GM's sinusoidal offset from the reference's PPS (ISPCS2022 tests)
We performed test using SwabianInstruments Time Tagger X (2ps RMS precision). In the test, we measure PPS offset between WR Switch Grandmaster and other devices synchronized to it. During the test, we observed strange PPS offset increase every N PPSes/seconds:
- The amplitude of the increase creates sinusoidal signal with period of ~1800 samples/seconds (~30 min)
- The PPS offset increase happens every 14 samples/seconds (i.e. 13 samples between the occurrence)
- The issue occurred only when GM was locked to GPSDO, it was not present when GM was freerining
Test setup/results and some analysis are presented here: GM-possble-bug-ISPCS2022-test.pdf
All data from the tests is available here: https://cernbox.cern.ch/s/KVULDoDIkWoabHX
The regularity of the phenomena might indicate that the problem is on the measurement device... to be investigated.