I’m facing an issue with my Archer C6 router. When I set the 5GHz band to 80 MHz, the upload speed drops significantly. For example:

Download: ~97–100 Mbps (normal)

Upload: ~15 Mbps (very low)

However, when I reduce the channel width to 40 MHz, the upload speed improves drastically to ~170 Mbps, while the download speed remains similar.

Details:

Router: TP-Link Archer C6 (V2/V3)

Phone: Realme 8 (tested on multiple devices, same result)

Security: WPA3-Personal (kept same, issue persists)

5GHz Channel: Auto / 36 / 40 tested

It seems like the 80 MHz 5GHz setting causes upload instability with certain devices, even though download speed is fine.

Has anyone else experienced this? Is there a way to make 80 MHz stable on 5GHz with Archer C6, or is 40 MHz the recommended solution?

Thank you for any advice!