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best channel to use for 5GHZ Mode in AIRPORT EXTREME?

67957 Views 33 Replies Latest reply: Nov 8, 2013 11:17 PM by TallBearNC RSS
  • Catscratch Calculating status...

    Hi Bob,

     

    People should check supported Wifi channels in the wifi section on the System info on their Mac. Your observation is extremely useful to clear why this happens. Thanx

  • Catscratch Level 1 Level 1 (0 points)

    Hi Bob what MBP do you have? Mine is a mid MBP 2012 13 inch and only accepts the lower channels.

  • Bob Timmons Level 9 Level 9 (75,585 points)

    2008 MBP.  My Wife's 2008 iMac handles the same channels as the MBP.

     

    The iPad2 here will handle the higher 5 GHz channels as well.

  • TallBearNC Level 1 Level 1 (30 points)

    The higher the Ghz, the less penatrating.

     

    If you have 5Ghz issues penetrating walls and ceilings (like I do), set your 5Ghz channel to 36. I recommend getting a wifi tool call InSider (not sure if it's out for mac but it is for windows), and must be run on a PC/Mac with wifi. It will show you your wifi, and any around you, their channels, strengths, and give you a quality rating (based on signal strength, overlapping channels, and co-channels).

     

    Turns out all the 5Ghz traffice in my area is on 100+... once I changed it to 36 (well 36/40 since I use 40Mhz for more speed), I get a LOT better performance downstairs (AP is upstairs)... If I set to to 149, etc, my devices downstairs either wont even connect to the 5Ghz band , or only get about 10Mbps. Once I moved to CH 36, my devices downstairs pull no less Than 100Mbps.

     

    Remember the lower the Ghz, the more penetrating it will do. This applies to 2.4Ghz

     

    Also a few things. It's better to be ON the same channel as others vs NOT. Shared channels have a protocol built in to share the bandwidth. Overlapping channels cause interference, and that's FAR worse than sharing a channel (unless there's a lot of people). Id rather have 1-2 overlaps vs share with 10 people. Also signal is an issue. If a neighboring wifi signal is weak enough, you won't share, it will just be a little noise. This shouldn't affect you if you have a strong signal.

     

    Channels 1, 6, and 11 do NOT overlap if everyone uses 20Mhz. A lot of people think if someone is on 1, and they chose 2, they are home free... nope... When you pick a channel, it actually uses the spectrum of one channel LOWER and one HIGHER.. So channel 1 uses up "0" and 2. 2 uses up 1 and 3. 3 uses 2, and 4

     

    *****

     

    This is why 40Mhz (aka Fat channel) doesn't really work in the 2.4Ghz band unless there is hardly any 2.4Ghz routers nearby...

     

    Channel 1 @ 40 Mhz takes up "0", 1, and 2... then the other 20Mhz extention channel takes up 4, 5 and 6. (note it skips 3)

     

    The best 2.4Ghz, 40Mhz is either 1+5 or 11+7.. However overlaptop will occur on ch 6 if those 2 are near each other.

     

    Even if someone used channel 11 at 40Mhz, that WILL overlaptop with channel 1 @ 40Mhz as 11 takes up "12", 11*, 10, 8, 7*, 6. It must skip a channel so the 2 20Mhz channels don't overlaptop with each other.

     

    Uh oh... so even if you have EVERYONE use only channel 1 OR 11 @ 40Mhz, overlap occurs on Ch 6. Granted this is a small overlap.

     

    To avoid overlap, 2.4Ghz channels should really ONLY be run at ch 1 or 11. 6 Can be used if EVERYONE is only using 20Mhz channels, but many people don't.

     

    Also note if you run 40Mhz in the 2.4Ghz band on Channels 1 or 11, you will be "friendly" with people on channels 1, 5, 7, and 11 as those are the channels used. So if you see a 40Mhz channel using a wifi tool, and you only want to run at 20Mhz, pick 1,5,7,11.

     

    Granted all my advice assumes people are doing things RIGHT by using only channel 1 or 11 for 40Mhz, and 1,5,7,11 for 20... and in a PURE 20Mhz area, it's best to stick to 1,6,11 as they are as far apart as you can get.

     

    Some routers let you replace the firmware with opensource firmware and use channels that you normall could not use (like channels 14/15 for 2.4Ghz) and a LOT of other 5Ghz channels. 2 problems: 1) depending on your country, this may be perfectly legal, in the USA it is NOT as not all of the 5Ghz band is "free" 2) your wifi card, tablet, phone, laptop, etc may not except a "non standard" channel thats out of range for your country.. but some of those can be modified.

     

    I don't recommend doing the above unless you in a REALLY crowded area, and have no other choice. Even then, if it violates your countrie's broadcasting laws, you could be fined. Governments really don't mess around with broadcasts on un approved channels.

     

    * = Main or extention channel.

     

    5Ghz fixes a lot of this as the channels are NOT spaced 1 spot apart. They are spaced 4 channels apart, 36, 40, 44, 48, etc. Some older 5Ghz N routers lack many of the useable 5Ghz channels... plus the channels and number of channels are country dependent.

     

    So if I set my 5Ghz band at ch 36 @ 40Mhz, it uses 36+40 (technically it's 35,36,37+39,40,41). This helps keeps the signal far away from the next channel up 44... So my neighbor could use 44 @ 40Mhz and do (43,44,45+47,48,49)... and we are kept appart by Ch 42 which you aren't allowed to use

     

    Now if my neighbor did ch 40 @ 40Mhz, that WOULD overlap with me.. then I'd go knock on their door or leave them a note asking them to change it, or I'd just move mine.

     

    Most people don't have to manually set channels. All modern routers will auto set channels so they don't overlaptop (or minimize it if there's no other choise).

     

    **************

     

    There's one last thing you can do: buy a wifi booster... your neighbors will hate you, but you can blast your wifi signal so strong that either 1) ALL the routers/APs around you will automatically get FAR away from you, or 2) people will be forced to change channels if they manually do things

     

    Boosters are legal, to a point. After a certain point, at least in the USA, you will violate FCC regulations.

     

    But if you are in CROWDED, urban area, not even the 5Ghz spectrum has enough to keep people happy, and a booster just may be the way to go

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