Seeing 2.4 GHz Radio Waves

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Posted by samzenpus on Wednesday September 9, 2015 @12:15PM from the take-a-look dept.

szczys writes: There was this art piece that circled the internet a few weeks ago which used a tablet to visualize WiFi and other signals and it was complete fake. It was cool, and it approximated where radio waves emanated from, but it wasn't actually measuring them for display. Greg Charvat has built his career on Radar and other RF design. Seeing that demo he realized he could show you what actual microwaves look like. He used a radar that he built himself from coffee cans. By altering the circuit just a bit he is able to move the receiver around the room and illuminate different LEDs based on the signal traits. A long exposure photograph captures this and lets you see the radio waves. It's like a charcoal rubbing but for electromagnetic waves.

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I'm coming mother by pr0t0 · 2015-09-09 12:31 · Score: 2

I didn't know Norman from Bates Motel was into radar and em waves. Cool.

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1. Re:I'm coming mother by Anonymous Coward · 2015-09-09 22:37 · Score: 0
  
  oh good, that means dad, I mean mom, finished her surgery!
Can't wait for conspiracy theorists by Anonymous Coward · 2015-09-09 12:33 · Score: 0

Can't wait for conspiracy theorists, crazy people under attack by "energy weapons" and those allergic to every kind of radiation to catch wind of this. These guys are going to become famous among the completely wrong crowd.
1. Re: Can't wait for conspiracy theorists by myrdos2 · 2015-09-09 14:13 · Score: 3, Interesting
  
  I've often wanted something that could produce an image from EM emissions, in the same way that our eyes create an image from light. It would make finding EM interference and shielding problems a breeze. But when I Google it all I can find is ghost detection equipment and cameras that are supposed to take a picture of your aura and other nonsense. So there's at least two kinds of crazy at play here.
2. Re: Can't wait for conspiracy theorists by Anonymous Coward · 2015-09-09 14:31 · Score: 0
  
  It would make finding EM interference and shielding problems a breeze.
  Not really, at least not so much in some place that isn't a large open office or outdoors, and involves a rather large detector. Optics gets messier when the size of objects interacting with are closer to the wavelength. A directional antenna would be easier, smaller, and get you quite a bit of info for a lot less hassle than imaging optics.
3. Re: Can't wait for conspiracy theorists by elgatozorbas · 2015-09-09 23:50 · Score: 1
  
  I've often wanted something that could produce an image from EM emissions, in the same way that our eyes create an image from light. One way to do so is to capture the electromagnetic field in an matrix in an area (say 2x2m^2), called an aperture, and converting these captured signals to visualise the sources of the signals, more or less like a scanning beamformer. In practice it would be costly to capture hundreds of signals at once. Assuming the sources are stationary, you can also scan the aperture horizontally and vertically.
4. Re: Can't wait for conspiracy theorists by Anonymous Coward · 2015-09-10 01:45 · Score: 0
  
  I've often wanted something that could produce an image from EM emissions, in the same way that our eyes create an image from light.
  Look at https://en.wikipedia.org/wiki/Synthetic_aperture_radar because that is exactly what it does.
5. Re:Can't wait for conspiracy theorists by Anonymous Coward · 2015-09-10 01:48 · Score: 0
  
  Clearly. Those Russians exploding a boom box just by pointing microwave radiation at it is obviously faked because everyone knows microwaves are completely harmless. And that Jesus loves them.
6. Re:Can't wait for conspiracy theorists by Anonymous Coward · 2015-09-10 05:13 · Score: 0
  
  You should see what a firehose does to a boombox, then we can ban dihydrogen monoxide.
7. Re:Can't wait for conspiracy theorists by Anonymous Coward · 2015-09-10 11:52 · Score: 0
  
  dihydrogen monoxide
8. Re: Can't wait for conspiracy theorists by Agripa · 2015-09-11 05:35 · Score: 1
  
  The output from an actual WiFi transmitter would be more interesting since almost all of them use mediocre antennas with weird radiation patterns and group delay instead of close to ideal horn antennas.
OK, that's pretty damn nifty. by Anonymous Coward · 2015-09-09 12:34 · Score: 0

When can I get a $1.99 widget to find wifi deadzones in my house?
1. Re: OK, that's pretty damn nifty. by JohnNemesh · 2015-09-09 13:10 · Score: 2
  
