TRX-Duo Is A Red Pitaya Clone For Software Defined Radio

October 9, 2022 by 33 Comments

If you’ve noticed the TRX-DUO software-defined radio transceiver, you might have wondered how it stacks up to other choices like Red Pitaya or HackRF.  [Tech Minds] obliges with a review of the Red device in the video below.

While this unit isn’t inexpensive, it also isn’t as expensive as some of its competitors. Sure, you can pick up an RTL-SDR dongle for a fraction of the price, but then you miss out on transmitting. The device is pretty powerful compared to a cheap software defined radio:

  • Frequency: 10 kHz to 60 MHz
  • CPU: Zynq SoC with a dual-core ARM Cortex A9
  • RAM: 512 MB
  • OS: Linux
  • Connectivity: Ethernet and USB connectivity (WiFi with a dongle)
  • ADC: 16-bit at 125 MS/s (2 channels)
  • DAC: 14-bit at 125 MS/s (2 channels)

The board boots off an SD card and there are several to choose from. The video shows two different images. One has a number of applications that run on the device and will also run on a Red Pitaya. The device shows a browser menu with various options and the result is quite impressive. Using the box as a WSPR beacon, it was heard fairly well given the low output power. It was, however, able to hear the world easily.

You can get a less capable Red Pitaya model for about $100 less than the going price. However, for something comparable, you will pay more for the Red Pitaya and — depending on capabilities — perhaps a lot more, although you do get more capability for the increased price.

You can do a lot more with a transmitting SDR — having both transmit and receive opens up many new projects. Of course, canned applications are great, but if you get one of these, you are going to want to try GNU Radio.

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Christian Hahn Starlink capture showing guard region.

Analyzing Starlink Satellite Downlink Communications With Software Defined Radio

November 26, 2021 by 23 Comments

Often, mere curiosity is sufficient to do something. This is also the case with people trying to analyze the communication setup and protocol which SpaceX is using with their Ku-band based Starlink satellites.  One of these fine folk is [Christian Hahn], who has recently posted some early findings to r/StarlinkEngineering over at Reddit. Some of the captured data seems to include the satellite ID system that ground-based user stations would presumably use to keep track of overhead Starlink satellites.

For the capturing itself, [Christian] is using a second-hand dish for capture and a DIY SDR using KC705 FPGA-based hardware – which may have begun its life as crypto mining hardware – along with the usual assortment of filters and other common components with this kind of capture. Even at this early time, some features of the Starlink protocol seem quite obvious, such as the division into channels and the use of guard periods. Nothing too earth-shattering, but as a fun SDR hobby it definitely checks all the boxes.

[Christian] has also announced that at some point he’ll set up a website and publish the findings and code that should make Starlink signal analysis easy for anyone with a readily available SDR receiver.

 

Doing WiFi With Software Defined Radio

January 16, 2021 by 12 Comments

Software defined radio lets RF hardware take on a broad spectrum of tasks, all based on how that hardware is utilized in code. The bladeRF 2.0 micro xA9 is one such device, packing a fat FPGA with plenty of room for signal processing chains on board. As a demonstration of its abilities, [Robert Ghilduta] set about writing a software-defined WiFi implementation for the platform.

The work is known as bladeRF-wiphy, as it implements the PHY, or physical layer of the WiFi connection, in the 7-layer OSI networking model. Modulation and demodulation of the WiFi signal is all handled onboard the Cyclone V FPGA, with the decoded 802.11 WiFI packets handed over to the Linux mac80211 module which handles the MAC level, or medium access control. Thanks to the capability baked into mac80211, the system can act as either an access point or an individual station depending on the task at hand.

[Robert] does a great job of explaining the why and the how of implementing WiFi modulation on an FPGA, as well as some basics of modem development in both software and hardware. It’s dense stuff, so for those new to the field of software defined radio, consider taking some classes to get yourself up to speed!

Virtual Software Defined Radio

August 7, 2020 by 5 Comments

Software defined radio or SDR has changed the radio landscape forever. But to use one you need to buy some kind of hardware right? Maybe not. As [Tech Minds] shows in a recent video there are plenty of SDRs publically available on the Internet. We know that isn’t news, but the video does cover several different methods of finding and using SDR receivers including many that run totally in the browser.

Of course, there are a lot of reasons you might want to borrow an alien radio receiver, even if you have your own hardware. Maybe you don’t have a great antenna or maybe you want to hear a signal — maybe even your own — from a different location.

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Software Defined Radio Academy Goes Virtual

July 8, 2020 by 4 Comments

They say every cloud has a silver lining. It’s hard to find a positive among all the bad news about the current global pandemic, but it has pushed more conferences and events to allow online participation either live or after the fact. A case in point: The Software Defined Radio Academy’s annual event is all on a YouTube channel so you can attend virtually.

Not all the videos are there yet, but the keynote along with some very technical talks about techniques ranging from FPGAs to spectrum monitoring and spectral correlation density — you can see that video, below. We presume you’ll eventually be able to watch all the presentations listed in the program.

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The Libre Space Foundation Reviews Software Defined Radios

April 8, 2020 by 7 Comments

If you want to go to the next level with software defined radio (SDR), there are a lot of choices. The RTL-SDR dongles are fine, but if you get serious you’ll probably want something else. How do you choose? Well, your friends at the European Space Agency Libre Space Foundation have published a paper comparing many common options. True, they are mostly looking at how the receivers work with CubeSats, but it is still a good comparison.

The devices they examine are:

  • RTS-SDR v3
  • Airspy Mini
  • SDRPlay RSPduo
  • LimeSDR Mini
  • BladeRF 2.0 Micro
  • Ettus USRP B210
  • Pluto SDR

They looked at several bands of interest, but not the HF bands — not surprising considering that some of the devices can’t even operate on HF. They did examine VHF, UHF, L band, S band, and C band performance. Some of the SDRs have transmit capabilities, and for those devices, they tested the transmit function as well as receive.

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Software Defined Radio Gets Physical Control

December 12, 2019 by 16 Comments

Software Defined Radio (SDR) is a great technology, but there’s something so satisfying about spinning a physical knob to cruise the airwaves. Wanting to restore that tactile experience, [Tysonpower] purchased a cheap USB volume knob and set out to get it working with his software. Unfortunately, getting it up and running took a lot more work than you’re probably expecting.

Programming the knob’s STM32

After verifying that the knob worked for volume control on his computer, [Tysonpower] decided to try and pull the firmware from the device’s STM32 microcontroller. Unfortunately, this is where things got tricky. It turned out the chip had Code Protection enabled, so when it was wired up to a programmer and put into DFU mode, the firmware got wiped. Oops.

That left [Tysonpower] with no choice but to write a new firmware from scratch, which naturally required reverse engineering the device’s hardware. Step one was reading up on STM32 development and getting the toolchain working, which paved the way to getting the knob’s LED to blink. A couple more hours worth of work and some multimeter poking later, and he was able to read the knob’s movement. He describes getting USB HID working as a nightmare due to lack of documentation, but eventually he got that sorted out as well.

The end result is a firmware allows the volume knob to mimic a mouse scroll wheel, which can be used for tuning in many SDR packages. But we think the real success story is the experience [Tysonpower] gained with reverse engineering and working with the STM32 platform. After all, sometimes the journey is just as important as the end result. Continue reading “Software Defined Radio Gets Physical Control” →