[time-nuts] Caveats on Allan Deviation with ultra stable oscillators

Bob Camp kb8tq at n1k.org
Fri May 30 19:58:16 EDT 2014


Hi

The question was “Rb ensemble” …. AFIK you would have to go back quite a way to find NIST running one….

Bob

On May 30, 2014, at 7:52 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:

> Bob,
> 
> The long tube Cs standard (NIST 7) is parked in the entrance. Too noisy to contribute much value. They have a bunch of 5071As and hydrogen masers. They live in individually temperature stabilized compartments. One typically is selected as the reference and then you measures differences. With these differences they then run the ensemble program on a pair of redundant PCs every 12 min.
> 
> Cheers,
> Magnus
> 
> On 05/30/2014 09:24 PM, Bob Camp wrote:
>> Hi
>> 
>> Rubidium ensemble? That would have been quite a while back. They have been running on long tube Cs standards for quite a while.
>> 
>> Bob
>> 
>> On May 30, 2014, at 2:03 PM, Tim Shoppa <tshoppa at gmail.com> wrote:
>> 
>>> What did NIST do with its Rubidium ensemble before they got the cesium fountain?
>>> 
>>> Did they break one of the rubidiums off the ensemble, maybe in a
>>> different room with different HVAC, and look at the one vs many?
>>> 
>>> Would that be useful for OCXO's, measuring one OCXO against an ensemble?
>>> 
>>> Tim N3QE
>>> 
>>> On 5/30/14, cdelect at juno.com <cdelect at juno.com> wrote:
>>>> Hi,
>>>> 
>>>> I usually don't use drift removal as I want to see the effects of drift!
>>>> 
>>>> The effects of oscillators locking together are very apparent on both the
>>>> phase and AD plots when using a DMTD system. There was no indications of
>>>> such locking!
>>>> 
>>>> My point was that if you are measuring ultrastable Quartz oscillators
>>>> against each other the AD at the higher Tau will not reflect the true
>>>> stability of the oscillators.
>>>> 
>>>> Only a Maser or high performance Rubidium (HP5065A) will reveal the true
>>>> behavior.
>>>> 
>>>> Cheers,
>>>> 
>>>> Corby
>>>> 
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