Information carried by waves nobody can see: the wave and the decibel, the circuits of a radio, the ways a voice or a bit rides on a carrier, the lines and antennas that launch it, the paths it takes and the noise it arrives in, the receivers, transmitters and software radios that make and catch it, and the systems built from all of it. See every signal on an analyser, and hear it.
This course never transmits, and it is not a licence: transmitting needs a licence on almost every frequency, and private communications are protected by law. Every signal on these pages is synthesised by the page; your progress stays in this browser. Not affiliated with or endorsed by any regulator, standards body, manufacturer or organisation mentioned here; trade names belong to their owners.