[time-nuts] GPS first LO need to be locked?

Attila Kinali attila at kinali.ch
Fri Mar 31 07:10:49 EDT 2017


On Thu, 30 Mar 2017 19:56:31 -0400
Bob kb8tq <kb8tq at n1k.org> wrote:

> > Doppler is pretty big when the spacecraft is coming or going at the horizon, about 5 kHz (out of 1.5 GHz, so 4-5 ppm).
> > Relatively speaking, GPS satellites are moving slowly (a few km/s)
> > 
> 
> So somewhere in the baseband processor code somebody said “we’ll handle +/- 5 KHz”. If your LO is < (say) 500 Hz it’s still inside the likely doppler handling range. 
> 
> If you want to do carrier phase then maybe you want to get a bit fancier ….

You have a carrier PLL anyways. What we call "carrier phase" is just
using the information from that subsystem to get a better estimate
for the time differences.

			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, Neil Stephenson



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