GQRX Tips

21 Dec

Pulse Audio
Prior to installation of gqrx make sure pulseaudio is available during build by installing the following:
pavucontrol
pavumeter
pulseaudio-libs-devel

Install gqrx
git clone https://github.com/csete/gqrx.git
cd gqrx
mkdir build
cd build
qmake-qt5 ..
make -j8
sudo make install

Typical device strings
For the b200:
uhd,type=b200,nchan=1

For the X310 with LFRX in slot 2:
uhd,addr=192.168.1.13,subdev=B:A,nchan=1

For the X310 with WBX in slot 1:
uhd,addr=192.168.1.13,nchan=1

For the N210 with LFRX:
uhd,addr=192.168.1.11,subdev=A:A,nchan=1

When switching between devices in gqrx the gain control changes will segfault the application.  Fix this by deleting the “gains” section in:
~/.config/gqrx/default.conf

Sending gqrx audio to fldigi
Install fldigi with yum

Configure fldigi sound card to use pulseaudio, leaving server string empty

Launch pulseaudio volume control, and under recording tab, fldigi capture from monitor of built-in audio analog stereo, and set level to 0 dB.

Adjust fldigi waterfall upper signal level and signal range.

Sending gqrx audio to UDP

Streaming audio over UDP

Configure the network settings in the Network tab of the audio settings window:
UDP host: localhost
UDP port: 7355

Verify the data is coming through at the opposite end using netcat:
nc -l -u 7355
nc -l -u localhost 7355
nc -l -u 127.0.0.1 7355

Pipe the output of netcat to other applications.
The following example will send the audio to the ALSA player application:
nc -l -u 7355 | aplay -r 48k -f S16_LE -t raw -c 1

The following command line will re-sample the raw audio to 22.05 kHz and send it to multimon-ng and decode POCSAG data (thanks to André Schmelzer for this):
nc -l -u 7355 | \
sox -t raw -esigned-integer -b16 -r 48000 - -esigned-integer -b16 -r 22050 -t raw - | \
multimon-ng -t raw -a SCOPE -a POCSAG512 -a POCSAG1200 -a POCSAG2400 -f alpha -

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