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

[Brian Padalino]

On 3/6/07, Gregory W Heckler <address@hidden> wrote:
> 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?

I believe the XO on the USRP has a 50ppm spec, so 1kHz is well within that.

> 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.
>
> 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!

On a side note, have you seen that SiGe device available from Spark
Fun Electronics?  I posted earlier today about it.  It might be of
interest?

   http://www.sparkfun.com/commerce/product_info.php?products_id=8238#

Brian