MPX & RDS Setup

Some help when using Amp when stereo multiplex and RDS is enabled. I test with a Behringer UMC204HD. (About 20 years old but still manufacured.)
I also a use a Behringer bought recently the UMC202HD.The perfomance still seem the same as the UMC2024HD but it is only 2 channels out. The driver is the same for both interfaces and available from Behringer.The UMC202HD has inconvenient TRS (balanced?)outputs compared to the old interface with RCA/Phono outputs.
The inputs to both interfaces is designed for XLR balanced microphones.I use a 20dB XLR attenuator on both inputs and an RCA/Phono to XLR converter.Amazon was the source for these adaptors.

To enable stereo multiplex and RDS generation the sound interface needs to set to 192kHz sample rate.Found in the main menu under Sound Settings>ASIO Settings.

Then through the Sound Out windows use the Controls>Input>MPX+RDS Enable.

The default settings have both stereo multiplex and RDS enable.So no further setup is needed at this point.

The output level can be used to adjust deviation.

Accurate deviation setting requires a spectrum analyser.
There is control for setting the deviation this way.The trick is to use the spectrum analyser and look for nulls in the center frequency.
Start with the first null.Less of getting the wrong null.
Make sure the null is same as other nulls.(2nd & 3rd).If you see the same result then the frequency response is good to 30kHz.
The required frequency response needs to be good the 60kHz.Test equipment to verify this is very expensive.

Final step is to enable pre-emphasis in the processor (MBL5 or MBL9).

There is a MPX power controller conforming to BS.412.

Additional RDS settings are trough the main menu.