setting airport signal strength

If you are using Mac OS X 10.5.8 or have upgraded to 10.6.x.....

Open Macintosh HD > Applications > Utilities > AirPort Utility

Click Manual Setup

Click the Wireless tab just below the row of icons

Click the Wireless Network Options button

Adjust the Transmit Power to 100%, 75%, 50% or 25%

Click Done, then click Update to save any changes that you have made

The Express and other Apple routers are set to 100% by default, so if you are looking for a stronger signal, this operation will not help.

With later versions of AirPort Utility the setting is no longer available in the UI,

but you can use the "File -> Export Configuration File",

then edit the XML file with a text editor,

then you can reimport the file with "File -> Import Configuration File."

You can for example halve all the values after txpower.

This is of course more risky and obscure.