I recently bought an RTL-SDR dongle and an antenna to receive ADS-B messages. These are short packets of data, broadcast by every plane in the sky, to inform others of their position, heading, speed and other flight data. The transmission of these messages is mandatory for aircraft, as it prevents mid-air accidents. They are also unencrypted, which means anyone can listen to them. All you need is an antenna and a dongle to ingest the data on your PC (pictured above), which can be bought for less...