[time-nuts] Thought experiment on a low cost timing board

SAIDJACK at aol.com SAIDJACK at aol.com
Sat Feb 25 19:29:00 EST 2006

Hello Poul-Henning,
how does SRS handle OCXO aging?
If the fine DAC only has 1:1000 of their 12-bit coarse DAC, and  the EFC 
range is +-20Hz, then the LSB DAC can only control about 2E-09 or  so over its 
full range if my math is correct.
Good OCXO's (e.g. MTI) crystals usually age between 3E-09 to 5E-010  per day 
as per their spec.
That would mean the coarse DAC would switch worst case about once a  day.
You mentioned there are some discontinuities when the coarse DAC switches  
(since the coarse and fine dacs have to switch simultaneously I guess to prevent 
 glitches). How bad are these discontinuities/glitches?
Would such a system not glitch every time the coarse DAC switches to  
compensate for crystal aging?

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