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SDRA2020 Online Conference Videos

The Software Defined Radio Academy is an organization that holds a conference within the yearly HAMRADIO fair in Friedrichshafen, Germany. This year due to the pandemic the conference was held online, and recently videos from the various talks have begun to slowly get uploaded to their YouTube channel.

The talks are typically very technical in nature, but if you're interested in cutting edge SDR research and applications then these are good talks to get caught up on. Currently there are seven videos that have been uploaded, but we are expecting that there are more to come since there are more talks listed in their programme. They appear to be uploading one video per day at the moment so get subscribed to their YouTube channel for the upcoming videos.

The currently uploaded talks include:

  • A Keynote interview with N1UL Dr. Ulrich Rohde
  • Laurence Barker G8NJJ: Using Xilinx Vivado for SDR Development
  • Edwin Richter DC9OE, Crt Valentincic S56GYK: Usage of higher order Nyquist Zones with Direct Sampling Devices
  • Prof. Dr. Michael Hartje DK5HH: Signalprocessing in the man made noise measurement system ENAMS
  • Bart Somers PE1RIK: Long term spectrum monitoring using GNUradio and Python

We are looking forward to the upcoming talks like the one by Dr. Bastian Bloessl DF1BBL that discusses the GNU Radio on Android implementation.

SDRA2020 - 03/04 - Laurence Barker: Using Xilinx Vivado for SDR Development

A Self-Executable version of TempestSDR is now Available

TempestSDR is an open source tool made by Martin Marinov which allows you to use any SDR that has a supporting ExtIO (such as RTL-SDR, Airspy, SDRplay, HackRF) to receive the unintentional signals radiated from a screen, and turn that signal back into a live image. This can let you view what is on a screen through a wall without using any physical cables.

We first posted a demonstration of TempestSDR back in 2017 when we were finally able to get it to compile. Compiling the software took a fair amount of work for those without experience, and even running it was a chore. However, getting it to work is worth it as you can do some really interesting demonstrations.

However these problems are over and recently Erwin Ried @eried has made a self-executable version of TempestSDR. This means that no compilation, java installs, mingw or extra dlls are required to get the program to work as now it's just an exe that you can run. You will still need the appropriate ExtIO dlls for your SDR. The video in his twitter post shows it working with a HackRF.

Decoding Radio Telemetry Heard on News Helicopter Video Footage with GNU Radio

Twitter user @d0tslash was watching news helicopter footage of the BLM protests on the 28th of May when he heard something that sounded like an RF telemetry feed in the background audio on the helicopter's video feed. Having seen this previous success at decoding similar helicopter telemetry, he contacted his friend proto17 who proceeded to reverse engineer and figure out how to decode the telemetry, in the end discovering that it was providing location data for the helicopter.

Over on GitHub proto17 has documented the complete process that he took in reverse engineering the telemetry. He first explored the audio in Baudline discovering that there was a 1200 Hz wide FSK signal. Next he used GNU Radio to further analyze the signal, discovering it's baud rate, resampling the signal and then using a GFSK block to demodulate the signal into 1's and 0's.

Finally he used some clever terminal tricks and a Python script to discover the bit pattern and convert the bits into ASCII characters which reveals the helicopter coordinates. The coordinates decoded indicate that the helicopter was indeed circling the protest area.

We looked into the news helicopters in use during the protests and found that Denver news stations all share one helicopter with registration N6UX. Plugging that into and looking at the helicopter ADS-B history on the 28th gives a good match to proto17's decoded data. 

News helicopter telemetry audio vs ADS-B history
News helicopter telemetry audio vs ADS-B history

YouTube GNU Radio Tutorials for Windows 10

Thank you to YouTuber M Khanfar for submitting news about his various Windows GNU Radio tutorials that he has been uploading to YouTube. So far he's uploaded tutorials on creating an FM Receiver, Air Band Receiver, AM/NFM Receiver, NFM Receiver with Squelch and Recorder and Spectrum Analyzer with GNU Radio on Windows 10. The tutorials are straight to the point and designed to be followed along with the video. The full list of videos can be found on his YouTube channel, and we have embedded one below.

