Faithful reader Dick Fiddler has a question regarding cordless phones and Wi-Fi interference. He writes:
I'm having interference issues with my AirPort network and cordless phone. Repositioning has helped some, but I'd like to pursue restricting the channels used by the Extreme. Unfortunately, I need a little more information to make it work. My Uniden phone says only "5.8 GHz" with nothing in the specs at all. The Airport Utility seems only to list channels without much reference to which are which. Any ideas on how to figure out which channels to use?
After researching the subject in greater depth I'm going to take the advice of my betters--and pass that advice along to you.
Leave it alone.
And by it I mean them and by them I mean the settings you find in the Wireless Options sheet of AirPort Utility. By default your base station is configured for automatic radio mode and channel selection. This is a good thing. And it is because when you first start up the base station it scans its environment and picks the channel that provides the best performance. Yes, you can choose specific channels, but they may provide worse results than what you're currently getting.
However, over time the base station's automatic setting may no longer be the best choice. For example, when you (or others around you) introduce devices that cause interference. If you find that your signal has degraded, unplug the base station, wait a minute, and plug it back in. This will cause it to once again scan the area and pick the best channels (which may now be different than the ones it picked the last time it was powered on).
If you're certain that your phone is the problem I'd suggest that you replace it with one that supports the Digital Enhanced Cordless Telecommunications (DECT) standard. This standard is sometimes referred to as "Wi-Fi Safe" because, unlike the 5.8GHz phone you're currently using, it doesn't crowd into the Wi-Fi spectrum and cause interference. All the major cordless phone manufacturers support DECT and they're so common that you don't pay a premium for them. I have a Panasonic DECT phone sitting within three feet of my AirPort Extreme base station and it doesn't cause a problem.