Twin fakra aerial adapter -worth using?

[tadziak]

Hello,
I have a VW GOLF V from 2008, with an Alpine IVA-202r installed. My original antenna installation uses two atennas - one on the roof and one at the rear
shield (diversity). My question to you is if it is better to use the twin fakra aerial adapter and connect both antenas into the Alpine unit,
or its better just two plug one of the antenas, using standard single adapter (for 1 antena)?

Do those two antenas' signals sum up when using twin fakra aerial adapter or this adapter chooses which one is stronger and sends it to the radio? Does it really work or it might cause some additional interferences?

I would be very grateful if you could clarifiy that to me...