Datasheet

Reference Guide

Figure 5. Cisco Aironet Lightning Arrestor

The accepted IEEE transient (surge) suppression is .000008 seconds (8 micro seconds). The

Lightning Arrestor is a 50-ohm transmission line with a gas discharge tube positioned between

the center conductor and ground. This gas discharge tube changes from an open circuit to a short

circuit almost instantaneously in the presence of voltage and energy surges, providing a path to

ground for the energy surge.

Installation

This arrestor is designed to be installed between your outdoor antenna cable and the Aironet

wireless device. Installation should be indoors, or inside a protected area. A good ground must be

attached to the arrestor. This can be accomplished by use of a ground lug attached to the arrestor

and a heavy wire (no. 6 solid copper) connecting the lug to a good earth ground. See Figure 6.

Understanding RF Power Values

Radio frequency (RF) signals are subject to various losses and gains as they pass from transmitter

through cable to antenna, through air (or solid obstruction), to receiving antenna, cable, and

receiving radio. With the exception of solid obstructions, most of these figures and factors are

known and can be used in the design process to determine whether an RF system such as a

WLAN will work.

Decibels

The decibel (dB) scale is a logarithmic scale used to denote the ratio of one power value to

another—for example:

dB = 10 log10 (Power A/Power B)

An increase of 3 dB indicates a doubling (2x) of power. An increase of 6 dB indicates a

quadrupling (4x) of power. Conversely, a decrease of 3 dB is a halving (1/2) of power, and a

decrease of 6 dB is a quarter (1/4) the power. Some examples are shown below in Table 1.

Table 1. Decibel Values and Corresponding Factors

Increase Factor Decrease Factor

0 dB 1 x (same) 0 dB 1 x (same)

1 dB 1.25 x –1 dB 0.8 x