[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Discuss-gnuradio] USRP2, WBX, and Mode S/ADS-B
From: |
Eric Cottrell |
Subject: |
[Discuss-gnuradio] USRP2, WBX, and Mode S/ADS-B |
Date: |
Mon, 22 Nov 2010 11:21:44 -0500 (EST) |
Hello,
I recently got the WBX daughterboard and updated GNURadio after a year or two
of hiatus. I really like the WBX so far, and have some ideas for receivers,
like an ACARS decoder that decodes multiple frequencies simultaneously, or a
trunked radio decoder that can decode the control channel and one or two voice
frequencies. A suggestion would be a WBR daughter board that is receive only.
I updated my Mode S / ADS-B code to work with the latest version of GNURadio
and the USRP2. The project now builds outside the GNURadio project. The USRP2
allows me to have a 10M sample rate receiver. I have to go back and update the
USRP1 version.
I like the updated scope sink. It is easier to use and I was able to find some
bugs, including a few stupid bugs, in my code. It was interesting using the
scope with various antenna and wideband preamp combinations. The preamp with a
1/4 wave antenna worked good. A colinear decreased range because of a raised
noise floor and increased interference. I moved the colinear to my roof
without the preamp and get a maximum range from 120 to 210 miles depending on
direction. I had it up 25 feet off the roof until a rainstorm and wind bent
the bottom mast section and now it is 15 feet off the roof. This cut down the
range a little. I have a DPD Productions 1090 MHz antenna on order that should
really fill out the range.
My code implements most of the RTCA recommendations in Appendix I of DO-260B.
I thought I had a good receiver, but as I fix bugs in my code the receiver
performance is improving.
http://www.faa.gov/about/office%5Forg/headquarters%5Foffices/ato/service%5Funits/nextgen/research%5Ftech%5Fdev/eng%5Fdev%5Fserv/adsb/wg3/Meetings31/media/pdf/1090-WP31-04.pdf
I only know some basic python so I have external C++ programs that decode the
log files rather than doing the decoder in Python. It is an advantage when I
spot a decoding error. I fix it and run the same log file through the decoder.
I am looking at implementing a socket interface so my code will work with
Planeplotter and other programs.
I want to try using a matched filter for preamble detection and a method that
packages the raw samples in a structure when it detects a preamble. The
following blocks work on this structure instead of a stream.
There are now several hardware platforms for decoding Mode S and ADS-B, mostly
from Europe. The SBS-1 implements a complete receiver/decoder using a FPGA and
possibly a soft microprocessor. The RadarBox sends the raw bits over the USB
and decoding is done on the PC. These are the major players. I was surprised
to see at least three other devices.
http://www.radargadgets.com/
http://www.auroraeurotech.com/avionics/
http://rxcontrol.free.fr/PicADSB/index.html
This seems like such a niche market and yet there are at least five hardware
solutions and two GNURadio solutions, including mine. I would like to compare
my code with a couple of other receivers to see how good it is.
73 Eric
[Prev in Thread] |
Current Thread |
[Next in Thread] |
- [Discuss-gnuradio] USRP2, WBX, and Mode S/ADS-B,
Eric Cottrell <=