[time-nuts] Reference oscillator accuracy

J. Forster jfor at quik.com
Fri Nov 13 17:51:11 UTC 2009


WWVB not WWV.

IMO, WWVB is MUCH fussier than LORAN. It's just utter stupidity that LORAN
is being shut down.

-John

============


> You will need a receiver to compare your references to.  It appears that
> LORAN will be shut off, so that leaves two services available, either
> WWV 60 Khz or GPS.  I do not use WWV any more, I can tell you about GPS.
>
> To compare against GPS you will need a timing receiver, there are
> several available.  A lot of us got Motorola Oncore VPs, UTs, or M12+,
> The Rockwell Jupiter is one and there are several more.  They provide a
> 1 PPS signal that is locked to the on board standards on the GPS
> satellite.  You put this signal in one input of a time interval
> counter.  You use a 1 PPS divider on your local reference and put its
> signal in the other input of the time interval counter.   You can record
> continuous or take daily 24 hour readings and derive your drift rates.
>
> GPS corrections are published at NIST;
> http://tf.nist.gov/service/gpstrace.htm
>
> You can also compare against a GPS disciplined oscillator.  In the long
> term it should be dead on, you will have to have it characterized for
> the short term.  The HP Z3801A was on the surplus market several years
> back, its probably one of the best.  The Trimble Thunderbolts were
> available to the group a while back.
>
> Brian KD4FM
>
> Glenn Little WB4UIV wrote:
>> While I was in the US Navy we had two Cesium standards for the
>> navigation center on SSBN submarines.
>> While in port, we would track LORAN C and compute the drift rate of
>> the two cesium standards.
>> Is there a service, that has drift rates published, that I can compare
>> my standards to, so that I can determine the standard drift rate.
>> I do not remember the drift rates that we determined on the submarine,
>> that was a few years ago, but, I seem to remember that the rate was in
>> the low nanoseconds.
>> If a rubidium standard drifts in one direction (does it?) a drift rate
>> could be calculated and, after a comparison to a known standard, with
>> known drift rate, a very accurate standard could be had for the lab.
>>
>> What would I expect the drift rate, or jitter, to be in a FRK class
>> rubidium oscillator?
>>
>> Is the drift rate constant enough that a drift rate could be applied
>> to a rubidium oscillator to determine it's real frequency at any given
>> time.
>>
>> We calibrated the submarine Cesium standards every three months.
>> We had to know the drift rate of our standard as well as the drift
>> rate of the standard in each of the LORAN stations to be able to do
>> the type of LORAN navigation that we did.
>>
>> I would like to be able to verify that my PTB-100 rubidium oscillator
>> is on frequency.
>>
>> If I compare two rubidium oscillators, what would I expect the
>> relative drift rate to be?
>>
>> Thanks
>> 73
>> Glenn
>> WB4UIV
>>
>>
>>
>>
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