FM RDS Stereo transmitter using gnuradio

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

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

FM RDS Stereo transmitter

Hardware

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

Software

• Ubuntu Linux 10.04
• Gnuradio 3.3
• Jack open Audio connection kit
• gr-rds project on CGRAN (by Dimitrios Symeonidis )
• Jack FM RDS Stereo gnuradio python script

Setup

• Download and install all software mentioned in the previous section
• Download and install gr-rds project (run also install-grc.sh 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 http://maxxima.mine.nu:8000

• 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.

Source

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