DVB-T sticks based on the Realtek RTL2832U can be used as a cheap SDR, since the chip allows transferring the raw I/Q samples to the host, which is officially used for DAB/DAB+/FM demodulation. The possibility of this has been discovered by the V4L/DVB kernel developer Antti Palosaari.
The RTL2832U outputs 8-bit I/Q-samples, and the highest theoretically possible sample-rate is 3.2 MS/s, however, the highest sample-rate without lost samples that has been tested so far is 2.8 MS/s. The frequency range is highly dependent of the used tuner, sticks that use the Elonics E4000 offer the best range (64 - 1700 MHz).
So far, the following devices are supported:
- ezcap EzTV668 USB 2.0 DVB-T/DAB/FM stick (Elonics E4000 tuner) (sources: AliExpress, Dealextreme)
- ezcap EzTV666 USB 2.0 DVB-T/DAB/FM stick (Elonics E4000 tuner, picture)
- Hama nano DVB-T stick (Elonics E4000 tuner)
- Terratec NOXON DAB/DAB+ USB-Stick (Fitipower FC0013 tuner)
People over at reddit are collecting a list of other devices that are compatible.
Other sticks based on the RTL2832U might be added in the future as well.
This is the PCB of the ezcap-stick:
More pictures can be found here.
rtl-sdr is a commandline tool that can initialize the RTL2832, tune to a given frequency, and record the I/Q-samples to a file.
The code can be checked out with:
git clone git://git.osmocom.org/rtl-sdr.git
It can also be browsed on http://cgit.osmocom.org/cgit/rtl-sdr/
- A GNU Radio source block is being created
Building the software
To build it, simply run 'make' in the src/-directory and make sure you have libusb1.0-0-dev installed.
Example: To tune to 392.0 MHz, and set the sample-rate to 1.8 MS/s, use:
./rtl-sdr /tmp/out.bin -s 1800000 -f 392000000
If the device can't be opened, make sure you have the appropriate rights to access the device (udev-rules, or running it as root).
- If the samples are written to a harddrive, and not a ramdisk, samples may get dropped. An improved version with proper buffering and asynchronous usage of libusb is in the works.
Using the data
To convert the data to a standard cfile, following GNU Radio Block can be used:
The GNU Radio Companion flowgraph (rtl2832-cfile.grc) is attached to this page. It is based on the FM demodulation flowgraph posted by Alistair Buxton on this thread.
- rtl2832-cfile.png (23.8 KB) - added by steve-m 2 weeks ago.
- ezcap_top.jpg (177.7 KB) - added by steve-m 2 weeks ago.
top view of the ezcap PCB
- rtl2832-cfile.grc (8.6 KB) - added by steve-m 2 weeks ago.
GRC flowgraph for the RTL2832 file format
- rtl-sdr-gmr.png (42.4 KB) - added by steve-m 2 weeks ago.
spectrum view of GMR carriers
- EZTV666.JPG (163.3 KB) - added by laforge 5 days ago.
Similar but smaller EZTV 666 receiver