[time-nuts] E1938A PN measurments

[Magnus Danielson]

On 09/30/2012 09:49 PM, Richard (Rick) Karlquist wrote:
> I only measured one 10811. However, John Vig's tutorial
> (available at IEEE UFFC) rather categorically states that
> piezoelectric resonators have flicker noise of frequency.
> What I measured was most closely related to phase noise,
> as opposed to Allan Deviation. Phase noise of 10811's is
> more consistent unit to unit than ADEV and certain more consistent
> than aging. BTW, ADEV at HP was measured against a
> special 10811 that was 500 Hz off frequency. I was never
> able to find out how they arrived at this "golden" unit.
> But it seems clear that it could not have been the
> best ever unit for ADEV, thus the real "golden" units
> that came down the pike were simply rated as ADEV too good
> to measure. I tried to get a project started where we
> would use a frequency synthesizer to do the offset.
> Then we could take the best units and compared them against
> each other. Then, as well accumulated test data, the
> cream would gradually rise to the top and we would have
> some true golden units. The problem was that there ADEV
> at those levels wasn't a "money spec".

With two such offset 10811s you could use DMTD methods or for that 
matter cross-correlation phase noise measures to more directly measure 
the units. That way you would have avoided the "golden unit" issue, 
since the phase noise of those would average out if treated well.

Didn't you consider steps like that?

That's what I do in my lab these days.

Cheers,
Magnus