[time-nuts] E1938A PN measurments

[EWKehren at aol.com]

Rick 
I have some 10811's all below 1 E-12 in the 1 to 100 sec. range, a few as  
low as 4 E-13 at 10 seconds. How low have you seen, I have the opportunity 
to  test 40+ units and hope to find a few even better ones. Any guidance will 
be  appreciated.
My best reference is 3 E-13 so any thing as good or better would have to be 
 tested by some one else after initial test.
Bert Kehren
.
 
 
In a message dated 9/30/2012 3:49:33 P.M. Eastern Daylight Time,  
richard at karlquist.com writes:

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
>>> <richard at 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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