Intermittent wifi problem driving me bonkers!

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/

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You might try changing the channel your wifi router is setup to use.

Your neighbor may be using the same channel you are and it's causing interference.

Also if you recently moved your computer or wifi router, it could be due to electromagnetic interference.

Try moving the equipment further away from power lines in your walls or away from other electronic equipment.

Hold down the Option key while you click on the Wi-Fi icon on the MenuBar. You get a snapshot like this one:

please post a screen shot or information about:

PHY Mode and Channel

RSSI or signal or signal/Noise

Transmit Rate

MCS Index

and very important... how many Networks do you see?

You have good signal strength and few other around as strong as yours. You are using two antennas to get 867Mbits/sec with a complex 256-pattern modulation scheme.

Do you have any other electronic equipment within about five feet of your Router?

On that same Option-Wi-Fi menu, choose Wireless Diagnostics and choose "Monitor" your connection. then just leave the window open in the background. If something happens, you will get an alert.

Hello lucasm220,

What kind of machine do you have? What year? There have been reports that the many required dongles for the newer USB-C MacBook Pros will interfere with your WiFi. The solution is to either buy a different dongle, move the dongle to a different port, remove the dongle, or use a 5 Ghz network. Bluetooth will be similarly affected.