Huge WiFi speed difference between mobiles devices and PC

[henry.live21]

After multiple tests across many different times of day, I am still getting huge disparity between the speeds shown on my mobile devices (Pixel 2 XL & Samsung Tab 2) in comparison to my PC.
The mobile devices will hit speeds of 40-50 Mbps with low ping, while the PC will vary hugely between 0.5 Mbps and 12 Mbps at maximum, but all the time getting wild swings in ping results.

These tests are run at exactly the same time from the exact same location connected to the same network (there are 2 networks in the property).

The network PCIe card in the PC is a TP Link N600

What suggestions do you have for troubleshooting and finding a solution?

 

[Ralston18]

TP Link N600 is a router.

E.g.: https://www.officedepot.com/a/products/538562/TP-LINK-N600-Wireless-Dual-Band/

Please confirm the components being used: 1) Make and model wireless router, 2) the PCIe wireless adapter installed in your computer.

And, in the meantime, ensure that you do not have both the wired and the wireless adapters enabled on your computer. Should be only one or the other; the wireless adapter in your case as I understand your post.

 

[failboat]

wifi bandwidth is very complicated. advertised rates mean nothing.
They test near 0dB when the best you can get is -30dB with your device on top of the router. -50dB line of site 8ft away.
-30dB is 80% drop in speed, -50dB is 90% drop. a room or two down might be -70dB or worse.

You should run ethernet to your pc if possible. a new AC card with mimo will help. you need to check your wifi AC specs and all your devices/adapters.
those devices are newer and likely have mimo, which uses more antenna's on both sides to multiply the bandwidth. wider channels can be used with AC over N. if you have greater than 50Mbs internet then getting wired is the only way to avoid bottlenecks.

https://www.smallnetbuilder.com/wireless/wireless-reviews/33084-ubiquiti-ac-pro-and-ac-lite-access-points-reviewed?showall=&start=2