I assume you are refferring to the co-axial cable thast runs from the radio aerial to the radio/cd/head unit. If this is the case you can buy connectors for this type of cable from your local tv/auto parts shop. Use the connectors and put in a professional join, or buy a soldered joiner and re-connect it permanantly, it's up to you.
Sorry about the slow reply....
Cheers
Sixpack Subaru