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Cisco IOS Software Configuration Guide for Cisco Aironet Access Points
OL-11350-01
Chapter6 Configuring Radio Settings
Configuring Transmit and Receive Antennas
•Long—A long preamble ensures compatibility between the wireless device and all early models of
Cisco Aironet Wireless LAN Adapters (PC4800 and PC4800A). If these client devices do not
associate to the wireless devices, you should use short preambles.
You cannot configure short or long radio preambles on the 5-GHz radio.
Beginning in privileged EXEC mode, follow these steps to disable short radio preambles:
Short preambles are enabled by default. Use the preamble-short command to enable short preambles if
they are disabled.
Configuring Transmit and Receive Antennas
You can select the antenna the wireless device uses to receive and transmit data. There are three options
for both the receive and the transmit antenna:
•Gain—Sets the resultant antenna gain in dB.
•Diversity—This default setting tells the wireless device to use the antenna that receives the best
signal. If the wireless device has two fixed (non-removable) antennas, you should use this setting
for both receive and transmit.
•Right—If the wireless device has removable antennas and you install a high-gain antenna on the
wireless device's right connector, you should use this setting for both receive and transmit. When
you look at the wireless device's back panel, the right antenna is on the right.
•Left—If the wireless device has removable antennas and you install a high-gain antenna on the
wireless device's left connector, you should use this setting for both receive and transmit. When you
look at the wireless device's back panel, the left antenna is on the left.
Beginning in privileged EXEC mode, follow these steps to select the antennas the wireless device uses
to receive and transmit data:
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 interface dot11radio { 0slot/port } Enter interface configuration mode for the 2.4-GHz radio
interface.
Step3 no preamble-short Disable short preambles and enable long preambles.
Step4 end Return to privileged EXEC mode.
Step5 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 interface dot11radio { 0 | 1slot/port
}
Enter interface configuration mode for the radio interface. The
2.4-GHz radio is radio 0, and the 5-GHz radio is radio 1.