How do radio and Wi-Fi signals actually work?


I don’t think I was ever taught this but thinking about it it seems like suck a futuristic concept and I wanna know how they both work. Like, how do these things send invisible, intangible signals?

In: 65

The “invisible signals” are electromagnetic radiation, same as visible light. It’s just not a wavelength your eyes can see. That’s the same category as microwaves, X-rays, UV light, infrared, etc. – it’s all just colours of light your eyes can’t see.

For radio and wifi, the ELI5 is that the data being sent is broken up into 1’s and 0’s (for wifi) or a wave representing the sound (for radio) and emitted as a pulsed/ flashing signal that travels out from the source in all directions, just like any other “light” does. Think of it like using a lantern to send Morse code as dots and dashes using long and short flashes of light. Radio broadcast are doing the same thing, beaming out pulses of light (a colour of light we call “radio”) across the landscape from their transmitter. Anyone with the right set of “eyes” for this colour – an antenna, can pick up this flashing light and decode the message back into a sound wave or digital data or whatever.

Just to be clear, wifi uses radio.

All those signals are photons that fly around and behave both like particles and like waves. As particles, they bounce around and have a linear component to them, but as a wave they have a frequency in which, once emitted, they oscillate in as they travel.
There is a spectrum of those frequencies that we call the electromagnetic spectrum. And every frequency range in that spectrum has different properties. Visual light exist on that spectrum. What happens is that we as a species developed organelles (cones and rods) in our eyes that interact — pick up that spectrum. But that is a very narrow band in that spectrum.

Radio signals are much higher wavelength and lower frequency, and that range has several properties — good propagation through the air, little in the way of signal deterioration and interacts with wires and antennas. This means that you can emit signals in those frequencies they can be picked up somewhere else in the speed of light. It started with simple signals that created tones for someone to hear and interpret by a user, but it slowly became progressively more complex so that only electronic systems can process them, but the principal is the same.

EDIT: A correction as detailed below.

I think of it like your neighbors down the street screaming the sports game scores. Because you know what they are screaming, and because you recognize their voice, you can put together that it’s your neighbor yelling, and he’s yelling the sports scores. That’s how routers and internet works, just on a wavelength we cannot see or hear, nor does it interfere with other wavelengths.

It’s easier to understand when you know that we humans only see and hear a very small spectrum of all the spectrums that there are in the world.

AM audio broadcast is probably the easiest to explain since it’s not digital.
Let’s first start with audio. Audio is a pressure wave traveling through air. A pure wave is just a simple whistle or hum tone depending on the frequency. You can add frequencies together, if you do it randomly you will get white noise. If you do it in a very very specific way you will get spoken words or music.

Now we need to turn that pressure frequency somehow into electrical current. For that we can use the convenient tool called the microphone which can just do that 1 to 1.

If you now want to transmit it, you have to add just one more frequency which is called the carrier. Let’s pick on from the visible light spectrum for example green. AM stands for amplitude modulation and just means we make our green light brighter or dimmer. If we add our signal to the green light it gets brighter and dimmer exactly like our audio signal.

Everyone who sees our flickering light just needs to know that we added the green frequency to our signal. If they remove the green part they will have exactly the original audio signal and just have to feed it through some speakers to turn it back into pressure waves.

In reality the carrier frequency is much lower than visible light and there are many different and more efficient ways to add information to the carrier.

Radio and Wi-Fi signals work by transmitting information through electromagnetic waves. These waves are generated by alternating the electric and magnetic fields of the signal, which then travels through the air or other mediums, such as cables. The receiving device, such as a radio or Wi-Fi router, then decodes the electromagnetic waves back into usable information.