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RDS subcarrier protection for audio beyond 16 kHz
https://forums.stereotool.com/viewtopic.php?f=16&t=15073		 Page 1 of 1
Author:  audio [ Wed Mar 15, 2017 3:16 pm ]
Post subject:  RDS subcarrier protection for audio beyond 16 kHz
When feeding FM stereo encoder + RDS on ST with an audio which its bandwidth (lowpass) is higher than 16kHz, the stereo subcarrier will interfere with RDS (especially at around 54kHz)

The Omnia9 encoder does not do this. When I feed my audio through (it is lowpassed at 17kHz), the lower sideband of the stereo subcarrier extends normally down to 21kHz but the upper sideband stops at 54kHz. (ST encodes all the way to 55kHz, which interferes with RDS)

Maybe this is a modified version of single sideband? It would be really great to have an option to limit the upper stereo sideband to 54kHz in ST. ;)
Author:  hvz [ Wed Mar 15, 2017 6:14 pm ]
Post subject:  Re: RDS subcarrier protection for audio beyond 16 kHz
Hi Audio,
I could add this, but I'm not sure how useful it is... A receiver needs to lowpass filter the demodulated L-R signal anyway to remove the RDS audio - radio's that don't will be playing RDS above about 16.4 kHz.
Author:  audio [ Sun Mar 19, 2017 3:04 pm ]
Post subject:  Re: RDS subcarrier protection for audio beyond 16 kHz
The problem with high bandwidth audio (16.5-17.5k) is that it freaks out some RDS receivers when highs interfere with RDS subcarrier.

I'm aware that there will be some dBs of stereo loss on highs when doing this but the only option I have to avoid the RDS decoder problem for now is by using single sideband. There isn't an option for double sideband yet.
Also many receivers can decode mono and stereo without RDS up to 17k so even if there's some stereo lossage when using RDS, I think it would still be benifitial to have such an option in a stereo encoder.
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