Ceiling-Mount Antennas

Ceiling-Mount Antennas

One of the most common indoor mounting locations for an antenna is the drop-ceiling support grids. The AP can be located above the ceiling tiles, and the antenna placed below the ceiling (providing the AP has the proper ratings, as explained in Chapter 12, "Installing WLAN Products"). The most common such antennas are omnidirectional, with fairly low gain ranging from 2 dBi to about 5.2 dBi.

An antenna that provides good coverage in offices and locations with fairly low ceilings, and yet has an excellent "stealth" capability, is a low-gain, low-profile ceiling-mount diversity antenna. Sometimes called a squint antenna, this blends into the ceiling very well. The antenna shown in Figure B-4 is manufactured by Cushcraft Corporation. When using antennas that mount to the ceiling grids, verify that the antenna mounting and the ceiling tiles are compatible. In some cases, the ceiling tile itself might extend down below the grid, causing interference for the antenna mounting.

Table B-2 lists the specifications for the Cushcraft 2-dBi squint antenna.

The antenna shown in Figure B-5 is a 5.2-dBi ceiling-mount from Cushcraft Corporation. It is provided with a clip that attaches directly to the drop-ceiling support grids, and hangs down about 9 inches. This antenna is not a good selection for low ceilings because it invites meddling by curious fingers, especially in public areas. For higher ceilings such as retail environments, however, it is an economical antenna, providing 3 dB of gain over a standard dipole.

Table B-3 lists the specifications for the Cushcraft 5.2-dBi ceiling-mount omni antenna.