i just got my unifi 30mbps few days ago. I use the Dlink Ac1200 (DIR 850), the stock router that was provided by TM.

On my mobile devices eg. android phone, ipad, etc, all can get 30mbps speedtest no problem.
On my asus zenbook laptop, can also get consistent 30mbps speedtest no problem also.

However, on my XP 8700 desktop pc, the speed is sluggish and i can get like 2-3 mbps and sometimes 15mbps, 28mbps but that is very rare.

I've checked out the problem and i suspected that the wireless network adapter in my 8700 is the problem. it uses Dell 1703 802.11 b/g/n (2.4Ghz) adapter.

my asus laptop is using Intel Dual Band Wireless AC 7265 adapter.

i do not want to resort to use LAN cable as the distance from my router in my living room & the PC in my study room is quite far away (~10meters long).
I tried checking latest drivers but windows 10 said, the drivers are all up to date.

any suggestion on how to fix the slow speed on my PC?