How Do You Get The Kanto Radio Card In Pokemon Soul Silver?

Fix the generator at the power plant. To do this you need the part which is stolen by a team rocket grunt who hides in Misty's gym in cerulean (or around there I forget) then you chase him north and fight him, he then reveals it is Hidden behind an inner tube in the Cerulean gym. After all is fixed go to lavender town and speak to the man with blue hair who will update your radio.

Hope that works, its been a while so I might be off in a few areas