"Tom Van Baak" <[EMAIL PROTECTED]> wrote: >> 24 hrs would get you to 2.77e-10 / (24 * 3600) = 3.2e-15, which >> is very acceptable. That puts you in the big leagues.
>Hi Mike, > It doesn't quite work this way. If it did, hey, you could wait a > month, and be better than the big leagues! > The missing consideration is the stability of the test setup. The > frequency reference and the phase comparator would have to have > 10^-15 levels of stability before you could claim this sort of > per-day measurement resolution. I can tell you a telecom rubidium > and hp3575A are not even close to this. I know. All I was saying is he could resolve a frequency difference of 3.2e-15 in 24 hours. That is big league stuff. As you point out, that is far better than the oscillators he is using. So his method is valid, and his equipment is capable of making useful and important measurements. Since it is a completely different method, it would give a valuable cross-check against other methods. As far as the measurement stability, the phase measurement is merely measuring the time between two signals. I would expect HP to hold much better than 0.1 degree with no problems. Since it is measuring a relatively small change and not an absolute value, the resolution of 0.1 degree could be considered valid data. So his equipment is capable of resolving a frequency difference that is much smaller than the stability of the oscillators. That is good. But we don't know what would happen during a 24 hour run. So what I was hoping for was a table of phase angle measurements perhaps every 15 minutes for the first several hours to get a feeling for the ups and downs of the phase angle drift, then perhaps every hour for a couple of days. That would be very valuable data. >> Can you see any drift in the GPS time? > You're not likely to see "drift in GPS time" when using a free > running rubidium or another GPSDO as a reference. Do you see why? Sorry, badly worded. I thought he locked the rubidium to gps, and was wondering if he monitored the DC error to the rubidium, and if he saw any diurnal change. If so, that would indicate the rubidium is quite stable by itself. >/tvb Best Regards, Mike Monett _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
