And this is a short video of the phase detector in action using a TCXO and 10 seconds phase averaging.
Yellow line goes high after PPS up edge and goes down at up edge of the 2.5MHz clock. Maximum high time is 400ns
The blue line shows the charging of the capacitor supplying Vphase to the Arduino
If there is perfect lock and no fractional adjustments of the PPS the phase (width of the yellow pulse) does not change with each PPS.?
Sometimes you see the 22ns jump left or right when the PPS is adjusted with one cycle of the 48MHz clock
If there is no perfect lock you see a slow drift of the phase.
After each recalculation of the target frequency every 10 seconds the phase jumps to a totally new value because the VCO PLL is restarted.
With an XTal in the SI5351 the phase is considerably less stable but still sufficient for achieving a lock
--
HBTE Files section:?
/g/HBTE/filesErik, PD0EK
