This article is a statement from Cisco Technical Assistance Center support to clarify the support conditions of 3rd party antennas on Cisco Aironet and Catalyst Access Points.
If a customer/partner wants to use use non-Cisco (third party) antennas with Cisco Wireless LAN equipment then:
It is up to them (their installer/integrator) to ensure that the system is compliant with all regulatory requirements.
Cisco TAC is not responsible for troubleshooting their RF performance; that is the responsibility of the customer/partner and their installer/integrator.
Cisco TAC does support the Cisco brand Access Points' hardware and software.
If the customer believes that the Access Points' wireless performance is not what it should be and they would like TAC support, they must replace the unsupported third party antennas with Cisco brand antennas and validate the performance
Official statement on Cisco support of third-party components (technology generic):
When a customer reports a product fault or defect and Cisco believes the fault or defect can be traced to the use of third-party memory products, cables, GBIC's, filters, or other non-Cisco components by a customer or reseller, then, at Cisco's discretion, Cisco may withhold support under warranty or a Cisco support program such as SMART Net Total care™ service.
Cisco does not support any third-party antennas. RF connectivity and compliance of third party antennas is the user’s responsibility. Cisco does not recommend any third-party antennas, and Cisco Technical Assistance Center will not be able to provide any support for third-party antennas. Cisco’s FCC Part 15 compliance is only guaranteed with Cisco antennas or antennas that are of the same design and gain as Cisco antennas.