RF Propagation
You should be familiar with two different antenna types:
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Omnidirectional antennas
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Directional antennas
Omnidirectional antennas propagate the Wi-Fi signals the same in all directions. Most manufacturers provide this antenna type on their APs, wireless routers, and client devices. Omnidirectional antennas do well in most facilities.
Figure A-7 shows a pair of omnidirectional antennas.
Figure A-7. Example of Omnidirectional Antennas
Wireless networking vendors usually sell high-gain omnidirectional antennas (see Figure A-8 for an example) for use with their products. This allows a larger Wi-Fi coverage area in all directions.
Figure A-8. Example of a High-Gain Omnidirectional Antenna
Directional antennas, however, focus the Wi-Fi signals and provide much greater wireless coverage in one direction than in others. Unlike omnidirectional antennas, most directional antennas are external, meaning you need to mount the antenna somewhere and connect the antenna cable to the AP or wireless router. Figure A-9 shows an example of a directional antenna, called a patch antenna. Figure A-10 depicts how this antenna type might propagate the Wi-Fi signals.
Figure A-9. Example of a Patch Antenna
Figure A-10. Coverage Area of a Patch Antenna
A directional antenna is useful when you want more horizontal than vertical coverage, such as when providing coverage for a long set of offices.