Don't know if it's helpful but I had the same symptom (connect to wi-fi at startup but turn grey after a moment) when using Mac Mini 6.2 system definition. I then changed system definition into Macbook air 5,2 and everything works.
Please can you tell me how you did this?
I have carried out some searches and found a program Chameleon Wizard.
There is a window in the program called SMBios.
In this section there's a section on the left "Generate Serial", and under this there's "Model Number" in which there's a dropdown menu with a list of Mac types. It's currently on Mac Pro (3,1) which I assume is default.
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Q: Is this where you make the change safely?
The reason I ask is because I find myself in a similar situation. I have the same WiFi card
TP-Link TL-WDN4800 (Rev.1.0,
like Atlantis). I get strong WiFi to start with, but it begins to drop off, come back, and then drop off again, until it's without a connection almost all the time.
Also, when I lose the connection, the symbol in the menu bar actually stays black for a lot of the disconnected-time. It also tends to go grey when disconnected for a long time. I live-stream TV in a browser tab to test the connection.
I have an old Macbook (2007) over 2 feet (70 cm) away from the WiFi antenna of the Hackintosh, yet the MacBook connects perfectly to the same Router/Modem, while the Hack. struggles.
The back of my Hack. (where the antenna is) is away from the wall by over 2 feet (65 cm) to (hopefully) ensure it's location isn't the problem. It's also 50 cm above the floor (on a box). The MacBook is 30 cm higher on a computer desk.
Any help would be greatly appreciated