RTL-SDR

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BATC Convention 2013 Slides


The key to the RTL-SDR is the Realtek 2832 chipset. The drivers for this give us access to the I2C control of the Frontend Tuner (eg. an Elonics E4000), allowing us to change the tuner frequency between 50-2200MHz (E4000), whilst sampling the output with the 3.2Msps ADC in the Realtek 2832. These samples are then fed down the USB into the PC, allowing demodulation with programs such as SDR# and HD-SDR.

This allows use to use the cheap TV dongle as a super-cheap sdr radio receiver, viewing upto 3.2MHz of bandwidth at once.

Discovery

Antti Palosaari discovered the ability to dump I/Q samples from the Realtek 2832 whilst developing the Linux driver for DVB-T.

I smell very cheap poor man's software radio here :) - Antti Palosaari

The guys at Osmocom jumped on it and very quickly had a set of Linux programs written to stream the samples.

Capabilities

People have managed to receive a very wide variety of signals, including:

  • Ham Radio signals (FM, SSB, CW, etc)
  • Data modes (by piping audio to FlDigi)
  • FM Broadcast (WFM)
  • High Altitude Balloon telemetry - See how I did it.
  • ADS-B (Airoplane transponders)
  • GPS

You can even listen into ~860MHz WFM radio mics, as I demonstrated at the BATC Convention. Much to my own surprise the audio was very clear!

Technical

The ADC in the RTL2832 chip runs at a 3.2Msps sampling rate. The sample depth is only 8 bits, providing a calculated ~47dB of dynamic range. The RTL2832 also provides I2C pass-through to allow us direct control of the E4000.

The E4000 tuner allows us to down-convert any frequency from 50-2200MHz down to baseband. The E4000 is capable of a 24MHz bandwidth. There is a tunable CMOS filter on the front-end, however this isn't the best filter in the world (see my BATC slides..).

Realtek RTL2832 DVB-T Demodulator:

Elonics E4000 Tuner:

Software

OsmoCOM (Open-Source MObile COMmunications) have spearheaded the development process with a program that controls the frequency and sample-rate of the Tuner IC, saving the resulting I+Q samples to a file, you can read more at their wiki page. GNUradio is then used to demodulate signals, with community-supported modules for many different types of signal.

For Windows:

  • HD-SDR
    • Intuitive interface.
  • SDR#
    • Recommended
    • Advanced Features
    • Active open-source development
    • Runs better than HDSDR on old/slow PCs or laptops.

For Linux:

  • GNU Radio is a very powerful Signal Processing framework.
  • gqrx is a multi-mode RX built on GNU Radio that supports the RTL-SDR in it's development branch.
  • QTRadio is a unique piece of SDR Software using a server-client architecture that can be used for ethernet-connected SDRs, potentially with remote web interfaces.

Compatible Models

The most up-to-date list I have seen can be found on the Osmocom RTL-SDR page.

As far as I know, any dongle with the RTL2832 Demodulator chip should now work. Frontend Tuners that work for sure are listed below:

  • E4000
  • FC0012
  • FC0013
  • FC2580

More Information

osmocomSDR - The guys who wrote the first drivers really kicked off the activity surrounding this dongle.

  • Supported Hardware List
  • List of Apps such as ADS-B rx, TETRA rx, etc.

reddit.com/r/RTLSDR - Frequent posts on new developments as well as links to many other resources.

##rtlsdr irc webchat - An irc chat channel with plenty of active discussion and expertise.

BATC Talk References