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".
Rick
On 9/30/2012 12:16 PM, Ed Palmer wrote:
Would this characteristic be similar across all 10811s or would there be
as much unit to unit variation as there is for aging and Allan Deviation?
Ed
On 9/30/2012 11:03 AM, Richard (Rick) Karlquist wrote:
I recently modified an old 10811 to bring out the crystal
leads on miniature coax (instead of having them connect
to the oscillator circuit). This allowed me to measure
the crystal's inherent flicker noise of frequency.
The measurements indicate that the 10811 phase noise out
to at least 100 Hz is entirely due to the crystal.
An interesting aspect of flicker noise of frequency
is that Allan deviation is independent of tau. Thus,
just one number describes the crystal noise.
Rick
On 9/30/2012 4:44 AM, Bob Camp wrote:
Hi
Close in, it looks like it's pretty much the crystal and the loading
of the bridge oscillator.
Bob
On Sep 29, 2012, at 11:46 PM, Richard (Rick) Karlquist
<rich...@karlquist.com> wrote:
The E1938A uses a crystal that is basically the same as
the 10811 crystal except that it is in a reduced height
package. However the phase noise is not as good as a
10811 due to broadband noise in the automatic frequency
control circuit. By the time I discovered this, it
was too late to try to fix it.
Rick Karlquist N6RK
E1938A designer
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