The present invention relates to a high-speed interface for radio systems, in particular to a synchronous serial digital interface for a car radio. In an embodiment, the synchronous serial digital interface for at least dual radio receiver systems includes a master device and a slave device. The dual radio receiver system has an intermediate frequency. The master device and the slave device exchange data in a bi-directional manner on at least one communication channel; the master device and the slave device have a unique bit clock; the master device supplies a synchronization signal to the slave device. The synchronization signal has a frequency spectrum with an amplitude at the intermediate frequency lower than the amplitudes at the other frequencies of the synchronization signal.