In the last period, the software defined radio starts to become more and more popular, due to it’s obvious advantages over the analog radio. With SDR, basically you can do almost everything, no matter how complicated the modulation and demodulation techniques are used.

This concept is not new, but the high performance electronics available for low prices have rendered practical many things. Now, it costs only 20$ !

Today, a cool SDR can be built using only an USB FM / DVB-T capture device based on the RTL2832U chipset from Realtek. The frequency range depends on the dongle. Elonics E4000 can be tuned on frequencies ranging between 64 MHz and 1.7 GHz, the IF signal is sampled by the 8 bit ADC and the device sends the raw samples. That’s quite impressive for a 20$ device.

There is even a source block which allows you to use those devices with GNU Radio and do all kind of cool stuff like grabbing GPS data or creating an aviation traffic mapper.

There is already a functional command line program which captured data from those dongles. You can read more on their page at http://sdr.osmocom.org/trac/wiki/rtl-sdr

The GNU Radio block can be found here: http://wiki.spench.net/wiki/Gr-baz#rtl_source_c