FM Radio Card Antenna - RAR - 990129

The biggest difference between the FM Radio Card antenna connnection and any other FM Radio is they type of connector used.  The antenna jack is a stereo 1/8" (3.5mm) type.  However, only the shield (sleeve) and center conductor (tip) are utilized.
To connect an unbalanced-fed (eg., coax fed) antenna, simply terminate the coax in a stereo or mono 1/8" plug.  Connect the coax shield to the sleeve (GND) and the center conductor to the tip.  Or wire up an adapter with a 1/8" plug on one end and a mate (type-F, BNC, etc) to your existing antenna connector on the other end.
If you have a balanced-fed (eg., twin-line) antenna, you may connect the two wires to the two plug connections described above.  However, this will not give maximum performance.  You would be better to use a BALUN between the antenna and the radio antenna jack.  BALUNS (BALanced-to-UNbalanced) adapters are often sold for FM and TV antennas.  Any of these should be suitable.