Hi It could be a DDS based coarse tune loop and you just happen to be unlucky on one unit. You can (with bad luck) get a fairly significant spur out of a DDS quite close to carrier. That will give you “ripples” in the ADEV plot.
Bob > On May 23, 2017, at 3:40 AM, Matthias Jelen <matthias.je...@gmx.de> wrote: > > Hello Time-Nuts, > > i´ve been playing with some Rbs recently. > > I compared two LPFRS-01 to a PRS-10. One seems to behave quite well (compared > to the specs given here: > http://www.spectratime.com/uploads/documents/isource/iSource_LPFRS%20Spec.pdf) > - short term stability specs are met), the other one shows quite some phase > ripple (appx. 1 ns RMS with a frequency around 0.007 Hz) which spoils ADEV in > the 60 - 200s range, very similiar to the typical GPSDO bump. Long term > stabilty is OK. > > Unfortunatly I didn´t find any schematics on the web. Has anyone encountered > a similiar problem with this unit? Any idea were this might come from? My > first guess would be a problem in the control loop locking the VCXO to the > Rb, but I have no clue which time constants are used in the PLL. > > Any hints are appreciated. > > Regards, > > Matthias > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
