Is the FM-VHF-exit filtered by frequency or can I connect the DSC-controller-receiver (156, 525 mhz)?

The FM-output of the easySPLIT has an upper frequency limit of about 108Mhz. 156Mhz are in the cut-off area of the electronic filter connected to the FM output. Therefore it will not work to connect a DSC-receiver to the FM output (car radio). But, of course you can use the DSC controller at the VHF output of the easySPLIT.