Sometimes you need an external antenna for the ESP8266.
For example you want to install the ESP into a metall box for some outside or other applications which is installed in cases. Or you only need a more signal strength. Therefor you need to install a WLAN Antenna connections. But most of the ESP don´t have a small microcoax or similar. So i buyed some WLAN Antennas for very small amount at the usual shop like "Ebay Bangood Ali etc."
So I started to modify and i want to share a small instructable for modification. For in this case a WEMOS D1 mini.
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Step 1: Prepare Wemos D1 Board
First prepare the Wemos Mainboard by cutting off some connections as shown in the pcutre. Be sure that the connection is cut through to get a better signal with the external antenna otherwise the signal doesn´t get better but worsst
Step 2: Soldering the The Cable to the PCB Tracks
After preparations for the cable and the board sold it together like described at the picture. Shield / Screen to ground and the centre-wire to the Antenna track.
Step 3: Check If There Is Not Short Between the Antenna Conection
Please measure to be enshure that there is no short between center and screen.
Step 4: Fix the Antenna Cable
Fix the antenna cable with some hot glue to protect the cable form destroying the connection with bending.
Step 5: Checking for the Success
I uploaded a program to two identical ESP8266 one with our hack one without at the same position. (6m to Access Point). Signal is printed with the internal Arduino instruction Serial.print(WiFi.RSSI()); as you can see the benefit is about 14-16dbm. with a +3dBi antenna. Now you can apply every antennta as you want.