Radio Data System (RDS) — a multifunctional standard designed for transmitting informational messages via FM broadcasting channels in the VHF band. It has found its widest application in car stereos/radios and professional stationary FM tuners, enabling the display of text information accompanying radio broadcasts, transmitted by radio stations. Supported by the VHF CCIR standard.
Technical details
The RDS signal is transmitted using a 57 kHz subcarrier, which is the third harmonic of the 19 kHz stereo pilot tone. This ensures compatibility with mono and stereo FM receivers. The subcarrier is amplitude- and phase-modulated with a data stream at 1,187.5 bit/s, encoded with a block structure and error correction for reliable reception in mobile conditions.
Key RDS functions include:
- PS (Program Service) — displays the station name (8 characters).
- RT (Radio Text) — transmits textual messages up to 64 characters.
- AF (Alternative Frequencies) — list of alternative transmitter frequencies for automatic retuning.
- TP/TA (Traffic Program/Traffic Announcement) — flags for traffic information broadcasts.
- CT (Clock Time) — transmits the current time and date.
Some advanced implementations include Enhanced Other Networks (EON) for cross-station service linking, and Radio Paging features for sending short digital messages to compatible receivers.
Diagram showing the FM multiplex spectrum with the RDS subcarrier
Related articles: VHF CCIR, FM,
FM Radio Frequencies in Moscow
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