What do Wi-Fi signals look like? MIT video reveals all with Coffee Can Radar

In late August, the internet got really excited about a trailer for a new iOS app showing what it would be like if we could physically see all the radio waves that are emitted from internet routers, mobile base stations and satellites.

The Architecture of Radio app by Dutch artist Richard Vijgen will only be released for iOS and Android in 2016, but it's important to bear in mind that it's only a visualisation of what wireless signals could look like.

Over at MIT, research scientists have been studying electromagnetics and radar for quite some time, and they can not only show you what your Wi-Fi signals look like, but even explain how you can see them for yourself.

"The late great Professor David Staelin from MIT once told me once that, 'if you make a new instrument and point it at nature you will learn something new'," Gregory L Charvat, co-founder of Hyperfine Research Inc and a visiting research scientist at the MIT Media Lab, wrote on Hackaday.

"Of all the things I've pointed Coffee Can Radars at, one of the most interesting thus far is the direct measurement and visualisation of 2.4 GHz radiation which is in use in our WiFi, cordless phones and many other consumer goods. There is no need to fool yourself with fake visualisations when you can do it for real."

What do 2.4 GHz wireless signals look like?

The Coffee Can Radar System is a DIY system devised by MIT that is used by everyone from government labs and the private sector, down to hackers, students, engineers and research institutions.

Charvat set up the radar system to directly image a 2.4 GHz microwave field emitted from its own transmitter, modifying the receiver antenna with a DSLR camera filming and red and green LEDs taped to the top of the can.

The results were red and green curved waves, and according to Charvat, this is what wireless radiation signals that come out of a wireless internet router look like.

"This is what 2.4 GHz wireless radiation looks like. From these measurements you can see the wave front curvature as it exits the transmitting cantenna. As we approach the distance 2d^2/lambda (where d = diameter of the transmitting cantenna) we can see the wave front turning into a plane wave. Also, you can see that the brightness of the LEDs drops as the inverse distance from the transmitter, just as one might expect," he said.

"Its well within your ability to measure and observe the nature of wireless propagation. See for yourself what wireless signals look like propagating through your lab and your home. If you're still not convinced that this is for you, take a look at [David Schneider's] Coffee Can Radar presentation, and my own video demonstrations of Doppler shift using the hardware."