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Why does FM sound better than AM?

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259 points zdw | 2 comments | 13 Oct 24 22:32 UTC | HN request time: 0.464s | source
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matrix2003 ◴[14 Oct 24 00:15 UTC] No.41832921[source]▶
Someone gave me an analogy some time ago that made a lot of sense.

If you shine a flashlight through a tree blowing in the wind and vary the brightness to convey information, the signal can get distorted pretty easily.

However, if you have a constant brightness source and vary the color, it’s a lot easier to figure out what the source is trying to convey.

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ra ◴[14 Oct 24 05:57 UTC] No.41834625[source]▶
That's not the real story. The RF environment is noisy, with naturally occuring static "sparks", but also with manmade RF noise.

This static and RF noise is AM. It's impossible to filter it out from an AM signal, and so the background noise gets amplified with the signal.

Encoding the signal in a modulated frequency (FM) means we don't need to amplify the detected AM signal and it's associated background noise.

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cbolton ◴[14 Oct 24 06:45 UTC] No.41834857[source]▶
That's exactly what the parent comment described in the beautiful example where the AM noise is due to moving tree leafs affecting the intensity of transmitted light, and you can fix it by varying color, which means varying the frequency spectrum of the light.
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1. ikekkdcjkfke ◴[14 Oct 24 10:08 UTC] No.41836007[source]▶
How does the radio follow the frequency modulations if the radio cannot "see" at a specific direction?
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2. cbolton ◴[14 Oct 24 10:49 UTC] No.41836272[source]▶
In the example, the amplitude of the flashlight signal is distorted by the movement of the trees. The signal is never completely hidden. Not sure if that answers your question...