SDR (Software Defined Radio) » rtl-sdr

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= rtl-sdr =

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 [http://thread.gmane.org/gmane.linux.drivers.video-input-infrastructure/44461/focus=44461 Antti Palosaari].

== Specifications ==

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).

== Supported Hardware ==

So far, the following devices are supported:

 * ezcap EzTV668 USB 2.0 DVB-T/DAB/FM stick (Elonics E4000 tuner) (sources: [http://www.aliexpress.com/product-gs/486876635-DVB-T-Digital-TV-USB-Dongle-Stick-With-FM-DAB-DAB--wholesalers.html AliExpress], [https://www.dealextreme.com/p/dvb-t-digital-tv-usb-dongle-stick-with-fm-dab-dab-44326 Dealextreme])

 * Hama nano DVB-T stick (Elonics E4000 tuner)

 * Terratec NOXON DAB/DAB+ USB-Stick (Fitipower FC0013 tuner)

People over at reddit [http://www.reddit.com/r/RTLSDR/comments/rbqfz/rtlsdr_compatibility_list_work_in_progress_please/ 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:[[br]][[br]]

[[Image(ezcap_top.jpg,50%)]][[br]]

More pictures can be found [http://www.steve-m.de/pictures/rtl-sdr/ here].

== Software ==

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/

=== Progress ===

 * A [http://cgit.osmocom.org/cgit/osmo-sdr/log/?h=dimitri/rtlsdr 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.

=== Usage ===

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).

=== Known problems ===

 * 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:[[br]]

[[br]][[Image(rtl2832-cfile.png)]][[br]][[br]]

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 [http://thread.gmane.org/gmane.linux.drivers.video-input-infrastructure/44461/focus=44525 on this thread].

What has been successfully tested so far is the reception of [http://tetra.osmocom.org/ TETRA], [http://gmr.osmocom.org/ GMR] and [http://svn.berlin.ccc.de/projects/airprobe/ GSM].

[[br]][[br]]

[[Image(rtl-sdr-gmr.png)]][[br]]

Multiple GMR-carriers can be seen in a spectrum view with the full 3.2 MHz bandwidth (at 3.2 MS/s).