To provide an on-vehicle antenna assembly and a transceiver system superior in serviceability.

Transceiver blocks of a radio information apparatus are mounted on a vehicle roof including a computer 16, a radio LAN unit 20, a TV antenna element 10, a TV tuner 12, an ITS radio access transceiver 14, and a GPS unit 13. Terminal units such as a TV receiver 21 working as a display, a navigator 22, etc., are installed on the vehicle front. The computer 16 connects the terminals to external circuits through the radio LAN unit 20, the transceiver 14, etc. Thus, the terminal units easily acquire external information, without any connection cables. The computer 16 automatically switches the antenna element 10 in the best state from navigation results (own vehicle position, running azimuth, access point and broadcasting station's position), thereby always making the antenna sensitivity best to improve the serviceability.