1 of 3 macs in home keep droping off AE network

Question

Have had my 3 macs and airport extreme network working fine for 2 years. Now one of the 3 is starting to drop off the network and does not always respond to my password to re-access. Very slow internet when it is on the network. Works fine off my neighbors unprotected network.
No change in range and my macbook works fine sitting next to the troubled imac so no range problem. Also, iPad wifi is fine throughout the house
Any ideas??

Answer 1

That's plenty strong enough.  Another explanation for what you're experiencing is noise.  To see the noise level that Mac is experiencing, nn your Mac pull down the Apple menu and select "About This Mac".  In the resulting window click on "More Info".  In the resulting window select "AirPort" under the "Network" category.  On the right under the name of your wireless network you'll see to the values to the right of "Signal / Noise"?  In a "quiet" environment a typical noise level is in the -90s.
To compare the signal and noise on that Mac with what the other Macs are seeing, you can use the advice in the second message of this thread.
There's one other thing you can try.  It might help to reset the connection settings on your Mac using these steps one at a time until the problem is resolved, recognizing that, depending on your problem, not all of these steps will make sense:
1) Use the AirPort menu bar item to turn AirPort off, then on again.
2) Try to select your Wi-Fi network from the AirPort menu.
3) In the Network panel of System Preferences delete the AirPort item from the left column, then add it back.
4) In the same panel as (3), define a new location and see if you can make that work.
5) In the same panel, select the AirPort connection item, click the "Advanced" button, select the "TCP/IP" tab, then click "Renew DHCP Lease".  Note that the fix this step implements may be temporary.
6) In the folder /Library/Preferences ( _not_ <yourhomefolder>/Library/Preferences), move the folder SystemConfiguration onto the Desktop, then restart your computer. See if you can now make your AirPort connection work.
These steps may not help, but they'll only take a couple of minutes to try.  Before you try these, if you have any special network settings on your Mac for things like DSL credentials, note all your network settings, because the latter steps will destroy them.  If you got all the way to the last step, if things don't work any worse than before, you can trash the saved SystemConfiguration folder.