[time-nuts] Driving clocks from 1pps

Murray Greenman Murray.Greenman at rakon.com
Thu Sep 4 17:30:16 EDT 2008


In the light of the latest posts on driving clocks from 1pps, it sounds
as though I'd better rethink what I was planning!

I am in the middle of the design of a micro which uses a 10MHz crystal
to provide a digital clock, but the time is kept in line via GPS using a
1pps NCO, which is steered digitally, rather than altering the 10MHz
oscillator in GPSDO fashion.

The plan was to provide two outputs (biphase) at 1pps to drive slave
clocks, but in the light of the notes from Brooke and Chuck, I would be
better off just providing a single output, and use a series cacacitor.

Chuck, I would expect that the 1pps would need to be about 50% duty
cycle, or at least have a pulse width of 100ms or so. I can imagine a
clock driven from 1pps with a low duty cycle would sound quite
different.

73,
Murray ZL1BPU




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