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ESP32-C3 SuperMini ANTENNA MODIFICATION

04/03/2025 · by peterneufeld · in All Articles, ANNEX32, Antennas, ESP32, ESP32 range extender · 52 Comments

Boosting ESP32-C3 SuperMini WiFi: A Simple and Effective Antenna Mod

The ESP32-C3 SuperMini modules are incredibly affordable, costing around €2, and are equipped with a compact SMD antenna. However, this tiny antenna significantly limits the usable WiFi range due to its design. To address this issue with minimal effort, I implemented a simple antenna modification that drastically improved performance.

The Antenna Modification

This modification involves adding a 31 mm length of 1.0 mm silver-plated wire, configured as a quarter-wavelength (λ/4) antenna.<br>The bottom section of the wire is bent into a horizontal loop (approximately 16 mm of the wire length, forming a loop with a diameter of about 8 mm), while the remaining 15 mm section is angled vertically upwards.

I wrapped the circular loop around the shaft of a 5 mm drill and then widened the ends of the loop so that they touch the terminals of the SMD antenna. The SMD antenna effectively completes the wire loop—mechanically at a quarter of its circumference, but electrically as a λ/4 element in parallel with a λ/8 wire.

Solder the new antenna directly to both ends of the original SMD antenna on the ESP32 module. Specifically, solder to the 50 Ohm antenna pin (the left end of the original antenna) and to the other "hot" end of the original antenna. This effectively bypasses the original PCB antenna. Ensuring two good solder joints at both ends of the PCB antenna is crucial. Pay close attention to the position of the wire that goes up from the loop. The old aerial has been left in place as it becomes electrically ineffective in this configuration.

EDIT: Meanwhile, some adaptations of my antenna design have been published in blog posts and YouTube videos. However, some of these adaptations struggle with the TOTAL 31mm length of the antenna wire, leading to suggestions to elongate the vertical section to make the complete antenna a 5/8 lambda radiator. This isn’t very wise if you want the antenna to radiate omnidirectionally and preserve the acceptable mechanical dimensions.

Testing with the WiFi Logger Program

To evaluate the effectiveness of this modification, I used my custom WiFi logger program written for ANNEX32 BASIC. The program compares the signal strength (RSSI) of two ESP32 modules: one unmodified and one with the new antenna.

The live signal data was displayed in real-time on a tablet browser.

Both modules were mounted side by side on a portable power bank to ensure identical testing conditions while moving around various locations near an access point (AP).

Results

The signal strength curves recorded with the WiFi Logger program consistently demonstrated a clear superiority of the modified module over the original. Under the testing conditions, where both modules were mounted side-by-side on a power bank and moved around various locations near an access point (AP), the modified antenna consistently provided higher signal levels.

On average, the improvement in signal strength was at least approximately 6dB . In many cases, particularly at the edges of the WiFi signal range or in environments with more interference, the improvement even exceeded 10dB . This difference in signal strength had a significant impact on the stability of the connection. The modified module maintained a stable connection while the unmodified module was more prone to disconnections or performance degradation.

To illustrate the results:

In close proximity to the Access Point: The improvement was often 6 dB to 8 dB, resulting in a more stable and less fluctuating connection.

At a greater distance from the Access Point: The improvement often reached 10 dB or more, making the difference between a usable and unusable connection. The modified module could receive and send data, while the unmodified module could not establish a connection or suffered from extremely slow data transfer.

In environments with obstacles (e.g., walls): The modified antenna showed better penetration and provided a more stable connection compared to the unmodified module, which struggled to maintain the signal.

These improvements led to a significantly extended WiFi range. Theoretically, every 6 dB increase in signal strength corresponds to a doubling of the range. In practice, this means that the modified ESP32-C3 SuperMini module was able to establish a reliable WiFi connection in areas where the unmodified module had no or only a very unstable connection.

Observations

The original SMD antenna CrossAir CA-C03 placed at the ESP32-C3 SuperMini module, due to its...