hytera trunk mode

[Asereje]

hi,since a few months i found a lot of signals in vhf here in spain, they have a lot of places and also they are very strong. Reading in the forum somebody told that is a hytera trunk system. Anybody knows a way to decode this system?. thanks

 

[Hit_Factor]

I'm pretty sure it's trunked DMR, use your typical tools. I monitor with a SDS100, haven't tried trunking with my SDR equipment yet.

 

[slicerwizard]

Anybody knows a way to decode this system?. thanks

It looks like you're already running the decoder.

 

[Ubbe]

The screen capture are full of errors and nothing can be decoded to voice by that signal.

What type of receiver are you using and how is it connected to the computer? It looks almost as if it is in the wrong polarity, that -DMR should be +DMR. Try the P key on the keyboard to switch polarity.

Push the R key to record 5 second and R again to stop recording and the resulting wav file can be run with DSDTune.exe to get the values to use together with DSDplus for best decoding quality.

If you have no success with this, can you run SDR# and record 10 seconds of IF sampling and then zip it and attach to your post?

/Ubbe

 

[Asereje]

Thanks folks for the sugestións, ill try to change the polarity. But it tells that i need to register and also the Aloha Word im a little Lost.
Im running a RTL sdr v3 and the last fastlane versión.

 

[Ubbe]

The text "required to register" are a message that systems sends out that says that radios trying to be used with the system cannot be used to even listen with until they sends its ID and gets acknowledge by the system. What I know of it's nothing that DMR systems can do. It's just bad decode quality, probably also the Aloha message are the result from bad decode.

If you manage to make an IF sample it would be easy to listen and hear if it actually are a DMR transmission and if so, what is causing the huge amount of errors in the decode. Are you spot on the frequency, are there enough bandwidth from your radio receiver, are there enough sampling rate from the computer?

/Ubbe

 

[slicerwizard]

More bad advice from Ubbe. And again, it's about DMR TIII and DSD+.

Bad decodes do not produce repeated identical Aloha messages out of thin air.

DMR signals decoded with incorrect polarity change DATA messages to VOICE messages and vice versa, so you are telling us that BOTH timeslots are carrying continuous voice but being decoded as data frames because the decoding polarity is incorrect?? And that the varying voice data (it always changes as people talk) is being decoded as identical aloha messages??? How would the 16 bit checksums be correct so often? And why is slot 1 always decoding as CSBKs (DMR control channel messages) while slot 2 is always decoding as IDLE messages, just like a real DMR TIII control channel signal does?

For reference, here's a decode of a local weak TIII control channel; it's identical to the OP's photo:

 

[garys]

When I have Polarity set incorrectly, I get no decode at all on DMR or NXDN systems. DSD-CC will recognize that its DMR, but do nothing else with it.

 

[slicerwizard]

The same TIII control channel with decoding polarity reversed:

 

[garys]

That's nice, but not at all what I see. Then again, as long as I remember to be in the correct window when I start pressing the "P" key, I don't invert polarity by accident.

 

[Ubbe]

But OP wrote it was a very strong signal?

Would be very interesting to take part of a sample of the raw signal.

/Ubbe

 

[slicerwizard]

If it is a strong signal, then something is wrong - off frequency, too much RF or AF gain, shaping filter off (or on) in DSD+, audio noise filtering enabled in SDR#, etc...

 

[Asereje]

Hi again i change the polarity and It didint change. Ill try to récord somebody tomorrow and ill add It thanks

 

[slicerwizard]

Hi again i change the polarity and It didint change.

Then you're not using a dongle with FMP24; so a dongle with SDR#? Or a discriminator tapped receiver? I'm starting to see the problem...