Vojtěch Bubník

Prague, Czech Republic
Joined May 2008
Vojtěch Bubník retweeted
The answer is an SDR that you already own! Let me introduce you to the BirriaSDR! A dual-band 40 Msps SDR (2.4 GHz/5 GHz) based on a mass-produced USB 3.0 Wi-Fi dongle that can export RAW I/Q for under 30 USD. Apologies, I finished the birria long ago... but only got around to writing this now. The idea was to use a chip as cheap as the RTL-SDR (<50 USD), with transport already built in (USB 3.0). Not something that costs four times as much or needs to be paired with an FPGA to export any real amount of data. Now, think for a bit: what kind of mass-produced device fits the bill? Yes, every single USB Wi-Fi dongle!!! It has been clear for a while that a lot of models have internal firmware that can be modified to export RAW I/Q data via their DMA engines. Most units can even run ASM payloads to modify the data. Historically, it would be a pain in the ass to reverse engineer the internal mechanisms of every single chipset in each Wi-Fi dongle (there are many!). But with AI, I can do that from my phone while eating birria at my local restaurant. Before leaving, I connected my MT7921A Wi-Fi dongle to my Raspberry Pi 5 and gave GPT-6 Astra the goal of getting it to export RAW I/Q over USB. Don’t be fooled: this wasn’t a “turn this into an SDR, make no mistakes” prompt. I had to give it leads on how to do this properly. By the way, this is the same chipset that the notorious ALFA AWUS036AXML has. At first, it created a burst exporter that could only record a short snapshot of RAW I/Q. This is an ancient feature that has been known for a long time and is even present in DD-WRT, but it was useless for our purposes. Then, after a couple of hours, it improved it to use the internal packetizing engine to create a stream of four consecutive complex samples per 16-byte block, with I and Q each occupying a 16-bit slot and retaining 14-bit precision. These blocks can be moved out of the device via the DMA engine. The RF front end can tune to both the 2.4 GHz and 5 GHz bands. The tested 40 MHz, 80 MHz, and 160 MHz sample rates work, but with a very prominent filter shape, as expected. The end result was a very capable SDR with dual-band 2.4 GHz/5 GHz reception, 14-bit I/Q resolution, and a nominal complex sample rate of 40 MSps over USB 3.0. Higher sample rates and wider bandwidths are still experimental. That said, I think this is a good proof of concept that needs to be further refined. Using a Wi-Fi dongle as an SDR solves the data interconnect problem and makes it easy to connect an external antenna with RP-SMA. I expect it won't take long for manufacturers to start mass-producing devices with the architecture I'm proposing, with a proper USB port, a tunable RF front end, and heat dissipation. I also want to make the point that you don't need to write a whole new SDR client every time you reverse engineer a Wi-Fi device to be used as an SDR. All you need is a small library that exports the I/Q. To prove this, the whole driver is a single Python script inside a CyberEther flowgraph file. Want to try it? First, buy an MT7921-based Wi-Fi dongle. They’re widely available and cost less than $30. Then, install CyberEther and download the flowgraph from the repository below. Connect the dongle and open the flowgraph in CyberEther to start streaming I/Q data, as shown in the video below. This will be available as a built-in block in CyberEther after some refinement. Download CyberEther: cyberether.org/ BirriaSDR Repo: github.com/luigifcruz/Birria… P.S. This is the same chipset many laptops come with!
Fellas, the answer to cheap SDRs is not in crippled chips that cannot export any real amount of data, or one that also costs hundreds of dollars.
25
63
4
421
34,545
The frontier LLMs are the best teaches I wished I had when I was a student. And my kids are wasting their time on Roblox and video feeds.
1
37
Vojtěch Bubník retweeted
Early duty here. VU2AAP and VU2LBW. 5060km over the ocean. That is as far as you can make it. The satellite is on both sides just over the horizon, that is why I had to go to the beach at 5am. – at Shimo la Tewa, Kenya
12
24
1
186
6,769
github.com/bubnikv/sdriak is now using an icon derived from "Sea free icons" designed by Ricardo Ruiz flaticon.com/free-icon/sea_1… via @flaticon . Thank you, Ricardo!
1
1
128
Rekonstruuji dům na kraji Prahy. Po zohlednění cen stavby si začínám myslet, že novostavby bytů vůbec nejsou drahé.
3
45
Když vidím jak vysychá naše krajina kvůli bezuzdnému pálení uhlíku a jinému znásilňování přírody, tak si říkám, kdy naše děti budou naskakovat na čluny.
Když se narodíš v rovníkové Africe, máš NULOVOU perspektivu. Proto posadíš dítě na vetchý člun a riskuješ všechno. My tady máme NEKONEČNOU perspektivu. Měli jsme jen kliku na rodiště. Nesuďte lidi bez šance, kdybyste se narodili tam, sedíte na tom člunu taky.
86
Apple’s App Store rules are hostile to open source: GPLv3 gives users the right to modify and redistribute software, while Apple requires non-transferable licence, DRM, and platform restrictions. A community project may need permission from every contributor just to be published
83
I don't get the discussion on which AI model to use for which task. If you you had to pick a subordinate into your team, would you willingly pick the less skilled one to have to constantly watch over him? For programming, I will always use the best model affordable.
1
67
FONMO: Fear Of Not Maxing Out (your AI token subscription)
2
73
Claude with Pro plan and Fable 5 allows a single SW engineer to take over a stalled open source project with a bunch of forks, unmerged pull requests, bug / crash reports and advance the original open source project one large step further, for fun.
2
1
150
It also takes away the joy of open source development done for credit and fame, as the robots are so efficient porting / stealing / reimplementing code or ideas. They evolved so far as to reverse enginner and re-implement binary code.
1
1
55
Programming with clunkers feels like the old joke about a policeman and swine on a space mission. Swine got a long list of instructions such as "Check engine, check fuel level...", while the policeman's instructions were short and simple: "Feed the swine and don't touch anything"
1
88
Scientists from IPP in cooperation with the Faculty of Nuclear and Physical Engineering of the Czech Technical University in Prague, with the support of the Technology Agency of the Czech Republic, have developed a unique soft X-ray diagnostic camera ipp.cas.cz/sd/novinky/hlavni…
3
75
wonderful dive into the history of vectors, divergence and curl youtube.com/watch?v=11QvV18J…
52
Sci-fi writers often describe the world before it arrives. We once relied on children to care for us in old age; now pensions do that. We once learned mainly from people face to face; now chatbots increasingly fill that role. In Isaac Asimov’s The Naked Sun,
1
80
human physical contact is seen as unpleasant, even repulsive. Are we moving toward that world? And if so, is it actually what we want?
1
57
We have an open position for a HAM radio super extra high frequency high power expert on Prague Tokamak COMPASS-U linkedin.com/feed/update/sha…
3
75
Vojtěch Bubník retweeted
This looks an awesome add on for the QMX+. Really appreciate Dan sharing it with everyone 👍
Here’s another 3D-printed box — this time for the QMX+. printables.com/model/1541880… The QMX+ is a great piece of hardware, by the way.
1
9
433
Vojtěch Bubník retweeted
The latest version features a 'Sync VFO' option, for better control QMX+
QMX+ and fork SDR++ by OK1IAK
3
15
3
110
7,491