Here's the part 15 wifi spectrum as seen from a directional antenna at one of our sites. The strong signal at 5800 is some part of Towson University's wifi network, about a mile away, directly in the path of this dish:
Operating in Part 15 under the Unlicensed National Information Infrastructure (U-NII) allows for outdoor use and user-installable antennas in much of the spectrum above. Operating under amateur rules allows for greater power, and some unlocked/international gear can be used above 5825 MHz.
We have two dishes very close to each other, pointing 120 degrees apart. One is a 25dB ~18" dish:
And the other is a 30dB ~30" dish:
The 25dB dish has one small cluster of trees and a 2.4 mile run, but you can see one building from the other. That's why its signal is -65 with a noise floor of -90. The link is 240 mbps bi-directional, but with 100 mbps ethernet as the limiting factor we can get sustained transfers of 9 megaBYTES per second.
The 30dB dish is aimed at a site 9.4 miles away, with a ridge and a cluster of trees in the middle. We're pretty sure we can aim them better to get the signal into the low 70s, but through the recent snow and ice storms the signal remained constant, and the bandwidth remained above 100 Mbps. Sustained transfers through this link are 8 megaBYTES per second.