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])

 * ezcap EzTV666 USB 2.0 DVB-T/DAB/FM stick (Elonics E4000 tuner, [attachment:EZTV666.JPG picture])

 * 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/gr-osmosdr/ GNU Radio source block] for [http://sdr.osmocom.org/trac/ OsmoSDR] and rtlsdr is being created. '''Please install a recent gnuradio (>= v3.5.3) to use it.'''

 * Current progress: Rework to a library, support for multiple devices, tuner autodetection, FC0012 support

=== Building the software ===

==== rtlsdr library & capture tool ====

'''You have to install development packages for libusb1.0''' and can either use cmake or autotools to build the software.

Please note: prior pulling a new version from git and compiling it, please do a "make uninstall" first to properly remove the previous version.

Building with cmake:

{{{

cd rtl-sdr/

mkdir build

cd build

cmake ../

make

}}}

Building with autotools:

{{{

cd rtl-sdr/

autoreconf -i

./configure

make

}}}

The build executable (rtl_sdr) can be found in rtl-sdr/src/.

==== Gnuradio Source ====

'''The gnuradio source requires the rtl-sdr package and a recent gnuradio (>= v3.5.3) to be installed.'''

Please note: prior pulling a new version from git and compiling it, please do a "make uninstall" first to properly remove the previous version.

Building with cmake:

{{{

git clone git://git.osmocom.org/gr-osmosdr

cd gr-osmosdr/

mkdir build

cd build/

cmake ../

make

make install

ldconfig

}}}

==== Automated installation ====

Marcus D. Leech has kindly integrated the forementioned build steps into his gnuradio installation script at [http://www.sbrac.org/files/build-gnuradio]. This is the most user-friendly option so far.

=== 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 1.8e6 -f 392e6

}}}

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].

Please note: for realtime operation you may use fifos (mkfifo) to forward the iq data from the capture utility to the GRC flowgraph.

What has been successfully tested so far is the reception of FM/AM radio, [http://tetra.osmocom.org/ TETRA], [http://gmr.osmocom.org/ GMR], [http://svn.berlin.ccc.de/projects/airprobe/ GSM], [https://github.com/bistromath/gr-air-modes ADS-B] and [https://github.com/smunaut/osmo-pocsag POCSAG].

[[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).