Polarization

Polarization
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Polarization

Antenna polarization, refers to the alignment or orientation of the waves.
When installing antennas an important consideration is antenna polarization.
It is important to have the polarization of the transmitting and receiving antennas oriented the same in order to receive the strongest possible signal.
As waves radiate from an antenna, the amplitude of the waves can oscillate either vertically or horizontally.

Indoor Communications

Polarization is not as important for indoor communications because the polarization of the RF signal often changes when it is reflected, which is a common occurrence indoors.
Most access points use low-gain omnidirectional antennas, and they should be polarized vertically when mounted from the ceiling. Laptop manufacturers build antennas into the sides of the monitor. When the laptop monitor is in the upright position, the internal antennas are vertically polarized as well.

Outdoor Communications

When aligning a point-to-point or point-to-multipoint bridge, proper polarization is extremely important. If the best received signal level (RSL) you receive when aligning the antennas is 15 dB to 20 dB less than your estimated RSL, there is a good chance you have cross-polarization.
If this difference exists on only one side and the other has higher signal, you are likely aligned to a side lobe.

Reference:
Coleman, David D.,Westcott, David A. CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-106 Wiley.