ESP32-C3 SuperMini ANTENNA MODIFICATION

[PeterN]

### Improving WiFi Performance on ESP32-C3 SuperMini Modules with a Simple Antenna Modification

The ESP32-C3 SuperMini modules are incredibly affordable, costing around €2, and are equipped with a compact PCB 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
The modification involves attaching a 31mm piece of silver-plated 1mm wire, designed as a quarter-wavelength (lambda/4) antenna. The lower part of the wire is bent into a horizontal loop (about 5mm in diameter), and the remaining section is angled vertically.

This new antenna is soldered directly to the 50 Ohm antenna pin of the ESP32 module (= left end of the original antenna) and also to the second right end of the old antenna. This effectively bypasses the original PCB antenna. The TWO solder joints of the new antenna wire at both ends of the original PCB antenna are electrically essential. Also note the placement of the long angled end of the wire. The old aerial has been left in place as it becomes electrically ineffective in this configuration.

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

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#### Results
The recorded signal strength curves clearly demonstrated that the modified module consistently outperformed the original. The modified antenna provided signal levels at least approximately **6dB** better, often exceeding **10dB** in certain conditions.
This improvement resulted in significantly more stable connections and extended range, as every 6db more doubles the theoretical range.

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#### Observations
The original PCB antenna, due to its small size, actually being a compactified quarter-wave-wire, was inherently inefficient at transmitting and receiving RF energy. In contrast, the new non-shortened quarter-wavelength antenna produced a much stronger and more consistent field, likely due to its combination of horizontal and vertical elements, which minimized null points in its radiation pattern. Notably, removing the original PCB antenna was unnecessary as it no longer contributed to performance in this setup.

#### Conclusion
This simple yet effective modification highlights how inexpensive hardware can achieve substantial performance improvements with basic adjustments. By mounting a well-designed wire antenna, even budget ESP32-C3 modules can achieve reliable WiFi connectivity over greater distances.


#### The utilized test program:

ATTENTION! I used ANNEX32 V1.70.2 for the ESP32-C3 and not the current V1.70.5 as there are issues with WGetASYNC in the later versions.
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EDIT:
CiccioCB ist still working to find the memory leak problem of versions 1.70.3 to 1.70.5 for the 1core ESP32-C3. He gave a hint to overcome the issue by inserting the command line r=PING(“ “) as a workaround.
I have updated the callback routine accordingly.

Code: [Local Link Removed for Guests]

'######## WIFI-GRAPH-LOGGER ####################################
' This program compares the WiFi signal strengths (RSSI) of two ESP32 modules.
' It aims to graphically display the impact of different antennas on signal quality.
'
' - Module 1 (local): Displays its own signal strength to the Access Point (AP).
' - Module 2 (remote): Sends its signal strength to Module 1.
' Operation modes:
' RX = 1: This module (local) regularly sends HTTP requests to the remote module.
' TX = 1: This module (remote) responds to HTTP requests with its signal strength.
' Author: Peter Neufeld (peter.neufeld@gmx.de, 03/2025)

' Configuration for the local module (ESP32 Module 1):
RX        = 1   ' This module sends requests to the remote module.
TX        = 0   ' This module does not respond to requests.
' Configuration for the remote module (ESP32 Module 2):
'RX       = 0   ' This module does not send requests.
'TX       = 1   ' This module responds to requests.

REMOTE_IP$ = "192.168.0.134" ' IP address of the remote module (Module 2)

X_Num      = 100 ' Number of measurements to display in the graph.
WIFI_REMOTE$  = "" ' Stores the received RSSI values from the remote module.

'onhtmlreload: Triggered when the webpage is reloaded.
onhtmlreload  WEBPAGE
gosub         WEBPAGE

' Enables URL handler for TX mode:
IF TX = 1 onurlmessage RETURN_WIFI_STRING

' Enables asynchronous HTTP requests in RX mode:
IF RX = 1 onwgetasync RECEIVE_REMOTE_STRING

' Timer to regularly measure local signal strength:
timer0 500, LOG_MY_WIFI_CONNECTION

' Timer to regularly query remote signal strength:
IF RX = 1 timer1 1000, GET_REMOTE_WIFI_LOG_STRING

WAIT

'###############################################################
LOG_MY_WIFI_CONNECTION:
' Measures local WiFi signal strength and stores it in WIFI_LOCAL$.

w=0
for i = 1 to 50
    w = wifi.rssi + w ' Accumulates RSSI values for averaging.
next i
w = W / (i-1)   ' Calculates the average RSSI value.

WIFI_LOCAL$ = trim$(WIFI_LOCAL$ + " " + str$(wifi.rssi,"%2.1f")) 
c = word.count(WIFI_LOCAL$, " ") ' Counts stored values.
p = instr(1, WIFI_LOCAL$, " ")   ' Finds the first value in the string.
p = len(WIFI_LOCAL$) - p         ' Calculates the length of remaining values.

If c > X_Num then WIFI_LOCAL$ = right$(WIFI_LOCAL$, p) ' Limits the number of values.

