Cisco Aironet 1600 Deployment Manual page 52

Understanding 802.11ac and the option module
Figure 67 Top covers removed from AP and module to show how antennas are mounted
Figure 68 Coverage is optimized for ceiling placement and radiates omni-directionally
If the AP is not mounted on the ceiling but rather on a wall, this may acceptable for smaller deployments
such as hotspots, kiosks, transportation or smaller coverage areas but in an enterprise deployment it
could cause excessive roams as the signal (think of the diagram above turned on its side) signal can
radiate on the floor above and below rather than downward in a uniform 360 pattern. See Figure 20.
If the module is installed in an AP 3600e (with external antennas) the 802.11ac module will still behave
as described in Figure 68 and if the dipole antennas are used, the AP will continue to provide an
omni-directional coverage pattern. If a patch or other directional or high gain antenna is used, it can
create a condition where you have two different coverage patterns. Since both the 5 GHz module radio
and the internal 5 GHz 802.11n radio both work together as one "blended" radio it is best to keep cells
uniform by using dipoles or by verifying coverage is acceptable for your intended application.
Cisco Aironet Series 1600/2600/3600 Access Point Deployment Guide, Release 7.5
52