Richard B. Gilbert wrote:
Rather than cooling the crystal it's customary to to put the crystal in an "oven". This is not the oven usually used for cooking. What it does is to heat the crystal to a temperature that can be maintained 24x7 and will be a little warmer than the highest temperature that can be expected naturally. A value in the range 120 to 130 degrees F could be used.
The 10 Mhz OCXO which is the frequency reference for a cell phone base station I'm working with is probably keeping the oven at a slightly higher temperature:
The base station itself is specified to tolerate ambient temperatures up to 55C (135F), so the oven has to keep the crystal a bit higher, probably in the 60-70C range?
Anyway, when I googled OCXO the first link I found specified such crystals with shorterm (day) drift rates of 0.1 ppb, and a yearly drift rate of maximum 20 ppb.
That kind of stability would make a pretty good ntpd baseline as well.:-) Terje -- - <Terje.Mathisen at tmsw.no> "almost all programming can be viewed as an exercise in caching" _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
