DSD+ & DSD 1.6 Unable to decode

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56FIN93

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Hi, i have this annoying problem with DSD+ and 1.6. In 1.6 i get garbled sound and in DSD+ there is no audio. I ran out of ideas. DSD+ -fa shows that signal is -DMR but in 1.6 it is +DMR. When i change it to
-DMR in 1.6 there is no audio. And yes everything is set to 48 kHz, default playback device is speaker and default recording device is virtual cable. I made .bat file for DSD+ (start dsd -i1M -o1M -fa).
Signal is coming over 73 miles (117 km) away from Estonia.




Thanks
 

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56FIN93

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Porvoo KP20TJ, Finland
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Hi, i have this annoying problem with DSD+ and 1.6. In 1.6 i get garbled sound and in DSD+ there is no audio. I ran out of ideas. DSD+ -fa shows that signal is -DMR but in 1.6 it is +DMR. When i change it to
-DMR in 1.6 there is no audio. And yes everything is set to 48 kHz, default playback device is speaker and default recording device is virtual cable. I made .bat file for DSD+ (start dsd -i1M -o1M -fa).
Signal is coming over 73 miles (117 km) away from Estonia.
Video : https://www.youtube.com/watch?v=dY8IKLvlefg&list=UUEzeTP2EngABkvgS7n6FThA
 

EricCottrell

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Hello,

Likely a marginal signal to start with, so do not expect to decode much.

The DMR voice sync is inverted DMR data sync, so you will get voice sync using one polarity and data sync using the other. DSDPlus has an automatic polarity feature. With dsd you need to add the -xr option to invert the sync. Using the -xr options depends on the receiver and sound card. On my Icom R2500 I have to use the -xr flag on VHF/UHF, and leave it off on 800/900 MHz.

I would say the DSD+ polarity is correct from seeing the Slot idle messages. A repeater will output these during hang time, or every minute or so if it is a IP-Connect repeater. The other messages are corrupted Slot idle messages due to the weak signal or interference.

73 Eric
 

jhampton2000

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Agreeing with Eric, this looks like your setup will decode this correctly as -DMR polarity. The number of ERR's on your youtube video suggests a very weak signal.

I might also suggest you run DMRDecode on this signal - it sounds like it might have privacy enabled (but it's hard to tell conclusively given the poor decode performance)

Also try the -fr switch on DSD+ for better decodes of DMR
 

EricCottrell

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This is the best signal i can receive : https://www.youtube.com/watch?v=3gEQfZ6TNgg&feature=youtu.be
Both VHF & UHF signals are coming from Estonia via inversion layer over sea. Common almost every night after over ~23-25°C hot day. After 7-8 AM (GMT+3) it dissapears.
Hello,

That is data and not voice, so -DMR is the correct polarity. If it is continuous, then it is likely a Tier 3 (Trunked) or Mototrbo Connect Plus control channel.

The DMRDecode screenshot appears to also be in the wrong polarity. DMRDecode has an invert setting in the menu, Voice frames only have Link Control (LC) information in the CACH and having two first fragments of CSBK (Control Signalling Block) shows it is not valid.

A control channel of a Tier 3 or Connect Plus will have CSBK information in Slot 0. The system will use Slot 1 for voice and will either have Slot Idle or CSBK information when slot 1 is not in use.

DMRDecode can decode CSBK information on a Motorola Connect Plus system and I think the developers have recently started adding Tier 3 decoding. There is a Hytera Tier 3 system in a nearby state to my location, but they are not very common in the US.

73 Eric
 

56FIN93

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Why DSD 1.6 gives audio and DSD+ is silent?

So DSD cant decode these channels yet?

In VHF there are few channels with constant transmission and they are strong, but randomly trasmitting channels are so weak that waterfall just shows them faintly.
 

frazpo

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Why DSD 1.6 gives audio and DSD+ is silent?

So DSD cant decode these channels yet?

In VHF there are few channels with constant transmission and they are strong, but randomly trasmitting channels are so weak that waterfall just shows them faintly.
Too vague. What type of signals?
 

EricCottrell

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Why DSD 1.6 gives audio and DSD+ is silent?

So DSD cant decode these channels yet?

In VHF there are few channels with constant transmission and they are strong, but randomly trasmitting channels are so weak that waterfall just shows them faintly.
Hello,

DSDPlus can automatically detect the polarity and in this case determines it is data. You have to use the -xr command line option to invert the signal in DSD 1.6. If you use the same polarity with DMRDecode, then you will see any decoded data.

73 Eric
 
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