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

Marcus D. Leech mleech at ripnet.com
Fri Oct 6 17:22:12 EDT 2017

On 10/06/2017 03:47 PM, 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
Try disabling automatic DC-offset and I/Q correction.  I've run into 
this before--since the DC offset and I/Q correction logic is somewhat 
stochastic, you would
   expect precise phase-measurements between two devices to wander 
around a bit with respect to one another.

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