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SCA Input
https://forums.stereotool.com/viewtopic.php?t=4730		 Page 1 of 1
Author:  radiofreak [ Wed Mar 20, 2013 4:10 pm ]
Post subject:  SCA Input
For some reasons, I want to try Airomate instead of the build-in RDS-encoder. So, I run the Airomate-Out (RDS only) with pilot in VAC (192 kHz of course), and then open the VAC-pipe as SCA in ST-config. In FM-Transmitter, I activated both SCA channel 1 and 2. But - nothing comes through. I then opened the RDS-VAC-Pipe for testing as the Input of ST, and - surprise - Pilot and RDS are there!

Furthermore, I want to test ST only for use as an BS412-Limiter/Stereocoder/RDS-Coder after Breakaway. What perfectly works is routing the pre-emphased L/R-Out of Breakaway over VAC in ST as the Input, defeat all things except the FM-Transmitter section (with defeated pre-emphasis of course) and ajust the BS412-section to match the incoming signal. But big problem on the Normal Out which feeds the DAB-Transmitter in my case: here, I have the pre-emphased audio. I could turn on the de-emphasing in Breakaway and again the pre-emphasis in ST to get the right Audio on Normal Out and FM, but then the double-pre/de-emph. deforms the highs too much...

So, I tried to route the whole MPX-Out of Breakaway via VAC through SCA in ST, but that doesn't work as well. Something's weird with SCA-Input...
Author:  hvz [ Thu Mar 21, 2013 10:16 am ]
Post subject:  Re: SCA Input
SCA = Side Channel, it gets encoded as an FM signal around 67 kHz. So that's not at all what you are looking for. See http://en.wikipedia.org/wiki/Subsidiary ... _authority

There is currently no way to input an external RDS signal. I should probably add that, but I don't have it yet. And there are other higher priority things that I'm going to do first. (Can you tell me what RDS feature you're missing? Assuming that that's the reason...)

About using a de-emphasized signal from Breakaway: How would that deform the highs? At least in Stereo Tool I have tested that using pre-emphasis + de-emphasis gives the original signal back, unchanged.
Author:  radiofreak [ Thu Mar 21, 2013 1:32 pm ]
Post subject:  Re: SCA Input
Once I've connected an external RDS generator to the SCA-In/Outs of a Vorsis AirAura, and it worked, so I thought I can use it for RDS in ST, too. The HPF can also be set all the way down to 0 Hz, so I thought that I can even put any signal through it ;)

Airomate allows sheduled RDS-text-changes (with the help of an additional programm). The "Smart-Split" of longer text from an external text-file works better (ST sometimes chops longer PS-texts). And besides that, Airomate is more convenient to use, especially on complexer RDS-text-setups, where you have a nice GUI with listings of your text-messages to see, reach and change within seconds.

Feeding pre-emphased audio from BBP to ST, the outgoing MPX sound is exactly the same as when Breakaway would generate the MPX. Feeding de-emph audio from BBP to ST and applying pre-emph again, I've noticed a slightly high-end-loss on the MPX. The highs are simply not as crystal clear as on the other way... Don't know if I'm doing something wrong ;)
Author:  phantomfm [ Sat Mar 23, 2013 4:45 pm ]
Post subject:  Re: SCA Input
True,

SCA (SubCArier) is used in broadcast processing to add (mix) RDS signal in the composite output.
SCA is also used to add FM EXTRA carrier.

For RDS synchronisation a 19Khz reference signal is dirived from the stereo gererator (needs to be in phase)

so yes, it's confusing, hans needs to give it a different name.

And even better, give ST a real 19Khz output, and RDS (SCA) input. :geek:
Author:  hvz [ Sun Mar 24, 2013 1:17 am ]
Post subject:  Re: SCA Input
@phantomfm: Does this mean that the RDS input is always the real RDS signal, or is there also a possibility to insert an RDS signal using ONLY the "original" RDS data without modulating it at 57 kHz?
Author:  phantomfm [ Sun Mar 24, 2013 1:00 pm ]
Post subject:  Re: SCA Input
Quote:
@phantomfm: Does this mean that the RDS input is always the real RDS signal, or is there also a possibility to insert an RDS signal using ONLY the "original" RDS data without modulating it at 57 kHz?
SCA input is always a subcarrier input, so for example a 57Khz DSBSC RDS carrier, so it needs a 192Khz pipeline (if used with AIROMATE) or 192Khz souncard input if used with external RDS encoder.
In order to SYNC the external RDS you need to apply 19Khz to the RDS system (via pipeline or soundcard output)

FMeXTRA (VuCast) can probably not be used since the subcarrier is in the 59 - 100Khz range, mm when i think about it, strange since the O9 can also be used for HD subcarriers...i think. (VuCast = HD radio)

Image

- EDIT - There sould be a SCA input for VuCast on a professional FM Exiter too.

Image
Author:  radiofreak [ Tue Mar 26, 2013 9:47 pm ]
Post subject:  Re: SCA Input
Quote:
About using a de-emphasized signal from Breakaway: How would that deform the highs? At least in Stereo Tool I have tested that using pre-emphasis + de-emphasis gives the original signal back, unchanged.
You're right. Found my mistake: the BS412-de-esser was going crazy when feeding it with a pre-processed de-emphased signal. Raising the threshold to +5 dB fixes it :)
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