Bernie asked 7 months ago
My esp32 devkit board is located in a room full of grounded plumbing so that the wifi signal barely reaches it. How do I improve wifi sensitivity for reception and transmission? Can I attach an external antenna?
In the following question, I am not sure where the zero-ohm resistor is on the internal antenna pad?
Bernie answered 5 months ago
I just found out that an antenna length of 4x the wavelength is not a good thing.
The optimal length is 1x or 1/2x the wavelength. So at 2.43 GHz, the wavelength length is 30 / 2.43 = 12.3 cm.
So I soldered an antenna with a 1x wavelength (see below), and it gave me another 16 dB of signal strength, for a total of 20 dB which is 100x stronger.
The direction of the antenna is important too. First point the antenna to the source of the WiFi signal. Then in any direction, bend the antenna at its starting point 90 degrees.
In my case, the RSS strength reported by WiFi.RSSI() went from -88 to -68 dB which has made a great difference.
Sara Santos Staff answered 7 months ago
Hi.
Yes. You can use an external antenna.
Are you using an ESP32-CAM? Then, this is the guide you’re looking for: https://randomnerdtutorials.com/esp32-cam-connect-external-antenna/
Regards,
Sara
Bernie answered 7 months ago
Not for ESP32-CAM. Just a DOIT Devkit V1 without an antenna jack.
There must be a way to improve reception/transmission?
Do You know what Steve Mercer means by “removing zero ohm resistor”?
Sara Santos Staff answered 7 months ago
Hi again.
The zero ohm resistor is on the ESP32-CAM.
So, it doesn’t apply to your case.
If you’re using an ESP32 DOIT board, it is not that easy, but I found this tutorial that shows how to solder an external antenna: https://community.home-assistant.io/t/how-to-add-an-external-antenna-to-an-esp-board/131601
There are also ESP32 board models that already come with an antenna connector, so you just need to plug the antenna. Those might be a better option if you don’t want to solder.
Regards,
Sara
Bernie answered 7 months ago
See update above. The optimal antenna length is 1x or 1/2x wavelength for 20 to 30 dB improvement..
So I implemented Sara’s link. What I did was to solder a wire to the RF output of the module, as my 38 pin ESP32 did not have an antenna jack. I experimented quite a bit and concluded that there is no need to extend the ground wire. Looking at the built in antenna, you see what appears to be a ground copper trace that loops back to the RF output. Then the micro built-in antenna takes off from where the RF joins ground. So I cut the ground trace and the trace to the built-in antenna. See diagram below.
Bernie
Sara Santos Staff answered 7 months ago
Hi.
Thanks for your feedback.
I’m glad it worked somehow in improving the signal, even though not that much.
Regards,
Sara
Sara Santos Staff answered 5 months ago
That’s great.
Thanks for sharing those findings.
Regards,
Sara
Bernie answered 5 months ago
This image shows the upgrade more clearly:
https://drive.google.com/file/d/1Zaf2fx_l-3bxhmR5DSItQ7FHSPjiEX6s/view?usp=drive_link
Sara Santos Staff answered 5 months ago
To share a picture, upload it to Google Drive, or imgur and then share a link to the file.
Regards,
Sara