Regarding the FM antennas, there are no distinctions among the mentioned units. All of these models utilize the same antennas for FM radio reception.
However, in terms of Wi-Fi antennas, they are solely compatible with MRX720/MRX1120/AVM60. The MRX 520 does not have ports for Wi-Fi antennas, as it does not support Wi-Fi or Play-Fi for streaming content.