Hi I think the idea is to run the TCXO while the OCXO is > 1 ppm off frequency and then switch to the OCXO when it's sure to be OK. Most inexpensive approaches to locking the TCXO will give you a pretty major frequency transient. Depending on what you are doing, that may muck things up as much as a dropout.
Bob On Dec 9, 2012, at 5:25 PM, Magnus Danielson <mag...@rubidium.dyndns.org> wrote: > Hi Joseph, > > On 12/09/2012 10:53 PM, Joseph Gray wrote: >> The finished project will be placed where I won't have regular access >> to it, so I think I have justification for wanting this complication. >> Also, I want to monitor which oscillator is in use, so my application >> will know. > > First reaction would be to lock the TCXO to the OCXO. It's not that hard to > make a PLL which will start acting only when the OCXO is "ready" (oven > detection could be part of it). > > Another approach than direct PLL locking could be to use injection locking, > but designing for it could be challenging. > > Switching a clock is a bit sensitive, but one solution to achieve it is to > lock the OCXO to the TCXO when the OCXO comes around, and only when that PLL > has lock, then switch between them and just let the lock state fade out on > the OCXO control, as you kill the control loop. > > A few ideas. I don't like switching of clocks, so I would avoid that if > possible, even if precaution to make sure they are locked to be > phase-aligned. I would go for the lock-up of the TCXO. Make sure that the > lock-in does not upset any of the measurements, possibly by making the > lock-in a little "weak" so the maximum rate of change isn't too great. > > Cheers, > Magnus > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
