24 June 2012

GQRX running nicely on HF with a USRP B100 and BasicRx

Tonight I've been using GQRX with my USRP B100, this time with the BasicRx daughterboard fitted, and a direct connection to my HF wire antenna.

It seems pretty good so far.  I've just been listening to some UK stations on 40m.

8 June 2012

RTL-SDR port of gr-air-modes feeding Xastir

After some finger trouble getting the RTL-SDR port of gr-air-modes working, I've now bodged that too for a Xastir feed.  I'm surprised to say this, but compared to the USRP B100 & WBX combination, this is working amazingly well.  So far I've had good tracks out to 137 miles, whereas the best I'd got in 6 days with the USRP/WBX was 90 miles.

This includes two tracks in Dutch airspace, one arriving and one departing.  Pretty amazing for a device that was overpriced at £25!

And a bit further again, 157 miles:

He came right past me and then on out to the west, being tracked for 213 miles.  Note that the packet counts are the number of position reports being forwarded to Xastir.  Many more ADS-B frames are being received than that.

And something out in the North Sea. Didn't see anything that far out up there with the USRP/WBX.

More ...

3 June 2012

ADS-B in Xastir with gr-air-modes

I find that while gr-air-modes is great for decoding ADS-B data, using Google Earth to view it in is a bit of a drag.  As I tend to have Xastir running on my laptop most of the time, I thought that it would be cool to plot aircraft tracks in that instead.   I decided on a very dirty hack to feed ADS-B data from gr-air-modes into Xastir. You can see, in the screen shot above, data received with a USRP B100 and WBX  with a discone in the loft and a cheap preamp.

In order to get this to work, you will have to edit the modified modes_kml.py file and replace mycall and mypass:

mycall = "MYCALL"
with something suitable, typically generated with the callpass utility.  Then configure Xastir to Enable Server Ports, and you should see something like this in the output of uhd_modes.py

/usr/local/bin/xastir_udp_client localhost 2023 MYCALL MYPASS "4196473>ADS-B:=5247.99N/00139.38E^035/462/A=033350BAW768  "
Received: ACK
If you don't get an ACK, it isn't going to work.

The file is modified from vanilla upstream, not from the rtl-sdr fork.

You must enable the kml output in order to get this to work, something like this:

./uhd_modes.py -g 50 -K ~/adsb.kml -a

Please don't feed (igate) ADS-B data into the APRS-IS. I don't think it is wanted.  I'f I'm wrong in this regard please let me know.

If you need to get some maps in your Xastir, I recommend enabling Automaps for  Online/OSM_tiled_Mapnik.geo in the Map Chooser properties dialog.