Looking at how to connect up the RDS
Connecting up a RDS Generator
The RDS generator signal has to be added to the MPX stream somehow before driving the FM modulator.
The RDS Systems
Connecting the RDS generator in series with either a seperate stereo generator or one embedded in the transmitter:
The RDS generator extracts the pilot from the MPX signal in order to synchronise the 57KHz RDS carrier to the MPX, then re-injects the RDS modulation into the MPX signal. However the lower diagram also shows a possible connection for parallel RDS injection. Here a pilot reference is used form the embedded stereo generator, the RDS modulation formed then re-injected into the RDS input of the transmitter.
The serial method tends to generate more noise injection into the MPX due to the increased MPX path length and treatment. For bst results parallel RDS injection is to be preferred.
A parallel connected RDS generator when a separate stereo generator is used is shown here.
Here we have looked at the RDS generator being an independent piece of equipment but it is quite possible to embed the RDS generator into the stereo generator and the stereo generator, in turn, embedded in the transmitter. In this way the parallel connection method can be used. Elsewhere a simple RDS generator for embedding into a stereo generator is described.