[time-nuts] E1938A PN measurments

[EWKehren at aol.com]

Doc
The units I mentioned have been done by Corby, but I let units run two  
weeks before I do any test. In the future when I do the 40+ two a week running  
parallel and the best rerun after 4 week soak.
Bert
 
 
In a message dated 9/30/2012 7:55:43 P.M. Eastern Daylight Time,  
docdailey at gmail.com writes:

Bert,

When you do tests like this, how long do you let the  oscillators "settle" 
prior to testing?

Doc

Sent from my  iPad

On Sep 30, 2012, at 4:23 PM, EWKehren at aol.com wrote:

>  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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