RTI TMC problems

Hello, now I have read all TMC-Postings here and unfortunately I am still not further … so I have to get it myself: Have a 99er RTI (CD-Version and TMC capable). Unfortunately, the good piece does not find a TMC-Sender. Have a second car with a Blaupunkt-Navi and that finds at the same location various transmitters. Various texts here speak of an extra antenna. Where can I find this and where is it connected to the Navi-Unit? I have another question: In the sky of my S80 I have such a cover plastic under which there is a cable with a green multi-pole plug. What else should you connect? Another antenna for ….. ? Thank you for your answers … Janos