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

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] GPS with DBSRX, Almost There
Date: Tue, 6 Mar 2007 14:34:01 -0800
User-agent: Mutt/1.5.9i

On Tue, Mar 06, 2007 at 04:57:55PM -0500, Gregory W Heckler wrote:
> Brian:
> From what I see it does not continuously stream data, which is a 
> requirement for my needs. Additionally I am looking at recording GPS L2C 
> and the new Galileo frequencies, so a tuneable front end is a must.

I'm pretty sure that it's capable of continuously streaming data.
It's basically a GPS front end chip connected to an FX2.
It might need a software tweak or two, but if they started with the
USRP code, it'll stream by default.


> Brian Padalino wrote:
> >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

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