I went from three antennas 5dbi three 12dBi antennas on my TP-Link router. I have observed absolutely no improvement. My backtrack showed even lower figures than before goods on the signal strength. The antenna is a bad bill and too thin to imagine that it can send 12dBi according to the manufacturing agreements wifi antennas.
In short, I replaced these antennas by official 8dbi TP-Link. It is the day and night despite the 4dBi less.