[USRP-users] Frequency offset between two USRPs B210 synchronized with use of Octoclock-G

john Shields john.shields at xtra.co.nz
Fri Oct 6 18:12:43 EDT 2017


On 06/10/17 19:47, Piotr Krysik via USRP-users wrote:
> W dniu 06.10.2017 o 21:33, Piotr Krysik via USRP-users pisze:
>> Hello everyone,
>>
>> I synchronized two USRPs B210 with use of Octoclock-G and the attached
>> gnuradio-companion flowgraph.
>>
>> I've connected signal generator generating sinusoid to both devices (it
>> was on frequency 694.5MHz while USRPs were tuned to 694.3MHz, signal
>> power was about -40dBm). What I would expect is to see constant phase
>> offset between signals received by both USRPs (perhaps changing slightly
>> with temperature etc.). However what I see is constant changes of phase
>> that corresponds to frequency offset between two devices. Moreover this
>> frequency offset changes significantly from one execution of a flowgraph
>> to another (look at the image):
>>
>> relative phase of two B210's
>>
> Missing image of phase offsets in the attachment.
>
> Best Regards,
> Piotr Krysik
>
>
>
>
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Hi Piotr,

             While I have a slightly different h/w configuration 
(2xN200, one GPSDO connected through MIMO cable (i.e. I use slightly 
different time/clock sources; and 2 SBXs) and while I have modified the 
Python code to use  timed_commands per the ettus sync page , I have not 
been able to get a consistent relative phase offset between the devices 
on successive GRC runs. I have been struggling for quite a while - 
hopefully, you will get a resolution quickly and I believe it might also 
fix my problem!


                      Kind Regards,


                                  John

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