[time-nuts] GPS discipline oscillator vs phase lock
arnold.tibus at gmx.de
Sat Jun 17 18:40:35 EDT 2017
sorry about, but
who is 'lifespeed', a robot or a real person with a natural name?
73, Arnold, DK2WT
Am 17.06.2017 um 23:07 schrieb Lifespeed via time-nuts:
> Yes, one has to lock them at a high reference frequency so as to avoid multiplied-up phase noise. I can manage the tracking loop design. Some applications aren't line-of-sight, so the radio link doesn't solve every situation. Fiber optic backup plan, but everybody hates cords.
> This is my application as well, phase measurement of the signals separated by some distance. Not a billion km, but even a few km requires similar considerations.
> -----Original Message-----
> From: jimlux [mailto:jimlux at earthlink.net]
> Well, at JPL we regularly lock two crystal oscillators together that are over a billion km apart with added Allan deviation of less than 1E-15 at
> 1000 seconds with a radio link at 7.15 GHz. It's how we measure the distance and velocity to spacecraft (a few cm in range and mm/s in
> velocity) and from that figure out the gravitational fields (among other
> So it is *doable*
> The performance depends ultimately on the noise within your tracking loop bandwidth.
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