[time-nuts] GPSDO Educational Tool

[John Ackermann N8UR]

I was doing a set of measurements and realized I'd come up with 
everything you need to understand about GPSDO in one ADEV plot. :-)  I 
thought I'd pass it along.

This shows a sawtooth-corrected GPS PPS and two GPSDOs -- one quite good 
(Z3805), and the other quite awful (u-Blox M8F VCTCXO).

You can see that the quality of the crystal oscillator determines what 
the control loop time constant should be -- the better the oscillator, 
the longer the time constant.  As different as their performance is, 
both these units have their constants pretty well chosen.

John

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