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

Piotr Krysik perper at o2.pl
Fri Oct 6 15:33:24 EDT 2017


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

What is on this image is not normal - i.e. much better phase offsets I
can get on two synced RTL-SDR dongles, working under patched driver.

Questions:
1. Have anyone synchronized USRPs B210 up to having constant phase
offset between the devices?
2. If yes - how?

Best Regards,
Piotr Krysik
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