[time-nuts] Simulation of oscillator noise

[Magnus Danielson]

On 12/08/2013 11:46 AM, Attila Kinali wrote:
> Hi Magnus,
>
> On Fri, 29 Nov 2013 17:42:25 +0100
> Magnus Danielson <magnus at 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