[time-nuts] FE-5680A adjustments

Mark Sims holrum at hotmail.com
Tue Jun 10 17:18:37 EDT 2008

I just posted my rather long dissertation on the FE-5650A and FE-5680A synthesizer board.  A critical observation is that the F=reference frequency value returned by the "S" command is NOT the value that the unit is actually operating at as shipped from the factory.  It is the value that the physics package operates at with the C-field pot set to its minimum value.  If you attempt to set the output frequency value 10.000000000 MHz on a unit that was factiry tuned to 8388608 Hz for a 1PPS output,  your 10MHz will be around 0.005Hz off (the closest that the DDS divider can produce).

The C-field adjustment pot seems to be the one that is accessible through the hole in the side of the physics package that is close to the internal base plate...  but I have not tweaked it on mine to be sure...

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