Probably the device are faulty.

You're in the right place. Signal strength ~70% is just ok. 80 and above is best.

which device?
Cause i'm getting the same result using the TPLink and a cheap USB Wifi.

This post has been edited by d3v073d_50uL: Apr 8 2021, 12:35 PM

Remove the wall between the router and device by moving the router instead.
5Ghz signal typically drops off after 2-3 walls in between. Try moving the router higher up (bookshelf top/cabinet top).

Also device quality (not router quality) can have an effect.. if the USB wifi being blocked by a metal casing of desktop PC..
to have the best signal quality even using the most cheapo router in the world = "clear line of sight" without metal, walls, other solid objects
may want to move or extend the USB wifi with a USB cable for better LOS placement

For easier GUI interface on windows can use Xirrus Wifi inspector https://xirrus-wi-fi-inspector.en.softonic.com/

This post has been edited by ceo684: Apr 10 2021, 11:46 AM

use wifi repeater maaa~ 5ghz was meant to be fast wifi but with shorter distance ?

The usb wifi are connected to a hub ~50cm aparts from the PC itself.
The router are stuck to the wall, above head height.

Getting clear line of sight, is a bit impossible at this point.
And using extension cable, will be messy.

Yes... but currently it only affect the USB wifi on the PC only as the other devices, can connect to the 5ghz without any problem.
So, suspect it is whether the USB wifi it self is weak... or something's wrong with my Windows.
Haven't tried yet with other pc/laptop available

This post has been edited by d3v073d_50uL: Apr 10 2021, 02:22 PM