[time-nuts] Is this a cesium frequency standard?

Said Jackson saidjack at aol.com
Fri Aug 24 01:51:56 UTC 2012


The PRS10 I have here is free-running, and the ADEV looks similar to the plots TVB made. I think it's the time constant of the Rb steering algorithm, not much one can do about that. Maybe lock a good DOCXO to it with say 200s time constant to filter out the hump..


Sent from my iPad

On Aug 23, 2012, at 15:35, "Poul-Henning Kamp" <phk at phk.freebsd.dk> wrote:

> In message <33222. at mymail.acsalaska.net>, "R
> ichard H McCorkle" writes:
>> See the chart TVB produced to see the PRS10 hump in published data.
>> http://www.leapsecond.com/museum/prs10/
> I have measured similar data when the PRS10 is fed a 1PPS from a GPS
> without sawtooth correction.
> The PRS10 has a 1/256 exponential average filter which can get rid of
> most of that noise, and I suspect Tom didn't enable it for that
> measurement.
> But even with that filter, the "hanging bridges" leak through at all
> relevant timeconstants of the PRS10's internal PLL.
> I tried converting the "negative saw-tooth" and injecting it into
> the PRS10 via the serial port, but the results were at best very
> mixed.  In the end I used the PRS10 to timestamp the 1PPS, pulled
> the measurement out via the serial port, and implemented my own
> neg-saw corrected PLL in software, which injected the correction
> back into the PRS10 via the serial port.
> When you do that, you get much better results, at 2Hz and elsewhere.
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
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