The RTL-SDR is a very inexpensive USB dongle that functions as a radio scanner on your computer, allowing you to receive live radio signals in your area (without needing the internet). Depending on the model, it can receive frequencies from 500 kHz to 1.75 GHz. Most of the software for the RTL-SDR is community-developed and offered free of charge. The RTL-SDR does not transmit; it is only a receiver.
The origins of the RTL-SDR can be traced back to mass-produced DVB-T TV tuners based on the RTL2832U chipset. Thanks to the collaboration of Antti Palosaari, Eric Fry, and Osmocom (particularly Steve Markgraf), it was discovered that the I/Q data of the RTL2832U chipset could be directly accessed, allowing the DVB-T TV tuner to be converted into a wideband software-defined radio using a custom software driver developed by Steve Markgraf.
The RTL-SDR is also known as the RTL2832U, DVB-T SDR, DVB-T dongle, RTL dongle, or the "cheap software-defined radio."
