[time-nuts] E1938A PN measurments

Bill Dailey docdailey at gmail.com
Sun Sep 30 23:55:26 UTC 2012


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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