P25 DSD+ decoding

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pclever
Posts: 3
Joined: Thu Sep 13, 2018 5:07 pm

P25 DSD+ decoding

Post by pclever » Thu Sep 13, 2018 5:13 pm

Hello, I have been trying to use DSD+ to decode some digital P25 phase 1 frequencies and running in to an issue. I have tried almost everything I could find on the internet over the last few weeks and I am unable to get this set up fully working. DSD+ is running and recognizing the P25 however it is not outputting any audio. Can anyone please give me some advice on what to try next?

I have attached an image of my current set up. Thank you for your help!!
Image

rtlsdrblog
Site Admin
Posts: 1790
Joined: Mon Nov 19, 2012 11:54 pm

Re: P25 DSD+ decoding

Post by rtlsdrblog » Fri Sep 14, 2018 1:41 am

Are you sure that it's an unencrypted voice channel and not just data?

pclever
Posts: 3
Joined: Thu Sep 13, 2018 5:07 pm

Re: P25 DSD+ decoding

Post by pclever » Fri Sep 14, 2018 1:46 am

rtlsdrblog wrote:
Fri Sep 14, 2018 1:41 am
Are you sure that it's an unencrypted voice channel and not just data?
I am pretty sure, I have tried about 10 different frequencies on P25 phase 1. This one is my local police department frequency and should be open to the public (unencrypted). I am about to create my own network and I doubt I will be able to use it if I can't decode P25 now.

rtlsdrblog
Site Admin
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Re: P25 DSD+ decoding

Post by rtlsdrblog » Fri Sep 14, 2018 1:58 am

Because DSD+ looks like it receiving and decoding the signal fine, but there's just no voice activity on the channel.

If someone speaks you'll see a log entry appear in the event log, and something different scrolling on the cmd window.

I also think that "TSDU" also means that you're on the trunking data control channel, not a voice channel.

pclever
Posts: 3
Joined: Thu Sep 13, 2018 5:07 pm

Re: P25 DSD+ decoding

Post by pclever » Fri Sep 14, 2018 2:32 am

rtlsdrblog wrote:
Fri Sep 14, 2018 1:58 am
Because DSD+ looks like it receiving and decoding the signal fine, but there's just no voice activity on the channel.

If someone speaks you'll see a log entry appear in the event log, and something different scrolling on the cmd window.

I also think that "TSDU" also means that you're on the trunking data control channel, not a voice channel.
Yeah trunking looked like it could be an issue. I am still fairly new to all this, do you know how to get to the voice channel when it is being trunked?

rtlsdrblog
Site Admin
Posts: 1790
Joined: Mon Nov 19, 2012 11:54 pm

Re: P25 DSD+ decoding

Post by rtlsdrblog » Mon Sep 17, 2018 5:33 am

Check out Unitrunker and this tutorial first https://www.rtl-sdr.com/rtl-sdr-tutoria ... nitrunker/

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