[time-nuts] LPFRS phase ripple?

Angus not.again at btinternet.com
Tue May 23 15:44:12 EDT 2017


If you've not already looked, it would be worth checking on the
EEVblog since there were some discussions there on faults in these
units - particularly the capacitor and lamp voltage issues.
One of the temperature controllers could be a little unstable too.


On Tue, 23 May 2017 09:40:26 +0200, you 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.
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