[time-nuts] FA2 internal OCXO orientation sensitivity

[Mark Sims]

The first time that I tried to set the FA2 internal oscillator frequency I tilted the case so that the screen was facing down and the adjustment screw was facing up.  I got it on frequency, but when I placed the unit with the bottom of the case facing down the oscillator was 0.032 Hz off.  So I did some more testing with the case in various orientations.  It looks like the frequency is fairly insensitive to orientation except for tilt in the front-back axis where it is around +/-1 milliHertz per 3 degrees of tilt (which seems rather high to me).  If you are using the FA2 in a mobile application pay close attention to the front/back tilt of the case.

   F:0010000000.001619430  bottom down
   F:0010000000.001687723
   F:0010000000.001946380
   F:0010000000.001902348
   F:0010000000.001692710
   F:0010000000.001663366
   F:0010000000.001712156
   F:0010000000.001760899
   F:0010000000.001590295
   F:0010000000.001648737

   F:0010000000.001922004 bottum up
   F:0010000000.002214679
   F:0010000000.002209653
   F:0010000000.002063463
   F:0010000000.001912133
   F:0010000000.002556087
   F:0010000000.002775519
   F:0010000000.002053697
   F:0010000000.002014587
   F:0010000000.001570725

   F:0010000000.033927950 screen down
   F:0010000000.033435257
   F:0010000000.032562128
   F:0010000000.032625399
   F:0010000000.032098574
   F:0010000000.032225335
   F:0010000000.032391257
   F:0010000000.032571790
   F:0010000000.032922928

   F:0009999999.971298357  screen up
   F:0009999999.967820455
   F:0009999999.967859533
   F:0009999999.967986393
   F:0009999999.967800925
   F:0009999999.967947314
   F:0009999999.968327835
   F:0009999999.968252960
   F:0009999999.968030373

   F:0009999999.998658455  left edge down
   F:0009999999.998985308
   F:0010000000.000419484
   F:0010000000.002063510
   F:0010000000.003292634
   F:0010000000.003956045

   F:0010000000.002448722  left edge up
   F:0010000000.002029197
   F:0010000000.001917045
   F:0010000000.001985357
   F:0010000000.002012571
   F:0010000000.001980588