To attempt to bridge the language gaps here I believe @tuyenpham has TWO antennas for his RAK2247:
- The small iPEX coil antenna (that shipped with the board)
- And a RAK Fibre Glass antenna
When he swaps over to the Fibre Glass antenna, he sees a drop in performance.
First three questions - where are you in the world, what frequency are you using and what is the frequency of the fibre glass antenna (from the label on the antenna) please.
Next two questions: what cable are you using to connect the fibre glass antenna and where is it placed? Pictures would be preferable.
You should see better performance from the properly connected & mounted fibre glass antenna straight away without any changes to the config.
For 5km line of sight, the antenna will need to be at least 2m off the ground - but always preferably above all large buildings in the vicinity - or at the top of them.