You guys are smart, and some quick googling got me nowhere. Why baby monitors, WiFi and Bluetooth … All use same 2.4GHz frequency? I understand this is quite good frequency for home, indoor use and wall penetration etc…
But why is it exactly 2.4GHz? Why does WiFi not use 2.2GHz, bluetooth 3GHz and baby monitors 2.6GHz or 1.7GHz?
I have two hipothesis but I cannot validate them:
- For some reason this specific frequency is the only allowed for commercial use and other are used for military or other purposes?
- Interference would still happen if they would use mentioned frequencies since they are “close” together. If they use the same frequency, they can communicate and segment space more efficiently. But I do not know if this is actually happening.
You’re pretty close. Yes water absorption and therefore microwave ovens, but it also means that 2.4GHz is a terrible frequency to use for commercial radio. Leaves are full of water, as are clouds, and rain, which means long range propagation generally sucks. So it was reserved legally for Industrial, Scientific, and Medical uses, and it’s mostly a free for all with regards to transmission and interference.
You’re also correct that the band being unlicensed led to wide adoption in short range consumer radios due to lower costs. There is still compliance testing, but it’s done for things like the right to use the official WiFi logo, not to appease the FCC.