[time-nuts] GPS: ADEV or MDEV?

Christopher Hoover ch at murgatroid.com
Sat Apr 21 23:06:59 EDT 2007


Bruce wrote:
> 6) Doesn't rely on the relative phase of an independent oscillator being
> random with respect to the PPS signal or the OCXO signal. This is rarely
> satisfactory unless one makes heroic efforts to isolate the oscillator
> from the PPS and the OCXO. Injection locking of the "independent"
> oscillator is almost inevitable unless there is sufficient isolation.

I am surely exposing my ignorance here, I don't completely understand this.

The independent oscillator is being used to measure the TI of the PPS, is
that correct?

If so, let's presume this oscillator is clocking a free running counter, the
value of which is being captured on the edge of the PPS and sent to a
processor (for sawtooth correction, filtering, etc.). 

How does injection locking occur?

-ch





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