Question Wifi PCI-E card problems with antenna

[In_JuraSky]

Hey all,
I stumbled upon a strange problem, on one of mine desktop PCs, I have a wifi PCI-E card. I recently bought a new card to replace an old hardware (ASUS PCE-AC56) which presumably had a broken antenna connector, and wouldn't run with the external antennas plugged in. After I installed the new card (TP-LINK TL-WN781ND) the PC wouldn't connect to the router no matter what. Then I had an idea, to unscrew the antenna from the TP-link card, and suddenly the Pc could connect to the internet again.
I looked through the interne of what the possible reason could be, but couldn't find any reasonable info, mind the second desktop is connected via LAN and all other laptops and phones work OK (to an extend of the capabilities modem/router provided by the provider, which could be better).
For info, the affected desktop is in the same room as the router, around 6m apart, however a cable connection is difficult, while the cable would have to circumnavigate the entire room (which would be close to 25m of cable). There is not many things in the way of the signal.

So my question would be if somebody encountered such a problem, and if buying a normal router would solve the problem?

The PC specs are:
MB: MSI X99 GAMING 7
CPU: intel i7-5820K
GPU: msi GTX980 Gaming X
PSU: corair RM750

 

[Lutfij]

I think you're facing a grounding issue with your chassis when you have the antenna's installed on the wifi adapter. If I'm reading this correctly the issue crops up only when you've added the antennas and they are tightened down to the chassis's frame? Which OS are you on and which version of the OS are you running?

 

[In_JuraSky]

Yes the problem occurs only when the antennas are tightened to the card, not the chassis, or at least not directly. I run Win10 latest version. The interesting part is that the problem randomly appeared maybe 1year ago

 

[In_JuraSky]

I can remeasure the antenna shielding in regards to the chassis or to the earth plug on the psu even... should not be a problem....

 

[In_JuraSky]

I can remeasure the antenna shielding in regards to the chassis or to the earth plug on the psu even... should not be a problem....

So I did a Rezistivity measurement of the antenna to the chassis and to the gounding pin on the PSU, both had resistance close to 0 Ohm, in DC, unfortunately I do not poses and oscilloscope to measure the impedance... Do you have any idea, how else this theory can be tested?

Cheers