Actually channel 11 is available in the North America. Since you are trying to use 11, that tells me you are trying to do 802.11n on 2.4 GHz. In the 2.4 GHz spectrum, you have 3 non over lapping channels... 1, 6, and 11... each of these channels are 22 Mhz wide. This means if you were using 802.11g on channel 11, it would actually go from channel 9 all the way to channel 13. This would give you the full 22Hz bandwidth of channel 11. Wher you site the channel in your AP or router is actually the center of the channel.

Now you already konw you are trying to use a 40 Mhz wide channel here. You are basically bundling two 2.4 GHz channels together to give you the higher bandwidth. If you try to start at channel 11, that would be 20 Mhz above and 20 MHz below. This would put you over channel 13 which is not allowed. You need to set your router to a lower channel so your 40 Mhz wide spectrum does not go above channel 13.

Check this page out, and scroll down to 802.11n. You can see a picture of the specturm with the channels: http://en.wikipedia.org/wiki/IEEE_802.11

If you were using the 5 GHz sectrum, you would have many more channels to move around in.

Hope that explains it for ya.

 

Quote:

Originally Posted by Thorn-Blade Actually channel 11 is available in the North America. Since you are trying to use 11, that tells me you are trying to do 802.11n on 2.4 GHz. In the 2.4 GHz spectrum, you have 3 non over lapping channels... 1, 6, and 11... each of these channels are 22 Mhz wide. This means if you were using 802.11g on channel 11, it would actually go from channel 9 all the way to channel 13. This would give you the full 22Hz bandwidth of channel 11. Wher you site the channel in your AP or router is actually the center of the channel. Now you already konw you are trying to use a 40 Mhz wide channel here. You are basically bundling two 2.4 GHz channels together to give you the higher bandwidth. If you try to start at channel 11, that would be 20 Mhz above and 20 MHz below. This would put you over channel 13 which is not allowed. You need to set your router to a lower channel so your 40 Mhz wide spectrum does not go above channel 13. Check this page out, and scroll down to 802.11n. You can see a picture of the specturm with the channels: http://en.wikipedia.org/wiki/IEEE_802.11 If you were using the 5 GHz sectrum, you would have many more channels to move around in. Hope that explains it for ya.

So if I am understanding correctly if I use channel 11 with a 40MHz band width I am effectively only getting 20MHz since it is over the allowed band spectrum?

What confuses me is that I am able to set my router to channel 13 with a 40MHz band width (my netbook also detects it as channel 13) which would mean I am using channels 9 to 17. How is that possible? or am I actually only using 9 though 11?

 

It is very possible that your hardware could allow you up over 13. For commerical equipment we order from Cisco, we actually order hardware specific for the area it is going to be in. (This could be outside the US.) The vendor of your hardware may export to other countries where higher channels are allowed, and not make a speicific model for them.

I am not really sure what happens if you try go over over 2483.5 MHz (Channel 14 which is restricted). I have never been asked this question before, and I have never thought about it. I will have to do some digging.

Here is another link for you: http://en.wikipedia.org/wiki/List_of_WLAN_channels

 

I have used channel 13 (which is not allowed in where I live) but getting things to connect was a pain. My PCI Atheros wifi card would allow it while using wildpackets peek drivers, but my netbook won't seem to allow it. Also, any friends that come over were (generally) unable to connect. I gave up using it after that.

Never even bothered with channel 14... DD-WRT allows me to set it, but I couldn't connect or even verify it was running from anything.

They are blocked because they can (could?) interfere with the restricted frequencies. I disregard that in search of less WiFi interference