[time-nuts] LPFRS phase ripple?
kb8tq at n1k.org
Thu May 25 06:46:47 EDT 2017
> On May 25, 2017, at 4:12 AM, Matthias Jelen <Matthias.Jelen at gmx.de> wrote:
> Hi Angus,
> thanks for the hint. I read through this fairly long thread - the baseline seems to be: Replace the caps.
> Best regards,
That’s what worked for mine ….. (at least most of them). In my case they arrived dead.
> Am 23.05.2017 um 21:44 schrieb Angus:
>> 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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