SDR, or Software Defined Radio, is a type of hardware radio that has a large bandwidth and scanning range, and is controlled by software. The RTL-SDR is a receive only SDR dongle that is based on the RTL2832U chip. This has a PPM temperature compensated oscillator (TCXO), SMA F connector, aluminium case with passive cooling, bias tee circuit, and break out pads for easy direct sampling modification.
 
The RTL.SDR has a maximum stable bandwidth of 2.4MHz, and a range of 500kHz - 1.7GHz.