[time-nuts] Ublox neo-7M GPS

Hal Murray hmurray at megapathdsl.net
Tue Aug 19 14:05:14 EDT 2014

SAIDJACK at aol.com said:
> its not a GPSDO though, not even a simple one :)
>   It does not discipline an oscillator. It generates the output by
> mathematically calculating how many phases it has to add/drop in a second,
> then   digitally adds/drops/extends/retards the phase of the output clock to
> achieve an average of number of desired clock cycles.

Is there something about the term GPSDO that says I have to do the "D" in the 
analog domain rather than the digital domain?

I agree that current technology doesn't give results that are useful for many 
applications that currently use GPSDOs.  What if the clock ran at a GHz?  10 
GHz?  Sure, it would have spurs, but would it be useful for some applications?

Is a GPSDO still a GPSDO if the D/A driving the VCXO only has a few bits?  
How many bits does it need to be a real GPSDO?

Is a battery powered wall clock listening to WWVB at 2 AM a WWVDO?  It's got 
a pretty good ADEV if you go out far enough.

These are my opinions.  I hate spam.

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