SVX Stereo gurus... TWO antenna leads?

I just yanked my (aftermarket) head unit out of the car for the first time to wire up some component speakers to replace the blown ones....


All of that seems straightforward... my problem is the antenna leads. The shop that put this head unit in originally apparently cut and spliced the antenna system together, leaving one of the coax leads chopped off and unused.

Does anyone know why there are two antenna leads and how I can take advantage of them? I'd like to rewire this properly, I've been getting really terrible radio reception.

Thanks for your help!