Over on the Raspberry Pi Reddit discussion board user spfoamer has posted about his Raspberry Pi + RTL-SDR based outdoor ADS-B receiver. ADS-B stands for Automatic Dependent Surveillance Broadcast and is a signal broadcast by aircraft that contains information about their locations. With a receiver like the RTL-SDR and correct software you can make an aircraft radar.

In his design the Raspberry Pi transmits location data back to a PC via an Ethernet cable. In addition the Raspberry Pi is also cleverly powered via power over Ethernet (POE) which uses unused wires in the Ethernet cable itself to carry the power. Since he uses a 12V power source, to obtain the needed 5V to power the Raspberry Pi spfoamer uses a UBEC (Universal Battery Elimination Circuit) which is an efficient device that converts voltages from up to 23V down to 5V. Additionally, he uses a 1/4 wave ground plane antenna and a 1090 MHz bandpass filter to eliminate out of band interference.

On the Pi itself he runs PiAware and contributes his data to the FlightAware network.