15KM is too long for 5210 to handle.

Replace it with TL-WA7510N and TL-ANT5823B/TL-ANT5830B. You need external antennas at both side. Use rangefinder or telescope or GPS to do the antenna aligment.

Or wait for the new Pharos CPE 510. http://www.tplink.com/common/Spotlight/CPE510.html

CPE 510 seems to be much powerful than the older products. It is supposed to handle 15KM point-to-point link without external antennas. (In fact, CPE510 has no external Interface reserved, so you can save your money for antennas too)


Your screenshot, the wireless calculator, its result is obviously calculated through the Free Space Propagation Model and for theoretical reference only. It has practical reference value.