Thanks for the answers. Now I have measured the exact distance, and it turned out to be 1 km. I've tried the calculator linked above, but it"s quite difficult for me, and maybe I entered something wrong..
Could someone please do the calculations for me?
Antennas: prime focus parabolic, 44cm, 24 dBi gain
Cables: U.FL connector on R52 card -> U.FL-N pigtail 15 cm -> N connector -> 5 meters of H-155 cable (attenuation: 0,6dBi/m ) -> N connector on the antenna
Distance: 1 km, clear line of sight, one antenna is on the top of a 10-floor building, other is on the roof of a 2 floor buildng.
The question is: what TX power should I set on the TX radios?
I'd like to set up everything before installation, I hired the local satellite guys to install the antenna mast, and the dish on the 2-floor building, because I don't have the tools and experience to do it alone, and also afraid of falling down... However, they're TV guys, don't know anything about WiFi. I thought I set both ends to alignment-only mode, so they only have to listen to the beeps to align the antenna on the roof