A $40 Software-Defined Radio

The last time I ventured into the waters of software-defined radio (SDR) was seven years ago, when I reviewed Matt Ettus’s Universal Software Radio Peripheral. While it’s an excellent product, the basic motherboard at the time cost US $550; daughterboards for different frequency ranges cost $75 to $275 [see “Hardware for Your Software Radio,” IEEE Spectrum, October 2006]. And I spent more than a few frustrating hours compiling the needed software on my MacBook Pro. This time I was able to get my feet wet for about $40—and the software took about 2 minutes to download, install, and run.

This minor miracle was made possible by Finnish engineering student and Linux developer Antti Palosaari. Last year, he discovered an unexpected feature of the RTL2832U demodulator chip made by Taiwan’s Realtek: Intended for decoding European HDTV broadcasts in inexpensive USB dongle-type receivers, the RTL2832U chip can also output a raw digital stream describing the amplitude and phase (so-called I/Q data) of signals over a wide range of frequencies. [See More]