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Posted by codetheweb 1/23/2026

I built a light that reacts to radio waves [video](www.youtube.com)
https://rootkid.me/works/spectrum-slit
425 points | 97 comments
tzvc 1/23/2026||
Creator here, thanks for posting. And feel free to ask me anything!
thinkingtoilet 1/23/2026||
Very cool project. Thank you for sharing. It's rare where something so technical can have such an artistic manifestation. Well done.
djhworld 1/23/2026|||
Awesome project & video, thanks for making it

Where did you learn all the PCB design stuff to make your circuit boards that controlled the filaments?

xtoilette 1/23/2026|||
I love your works, what kind of background do you have?
tzvc 1/23/2026||
CS background, but I've always been a "bricoleur" on the side
dangoodmanUT 1/23/2026|||
You’re very good, I’m jealous of your work
jenowigner 1/23/2026|||
amazing project ! well done ! inspiring to see it this morning the youtube algo recommended it for me. I was thinking what would be a budget way of creating this ? maybe a $20 SDR instead of the hack rf , seems to be a waste of the hack rf to use it as a lamp :)) I think the way you did must have cost you over $1k. Thanks for the inspiration !
tzvc 1/23/2026|||
Hackrf is defo overkill for this. I got it cause my initial plan was to cover the whole spectrum

You could probably do it with a cheaper SDR, but it would be slower

Total budget for this is around $1k

orbsa 1/23/2026||||
IIRC, a regular SDR dongle will not be able to process the full bandwidth of GHZ range.
pixl97 1/23/2026||
I do think most people implementing something like this, especially in the exact way this one was implemented would really just be interested in the Wi-Fi ranges.

When I was doing wireless stuff we'd show customers the output of RF analysers to show that even with their wifi turned off their spectrum was packed full of noise.

Having a large viceral display of this would quickly enlighten them.

direwolf20 1/23/2026||||
HackRF isn't a good SDR by any metric except for the date it came out.
ipdashc 1/23/2026||
What would a better alternative be?
1e1a 1/23/2026|||
The $5 nrf52840 should be sufficient, it can scan 114 channels (from 2400-2514 MHz) several times per second, measuring the approximate RSSI.
bethekidyouwant 1/23/2026||
You could not use that as an SDR to make a waterfall which is required in this case
proee 1/23/2026|||
How much did that sheet metal frame cost you from PCBWay? Thanks for sharing.
tzvc 1/23/2026||
Around $200 delivered to france
cheschire 1/23/2026|||
Do you have a list you would be willing to share of trusted manufacturers & suppliers that you reference for different products or materials?
tzvc 1/23/2026|||
I used JLCPCB for the pcb cause they integrate well with the pcb design software i use (kicad or easypcb)

And I used pcbway for the sheet metal fabrication

Honestly they are both great and similarly priced

flexagoon 1/23/2026|||
At least in the last video it seems like he used both PCBWay and JLCPCB for manufacturing
cheschire 1/23/2026||
Yep! The choice of JLCPCB after having used PCBWay is what inspired the question.
flexagoon 1/23/2026||
Love your channel! Do you have any plans to eventually open source your projects? (Both in terms of hardware and software)
tzvc 1/23/2026|||
To be honest, all of the hardware and software is really poorly documented. But I guess i coudl still publish it as is
flexagoon 1/23/2026||
Yes, would be still great! I'm sure a lot of people would have fun playing around with it even without the documentation
mechazawa 1/23/2026|||
I'm personally especially interested in 'Latent Reflection'. I've tried to make something similar never got to a point where I was happy with the output the AI model gave me.
tzvc 1/23/2026||
Lots of tuning to get the model to not immediatly spiral into nonsense. But small models are getting better by the minute, maybe i'll revisit it with a better model and share all the code
TrackerFF 1/23/2026||
Cool project. I was going to say, the end resulting light should be a pretty saturated spectrum, given that many RF sources just keep pumping out waves, and the those waves propagating and bouncing around.

I think one fun application would be a light which represents your wi-fi strength around the house. Obviously in a smaller apartment that's really not a problem, but in larger houses it would be fun to see.

Another application would be to find hidden RF sources / leaks. I have a home recording studio, and for the life I could not find some RF source that kept adding noise / interference. I could roughly detect the frequency of the noise, but not its origin. I guess if I had a couple of RF sensors I could try to triangulate my way to it.

tzvc 1/23/2026|
Yes, in the parisian apt. where I filmed the RF landscape is wild

But tuning in to the specific wifi channel you router use you could even use this piece as a signal strenght plotter!

pixl97 1/23/2026|||
>use this piece as a signal strenght plotter

Seems like it wouldn't be hard to filter this for something like the 2.4 or 5GHz range then put a different color filament at the demarcation point for each of the channels.

ricardonunez 1/23/2026|||
That’s what I was thinking, the project should yield a few different useful tools. That was a great video.
kh_hk 1/23/2026||
Cool project. Here's some OT: where do people learn to make these videos? Fast paced but calm narration with chill music and sped up action mixed with regular speed. It's a matter of consuming a lot of this content until the form clicks, or you need to go to influ-school?
tzvc 1/23/2026||
No influencer school, no video experience whatsoever actually

I watched TONs of youtube videos growing up and I guess I took inspiration from what I liked in each: fast pace, always shows what you are talking about on screen (no talking head), include tiny projects in the main one, explain the science, use an intro to captivate and an outro to nail the point, use music to drive rythme

I film and record audio with just my phone

kh_hk 1/23/2026|||
Thanks! That kind of makes sense. It's always interesting to me when I see patterns that make videos work well, and I usually have a lot of questions about the production.

