Re: [Discuss-gnuradio] multi usrp, 1 odd channel, HW problem?

[Matt Ettus]

Probe R201 on all 4 WBX boards with an oscilloscope while running.  One 
side of the resistor is ground and the other side is the reference 
clock.  They should all be around the same amplitude, and have the exact 
same frequency and phase.

Matt

On 10/14/2010 09:13 AM, Steven Clark wrote:
> Hi all-
>
> I have a multi-usrp setup with 2 USRP 1s and 4 WBX daughtercards. I have
> performed the clock synching described here:
> http://gnuradio.org/redmine/wiki/1/MultiUsrp
>
> I'm doing 4-channel receive, using a power splitter to send the same CW
> signal into all 4 d'cards, and tuning them all identically.
>
> 3 of the 4 channels are nicely phase-locked. The 4th seems a little...off.
>
> ClockMasterUSRP (Serial #5821): Side A: "red" channel
> ClockMasterUSRP (Serial #5821): Side B: "green" channel
> ClockSlaveUSRP (Serial #2087): Side A: "blue" channel
> ClockSlaveUSRP (Serial #2087): Side B: "black" channel <--- problem with
> this guy
>
> Please see these 3 images to see the problem:
> http://picasaweb.google.com/steven.p.clark/MultiUsrpGlitches?feat=directlink
>
> You can see the problem in both the frequency domain, and in the time
> domain.
>
> I tried swapping daughtercards around, and the problem is not tied to
> any one daughtercard, but rather to slave USRP side B.
>
> Any idea what could be causing this? Shouldn't the same clock be going
> to both sides of the USRP? (why does blue look fine, but black does not?)
>
> -Steven
>
>
>
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