Combining the bandwidth of multiple RTL-SDRs: Now working in GQRX!

A few days ago we posted how Oliver, an RTL-SDR experimenter, managed to (incoherently) combine the bandwidths of two RTL-SDR dongles to create a 4.4 MHz FFT display in GNU Radio. Now Oliver has taken this idea further and produced an updated version of his GNU Radio program

Oliver’s GNU Radio program is now capable of combining four RTL-SDR dongles and is now also capable of piping the output via a FIFO to GQRX. With four RTL-SDR dongles you can get a total bandwidth of 8.4 MHz. He also writes that it is even possible to listen to analog signals that are in overlapping areas.

Four RTL-SDRs producing a total of 8.4 MHz of bandwidth in GQRX.
Four RTL-SDRs producing a total of 8.4 MHz of bandwidth in GQRX.


  1. Pierre

    I am a financial software sales person, so I am used to have to convince my audience that I have something worth learning about in 30 seconds. What does that screenshot exhibit, except a clock-spurious spike at 432 MHz? Or have I missed a video? I have no serious doubts that there is some interesting SDR DSP chain in this story, but showing an empty ISM band is not, in my humble newbie ham opinion, an obvious\unquestionable evidence of having achieved the claimed results. Show us more Olivier!

    • fusionimage

      a single rtl-sdr dongle can provide 2.4 MHz of bandwidth, the screenshot shows 4 dongles with 8.4 MHz bandwidth (not 9.6, due to overlaps)
      and yes, there is some black magic dsp processing in gnuradio, just download the flowgraphs at my blog

  2. Fabio

    How about syncing data with a reference signal every now and than in order to achieve a near coherent digitizing from all dongles.

  3. Fabio

    Using multiple receivers could be interesting also to perform noise reduction. Combining samples over the same band could reduce the Gaussian Noise. Filtering out the signal from a reference receiver with the RF input terminated with a dummy load could be used to reduce system noise. Filtering out the signal from a reference receiver with reference antennas could be used to reduce other site specific noise. Would be nice to have such alternatives explored in a dynamic way, where you can trade sensitivity and bandwidth on the run.

  4. virender

    It’s mean that you can watch analog TV after combining multiple dongle because single RTL SDR doesn’t have enough bandwidth to properly watch analogue TV.

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