[darken]

I believe they fall under the "amateur" bands. I.e. frequencies not requiring a license to utilize (given you obey given power limits). That's why the same frequencies are shared by WiFi, Bluetooth, ZigBee, etc.

Some of the amateur bands also overlap with allocations for things like radar. For example, a subset of the "5Ghz" WiFi channels (the "DFS" channels) can only be used if the access point will auto switch to a different channel upon detecting a radar pulse.

[vvoid]

I believe you're thinking of the ISM bands - problematic chunks of the spectrum that are given over to industrial, scientific and medical technologies that emit RF by design. The FCC allows a bit of part 15 free-market anarchy on these bands so long as manufacturers limit power and print a familiar disclaimer on the device. By contrast, the amateur radio service does require a license.

This is actually a chart that shows who is legally protected from interference. A license holder of a service listed in a colored bar has the right to complain if there is another emission on their spectrum. (There are also "primary" and "secondary" users for some ranges, the latter expected to yield to the former). According to that chart, a radiolocation service is the primary user. Amateurs can then work around them (1.5KW earth-moon-earth wifi anyone?) and finally wifi is allowed to exist with all the other random gadgets.

Yes, WiFi is given nearly the lowest priority for a small slice of the spectrum that is full of garbage from other users. No wonder it's so good at beamforming, spread spectrum use, channel hopping, and so on.

[tesseract]

"Amateur" in the context of this chart specifically means licensed amateur radio aka "ham radio".

[Dylan16807]

But if I go look between 5 and 5.6 GHz I don't see any mention of "amateur". That's where most of the 5GHz range is.

[sidewndr46]

No, you cannot use WiFi on an amateur band for a whole host of reasons.