[time-nuts] Good references on holdover?

[Magnus Danielson]

Javier,

If you are aim to do hold-over as you switch between two sources, you 
are looking at reasonably short times, then just keep a fixed voltage to 
the oscillator suffice.

Even if you need a little longer times, say 10-20 s, it suffice.

Temperature changes and oscillator drift may be the main problems for 
longer times.

Cheers,
Magnus

On 02/06/2015 10:21 AM, Javier Serrano wrote:
> Dear all,
>
> We would like to start working on holdover performance for White
> Rabbit [1]. This is a new domain for us. Our main use case is a WR
> switch losing its reference because someone disconnects a fiber. We
> can have redundancy, but it will take some time for a switch to change
> over to another reference. During this time, the oscillator in that
> switch will be free-running. We want to minimize the phase drift
> during that interval, which we think should be a couple of seconds
> maximum. We have never worked on holdover, and I am wondering if we
> can do something smarter than the obvious feeding of some constant
> voltage to the VCXO, based on averaging during the locked state. Does
> anybody know of any good references on holdover?
>
> Thanks!
>
> Javier
>
> [1] http://www.ohwr.org/projects/white-rabbit/wiki
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