[time-nuts] GPSDO using 100Hz

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Nov 24 18:53:48 UTC 2008


WarrenS Email wrote:
>
> Bruce, Thanks for the feedback, Good information to know, 
> but you seemed to missed my point and question.
> in it and must use a processor?
>
> Also I should comment that on  LeapSecond.com 
> http://www.leapsecond.com/pages/gpsdo/
> you stated "where the ADEV for various GPSDO remains below 1E-11 
> over the Tau range of [0.1s, 100,000s]. This Tau has NOTHING to do with 
> the tracking time constant that the GPSDO is set to, which is usually 
> recommended to be set for a TC of several hours for optimal results.
> BTW most of what they have plotted is the results of NOT setting the GPSDO 
> tracking TC slow enough. This is why the Allan Deviation increases in the tracking 
> mode at mid averaging times. The 1 second GPS tracking signal is adding noise, 
> which pretty much makes my point that 1 PPS signal is not so good to use 
> if you want good fast results.
>
> Warren
>   
Analog time constants of several hours are generally considered
impractical due to the lack of suitable low noise components principally
high value resistors and capacitors.
So how do you propose to get around this with an analog control loop?

Bruce



More information about the time-nuts mailing list