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I have an Airport Extreme (will find actual version number later, as it's not able to tell from Airport Utility any more) that runs a 2.4 and 5 ghz network. The 5Ghz one is almost always fast, but the 2.4Ghz one can produce some woeful speeds. The following screenshots showing me using my ISPs speedtest tool from the same iMac on each network:

Slow

Fast

I'm simply at a loss as to how to start troubleshooting this. It usually works fine, but sometimes is so bad I cannot even connect to it. The faster connection is pretty close to my maximum, so I'm happy with that - if I plug in direct via a cable it's usually similar to this.

It doesn't matter how far from the router I am, if it's decided to be slow, there is nothing I can see to either fix or troubleshoot it. The latest 7.6.1 firmware is on the AE, and it does not show any errors or warnings.

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2 Answers

up vote 6 down vote accepted

You are suffering from network congestion. Channel 11 is a very common channel and most 2.4GHz routers ship with that channel default. There are simply too many routers using channel 11 around your house.

However, not many people in your neighbourhood are using 5GHz channels, so that is free from network congestion.

The solution to this problem will be to change your 2.4GHz channel from 11 to something else.

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Also other devices such as household telephone wireless handsets also use the same 2.4Ghz spectrum as WiFi in the UK. Using the 5Ghz spectrum will bypass theses issues as well as the congested 2.4 range issues highlighted by @duci9y –  Stu Wilson Oct 22 '12 at 11:57
    
Handsets use 2.4GHz? I thought they used 2.45GHz. Bluetooth too, uses 2.4GHz, so it’s really crowded in 2.4GHz-land. –  duci9y Oct 22 '12 at 15:11
    
Cheers - seems to have made a difference, I'll be doing a sweep of all my kit and working out what doesn't support 5Ghz. Speaking as someone who has 11 internet connected devices within 2 paces, it may take a while to see if I can bin 2.4Ghz for good...! –  stuffe Oct 22 '12 at 18:23
    
You don’t need to kill 2.4GHz, just change channels until you find one that isn’t crowded. Though, to be future proof, it will be best to use 5GHz. –  duci9y Oct 23 '12 at 5:00
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If you've got a mac, you can see which channels are running on other nearby wifi networks. Just go to 'About This Mac' (apple menu) and click more info. Click 'System Report' and select Network - Wi- Fi from the left hand pane. In the interfaces section you'll your current network, then all other local wifi networks complete with channel and mode. Really handy tool for finding a free channel. 11 used a lot near me for 2.4Ghz and changing this made a real difference.

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There's also a great app called iStumbler which shows you all the networks around and their respective channels. Best to pick a channel with one free either side if possible (so if 3, 4, and 5 are free, choose 4). Doesn't seem to work for 5GHz though. –  chmac Feb 22 at 2:27
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