802.11n antennas setup

hello guys.

im currently running a mikrotic based point to mutli point network over distances of upto 10km. we now want to migrate to 802.11n 5.8ghz. i have bought R52n cards for my network.

my problem is i cant seem to find an antenna that i can use. some have suggested that i use 2 separate antennas (1 horizontal,1 vetical) but i cannot find any info/setup manuals on this.

all help welcome.

Thanks in advance