How Amplitude Modulation Carries Voice

You would need an antenna one hundred kilometers long just to broadcast your voice directly.

That is the physical limit of sending low-frequency human speech through the air.

To fix this, engineers use a trick called Amplitude Modulation. We take a high-frequency

radio wave that travels easily and we actually change its physical height to match the shape

of your voice signal. It is like piggybacking a slow message onto a fast runner. As long as we do

not push the signal too hard and cause distortion, your car radio just traces the outline

of that wave to play the music back.