[time-nuts] New Subscriber, DIY GPSDO project (yes, another one)

[Bob kb8tq]

Hi

One of the biggest issues in all this is that while a group of OCXO’s
may have some similar characteristics, they most certainly will not all
have the *same* characteristics. This one is at 5x10^-13 at 1 second
and the next one out of the box is at 5x10^-12 at 1 second. 

On top of that, your GPSDO may not have the luxury of continuous 
operation. Most commercial designs are targeted at “this level of 
holdover” after “that number of hours on power”.  You might get
72 hours on power, you also might be required to do it all after 
24 hours.

Finally, the operating environment may be nicely controlled in one 
case and really horrible in the next case. This one is in a nice cave
and the next one is in an unheated garage. 

Very much not a “one size fits all” sort of thing.

Bob

> On Mar 10, 2020, at 7:53 AM, Attila Kinali <attila at kinali.ch> wrote:
> 
> On Tue, 10 Mar 2020 03:38:11 +0100
> Magnus Danielson <magnus at rubidium.se> wrote:
> 
>> Now, to raise the complexity, the state-model of noise does not allow
>> for flicker noise variants. There just isn't a a good way to express
>> that. There is a few articles that give rough estimates, but no
>> half-integrators to be seen and therefore the noise models which is so
>> important in Kalman does not work very well.
> 
> There is a thing called "fractional control" which deals with fractional
> order (integrator/differentiator) control loops. But, what I have seen
> so far was only fractional order in the underlying system model, not in
> the noise. But I have only scratched at the surface of this topic, so
> there is a lot I have not seen yet.
> 
> If someone here knows more about fractional control, I would really
> enjoy a chat about the topic.
> 
> 				Attila Kinali
> 
> -- 
> In science if you know what you are doing you should not be doing it.
> In engineering if you do not know what you are doing you should not be doing it.
>        -- Richard W. Hamming, The Art of Doing Science and Engineering
> 
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