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Digital Voice Decoding Software For discussion of software applications which decode digital voice formats such as P25, NXDN, MotoTRBO, etc. Please use the HF Digital Signals forum for anything below 30MHz.

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Old 10-07-2011, 7:44 PM
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Unhappy DSD and Nexedge. Help/suggestions

I am running DSD on a Dell D600 laptop using a cheap USB sound card for input and the internal sound card for output. I have two scanners with discriminator taps, GRE PRO-2006 and PRO-2053.

This setup will decode the local 700 MHz P25 system like a champ even though my PRO-2006 will not tune exactly to the frequencies. It works remarkably well, almost as good as my PSR-600!

Now I have two new Kenwood Nexedge systems nearby. They are on 450 MHz and both scanners will tune exactly to the frequencies. I have programmed a bank in my scanner with all the frequencies in the trunked systems, identified the control channels and locked them out.

Thus far I have not gotten anything. I have tried the -fi option to force NXDN 4800. I have tried both scanners. I have fiddled with the input levels. I have cussed and threw things. I have about run out of ideas!

Question 1: When I am sitting on the control channel, should I be seeing a constant scroll of data like I do on the P25 system? I see nothing happening right now.

Question 2: Does anybody have a Nexedge system working on dsd and if so do you have any tips or suggestions that might help me out?
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Old 10-08-2011, 2:58 AM
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Is the NXDN system you are trying to decode encrypted?

Most radio shops that are installing NXDN systems are turning on the encryption option just because its there and they can.

Steven
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Old 10-08-2011, 8:48 AM
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I don't know whether either of the two systems are encrypted. Although I have got DSD to spit out a few blips that say NXDN-48 ... Voice. All I ever hear is a blurp of sound. 99% of the time the program does nothing while I hear data coming over the scanner speaker.

I figured that even if it was encrypted I would get something on the computer screen and garbled audio like I get with encrypted P25.
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Old 10-08-2011, 2:58 PM
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FWIW I have used DSD to successfully decode a lot of NXDN4800, both simplex and repeated....so it can work. I've never come across it on a trunked setup before, nor have I come across any encrypted NXDN (just encrypted TRBO which comes through as garbled audio). my setup also decodes P25, TRBO simple and repeated and NX9600. I can send you a quick recording of NXDN4800 if that helps you to diagnose the problem? whats the max sampling rate of your sound card btw?
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Old 10-08-2011, 6:40 PM
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Thanks. I don't know that the recording would help. These are trunked systems that were both installed in the last 12 months. I assume they are NXDN 4800 but have had no luck setting DSD on 9600 either.

I don't know much about this little USB sound card. It was less than $5.00 on eBay. I have tried using the internal sound card in the Dell as the input and it does not seem to work quite as well with the P25 decoding as the USB card does. I would guess that it is at least 48,000 bps. It says "full speed". :-)
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Old 10-09-2011, 2:07 PM
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I found this posting helpful in finding out exactly how my sounds card performs....Linux: How to determine your audio card's, or USB mic's, maximum sampling rate - voxforge.org

DSD really needs 48khz sampling rate to work properly, higher is better.

Jim
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Old 10-09-2011, 4:54 PM
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Thanks for that information! I did the test and it worked up to 192,000 Hz. When I tried 256,000 it gave me an invalid value error. So I think it is safe to assume this card is good up to 192,000 Hz.
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Old 11-14-2011, 12:34 PM
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I am also having trouble with a trunked NXDN4800. I would expect DSD to decode to voice channels, no such luck. DSD is working reasonably well on P25 C4FM and DMR. Now granted I know the sound card I am using is not the best in the world, what internal card is? But I would be expecting to get DSD to diplay something. I am getting nothing, not even an acknowlegement of a signal present. Other users are reporting success with 4800, but those all appear to be conventional systems. This leads me to believe that there may be a change in the frame for a trunked NXDN. Thoughts?
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Old 12-13-2011, 11:56 AM
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I'm in the same boat. All the NXDN around me (that I'm currently aware of) is trunked, and I've had *0* success with DSD on any of the channels.
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Old 12-22-2011, 10:30 AM
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I think a lot of people are incorrectly assuming that because it works with NXDN Analog, either 4800 or 9600, that it will work with NXDN trunking....

I don't beleive this to be the case, has anyone at all been able to decode NXDN Trunking with DSD? I havent heard of anyone....

It stems from the fact that the NXDN Trunking format is different then the NXDN Conventional format, the trunking format doesnt use standard RAN's like you see with conventional, you can take a NXDN radio, put all the voice channels in, and there is no way to make the radio unmute because the radio doesnt understand the trunking data in conventional mode, they are two, similiar, but different formats
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Old 12-24-2011, 10:04 AM
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Quote:
Originally Posted by VE9MP View Post
It stems from the fact that the NXDN Trunking format is different then the NXDN Conventional format, the trunking format doesnt use standard RAN's like you see with conventional, you can take a NXDN radio, put all the voice channels in, and there is no way to make the radio unmute because the radio doesnt understand the trunking data in conventional mode, they are two, similiar, but different formats
This may be true for 9600, but not for 4800. You can program a NXDN radio conventionally with RAN codes for a 4800 trunked system and it will work, I have personally witnessed it. That being said there is obviously something different in the frame between a conventional and trunked. We just need to find out what it is and hack DSD accordingly.
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Old 12-24-2011, 12:30 PM
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Interesting little tidbit, thanks for that.....will try next time i'm through an area with a 4800 system
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Old 04-05-2013, 6:41 PM
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Thumbs up usb soundcard

I was wondering the name of the usb card you are using?

I am trying to decode P25 for Chicago Fire and others with my BC 760 xlt and perhaps other analog scanners.

Thanks for your time in this manner.
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Old 04-05-2013, 6:46 PM
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DSD and NXDN trunked... Everywhere I've ever read in the forums, those who know state that DSD does not currently handle NXDN trunking, only conventional.

So, why do ya'll keep trying to beat a dead horse?

Mike
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