I have a project to build a short range link between two buildings about 800-900 meters (half a mile) away from each other using two 1250 in 802.11n mode. the design account for 2 external antennas on each side, 100 ft interconnects & lightning fuses. My question is related to antenna section in 2.4ghz and 5ghz. I believe 2.4ghz is a no brainer with 10 dBi Yagi antenna AIR-ANT2410Y-R, but I have not clue for 5ghz operation, can anyone enlighten me?