DSD+ SDR# and I'm just lost

[kc5qih]

Okay guys i'm sure this answer is buried somewhere in this forum but i'm pretty much at a loss. I have configured SDR #, and DSD+ the way I've been reading it to be done. I have the VB Cable as the output and have tuned to what I know to be the voice channels of the Waco PD P25 system, now i'm not sure if it's Phase I or Phase II so I switched to another smaller agency here close that according to the radio reference database only has the one voice frequency at 154.355 and a primary control channel along with alternates which makes no sense to me. Anyway I'm not hearing anything at all when i'm listening to the Waco frequencies or the LLPD frequencies even though I see them on the scope on SDR #. Below is how I think it should be set up.

Would it just be silent until a voice call comes through? And when I switch it to the Baylor PD MotoTRBO frequency and I get the 2nd one. I am, at this point baffled as to why i'm not hearing jack. Any ideas?

 

[Voyager]

The scope is showing the data which may not be voice data.

I don't see the DSD Interface on your SDR# which makes things run much smoother. It also allows you to mute the receiver and control the voice via the standard windows volume control.

You're also getting a lot of errors which means your levels may be off.

Last, if your target is DMR, set the bandwidth to 8000 (not 12000). While it won't make it not work, it will work better with the appropriate bandwidth.

I would also drop the order down as much as you can.

 

[kc5qih]

I've adjusted some levels and now this is what I get. It just seems like something is off. I mean i'm getting the data but no voice is coming through on it and it should be a voice frequency as opposed to a control channel. Is it possible this is phase II and DSDPlus will not decode the voice?

 

[slicerwizard]

SDR# volume control is set much too high.

RF noise floor is ridiculously high.

 

[kc5qih]

SDR# volume control is set much too high.

RF noise floor is ridiculously high.

I will adjust that next. This whole process has been quite the learning experience. So would the high RF noise floor cause that issue with DSD Plus? I mean it's obviously decoding something I'm just not getting any audio from it.

 

[kc5qih]

So I've tweaked a few things and this is what i'm getting now. I'm going to assume this is a control channel although when I click on the other frequencies on the scope it's still just the digital hash sound with no voice being decoded at all.

 

[kc5qih]

well I finally have some audio being decoded. Looks like it was an audio issue. I brought the gain back and the audio output back substantially and the signals started decoding, well some of them. There is one I see now that has constant errors although i'm not sure who it Is.

 

[kc5qih]

okay one more question. I have finally got the thing to decode digital voice however i'm hearing the digital carrier below the voice. Is there a way to mute the digital carrier so that all i'm hearing is the voice part. The digital buzz is someone annoying.

 

[Voyager]

That's what the plugin will do - separate the raw decoding from the voice encoding.

Read post #2... " It also allows you to mute the receiver and control the voice via the standard windows volume control." which is exactly what you're asking about.

I will also note that in your post 7 the signal is MUCH stronger than in post 6. That may be why it's working better, too.

 

[slicerwizard]

well I finally have some audio being decoded. Looks like it was an audio issue. I brought the gain back and the audio output back substantially and the signals started decoding, well some of them. There is one I see now that has constant errors although i'm not sure who it Is.

Your 4 level signal doesn't look like one - it's that badly distorted. It's just a wavy line; I certainly couldn't identify it as 4 level data. The error rates are going to be too high to decode voice.

Your screenshot doesn't show important stuff like I/Q sampling rate, bandwidth or noise filter setting.

Since you're using one of the inexpensive dongles, I'd just recommend using FMP instead of SDR#. It doesn't have very many options to set or get wrong.


This is 4 level audio - NXDN96, same as your signal. The white lines are approximate decision point levels; they show which of the four states each symbol has. I can't do that with your raw audio display.