[time-nuts] Worst possible error on a rubidium

[Will Matney]

Here's a link to the other pdf that I spoke of on the programming. It goes
into some of the same, but it does have other info.

http://www.dd1us.de/Downloads/precise%20reference%20frequency%20rev%200_4.pd
f

Best,

Will

*********** REPLY SEPARATOR  ***********

On 7/13/2011 at 8:06 PM Will Matney wrote:

>I think it's more in who had them and tried to calibrate them, as some of
>these are actually programmed for the desired frequency. I forget which
pin
>that is, but I think it may show it in one of the pdfs. There's another
pdf
>available out there from a ham who did a lot with these, and it did show
>how to program/calibrate them.
>
>I know a few of the guy's over in Asia like to play with these before they
>sell them, so I think a lot of it's all in whom you get them from.
>
>Best,
>
>Will
>
>*********** REPLY SEPARATOR  ***********
>
>On 7/13/2011 at 4:56 PM WB6BNQ wrote:
>
>>David,
>>
>>The answer to your question is quite complex.  A number of factors
control
>the
>>operation of a passive atomic resonator acting as a filter.  Temperature,
>pressure,
>>buffer gas mixtures, external magnetic forces, coupled light excitation,
>the length
>>of the cavity, the interrogating external RF energy level are but some of
>those
>>factors.
>>
>>The "Atomic" nature of the filter is based upon the extremely narrow
>resonance of
>>electron absorption of energy which occurs at a specific frequency and is
>influenced
>>by the previously mentioned factors.  That specific RF excitation
>frequency is
>>different for each element in the Periodic Table.  For example the
>Hydrogen Maser is
>>around 1.45 GHz; the Rubidium is in the 6 Ghz range and the Cesium is in
>the 9 Ghz
>>range.
>>
>>None of the specification sheets even approach trying to answer such a
>question
>>directly.  However, with certain qualifying assumptions, it could be
>inferred from
>>"certain" specs, if available, as a general idea, BUT, by no means the
>complete
>>answer.
>>
>>For example, looking at Symmetricom's XPRO Rubidium spec sheet, they give
>a 10 year
>>spec of ?+/-1x10e-9.  The assumption is the unit was built correctly, was
>adjusted
>>to be precisely on frequency at its intended installation site and was
>left powered
>>on, in a stable atmosphere, without failures of any kind for the entire
10
>years.
>>If the product truly met those assumptions and specs, then I would say,
>with some
>>confidence, that if you picked up a used one working properly that it
>would be
>>reasonable to assume after powering up and allowing it to come to a
stable
>>temperature (24 hours) and it indicated a locked condition that it would
>be within
>>1x10e-9 of the correct frequency.  Unfortunately, FEI is not so forth
>coming with
>>their product literature, but I suspect their units are similar.
>>
>>Also, be aware that at least one member on this list has reported buying
>two 5680A's
>>from China and they were both significantly off frequency by many hertz.
>Inspection
>>and determination of the problem is a project in motion.  This same
member
>has
>>further stated other reports exist on the WEB of other units exhibiting
>the same
>>problem, although I have not seen those reports.
>>
>>It may prove out that the two 5680A's have a problem.  It is equally
>possible that
>>they are deliberately offset for some specified yet unknown reason.  Time
>will tell.
>>
>>While a Cesium frequency standard is by definition and without question
>accurate,
>>that only applies under a narrow set of circumstances.  It is possible to
>miss
>>adjust such a beast and that is why multiple standards labs constantly
>cross check
>>themselves.
>>
>>Remember, to error is human and machines do what we tell them !
>>
>>Bill....WB6BNQ
>>
>>
>>"Dr. David Kirkby" wrote:
>>
>>> If an old random 10 MHz Rubidium oscillator is working (i.e. powers up,
>and
>>> eventually locks), what is the maximum possible frequency error it
could
>have?
>>>
>>> Could it remained locked with an error of 1 part in 10^7, 10^8, 10^9,
>10^10 etc?
>>>
>>> I assume there are physical limits which would simply stop it
>functioning too
>>> far from the correct frequency, but don't have much clue what they are.
>>>
>>> --
>>> A: Because it messes up the order in which people normally read text.
>>> Q: Why is top-posting such a bad thing?
>>> A: Top-posting.
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>>>
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