> -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Ed Palmer > Sent: Thursday, August 27, 2009 12:06 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Couple of questions for Racal 1992 owners > > Thanks for the info Antonio. Racal didn't spec the warmup > characteristics of the counter as a whole and it seemed a little odd > that the warmup drift for the counter was as large as 10 days of > oscillator drift. > > Ed
Intuitively, this wouldn't surprise me. You set the OCXO up so that the temperature is somewhat higher than the highest expected ambient (so, say, it's at 60C) and pick a crystal that has a flat freq/temp characteristic near there. So, when you turn on, your crystal is at, say, 25C, where the slope of the freq/temp curve is pretty steep. I'll bet someone has some curves out there that could give a quick order of magnitude estimate... I have a poor quality chart here that shows an AT cut with about 40 ppm change for a 50 degree C change, and an SC changes about 5 ppm over the same span. Since a decent oscillator has aging of small ppm/year, that's orders of magnitude bigger for the temperature effect. Is this a SC or an AT cut? _______________________________________________ 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.
