Avoiding Damage To Radios In A Testing Environment; Antenna Port 3 - Cisco Aironet 1520 Series Hardware Installation Manual

Chapter 2 Mounting Instructions

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 receiver's
maximum receive input level. 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:
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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
Under no circumstances should you connect the antenna port from one access point to the antenna port
Caution
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.
OL-12632-02
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
attenuation of at least 60 dB.
Cisco Aironet 1520 Series Outdoor Mesh Access Point Hardware Installation Guide
Avoiding Damage to Radios in a Testing Environment
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