TRX-1: How to decode direct TDMA?

[radionx]

Hi all

I have a single frequency UHF DMR system here. It uses SL2600 devices from Motorola, no E. Special thing: It uses only one timeslot, so if someone is broadcasting and you listen with a scanner in FM the squelch gets triggered in very short periods. I programmed it in my TRX-1 as DMR Conv...no chance. It does not decode. The signal is strong.

Does DMR simplex use 1 time slot or 2?

I have experimented with the DMR simplex modes in my Hytera portables. These are the 3 modes we are talking about here and getting them mixed up. DMR simplex modes: 1. Plain old DMR simplex mode. I don't know the exact name for it. 2.. TMDA direct mode. 3. Single frequency repeater (SFR)...

forums.radioreference.com

This kind of programming WILL get more popular in country.

Any hints?

 

[RaleighGuy]

What is your color code and time slot set as? Also have you tried the "Skip DMR Talk Groups"?

 

[radionx]

What is your color code and time slot set as? Also have you tried the "Skip DMR Talk Groups"?

View attachment 122853

Hi!

It's set to Color any and Slot any.

DG mode dig
Rx mode nfm
Sq mode none
DMR ticked
Skip Dmr Tgid selected
Agc on

One of the guys is sending 30M apart...won't decode...

 

[RaleighGuy]

Hi!

It's set to Color any and Slot any.

DG mode dig
Rx mode nfm
Sq mode none
DMR ticked
Skip Dmr Tgid selected
Agc on

One of the guys is sending 30M apart...won't decode...

And you are sure it is DMR and not NXDN, P25 or something else? Based on the settings it should work for DMR.

How close/far are you from transmitter?

 

[radionx]

Hi!

It's set to Color any and Slot any.

DG mode dig
Rx mode nfm
Sq mode none
DMR ticked
Skip Dmr Tgid selected
Agc on

And you are sure it is DMR and not NXDN, P25 or something else? Based on the settings it should work for DMR.

How close/far are you from transmitter?

Well, they use Motorola SL2600. It's DMR. They are like...50 ft away...

Should I dump this somehow for debugging?

 

[radionx]

Could it be that the TRX-1 has issues with these short lived 30ms signals with white space in between?

I left the squelch open...

It becomes VERY common on itinerant or common usage frequencies...if I cannot decode it I lose about 40% of all DMR traffic.

 

[radionx]

Hmmm...I tried with another pair of radios (Retevis). Direct Mode DMR with a S2 only emission does not get detected by my TRX-1. DSDPLUS via IF can detect some packets...but seldom.

Any thoughts?

It is a quite hard to detect signal, by the way. 30ms packet, 30ms white noise...and so on.

Maybe whistler support can tell us something?

I also think speech latency rises in this mode. Might be because of timing & reassembly.

 

[lwvmobile]

Hmmm...I tried with another pair of radios (Retevis). Direct Mode DMR with a S2 only emission does not get detected by my TRX-1. DSDPLUS via IF can detect some packets...but seldom.

Do you still have those radios and/or wav file samples from them? I'm interested in Retevis DMR all of a sudden and could use some samples from it to study it.

 

[Wackyracer]

You're over powering the trx. you should be further away then 50ft

 

[radionx]

Do you still have those radios and/or wav file samples from them? I'm interested in Retevis DMR all of a sudden and could use some samples from it to study it.

I mean, if the programmer of DSD-FME asks me something...I'm glad to help! What are you looking for?

 

[radionx]

You're over powering the trx. you should be further away then 50ft

In this specific case the reason was:

It's DCDM DMR (or direct TDMA) which the TRX-1 won't decode (I REALLY hope Whistler implements it). DSD+ can handle it and decodes it without capturing the "Timing Master Packet".

I think it's quite similar to DMRs, but something in the DMR header might be slightly different.

Another user here verified my observation.

I have no idea if the SDS 100 can handle DCDM. Another interesting question.

DCDM is quite hard to detect, I think many just overlook these signals.

 

[lwvmobile]

I mean, if the programmer of DSD-FME asks me something...I'm glad to help! What are you looking for?

Well dang, I guess I'm getting famous now
I'll PM you here momentarily about possibly acquiring some samples from your Retevis DMR radio.

 

[slicerwizard]

I think it's quite similar to DMRs, but something in the DMR header might be slightly different.

Just different frame sync patterns.

 

[lwvmobile]

Just different frame sync patterns.

You wouldn't happen to know what the frame sync pattern is by chance, would you?

 

[lwvmobile]

You wouldn't happen to know what the frame sync pattern is by chance, would you?

Okay, so I'm an idiot, its the Direct Mode sync, I got confused on different nomenclatures.

 

[XVCham]

DCDM is one of the more tricky modes to decode. I have a personal DMR T3 site that is programmed into my scanner, but I also have direct talk-around freqs for close-range comms (simplex). I use DMR DCDM on these simplex freq because of the licensing costs. While I have everything programmed into the same scanlist (I leave my scanner on scan/record 24/7 to monitor my site's traffic), the scanner simply refuses to pick up the DCDM simplex signals. Same can be said for DSD+, The raw signals do sound a little different (I might be able to get a recording of it).

 

[slicerwizard]

Never had a problem with DCDM and DSD+ FL.