Eric A. Cottrell wrote: > Hello, > > I got Mode S and ADS-B receiving working. I dump the messages to > standard output for redirect to a simple log file. Simple programs take > the log and decode it into English. I have not decoded all the messages > yet like Airborne Velocity. This is great news. Have you already got an svn accoupt so you can commit your code into a development branche. Or is your code available in an other way?
Greetings, Martin > > Tick: Sat Apr 28 08:43:52 2007 > Extended Squitter A/F: a6b55a Extend Cap: Unassigned 5 > Airborne Position O ln: -70.949388 la: 42.521745 Alt: 6100 > All-Call Reply A/F: a6b55a Extend Cap: Unassigned 5 > Short Altitude A/F: a6b55a Airborne No Downlink Request Alt: 6100 > Tick: Sat Apr 28 08:43:54 2007 > Extended Squitter A/F: a6b55a Extend Cap: Unassigned 5 > Airborne Velocity > > I was having problems with GNURadio stopping while trying to receive > from the USRP. It seemed like the USB stream would stop. I thought it > was the laptop so I setup a Core 2 Duo system. The problem still > occurred. I "fixed" the problem by removing the TVRX board from RXB and > moving the DVB board from RXA to RXB. Now I can log all day. > > One neat little program I use makes a kml file out of the positions and > I use Google Earth to see how good the range is. I can only receive > stuff up to 20 or so miles out. There are a number of Aircraft with > ADS-B that use Boston or fly over on the way to Europe. > > As I am reading technical articles and other information I see the > techniques progressed as 1090 MHz got more crowded and more powerful DSP > chips became available. Mode S started out using simple receivers with > pulse edge timing or centered sampling of pulse amplitudes. A radar > site sends interrogations at their Pulse Repetition Frequency so the > maximum reply rate was under 450 per second. FRUIT became a problem as > more sites came on-line and aircraft started using 1090 MHz for TCAS. > FRUIT as in False Replies Uncorrelated In Time. Basically overlapping > of different Mode S signals or Mode S with Mode A/C pulses. One > interesting article outlines using 10 or 8 MSPS for the sampling rate > and using factors such as amplitudes of pulses being within 3 db of each > other and the effects of beat frequencies of interfering Mode S signals > to determine if a bit is a one or a zero. So this is turning into an > interesting DSP and data decoding experiment. > > I suspect that I am in a high FRUIT environment and my limited range is > due to the basic receiver techniques I am using and the Discone Antenna. > I am currently implementing a better receiver in code and may put up a > 1090 MHz antenna with a preamp. > > Another interesting project is to also receive the 1030 MHz > interrogations and figure out the range and bearing of Mode S aircraft > by the timing between the interrogations and replies. > > 73 Eric > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
