On 10/24/2010 07:22 PM, Andrea Montefusco wrote:
is it thinkable to operate the decoder at a lower sample rate ? (e.g. at 2 MS/s or even less)
I found this reference http://www.tech-software.net/adsb_decode1.php in a Eric A. Cottrell message that explains why we need an high sample rate: [...] I thought that the USRP and DVB tuner board could also receive ADS-B and Mode S. I did not know if my discone and long coax run would work. So I did some experiments. I used the fft and oscilloscope programs to check for activity. I did see activity on 1090 MHz. I then modified the oscilloscope program to do AM detection with the gr.complex_to_mag() function. I saw various pulse trains that look correct. There were some short ones that look like old transponders and longer ones that look like Mode S. I found the range of good gain settings was narrow (31 to 35) with 33 to be the best. I found the decimation of 16 gave good pulse shapes. The pulse timings are in 500 nS units so you need 250 nS sample times at least. [...] So, I believe there is no hope to decode this stuff with HAM SDR hardware. *am* --------------------------------------------------------- Andrea Montefusco iw0hdv http://www.montefusco.com tel: +393356992791 fax: +390623318709 --------------------------------------------------------- _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
