@小杨
Alright then, it looks like the config file is not working on 4.1.5 with Android running 6.0.1.
I used Bin4ry's deejayeye-modder for 4.1.3 and can get a strong connection for 2km or so. Now with 4.1.5 without the mods and with config file that goes down to like 1KM.
I was flying within the same area, and the same time of day.