[time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit

Hal Murray hmurray at megapathdsl.net
Tue Dec 19 19:55:34 EST 2006


> Noise like the oncore sawtooth isn't always a bad thing.

I was going to comment on that area...  Thanks for the reminder.

The problem is that the sawtooth isn't noise in the normal Gaussian sense.  
If you happen to hit a long/wide hanging bridge, the resulting offset may get 
past your PLL filter.

It might be possible to avoid hanging bridges by dithering the sawtooth.  I'm 
thinking of something like a heater under the xtal for the GPS unit that gets 
driven by a medium frequency - slow relative to the normal sawtooth but fast 
relative to the PLL time constant.  This somehow feels not-good, but I can't 
see the obvious screwup.

-- 
These are my opinions, not necessarily my employer's.  I hate spam.






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