If you are using and NodeMCU or Duet 2 WiFi in a metal box the signal strenght of the WiFi would be quite bad.
So a external antenna is needed. Two options are possible
- Soldering an external antenna to the ESP12F Modul. Tutorial here: https://www.instructables.com/id/External-Antenna-for-ESP8266/
- Replacing the ESP Modul with a ESP07 or ESP07S. The moduls have an external antenna connector. My Adapterboards for RRF and the Duet needs the ESP07S Version.
The trickiest part is the desoldering of the Modul.
- Using and HotAir Station is the "normal" way to do it. Heat the solder points of the ESP up and it comes easily loose
- But not everybody got and hotair station. But there is a way to do it without!:
For the desoldering without hotair you will need:
- Soldering iron
- Copper wire
- Solder wick
- ESP07(S) modul
My inspiration for this comes from this video: https://www.youtube.com/watch?v=CVsmwFAkf7I&t
Step 1 is bending the copper wire like this
Step 2 applying a lot of solder to the wire so it become a giant "solder snake". Then heat everthing out and push the ESP away
Step 3 ESP is now desolderd. Now clean the solderpoints with some solder wick and retin them
Step 4 Place the ESP07(S) on the old solder points. And solder the modul onto the board
Step 5 After soldering the board so not forget to reflash the firmware of the ESP!
Step 6 Finish! You can now use an external antenna with the NodeMCU