Some WiFi channels cannot be used
If we focus on the 2.4 GHz band, which is the one that has limitations in some channels, we can say that they exist from 1 to 14. Of course, 14 was the last one added and many devices are not compatible, in addition to the fact that most countries prohibit using it. However, beyond that issue, you may find that you cannot use other channels because they are prohibited.
This is what happens, for example, in the US. There it is not possible to use channels 12 or 13, in addition to the already mentioned 14. Even in Spain, 14 is also restricted, as in all of Europe. In fact, only Japan allows you to use that channel. This means that the use of WiFi is not the same in all parts of the world.
Why is this happening? To answer that question, you need to know how wifi networks work. Like a radio, for example, they also transmit information through waves. This means that there may be interference. It is the same as if an FM radio station is on almost the same frequency as another channel.
The reason certain channels cannot be used in some countries is because they may interfere with satellite radio waves. This is the case of channels 12 and 13, for example, in the United States. There they do not allow them to be used in a general way to prevent frequencies from leaking and creating problems. They only allow them to be used in low-power mode, but this is really not convenient for the user, since it would work worse.
Channel 14, the most restricted
There is a channel different from the rest: 14. It was the last one to join the 2.4 GHz band and uses a higher frequency, so it is much further away from the rest. Once again, the fact that you can interfere with communications and generating conflicts, means that it cannot be used in practically any country in the world, except Japan.
Basically the reason is avoid interference in satellite phones, which use a nearby frequency. Hence, although this channel is compatible with many devices, in practice it is not really used at the user level. In fact, as you have seen, there are countries where the use of the 2.4 GHz band is basically limited to the use of channels 1 to 11.
What can we do to avoid interference problems if we also cannot use some channels? This will depend on where you connect and how many routers you have around you, but it is not uncommon to find a channel or channels that are saturated. In this case, the best way to avoid problems is use the 5 GHz band. There you will find more channels available and also do not interfere with each other. You can always see the WiFi channel you are using.
However, you can use apps like Wi-Fi Analyzer to find the best channel in Windows. In this way you will connect to the one that is freer and you will have a considerable improvement in terms of signal quality.
