[time-nuts] GPS phase lock !!

Bruce Griffiths bruce.griffiths at xtra.co.nz
Fri Mar 6 04:58:46 UTC 2009


Dan Sawyer wrote:
> I am new to time-nuts, and have just successfully phase locked a Jupiter 
> GPS 10kc signal to a 10 mhz vcxo. There is jitter in the 10kc Jupiter 
> output, as expected. How can the characteristics of the 10 mhz vxco 
> signal be measured or analysed? A 10 mhz signal from a tcxo shows a 
> clean sync with the locked 10 mhz signal, however there is low frequency 
> 'jitter' between the two signals. The 10 mhz signal gains and looses 
> over about a 40 nsec range on a random 20 to 40 second cycle.
>
> What is the root cause of this low frequency oscillation? Is it the 
> result of the phase lock 'searching'? Or is it inherent in the 10mhz 
> tcxo output?
>
> Thanks in advance - Dan
>
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>   
Dan

In order to make useful comments, more detail about your circuit and PLL
time constants etc are required.


Bruce




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