[time-nuts] Worst possible error on a rubidium

[Will Matney]

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.
>> Q: What is the most annoying thing in e-mail?
>>
>> _______________________________________________
>> 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.
>
>__________ Information from ESET Smart Security, version of virus
signature database 5851 (20110206) __________
>
>The message was checked by ESET Smart Security.
>
>http://www.eset.com