In many situations, line of sight (LOS) is not considered to be a problem, particularly for WLAN devices that communicate over short distances. Due to the nature of radio wave propagation, devices with omnidirectional antennas often communicate successfully from room to room. The density of the materials used in the construction of a building determine the number of walls the RF signal can pass through while still maintaining adequate coverage. The impacts of various materials on signal penetration are as follows :

• Paper and vinyl walls have little effect on signal penetration.
• Solid and precast concrete walls limit signal penetration to one or two walls without degrading coverage.
• Concrete and concrete block walls limit signal penetration to three or four walls.
• Wood or drywall allows for adequate signal penetration for five or six walls.
• A thick metal wall causes signals to reflect off, resulting in poor signal penetration.
• Chain link fence wire mesh with 2.5 cm to 3.8 cm (1 to 1.5 inch) spacing acts as a 1.3 cm (0.5 inch) wave that will block a 2.4-GHz signal.

When connecting two points, the distance between them, obstructions, and antenna location must all be considered. If the antennas can be mounted indoors and the distance is short, the standard dipole or magnetic mount 5.2 dBi omnidirectional or Yagi antenna can be used.

For long distances of 0.8 km (0.5 mile) or more, directional high-gain antennas such as a Yagi or Parabolic Dish must be used. These antennas must be as high as possible, and above obstructions such as trees and buildings. If the directional antennas are used, they must be aligned so that their main radiated power lobes are directed at each other.

The U.S. FCC requires professional installation of high-gain directional antennas for systems that are intended to operate solely as point-to-point systems and have total power exceeding the 36 dBm EIRP. The EIRP is the apparent power transmitted toward the receiver. The installer and the end user are responsible for ensuring that the high power systems are operated only as point-to-point systems.

When designing a system, it is important to realize that if the site-to-site antenna was installed and tested during the winter, problems may occur in the spring. During the spring, the leaves return to full foliage and low-power microwaves will bounce off leaves like a mirror when they are wet. Therefore, a strong winter signal may become a weak signal in the spring.

If the root and non-root bridges are not associating with each other, try performing RF troubleshooting shown in Figure .