[time-nuts] Interesting paper: Don't GPSD' your Rb...

[Magnus Danielson]

On 05/07/2012 10:59 PM, Azelio Boriani wrote:
> Yes, interesting, now I realize... but:
>> the larger the deviation becomes and lower frequency it will have... and
> both makes it>harder to suppress by filtering.

> Filtering at what level? Lengthen the sampling time? The average build up?
> That is, now I'm not aware and think that I have to correct as slowly as
> possible because I think that the oscillator has to be disturbed to a
> minimum. Then I see low frequency large deviations, so I think, OK, I have
> to average longer to account for. Is this the filtering you are referring
> to? So that one ends up increasing the slowness of the system getting only
> very slow frequency very large deviations.
> Thanks for the help

If you have a little frequency error the longer you wait to do any 
adjustment the larger phase-deviation that frequency error will result 
in. If you sample to seldom, then you rely on your DAC resolution and 
stability inbetween your samples, the clock will essentially be in 
hold-over. If this is 1 ms, 1 s or 1000 s will make a difference.

That relates to sampling rate, which puts a limit to the loop bandwidth 
you can have.

But my main reaction was to the sample-rate vs. measure and adjust rate 
(i.e. sample rate), and I wanted to point out that there is a merit in 
sampling (much) faster. The modulation waveform is only to illustrate 
the averaging behaviour.

Cheers,
Magnus