reconnect power and fiber
Enjoy the improved pointing!
updated 12/5/2001 - Bob Broilo
contact info for Bob Broilo