No audio output from DSD+

[K0EKL]

I'm attempting to use Unitrunker-1.0.32.7 and DSD+ 1.101 to monitor the "ARMER" P25 system in Minnesota. (I'm already using a Uniden BCD396T to monitor the same system.) I'm using a laptop running Win 10 64 bit with 8 GB ram.

I have Unitrunker working with a single RTL SDR stick configured for 2 VCOs. I have the TGIDs imported into Unitrunker from Radio Reference. Unitrunker shows 100 percent health in the site window and I see every call that comes in. I'm listening simultaneously on the Uniden and can see that the calls and TGIDs shown in Unitrunker match up with what I hear on the Uniden.

I'm using VBCable to feed digital audio from the voice VCO digital output to DSD+. VB Cable is the default input device and my laptop's speakers are the default output/playback device. Input and output levels are all set to 50 in Windows volume control.

As a call comes in I see scope activity in DSD+ but at most I get a second or two of garbled sound. Maybe one out of 50 calls results in a bit of audio.

With each call DSD shows text like this:

SYNC25p1 NAC40D TSDU
NO SYNC

or

SYNC25p1 NAC40D TDULC
NO SYNC


So, what am I doing wrong? What do I need to do to fine tune DSD+?


Thanks

 

[baustm]

Yeah, this just sounds like DSD is being fed bad audio. A couple things I can think of would be the gain and the correction for your RTL. A screencap of your Unitrunker settings for the voice VCO would also be helpful.
You could also try lining up the scope on Unitrunker with the scope from DSD, and see if there is any visible clipping on either side.
From my experience you don't really need to tune DSD+ for P25 to get decent quality, it's mostly on the receiving side that the traffic gets messed up.

 

[K0EKL]

Screenshots

From top to bottom these are screenshots of the Receiver, Signal VCO, Voice VCO, Voice scope and DSD+ scope.

 

[slicerwizard]

You're dealing with PSK signals. Tell DSD+ to use its PSK optimizations. But don't get your hopes up too much.

 

[SCPD]

NooElec SDRSmart

Please consider the NooElec SDRSmart for $30 it has a 0.5ppm TCXO. You even get 3 antennas that actually work well. You can leave Unitrunker to 0.00000ppm but still have auto correct turned on with squelch 40 or higher .It will hold at 0.00000 or on days with changing ambient temps it maxes 1.40000ppm.

99% of the time it stays at 0.00000. Just order one for your voice role. The signal role is less finicky in terms of control data decoding because its just the data control channel for the system. It sure did help me. Just passing on the knowledge.

Voice Role needs to be on top of the game when you use digital speech decoder (DSD). Precision is the game. Not down played. Not hyped. It is what it is.