Getting Started with Wireless Communication – Setting up a Flight Tracking Receiver

We recently had a 16 year old student in our labs, and tried to teach him something about LTE, RF transmitters, spectrum analysis, and so on. Most of the stuff however was far too complex for him to understand, as many of the mathematical basics were missing. After talking to him for a day and doing weird measurements, it popped to my mind that I still have this DVB-T Stick and a Raspberry Pi at home, which might make a really cool project. So I brought both devices the next day and told the student to do some research on rtl-sdr.com and find a project he would like to do.

He wanted to track airplanes, as he found a flight tracking webserver could be easily implemented with the RTL-SDR stick and the Pi. What’s this flight tracking, anyhow? Airplanes are sending broadcast messages with information on their flight code, location, altitude, direction, speed, and many other information. The system is called ADS-B, Automatic Dependent Surveillance Broadcast, and the messages are modulated on a 1090 MHz carrier signal and sent once or twice every second.

adsb.jpg
from: http://jlcavionics.com/adsb.html

We just need the RTL-SDR Stick, an 1GHz vertically polarized antenna, and some receiver software. So we went to the lab and were soldering a simple dipole antenna with a length of roughly 7.5cm. Other antenna examples can be found on the project webpageof rtl-sdr.com. Then we downloaded dump1090-mutability software, the compilation was easy with standard tools.

Plugging everything together, holding the antenna out of the window starting the software, and immediately we received some messages! We were of course immediately googling at the coordinates, to see where the airplanes were located and were heading to.

2016-12-10-214239_1920x1080_scrot.png

It took us a 1 hour effort to build an antenna and compile the software, and could receive some digital radio messages from far away. Pretty cool, isn’t it?

On Teaching Wireless Communication – with a Raspberry Pi

Smartphones, PCs, Televisions, internet, cellular networks, Wifi, Bluetooth; we have seen dramatic increase in complexity of devices, servies, and technologies while theay are easier and easier to use. A huge step forward to enable use of technology not only to nerds and geeks, this trend also results in the fact that nearly nobody understands and nobody can explain his kids how these devices and systems work. Teaching and explaining wireless communication gets more and more complicated, as we lack simple examples and devices. Some decades ago, it was easily possible to disassemble and debug your TV, Radio, or other electrical equipment, make some experiments or try to fix it.

The current PISA report in Germany revealed, that students are good in Math and Science, but are heavily lacking interest in these fields. One of the projects targeted at fueling interest in programming and computers is the Raspberry Pi as simple learning platform for anything related to computing. The success is amazing, now having sold 10 million devices of the Raspberry Pi and fueling huge interest in the making and creating things.

There are plenty of cool and fun projects on the webpages like hackster.io. With these ideas, plans, and descriptions, a rewarding project can be very easily built. Questions on the basic principles of the project can follow, which can be answered by a friend, relative, or teacher. On the second hand, it’s very easy to experiment and to explore. The combination of getting started easily, rewarding projects and room for experimentation makes the major success of the Pi.

In the next couple of posts I will write how to use the Raspberry Pi together with cheap Hardware and open source software to conduct projects and experiments to learn something about wireless communication.