[time-nuts] PRS-10 findings

Tom Van Baak tvb at LeapSecond.com
Wed May 30 10:40:12 EDT 2007


> Hello guys,
> 
> some time ago we talked about curious humps in the ADEV of the SRS PRS-10  Rb 
> at around 20s intervalls.

Can you refresh me on the topic? I didn't see any 
PRS10 humps here:
http://www.leapsecond.com/museum/prs10/

> Could this be the counter self-calibrating?  This is too regular to be  
> co-incident.

I've not heard that these counters do some sort of dynamic
self-calibration. Nor have I seen that sort of periodicity in a
53131 or 53132 counter. You can verify this with one or two
other non-PRS10 and non-Fury sources: set them in the
range of something like 1e-10 apart and collect data for a
couple of minutes. You should see them drift apart at the
rate of 100 ps per second with expected amount of noise
but no other anomalies.

> 
> Has anyone else seen this?
> 
> I don't see this on a scope when comparing two 1PPS's so I do think it's  the 
> counter.

This is the right approach -- to substitute another source, to
substitute another counter, another cable, another DC power
supply, until you locate the culprit.

Just to get a clear idea of your lab set up; how is your counter
configured exactly; int or ext ref? trigger levels? 1X or 10X
attenuation, etc.

If you can see the readings on the 53132 display, do they also
happen when your PC (RS232 or GPIB?) is not electrically
connected to the counter? Desktop or floating laptop?

Is the Fury floating (wall wart) or are you using a grounded
power supply? How is the PRS10 powered? etc.

Also do the 10 MHz RF outputs show this phase jump or is it
only in the 1PPS outputs?

/tvb




More information about the time-nuts mailing list