Randomly saying "Unable to set BB rate"

I am trying to transmit on one SDR and receive on another SDR. Both are ADALM-PLUTO with two different IP addresses. The one that transmits never seems to have errors, but the one that receives often says "unable to set BB rate". I am aware this implies a sampling rate issue, and I am sampling at 1M  which should be well within the range this can handle (the TX also samples at 1M and never has issues). What is confusing is that sometimes I will run the RX GNU Radio program and it will run fine* , but then I can close it and launch it without changing anything and it will say this error 

self.iio_pluto_source_0 = iio.pluto_source(device_uri, 5651*1000000, samp_rate, 20000000, 32768, True, True, True, 'manual', 30, '', True)
File "/usr/lib/python3/dist-packages/iio/iio_pluto_source_swig.py", line 92, in make
return _iio_pluto_source_swig.pluto_source_make(*args, **kwargs)
RuntimeError: Unable to set BB rate

* I do get these warnings, which may be of use, but I think these are mostly pertaining to GUI usages.: 

QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
Unable to write attribute out_voltage0_hardwaregain: -22
libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast

Does anyone have any idea how I can fix my SDR to consistently run at 1M sample rate, or even possibly run at higher sample rates. Also, when I am getting this error, running at a much lower sample rate does not fix it. 

Thank you!

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  • 0
    •  Analog Employees 
    on Apr 16, 2021 1:43 PM

    Hi Tyler, 

    When your sample rate is below 2.08 MHz, "Auto Filter" property of Pluto Sink block needs to be set to true so that a default filter is loaded. In the latest version of gr-iio, you wouldn't even be able to run the flowgraph otherwise. Are you loading an auto filter when the flowgraph runs without errors? What version of GNU Radio/gr-iio are you using?

    More generally, you will need to design a custom filter to suit your application when the sample rate is < 2.08 MHz. 

    - Srikanth

  • Hi Srikanth, 

    I am running GNURadio 3.8 on a docker image and that uses the latest version of ubuntu (20). I tried making the filter 2.08MHz like you were saying and that still did not seem to help that much. I was not using any custom filter previously. The file can sometime run perfectly fine, and then I close it and immediately run it again, and I get an error. 

  • 0
    •  Analog Employees 
    on Apr 20, 2021 1:49 AM in reply to TylerUW

    To be precise, the sample rate needs to be >= 2.084 MHz. When you set the sample rate to this number, is the error that you sometimes get the same as the one you described above - "Unable to write attribute out_voltage0_hardwaregain: -22", but without the "RuntimeError: Unable to set BB rate" error? If this is the case, it could be because the tuning range of the LO hasn't been updated to span 70M - 6GHz as shown here - Customizing the Pluto configuration [Analog Devices Wiki]. If this is not the case, can you provide a screenshot of your flowgraph?

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