jumerle

I am replacing my Nakamichi stereo with pioneer AVEC 8100 double din unit but I noticed that there are two antenna jacks on the Nakamichi stereo but on the pioneer unit there is only space to insert one jack. Does anyone know which jack I need to insert and why are there two antenna jacks on the Nakamichi stereo?

Can someone please supply me with the wiring diagram for the Nakamichi amplifier? I want to keep the use of my factory installed amp and speakers but I do not have the schematic for the amp.
Thank you