[boschmann]

Those adapters are for aftermarket radios and go right at the radio & provide a switched power source for the antenna - I believe they actually run power through the antenna wire. Look at a few sites to get a better understanding, most are wanting to sell their adapters, find one that has good descriptions of the system. Without seenig what is going on with your system it is hard to give advice, perhaps you have a radio shop nearby that is familiar with VW's.