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DCU TechWeek: Hacking Radio

Thanks for coming to my talk; I hope you enjoyed it and that it gave you some ideas on how you can play with radio. The fundamentals of radio are pretty straightforward, and apply to all radio transmitters and receivers, no matter how complex they are otherwise. Knowing these basic building blocks are often enough to get you started in building your own radio circuits or hacking stuff together to make radio do what you want it to do. Radio was built on people tinkering with stuff!

If you want any tips or have questions please grab me and I’ll try to point you in the right direction. I’m on Redbrick chat (lithium) so feel free to poke me.

Talk slides

The slides for the talk are on Google Docs here.

General links

www.rtl-sdr.com – This is a great site for getting cool ideas on how to use your USB software-defined radio. Searching for things like ‘ADS-B’ on the site will give you instructions on how to set up your own aircraft “radar” system, like I demonstrated, but there’s loads of stuff in there. Their quick-start guide is especially useful if you want to get your own USB radio like the one I used and get it set up with decent software: you can pick one up on eBay or Amazon for between €10 and €25, depending on the seller.

Raspberry Pi transmitter – This is ridiculously easy to set up and run. One of the pins on the RPi acts as an antenna, so you can transmit stuff around your house.

websdr.ewi.utwente.nl:8901 – This is a good online radio receiver based in The Netherlands. Simply put in the frequency you want and hit enter. The default settings are good for listening to normal broadcast stations. Use CW for listening to Morse Code, and USB or LSB for amateur radio operators.

priyom.org – A really good resource for numbers stations. The schedule gives a Google calendar of what’s coming up, and the link at the top of the page just under “Next station in X minutes” will bring you to the correct tuning on the University of Twente online receiver mentioned above, ready for you to listen

www.irts.ie – The Irish Radio Transmitters Society look after radio exams required for getting a transmission licence. If you’re thinking about getting an amateur radio licence, check them out.

Aircraft/ADS-B

If you want to do the aircraft radar thing, the stock antenna that comes with the USB radio will pull in signals from around Dublin. You can build a special antenna that will extend this range much further. My one gets aircraft from as far as Wales very easily. Instructions are on this site at: http://ei6gsb.conorfarrell.com/construction/constructing-an-ads-b-collinear-antenna/

To decode ADS-B signals, use the algorithm outlined here: http://www.lll.lu/~edward/edward/adsb/DecodingADSBposition.html

To get on-screen radar, you will need the USB SDR above, and also this software: http://rtl1090.web99.de/ (download the ‘scope’ beta version). Unfortunately it didn’t work during the talk, but here is what you should have seen!

1090a

These are the raw frames broadcast by the aircraft (modified slightly by the rtl1090 software)

1090b

This is the list of aircraft being picked up. Note the callsigns, altitude (with ascending descending info), airspeed, groundspeed, and signal strength.

This is the "radar"

This is the “radar” scope that plots the information contained in the ADS-B frames

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