As most of you will be aware, it is rare for a studio to be co-located with the transmitter, particularly in countries with tight controls over antenna location such as the UK. Therefore, it is usual to have to have some form of connection between the 2 locations. Unlike SW transmitters, which can be thousands of miles from the studio, and thus use a satellite link, FM stations are typically between one and 10 miles from the transmitter. To connect the two locations, 2 methods tend to be used. One is a digital data connection, usually 2 M/bits per seconds, over copper, point to point radio or optic fibre, and this will carry the audio feed and any additional data, such as RDS and switching control. This is (without any exception I know of) what the BBC use.
However, in the commercial radio station sector in the UK, costs are paramount (I could say it shows from the programming!) and so another way has been devised, using a point to point audio radio link, which sounds perfectly acceptable, but does present one problem: There is no provision for data to be carried over it!
Thus, for FM stations who wish to use RDS (and lets face it, who doesn't, even "temporary" restricted service licence and Student stations use it these days, not to mention pirates!) there are a few problems. The main solution is to co-locate the RDS generator at the transmitter, BUT, this gives the problem, "how to change RDS data settings".
The solution? Well, the main consideration is the TP (Traffic Programme) flag, which needs to be made to change from zero to one for traffic announcements. By doing this, the receiver, if so equipped, will stop playing CD's or tapes, or if the volume is set to zero, will increase volume to allow you to hear the announcement. As I said, only audio data can be carried by this point to point radio link, so the solution is to have a 3 note multi-frequency tone (like the dialing tones on telephones) that the RDS data generator receives and recognises, changing the flag as a result, hearing the tones again causes it to switch back. Click here to hear that set of tones (22k/b Wave file) Note that the tones in this sample have a jingle in the background. By using the 3 MF tones the hope is that there will be nothing that will trigger the RDS generator to act, other than when intended. (What will happen if a major recording artist ever uses this in one of their songs will be hilarious to witness!). So, if you have heard these tones on a station near you, you now know why. There is a problem associated with this however. As this is the only data item they have control of, you will find that nothing else on the station's data stream ever changes. The PS name will always be the same, as will the PI code (Though this is unlikely ever to change unless the station is given permission to, or requested to, by the Radio Authority), the Music/Speech flag (which should be "M" if not used actively by the station, but there are some near me who are outputting "S" permanently!) the PTY code, almost always 9 - Varied, or 10 - Pop Music (They should allocate a new PTY code, for "music from the 80's, 90's and now" as this seems to be the maxim used by most UK commercial stations these days) and even the radio text, as used on receivers such as the Grundig Ocean Boy 510, will never change.
FOR ALL COUNTRIES.
In many countries, such as Turkey, Germany, and others, the PS name is used "dynamically" (against RDS forum recommendations) to provide information such as artist, song title, station info, time, date, and temperature, you will never see this in the UK, as the BBC won't do it (being major partners in the RDS forum) and the commercial stations can't do it for the reasons stated above, i.e./ no data control for the remote located RDS generator.
I have witnessed dynamic PS name in several countries myself, Turkey, Albanian, Corfu and Spain. France did not appear to be doing it, judging by my visits to Normandy and Paris in 2001. However, this use has led many people to confuse RDS dynamic PS name use, and real RDS radiotext! Even Thomas Baier, the Satellit 700 website owner thought the 700 could receive radiotext, and did not believe me at first when I told him otherwise. However, after checking with the programmer of the 700, he agreed that I was right.
This confusion over the use, and even existence of RDS radiotext even included a media lecturer at a top UK university, who knew nothing of it's presence in the data stream. Why? Well, in my opinion, in the UK, the BBC have tried not to publicise it, in an effort to force DAB onto people, as it has the facility also. Now, DAB (Digital Audio Broadcasting) has been something of a lame duck in many countries, Germany for example call it "Dead And Buried" as, after an initial buzz, most broadcasters htere have/are turning it off due to lack of interest. And with good reason: transmission range is shorter than FM, multipath is an even bigger problem, which meant that massive data checking and correction elements had to be built into the system or it would simply not work, audio quality is, at best, arguable as good as FM, but more often it is much worse, as broadcasters squeeze far too many channels (stations) onto each 2 m/bit Mux transmitter path, and if you've ever heard lower than 200k/bit per second MP3 files, you know how bad they can sound. And DAB used the inferior MP2! Even the BBC have been known to drop as low as 60k/bit per second. The BBC are known to "juggle" the data rates on their mux paths to fit them all on, maximum space is ususally given to Radio 3 (as their listeners are more discerning) and the others are allocated bandwidth on the basis of need, ie/ is the programming music or speech Incidentally, the BBC often use MP2 or 3 files of reports from location in their radio news programmes, I can almost always tell those that have been sent thus, when listening on any fairly decent FM radio!
Now, back to what RDS CAN do! Time setting of your radio clock? Yes, if the radio is so equipped, like the Ocean Boy 510, it will update the clock and day of week, and also adjust itself for Daylight Saving Time.
Radiotext? That is available too, although the BBC, as I said above, keep very quiet about it.
Here's a video of the Ocean Boy 510 receiving Radiotext at the end of BBC Radio 4's "Just a minute" programme, as it's about to lead into the "Food Programme"
You can speed up the text scrolling on this model by holding down the "text" button.
Also, the model shown has Full EON traffic announcement and Programme Type display and search. I'm no expert on DAB, but I'm not sure even it has both of these?