Solved Motherboard built in Intel AX200 - very slow download speeds

[poisonborz]

Just got an Asus PN50 - with a built-in AX200 - and with freshly added Windows 20H2 the wifi is acting weird. Ping is mostly, and upload speed is always normal, but download very slow.
Asus N66U: 2.4G - 100ms ping, 15Mbps download, 5G: 6ms ping, 5Mbps download
TP-Link repeater - 2.4G and 5G both 30Mbps download

I've tried to change channels and settings in the router, to no avail - and since all other devices work with it normally, and this happens with both router and repeater, I guess the issue is not there.

I've tried to use both the AX200 driver supplied by Asus, and (after removing/uninstalling) the AX200 driver by Intel. The Intel driver resulted in even lower DL speeds. Anyone any idea what could be the solution?

 

[L&LD]

Long shot, but can you try switching the antennae leads on the Wi-Fi adaptor? Be careful, these things are very delicate if you try.

Could also be a defective adaptor too. Is this returnable/exchangeable?

And what firmware, features, and wireless settings are on the RT-N66U today?

 

[AndreiV]

Long shot, but can you try switching the antennae leads on the Wi-Fi adaptor? Be careful, these things are very delicate if you try.

Could also be a defective adaptor too. Is this returnable/exchangeable?

And what firmware, features, and wireless settings are on the RT-N66U today?

What antennae are you talking about?

This is a min PC, it fits in the palm of your hand.

 

[thiggins]

Using an AX device with an N router could have interoperability problems.
Check the Windows network properties for the AX200 and see if there is a way to force it to not use AX mode,

 

[L&LD]

@AndreiV, it still has antennae leads.

 

[poisonborz]

Thanks for all the tips - this is now solved! The problem was the router firmware after all - more specifically, an Asus driver bug affecting Intel devices. I used an old Shibby Tomato build. After I updated to FreshTomato - which uses a backported Merlin driver - the speed is now as it should be. The golden post that solved it all. The overall moral of the story would be to not jump to conclusions just because other devices work well - suspect a router issue if the problematic device (chipset) is new/unique.