Raspberry Pi & GQRX= SDR

Discussion in 'RFinderPi - Open Source radio interface based on R' started by W0CHL, Jun 30, 2017.

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  1. W0CHL

    W0CHL Ham Member QRZ Page

    I'm using a Raspberry Pi 3 and GQRX software for software defined radio. Easy to load the required files and the GQRX google groups people (especially Alex, the author of GQRX) are willing to help setup. The GQRX software typically runs about 45-50% of CPU time and a heatsink for the CPU is recommended. The download of 2.6 version is at gqrx,de .. It supports a bunch of different inexpensive RTL USB sticks. I'm using a NooElec stick and an upconverter with great results!
    Cheers,
    Jim W0CHL
     
  2. VA3VF

    VA3VF Guest

    Hi Jim,

    Is there a way to pipe the signal from GQRX to another application on the RPi3, a virtual audio cable of sorts?

    My goal is to have a self-contained WSPR/JT65/JT9 receiving station. The RPi3 works fine with WSJT-X, but it still needs an external receiver. I want to use an RTL-SDR dongle instead. GQRX works fine receiving FM broadcasters.

    The missing link is the virtual audio cable part.

    73 de Vince, VA3VF
     
  3. W0CHL

    W0CHL Ham Member QRZ Page

    You better check on the GQRX forum. I'm Alex would have that information. I'm only into GQRX by one week...
    Cheers,
    Jim
     
  4. WL7CG

    WL7CG Premium Subscriber QRZ Page

    I just got mine running here using a RTL-SDR dongle. I have the standard RPI 7" display and the GQRX display does not quite fit. It's working and I just need to determine the best setting for the pi.
     
  5. K1WTF

    K1WTF Premium Subscriber QRZ Page

    I don't have experience with the GQRX app, but is it just audio you want into another application? If it is, try something like this:
    pacmd load-module module-null-sink sink_name=Virtual0
    pacmd update-sink-proplist Virtual0 device.description=Virtual0
    pacmd update-source-proplist Virtual0.monitor device.description=Virtual0

    This creates a new input/output device with a monitor, named 'Virtual0'. Open 'pavucontrol' (if its not installed: 'sudo apt-get update && sudo apt-get install pavucontrol') and under the playback tab, assign the gqrx audio output to go to the Virtual0 device. Fire up your other app, and in pavucontrol under the recording tab, assign whatever the other app is to 'Virtual0'. If you want more than one virtual audio device, or want to name it something more useful, just change 'Virtual0' in each line to something else.

    Here's an example of 4 different chrome tabs playing into different virtual audio devices, and different wsjtx instances listening to each virtual audio device:
    [​IMG]
    [​IMG]
     
  6. K1WTF

    K1WTF Premium Subscriber QRZ Page

    Also a note, depending on the audio delay of the entire chain (rtl-sdr into gqrx) is too great, you may not be able to decode some digital modes. For example, my kiwi sdr and chrome can't decode FT8 because there's about a 2-3 second delay in the audio from realtime. JT65/JT9 works fine though.
     

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