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Is this DMR ?

Posted: Wed Mar 18, 2020 11:05 pm
by TA2ISO
OpenGD77 decodes some talk groups and ids but there is no audio.
gqrx_20200318_224223_425300000.zip
(232.58 KiB) Downloaded 229 times
It looks like some kind of a trunking control channel. DSD also sees it as DMR.

Re: Is this DMR ?

Posted: Thu Mar 19, 2020 12:04 am
by VK3KYY
It doesn't sound like DMR to me.

Open the file in Audacity and you'll see 2 distinct packet types.
There is a short burst and a long burst.

I don't know what this is typical of.

Try using a SDR dongle and DSD, it auto detects most modes

Re: Is this DMR ?

Posted: Thu Mar 19, 2020 12:34 pm
by kt4lh
Maybe it's Tier 3? Encrypted?

Re: Is this DMR ?

Posted: Thu Mar 19, 2020 11:39 pm
by EB3AM
TA2ISO wrote:
Wed Mar 18, 2020 11:05 pm
OpenGD77 decodes some talk groups and ids but there is no audio.gqrx_20200318_224223_425300000.zip

It looks like some kind of a trunking control channel. DSD also sees it as DMR.
Maybe Tetra?
Is constant? or is like a talk transmission? Tetra make a constant TX on the BSU...

Re: Is this DMR ?

Posted: Thu Mar 19, 2020 11:52 pm
by TA2ISO
dsd3.png
dsd3.png (270.94 KiB) Viewed 5632 times
dsd4.png
dsd4.png (249.59 KiB) Viewed 5632 times
gqrx_20200319_233419_425300000.zip
(505.23 KiB) Downloaded 200 times
This is the longer version with a different burst at the end.

Re: Is this DMR ?

Posted: Fri Mar 20, 2020 12:13 am
by TA2ISO
EB3AM wrote:
Thu Mar 19, 2020 11:39 pm
TA2ISO wrote:
Wed Mar 18, 2020 11:05 pm
OpenGD77 decodes some talk groups and ids but there is no audio.gqrx_20200318_224223_425300000.zip

It looks like some kind of a trunking control channel. DSD also sees it as DMR.
Maybe Tetra?
Is constant? or is like a talk transmission? Tetra make a constant TX on the BSU...
Have`t tried decoding it with tetra, going to try with telive. i have never listened to a tetra frequency sounding like this one though.

Re: Is this DMR ?

Posted: Fri Mar 20, 2020 1:14 am
by VK3KYY
Probably encrypted audio

Re: Is this DMR ?

Posted: Fri Mar 20, 2020 9:39 am
by G4EML
Doesn’t sound like DMR. But even if it is don’t forget that DMR is not only used for voice traffic. Many systems use it just for digital data or telemetry. As previously mentioned tier 3 is trunked and so also has a control channel.

Re: Is this DMR ?

Posted: Fri Mar 20, 2020 9:52 am
by VK3KYY
There is around 10ms of audio, then a gap of around 10mS, then there is 30mS of audio then another gap of 10ms

I'm not sure what DMR looks like, does it have gaps in it?

waveform.png
waveform.png (5.61 KiB) Viewed 5598 times

Re: Is this DMR ?

Posted: Fri Mar 20, 2020 11:28 am
by G4EML
DMR from a repeater is constant, no gaps. You can hear changes in the tone when speech or data start but they are quite subtle.