Re: [Discuss-gnuradio] Rotating constellations and varying LOs with USRP B210 + Board Mounted GPSDO

[George Sklivanitis]

Hi Nicolas, 

Thanks for the response. I have already posted my question to the USRP-users list. 

I am using the clock reference only from the GPSDO mounted on each of the B210s. I am not exporting the time reference from one device to the other. 

We have been testing communication links between GPS disciplined B210s and N210s, each on it's own GPSD0 mounted clock, as well as between B210s with their own GPSD0 mounted clock and N210s that receive an external REF and PPS from a GPS-disciplined octoclock. 

We observed the same thing. LED indicators on all devices show that the clock reference locks but constellations keep rotating. Should we address the residual CFO or is there something wrong with the hardware?

Thanks,

George 

On Mon, Sep 11, 2017 at 7:32 AM, Nicolas Cuervo <address@hidden> wrote:

Hello George,

this question would be better posted in the USRP-usrs list. However, the answer to this is "yes". There is a known issue on the B210 when using GPSDOs and it's report of PLL lock. Are you using the clock reference only from the GPSDO mounted on each of the USRPs? or are you also exporting the time reference from one device to the other? 

On Wed, Aug 30, 2017 at 6:14 PM, George Sklivanitis <address@hidden> wrote:

Hi everyone, 

Has anyone noticed unstable LOs or carrier frequency offsets when using USRP B210s with board mounted GPSDOs?

We have recently been doing field tests using GPS-disciplined oscillators for both USRP B210s and USRP N210 and occasionally both transmitter and receiver flowgraphs lose GPS lock, although clock reference leds in the USRP panel are ON.

Thanks,

George

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Sklivanitis Georgios
Postgraduate Student

Telecommunications Division
Technical University of Crete
ECE Dept.
Tel. : 28210 59257