[time-nuts] time-nuts Digest, Vol 51, Issue 73

Ronald Held ronaldheld at gmail.com
Thu Oct 23 19:44:02 UTC 2008 

This may be too simplistic, but are the jumps due to aging effects?

On Thu, Oct 23, 2008 at 8:00 AM,  <time-nuts-request at febo.com> wrote:
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> Today's Topics:
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>   1. Re: Question on crystal jumps (Steve Rooke)
>   2. Re: Question on crystal jumps (WB6BNQ)
>   3. Re: Question on crystal jumps (Neville Michie)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 23 Oct 2008 23:35:37 +1300
> From: "Steve Rooke" <sar10538 at gmail.com>
> Subject: Re: [time-nuts] Question on crystal jumps
> To: "Discussion of precise time and frequency measurement"
>        <time-nuts at febo.com>
> Message-ID:
>        <1231b6a80810230335r74a6bf27r5e9db838425d0364 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> 2008/10/23 Ron Smith <ronald.p.smith at btinternet.com>:
>> The text says the curve of frequency against plate thickness does not give a
>> straight line, but has discontinuities in it. These discontinuities they
>> call "stepping points" and are a result of edge vibrations coinciding with
>> sub-multiple frequencies of the wanted thickness vibration mode. The degree
>> of coupling between the wanted and unwanted modes varies with crystal
>> dimension. If there is zero coupling, the stepping points should not affect
>> the main oscillation. But perhaps even the smallest change in dimension can
>> cause it to cross one of these discontinuities and jump to and fro? I
>> suspect that crystal sensitivity to stepping or jumping may be correlated
>> with its temperature coefficient, although there are other factors
>> (including gravitational) that influence frequency of oscillation at very
>> small levels.
>
> I have a counter that seems to exhibit a jump in it's timebase. From a
> cold state a fixed frequency connected to the input shows a gradual
> change as the unit heats up over an hour or two. Once it reaches a
> stable state it will stay in that state for a couple of days and then
> it will jump to a new stable state, and stay in that state however
> long the unit is switched on. This is repeatable each time I switch
> on. I have not observed the jump and there is no data output on the
> counter to be able to record the times that this happens. All I know
> is that there is a definite little jump after a long period of
> stability.
>
> 73 - Steve
> --
> Steve Rooke - ZL3TUV & G8KVD
> Omnium finis imminet
>
>
>
> ------------------------------
>
> Message: 2
> Date: Thu, 23 Oct 2008 03:42:42 -0700
> From: WB6BNQ <wb6bnq at cox.net>
> Subject: Re: [time-nuts] Question on crystal jumps
> To: Discussion of precise time and frequency measurement
>        <time-nuts at febo.com>
> Message-ID: <49005522.FAE46EB7 at cox.net>
> Content-Type: text/plain; charset=us-ascii
>
> Hi Bob Q,
>
> Yes Rubidium (Rb) and Cesium (Cs) standards use OCXO's.
>
> I suppose the way to look at it is the Rb or Cs chamber acts as an
> invariant
> atomic filter with extremely narrow bandpass (i.e., with an extremely
> high Q).
> The resonant frequencies of these atomic filters are up in the microwave
> regions
> and thus do not lend themselves easily to direct comparison.  So, a high
> quality
> standard frequency oscillator is locked in a loop controlled by the
> atomic
> filter.  The OCXO's output is the reference signal out of the atomic
> standard.
>
> I hope this rather simplistic overview answers your question ?
>
> Bill....WB6BNQ
>
> Bob Q wrote:
>
>> Do rubidium standards use an OCXO?
>> Bob Q.
>>
>> ----- Original Message -----
>> From: "Rick Karlquist" <richard at karlquist.com>
>> To: "Discussion of precise time and frequency measurement"
>> <time-nuts at febo.com>
>> Sent: Wednesday, October 22, 2008 2:23 PM
>> Subject: Re: [time-nuts] Question on crystal jumps
>>
>> > I'm not quite sure what the question is here, but when
>> > we made 10811 oscillators at HP, "jumps happened".  Some
>> > crystals were better than others, but no crystal was immune
>> > from jumps.  With good quality crystals, you might be able
>> > to put an upper bound on the magnitude of jumps, like 10-9,
>> > but not on the time between jumps.  I also noticed that there
>> > didn't seem to be any correlation between jump activity
>> > and stability between jumps.  You could have an oscillator
>> > with really low aging, say a few parts in 1E11 per day that
>> > looked really good for quite a while, but then the frequency
>> > jumps.  After you've controlled everything you can about the
>> > crystal process, the electronics, the oven and the environment,
>> > you are still left with jumps.  If you want no jumps, go to
>> > an atomic standard like rubidium.  There are mechanisms that
>> > can cause jumps in rubidium standards as well, but good
>> > rubidium standards don't jump.
>> >
>> > Rick Karlquist N6RK
>> >
>> >
>> > iovane\@inwind\.it wrote:
>> >> I would be very pleased to know when (date and time) anybody
>> >> out there happened to record jumps in frequency of crystals.
>> >> I have stable (e-07) tuning forks which happen to jump too,
>> >> and I don't understand why, even having under control
