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Cisco Aironet 1570 Series Outdoor Access Point Hardware Installation Guide
OL-32138-01
Chapter 2 Installing the Access Point
Avoiding Damage to Radios in a Testing Environment
• If any part of the antenna system should come in contact with a power line, do not touch it or try to
remove it yourself. Call your local power company. They will remove it safely.
If an accident should occur, call for qualified emergency help immediately.
Avoiding Damage to Radios in a Testing Environment
The radios on outdoor units (bridges) have higher transmit power levels than radios on indoor units
(access points). When you test high-power radios in a link, you must avoid exceeding the maximum
receive input level for the receiver. At levels above the normal operating range, packet error rate (PER)
performance is degraded. At even higher levels, the receiver can be permanently damaged. To avoid
receiver damage and PER degradation, you can use one of the following techniques:
• Separate the omnidirectional antennas by at least 2 ft (0.6 m) to avoid receiver damage or by at least
25 ft (7.6 m) to avoid PER degradation.
Note These distances assume free space path loss and are conservative estimates. Required separation
distances for damage and performance degradation levels in actual deployments are less if
conditions are not non-line-of-sight.
•
Reduce the configured transmit power to the minimum level.
• Use directional antennas, and keep them away from each other.
• Cable the radios together using a combination of attenuators, combiners, or splitters to achieve a total
attenuation of at least 60 dB.
For a radiated test bed, the following equation describes the relationships among transmit power, antenna
gain, attenuation, and receiver sensitivity:
txpwr + tx gain + rx gain - [attenuation due to antenna spacing] < max rx input level
Where:
txpwr = Radio transmit power level
tx gain = transmitter antenna gain
rx gain = receiver antenna gain
For a conducted test bed, the following equation describes the relationships among transmit power,
antenna gain, and receiver sensitivity:
txpwr - [attenuation due to coaxial components] < max rx input level
Caution Under no circumstances should you connect the antenna port from one access point to the antenna port
of another access point without using an RF attenuator. If you connect antenna ports, you must not
exceed the maximum survivable receive level of 0 dBm. Never exceed 0 dBm, or damage to the access
point can occur. Using attenuators, combiners, and splitters having a total of at least 60 dB of attenuation
ensures that the receiver is not damaged and that PER performance is not degraded.
Installation Guidelines
Because the access point is a radio device, it is susceptible to common causes of interference that can
reduce throughput and range. Follow these basic guidelines to ensure the best possible performance:
• For information on planning and initially configuring your Cisco Mesh network, refer to the Cisco
Wireless Access Points, Design and Deployment Guide, Release 7.3.
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