Tuesday, September 11, 2012

ADS-B using Ubuntu and the RTL2832

The next task for the RTL2832 was  to decode aircraft transmitting A-DSB using Ubuntu. Doug G4DZU had previously pointed me at a link http://www.hamradioscience.com/the-rtl-2832u-sdr-and-ads-b/ with an idiots guide to doing it , so it was time to try
Installing gnuradio took one line (and patience):-

wget http://www.sbrac.org/files/build-gnuradio && chmod a+x ./build-gnuradio && ./build-gnuradio

dinner and desert  and a coffee later it finished. Time to see if it worked:-

rtl_test -t
Found 1 device(s):
  0:  Generic RTL2832U (e.g. hama nano)
Using device 0: Generic RTL2832U (e.g. hama nano)
Found Elonics E4000 tuner
Supported gain values (14): -1.0 1.5 4.0 6.5 9.0 11.5 14.0 16.5 19.0 21.5 24.0 29.0 34.0 42.0 
Benchmarking E4000 PLL...
[E4K] PLL not locked for 52000000 Hz!
[E4K] PLL not locked for 2217000000 Hz!
[E4K] PLL not locked for 1109000000 Hz!
[E4K] PLL not locked for 1249000000 Hz!
E4K range: 53 to 2216 MHz
E4K L-band gap: 1109 to 1249 MHz

looks like mine works 53-1108MHz & 1250-2216MHz, Impressive!

next install gr-air-modes:-

git clone https://github.com/bistromath/gr-air-modes.git
cd gr-air-modes/
mkdir build
cd build
cmake ..
sudo make install
sudo ldconfig
Launching the programme with 
uhd_modes.py -d -P 
with a piece of wire in the rtl283 antenna socket resulted in decodes from one aircraft almost overhead. Time for a better 1090MHz antenna. The J pole previously used was easy to build from 2 pieces of semi rigid cable so time to make another.It was tuned with a tracking generator/directional coupler/ spectrum analyser and achieved 32dB retun loss after tweaking. Putting this on the end of 35' of cable in the loft resulted in many more decodes and a torrent of data in the terminal:- 

Next time to plot the data. The article  pointed to Virtual radar server at http://www.virtualradarserver.co.uk/Mono.aspx so this was installed. Launching it with and clicking on the http link for local host resulted in the following map with 8 aircraft:-

The rtl2832 is not as sensitive as the Modesbeast I also have but it is only 5% of the cost!

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