  There are several wifi sniffing apps you can download for your smartphone that will accomplish.
The Stars My Destination by Anonymous Coward · 2015-09-09 12:43 · Score: 0

Gully could see radar... ah wonderful book.
i see Dead People by turkeydance · 2015-09-09 12:45 · Score: 1

they look like WiFi
I don't get it by Anonymous Coward · 2015-09-09 12:49 · Score: 4, Funny

What does this have to do with the new iPad Pro? This site is supposed to be news for nerds...not this boring gobbledygook!!
1. Re:I don't get it by david_bonn · 2015-09-09 13:02 · Score: 5, Insightful
  
  I actually think this is one of the most awesome things I have seen on slashdot in a long time.
  Someone did a real science experiment with fifty bucks worth of parts and two coffee cans.
2. Re:I don't get it by Anonymous Coward · 2015-09-09 13:08 · Score: 0
  
  Looks to me like OP was being sarcastic about the lack of actual technical stuff like this on Slashdot since Dice took over. And yes, agree this is very cool.
3. Re:I don't get it by fisted · 2015-09-09 13:53 · Score: 2
  
  Highest-modded whoosh i've seen on slashdot in a long time.
  
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4. Re:I don't get it by Anonymous Coward · 2015-09-10 04:06 · Score: 0
  
  Someone did a real science experiment with fifty bucks worth of parts and two coffee cans.
  Not sure why that is impressive. Not all science experiments have to be complex and expensive.
  Analemmatic sundials can be made simply by putting a stick in the mud. You can learn a whole lot about the motion of the Earth from it.
  Benjamin Franklin experimented with electricity using a kite and a key
  Hell, did you ever try experimenting with two cans and a string? Boiling kettles of water at different altitudes? Experimenting with parallax using only your eyes and one finger? Magnifying things through a drop of water?
Cool, but it's been done better by Anonymous Coward · 2015-09-09 13:22 · Score: 5, Interesting

7 months ago on Hackaday's own site:
http://hackaday.com/2015/02/17/mapping-wifi-signals-in-3-dimensions/
1. Re:Cool, but it's been done better by Anonymous Coward · 2015-09-09 16:29 · Score: 0
  
  Cool! A way to visualize fading with LEDs in addition to the other guys way of viewing the wavefront. Good stuff. Just in case anybody is interested, you can also use EM Simulators like FDTD or FEM to do these things without building hardware. It can be very enlightening to see how electromagnetic waves propagate through various materials. It is also very useful for designing things like microstrip planar filters (low-pass, bandpass, etc).
not really what microwave would look like. by Wycliffe · 2015-09-09 13:31 · Score: 3, Interesting

Microwave and light wave are on the same spectrum so if you could see in microwave then it would just illuminate objects just like
regular light or ultraviolet light but with the awesome effect that it would actually penetrate some objects. A camera that shifted
microwave down to visible light would be really cool similar to how a ultraviolet camera lets you see ultraviolet light.
1. Re:not really what microwave would look like. by Tony+Isaac · 2015-09-09 16:57 · Score: 4, Insightful
  
  A big difference from regular light would be blurriness. WiFi, at 2.5 GHz, has a wavelength of about 5 inches. This would lead to an extremely foggy, blurry image of everything around you.
2. Re:not really what microwave would look like. by dotancohen · 2015-09-09 20:04 · Score: 2
  
  A big difference from regular light would be blurriness. WiFi, at 2.5 GHz, has a wavelength of about 5 inches. This would lead to an extremely foggy, blurry image of everything around you.
  This is actually terribly insightful. I just googled "c / 2.4 Ghz" and Google came back with "12.4913524 centimeters".
  
