[time-nuts] Holdover recovery

Logan Cummings logan.cummings at gmail.com
Mon Apr 4 22:01:45 UTC 2016


My Italian is not very good, but I think this is the English translation
via ITU:

https://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-BT.2253-2012-PDF-E.pdf

-Logan

On Mon, Apr 4, 2016 at 1:10 PM, <timeok at timeok.it> wrote:

> Here the italian version:
>
> http://www.crit.rai.it/eletel/2012-1/121-2.pdf
>
> Luciano
> www.timeok.it
>
>
> On Mon 04/04/16 21:28 , Magnus Danielson <magnus at rubidium.dyndns.org>
> wrote:
>
> > Hi Hal,
> >
> > On 04/04/2016 05:39 AM, Hal Murray wrote:
> > >
> > > Has anybody studied what happens when a GPSDO comes out of holdover?
> Has
> > > anybody seen any specs? I don't think I have.
> > >
> > > I think you have a choice of quick recovery for time or frequency, but
> > you
> > > can't get both.
> > >
> > > Suppose your setup has been in holdover for a while. The frequency is
> > > slightly off. The time offset of the PPS pulse will be the integral of
> > the
> > > frequency offset.
> > >
> > > What happens when you come out of holdover? If you fix the frequency,
> > the
> > > PPS will stay off.
> > >
> > > Suppose the PPS has drifted by 1 ns. If you correct that in 1 second,
> > the
> > > frequency will need to be off by 1E9 during that second.
> >
> > The RAI laboratory in Torino have made such tests and published
> > measurements and recommendations. For a long time it was only available
> > in italian, but there is now an english version available.
> >
> > Cheers,
> > Magnus
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