This document provides information for the installation of antennas on
Cisco Aironet products.
Cisco recommends that you have knowledge of these topics:
The information in this document is based on these software and
Technical Tips Conventions for more information on document
You must place the antennas in a wireless network installation close to
the users. The location of the antennas do not need to be close to the
connected switch or to a computer room. The cable run can be 100 feet or more
from the AP or bridge to the antenna locations.
A coaxial cable carries radio frequency (RF) energy between the
antennas and the radio equipment. An antenna cable introduces signal loss in
the antenna system for both the transmitter and receiver. In order to reduce
signal loss, minimize the cable length and use only low-loss (LL) or ultra
low-loss (ULL) antenna cable in order to connect radio devices to antennas.
RF coaxial cable = loss of signal strength
Loss of signal strength is directly proportionate to the length of the
cable segment. As the diameter of the cable increases, signal loss decreases,
but at a much higher purchase cost. As signal frequency increases (a
higher-numbered channel), loss increases.
LL cable extends the length between any Aironet product and its
antenna. With a loss of 6.7 decibels (dB) per 100 feet (30 meters [m]) for LL
cable and 4.4 dB for the ULL cable, these cables provide installation
flexibility without a significant sacrifice in range or performance.
Cisco offers these LL and ULL cables:
20 ft (6 m)
50 ft (15 m)
100 ft (30 m)
150 ft (46 m)
Note: The use of Cisco antennas and Cisco antenna cables with your Aironet
wireless products ensures complete compliance with the requirements of these
Cisco LL and ULL cables are not plenum rated. Plenum rated cable is
Times Microwave Systems
A 100-foot cable can reduce the transmission distance by 30 percent.
That 30-percent reduction in range translates to an approximate 50-percent
reduction in coverage area (in square feet).
When you install antenna cables, be aware of these:
If you pull the coaxial cable too hard, its loss properties increase.
You must treat coax with care.
Curves in coax must not exceed the specified bend radius of the
The longer the cable segment is, the higher the signal loss is over
the full length of the cable. You can find the actual loss per foot in the
specifications of the manufacturer for that cable.
If any copper wire passes from outside to inside a building, use
lightning protection. Most countries require the use of lightning protection in
this cases. Check the local building regulations.
For outdoor-mounted antennas, seal with a good material like
Cisco has an
Bridge Range Calculation Utility to help you calculate power budgets.