CompTIA Network+ Certification All-in-One Exam Guide, Eighth Edition (Exam N10-008), 8th Edition by Mike Meyers & Scott Jernigan

Author:Mike Meyers & Scott Jernigan [Mike Meyers]
Language: eng
Format: epub
Publisher: McGraw-Hill
Published: 2022-02-10T16:00:00+00:00

Figure 14-26 Patch antenna

Polarization and Antenna Alignment All radio signals have a property called polarization, which describes the orientation of the radio waves. The polarization of a Wi-Fi signal depends on the antenna, though linear polarization (meaning the waves all oscillate in the same direction) is the most common. In addition, these polarized antennas and emitted signals can be oriented in several ways, such as vertically, horizontally, and slanted (like a 45-degree angle).

When you adjust a Wi-Fi antenna or rotate the device it is attached to in physical space, you effectively change the angle (orientation) of its signal. When the receiving antenna aligns with the polarization of the transmitter, this creates the strongest signal. The greater the misalignment between receiver and transmitter, the weaker the signal. Misaligned polarization can lower a network’s effective range and throughput. Let’s look at a scenario with Ellen the network tech to show the impact of misalignment more clearly.

Ellen wants to connect two buildings in her organization via Wi-Fi. With both antennas aligned vertically, the connection will be strong and solid. If she sets one antenna to vertical and the other to horizontal, on the other hand, a 90-degree difference, the signal strength would drop by 18 decibels. Every 3 dB equates to a doubling (or halving) of power, so –18 dB represents a 98.4 percent loss in power.

The math isn’t important for the CompTIA Network+ exam, but the outcome is. In a worst-case cross-polarization scenario like Ellen’s network, the connection would be 1/64 the comparable signal strength when compared with the same configuration using common (aligned) polarization. Ouch!

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