[time-nuts] Small basket

Azelio Boriani azelio.boriani at screen.it
Thu Oct 13 04:17:45 EDT 2011


Are you referring to Kalman filtering/steering? Yes, it depends on how
accurate is the model of the oscillator (and the dimensions of the
Kalman filter) but it can work for several hours not indefinitely.

On 10/13/11, Chuck Harris <cfharris at erols.com> wrote:
> Because the aging of oscillators is sufficiently random that it defies
> prediction over the long term.  Austron, and others, have made disciplined
> oscillators that calculated the aging rate relative to a stable source,
> and applied that correction to the oscillator's EFC if the stable source
> went away... It works for several hours at most before the stubborn little
> oscillator, and the aging model diverge.
>
> -Chuck Harris
>
> Perry Sandeen wrote:
>> List,
>>
>> Wrote: I wonder how long it will be before the only remaining basket of
>> will
>> suffer a catastrophic fall.
>>
>> The U.S. satellite system, AFAIK, is not guaranteed for high accuracy to
>> civilians
>> and also is vulnerable to foreign interference/destruction.
>>
>> Perhaps while we have it as it is now, it might be prudent to accurately
>> track the
>> EFC voltage over time that one needs to maintain a particular oscillator
>> to it
>> maximum stability.
>>
>> Then make an independent oscillator and divider chain that will cycle a
>> digital
>> potentiometer taps or perhaps a DAC to automatically maintain the rate-of
>> - change
>> needed to keep said oscillator at maximum stability.
>>
>> Doing this now with at least one or two oscillators and then comparing to
>> a GPS
>> derived frequency and least gives one a “belt and suspender” back-up.
>>
>> High quality 10 MHz oscillators are available all day on epay for less
>> than $50.
>> Or one could splurge on  a HP 10811 or Rubidium for less than $100.
>>
>> Just food for thought.
>>
>> Regards,
>>
>> Perrier
>>
>>
>>
>>
>>
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