' Updates the graph with local values:
jscall |traceme(0,"| + WIFI_LOCAL$ + |");|
' Updates the graph with remote values if available:
if WIFI_REMOTE$ <> "" jscall |traceme(1,"| + WIFI_REMOTE$ + |");|

return

'###############################################################
RETURN_WIFI_STRING:
' Returns local RSSI values as a response to an HTTP request.
URLMSGRETURN WIFI_LOCAL$
return

'###############################################################
GET_REMOTE_WIFI_LOG_STRING:
' Sends an HTTP request to the remote module to query its RSSI values.
wgetasync ("http://" + REMOTE_IP$ + "/msg?x=1")
return

'###############################################################
RECEIVE_REMOTE_STRING:
R = PING(“ “) ‘This will overcome a memory leak issue in V1.70.3 to V1.70.5
' Receives and stores the RSSI values from the remote module.
WIFI_REMOTE$ = WGETRESULT$
return

'###############################################################
WEBPAGE:
' Creates and loads the HTML page with the graph to display RSSI values.
cls
jsexternal "/xy.min.js" ' Loads external JavaScript library for graphs.
cnt = 0
a$ = ""
a$ = a$ + |<p>WiFi Graph for two ESP32 modules:<br>|
a$ = a$ + |GREEN: With additional antenna<br>RED: With standard antenna|
a$ = a$ + |</p><canvas id="canvas1" width="800" height="400"></canvas>|
html a$
pause 500 
A$ = ""
A$ = A$ + |var datasets = [|
A$ = A$ + |  {|
A$ = A$ + |    lineColor : 'rgba(20,100,100,1)',|
A$ = A$ + |    pointColor : 'rgba(20,20,20,1)',|
A$ = A$ + |    pointStrokeColor : '#fff',|
A$ = A$ + |    data : []|
A$ = A$ + |  },|
A$ = A$ + |  {|
A$ = A$ + |    lineColor : 'rgba(151,30,0,1)',|
A$ = A$ + |    pointColor : 'rgba(151,80,0,1)',|
A$ = A$ + |    pointStrokeColor : '#fff',|
A$ = A$ + |    data : []|
A$ = A$ + |  }|
A$ = A$ + |];|
A$ = A$ + |var ctx2 = document.getElementById('canvas1').getContext('2d');|
A$ = A$ + ||
A$ = A$ + |var xy = new Xy(ctx2, {rangeX:[0,|+ STR$(X_Num)+ |], rangeY:[-80,-35]|
A$ = A$ + |, smooth:0.05, pointCircleRadius:2, pointStrokeWidth:1 });|
A$ = A$ + ||
A$ = A$ + |function traceme(set, data){|
A$ = A$ + |  var s = data.split(" ");|
A$ = A$ + |  for (var i=0; i<s.length; i++) {|
A$ = A$ + |    datasets[set].data[i] = [i, s[i]];|
A$ = A$ + |  }|
A$ = A$ + |  xy.draw(datasets);|
A$ = A$ + |}|
jscript A$
A$ = "" ' Frees memory.
return

[lyizb]

Excellent. Any idea of comparative distances for reliable transmission at a given baud rate?

Also: where does one get silver-coated copper wire?

[botman]

It looks like a piece of a paperclip to me.
I have been known to use paperclip wire before.

[PeterN]

Excellent. Any idea of comparative distances for reliable transmission at a given baud rate?

Also: where does one get silver-coated copper wire?

The effect on the possible distances is difficult to estimate as it depends heavily on the materials in between. BUT: Every 6db more doubles the range. And I always see more than 6dB here.
The built-in print antenna seems to be a very poor solution.

Any copper wire or tinned switching wire will do the job with no measurable difference. However, the non-smaller diameter and the correct length is more important.
You can find these silver-plated 1.0mm wires easily at a craft shop or on Amazon https://amzn.eu/d/8mI6BqK

[PeterN]

It looks like a piece of a paperclip to me.
I have been known to use paperclip wire before.

Will also work from a purely electrical point of view. However, there may be problems soldering it accurately and cleanly at the TWO necessary contact points.

[RonS]

good morning

I once learned: High-frequency waves run and spread out on the surface of the materials, so silvering can be an improvement.

Ron

[BeanieBots]

It looks like a piece of a paperclip to me.
I have been known to use paperclip wire before.

Will also work from a purely electrical point of view. However, there may be problems soldering it accurately and cleanly at the TWO necessary contact points.

Accuracy was at the back of my mind. How critical are the dimensions?
Would this work for 1/2 or even full wave with presumeably even longer range. Maybe add ground plane??
For silver plated wire, raid your Wife's/Girlfrend's jewellery box

[PeterN]

It looks like a piece of a paperclip to me.
I have been known to use paperclip wire before.

Will also work from a purely electrical point of view. However, there may be problems soldering it accurately and cleanly at the TWO necessary contact points.

Accuracy was at the back of my mind. How critical are the dimensions?
Would this work for 1/2 or even full wave with presumeably even longer range. Maybe add ground plane??
For silver plated wire, raid your Wife's/Girlfrend's jewellery box

Hi Chris,
I’m glad to hear from you again! I was worried that your work in the kitchen might have forced you to take a little holiday
The dimensions are indeed critical regarding the length and wire diameter, as these factors influence the optimal working frequency.
The quarter-wave antenna has an appropriate 50 Ohms impedance at one end and is high-impedance at the other. A half-wave dipole, on the other hand, would be high-impedance at both ends, leading to mismatching.
It was indeed much more interesting to preserve the omnidirectionality of the radiation pattern. This can be achieved through the horizontal and vertical parts of this very simple antenna design.
All other antenna constructions may provide better gain, but this gain would come at the cost of a radiation pattern that concentrates the field in specific directions.
And to be clear: the original aerial is more of a power destroyer than a radiating element.

[BeanieBots]

Thanks for the explanation. Proves my rf knowledge is insufficient (or lost)
Lack of on-line activity is/was due to many factors. The worst being the death of my PC
Lost tons of work despite good backup regime and then all that installing of software and configuring to get things the way you like them
Up and running again now but still feeling the pain, thanks for asking.

[Oli]

please make a comparative measurement with my 2 conversions, that would help a lot
Oli

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