Another question that I hope is not disrespectful: does PCBWay and JLCPCB pay for brand placement during the video or was it just a tribute from your side?

dangoodmanUT 1/23/2026|||
Man iphones have come a long way
pixl97 1/23/2026||
My wife has worked in marketing for years and setting up photo shoots/video shoots has changed massively. A huge amount of the video and pictures that don't require a specialized lense are just done with feature phones these days.
xtiansimon 1/23/2026||
Yo. You have to make videos. Then, seeing videos that you like, you secretly try to “steal” those ideas you articulated.

Just don’t tell anybody you’re a copy-cat.

wpietri 1/23/2026||
"Good artists borrow. Great artists steal." -- me
lucid-dev 1/23/2026||
FANTASTIC!!

I was just thinking about this the other day, and wondering about directionality...

For example, if you had a camera facing a space, and the receiving antenna was within that space... and you were able to (somehow?) from the antennas perspective, see the "direction" the frequency was coming from..

And then map the different specific frequencies within the desired bandwidth to colors... and of course intensity map like you have in the slit device..

And then "look through the camera"... you would see a live three dimensional overlay of all signals within range (colored!) "interacting" with the antenna... but kind of more the "looking through the camera" sort of view, like you could "see" how those waves were interacting..

And then wouldn't it be interesting to put a tin-foil hat to one side of the attennas.. and see how the waves change in real time... etc.!!!

(I guess it takes three antennas, to triangulate the field? Maybe all three can still be mounted on a single device in close proximity?)

mzhaase 1/23/2026||
Yes it has been done: https://youtu.be/sXwDrcd1t-E?si=V75bEPMT8qGbo1wG
janez2 1/23/2026||||
your link has the "si=" tracking parameter in it
diimdeep 1/23/2026||||
The title is: This ESP32 Antenna Array Can See WiFi

And every time I see something like this I like to remind to myself and imagine what spherical grid of Starlink satellites linked by laser is really capable of instead of mere internet as it is advertised.

phrotoma 1/23/2026|||
See also: https://youtu.be/o6WHhqDHSQ4
johanvts 1/23/2026|||
If you buy three (or more) Phillips Hue bulps you can have them respond to motion detected by things moving around and disturbing the radio waves they use to communicate. So they must have pretty much the kind of map you want, but I dont know how easy it is to export it.
amelius 1/23/2026|||
This is sort of that idea with sound:

https://www.youtube.com/watch?v=jL2JK0uJEbM

ErroneousBosh 1/23/2026||
> and you were able to (somehow?) from the antennas perspective, see the "direction" the frequency was coming from..

You can kind of do that quite easily at low frequencies, by measuring the phase of signals coming in from a pair of aerials. If you put two aerials a quarter of a wavelength apart and switch between them very quickly at audio rate, then you'll get a tone when there's a difference in phase. If there's no tone the two signals are exactly in phase - the two aerials are exactly the same distance from the transmitter.

If you look on some police cars you'll see a group of four aerials about 15cm apart stuck to the roof which used to be used for "Lojack" style trackers.

There are a whole bunch of circuit diagrams floating around for doing this kind of thing, with the simplest being Ye Olde 555 timer and a couple of PIN diodes!

mrtksn 1/23/2026||
It’s beautiful. I think I’ve seen something similar in a Ukraine war video where they use a device that lights up on specific frequencies that drones use.
cush 1/23/2026||
His other projects are so interesting. I love this one

https://rootkid.me/works/exhibit-a

CrzyLngPwd 1/23/2026||
Oh, that is fantastic.

What would really finish it for me, though, is if, when the button is released, the device shows a website, with URL visible, with a photo of the criminal, with added facial recognition and lookup of social media to find their identity.

What fun!

simgt 1/23/2026|||
The narration is very nice. Any idea of what the data could be? He mentions that it's legal for him to store but illegal to sell abroad and ranges from "bad to very bad".
abrookewood 1/23/2026||
It's in teh description: "launching a fully functional darknet marketplace (http://spectretjag3wni6fzt445qwgokqlxnfz7fxkicj5efxjywlinibm...) that offers a trove of illegal data for sale across borders"
simgt 1/23/2026||
> offers a trove of illegal data for sale

I'm precisely asking for speculation on what this data could be, which is the goal of the artist as stated in his video

pixl97 1/23/2026||
Stolen PII/identities/passwords are one of the most common you'll find.
MPSimmons 1/23/2026||
I don't need that, I already have a Twitter account
asgerhb 1/23/2026||
Sawing the first shot, I thought the LED candle on the coffee table was the device. That would have also been cool, having flickering affected not by wind, as with real candles, but by radio waves.
milleramp 1/23/2026||
Very cool, was there a conversion or look up table to convert db to gamma for more accurate human visualization?
tzvc 1/23/2026|
I'm not sure what you mean
milleramp 1/23/2026||
The db scale is logarithmic but doesn't match how our eyes sense light. So small changes in db may result in large visible light changes, or vise versa. Have you ever looked at a raw image, it doesn't look correct untill a gamma is applied, even though roughly the same information exists in both raw and gamma images. This is a similar concept. To do do this: db > linear > gamma This can be precomputed into a lookup table with the number of entries being the number of current steps, 8-bit 256 entries.
01100011 1/23/2026|
A much simpler and less cool project would be to convert a slice of the RF spectrum into an RGB value with lowest frequencies mapped to red, highest to blue, and the resulting color being how we would perceive the mix.
saaaaaam 1/23/2026|
That would still be cool - but what I really like about this is that it says something quite interesting about human existence, how we live, and in particular how we live in cities when we are in proximity to each other.
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