sector antenas like this might have troubles reaching up to 5km.
free path loss:
(3 .. 5) km = (116 .. 121) dBm
for SXT SA5 as server/AP with 54MBit rate, in specified distance there will be only: 27 + 16 - (116 .. 121) = - (73 .. 78) dBm
then it depends on client device what kind of antena it has. For example using LHG 5 as client/CPE means additional 24 dBi gain.
RX power will be - (73 .. 78) + 24 = - (49 .. 54) dBm
With this rate, LHG will have -80 dBm sensitivity and link should work. With higher rate, it is not gonna be reliable. If there is interference around, it is also not gonna work very well.
However, if he use CPE with less gain, it is gonna be way harder.