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I don't quite understand the WLAN channel display. Elsewhere in the UniFi Network Controller, the channel is set to 1. But what does the number 3 in the display below mean?

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To clearify the situation i added three more screenshots with different WLAN settings. Because the behavoir also exist with channels in mid i dont think it has to do with borders, but the channel width seem to have an effect.

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    An 802.11b 2,4 GHz Wi-Fi connection uses a band 22 MHz wide, which is three channels, and other 802.11 2.4 GHz variants can use even wider bands. The WAP seems to have chosen channel 3 as the center of a 40 MHz band because it would extend outside the allowed frequency on channel 1.
    – Ron Maupin ♦
    Commented Mar 10, 2021 at 23:54
  • Did any answer help you? if so, you should accept the answer so that the question does not keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer.
    – Ron Maupin ♦
    Commented Dec 23, 2021 at 17:01

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In the 2.4 GHz band, there are three non-overlapping bands for 802.11b/g/n from which you can choose for the 22/20 MHz bandwidth (the EE term, not the networking term). Those are channels 1, 6. and 11 as the center of the band. Choosing a different channel can be problematic if there are neighboring devices using the non-overlapping channels because you will overlap your band with the neighbor bands, causing interference and noise in your and the neighbor bands,

With 802.11n using 40 MHz bandwidth, You must use channel 3 instead if channel 1 as the center of the band because channel 1 would have the band extend below the frequencies allowed.

Wikipedia has an article about the channels.

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  • Many WLAN scanners and even the UniFy Network Controller show multiple numbers for the channel description, that's what confuses me. So far I have assumed that simply the position of the center frequency of the channel determines the channel number?
    – fitcfitcfatc
    Commented Mar 11, 2021 at 20:34
  • When you pick a channel number, that is the center channel of the band you want to use. Different variants of 802.11 will have different widths for the band. You seem to want to use a band that is 40 MHz wide, and you cannot use channel 1 as the center of the band as the lower end of the 40 MHz band would extend below the legally allowed frequencies for 802.11.
    – Ron Maupin ♦
    Commented Mar 11, 2021 at 20:39
  • I think I have understood this principle. But why does my UniFi Network Controller show me only channel number 1 elsewhere in the application (in the scenario in the first image above "3 (1,+1)VHT40")? The actual channel number should be 3, right?
    – fitcfitcfatc
    Commented Mar 11, 2021 at 21:00
  • It is showing that it automatically changed it to channel 3 in your first image. If other parts of the application show it as channel 1, then that could be a bug you should report.
    – Ron Maupin ♦
    Commented Mar 11, 2021 at 21:03

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