How does a song fly through the air into your radio?
Explored it? Here's the recap
How does a song fly through the air into your radio?
The short answer
A radio station hides your song inside an invisible wave by bending one of its dials, and the radio in your room reads that bend back into sound. AM bends how tall the wave is; FM bends how squished its wiggles are.
How it works
Every radio wave has two things it can change: its height (how big it is) and its spacing (how squished or spread-out the wiggles are). To send a song, the station keeps a fast wave going and gently bends one dial in time with the music. AM (amplitude modulation) bends the height up and down; FM (frequency modulation) bends the spacing tighter and looser. Your radio watches that dial move and turns it back into the sound you hear.
What people get wrong
Many people think one kind of radio just happens to sound nicer than the other, like it's luck. The real reason is where each one hides the music. A storm sprinkles random crackle onto a wave's height, so it wrecks AM, which keeps its message in the height. FM hides its message in the spacing, which the storm barely touches, so FM comes out clear.
The catch
FM sounds clearer, but it takes up more room on the dial and doesn't travel as far. AM is cracklier because it rides in the height that storms scramble, but at night AM waves bounce off the sky and can reach hundreds of miles, way past where FM gives up. Neither one wins everything; they each trade something.
Questions kids ask
Why does AM crackle in a thunderstorm but FM doesn't?
AM hides the music in the wave's height, and storms add random crackle right on top of that height, so the message gets scrambled. FM hides the music in the spacing of the wiggles, which the storm barely changes, so it stays clear.
If FM sounds better, why do we still use AM?
AM travels much farther. At night its waves bounce off a high layer of the sky and can reach hundreds of miles, so one AM station can cover a huge area. FM stays clearer but doesn't reach nearly as far.
What does the wave actually carry from the tower to my radio?
It carries a pattern, not the sound itself. The station bends a fast invisible wave in time with the music, and your radio watches how the wave is bent and rebuilds the sound from that pattern.
What do AM and FM stand for?
AM means amplitude modulation, which is a fancy way of saying it bends the wave's height (amplitude). FM means frequency modulation, which means it bends how squished the wiggles are (the frequency).
For grown-ups
A station transmits a steady high-frequency carrier wave and encodes the audio onto it. AM varies the carrier's amplitude; FM varies its instantaneous frequency. Additive noise lands mostly on amplitude, so an FM receiver with a limiter rejects it, giving FM its noise immunity and capture effect. The price is bandwidth: FM occupies far more spectrum per station (roughly Carson's rule), while AM's longer wavelengths refract off the ionosphere at night for big nighttime range.