What is software defined radio?

Software defined radio (SDR) allows you to use one single but completely programmable transceiver device for modulating and demodulating many different types of RF signals. A wideband device such as the FreeSRP can thus be programmed and used to interact with wireless transmissions like FM radio, TV, GSM, 802.11 or GNSS.

The FreeSRP is compatible with the GNURadio ecosystem, and works with many existing GNURadio-based programs, such as gqrx.

For a detailed look into the project's development, check out these blog posts:

Building an SDR from scratch  GNURadio: FreeSRP
FreeSRP R2

Covers 70 MHz to 6 GHz

Based on the Analog Devices AD9364 agile transceiver, the FreeSRP covers a wide frequency range and has up to 56 MHz of bandwith.

Powerful signal processing

The onboard Xilinx Artix 7 FPGA provides powerful digital signal processing capabilities and makes the FreeSRP a great prototyping platform.

USB 3.0 connection

The USB 3.0 connection makes real-time streaming of all received data to a PC possible, so GNU Radio or other signal processing toolkits can be used.

The project

The aim is to develop a powerful but low cost (300-400 USD price range) SDR platform. Currently, the project has seen its third hardware revision and is able to receive and transmit. Software is still under development, but a small C++ library using libusb already allows using the SDR from within other applications. I have started extending the gr-osmosdr GNURadio block to work with the FreeSRP.

The hardware and software will be released under an open source license when the design is fully working with all major issues fixed.

Thanks for supporting this project to:

LeitOn PCBsPrototype PCBs manufactured in Germany
Photocad StencilsLaser cut steel SMD stencils

Gude Stiftung
Deutsche Schule Barcelona

Further information


The prototype hardware works, and I'm currently finishing the software.

The production hardware will require only a very minor revision of the current prototype.

If you're interested in this project or can help bring this into production, please contact me!

Progress & status


  • Receiver, even at full bandwidth and over the full spectrum
  • Receiving part of the driver and receiver gr-osmosdr integration (in a private fork of gr-osmosdr)
  • Transmitting part of the driver (full duplex works as well, but with bandwidth reduced to ~25 MSps)
  • Compatibility with gqrx and all other GNURadio-based software that uses gr-osmosdr

In progress

  • Improving full duplex bandwidth
  • Fixing much lower than expected output power (hardware issues)

To do

  • Proper characterization of receiver/transmitter in a controlled environment

Source files

Download the full, open-source schematics, PCB layout and software.

GNURadio software and library available now, hardware and firmware coming soon.

Project on GitHub


FreeSRP Alpha

I am planning on doing a small run of 10-20 boards for the next revision of the FreeSRP hardware, hopefully available by January 2017. The expected price tag is 350 USD. You can sign up for updates by entering your email address here or contact me if you want one!