See also:
Support for discontinued RDS encoder models
Online Technical Support


What is the Radio Data System (RDS)?

The Radio Data System (RDS) is intended for application to VHF/FM sound broadcasts in the range 87.5 MHz to 108.0 MHz which may carry either stereophonic (pilot-tone system) or monophonic programs. The main objectives of RDS are to enable improved functionality for FM receivers and to make them more user-friendly by using features such as Program Identification, Program Service name display, program related text information and where applicable, automatic tuning for portable and car radios, in particular.

The Radio Data System has spawned in Europe around 1980. At present it starts to be used in all the world. It brings some useful possibilities. The listener's receiver can display station name, stations phone number and address, artist and title of actual song playing, traffic announcement, program type and much more.

In USA the system is called Radio Broadcast Data System (RBDS). The RBDS is very similar to RDS. All RDS encoders from our production can be used in USA without restrictions.

The most important RDS services are described below.

PS - Program service name
This is the label of the program service consisting of not more than eight alphanumeric characters, which is displayed by RDS receivers in order to inform the listener what program service is being broadcast by the station to which the receiver is tuned.

LPS - Long Program service name
The Long Program Service name (Long PS) is an addition to the PS. Receivers equipped with the Long PS function allow to show up to 32 bytes long station name. Since the Long PS is UTF-8 encoded, it covers all languages and letters, as well as multiple symbol sets.

RT - Radiotext
This refers to text transmissions, primarily addressed to consumer home receivers, which would be equipped with suitable display facilities. The text can be up to 64 characters long. Some receivers do not support the Radiotext service.

An additional feature of the Radiotext is the Text A/B flag. Two cases occur: If the receiver detects a change in the flag, then the whole radiotext display should be cleared and the newly received radiotext message segments should be written into the display. If the receiver detects no change in the flag, then the received text segments or characters should be written into the existing displayed message and those segments or characters for which no update is received should be left unchanged. For static RT (i.e. RT is not updated and shows only a general information like studio's phone number), the A/B flag has no meaning.

RT+ on iPodClick here for summarization of national character coding issues

RT+ - Radiotext Plus
The RT+ is designed to let the listener take additional benefit from the Radiotext service by enabling receivers to offer direct access to specific elements of Radiotext. Typically the RT+ feature supports song artist and song title elements. These elements anyway carried in the Radiotext, are identified by their class code, length and location within the Radiotext. The receiver must be equipped with the RT+ function (also called "tagging") to take advantage of this feature.

Click here for information about how to send RT+ tagging with our RDS encoders

AF - Alternative frequencies list
The list of alternative frequencies gives information on the various transmitters broadcasting the same program in the same or adjacent reception areas. This facility is particularly useful in the case of car and portable radios.
When the PI code indicates local coverage-area, i.e. only one frequency is used, AF list may contain this single frequency.

PI - Program identification
This information consists of a code enabling the receiver to distinguish between countries, areas in which the same program is transmitted, and the identification of the program itself. The code is not intended for direct display and is assigned to each individual radio program, to enable it to be distinguished from all other programs. One important application of this information would be to enable the receiver to search automatically for an alternative frequency in case of bad reception of the program to which the receiver is tuned; the criteria for the change-over to the new frequency would be the presence of a better signal having the same PI code.
The PI code consists of four characters. The first two characters have special meaning, second two are used to clearly identify different stations.
The first character identifies country. The second character identifies program type in terms of area coverage:
0 - Local (Local program transmitted via a single transmitter only during the whole transmitting time.)
1 - International (The same program is also transmitted in other countries.)
2 - National (The same program is transmitted throughout the country.)
3 - Supra-regional (The same program is transmitted throughout a large part of the country.)
4 to F - Regional (The program is available only in one location or region over one or more frequencies, and there exists no definition of its frontiers.)

ECC - Extended Country Code
It helps the receiver to recognise the country in cooperation with the PI code. The first most significant bits of the PI code carry the RDS country code. The four bit coding structure only permits the definition of 15 different codes, 1 to F (hex). Since there are much more countries to be identified, some countries have to share the same code which does not permit unique identification. The ECC byte determines the country unambigouesly.

Click here to find ECC and first PI digit for your country!

PTY - Program type
This is an identification number to be transmitted with each program item and which is intended to specify the current Program type within 31 possibilities. This code could be used for search tuning. The code will, moreover, enable suitable receivers and recorders to be pre-set to respond only to program items of the desired type. The last number, i.e. 31, is reserved for an alarm identification which is intended to switch on the audio signal when a receiver is operated in a waiting reception mode.

TA - Traffic announcement identification
This is an on/off switching signal to indicate when a traffic announcement is on air. The signal could be used in receivers to:
a) switch automatically from any audio mode to the traffic announcement;
b) switch on the traffic announcement automatically when the receiver is in a waiting reception mode and the audio signal is muted;
c) switch from a program to another one carrying a traffic announcement.
After the end of the traffic announcement the initial operating mode will be restored.

TP - Traffic program identification
This is a flag to indicate that the tuned program carries traffic announcements. The TP flag must only be set on programs which dynamically switch on the TA identification during traffic announcements. The signal shall be taken into account during automatic search tuning, so I recommend to turn this flag on even though you don't transmit any traffic announcements.

DI - Decoder identification
Indicates which possible operating mode is appropriate for use with the broadcast audio. Many receivers ignore this service completely. For others, only the Stereo and Dynamic PTY flags have a sense. Set the Dynamic PTY if your PTY changes dynamically in dependence on actual program content. Flags Artificial head and Compressed are archaic and should be kept cleared unless you have a real reason for their use.

M/S - Music/speech switch
This is a two-state signal to provide information on whether music or speech is being broadcast. The signal would permit receivers to be equipped with two separate volume controls, one for music and one for speech, so that the listener could adjust the balance between them to suit his individual listening habits.

CT - Clock-Time and Date
Time and date codes should use Coordinated Universal Time and Modified Julian Day. The listener, however, will not use this information directly and the conversion to local time and date will be made in the receiver's circuitry. The CT may be used as a time stamp by various RDS applications and thus it should be accurate.

EON - Enhanced Other Networks information
This feature can be used to update the information stored in a receiver about program services other than the one received. Alternative frequencies, the PS name, Traffic Program and Traffic Announcement identification as well as Program Type and Program Item Number information can be transmitted for each other service. The relation to the corresponding program is established by means of the relevant Program Identification.

IH - In House Applications
This refers to data to be decoded only by the operator. Some examples noted are identification of transmission origin, remote switching of networks and paging of staff. The applications of coding may be decided by each operator itself.

PIN - Program-Item Number
The code should enable receivers and recorders designed to make use of this feature to respond to the particular program item(s) that the user has preselected. Use is made of the scheduled program time, to which is added the day of the month. The transmitted Program Item Number code will be the scheduled broadcast start time and day of month as published by the broadcaster. This feature is deprecated and thus it has been removed from our encoders.

PTYN - Program Type Name
The PTYN feature is used to further describe current PTY. PTYN permits the display of a more specific PTY description that the broadcaster can freely decide (e.g. PTY=4: Sport and PTYN: Football). The PTYN is not intended to change the default eight characters of PTY which will be used during search or wait modes, but only to show in detail the program type once tuned to a program. If the broadcaster is satisfied with a default PTY name, it is not necessary to use additional data capacity for PTYN.

TDC - Transparent Data Channels
The transparent data channels consist of 32 channels which may be used to send any type of data.

Fill your FM frequency to AF (method A) and make sure the second digit in PI is 0 (zero), for example '20A6'.
The lower byte of the PI (in this example 'A6') must be unique in the area of coverage, i.e. no neighboring station may use the same last two digits of the PI.

For each station in the same location a unique PI (Program Identification) must be assigned. Stations that carry different program must be unambiguously identified by the lower byte (last two digits) of the PI. In other case they are recognised as one station by car radios, regardless of any other service settings. If the PI is not assigned to your station by your government, choose such number that is not in conflict with other stations in the area.
When you first use the RDS encoder, the PI is usually set to factory default value FFFF and it's necessary to change it as soon as possible.

When you store your station into the car radio preset memory, the station PI is also stored. If you invoke the station from the preset memory later and the receiver detects another PI, it starts to search the FM band for the station with the same PI which has been originally stored. Depending on the receiver model, this may result in unexpected interruption of listening.
To solve this, tune your station manually using up and down buttons and store your station to the receiver's preset memory again. Of course, to make the life easier for your listeners, always keep on mind:
1) After purchasing the RDS encoder, set your final PI as soon as possible.
2) When replacing your old RDS encoder with a new one, set the same PI as on the old encoder.

Broadcasters using splitting of the network must pay attention to the PI settings. The PI of each regional variant shall differ in the second digit (4 to F) and may be static. This convention permits a receiver to use a regional on/off mode. When a receiver is in the mode "regional off", it leads to the acceptance of the PI with the differing second digit, and thus permits switching to a different regional variant. This option can be deactivated by choosing the mode "regional on". Then only frequencies having the same second digit of the PI (i.e. the same program) will be used. This should also be the case for receivers without regional on/off mode.

Optional switching of the second PI digit to 1, 2 or 3, respectively, informs a receiver that now all frequencies for all regional variants carry the same program and the receiver can switch to these frequencies regardless of the receiver's regional mode. Broadcasters using splitting of the network during certain hours of the day may also consider using of AF method B.

Please never do this:
✘ Dynamically change last two digits of the PI,
✘ dynamically change the AF lists.

The RDS standards have been written in the 1980s. The most common LCD displays at that time made it possible to display only 8 alphanumeric characters. A wide range of devices and different ways of use eliminate the possibility of centralized display format control.
The result of all this is that the RDS standards do not contain any layout control commands or explicit on/off switches for displaying particular RDS services or graphic effects. No RDS encoder can tell the receivers how many lines of Radiotext to display, how to alternate the information on a smaller LCD, what should be the position of the text, whether to display the tuned frequency or not, etc. Depending on the receiver model, some of this can be controlled in the receiver's menu.

It's somewhat surprising how often this question occurs, especially in conjunction with TA or EON service. Please imagine the consequences if it would be possible! Fortunately, it is technically impossible.
You cannot remotely tune the receivers in the area to your frequency. The receivers don't listen to your station so they don't know anything about existence of your station and they don't receive the data which you carry in your RDS. You can put anything to your RDS but it is absolutely meaningless if you send it to nobody. Both the TA and EON services work different way, they are carried on the currently tuned station. Maybe 0.1% of all receivers contain a secondary tuner which is theoretically able to do a continual scanning of the FM band in background of normal listening, searching for a station with TA, but the result is unpredictable.

All RDS encoders from our current offer support separate data channel (RDS2) for the station logo, according to the latest IEC 62106 standard. The logo feature is well known from digital radio broadcast promotions. For the FM RDS there was no equivalent function defined for a long time. Although the interest in sending the station logo is quite understandable from the broadcasters, current car radios still don't fully support the graphics reception via RDS.

In many cases the car radios implement another solution which uses a large pre-programmed set of known station logos. This set is being further updated, for instance via DAB reception or via cloud. Particular logo of FM station is showed if received PI (RDS Program Identification code) and ECC (Enhanced Country Code) matches. Thus, the RDS points to appropriate logo in the receiver's database. Our RDS encoders support the PI and ECC as well.

This question is concerned only with stereo broadcast. In this case it's preferable to synchronise the RDS subcarrier with the 19 kHz pilot signal, rather than leave these two signals in complete independence. In fact substantial intermodulation may be produced between the 3rd harmonic of the pilot signal and the RDS signal, generating a unwanted beat which may be audible.

The RDS signal level on FM transmitter input should be as small as possible, but RDS must be displayed properly on a receiver. If you don't have any special measuring instrument, compare it with commercial radio stations. The right level should be between 3 and 11 % of the audio signal, measured in peak-to-peak values. Recommended value is about 6 %, which results in 4 kHz deviation of the FM carrier. Don’t forget that maximum FM carrier deviation with RDS and audio signal is 75 kHz.

The RDS signal must respect a phase criterion (in phase or in quadrature) with the 19 kHz pilot tone. In order to achieve this characteristic, the RDS encoder integrates a digital PLL with software phase control.
The oscillograms below show the appearance of RDS signal, pilot tone and a RDS signal added to the pilot tone. In real operation the phase difference can be easily measured for example using the P275 FM Analyzer.

Conditions: Pilot deviation: 6.8 kHz, RDS deviation: 3.4 kHz, no audio input. Measured at the FM transmitter input.

phrds.jpg (4068 bytes)   phpilot.jpg (3120 bytes)
1. RDS signal, 2. Pilot tone 19 kHz.

phinph.jpg (4953 bytes)   phinquad.jpg (5098 bytes)
3. RDS and pilot in-phase, 4. RDS and pilot in quadrature.

Almost anyone making RDS development and testing takes a note that there's no suitable low cost FM modulator available on the market with small output power, wideband modulation input and stable frequency. It has been discovered that – with some limitations – commercially available mp3 transmitters can sometimes provide the same functionality. Download this application note describing such solution.

First of all, the transmitter must provide appropriate input for the RDS signal. This is usually marked as SCA, MPX or RDS input, and the connector is BNC type. Many cheap stereo transmitters have no input provided for the RDS encoder connection. In such a case it's not possible to connect any RDS encoder. For FM broadcasting purposes strongly recommends not to buy any FM transmitter which has only audio right and audio left inputs.

If you do not use separate audio processor (stereo encoder), the transmitter should be equipped with pilot tone or MPX output, to meet the requirement of phase synchronization. All our RDS encoders are able to operate without the synchronization signal but such mode of operation is not recommended for stereo broadcast. For FM broadcasting purposes strongly recommends not to buy any stereo FM transmitter which does not provide the pilot tone or MPX output.

The usability of the FM transmitter, as well as its extensibility and audio performance, is usually proportional to the number of inputs/output provided. allows you to save a lot on the RDS encoder, while keeping all commonly used RDS services and functions, but you should never save money on choosing the FM transmitter because this is the basis of whole broadcast chain.

P232U, P164 and others - What are the differences?

To cover current market needs we produce different RDS encoder equipment. Following table introduces the main differences and specifics.

RDS Encoder P232U P164 P232 P332 P132 PIRA32 MicroRDS
Product status In production In production In production (module only) Sold out Sold out Sample design only Sample design only
General Comparison
Device characteristics FM broadcast RDS encoder with two independent communication ports FM broadcast RDS encoder with two independent communication ports FM broadcast RDS encoder with two independent communication ports FM broadcast RDS encoder with up to four independent communication ports FM broadcast RDS encoder with up to four independent communication ports FM broadcast RDS encoder with single communication port Simple RDS encoder module with only basic set of features
Stand-alone operation Yes Yes Yes Yes Yes Yes Yes
Suitable for mono / stereo transmission Yes / Yes Yes / Yes Yes / Yes Yes / Yes Yes / Yes Yes / Yes Yes / Yes
Plug and go Yes Yes Yes Yes Yes Yes No
Control and Communication
Communication ports RS-232 and USB Ethernet and USB RS-232 (one is internal) RS-232 and Ethernet,
4 ports total
USB and Ethernet,
4 ports total
RS-232 IIC or RS-232
Communication protocols ASCII, UECP, X-Command, RDS Spy ASCII, UECP, X-Command, RDS Spy ASCII, UECP, X-Command, RDS Spy ASCII, UECP, X-Command, RDS Spy ASCII, UECP, X-Command, RDS Spy ASCII, UECP Binary protocol only
Addressing at the protocol level UECP and X-Command UECP and X-Command UECP and X-Command UECP and X-Command UECP and X-Command UECP and ASCII N/A
Free format group buffers
(Immediate / Circular / UECP FIFO)
1 / 16 / 12 1 / 16 / 12 1 / 16 / 12 1 / 16 / 12 1 / 16 / 12 1 / 16 / 4 1 / 1 / 0
Windows control software Magic RDS 3
Magic RDS 4
Magic RDS 4 Magic RDS 3
Magic RDS 4
Magic RDS 3
Magic RDS 4
Magic RDS 3
Magic RDS 4
Magic RDS 3
Magic RDS 4
Tiny RDS
Magic RDS 4
Embedded configuration website N/A Ethernet Status N/A Yes Yes N/A N/A
Support for LCD display Yes Yes Yes Yes Yes Yes No
Analog Interfacing
MPX input, switchable loopthrough mode Yes Yes Yes Yes Yes Yes No
Pilot sync. capability Full, from pilot tone or MPX Full, from pilot tone or MPX Full, from pilot tone or MPX Full, from pilot tone or MPX Full, from pilot tone or MPX Full, from pilot tone or MPX Pilot only
RDS level control Software Software Software Software Software On-board trimmer On-board trimmer
Text Capabilities
Fixed set of text messages Yes Yes Yes Yes Yes Yes No
Total text capacity 25 kB 25 kB 25 kB 25 kB 25 kB 25 kB 0.15 kB
Dynamic/scrolling PS Yes Yes Yes Yes Yes Yes Yes
Support in broadcast automation systems Excellent Excellent Excellent Excellent Excellent Excellent No direct support
Other Features
Weekly scheduling Yes Yes Yes Yes Yes Yes No
Direct support for advanced services
Yes Yes Yes Yes Yes Yes No
Special features Optically isolated bidirectional RS-232 port,
supports RDS2 data-stream (since 2021)
Supports RDS2 data-stream Optically isolated bidirectional RS-232 port,
supports RDS2 data-stream (since 2022)
Optically isolated bidirectional RS-232 port - - -
What's the difference between the P232U and P164?

The P232U does not have Ethernet connectivity but has extra RS-232 port. The P232U has front panel LCD for showing status information. Other functions and features are identical. Both devices use the same firmware and Windows control software.

(C) 1999-2024 All rights reserved.