Bits of SDR

The hackspace is a bit quiet at the moment, we’re waiting for some room to set up our laser cutter.  NSME are kindly giving us some space and have even provided some fire extinguishers, optimistic that they are.  Hopefully by the beginning of April we will have space for it.

In the meantime, I did some tooling around with the RTL SDR dongle, the software support for which has come on marvellously, and after some fun following some guides on the ‘net, we were able to pick up the ADS-B location broadcasts of airplanes overhead – albeit in a very small range, due to the antenna in use that isn’t designed for 1.09GHz.
For the curious, I originally started with the rtl_adsb library that comes with rtlsdr these days (also worth investigating the rtl_tcp server if you want to leave your dongle in an RPi…).  This puts out the decoded broadcasts to an almost human-readable level.  I then installed the VirtualRadar software (which is cross platform) . . . which didn’t decode the messages at all (linked together via netcat).  It confirmed it received messages, and that they were not badly formatted, but couldn’t decode them either.
I then tried using this guide and used the gr-air-modes application instead.  The uhd_modes.py script it recommends has been replaced with rx_modes instead but the syntax is the same.  This wasn’t too painful for me as I already had gnuradio installed.  For those that don’t though, the latest in Ubuntu 12.10 is compatible with the osmocom extra sources.

One thought on “Bits of SDR

  1. Okay now you are going to want some software to decode and display the aircraft positions. Head on over to the Virtual Radar Server site and go to the Linux page . Follow the simple instructions on this page to install Virtual Radar Server and the Database Writer program. Be sure gr-air-modes is running and you are seeing data in the terminal window. Start the program and go to the base station setup an enter your computers IP address, do not change the port number. Close and restart the program and you should see “connected” at the bottom of the programs window. To see the map and the aircraft data click on the local link showed at the bottom of the programs window. You should now see the aircraft positions overlaid on a google map and other data about the aircraft displayed on the right. You may have to adjust the map to show your area. If you are seeing aircraft but no plots on the map, don’t worry everything is working correctly. This means that the aircraft are not transmitting type 17 messages that contain positional data. You can watch the terminal window and see what messages are being received. You may eventually see an aircraft plot if you are patient. Virtual Radar Server can also setup to run a public web server so that other people can see your plots if you are so inclined.

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