MacBook, USB-C Dongle and WiFi Interference

May 2019 | Dios Kurniawan

Ever since I moved my study desk to a different room at home, I had been experiencing very slow wifi connection on my MacBook. This happened only when I attached an external monitor via DisplayPort-to-USB-C converter. Wifi shows it is still connected, but speed can suddenly drop to near-zero rate.

Each time I unplugged the dongle, the problem disappeared. The USB-C dongle seems to generate some signal interference right into MacBook’s wifi antenna.

After hours of frustration, I found out the solution on an internet forum: aluminium foil. It might sound silly, but aluminium blocks radio signal pretty well. Wrap the USB-C dongle with few layers of aluminium foil and the wifi problem is gone.

DisplayPort to USB-C / Thunderbolt 3 converter, wrapped in aluminium foil

Interesting that this only happens on MacBook. Other devices do not suffer from the same symptom.