Re: [Discuss-gnuradio] GPS with DBSRX, Almost There

[Matt Ettus]

> I've noticed that the DLL of my software receiver settles to +15 Hz, 
> and the true IF is +24 kHz from the predicted IF. This would indicate 
> that the 64 MHz board clock is ~1 kHz from its spec value. This, in 
> itself is not a problem, but I was wondering if this was within 
> tolerances of the onboard XO?

24 kHz off at 1575 MHz would be 15ppm, which is within the spec of 50 ppm.

> The real problem lies in the fact that the carrier tracking loop (a 
> 3rd order PLL) of my software receiver cannot achieve phase lock. The 
> phase jitter looks high, and the LO frequency drifts so much it 
> dominates over the Doppler derived from satellite motion.

Yes, the clock does have a lot of drift relative to the doppler change rate.

> If anyone would like any GPS IF data I would be happy to email it to 
> your personal email address (indicate how many seconds of data you 
> would like). Thanks!
>
>
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