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Why does FM sound better than AM?

(www.johndcook.com)
259 points zdw | 1 comments | 13 Oct 24 22:32 UTC | HN request time: 0.206s | source
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massysett ◴[14 Oct 24 00:39 UTC] No.41833059[source]▶
What I’ve never understood is how the FM receiver can lock on to the signal if its frequency is always changing. Doesn’t the receiver need to lock on to something? If the answer is “it locks on to the amplitude, which doesn’t change,” well AM is bad because the amplitude is subject to interference, so wouldn’t FM have the same problem?
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1. CodeBeater ◴[14 Oct 24 01:14 UTC] No.41833237[source]▶
Most FM receivers nowadays rely on creating a signal of a specific frequency that interferes with the desired on-dial frequency, this is called an intermediate frequency. Then the actual audio signal is analogous to the changes on that IF.

This technique is known as superheterodyne, and Technology Connections has a wonderful video explaining it better than I can.