The disclosure relates to a radio modem for a motor vehicle, having an antenna arrangement, an AD-DA converter and a processor for exchanging communications data between the motor vehicle and at least one object in the vicinity of the motor vehicle. The processor is configured to provide at least one communications standard, which in each case specifies a digital protocol stack for controlling the exchange of communications data and a radio frequency f0 for a radio signal, and implementing every provided communications standard by operating the associated protocol stack and by providing a digital mixer, which is coupled on a baseband side to the protocol stack and on an HF side to the AD-DA converter and which provides for the radio frequency f0 on the HF side, wherein the AD-DA converter is connected directly between the processor and the antenna arrangement.