I can’t remember the last time I tuned in to an actual radio station. Back in my teenage years, my parents showed me how to record songs from the radio onto a cassette. Then piracy and MP3s swept in, and radio faded from my life.

It wasn’t until I heard a podcast outro — “This is a podcast from detektor.fm” — that I suddenly wondered: What the heck is FM?

That tiny question led me down a rabbit hole into the world of modulation and carrier waves — the century-old tech quietly powering everything from your phone calls to your Wi-Fi.

From sound, to electric signal, and back again

Every voice you hear on a radio — or through a video call — starts the same way: sound waves hitting a microphone.

Microphones are electromechanical transducers: they transform sound into electrical signals.

  • Dynamic microphones use a small magnet inside a coil attached to a diaphragm. When soundwaves hit, the diaphragm vibrates, and the magnet-and-coil movement generates an electrical signal through magnetic induction.

  • Condenser microphones use a parallel plate capacitor with a permanent electrical charge. Soundwaves make the diaphragm vibrate, changing the voltage and creating a signal.

Either way, your voice becomes an electrical signal ready for the next step: riding a carrier wave.

The carrier wave: your message’s invisible vehicle

A carrier wave is like a delivery truck for your message. We “modulate” it — change it in some way — so it carries the information:

  • AM (Amplitude Modulation) changes the wave’s height.

  • FM (Frequency Modulation) changes the wave’s spacing.

By Berserkerus — Own work, CC BY-SA 2.5

Once modulated, the signal travels to an antenna, becomes a radio wave, and flies invisibly through the air in all directions. Your device’s antenna catches it, turns it back into an electrical signal, demodulates it, and — after a bit of amplification — sends it to your speakers.

A short history, a lasting impact

In the 1890s, when Heinrich Hertz proved radio waves existed, the tech world shifted from wired telegraphy to wireless communication. Since then, carrier waves have evolved — but the principle hasn’t changed.

Even if you never listen to radio, modulation is all around you. Today it’s how:

  • Your phone makes calls

  • Your Wi-Fi sends and receives data

  • Your TV streams content

  • Your Bluetooth headphones work

In fact, the modem in your home — short for modulator-demodulator — uses carrier waves to encode and decode data so you can browse the web, stream music, or hold a video call halfway across the world.

Pratyeka, CC BY-SA 4.0, via Wikimedia Commons

Why it matters

Without modulation, there’s no Wi-Fi, no phone calls, no live sports streaming — basically, no modern connectivity at all. It’s the invisible infrastructure holding up the digital world.

So next time your Wi-Fi cuts out or your Bluetooth drops, remember: behind that frustration lies a century-old technology quietly doing its job.

Grandpa Radio may be over a hundred years old, but he’s still running the show behind your Netflix binges, Zoom calls, and Spotify playlists.

Thank you, and cheers, Grandpa Radio!