[ntp:questions] what happens when sys.peer turns stratum 16?

David Mills mills at udel.edu
Wed Jun 2 21:53:46 UTC 2010


The Spectracom WWVB (type 4) driver, among others, uses the qualitity 
indicator provided in the timecode message to set the dispersion when read.


Terje Mathisen wrote:

> David J Taylor wrote:
>> "Miroslav Lichvar" <mlichvar at redhat.com> wrote in message
>> news:hu5osh$kc5$1 at speranza.aioe.org...
>> []
>>> I couldn't find a description either, but it seems to work as expected.
>>> PPS is turned off when the sync is lost and turned on when a fix is
>>> back. It works only when the fix status is changed, i.e. the command
>>> itself doesn't change the PPS status.
>>> -- 
>>> Miroslav Lichvar
>> That's good news, Miroslav, thanks for the update. I'm not sure how best
>> to use that. If lock is lost for a long period then using an alternative
>> source would be better, even if that means only getting (for example)
>> millisecond accuracy. But if the outage is just a few minutes, I wonder
>> whether the free-running PPS output might not be better than sync over
>> the Internet? There may sense in leaving the PPS output running for a
>> few minutes if lock is lost and the PPS is the only precision source -
>> what do you think?
> I have seen ntp source code which used the (measured or implied?) 
> quality of the freerunning oscillator to determine how long such a 
> signal should be considered valid.
> Sorry, I don't remember if this was within a specific driver or in the 
> mainline code. :-(
> Terje

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