Hello all,
Many here have seen my prior posted struggles with USB3, Pi4, and wireless. Finally, after a month+ of pulling my hair out trying to get my config to work right, I think I finally understand what is going wrong. Hopefully this note will help others avoid my experience. The long and short is that the Pi4's USB3 ports are jamming 2.4Ghz Wifi. What many suggest is "power issues" turns out to be USB3 RF interference. This ONLY occurs for USB3 + 2.4Ghz connections. The symptom is that the 2.4Ghz wireless network will either not be visible, or will drop back to hotspot as soon as USB3 is detected (boot time or at cable reconfig). Pi4 is an almost perfect 2.4Ghz wireless self-jamming device due to having its USB3 ports and HDMI ports in close proximity to the wifi antenna (top of board near GPIO pins 1-6). Poor shielding (cables and connectors) can magnifiy the issue, but even good cables won't eliminate the problem. Some particular Pi4 casings can help (better grounding), others will hurt. Cable lengths and device distances also factor in the RF interference @ 2.4Ghz. Too many variables! Many have responded to my prior posts that their Pi4 setups work fine. I believe those Pi4s that ARE working are not using USB3 + 2.4Ghz wireless networking (or fortune has smiled on them greatly). That said, the Pi4 + USB3 CAN work great under certain circumstances:
- Pi4 + USB3 + 5Ghz wireless should be fine.
- Pi4 + USB3 + hard wired (cable) Ethernet is ok
- Pi4 + USB3 + blind hotspot is ok (i.e. NOT mapped back to a 2.4Ghz "infrastructure" internet source).
- Very curiously, I can most often get stable USB3 with 2.4Ghz AFTER booting with USB2 (i.e. cableup USB2 port, boot, then move cable to USB3 after ~minute).
Note:
- Pi4 + USB2 + 2.4Ghz wireless (+ Powered USB3 hub in downgrade USB2 mode) works fine.
What will NOT consistently boot is Pi4 + USB3 + 2.4Ghz wireless. I recently found the Intel white paper on this general issue from years ago. Fits my symptoms exactly. Here's the link:
www.intel.com/content/www/us/en/products...erference-paper.html
USB3 RF interference @2.4Ghz is the problem. RF interference @2.4Ghz also occurs for HDMI, Bluetooth, and even a particular screen resolution! Looking back now at many forum posts (here and in the Raspberry Pi forum), where Pi4 + USB3 + 2.4Ghz odd networking issues occur, these may have a (known or unknown) underlying RF interference factor.
So, Pi4 + USB3 is great (more memory, faster CPU, USB3 allows 10X read/write performance gain and SSD longevity benefits over SD). Just be wary of USB3, bluetooth, and HDMI with 2.4Ghz wireless. I tried multiple different twisted/shielded USB3 cables and carefully mapped out all power (to eliminate this as a possible issue). The Pi4 design itself is part of the problem...not their fault...just hard to have HDMI, USB3, and wireless using 2.4Ghz in close proximity. In the end, for my use, I will add an Ethernet cable to retain a USB3/network speed advantage. If you're trying to stay wireless with USB3, be prepared to need 5Ghz, or stay with blind hotspot mode(which requires off-line platesolving and image transfers via cable or sneaker-net). Hope this helps someone. Cheers all....