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Voice/Control Channel Decoding Software - For discussion of software applications which decode digital voice formats and trunking control channels. Please use the HF Digital Signals forum for anything below 30MHz.

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Old 09-10-2017, 9:52 AM
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Question Strange DMR Channel with DSDPlus FastLane

Hi there all! Long time reader here; for years, and I learned a lot. Now I an facing a strange and interesting DMR channel which prompted me to post.

I am using the latest DSDPlus FastLane release and everything works fine decoding many DMR channels in my area and a P25 Simplex (I think) channel - but the P25 is for another post.

The DMR Channel in question is mainly data on DCC-1 and sometime Voice on DCC-5. It is strange because I cannot understand what kind of data is being sent. If it is some kind of telemetry or messaging then I am not interested at all, but if it is some kind of control channel then I am interested if I can understand the topografy of the network. Mainly there is data traffic, some time only voice, and sometimes data+voice. In the last scenario DSD+ goes mad and scrolls a lot of errors. No errors if it is only voice or only data. Voice decodes fine and clear - data scrolls without errors but I cannot understand what kind of data.

I've managed to record the raw input of DSD+ during an episode, which I uploaded to zippyshare @

Zippyshare.com - DSDPlus-Raw-Input_2017-09-10@151210.wav

Also I am attaching two screenshots. One of the signal on SDR# and the other of the DSD+ windows during the registration of the above audio file. On the second screenshot, the area with red rectangle on the DSD+ Event Log window is what it logs during the registration.

Is there anyone that can help me understand what kind of DMR Channel is this?

Thanks in advance,

Ben
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Old 09-12-2017, 7:52 PM
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Zippyshare has jumped the shark. Pops up all kinds of junk. Couldn't even get it to let me download that file.
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Old 09-12-2017, 9:17 PM
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Yep, @slicerwizard , just noticed today Zippy forces you to click endless times before letting you download the file.

Anyway, uploaded it to G-Drive:


https://drive.google.com/file/d/0B69...ew?usp=sharing


Thanks in advance!

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Originally Posted by slicerwizard View Post
Zippyshare has jumped the shark. Pops up all kinds of junk. Couldn't even get it to let me download that file.
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Old 09-13-2017, 10:40 AM
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Quote:
Originally Posted by BrinC View Post
The DMR Channel in question is mainly data on DCC-1 and sometime Voice on DCC-5.
Looks like two separate transmitters (repeaters) to me.


Quote:
It is strange because I cannot understand what kind of data is being sent. If it is some kind of telemetry or messaging then I am not interested at all, but if it is some kind of control channel then I am interested if I can understand the topografy of the network.
The DCC1 repeater seems to be sending automatic registration service (ARS) messages.

The DCC5 repeater is carrying voice traffic.


Quote:
Mainly there is data traffic, some time only voice, and sometimes data+voice. In the last scenario DSD+ goes mad and scrolls a lot of errors.
Not surprising, since the two repeaters are fighting each other.


Quote:
No errors if it is only voice or only data. Voice decodes fine and clear - data scrolls without errors but I cannot understand what kind of data.
Again, just some boring ARS data (based on the fact that the embedded port numbers are 0FA5 (4005), which is where ARS lives)
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Old 10-28-2017, 4:34 PM
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@slicerwizard, Thank You very much for your help!

Yes, indeed there "were" two different repeaters. I mean "were" because it was my fault. I was using and old RTL-SDR USB Dongle and a not-tuned antenna. Your explanation made me think and I ordered a good usb dongle and a build a better antenna.

Last week I had all assembled and after some days of head-bashing I noticed that A repeater was on it's own frequency (almost all data and rarely some voice) and the B signal was a ghost/reflection/etc from another B repeater (all voice) on another frequency. I think it was because of the old RTL-SDR Stick and the antenna. Now everything is ok and believe it or not the error rate is below 1%, so, many many many thanks again.

Anyway, yes, you are right about ARS messages "living" on 4005, but it seems strange to me and I have reasons to believe these are not just simple ARS. I am prepping and uploading some fresh and cleaner logs and recordings as I write this post, and will post those logs and link, but I will try to explain:

On the channel I have seen only three active units. RID 8, 105 and 354. Also there is RID 1 which I believe is an USB accessory (because of 13.0.0.1), it is always passive, meaning it is always the target of data communications and never the source. Those data messages targeting RID 1 are with very short intervals; once a minute or max once every three minutes. It it was an Automated Registration Service, I think the unit sends one when powered on and does not sends every minute, right? Anyway, I will post the logs asap so I can bother you again looking into it
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