AM and FM Radio

Riding a message on a carrier

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Messages ride on a high-frequency carrier: modulation.
• AM varies the strength (keep depth ≤ 100%); FM varies the frequency and resists noise.
• Modulation creates sidebands, which set how much bandwidth a station needs.

Steps

1. Why not send sound directly?
2. Modulate the carrier
3. Tuning in
4. Why FM sounds cleaner
5. How many stations?
6. Hearing the bandwidth