[time-nuts] GPS receiver local oscillator (was: 1PPS for the beginner)

Attila Kinali attila at kinali.ch
Tue Aug 14 17:35:56 EDT 2018

On Tue, 14 Aug 2018 13:56:40 -0700
ed breya <eb at telight.com> wrote:

> Perhaps what's needed is a clock that is reasonably stable, like a TCXO, 
> that can be dithered over some range and rate so that the sawtooths 
> never get stretched out far enough to become bridges. If the dithering 
> is in a predictable or controlled form, it seems maybe the 
> filtering/processing could be improved.

Dithering is not as easy as it would seem at first. You still need to
relate the oscillators frequency and phase to the GPS signal. Which means
you have to use the dithered signal as frequency source at least for
the baseband processing. But using a dithered frequency source means
using a frequency source with a (very) bad phase noise. Which reduces
the SNR quite considerably.

			Attila Kinali

It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neal Stephenson

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