I am reinstalling all the audio in my 1990 300zx na 2 +2. I have the antenna adapter and have read a number of posts but I think I'm missing something. The adapter splits in 2. 1 male end and one female. The male obviously fits into the new head unit but what is the other end for? I understand there are 2 antennas but should I have a second cable somewhere to plug into the female end of this? Thanks.