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Cables

The antenna should be mounted at a location that utilizes its radiation pattern to maximum performance for the users. In some cases, this is not an ideal location to mount the AP. Therefore, it is sometimes desired to separate the antenna from the AP or radio device. This can be due to the necessity to mount the antenna outdoors and keep the AP indoors, or to mount the AP in the ceiling and mount the antenna below the ceiling. Sometimes customers may even want to keep the AP in a wiring closet and place the antenna out in the user area.

Understanding RF Power Values," cabling introduces losses into the system, lowering signal level from the transmitter to the antenna, as well as reducing the signal level moving from the antenna to the receiver. In both cases, this has a dramatic effect on the RF coverage area.

Cable designed carrying RF for WLAN is a coaxial cable and must be selected to match the impedance of the transmitter and antenna. Virtually all WLAN systems utilize 50-ohm antenna system impedance, and the cable selected must match this value.

A wave traveling down either a wire or in the open air has a distinctive physical characteristic to it: its length. One relationship that occurs in RF is that as the oscillations or frequency of a wave becomes faster, the overall length of the associated wave (called wavelength) becomes shorter.

As frequencies of signals change, they are affected differently by the surroundings. In a wire, as electrons travel down the conductor, they have opposition called resistance. As the frequency of that electrical signal increases, the electrons in the wire are moving faster and faster. They tend to move toward the surface of the conductor, which is called skin effect. This actually increases the resistance to electron travel (because they use only the skin, or outside portion, of the cable), and therefore reduces the amount of energy reaching the end of the wire. To offset this skin effect, many coax cables, designed for microwave frequencies and higher use cables of significant physical diameter, for lower loss.

Many cable types appropriate for WLAN environments are available today. attenuation (energy losses) that are associated with these cables.