Whenever connecting my Western Digital WD Passport Ultra drive via USB to perform backups on Windows 10, my Wi-Fi connection went for a toss and wouldn’t recover for a while even after disconnecting the backup drive. The network connection slowed to a crawl and some web-sites would timeout trying to access them in a browser. Looking at the task manager did not show any task consuming high amounts of CPU or memory or disk or network bandwidth. After some research, I came across some comments indicating that USB 3.0 can interfere with Wi-Fi signals which are in the 2.4 GHz range. This paper describes this problem in more detail. Apparently the best solution is to switch to using Wi-Fi in the 5GHz range if your Wi-Fi router supports it. Alternate approaches are to somehow shield the USB cable and connector so the electrical noise doesn’t spread out or adjust the Wi-Fi dongle/antenna so it isn’t too close to the drive and it’s cabling. The linked paper describes various tests done with shielding and managing Wi-Fi dongle placement.
http://www.intel.it/content/dam/www/public/us/en/documents/white-papers/usb3-frequency-interference-paper.pdf
