In the web interface, if one goes to:
Network Interfaces/Radio0-802.11G/Setting tab
half way down the page there's a section called External Antenna Configuration and you can enter an Antenna Gain in the box.
The access point came originally with two small plastic antennas, about 6 inches long but I took these off and connected two external antennas, one is 3db, the other 6db. Should I enter 6db in the box or does the access point set the gain automatically? At the moment all antenna settings are at default.