[time-nuts] wwvb 60 khz tuning fork crystals Some insights

ed breya eb at telight.com
Thu Jun 27 00:13:15 EDT 2013


I presume you used the regular 74HC04 or 74HCU04 inverter, not the 
74HC14 Schmitt trigger input type?? If the '14 is actually used, that 
may explain the problems around setting the feedback biasing resistor 
value - you may be overriding the built-in hysteresis to get it in 
the linear region. Usually that R isn't very critical with regular 
crystals, but maybe tuning fork types need more gain, or, if it's 
actually a '14, the input impedance is probably lower than a regular 
gate, so it's loading the resonator.

Ed



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