Hello - I am trying to frequency sync two USRP B210s. I have a GPSDO on both USRPs so the 10 MHz ref is unavailable (as noted in the site manual) and I am unable to use the GPSDO yet because I do not have a GPS antenna (it is coming in the mail). But so that I don't just sit and wait for the GPS antennas to arrive, I wanted to try frequency synching the two USRP using a 1PPS reference input.
I generated a 1 PPS square wave using an arbitrary waveform generator with a 20% duty cycle at 5V high and 0V low. I fed the square waves into the "PPS in" input. On the GnuRadio, I set it to "unknown PPS" and clock source to "external" for both USRPs. I ran the flowgraph (which is just one B210 transmitting and one B210 receiving and sending the data to a QT frequency/constellation sink) and there is not synchronization. There is still a rotation in the constellation plot. How can I get the 2 USRPs frequency synched? Thanks, Daniel Cho
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