[time-nuts] Has anybody checked this? GPSDO in kit

Mark Sims holrum at hotmail.com
Sat Oct 22 22:52:22 EDT 2016

Yep,  I recently sorted through a bag of 100 crystals from China ($10, shipped) looking for a "good" one.  They were ALL good...  a complete waste of time.  I was rather amazed at their consistency and performance for a 10 cent part.

Last year I bought an alarm clock / game from China (looks like 7 sticks of dynamite with an ominous circuit board / LED display strapped to it).  It uses a 40 pin (AVR?) processor driven by a 16 MHz processor crystal.  I have not set it in over a year and it is still within a few seconds.  I suspect they measure the frequency and have a calibration tweak stored in EEPROM... but that seems excessive work for a $20 toy.  I highly doubt they go as far as doing temperature compensation.  Maybe they characterized a bucket of XTALs and use a generic compensation factor?


>  Yes, you can build gear to do temperature runs on crystals and sort bags full of them. 
It’s likely that your whole bag of 5,000 came from the same bar and your 
net result will all look a lot alike…..

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