The Radio Data System: FM radio adds features to stay viable, part 3

Broadcast FM radio has extended its user-friendly capabilities through the addition of embedded, backward-compatible functionality which adds text and even graphics to the radio display.

RDS is part of FM radio’s effort to maintain relevance and meet user expectations in the face of many alternative ways in which users can access news, music, and more while in the car, at the beach, and yes, even at home.

Q: What are RDS and RBDS?
A: RDS and RBDS can be used to transmit various types of data, such as data related to the transmitted radio program, including the name of the station or the name of the track, or the artist. It can be used for many other purposes, particularly for hidden messages and signals.

RDS has been in use in Europe and Latin America since the early 1990s. An FM broadcast receiver equipped with either is sometimes called a “smart radio.” Data types carried by RBDS include:

Alternative frequencies (AF)
Clock time (CT)
Enhanced other networks (EON)
Program identification (PI)
Program service (PS)
Program type (PTY)
Radio text (RT)
Travel announcements (TA)
Traffic program (TP)
Traffic message channel (TMC)

Q: What is the difference between RBDS and RDS?
A: RDS originally began in Europe in the mid-1980s as a project of the European Broadcasting Union providing a protocol for the distribution and propagation of data by FM radio signals. The standard was subsequently enhanced in 1991 with features including alternative frequencies functionality, and it was published under the auspices of the European Committee for Electrotechnical Standardization, CENELEC.

In North America, the U.S. National Radio Systems Committee issued its version known as the Radio Broadcast Data System (RBDS) in 1992. In the US and North America, it is called the Radio Broadcast Data System (RBDS). The two standards (RDS and RBDS) are very similar, with the main difference in the classification of the program type that is transmitted, such as news, sports, drama, pop music, and jazz music.

Q: When did RDS show up in cars?
A: By the early 2000s, cars began to have a basic RDS capability, and by 2020, nearly all cars offer some type of RDS-friendly display.

Q: What features does the standard support?
A: Many things: in addition to clock time and station information, it can show items such as song title, performing artist name, and other content-related information, It can also be set to traffic announcements (TA) mode, where it will display traffic bulletins as they are updated. There is also an auto-tune capability, where the radio can automatically track and follow a station’s content when the car moves from the service area of one transmitter to the next.

Without RDS the radio must be manually tuned to the next station. This auto-tune is possible when the station is part of a national network broadcasting from many different transmitters around the country, with each network assigned a Program Identification (PI) code. The RDS can auto-tune the radio to follow a given PI code.

Q: What does the RDS display look like?
A: That has evolved over time. Initially, when automotive companies started implementing RDS, cars had only single-line or few-line displays and so didn’t have a lot of room (Figure 1). As a result, auto radios focused on implementing program service (PS), which was originally meant to be a static station naming field of only eight characters. Basic PS evolved into PS scrolling, where a long string of station names, song titles, artist, and branding information was cut up into eight-character blocks, sent over a period of time with a delay between each block.

Figure 1. The original RDS display in the car had just one or a few lines, with limited ability to provide information to the user (Image: Nautel Inc.).

Q: That doesn’t sound like much – can RDS go beyond that simple display?
A: Yes, the standard allows for more, and most new auto FM receivers have the needed decoding and also an LCD “full-image” screen rather than just a single or few lines. RDS allows broadcasters to add small amounts of data to the transmission which will be displayed in the receiver.

Q: What happens next?
A: There are two message formats that are sent to the decoder. The Program Service (PS) Name is a static 8-character message with the station call sign, frequency, and marketing “street name” (such as “Boom 101”). The second message is the Radio Text (RT) field, a 64-character field containing metadata. This metadata can represent more information including a small picture of the album from which the song is taken (Figure 2).

Figure 2. As display technology advanced and cars added more console functionality, its RDS display capabilities expanded literally and figurately to include different font sizes and more information, and even small images (Image: Nautel Inc.).

Q: What makes this happen?
A: At the transmitter, a middleware application is required to capture the metadata, format it, and send it to the encoder in a format that can be decoded. Not all FM broadcasters have implemented RDS (most have) while some have only implemented the simper formats.

The final part of this article looks at more RDS details.