[time-nuts] TBolt OCXO replacement

Magnus Danielson magnus at rubidium.dyndns.org
Wed Feb 17 00:08:09 UTC 2010


Henry Hallam wrote:
> Timing newbie here, so please educate me - why does aging matter?
> Isn't the whole purpose of a GPSDO to completely eliminate long-term
> drift?

First degree effect yes, but depending on how you do it, more or less of 
the drift remains uncompensated. If you just try to do frequency 
compensation, drift is uncompensated and a second-degree PI-regulator 
will have a phase shift in its chase of frequency and also then a 
frequency error (it compensates the frequency it had a while ago).

Linear drift compensation (such as PII²-regulator) would work better, if 
only the oscillator had true linear drift... which they don't.

Various elaborate algorithms exists to handle both tempco and drift 
(both important in hold-over operation), the Thunderbolt is not doing 
too advanced tricks. A low-drifter would certainly help, but to be 
meaningful tempco also needs to be considered.

Cheers,
Magnus



More information about the time-nuts mailing list