I've got the silabs version (but ordered one of these as well for testing).
On the silabs I removed the stock antenna and soldered an antenna adapter straight onto the board so that the tip is where the original antenna was, and the sleeve is somewhere on a groundplane.
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this topic should have some pics/more info )
Also check if you have a powered car antenna. Of you do you should be able to fix that by attaching the switched power lead to the antenna power lead.
BUT : this also provides the voltage to the Radio if it doesn't have a decoupling capacitor. I haven't got the device yet so I can't check. (should be there, but test on your own risk)
But its good to hear that the Silabs plugin is working fine.