alzhao
2
If you check the wifi module on MiFi, you will find uFL connector. If you want to connect external antenna, you need to remove one resistor R57 (the one nearest to the uFL on the baseboard) and then you can connect external antenna.
But I suggest you try the internal antenna first. 100meters maybe a problem for external antenna as well, as this is related to the hotspot as well.
BTW, please try firmware v2.23-3 from GL.iNet download center
Now you can config multiple WAN like repeater and modem at the same time. Repeater will have priority. If repeater is not connected it will use modem. The repeater will connect automatically if in range.