The RTL2832 is an IC produced by Realtek Corporation to demodulate DVB-T (digital TV) signals and send them to a host computer over the USB bus. It has an additional mode designed to allow reception of consumer FM radio, and this is achieved by capturing I/Q samples and forwarding them to the host computer for demodulation and playback.
This feature was discovered by a Linux kernel developer while writing a Linux driver for devices using this chip, and the discovery was quickly put to use by implementing drivers for SDR programs such as HDSDR, turning these devices into cheap Software Defined Radio (SDR) receivers. As the devices have a wide tuning range (typically continuous from 64MHz to 1.7GHz) they are very flexible.
As so many devices have been produced based around this chip, it is difficult to reliably tell which devices are suitable for use with SDR. There is a community maintained list on Reddit documenting which devices are known to work.
The SDR mode of the chip is theoretically capable of capturing up to 3.2MHz of the RF spectrum at one time, however the largest sample rate successfully received without sample loss is 2.8MHz. This means any signal to be demodulated must fit within 2.8MHz of the RF spectrum. For comparison, a consumer FM radio signal has a bandwidth of around 120kHz, and a TV signal (with audio) is 6-8MHz.
The RTL2832 chip does not perform any RF tuning itself, so it must be paired with a suitable tuner chip to enable signal reception. At the time of writing, the available USB devices use one of the following tuner chips:
|Tuner||Advertised frequency||Actual frequency|
As the tuner chip dictates the frequencies available for reception, the Elonics chip is typically favoured as it has the greatest frequency range.