I want to cover a large extension. So I need a omnidireccional antenna. I'm thinking in Air-ant2506, but I see that it is used as a bridge. Can I use this antenna if I don't want to use it as a bridge?
Yes, you can use the AIR-ANT2506 in a client <-> AP application. The AIR-ANT2506 is designed as a mast mount antenna implying external use in a bridge <-> application. The AIR-ANT1728 is a ceiling mount antenna with similar RF properties designed for indoor use.