> Indeed, but you can also handle that by using two oscillators, one for long- > term stability and one for short-term and lock the short-term to the long-term > oscillator with a suitable PLL bandwidth. Comes at some additional cost, but > then you can optimize each end better rather than compromizing on one crystal > oscillator. That ain't a free lunch either. In the end, you should not stare at > the numbers, one must recall the intended application and make that work.
You've hinted at the scenario that I often use here in my lab. I do use two oscillators. For short-term I use a nice quartz OCXO -- free running. And for long-term I use daily averages of 1PPS pulses from a GPS receiver. But they are not disciplined; it's just two completely separate references. Neither helps the other but also neither pollutes the other. This works because, in most cases, for me at least, absolute accuracy is not critical during short-term, low-noise measurements. And similarly, undisciplined averaged sawtooth corrected raw GPS 1 PPS timing provides a slightly better long-term reference than a GPSDO provides. So you get the best of both worlds. Granted a GPSDO sort of gives you both in the same box but do you lose a bit of performance on either end as a result. /tvb http://www.LeapSecond.com _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
