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Using GrOsmoSDR as signal source

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András Retzler edited this page Feb 25, 2018 · 22 revisions

GrOsmoSDR is a GNU Radio block, which allows you to use variety of SDR hardware with OpenWebRX, including:

  • FunCube Dongle
  • bladeRF
  • ​HackRF
  • USRP
  • ​Fairwaves UmTRX
  • RFSPACE ​SDR-IQ, ​SDR-IP, ​NetSDR
  • RTL-SDR, RTL-TCP
  • MSi2500 based DVB-T dongles
  • ​SDRplay RSP
  • ​AirSpy

Step #1: You will need to install GNU Radio and GrOsmoSDR:

sudo apt-get install gnuradio gr-osmosdr

Make sure you have at least GNU Radio version 3.7.8.1.

📗 Since writing this article, a tool called osmocat.py has been released, which claims to do the same as steps #2-#6 below: https://github.com/roseengineering/osmocat

Step #2: Download osmocom_source.grc to the OpenWebRX directory.

cd openwebrx
wget https://gist.githubusercontent.com/ha7ilm/19d14e1394bd2e7015e6/raw/141720f8b2b6da725fbcfc8959ee4ea4547b53a8/osmocom_source.grc

Step #3: Execute the following:

mkfifo /tmp/osmocom_fifo

Step #4: Open osmocom_source.grc in GNU Radio Companion.

You can run GNU Radio Companion by:

gnuradio-companion

...then select File > Open and look for the osmocom_source.grc.

Double-click the osmocom Source block, and configure the receiver.

Maybe Device Arguments is the most important field, which allows you to select the receiver. The format is like this:

<receiver type>=<receiver id or path>
  • If you want to use RTL-SDR #0 (the first RTL-SDR connected), you should enter: rtl=0
  • If you want to use HackRF #0 (the first HackRF connected), you should enter: hackrf=0
  • If you have an RFSPACE SDR-IQ on port /dev/ttyUSB0, then you should enter:
    sdr-iq=/dev/ttyUSB0

There are many other options detailed on the Documentation tab.

osmocom_source

Step #5: Apply the same configuration to config_webrx.py. You will have to set at least the following settings:

  • center_freq
  • samp_rate

You will also have to uncomment the two relevant lines (and comment out the ones for RTL-SDR):

# >> gr-osmosdr signal source using GNU Radio (...)
#start_rtl_command="cat /tmp/osmocom_fifo"
#format_conversion=""

Uncomment like this:

start_rtl_command="cat /tmp/osmocom_fifo"
format_conversion=""

Step #6: Execute the flowgraph in GNU Radio Companion (F6 or Run > Execute). This will supply the I/Q data for OpenWebRX.

Note: next time you can just run python osmocom_source.py from the command-line.

Step #7: While the flowgraph in GNU Radio Companion is running (in the background), start OpenWebRX:

python openwebrx.py
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