I’ve recently bought the MT300A on amazon and it was the internal-antenna version. I’ve noticed that there are uFL connectors on the PCB (contrary to what the store page says…) and I found uFL to SMA connectors on ebay. Would I be able to just plug-in such a connector and add external antennae? Would I have to disconnect the internal antennae in any way?
No. it is not uFL connector. It is for radio calibration. The uFL connector actually as a little different in the middle.
If you want to modify it it, you have to use a solder. Otherwise, just buy the external antenna version.
nikkam
3
Do i have to remove any resistor or just to connect the external antenna?
sboger
4
Yes. Notice the C44 capacitor in this image of the CON2 antenna connector. Above and to the left of it are two empty pads. You need to un-solder the C44 capacitor and completely move it to those two pads and re-solder. Repeat for CON1.

This will be a fun project. I’ll write back with results.