Tagged: TRX-DUO

Exploring the Art and Science of Spectral Painting with SDR

Thank you to Paul Maine, who wrote in and wanted to share some experiments he and Gary Schafer have been doing with spectral painting. Spectral painting is the art of drawing pictures directly on the spectrum waterfall, which a software-defined radio makes visible. Paul has written the post below:

What happens when radio technology meets digital artwork? The result is something fascinating called Spectral Painting—the ability to create images that appear inside the radio frequency spectrum.

Gary Schafer (@signalgalaxiesunlimited) and Paul “The SDR Guy” Maine (@paulmaine6433) have teamed up to explore this unique combination of software-defined radio, signal processing, and creativity. Together, they have created companion videos on Spectral Painting and released them at the same time, each approaching the topic from a different perspective. For the best experience, it is recommended to watch Gary’s video first, followed by Paul’s practical demonstration.

Gary begins the journey by diving into the theory behind Spectral Painting. Using GNU Radio flowgraphs and GNU Octave scripts, he explains how images can be transformed into signals and displayed within the frequency spectrum.

Paul then takes Gary’s GNU Radio flowgraph and GNU Octave scripts from theory into practice. Using multiple SDR platforms, he demonstrates how to transmit spectral images using both the HackRF and TRX-DUO SDRs. He then completes the process by receiving and displaying the images using several different SDR receivers, including the RTL-SDR V3, RTL-SDR V4, and Airspy HF+.

Together, these videos provide a complete journey—from understanding the science behind Spectral Painting to seeing it come alive on real SDR hardware.

Below is an example screen capture of Spectral Painting in action.

Spectral Painting Example
Spectral Painting Example

Start with Gary’s video to learn the concepts and signal processing techniques:

Creating Spectral Paintings using Gnu Radio Companion (and other open source tools)

Then watch Paul’s video to see Spectral Painting transmitted and received using real SDR equipment:

E30 Spectral Painting

TechMinds: A Look at the TRX DUO Red Pitaya Clone

The Red Pitaya is advertised as an open source electronics laboratory instrument, but as it's essentially a software defined radio with built in computing hardware, custom software can be installed allowing it to function as an HPSDR compatible RX/TX capable SDR.

The TRX DUO is a "Red Pitaya compatible" device that comes at a price significantly lower that the Red Pitaya. Its specifications are comparable to the Red Pitaya SDRlab 122-16 which in the official website goes for 625,00€ / US$622. In comparison the TRX DUO can be found on marketplace sites like Aliexpress for almost half price at US$320.

The TRX-DUO has a tuning range from 10 kHz to 60 MHz, 16-bit ADC and 2-RX and 2-TX channels. It also has a built in ARM Cortex A9 processor, and Xilinx Zynq 7010 FPGA SOC. The built in computing means that decoding software can be run directly on the device if desired.

Matt from the TechMinds YouTube channel has recently tested and reviewed the TRX-DUO in his latest video. His video goes over the specifications, software installation, and a demonstration of it receiving HF signals. He goes on to show how it can be used as an 8-band WSPR monitor, and how you can enable WiFi on it and download various Red Pitaya apps.

Matt also notes that the transmit power of the TRX-DUO is very small at 2.5 mW, but of course an external amplifier can be used to boost this.  However, it is important to note that band filtering would be required for the emissions to be safe to transmit.

TRX DUO APPLICATION BASED HF SDR TRANSCEIVER (RED PIYATA)