@MikroTik: all the hardware pages have links to this PDF: https://i.mt.lv/routerboard/files/anten ... 123306.pdf
Which has the estimated distance when choosing hardware for PtP links... problem is, there isn't a PDF for 2.4GHz gear....

Depends on your country and your allowed EIRP

Look for a *link budget calculator*.

Height above average terrain is very important because of the curvature of the earth. Even under the best conditions, with high gain antennas, etc, an antenna held at the height of a human hand held up as high as it can hold a hand held transmitter, will only be line of sight with a similar hand held transmitter for a very few kilometers. (This is assuming the surface of the earth was perfectly flat, which of course it isn't.)

I have a friend who was able to get and maintain a 40 km wifi link over water with a popular Linksys WRT series AP and a home-made corner reflector / Yagi antenna. (probably around 12-14 db gain) Both he and the AP he was connecting to were on mountainsides however quite a long distance above the water. (This was in the Adriatic.)

@MikroTik: all the hardware pages have links to this PDF: https://i.mt.lv/routerboard/files/anten ... 123306.pdf
Which has the estimated distance when choosing hardware for PtP links... problem is, there isn't a PDF for 2.4GHz gear....