[ELI5] For wifi why do we use a whole channel of 20MHz instead of a couple frequencies?

Question

So I get why we can’t use ONE single frequency, it’s sine and we can’t transfer data through it, it’s always gonna be constant. But what about using like 10 or 20 frequencies, something like from 2.4GHz to 2.4GHz10Hz (wrong syntax but you get what I mean). and use it to transfer the data.

I’m gonna give an other potentially wrong example, for radio, don’t we use one single frequency? we set our receiver to that frequency and get the transmitted data from the transmitter? or is it different from wifi because radio is simplex and wifi is half-duplex?

This ended up requiring 2 explanations (wifi and radio) but I’m more interested in the wifi use of a whole 20MHz channel instead of a smaller number of frequencies. Thanks.

In: 2

Answer 1

We can never use one frequency. Exactly one frequency cannot communicate any data at all. It’s just a constant unchanging signal. To transmit data, we need a range of frequencies, known as “bandwidth”. The “width” of the “band”.

The amount of data we can move (assuming everything else is perfect) is directly related to (and limited by) the bandwidth.

So… Using exactly one frequency has exactly zero bandwidth and is not very productive.