[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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