In a message dated 4/25/2007 09:50:38 Pacific Daylight Time, [EMAIL PROTECTED] writes:
>So, to >reiterate the question, if I was clear enough, what kind of frequency >excursions should I anticipate to see amongst my three disciplined >oscillators in lets say 24 hours, or in a month. Assume GPS disciplining was >working all of that time (can I even assume that with aging?). BTW, how is >my assumption regarding the oscillators aging? Hello Mike, from my experience, good oscillators will age parts in 1E-08 per day or less. Bad ones can age much faster, some parts in 1E-06 in the first days even. That's a pretty significant variation in EFC voltage required to compensate that. We have seen units that age significantly in the first 2 - 3 days, then slow down, and after 6 months or so almost have no aging. We have seen units where the aging actually accelerates over time. Aging is a very slow changing process after the crystal has run some days (second derivative is small), so GPS locking will usually easily compensate this error. There are oscillators that have popcorn noise (frequency jumps) that can be really annoying, and this effect is similar to rapid aging (from one second to another): almost sudden the phase/frequency of the OCXO changes radically from one second to another. This is usually caused by either dust particles leaving, or landing on the crystal, the crystal "cracking" in it's holders, or radioactive particles hitting the crystal. Also, thermal effects will usually require much larger shifts in EFC voltage than aging, unless you are using a double-oven high quality OCXO. Thermal effects on the required EFC voltage usually swamp aging effects and are harder to deal with because they are more or less random, and not a nice (almost) straight line on the EFC voltage. bye, Said ************************************** See what's free at http://www.aol.com. _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts