RDS or Radio Data Services or RBDS Radio Broadcast Data Services has been around for a long time and used in a number of devices such as pagers and smart meters but for our purposes we will stay with the text display on FM receivers.
This is a process where an RDS encoder inserts small amounts of text in the FM signal which will display on FM Receivers. This may be the artist and title of the current song, station slogan or other informational, promotional or commercial campaigns.
There are two text messages sent to the encoder. The Program Service Name or PS which is an 8 character static message with the stations call letters or street name and Radio Text or RT which is a 64 character dynamic message text message. While newer receivers have larger screens showing all data, most older and even some newer FM Receivers do not display Radio Text or require the listener to press and “i” info or “D” display button.
The listener may unaware of the command or if used they see a blank display or a “No Text Data” message as the station is not sending RDS data. To overcome this issue encoder manufactures introduced the Dynamic Program Service or DPS where the 64 character messages is broken into 8 character segments and sent as the PS. When introduced thousands of listeners turned on their radios and the now playing data displayed with the most common response of “I Love That”. While not part of the standard it has become common place but when used it is recommended to use Block scrolling where the text is scrolled 8 characters at a time and a scroll rate to 2-3 seconds. Using the scroll method scrolls 1 character at a time and can be distracting.
Posting data to and RDS Encoder
Depending on the station equipment the encoder may be located at the station or may be at the transmitter site. Either way, information is sent to the encoder via RS-232 Serial connection or via an IP link.
For a serial feed it may be necessary to add a serial card to the PC or to use a USB to Serial connector. If the encoder is at the station a serial connection is normally not an issue. If the encoder is at the Transmitter it may be necessary to use the Serial port on the STL to connect to encoder at the transmitter. If the port is unavailable it may be necessary to install a serial line to the transmitter or to use an IP connection. Note: The Serial connection will be required every few minutes 24×7 so it needs to be a reliable connection.
Most encoders support a TCP/IP or UDP connection which can be used to send the RDS data to the encoder. Like the serial connection, if the encoder is at the station it just needs to be on the same network as the sending application. If it’s at the transmitter if will require a static IP or require port forwarding to get to the encoder.
The two most common IP issues is the encoder IP cannot be accessed from the sending computer. If so, it may require a second NIC to connect to the encoders network or altering the networks so both the CSRDS computer and encoder are on the same network. When connected we can ping the encoder from the sending computer.
The second and more common issue is the port. While we can ping the encoder we may still have issues sending data if the port is blocked by the network security which may be on the computer running the application, the network switch/router or a group policy. Errors can occur if the port is already in use by another application or service.
There are two protocols for sending text to the encoder. UECP which is the original encoding format commonly used in Europe and ASCII which sends text based commands commonly used in North America. CSL uses the ASCII option as it is easier to track and trouble shoot as you can see the actual data being sent rather then text and binary codes in the feed.
FM Analog RDS\RBDS Commands
PI: The Program Identifier or PI is a hex code included in the RDS signal that identifies the station and becomes the “digital signature” of the station. In the US this is identified by a formula based on the station’s call letters. For Example, station KNAB would have a PI of 3255. For Canadian stations, Industry Canada has posted a spreadsheet created by the CBC to calculate Canadian PI codes on their web site at https://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/h_sf08741.html.
PS: Program Service Name: The station’s “street name” that will appear on the receiver faceplate display. The PS can be up to eight characters in length (including spaces) and can be as simple as the station’s call letters (“PALM” or “PALM FM”) or a slogan (“THE HAWK” or “FM96”). The Program Service Name is automatically displayed on all RDS enabled devices.
PTY: The PTY or Program Type is a pre-defined code and is a number between 01 and 31.Many RDS receivers are able to seek the listener’s preferred format automatically. This means that a car radio can switch from a fading station to a stronger one that carries the same variety of music. The PTY function of RDS helps a broadcaster catch ‘transient audience’ share.
RT: This is the Radio Text which is a 64-character “scrolling” message containing the artist and title information, promotional message, weather forecast, etc. This message is also sent to RDS enabled devices but may require the listener to press an “Info” button to see this message and some RDS receivers DO NOT display Radio Text.
DPS: Due to the limitations of some receivers to display Radio Text, several RDS/RBDS encoders have a Dynamic Program Service or DPS option. When used, the 64-character message is broken into 8 character segments and will automatically display in the PS area of the RDS enabled device. Check your RDS Encoder manual for restrictions and details.
RT+: The RT+ code is a special code sent via the RDS\RBDS encoder to RT+ enabled devices such as Microsoft’s Zune MP3 Player allowing the listener to purchase and download the current song. This can be done immediately if the device is connected to the internet via a wireless link or at any time for RT+ enabled devices such as cell phones. When connected, the album art can be displayed and if desired, the listener may preview a few seconds of the song or purchase and download the song to the device. If not connected, the “tag” is saved and the option is available when the RT+ device is connected.