This one is old news but I found this now.
Link : sticked in mikrotik wireless forums and http://www.engadget.com/world-record-5ghz-wifi-189-miles/
304km is very good result. Congratulations!
While I aiming stable links of about 1 to 3 km this looks impossible to reach for me.
Interesting is – home made antennas – they used 1.2 meter dishes and homemade feeders for reflectors.
Here is hardware used : “a pair of Ubiquiti XR5, and a pair of handmade antenna (120cm satellite dish for the surface, and a bronze ball-bearing extracted from a bus).” After connection cards power is lowered to 10mW !
The link is possible due some of the features of the Mikrotik software.
As constructor of the antennas is mentioned Paolo IK0PCJ – You can find a link to his site in my previous post.
Look like that the smaller feeder is used. There are NO dimensions on the forum so I do not put links to it.
This look simple enough so if You know the frequency – You will be able to calculate and build one of these.