What is that roof antenna for?

[khengswee]

The newer BMWs all have these "shark fin" antennas. My 323ci has a short flexible antenna.

Are these for FM or cellphones? My ETK parts catalog seems to suggest they're for cellphones. Can anyone confirm this?

Also, has anyone tried REPLACING these with XM radio antennas?

 

[Bmw 325i 7803]

They're for cell phones since my car is an 03 and it has no antenna and no cell phone uplink either. My FM radio works fine...

 

[nbtstatic]

BMW Assist.