>> >> temperature and air pressure. Sometimes they return to their
>> >> prior frequency with another jump, and this could happen even
>> >> days later, sometimes they jump and then recover smoothly the
>> >> prior frequency in a short time (such as one hour).
>> >> I have no idea whether any correlations would exist between
>> >> crystals and tuning forks jumps, regarding the causes that
>> >> could trigger metastability, and hence I would have a look at
>> >> crystal data in order to improve the base for future
>> >> speculation.
>> >>
>> >> Thanks in advance.
>> >> Antonio I8IOV
>> >>
>> >>
>> >>
>> >> _______________________________________________
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>> >>
>> >>
>> >
>> >
>> >
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>
>
> ------------------------------
>
> Message: 3
> Date: Thu, 23 Oct 2008 22:00:56 +1100
> From: Neville Michie <namichie at gmail.com>
> Subject: Re: [time-nuts] Question on crystal jumps
> To: Discussion of precise time and frequency measurement
>        <time-nuts at febo.com>
> Message-ID: <5308066F-31D8-4F19-80D9-66BA4E628364 at gmail.com>
> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
>
> Hi,
> The EFRATOM LPRO does not use a OCXO, just a straight quartz crystal
> oscillator.
> The control voltage swings around a volt as the base plate warms up.
> The time constant of the PLL that the XO is in must be quite short, a
> small fraction of a second
> so that the effect of drifting temperature has little effect on the
> output.
> I guess that all the crystal does is to filter what must be a quite
> noisy signal
> from the atomic resonance. When I inspected the circuit board I could
> not even find the crystal,
> it is not in a grand crystal can.
> cheers, Neville Michie
>
>
> On 23/10/2008, at 9:42 PM, WB6BNQ wrote:
>
>> Hi Bob Q,
>>
>> Yes Rubidium (Rb) and Cesium (Cs) standards use OCXO's.
>>
>> I suppose the way to look at it is the Rb or Cs chamber acts as an
>> invariant
>> atomic filter with extremely narrow bandpass (i.e., with an extremely
>> high Q).
>> The resonant frequencies of these atomic filters are up in the
>> microwave
>> regions
>> and thus do not lend themselves easily to direct comparison.  So, a
>> high
>> quality
>> standard frequency oscillator is locked in a loop controlled by the
>> atomic
>> filter.  The OCXO's output is the reference signal out of the atomic
>> standard.
>>
>> I hope this rather simplistic overview answers your question ?
>>
>> Bill....WB6BNQ
>>
>> Bob Q wrote:
>>
>>> Do rubidium standards use an OCXO?
>>> Bob Q.
>>>
>>> ----- Original Message -----
>>> From: "Rick Karlquist" <richard at karlquist.com>
>>> To: "Discussion of precise time and frequency measurement"
>>> <time-nuts at febo.com>
>>> Sent: Wednesday, October 22, 2008 2:23 PM
>>> Subject: Re: [time-nuts] Question on crystal jumps
>>>
>>>> I'm not quite sure what the question is here, but when
>>>> we made 10811 oscillators at HP, "jumps happened".  Some
>>>> crystals were better than others, but no crystal was immune
>>>> from jumps.  With good quality crystals, you might be able
>>>> to put an upper bound on the magnitude of jumps, like 10-9,
>>>> but not on the time between jumps.  I also noticed that there
>>>> didn't seem to be any correlation between jump activity
>>>> and stability between jumps.  You could have an oscillator
>>>> with really low aging, say a few parts in 1E11 per day that
>>>> looked really good for quite a while, but then the frequency
>>>> jumps.  After you've controlled everything you can about the
>>>> crystal process, the electronics, the oven and the environment,
>>>> you are still left with jumps.  If you want no jumps, go to
>>>> an atomic standard like rubidium.  There are mechanisms that
>>>> can cause jumps in rubidium standards as well, but good
>>>> rubidium standards don't jump.
>>>>
>>>> Rick Karlquist N6RK
>>>>
>>>>
>>>> iovane\@inwind\.it wrote:
>>>>> I would be very pleased to know when (date and time) anybody
>>>>> out there happened to record jumps in frequency of crystals.
>>>>> I have stable (e-07) tuning forks which happen to jump too,
>>>>> and I don't understand why, even having under control
>>>>> temperature and air pressure. Sometimes they return to their
>>>>> prior frequency with another jump, and this could happen even
>>>>> days later, sometimes they jump and then recover smoothly the
>>>>> prior frequency in a short time (such as one hour).
>>>>> I have no idea whether any correlations would exist between
>>>>> crystals and tuning forks jumps, regarding the causes that
>>>>> could trigger metastability, and hence I would have a look at
>>>>> crystal data in order to improve the base for future
>>>>> speculation.
>>>>>
>>>>> Thanks in advance.
>>>>> Antonio I8IOV
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts at febo.com
>>>>> To unsubscribe, go to
>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>> and follow the instructions there.
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at febo.com
>>>> To unsubscribe, go to
>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>> and follow the instructions there.
>>>
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