How to enable 5GHz channel 100 on OpenWrt

If you open this link to see 5GHz channel allocation you will find 2 green blocks. The first block has channels 36, 40, 44, and 48. The second block has channels 149, 153, 157, 161, and 165. As far as I understand, these blocks can be used in any country. As a result, many routers only allow you to choose only these channels for a 5 GHz network. All channels between these are co-called DFS channels, and their usage is different in each country.

DFS channels have some rules that are different in each country and that routers must follow.

But what will happen if you try to use any of those DFS channels? For example, let’s try to use channel 100. In the case of OpenWrt, this will just disable the 5Ghz network completely. This is because we didn’t specify the country. Without this information, OpenWrt does not what the rules are and disables the network.

You can set the country in the “Advance Settings” tab of your wireless network. The next explanation will be for the USA because I don’t know the rules in other countries. If you set the US as the country and put channel 100 again, your 5 GHz Wi-Fi will look like it still does not work, but it will start working in one minute. Basically, the router will try to detect the usage of radar. If it is detected, the router will switch channels or will reject to work.

From my research, it looks like it is quite rare to have radar nearby. Even people who live in cities with huge airports like Los Angeles are reporting that there are no radars or something similar and they are totally ok to use DFS channels.

But why would you use channel 100 in the first place? Well, most routers avoid it and as a result, nobody in your neighborhood uses it. It is free to use. Moreover, you can use 20, 40, 80, or even 160 MHz wide channels without worrying about interference. Especially it is good if you live in an apartment with many Wi-Fi networks.

Are there any disadvantages when using the DFS channel? From what I read clients connect slightly slower and if you need to restart the router, your Wi-Fi network will come online one minute later than usual.

I’m using channel 100 for 2 weeks and so I didn’t see any issues.

I hope it helps someone.a

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