[time-nuts] Is this a cesium frequency standard?
saidjack at aol.com
Thu Aug 23 21:51:56 EDT 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 <3318.104.22.168.110.1345760897.squirrel at mymail.acsalaska.net>, "R
> ichard H McCorkle" writes:
>> See the chart TVB produced to see the PRS10 hump in published data.
> 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
> 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
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