  --
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3. Re:not really what microwave would look like. by Anonymous Coward · 2015-09-09 20:48 · Score: 2, Interesting
  
  Fun fact, humans can actually see UV light pretty well if you remove our lens that obscures it.
  Many people who have had one of their lenses removed have noticed it, and many have reproduced what it approximately looks like and how it affects the world they see around them.
  Their sensitivity to bluer frequencies is still the same though, no increase in fidelity, just opens up more of the spectrum to see.
  For the most part, it increased how vibrant everything looked, a whitish blue-violet filter being applied to everything. An artist even painted in it, Monet I think.
  Of course, this does mean that their eyes are being exposed to damaging UV, which is A Bad Thing.
  They'd probably be recommended to wear sunglasses wherever possible now, outside of new surgeries which I hope have UV-blocking coatings if requested.
4. Re:not really what microwave would look like. by umafuckit · 2015-09-09 23:31 · Score: 1
  
  Microwave and light wave are on the same spectrum so if you could see in microwave then it would just illuminate objects just like regular light or ultraviolet light but with the awesome effect that it would actually penetrate some objects. A camera that shifted microwave down to visible light would be really cool similar to how a ultraviolet camera lets you see ultraviolet light.
  Maybe a "pinhole" microwave camera is possible?
  
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5. Re:not really what microwave would look like. by Anonymous Coward · 2015-09-09 23:37 · Score: 0
  
  It would need to be pretty big if you didn't want an image of just pinhole diffraction.
6. Re:not really what microwave would look like. by Anonymous Coward · 2015-09-10 01:12 · Score: 0
  
  https://en.wikipedia.org/wiki/Pinhole_camera
  Optimal pinhole size can be guessed using: d = (2fL)^0.5
  The focal length (f) can be selected, so say we want it to be a manageable size with a focal length of 1m, the pinhole should be: d = (2 x 1 x 0.125)^0.5 = 0.5m...pretty big hole.
  If we go to a 2m focal length: d = 0.7m
7. Re:not really what microwave would look like. by Anonymous Coward · 2015-09-10 04:36 · Score: 0
  
  Right. The thing is light is over 150,000 times shorter wavelength than WiFi. What people are trying to do here is visualize the field created by microwaves. This is very different than imaging what they reflected off like we do with light. The RF field created by light isn't normally coherent, while microwaves are. If you illuminated a room with laser light, then you might get a similar field, but the features of the field would be microscopic.
8. Re:not really what microwave would look like. by Anonymous Coward · 2015-09-10 05:28 · Score: 0
  
  Eh, that puts you into the realm where diffraction makes things blurrier, and you're better off with d=2sqrt(f \lambda) where get slight focusing from diffraction. Either way, your resolution at the end of the day is going to be about the scale of your pinhole radius, so you're going to end up barely resolving anything with the 2m meter setup.
9. Re:not really what microwave would look like. by Anonymous Coward · 2015-09-10 06:40 · Score: 0
  
  regular visible light passes through some objects as well, the most common of them is glass, though some plastics and aluminums (according to star trek) are also transparent (which of course is from the latin literally translated means "your dad has breasts now.")
  Some objects are more receptive to passing RF frequencies than others, just like visible light.
Re:the movie Lucy by Anonymous Coward · 2015-09-09 13:44 · Score: 0

Scarlett Johanssen
Ah yes, Obama's side squeeze... Not bad, eh? Better lookin' than Monica...
Is this guy serious? by AndyKron · 2015-09-09 14:03 · Score: 0

The video looks like is was made by rubbing charcoal on the monitor. Is this guy serious?
1. Re:Is this guy serious? by Anonymous Coward · 2015-09-09 20:49 · Score: 0
  
  The video looks like is was made by rubbing charcoal on the monitor. Is this guy serious?
  Are you?
not waves by Skapare · 2015-09-09 20:16 · Score: 1

that didn't look like waves to me ... particles?

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1. Re:not waves by Anonymous Coward · 2015-09-09 22:57 · Score: 0
  
  Back in the day we used to call them "quantum mechanical objects".
why standing? by Anonymous Coward · 2015-09-10 01:48 · Score: 0

Why does it appear that the wave is a standing wave? Shouldn't it be propagating smoothly like a normal wave?
1. Re:why standing? by Zeroko · 2015-09-10 05:54 · Score: 1
  
  As long as the source & reflective/absorbing objects stay fixed, the areas where the waves interfere constructively & destructively should remain fairly stable (which is in turn why microwave ovens have turntables), & the wave itself is waving at far too high a frequency to see.
1.6 GHz by Anonymous Coward · 2015-09-10 04:13 · Score: 0

Hmm, I get it. So by that logic, I can claim that my cock is 1.6 GHz.