[time-nuts] 1PPS for the beginner

ed breya eb at telight.com
Tue Aug 14 16:56:40 EDT 2018


I have often wondered about sawtooth correction and other means to deal 
with it besides reading the offset data (I know about the implementation 
with a digital programmable delay line - pretty slick). Then I wondered 
about what would happen if the GPS receiver's internal clock, instead of 
being from a drifty TCXO, was synchronized and "perfect," synthesized 
from the output 10 MHz. It seems to me that wouldn't work though, 
because eventually the accumulated errors would just flip the offset up 
and down around the true mean, at some very slow rate, rather than more 
rapid, but unpredictable sawtooths and hanging bridges that can more 
readily be filtered out.

Perhaps what's needed is a clock that is reasonably stable, like a TCXO, 
that can be dithered over some range and rate so that the sawtooths 
never get stretched out far enough to become bridges. If the dithering 
is in a predictable or controlled form, it seems maybe the 
filtering/processing could be improved.

Does this make any sense?

Ed




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