RFI from USB memory stick. - Page 1
Forum section: electronics / projects

author: calzap
author_rank: Frequent Contributor
timestamp: February 28, 2022, 03:48:15 pm
content: This AM when trying to sign-in to my PC, the wireless mouse (Logitech M275) wasn’t working, and the wireless keyboard (Logitech K345) was flakey. Tried changing battery in the mouse to no avail. Rebooted using the PC power switch. Things didn’t change. Tried unplugging and re-plugging the dongle in the USB slot. Things didn’t change. Still suspecting the dongle (keyboard and mouse unlikely to malfunction simultaneously), I held the keyboard next to the dongle, and it worked fine.Then it dawned. I had plugged-in a USB memory stick (Sandisk Ultra USB 3, 16 GB) next to the dongle just before trying to sign-in. Pulled the memory stick, and everything worked fine. Must be RF from the memory stick that interfered with dongle reception/transmission. I’ve never encountered this phenomenon before. Has anybody else experienced it?Mike in California

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 28, 2022, 03:54:48 pm
content: More likely some kind of denial of the USB chain.Tim

author: calzap
author_rank: Frequent Contributor
timestamp: February 28, 2022, 04:35:15 pm
content: Quote from: T3sl4co1l on February 28, 2022, 03:54:48 pmThen why did the keyboard work when held very close to the dongle? Does a stronger received signal garner more priority in the USB chain?Mike

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 01, 2022, 04:33:50 am
content: No clue.There's no reason for a garden-variety memory stick to cause radio interference. At, what, those would be BT I suppose (2.45GHz)?The next best thing is you've got some hacked stick with a BT "bug" in it or something?Tim

author: Someone
author_rank: Super Contributor
timestamp: March 01, 2022, 05:43:42 am
content: Quote from: T3sl4co1l on March 01, 2022, 04:33:50 amPossibly not interference, but a big chunk of metal right next to the tiny RF dongle can cause some serous changes/shadowing of the antenna pattern. Similar little dongles would have trouble going through "proper" desks with metal frames/drawers, and would end up plugged into USB hubs on monitors up on the desk.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 01, 2022, 05:51:17 am
content: Good point, no idea what the surroundings are like. Maybe it's an unlucky shadow.Tim

author: Ian.M
author_rank: Super Contributor
timestamp: March 01, 2022, 06:10:29 am
content: USB 3 can cause interference in the 2.4 GHz ISM band. Seehttps://www.usb.org/sites/default/files/327216.pdfIf its a desktop, relocate the dongle to the end of a USB 2 A(M-F) extender cable, and take three to five turns of the cable through a ferrite ring, preferably at the dongle end, or use clip-on ferrites at both ends. Ideally, use a USB 2 port at the PC end. Try to locate the dongle itself near your mouse pad. If your PC is under-desk and the desk isn't metal topped, it may be advantageous to stick the cable end to the underside of the desk close to the mouse pad.If its a laptop, try to keep USB 3 devices and RF dongles as far apart as possible, e.g. in ports on opposite sides of the PC.

author: calzap
author_rank: Frequent Contributor
timestamp: March 01, 2022, 08:56:12 am
content: Quote from: Someone on March 01, 2022, 05:43:42 amDefinitely possible. It's a HP Z2 workstation on top of my desk. The dongle and USB stick were plugged into adjacent vertical USB-2 ports on the front of the computer. And the USB stick was protruding out so as to be between the mouse and keyboard in their normal position and the dongle.Mike