How far are you trying to go.  The sector antenna is overkill for what you need unless your building out for a wireless service provider network.  Plus you have to get a Rocket radio to go with it so they get pricey.  Nanostations or Nanobeams can go several miles and are much smaller and easier to work with.  If you have totally clear line of sight go with 5ghz as it is a less crowded band.  Use 2.4 if you have a FEW trees to deal with.

For what it's worth.....I have two sector antennas on a grain bin that are access points for nanobeams and cameras that are at irrigation wells.  The cameras monitor the well's drip oil so I don't have to go to the pivot on a daily basis.  Two of them are about 2.5 miles away and work perfectly.  The biggest challenge is getting enough height to keep the fresnel zone above the corn.  If I could get then stations at the wells above 10 feet high I could reach out much further.