I actually verified the problem of “ Wi-Fi becomes unstable at a specific resolution '' of Raspberry Pi 4
Released overseas in June 2019, from November 2019Technical standard conformity certification (technical suit)Single board computer that has been sold in JapanRaspberry Pi 4"If you set the screen output to a specific resolution, Wi-Fi is difficult to connect. I actually tested to see what kind of problem occurred.
Raspberry Pi 4 Wi-Fi problem: Firmware update will fix your screen resolution bug | ZDNet
Raspberry Pi 4 WiFi stops working at 2560×1440 screen resolution
This is the Raspberry Pi 4 purchased.
The problem this time is "If you set the screen output to 2560×1440 resolution on Raspberry Pi 4,2.4GHz Wi-FiMay be difficult to connect toThat means. Start verification by connecting Raspberry Pi 4 to a 4K monitor.
For the 2.4 GHz band Wi-Fi connection source,Pocket WiFi 504HWWas used.
The resolution of the screen output from Raspberry Pi 4 was set to 3840×2160 in the initial state.
When the resolution is 3840×2160, the connection to Wi-Fi was confirmed.
Next, set the screen output to “2560×1440”. Since the target resolution was not displayed in the resolution selection menu, enter the following command.
sudo xrandr –newmode "2560×1440" 146.25 2560 2680 2944 3328 1440 1443 1448 1468 -hsync + vsync
sudo xrandr –addmode HDMI-1 "2560×1440"
When executed, the item “2560×1440” appears in the menu for changing the resolution, so change the resolution.
When I checked the Wi-Fi connection status, I was unable to establish a connection and was in an unstable state.
The problem this time is that if you set the resolution of the screen output from Raspberry Pi 4 to 2560×1440, radio waves close to 2.4 GHz band will be emitted from Raspberry Pi 4, so it will interfere with Wi-Fi in 2.4 GHz band about. Spectrum analyzerWi-SpyUse to check whether the radio wave is actually emitted.
Check with Wi-Spy close to HDMI like this.
In the graph, the vertical axis is frequency, the horizontal axis is Wi-Fi channel, the orange line is the area of the channel to which the mobile router's radio wave corresponds, and the stronger the color becomes, the stronger the radio wave is emitted The At 3840×2160 resolution, the channel area of the mobile router is not particularly responsive.
Next, when I set the resolution to 2560×1440, there was a response on the screen. Strong radio waves are generated in the channel area of the mobile router, and it has been confirmed that there is a high possibility that the radio waves generated from the Raspberry Pi 4 and Wi-Fi are interfering.
Raspberry Pi official forumHowever, similar problems have been reported and may be addressed by patches.