[time-nuts] GPS W/10KHz

Magnus Danielson magnus at rubidium.dyndns.org
Sat Feb 8 17:47:35 UTC 2014


Alex,

On 08/02/14 17:34, Alex Pummer wrote:
> Hi Bob,
>   thank you very much, I know about it, the DoD makes it jittery, that
> is not a problem until the average frequency is correct, if you you lock
> a low noise [phase-noise] crystal oscillator to it with a proper loop
> filter you will have a very good reference.

As of 2000, DoD does not add jitter.

Bob is alluding to the fact that the receiver isn't really doing a job 
of producing that 10 kHz, just as with the PPS signal.

As the regular adjustments occurs, the PLL is pulled here and there and 
this scales up and well... becomes quite large when you hit 10 GHz.

Had similar issues with a PLL designed that had a dead-band, which 
caused unacceptable performance onces scaled to about 2,5 GHz. Someone 
tried to use the 4046 current-pump phase-detector. Replacing it with a 
SR phase-detector proved a good solution. Comparator frequency of 8 kHz 
in that case.

Cheers,
Magnus



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