[time-nuts] Phase noise vs warmup or time

[Tom Van Baak]

> If I have several crystals and I want to find the ones with good phase noise, 
> do I have to let them run in their ovens for a week/month, or can I just turn 
> them on and measure the phase noise?

I'll make a distinction between time domain and frequency
domain measurements.

A long warm-up is helpful if you want to measure frequency
stability (e.g., sigma of tau, or ADEV).

But, depending on the equipment you use, a phase noise
measurement (e.g., script L of f) doesn't require the source
to be long-term stable; you get pretty much the same phase
noise results in the first minute as you would a day or week
later.

/tvb