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rtl-sdr
DVB-T dongles 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.
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 2.4 MS/s. The frequency range is highly dependent of the used tuner, dongles that use the Elonics E4000 offer the widest possible range (see table below).
Supported Hardware
Note: Many devices with EEPROM have 0x2838 as PID and RTL2838 as product name, but in fact all of them have an RTL2832U inside.
Realtek never released a chip marked as RTL2838 so far.
The following devices are known to work fine with RTLSDR software:
If you don't know where to buy one or if you are just looking for a trustworthy source, try [url]http://shop.sysmocom.de/t/software-defined-radio[/url]
People over at reddit are collecting a list (v2) of other devices that are compatible.
Other dongles 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.
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 [url]http://cgit.osmocom.org/cgit/rtl-sdr/[/url]
If you are going to "fork it on github" and enhance it, please contribute back and submit your patches to: osmocom-sdr at lists.osmocom.org
A GNU Radio source block for OsmoSDR and rtlsdr is available. Please install a recent gnuradio (>= v3.5.3) in order to be able to use it.
Mailing List
We discuss both OsmoSDR as well as rtl-sdr on the following mailing list: osmocom-sdr@….
You can subscribe and/or unsubscribe via the following link: [url]http://lists.osmocom.org/mailman/listinfo/osmocom-sdr[/url]
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 buildcd buildcmake ../makesudo make installsudo ldconfig
In order to be able to use the dongle as a non-root user, you may install the appropriate udev rules file by calling cmake with -DINSTALL_UDEV_RULES=ON argument in the above build steps.cmake ../ -DINSTALL_UDEV_RULES=ON
Building with autotools:cd rtl-sdr/autoreconf -i./configuremakesudo make installsudo ldconfig
The built executables (rtl_sdr, rtl_tcp and rtl_test) can be found in rtl-sdr/src/.
In order to be able to use the dongle as a non-root user, you may install the appropriate udev rules file by callingsudo make install-udev-rules
pre-built Windows version  using libusbx 33ba1231a1b07425eaa83935f84b2e4b7f904f35 and pthreads-win32 cvs
Gnuradio Source
The gnuradio source requires the rtl-sdr package and a recent gnuradio (>= v3.5.3) to be installed.
The source supports direct device operation as well as a tcp client mode when using the rtl_tcp utility as a spectrum server.
Please note: prior pulling a new version from git and compiling it, please do a "make uninstall" first to properly remove the previous version.
Please note: you always should build & install the latest version of the dependencies (librtlsdr in this case) before trying to build the gr source.
Building with cmake:git clone git://git.osmocom.org/gr-osmosdrcd gr-osmosdr/mkdir buildcd build/cmake ../makesudo make installsudo ldconfig
NOTE: The source block (osmosdr/rtlsdr Source) will appear under 'Sources' category in GRC menu.
For initial tests we recommend the multimode receiver gnuradio companion flowgraph (see "Known Apps" table below).
You may find more detailed installation instructions in this recent tutorial.
Automated installation
Marcus D. Leech has kindly integrated the forementioned build steps into his gnuradio installation script at [url]http://www.sbrac.org/files/build-gnuradio[/url]. This is the most user-friendly option so far.
Usage
rtl_sdr
Example: To tune to 392.0 MHz, and set the sample-rate to 1.8 MS/s, use:./rtl_sdr /tmp/capture.bin -s 1.8e6 -f 392e6
to record samples to a file or to forward the data to a fifo.
If the device can't be opened, make sure you have the appropriate rights to access the device (install udev-rules from the repository, or run it as root).
rtl_tcp
Example:rtl_tcp -a 10.0.0.2 [-p listen port (default: 1234)]Found 1 device(s).Found Elonics E4000 tunerUsing Generic RTL2832U (e.g. hama nano)Tuned to 100000000 Hz.listening...Use the device argument 'rtl_tcp=10.0.0.2:1234' in OsmoSDR (gr-osmosdr) sourceto receive samples in GRC and control rtl_tcp parameters (frequency, gain, ...).
use the rtl_tcp=... device argument in gr-osmosdr source to receive the samples in GRC and control the rtl settings remotely.
This application has been successfully crosscompiled for ARM and MIPS devices and is providing IQ data in a networked ADS-B setup at a rate of 2.4MSps. The gr-osmosdr source is being used together with an optimized gr-air-modes version (see Known Apps below). You can find a Makefile for OpenWRT here.
A use case is described here.
rtl_test
To check the possible tuning range (may heavily vary by some MHz depending on device and temperature), callrtl_test -t
To check the maximum samplerate possible on your machine, type (change the rate down until no sample loss occurs):rtl_test -s 3.2e6
A samplerate of 2.4e6 is known to work even over tcp connections (see rtl_tcp above). A sample rate of 2.88e6 may work without lost samples but this may depend on your PC/Laptop's host interface.
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.
Please note: for realtime operation you may use fifos (mkfifo) to forward the iq data from the capture utility to the GRC flowgraph.
You may use any of the the following gnuradio sources (they are equivalent):
What has been successfully tested so far is the reception of Broadcast FM and air traffic AM radio, TETRA, GMR, GSM, ADS-B and POCSAG.
Tell us your success story with other wireless protocols in ##rtlsdr channel on freenode IRC network.
Known Apps
The following 3rd party applications and libraries are successfully using either librtlsdr directly or the corresponding gnuradio source (gr-osmosdr):
Using our lib? Tell us! Don't? Tell us why! :)
Multiple GMR-carriers can be seen in a spectrum view with the full 3.2 MHz bandwidth (at 3.2 MS/s).
Credits
rtl-sdr is developed by Steve Markgraf and Dimitri Stolnikov, with contributions by Kyle Keen, Hoernchen, Christian Vogel and Harald Welte.
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