ну идея как раз та что я описал
Autotuning
RDS brings intelligence into the tuning of a radio. The autotuning facility comes into its own on long journeys when the car moves from the service area of one transmitter to the next. Without RDS the radio has to be manually tuned to the next station. This is not always easy because it is difficult to reliably detect which is the strongest station.
An RDS set will look for the Programme Identification or PI code. A national network will be broadcast from a large number of different transmitters around the country. The station or network eg Radio 4 will have its own PI code. When the radio moves out of the range of one transmitter the radio will seek the strongest signal which has the same PI code, allowing the radio to remain tuned to the same programme.
When radios fitted with RDS store a station frequency, they also store the PI code along side it. This has the advantage that when the radio is turned on in a place outside the coverage area for the transmitter frequency which is stored then the radio will seek the strongest signal which has the correct PI code.
Local radio stations also have a PI code. In view of the local nature of these stations the PI code works slightly differently.
If the station has two or more transmitters then the PI code will operate in the normal way when it is range of these transmitters. However when the radio moves outside this coverage area it will retune to the strongest signal of the same type of station.
The PI code consists of four characters. The first indicates the country of origin and for the UK this is C. The next one indicates the type of coverage. The figure "2" indicates a national station, and the final two characters are the programme reference. For example Radio 3 has the PI code C203 and BBC GLR has C311.
RDS instant tuning
It takes a number of seconds for the radio to search for the strongest signal with the correct PI code. During this time the radio would mute itself and the listener would have an annoying gap in listening. To enable the set to tune itself very quickly from one transmission to the next each transmitter broadcasts a short list of frequencies of adjacent transmitters. This vastly reduces the amount of seeking which the radio set has to perform. In addition to this a second front end is often employed to constantly detect the strength of the alternative frequency transmissions. This results in much faster changes in setting - to the extent that the listener should not be able to detect when the radio changes from one transmitter to another.
Another facility associated with tuning is called the Programme Service Name (PS). This enables the set to display the station name. This normally takes a second or two to come up on the display after the station has been tuned in. However it is a most useful facility with the ever-increasing number of stations on the air
http://www.radio-electronics.com/info/broadcast/rds/radio-data-system-basics-tutorial.php
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