I have a 1310 bridge with and AIR-ANT24120 external antenna. Problem is that the signal strength is very weak when using this antenna (RSSI -80 -90 for associated clients. I have swapped the antenna for a new one with the same results. I then swapped the antenna for a 2.2 dbi omni and could cover almost 3 times the area. I have changed power settings the dbi assigned to the external antenna etc. The antenna was plugged directly into the 1310 and I am using the 1 foot cable supplied by Cisco for the power injector. I have run out of ideas.
How many users are there receiving the signal from your antenna?. Let me know this information. Also, did you try using any other antenna apart from the mentioned external antenna?. If yes, then let me know what is the other antenna you tried?.