Build NFM Reciver with Squelch and Recorder Activity GNU RADIO Win10

Radenso Theia: An SDR Based Police Radar Detector

Radenso is a company that sells radar detectors. These are used to help motorists avoid speeding fines from Police using radar speed detectors in their cruisers. Their latest upcoming product is called the "Radenso Theia" and is a software defined radio based solution.

In one of their latest YouTube videos they explain how SDR is used in the Theia, noting that the SDR ADC chip they are using is an AD9248. The use of an SDR allows them to more easily apply advanced digital signal processing algorithms to the radar detection task. In particular they note that they can now apply deep learning artificial intelligence filtering which helps to classify different radar gun FFT signatures and avoid false positives from other radar sources such as automatic doors.

While the Theia is designed to be a radar detector, they note that the device could also be used by hardware hackers as a standalone software defined radio. They have thought about this use case and have added a separate uFL connector that can be enabled by soldering a zero ohm connector, and this allows users to connect any antenna to it.

What is a software defined radio and why does it matter for Radenso Theia?

ARM Radio Code Ported to Free Toolchain

Several years ago in 2015 we posted about the "ARM Radio" by Alberto I2PHD which is a minimalist SDR implementation based on the ARM processor on the STM32F429 discovery board. It was implemented with nothing more than a basic low pass front end, a reconstruction filter for the audio output and some DSP code. With it's low cost ADC it's only able to tune from 8 kHz to 900 kHz, but this is enough to get broadcast AM signals and NDBs. While it may not have the best specs, it's an excellent learning project for SDR DSP and microcontroller programming, and the code is completely open source, although a non-free toolchain is required.

Recently Alberto Garlassi wrote in and wanted to share a re-implementation of the code on a free toolchain. He writes:

Unfortunately the author used the Keil MDK toolchain, this means that it is not possible to change the code without paying for a license. The free version is limited to 32K and this is not enough.

I ported it to the free (don't know how much, certainly GCC + Eclipse) System Workbench, now it is easy for everybody to start where I2PHD left.

I did this several years ago and in the meantime ST and ARM changed many things in their tools and libraries, but it still works ok, I checked.

The complete project is on Github, it should be a matter of downloading the IDE, the libraries and press the debug icon. I'm in touch with Alberto Di Bene I2PHD, he has no objections and told me he's happy about this.


TechMinds: Hands on with the Elektor SDR Arduino Shield Learning Kit

The Elektor SDR Hands-On-Kit is a low cost (€49.46) SDR learning package that makes use of the Elektor SDR Arduino shield which turns an Arduino microcontroller board into a 150 kHz to 30 MHz capable SDR receiver. It also comes with a book that teaches several basic SDR concepts.

Over on YouTube TechMinds has recently uploaded a video where he unboxes, constructs, and tests the kit using the free G8JCFSDR SDR software. TechMinds also notes that this SDR Shield can also transmit with 10mW of power, and that there is a tutorial included in the book that shows how to use the shield as a simple WSPR transmitter.

Elektor SDRShield - Hands-on Software Defined Radio Kit

Building a 1-Bit Oversampling SDR with not much more than a low cost FPGA

Thank you to Alberto Garlassi for submitting information about his super low parts home made FPGA software defined radio which is capable of medium wave and shortwave AM reception. What makes this design interesting is that is is created with nothing more than 3 resistors, 1 capacitor, and a low cost 30€ Lattice MachXO2 FPGA dev board.

The design makes use of the FPGA's LVDS buffer input to implement a direct sampling 1-bit ADC to which a wire antenna is directly connected to. This 1-bit resolution is increased by using an SDR trick that involves superimposing random RF noise onto the desired signal, and oversampling at 80 MHz then decimating down to a 6 kHz bandwidth. This results in an effective ADC resolution of 6-bits, from 1-bit hardware.

Synthesized on the FPGA is the ADC, Mixer, two CIC filters, an AM demodulator and a PWM circuit for audio output. The synthesis allows for medium wave and shortwave AM reception where the frequency can be tuned via PC control.

The FPGA Verilog synthesis files are available on the projects' GitHub page, and a more in depth explanation of the SDRs operation is available on its page. Alberto has also created a short demonstration video which is shown below.

FPGA + 3 R + 1 C = Medium and Long Wave SDR Receiver.