Hi Your typical CDMA cell tower is spec'd for a 1 us / 24 hours holdover. Weather that's actually going to matter is open to some debate. They try to apply the spec within 3 to 5 days after power up.
Bob On Aug 5, 2012, at 8:07 PM, Chris Albertson <albertson.ch...@gmail.com> wrote: > On Sun, Aug 5, 2012 at 4:27 PM, Bob Camp <li...@rtty.us> wrote: > >> Hi >> >> If the OCXO is off by 200 ppb, it will slip time by 200 ns per second. >> >> It will be off by a *lot* more than 200 ns at the end of a year. Compared >> to the spec's on a cell tower OCXO, 200 ppb per year isn't very good... >> >> > Cell towers typically are spec'd for only 24 hours hold over from a GPS > outage. The idea is that you can get a repair person to a tower within 24 > hours. But I think in real life they can handle a longer than 24 hour > period. > > A YEAR of holdover would be nuts. Who would want to pay for a clock like > that? > > I'm very slowly working on getting my Rb oscillator to be disciplined by > the t-bolt. The $40 Rb unit is roughly a "1E-10 level" oscillator but if > used to drive my NTP server I only really need 1E-3 level accuracy. So > this means I have 1E7 seconds or about 100 days before my clock looses a > millisecond. I think this is exactly what the OP was asking for. > > For this kind of months long outage OCXO is not the best. But if you are > worried about minutes or an hour of holdover OCXO is the best. > > Chris Albertson > Redondo Beach, California > _______________________________________________ > 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.