Cisco Aironet 1600 Deployment Manual page 60

A Quick Look at a few "Non-Optimal" Installations
Figure 79 Example of a poor installation – Access Point is too high & buried in conductive foil
Remember the best place for an Access Point is as close to the users as possible – Avoid metal or
conductive objects in the near field (they cause the radio waves to become directional and increases nulls
(dead spots). If you must mount the AP in a high ceiling, look at directional antennas to direct (angle
down) the signal to the intended target area and always mount dipoles in the correct orientation.
Figure 80 When using dipole antennas observe the correct orientation (vertical polarity)
Cisco Aironet Series 1600/2600/3600 Access Point Deployment Guide, Release 7.5
60