With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
bsnAPIfPhyAntennaType
bsn AP If Physical Antenna Type
1.3.6.1.4.1.14179.2.2.2.1.8
This attribute specified if the Antenna currently used by AP Radio is internal or external. For 802.11a the antenna is always internal. For 802.11b you can set antenna type to be external or internal.
Back to AIRESPACE-WIRELESS-MIB MIB page.
IPHost Network monitor allows you to monitor bsnAPIfPhyAntennaType on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco multiplexers right now.