[time-nuts] LPFRS phase ripple?
magnus at rubidium.dyndns.org
Tue May 23 05:40:08 EDT 2017
I seem to recall a similar issue and as I recall it, I could see
"wobbles" on the output, which I presume is from the rubidium lamp
RF-generation. It was quite obvious when looking at the output with a
scope. I am quite sure it was a LPFRS-01.
On 05/23/2017 09:40 AM, Matthias Jelen 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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