ESP32-C3 SuperMini WiFi Range Improved with Simple Antenna Modification

Addressing WiFi Limitations

ESP32-C3 SuperMini modules, priced around €2, come with a compact SMD antenna that restricts their usable WiFi range. This limitation stems from the design of the small antenna.

The Antenna Modification Process

The modification involves adding a 31 mm length of 1.0 mm silver-plated wire, configured as a quarter-wavelength (λ/4) antenna. The wire's bottom section is bent into a horizontal loop (16 mm, 8 mm diameter), with the remaining 15 mm angled vertically upwards. This loop is wrapped around a 5 mm drill shaft, and its ends are widened to touch the terminals of the existing SMD antenna.

The new antenna is soldered directly to both ends of the original SMD antenna on the ESP32 module: to the 50 Ohm antenna pin and the other "hot" end. This effectively bypasses the original PCB antenna, which becomes electrically ineffective. Proper solder joints are crucial, as is the positioning of the vertical wire section.

Performance Evaluation

To assess the modification's effectiveness, a custom WiFi logger program written for ANNEX32 BASIC was used. This program compared the signal strength (RSSI) of an unmodified ESP32 module against one with the new antenna. Live signal data was displayed on a tablet browser.

Results and Impact

Both modules were mounted side-by-side on a portable power bank to ensure identical testing conditions while moving near an access point. The signal strength curves consistently showed that the modified module outperformed the original, demonstrating clear superiority in signal reception under various conditions.