I have a customer that wants to use 4.9GHz (it is a public sector client that owns the license) for long range bridging links to avoid current interference issues in the 2.4GHz. In the past, I had heard there was a sw based limitation when using the 1500's for bridging of 2.5 miles for birdge links even though the hardware with the correct antennas should support up to 15 miles in that space. Does anyone have knowledge of or experience with using the 1500's in a long range point-to-point solution that can validate longer range than 2.5 miles?
Maybe this is the limitation you had seen (now removed in version 4.0);
Wireless Mesh User-Configurable Bridge Distance
Historically, wireless mesh bridge links were limited to two miles. In this release (4.0), bridge distance capabilities are expanded. Cisco wireless LAN controllers now support the ability to specify the distance between nodes used for bridging to a remote location. Performance capabilities of the radio and the RF environment determine the actual distances possible between bridges.
4.9-GHz Support for Wireless Mesh
The Cisco Aironet 1500 Series has been approved for use in the 4.9-GHz band in Japan and the United States. In the United States, the 4.9-GHz band is available only to licensed public safety agencies, providing a level of protection from interference from other wireless devices. The Cisco Aironet 1500 Series now supports operating the wireless backhaul on the 4.9 GHz channels for public safety license holders.
From this good doc;
Hope this helps!