[time-nuts] E1938

Rick Karlquist richard at karlquist.com
Tue Oct 2 17:25:00 EDT 2007

No oscillators are in the non aging category.  However, the E1938
and 10811 are in the RANDOM aging category.  As I previously said,
the direction of the aging is random.  Now you have brought up the
so called disciplined oscillator concept.  This concept admits that
the direction and slope of aging is random between oscillators,
but maintains that an individual oscillator has a known direction
and slope that can be taken out.  This is an extension of the
initial fallacy.  Oscillators can initially age in one direction
for a while and then change directions.  Also, the slope may be
fairly constant, allowing disciplining. or it may gradually decrease.
However, it is also a fallacy to think that the aging will
asymptotically approach zero if you wait long enough.  There are
now extremely old 10811's, and you will find that their aging
is nothing special.

The discipling concept with frequent GPS updates only assumes that
aging characteristics won't change abruptly.  That is the one
assumption that is probably fairly safe.  However, all oscillators
exhibit frequency jumps, that will only be made up after the
time constant of the GPS loop has time to track them out.

When reading papers on discipled oscillators, pay no attention
to anecdotal data.  The only data that counts is on large numbers
of oscillators over large spans of time.


Brooke Clarke wrote:
> Hi Rick:
> I've heard that but it's not clear to me which oscillators are in the non
> aging
> catagory.  For example what about the HP 10811 or the Stanford Research SC
> 10?
> The plot on Brooks Shrea's web page for his GPSDO shows linear aging on
> his
> Austron 1250. See:  http://www.rt66.com/%7Eshera/index_fs.htm
> Have Fun,
> Brooke Clarke
> http://www.PRC68.com
> http://www.precisionclock.com
> http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam
> Rick Karlquist wrote:
>> ); SAEximRunCond expanded to false
>> Errors-To: time-nuts-bounces+brooke=pacific.net at febo.com RETRY
>> This question keeps coming up in relation to various crystal
>> oscillators.  Basically, if you have a really good process,
>> which HP had for the E1938A, there will be no bias in favor
>> of aging in any particular direction.  If there was any
>> bias, the cause of it would be investigated and then eliminated.
>> The main source of aging that remains is believed to be microcracks.
>> These can increase or decrease frequency.
>> Now if you are talking about colorburst crystals, they usually age down
>> because crud from the package deposits on the crystal to
>> a greater extent than dirt on the crystal flying away.
>> Rick N6RK
>> Brooke Clarke wrote:
>>>); SAEximRunCond expanded to false
>>>Errors-To: time-nuts-bounces+richard=karlquist.com at febo.com RETRY
>>>Hi Rick:
>>>If the aging drift is up in frequency then there might be an advantage
>>> in
>>>starting at the low end of the window.  Any idea of how these age?
>>>Have Fun,
>>>Brooke Clarke
>>>http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam
>>>Richard (Rick) Karlquist wrote:
>>>>); SAEximRunCond expanded to false
>>>>Errors-To: time-nuts-bounces+brooke=pacific.net at febo.com RETRY
>>>>The labels may or may not be significant.  If the frequency
>>>>is indeed -2.94 Hz at 2.5V EFC, you could probably get it back
>>>>to 10 MHz by increasing the EFC voltage.  You can also decrease
>>>>the bridge capacitor to bring the frequency up if necessary.
>>>>The factory was supposed to choose the capacitor to get 10 MHz
>>>>in the center of the EFC range.  If this is not correct, the
>>>>oscillator is usually perfectly OK , and they just
>>>>goofed on the capacitor.  The capacitor installation process
>>>>had a lot of problems.  Should be safe to power it up and see
>>>>what the status is.
>>>>Rick N6RK
>>>>Jeroen Bastemeijer wrote:
>>>>>); SAEximRunCond expanded to false
>>>>>Errors-To: time-nuts-bounces+richard=karlquist.com at febo.com RETRY
>>>>>Dear All,
>>>>>After some shipping time, my E1938 arrived today! :-)  :-)  :-)
>>>>>Thank you Rick!
>>>>>First thing was examining the board, oscillator and the HP-test
>>>>>notes/labels. Most of the specs mentioned there are logical and
>>>>> numbers
>>>>>are very reasonable. ;-) However, one spec drew my attention: "Hz off
>>>>>freq. after warm up: -2,94". Does anyone know what it means? Is this
>>>>> the
>>>>>offset after warm-up without EFC applied?
>>>>>The unit hasn't been powered up. Whit the hardware at hand I first
>>>>> want
>>>>>to read some docs to be sure about what I'm doing. For comparison,
>>>>> what
>>>>>other numbers are around for the "Hz off freq. after warm up"-spec?
>>>>>Final result of the HP-test was: PASS. So, I assume this number is OK.
>>>>>What is your opinion? Looking forward to your reactions.
>>>>>73 Jeroen PE1RGE
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