Raspberry Pi Zero W external antenna mod

Saturday 04 March 2017

Raspberry Pi Zero W external antenna mod

With the release of the new Raspberry Pi Zero earlier this week we ordered one from The Pi Hut to use with our expansion boards (they all work without any problems) and one from Pimoroni to use with our barcode scanner project.

The new Raspberry Pi Zero W has built in Wi-Fi and so we thought this would be better than the USB dongle which we are using with the barcode scanner.

Upon receiving the new board we noticed that the Raspberry Pi foundation have left a space and jumper pad for a U.FL RF connector to use with an external antenna.

Connector Pads

Connector Pads

We already had a suitable Wi-Fi antenna and so we ordered the U.FL connector and a short coaxial cable assembly from Farnell.

The parts ordered are:

HIROSE(HRS)  U.FL-R-SMT-1(10) and MULTICOMPR-134G7210150CA

On the Raspberry Pi PCB there is a component which appears to be a zero ohm resistor (0201 size 0.6mm x 0.3mm) which links to the pcb antenna or can be turned 45 degrees to link to the U.FL connector bypassing the internal antenna.

Component to rotate

Component to rotate

We carefully removed and rotated the resistor to the U.FL link pad and then soldered the new U.FL connector to the board.

Link rotated and the new U.FL connector fitted.

Link rotated and the new U.FL connector fitted

The connector fitted to the Raspberry Pi Zero W

The connector fitted to the Raspberry Pi Zero W

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.

sudo iwlist wlan0 scan

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.

      Internal Antenna External Antenna
Network Channel Encryption Quality Signal Level (dBm) Quality Signal Level (dBm)
Net1 6 WPA2 26/70 -84 27/70 -83
Home network 13 WPA2 50/70 -60 68/70 -42
Net2 1 WPA2 27/70 -83 37/70 -73
Net3 1 WPA2 27/70 -83 37/70 -73
Net4 6 WPA2 26/70 -84 27/70 -83
Net5 6 off 27/70 -83 30/70 -80
Net6 1 off 31/70 -79 37/70 -73
Net7 11 WPA2 28/70 -82 29/70 -81
Net8 6 WPA2 27/70 -83 26/70 -84
Net9 11 off 28/70 -82 31/70 -79
Net10 1 WPA2 27/70 -83 25/70 -85
Net11 6 off 28/70 -82 23/70 -87
Net12 6 off 26/70 -84 22/70 -88
Net13 6 WPA2 28/70 -82 21/70 -89
Net14 11 WPA2 29/70 -81 32/70 -78
Net15 11 WPA2     14/70 -96
Net16 1 WPA2     30/70 -80
Net17 1 off     30/70 -80

 

Testing the Raspberry Pi Zero W with the built in antenna

Testing the Raspberry Pi Zero W with the built in antenna

Testing the Raspberry Pi Zero W with the external antenna

Testing the Raspberry Pi Zero W with the external antenna

Please note this will invalidate the FCC certification.

The photo below shows the new modified Pi attached to the Barcode scanner project we are working on. The Raspberry Pi Zero W is mounted between the power supply/controller PCB and the touch screen so the onboard antenna would be shielded by both boards.

Barcode scanner pcb