Advertisement
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 (#6 solid copper) connecting the lug to a good earth ground. See Figure 5.
Understanding RF Power Values
Radio Frequency 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
0 dB
1 dB
3 dB
6 dB
10 dB
12 dB
20 dB
30 dB
40 dB
All contents are Copyright © 2003 Cisco Systems, Inc. All rights reserved. Important Notices and Privacy Statement.
Factor
1 x (same)
1.25 x
2 x
4 x
10 x
16 x
100 x
1000 x
10,000 x
Cisco Systems, Inc.
Page 9 of 29
Decrease
0 dB
-1 dB
-3 dB
-6 dB
-10 dB
-12 dB
-20 dB
-30 dB
-40 dB
Factor
1 x (same)
0.8 x
0.5 x
0.25 x
0.10 x
0.06 x
0.01 x
0.001 x
0.0001 x
Advertisement
