I was told by a wifi tech that the "pipe bomb" antenna [air-ant2506] should be installed upside down when installing inside a building, ie warehouse.
When I go to the hardware installation page for the antenna, Cisco makes no statement regarding this....they clearly show the antenna with the metal end at the bottom, not top.
http://www.cisco.com/en/US/docs/wireless/antenna/installation/guide/ant2506.html
Ultimately does it really matter which end is up if you are mounting inside? Just as long as it's vertical correct?