Thanks, John. That was the type of information I was looking for. Joe Gray KA5ZEC
On Mon, Oct 5, 2009 at 11:34 AM, John Ackermann N8UR <j...@febo.com> wrote: > Here's a reason why you might "want" (as opposed to "need"!) another > standard beyond the GPSDO. > > An Rb or Cs is self-contained. The GPSDO relies on an external factor, the > presence of GPS. Holdover mode may be good to keep thing close for a while, > but over the long term the GPSDO without GPS is no better than its crystal > oscillator. > > The Rb is a secondary standard and therefore isn't "correct" by definition, > but it has a low aging rate and gives you something independent of GPS to > use for measurements. Monitor it against GPS for a while to learn its > offset and drift characteristics, and then you can extrapolate its > performance out over a much longer time than you could with an OCXO. > > You may not require that independence, but it gives you additional > measurement capability. For example, comparing the output of two GPSDO may > not be meaningful because their frequencies could be correlated by their > common view of the GPS constellation. Using an Rb reference would eliminate > that common mode error and reveal information about the GPSDO's short and > medium term stability that would otherwise be hidden. > > John > ---- > Joseph Gray wrote: >> >> I know I don't "need" any of this stuff. I was just wondering what I >> could do with a rubidium vs what I already have. >> >> On Mon, Oct 5, 2009 at 10:58 AM, J. Forster <j...@quik.com> wrote: >>> >>> From an engineering point of view: >>> >>> Very few people really "NEED" a Rb or Cs as they are not really doing >>> anything that requires that level of precision in frequency or accuracy >>> in >>> time (me included). These days a BC-221 or WWB is not good enough, but 1 >>> Hz at X-Band is for almost all practical uses. > > _______________________________________________ > 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.