[time-nuts] IC for Clock Input?

Brooke Clarke brooke at pacific.net
Mon Sep 6 19:48:24 EDT 2004


I'm trying again to make a clock that will use the output from a precision frequency standard (1, 5 or 10 MHz) as it's heartbeat.

At first I was going to use the 74HCT4046, like was done by Brooks Shera, but I've discovered that the through hole version of this part is out of production.  Brooks' has them in stock to support his board, but I would like to find a new part.  

In my case all the input IC needs to do is convert the input RF sine wave into a clean TTL drive for the microprocessor.

Can I just use a Schmitt gate like the 74HCT14N?  To center the A.C. coupled input a 68 Ohm resistor to ground and a 200 Ohm resistor to +5 Volts will bias the gate to the center of it's hysteresis and any excursion greater than about 1 Volts (about 20 mw) will cause it to switch.


Brooke Clarke, N6GCE


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