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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: 0.532s | 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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beala ◴[14 Oct 24 01:10 UTC] No.41833220[source]▶
This makes a lot of sense so long as your source of noise is something like a tree swaying in the wind, ie something that interferes with the amplitude. If instead the source of noise is uhhh a piece of stained glass swaying in the wind then blinking the flashlight is the better bet. I guess it just turns out radio interference is more like the tree. But why?
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1. bee_rider ◴[14 Oct 24 01:24 UTC] No.41833304[source]▶
The stained glass would change the amplitude of some light selectively. But because the FM radio works at different distances, I wonder if it must have some way of adjusting for different amplitudes anyway?
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2. xeyownt ◴[14 Oct 24 05:44 UTC] No.41834547[source]▶
Yes, stained glass is like band filter, they let through a particular frequency range, while reducing those outside the range. Your FM receiver will still lock on the desired frequency as long as their is enough signal strength. It's kind of the same as listening to an emitter that is very far while being very close to another. Of course, it'll stop to work at some point depending on minimum signal-to-noise ratio.