Monday, December 31, 2012

Airborne!

I told Tim, G4VXE, about the trouble I was having getting a USB TV dongle to work as a VHF/UHF SDR and he emailed me a couple of files. One of those was an installation script which I suspect is the same one mentioned in the article "Cheap and Easy SDR" in the January 2013 QST which a couple of people mentioned. I had read this article at least twice and then forgotten all about it, which is a shame as it would probably have saved me several hours of abortive messing about.

I ran the script once and it seemed to work but I still could not get anything out of my ezcap dongle. I then used MagiCure to turn back the clock a few days to before I started messing about, and then ran the script again. This time it worked. I ran SDR# and it appeared to be working. I set the frequency to somewhere in the FM broadcast band and within a couple of minutes I was listening to Classic FM on 99.9MHz in stereo.

SDR# receiving BBC Radio 3 in the FM broadcast band
This was all very good, but I have any number of radios able to receive FM radio. I wanted to try receiving ADS-B aircraft beacons. But although both ADSB# and RTL1090 (ADS-B decoders) seemed to work (i.e. didn't display any error messages) they were not decoding any data. I used SDR# to monitor 1090MHz, the ADS-B frequency, and I could not see or hear any signals, though I have no idea what they are supposed to sound like.

I decided to reinstall the second dongle which had worked as a TV receiver. Then, on a whim, I thought I would try running SDR# to see if it would connect with the other dongle. To my great surprise, it did. What's more, it seemed much livelier (more sensitive) than the ezcap dongle. I tried both RTL1090 and ADSB#. Both worked and immediately started decoding packets! I started up ADSBScope and within a few seconds aircraft began to appear on the screen!

ADSBScope plotting aircraft overhead at G4ILO
After a while I got cocky and decided to see if there were any other free aircraft-plotting applications I could try, so I downloaded VirtualRadar. After a bit of trial and error I found the right settings to connect with ADSB# and I was soon seeing the aircraft passing overhead plotted on a Google map.

VirtualRadar plotting aircraft overgead at G4ILO
Strangely enough, both RTL1090 and ADSB# think they are talking to the ezcap dongle! Not surprising I suppose as I have not installed any other drivers. It would be nice to be able to use the equipment as a TV receiver as well but I suspect that would break everything! I should probably quit while I am still ahead.

Both ADSBScope and VirtualRadar are nice applications, and I couldn't say one is better than the other. VirtualRadar runs as a web server and you have to point a web browser at it to see the display. It shows more information such as the starting and destination locations of many aircraft, which is interesting. But curiously VirtualRadar does not display aircraft callsigns (like G-ADSB) while ADSBScope does.

This is looking to be an academic question as this morning ADSBScope has decided to stop working. It won't talk to either RTL1090 or ADSB# but complains repeatedly about a "comm error." Ah well, at least VirtualRadar and SDR# are still working.

5 comments:

Tim said...

Good news Julian!

I'm delighted it's all working now and that you are decoding some aircraft. You can get the registrations displayed by Virtual Radar Server. You need a file called basestation.sqb which is what the Virtual Radar boxes create. You should be able to find one on the net to download, but if not, email me and I'll send you mine.

You'll find a spot in the Virtual Radar Server config where you can point the server at this file and you should be all set.

I'm not sure what's happened to ADSBScope. If all else fails - uninstall and reinstall!

Vy 73 and Happy New Year,

Tim

g4fre said...

my experiences using planeplotter and virtualradar are at g4fre.blogspot.com for dec 16. the r820 dongle is much more sensitive for adsb than the old e4200

dave

g4fre

Julian Moss said...

Interesting, Dave. My ezcap dongle is the one that's deaf. The other one isn't marked ezcap (and it has a strange sub-miniature coax connector on it) but it works with the same drivers and seems more sensitive.

Gavin Stirling said...

I have flown both GEZUA and GEZAU! I wonder what day you decoded the ADS-B as it may have been me doing the flying :-)

Regards,
Gav
GM0WDD

Julian Moss said...

I think it was Sunday Dec 30. I'll give you a wave next time you fly over!

Julian, G4ILO