USB-C port interferes with Wifi - Macbook Pro 2018 Touchbar

Why do I have difficulty with Wi-Fi or Bluetooth devices when USB 3 devices are attached to my computer?

Some USB 3 devices can generate radio frequency interference that can cause Wi-Fi and Bluetooth devices operating in the 2.4GHz band to have issues communicating with your computer. Here are some tips to avoid this issue:

• If your USB device has a cable long enough that you can move the device, place it away from your Mac—and make sure not to place it behind your Mac, or near the hinge of its display. The antennas for Wi-Fi and Bluetooth are located there, and USB 3 devices placed there might interfere with your wireless connections.
• If you're using adapters or dongles on a Mac computer with Thunderbolt 3 (USB-C) ports, plug them into the front port on the left side of your Mac, or into the ports on the right side (if your computer has them). These ports are the farthest away from the antennas, making interference less likely.
• To avoid interference on the 2.4GHz band using Wi-Fi, try using the 5GHz band instead. You can change this on your wireless base station. Bluetooth always uses 2.4GHz, so this alternative isn't available for Bluetooth.

from:

Using USB devices with your Mac - Apple Support

also, any of these items may be involved:

• Power Adapter cable recall

Apple USB-C Charge Cable Replacement Program - Apple Support

• firmware update for the Apple Multi-Port display adapters (specifically to reduce interference).

About the USB-C Multiport Adapter Update 1.0 - Apple Support• LG-display recall -- to address Wi-Fi interference so severe, it knocks the Router off the air if too near the Router.

https://9to5mac.com/2017/02/03/lg-fixes-wifi-interference-problems-with-ultrafin e-usb-c-5k-display-new-units-unaffected/

http://support.apple.com/kb/HT5172#15

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