Re: [Discuss-gnuradio] Using 10 MHz gps disciplined clock for USRP external clock

[Nick Foster]

On Thu, 2010-12-23 at 04:18 -0500, Burak TUYSUZ wrote:
> Hi all,
> 
> I will be interested if anyone tried to use 10 MHz gps disciplined
> clock outputs on USRP as an external clock.
> I believe USRP will not be doing good at 10 MHz clock so what will be
> the best way to use this output from GPS with USRP...
> Thanks in advance

USRP2 has an SMA connector on the front which will take a 10MHz
reference to synchronize the oscillator. USRP1 does not. This is not
readily doable on a USRP1 as it doesn't use a VCO, it uses a fixed 64MHz
oscillator.

That said, I have done this on my USRP1. I modified the USRP to use an
external clock and built a 64MHz reference oscillator using a GPSDO and
a homemade PLL, using an Si570 as the VCXO. It works pretty well,
although when I finally put it on a phase noise analyzer it didn't look
particularly great.

In hindsight, it might be easier to solve the frequency mismatch problem
in software. =)

--n


> 
> -Burak
> 
> 
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