Next RDS Forum meeting on 21 & 22 October at Geneva

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Main objective to assist the tuning to a radio programme

The use of more and more frequencies for radio programmes in the VHF/FM range made it increasingly difficult to tune a conventional radio to a desired programme. This kind of difficulty is solved with the Radio Data System, that has been on the market since 1987, and whose spectacular evolution is still continuing.

RDS has conquered all receiver price classes and is nowadays a must in the standard functionality of any radio receiver.

More than 38 years later after that technology was created, almost all FM radios use RDS. ICs have become available that have an FM receiver and an RDS decoder on the same chip and the price for such a chip, if bought in quantities, is now extremely low, say to give the magnitude, only one to three Euro. The trend of this price is still falling and the quantity of such chips sold on the world market is still much increasing, now over one billion units per year already.

RDS made FM radios user-friendly

The recent developments of highly integrated silicon tuner solutions with embedded RDS functionality has opened up a new range of products to the market. Many applications of RDS are nowadays already within mobile phones and portable network devices. The more traditional car radios have sometimes a separate RDS decoder IC, but RDS decoding is very often an integral part of dedicated multi-purpose digital signal processing, necessary for the product even without RDS. In these products the RDS function price is then almost zero, as it is done in software only.

The development of RDS started in the European Broadcasting Union, EBU. The developers aimed at making radio receivers very user-friendly, especially car radios when these are used where a transmitter network with a number of alternative frequencies (AF) is present. In addition listeners should be enabled to see the programme service name (PS) on an eight character alpha-numerical display and the transmitter frequency information, displayed on non-RDS radios, is then only used, in the background, by an RDS radio.

All this has become possible by using, for many years, the microprocessor controlled tuner technology, permitting a radio to be retuned within milliseconds. During this process the audio signal is muted which, because of the short time, is usually not detected by the ear. Thus, the radio is able to choose the transmitter frequency, among a number of alternatives that gives the best reception quality. It is also ensured that the switch-over is made to exactly the same programme content by performing a kind of identity check using the programme identity (PI) code.

Travel information with RDS is possible using the Travel Programme (TP) and Travel Announcement (TA) flags.

RDS is also used for the digitally coded Traffic Message Channel (TMC), which has been widely introduced all over Europe within EU funded projects. RDS-TMC is generally used by GPS navigational devices that use the TMC messages also for dynamic re-routing.

EON was a really nice enhancement

Once a radio is tuned to a programme service, broadcast within a network, using the RDS feature Enhanced Other Networks (EON) additional data about other programmes from the same broadcaster will be received. This enables the listener, according to his choice, to have his radio operating in an automatic switch-mode for travel information and this information comes from a service that, at a given time, does not necessarily contain such travel information.

RT+ is a powerful feature

Many of the receivers, apart from the usual RDS basic features (PI, PS, TP/TA, AF), implement also some of the dynamic RDS features such as Programme Type-PTY, Radiotext-RT and Clock-Time, displaying the time/date. The feature, called RadioText Plus is implemented in some car receiver models. The main purpose is to display Music title and Artist name and also the home page of the radio programme service for those radios that have an Internet access.

RDS is absolutely future proof and will not be replaced by digital radio, at least until such time as when FM broadcasting ceases to exist and this, for sure, is not going to happen in most countries worldwide within the next 10 years, in spite of all the breathtaking developments of the new era of digital broadcasting.


Since 2018 the RDS standard IEC 62106 contains the option RDS2. These are three additional subcarriers, modulated and structured as the basic subcarrier. This will permit to increase the data transmission capacity of RDS significantly. RDS2 uses only ODAs. Those already defined for legacy RDS can be tunneled over RDS2, e,g. RT+, eRT and RDS-TMC. In addition new applications, specific to RDS2, were specified by the RDS Forum. These are Station logo and Slideshow with or without text and the option to be synchronized with the music on air. Also linking to the same radio programme service stream on the Internet and transmitting RDS data over other bearers than FM will be possible. These new specifications will become an international IEC standard as from early 2023, ref. IEC 62106-6 ED.2.