On 12/08/2013 11:46 AM, Attila Kinali wrote: > Hi Magnus, > > On Fri, 29 Nov 2013 17:42:25 +0100 > Magnus Danielson <magnus@rubidium.dyndns.org> wrote: > >>>> When I look in the data sheets of oscillator that I find on the internet, >>>> they only have precision estimates like 1ppm or 1ppb, but no detailed allan >>>> variance graphs. >>> Yes. Because in the class of cheap AT cut oscillators, you dont worry about >>> allan variance. The instability due to temperature dependence of your >>> system is much higher than the temperature-free (in)stability. The ADEV >>> becomes "relevant" only after you do at least a temperature compensation >>> or temperature control. >> The specification for temperature variations is a poor excuse too. Some >> vendors have learned that the hard way. > Could you explain a little bit what you mean here? I don't think > i get exactly what you are hinting at. Well. While staying within +/- 10 ppm over the temperature range may be one way of specifying the temperature dependence, it does not give you a good sense how it behaves at some particular temperature. Also, these are long-term dependence, but what happens when there is a quick change in temperature, what happens to frequency... and phase. Then we have drift properties. Let's put it another way. There is a reason cheap oscillators are cheap. Cheers, Magnus