[time-nuts] ensemble oscillators for better stability

Said Jackson saidjack at aol.com
Sun Dec 30 19:12:30 UTC 2012


The Tsc5125A and miles Timepod show a phase noise floor 3dB above the noise floor of the two oscillators (if two are used with identical noise floors).

Your oscillators are better than you think, or your equipment is not calibrated.

Btw: that result IS what you want, why would you want that measurement to show better results than what your DUT can provide??

Now the tester may recognize that IT by itself could do better with better reference and DUT, and thus may also show a lower instrument noise floor, but that cannot be reached with a noisy reference no matter how long you average.

It would be nice if that worked, then we all could use $10 TCXOs instead of $1000 Wenzel references.

A cross correlated measurement usually treats the DUT and REF identically, so if one is way more noisy than the other one, the noisier one will be the noise floor shown.


Sent From iPhone

On Dec 30, 2012, at 1:44, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:

> Tom Knox wrote:
>> Dual oscillators in Cross Correlated
>> measurements will also produce a 3dB theoretical reduction in a Phase
>> Noise measurement system.
> Since when?
> Its way better than that.
> I routinely achieve a PN floor below -170dBc/Hz (I don't have an OCXO with a phase noise floor below ~ -175dBc/Hz) using a pair of oscillators each having a PN floor (~ -150dBc/Hz) well above that
> Bruce
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