software radio playing

I bought a cheap software radio to plug into my Mac. I have no idea what I’m doing and no proper antenna, but just bashing around with gqrx I’m able to listen to FM radio and understand roughly what’s going on.

Even better, I just got dump1090 running; it’s a decoder for 1090S airplane transponder signals. Even better I happened to catch Air France 083 from San Francisco to Paris, a flight I’m happy to say I’ve been on myself a few times! I’m amazed at how fast they send data, many reports a second.

Getting the software working on my Mac wasn’t too hard. I installed libusb via Homebrew, then compiled librtlsdr from sources. Didn’t install that, just hacked the dump1090 Makefile to find stuff in /tmp or wherever it happened to be. My modified Makefile plus some sample output below.

Update libusbx may be a better choice than libusb. And rtlsdr is packaged in a HomeBrew fork you can tap for GNU Radio.

CFLAGS=-O2 -g -I/tmp/rtl-sdr/include/ -Wall -W `pkg-config --cflags librtlsdr`
LIBS=-L/tmp/rtl-sdr/build/src/ -L/usr/homebrew/Cellar/libusb/1.0.9/lib/ -lrtlsdr -lpthread -lm

$ ./dump1090 --interactive
Hex    Flight   Altitude  Speed   Lat       Lon       Track  Messages Seen .
--------------------------------------------------------------------------------
ac4d44          0         0       0.000     0.000     0     5         48 sec
a78dd7          0         0       0.000     0.000     0     28        17 sec
a8b805          10950     0       0.000     0.000     0     146       3 sec
3965a9 AFR083   11875     346     37.890    -122.348   48    608       23 sec

$ ./dump1090
CRC: c3e472 (ok)
DF 0: Short Air-Air Surveillance.
  Altitude       : 11300 feet
  ICAO Address   : a26fc9

*00c1879c1bd991;
CRC: 1bd991 (ok)
DF 0: Short Air-Air Surveillance.
  Altitude       : 11300 feet
  ICAO Address   : a26fc9

*00c6079cc3e472;
CRC: c3e472 (ok)
DF 0: Short Air-Air Surveillance.
  Altitude       : 11300 feet
  ICAO Address   : a26fc9

*59a26fc99c4306;
CRC: 9c4306 (ok)
DF 11: All Call Reply.
  Capability  : Level 2 (DF0,4,5,11)
  ICAO Address: a26fc9

$ ./dump1090 --raw
Found 1 device(s):
0: Realtek, RTL2838UHIDIR, SN: 00000001 (currently selected)
Found Rafael Micro R820T tuner
Max available gain is: 49.60
Setting gain to: 49.60
Exact sample rate is: 2000000.052982 Hz
Gain reported by device: 49.60
*8d4005e2583d0135f7fdf5514966;
*02c18790ae0146;
*8d4005e2200815f2e37820027da5;
*02c18790ae0146;
*8d4005e2583d04ca30ac60c73091;
*02c18790ae0146;
*20000790eda525;
*02c60790763ca5;
*5d4005e2dd7ccb;
*02c18790ae0146;
*02c18790ae0146;
*8d4005e29900c99d28060e63ed38;

Here’s a screenshot of GQRX while tuned to 1090MHz. I think there’s at least one airplane transmitting when I took this; hard to be sure. There’s some horizontal lines that I’m guessing are the signal. It’s so faint above the noise floor, I’m sort of amazed it works.

Screen Shot 2013-04-24 at 8.48.13 AM

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