The Raspberry Pi Zero 2 W is the latest board in the Raspberry Pi Zero family, with a 1GHz quad-core processor and 512MB SDRAM and was released on the 28th October 2021.
When the Raspberry Pi Zero W was released in 2017 we modified the board with an external antenna connector which was a very popular blog post and with the announcement of the new Raspberry Pi Zero 2 W version we tried to order the new board and try the same modification again.
Initially there was very limited stock available and we were not able to order the new board until the end of November.
As with the previous version the Raspberry Pi foundation have left a PCB footprint and jumper pads for a U.FL RF connector to use with an external antenna but the new Raspberry Pi Zero 2 W has a solid PCB trance going to the built in antenna compared to the 0201 link used on the previous board.
We ordered a suitable Wi-Fi antenna, U.FL connector and a short coaxial cable assembly from Farnell.
The parts ordered are: Swivel Type Antenna, U.FL-R-SMT-1 and JF1R6-CR3-4I - RF / Coaxial Cable Assembly.
Before starting the modification we used the following command to obtain a list of available Wi-Fi networks and their signal strengths and save to a text file.
sudo iwlist wlan0 scan | egrep "Cell|ESSID|Signal|Rates" > scanlist.txt
Adding the U.FL connector
Please note this modification is done at your own risk and will invalidate any warranty and RF compliance.
First, we need to cut the track which goes to the PCB antenna. We used a Dremel with an engraving tip, but this could also be cut using a sharp knife to scrape away the copper trance. Take care not to cut either side of the track into the ground plane otherwise you could cause a short circuit on the antenna circuit. We cleaned the resulting dust away with a cotton swab.
Next we applied solder to the centre pad for the U.FL connector and to the two small pads to fit a zero ohm resistor (0201 size 0.6mm x 0.3mm). We did not have a suitable 0201 resistor so we later created a solder bridge with the soldering iron and a small amount of solder.
The U.FL connector was then fitted in place and held with tweezers and heat applied using a needle tip soldering iron to heat the centre pad.
The outer pads are then soldered to the ground plane on the PCB. We tried this with the small soldering iron tip but found that it did not have enough thermal mass to heat the board so we changed to a 2mm soldering iron tip to heat and flow the solder fully.
With the connector fitted and the solder link complete we cleaned the area with a cotton swab and alcohol to remove any solder flux.
Testing the new antenna
To test the new external antenna compared to the built in PCB antenna we used the following command to scan for available Wi-Fi networks and saved to a new text file.
sudo iwlist wlan0 scan | egrep "Cell|ESSID|Signal|Rates" > scanlist-result.txt
The testing was performed in the same location as before with the new antenna held vertical. The signal strength would improve further if the antenna was fitted to a metal ground plane.
The following table shows a list of networks found and their signal strength and quality readings. Most networks showed an improvement with the new external antenna and our home network had a much greater signal strength.
A smaller Signal Level (dBm) is better.
||Internal Antenna Quality
||Internal Antenna Signal Level (dBm)
||External Antenna Quality
||External Antenna Signal Level (dBm)
|Nearby Network 1
|Nearby Network 2
|Nearby Network 3
With the PCB antenna the Raspberry Pi Zero 2 W detected 4 available Wi-Fi networks. After installing the new external antenna, it detected 14 Wi-Fi networks.
Why not leave the track and remove the component on the antenna?
There have been several comments posted on various blogs which have asked why we didn’t just remove the first “resistor” on the antenna trace. The component is a capacitor which measures 6.5pF on an LCR meter and is part of the tuned PCB antenna.
Removing the capacitor would create an unmatched impedance to the RF driver which could cause problems with the signal integrity.
The small curved track which would be left on the PCB measures approx. 4.3mm which would be resonant at 17.4GHz at quarter wave (7th harmonic), 34GHz at half wave (14th harmonic) and 69.7GHz at full wavelength (29th harmonic). Harmonics are calculated on WiFi 2.4 gigahertz frequency.
10 December 2021 at 6:53 pm
Great post, thanks for risking your Zero 2 W to do this mod!
13 December 2021 at 1:49 pm
Dont destroy the trace, just move the 0 ohm resistor.
13 December 2021 at 2:09 pm
There isnt a zero ohm reisistor on the 2W mode, only on the first gen one.
greetings from Hackaday
13 December 2021 at 2:18 pm
Cool! Do you think this could be done by removing the resistor that appears to be inline with the PCB antenna? I personally would be scared to cut the trace :)
Of course, I'm not sure if this would actually work, RF isn't really my cup of tea.
13 December 2021 at 4:14 pm
Leaving the track's worse than you think. The resonant frequency of the stub needs to be calculated in the propagation speed of the wave (on the board) not free space. It looks like CPWG, which means the effective dielectric constant's probably around 2, meaning it's probably around 70% speed of light. So it's actually more like 12 GHz, or the 5th harmonic.
But if I were doing this I'd probably scratch the trace to generate a pad so that I could rotate the resistor there if I wanted to.
greetings from Hackaday
14 December 2021 at 12:36 am
Please disregard earlier message, and -1 to me for lack of research. I think I understand now.
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