[time-nuts] Thunderbolt? (re simple gpsdo.)
Hal Murray
hmurray at megapathdsl.net
Fri Dec 30 18:16:51 UTC 2011
> "What is the simplest design for a GPSDO that uses only the PPS signal from
> a modern GPS?"
Some sort of oscillator with a voltage control.
CPU with a timer/counter that can capture the PPS.
DAC.
Software.
Drive the CPU from the osc so you can count cycles between PPS pulses. Use
the DAC to adjust the frequency. Build a low pass filter in software.
The DAC may be the tricky part. You would like lots of bits, but it also has
to be stable.
With a given DAC, you can get finer control by trading off range.
--
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