Tom Van Baak said the following on 12/29/2009 04:24 PM:
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.
As a practical matter, you need to allow an OCXO time to stabilize or else the warm-up frequency drift may cause difficulties in the phase noise measurement. You need to keep the DUT and reference in the proper phase relationship, and if the drift is too fast the PLL may not be able to keep up. From what I've seen using the TSC test set, you'll get glitches in the flicker-noise region (say, around 1 Hz offset); the floor isn't much affected.
I fully agree with Tom on the main point -- I'm not talking days or weeks, but an hour or so is probably a good idea.
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