Using external antenna on DUO


Hi @llcllc21, Sorry for suffering from the bad experience.

  1. Please upload the “Examples > RedBear_Duo > WiFi > ScanNetworks” via Arduino IDE and then check the RSSI strength of each AP. If the RSSI is lower than about -80 dBm even if the Duo is close to the AP, there is something wrong with the antenna. Attaching the result of the scanned AP herein would be good.

  2. Did the problem happen when you were using the chip antenna?



Hi @guohui,
Let me know if I do something wrong:

I uploaded the last firmware, and I checked it out before with blink example and works well, but I cannot see anything by serial monitor, I suppose I should see RSSI through serial monitor but I cannot.

Please let me know What is wrong to see serial monitor.


Did you connect the Duo to computer directly or via RBLink? The Serial in sketch is mapped to the on-board Micro USB comport.

I tried the ScanNetworks example with only adding a 5 seconds delay after Serial.begin(), and everything works fine:

The first discovered AP is much close to me and normally the RSSI is around -45 dBM.


That’s I have:
Scanning available networks…
** Scan Networks **
number of available networks:3
Channel: 3
RSSI: -85
Channel: 1
RSSI: -82
SSID: vodafone3B7A
Channel: 5
RSSI: -92

my internet connection is the first one: -85, I am 5 meters away of router.


For comparison basing the same distance, you can simply detach the external antenna and scan the networks again to see if the external antenna takes effect or not. If the results are almost the same, then there may have hardware issue on the board. Please check if the antenna socket is well soldered.


Does anyone have any direction on how to remove the tiny components to make the external antenna work? I am a software developer and don’t do much pulling components off of boards so I’m looking for direction on the best (easiest) way to remove those components without destroying the duo. Does anyone recommend certain tools to get in and do this?




Hi everyone…i am a new user here. As per my knowledge the Duo does NOT solder the antenna switch on-board, so WiFi.selectAntenna( … ) is not applicable for Duo. It has been documented here15.To use on-board chip antenna, nothing need to be changed. It is used by default when you got the Duo.To use external antenna via the RF connector, you need to remove the components being figured out below.

pcb assembly prototype



I am planning to use a directional wifi antenna so I removed the components mentioned in this thread. However I noticed that a part was different from the previous redbears that I purchased. Is this normal? R25 in schematic.
One more thing is, the matching circuit seems to have 2 capacitors and a resistor. However their units are in Henry ( so they should be inductors) I don’t think this is normal :slight_smile:

Can anyone from redbear please check this?


Hi @riforifo, quote from hardware engineer, the right-side one is from the latest production batch. All of them are inductor. The left one in the middle might be from different supplier. Did you purchase them in the same pack? Also, you can compare the WiFi performance between them.


Hello Guohui,

thanks a lot for the explanation. I didn’t purchase them in the same pack. The left one was a previous duo that I purchased like a year ago. I will try to compare the wifi performance between them.


hi, would like to know if the same method is to be employed with the latest Redbear Duo? In our use case range/sensitivity is extremely important so I guess we have no choice but to go for the external Antenna.

And also would you be able to suggest a good antenna for this board? We are looking at production scale. Thanks once again for demystifying the Antenna connection in the earlier posts.