I learn from this discussion that the aging rate claimed by manufacturers would refer to the aging of the whole assembly, not the crystal alone. And for practical purposes that is correct. And even in the case of sealed assemblies, components other than the crystal itself may affect the overall measured drift. So my original question on this subject seems to lose any sense, because we will never be able to measure the aging of the crystal alone (if any, at this point) and hence variations in the aging rate either. Anyway some doubts of mine are not yet fully answered by this discussion, and I would appreciate your opinions. Given a good quality sealed OCXO running in constant ambient temperature, what kind of aging curve should one expect, a fluctuating one? (I understand that this might be the case, due to the interaction of known "intrinsic" aging factors having different timescales, as I've just learnt on this list. A "regular" curve would be hard to get). May it happen that fluctuations in frequency due to "external" causes such as tides, geomagnetic storms, or so, and not actually affecting the "aging rate", are interpreted as fluctuations in the aging rate?
I'm running a simple test comparing an OCXO (option 04E on a military Racal 1992 counter) to rubidium (LPRO), the counter being counting the LPRO. The test is running since about two weeks, and I started recording three days after power up. In the first days the OCXO showed a decreasing drift starting with some 3x10e-10 per day until it reached a stability within +/- 1x10e-10 in the last 5 days (that is, since 5 days back, the counters reads always the same value +/- the occasional uncertainty of the rightmost (11th) digit (10 seconds gate time). The OCXO specs are <= 5x10e-10 per day. I didn't notice whether it is sealed, and won't check right now. I don't expect that the counter will always stay there, and I don't know what to think when the drift (aging rate?) will change. Thanks, Antonio I8IOV _______________________________________________ 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.
