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LF: Fwd: rtl-sdr – OsmoSDR

To: [email protected]
Subject: LF: Fwd: rtl-sdr – OsmoSDR
From: John Rabson <[email protected]>
Date: Sun, 1 Apr 2012 17:18:52 +0200
References: <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Could this be any use at LF?

John F5VLF

Begin forwarded message:


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).

Supported Hardware

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 Download)
  • 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:

top view of the ezcap PCB
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://

It can also be browsed on


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).

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:

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.

What has been successfully tested so far is the reception of  TETRA,  GMR and  GSM. 

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


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