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Cisco Aironet 1552 Series for Hazardous Locations Installation Guide
Chapter 2 Before You Begin
Avoiding Damage to Radios in a Testing Environment
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.
Additional Considerations for Hazardous Locations
This section describes special considerations for preparing the 1552H, 1552SA/1552SD and 1552WU
access points for installation in Class I, Division 2/Zone 2 hazardous locations.
Note
This document does not provide specific procedures for installing conduit. You must ensure that your
installation techniques and procedures comply with Class I, Division 2/Zone 2 hazardous location
installation regulations for your geographic location.
