[time-nuts] Holdover recovery

[Magnus Danielson]

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