After working on my pond control project, I wanted to be able to increase the range of some M5Stack ATOM Lite modules. These modules are ESP32 based and come in a tiny form-factor.
They open easy enough after removing the sticker on the back and then squeezing the clam-shell case. Only 3 parts make up the module – case halves and the PCB inside.
Flipping over the PCB shows the 3D antenna connected to a capacitor-inductor network and the LNA pin on the ESP32-Pico chip.
The sheet-metal antenna is attached at 4 points – one top left, one top right (obscured) and the two bottom right in the foreground. With a little soldering and flux cleanup, the antenna is removed. I used a quick-clamp as a poor-mans PCB holder.
The left-hand pad is the LNA pin, and the right is a ground pad. The two upper pads are not connected to any trace I could find.
The idea is to get the antenna out the side of the case without interfering with the reset button, and also not coming out the bottom or rear (it would prevent the module from being used in the many modules – e.g. the PoE kit). I drilled a small hole in the case.
I cut back the end of a SMA pigtail connector, and tinned the ends.
I threaded the pigtail through the hole, and soldered the centre pin to the left pad, and the outer shield to the right ground pad.
Closing up the unit, I was ready to test
Before starting the internal antenna removal, I ran a simple sketch to list found AP’s. With the internal antenna, a maximum of 8 networks were discovered. With the external antenna, a maximum of 12 networks were found.
This isn’t the most scientific, but gives an idea of the improvement. I also listed the RSSI along with the AP name, and compared the two. The AP I picked was one that I had configured in the garden with 2 walls between.
The red – external – line clearly shows an improvement over the internal antenna.
The final step will be to add a small amount of epoxy to the antenna penetration in the side of the case for mechanical strength. Quick project done.