Cisco Aironet 1550 Series Getting Started Manual page 31

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.
• Reduce the configured transmit power to the minimum level.
• 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 antenna gain + rx ant 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 RF Attenuator components] < max rx input level
(0 dbm)
Under no circumstances should you connect the antenna port from one access point to the
Caution
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 PER performance is not degraded.
31