Losing Your Wi-Fi Connection?
After connecting to a wireless network the airport extreme wireless network card in your iMac, Mac Pro or MacBook Pro gradually loses connectivity.
Common Symptoms:
- Wireless indicator located near the clock begins by showing full wireless connectivity but gradually reduces in strength bars
- The indicator may lose 1, 2, 3 or all of its strength indicating bars
- In most cases, eventually all connectivity will be lost and can be reconnected by selecting Turn Off Airport, rebooting or running the Network Diagnostic wizard
- The Console is showing the message kernelAirPort: Roam (Beacons Lost)
Explanation:
Issues such as this have been reported for many different reasons.
Recent forum activity indicates that this issue began occurring to users after installing version 10.5.3 or 10.5.4 of Mac OS X (Snow Leopard).
Other reasons can include incorrect security or channel settings.
Console Viewer:
kernelAirPort: Roam (Beacons Lost)
Solution – Set a Fixed Wireless Channel
- Open Finder , Applications , Utilities , Airport Utility
- Click Wireless
- Change Channel from Automatic to 12 (If channel 12 does not work then try different channels)
- Click Update
- Allow router to restart and reconnect to wireless network.

[...] Try changing the channel to 6 or 12 and see if that helps at all:- Apple Airport Extreme Connection Drops | proposed solution [...]
Try changing the channel to 6 or 12
No do channel 12 (or 13) if using a USA machine. USA Macs/Pcs are set to ignore these channels.