FM RDS Stereo transmitter using gnuradio

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Information on the setup a software defined FM RDS Stereo transmitter using Gnuradio.

It has been made from the integration of a stereo transmitter (, gr-rds project on CGRAN and design from CRC.



  • PC
  • USRP1 Universal Software Radio Peripheral with WBX RF daugtherboard (50MHz-2.2GHz) (can work also with Basic TX with minor modifications)



  • Download and install all software mentioned in the previous section
  • Download and install gr-rds project (run also script in src/grc to install components for gnuradio companion, optional)
  • Download the Jack FM RDS Stereo gnuradio python script
  • Create the .asoundrc file in your home directory, "jackplug" is mapping of jack source to ALSA, defined in .asoundrc file in home directory

Startup procedure

  • Power and connect USRP1, with wbx board installed in A side (can be changed with minor modification to the script)
  • Start jack audio server using Jack Control (you need to have install jack audio server and tools)
  • Start Jack FM RDS Stereo gnuradio python script
  • Window will appear with the different settings to control frequency and gains of FM composite signal components
  • By default (depending on .asoundrc file) all source will be connected to the default system audio input (laptop microphone in general)
  • Play the audio of the content you want to broadcast on jack, for example, if you take an internet radio stream:
mplayer -ao jack
  • Connect the output of jack source to the input of gnuradio software transmitter using "connections" in JACK control

That's it

TO DO: fine tuning of gains for composite signal.


Jack crc fm rds tx.grc.png

  • Python script can be modified directly.
  • Gnuradio companion source file can be found HERE
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