DSD+ and DMR Simplex

[dtscho]

A hotel in Richmond, VA recently switched to what I believe is DMR simplex. I used DSD+ 1.074 with FMP to try to monitor and get information on color code, group, etc. The program didn't respond at all when there were voice transmissions (I saw employees talking into their radios). I checked to make sure the program was working on other DMR transmissions - everything was fine. Here are other things I did, all to no avail:

- changed the PPM correction slightly, even though it looked good where it was
- varied the gain, to make sure the signal wasn't overloading DSD+
- ran DSD+ to only decode DMR (-fr)
- ran DSD+ to decode dPMR (-fm)
- tried using SDR# to feed audio into DSD+
- tried using SDR# with "WinDSD" version 2

The audio definitely sounded like other DMR simplex audio I've heard.

Here's a link to a raw audio sample, recorded using the "R" command in DSD+:

https://www.dropbox.com/s/5nqz3s2c89oamv9/DSDPlus-Raw-Input_2015-07-13@132712.wav?dl=0

Here's the link to the FCC license for the hotel:

WQJA565 (APPLE SEVEN HOSPITALITY DBA MARRIOTT RICHMOND) FCC Callsign Details

Anyone have ideas? It was frustrating not getting any results, even while seeing people using the radios.

Thanks,
Dave

 

[SOFA_KING]

I have no experience in DSD+ or SDR, but some with DMR and simplex. So excuse me if this doesn't help...

DMR simplex (and repeater input transmissions) are pulsed TDMA of only one time slot from subscriber units, as opposed to repeaters that transmit both time slots at the same time (not pulsed, but continuous). Does SDR and DSD+ have any ability to time sync the TDMA pulses? Could that be the issue?

Phil

 

[dtscho]

Not sure, but I do know that DSD+ shouldn't have any problem with DMR simplex. I have seen it decode it. Also see this thread:

http://forums.radioreference.com/vo...e/314089-does-dsdplus-decode-dmr-simplex.html

Dave

 

[SOFA_KING]

Very good read. Thanks!

Someday I have to delve into this SDR stuff. I'm not a huge fan of needing a computer to decode digital transmissions, but if scanner manufactures don't produce the "all-in-one" solution many of us want, it may be the only alternative.

Good luck on solving your problem. Sorry I couldn't help.

Phil

 

[RayAir]

I'm using DSD+ 1.074 and can verify it will decode DMR simplex. I've tried it with my own radios and received other radios in direct mode.

It is true that you need a repeater to sync the time slots, but this is irrelevant to receiving DMR simplex.

Make sure you're receiving on the exact frequency and you have a clean audio source signal with decent signal strength.

Sometimes if I'm slightly off on the frequency DSD won't decode.

I don't have to do anything special with DSD to receive DMR simplex either. It does it fine by just opening the application.

 

[I3YBD]

Hola Dave

I can not do Donwload of audio files, by 404 not found?

Ciao Maurizio

 

[dtscho]

Hola Dave

I can not do Donwload of audio files, by 404 not found?

Ciao Maurizio

Sorry, I accidentally deleted the file. It is back now.

Dave

 

[racingfan360]

I appreciate it's not much help but:
- it does indeed sound like DMR simplex
- if it is, DSD+ should decode it ok
- I've tried your sample and have gotten nowhere. It doesn't sound/look like a great quality sample though

All my experience with decoding DMR simplex is with a tapped scanner. Has anyone tested/verified DMR simplex decoding with FMP yet?

 

[Forts]

You mentioned you were able to see staff talking in their radios... how close to them were you while recording your sample? It's possible you are too close to the transmitting radios to get a clean decode.

For example, if I start up DSD+ and key up my TRBO portable while standing on the other side of the room, it won't decode. Tons of errors. If I go outside and stand at the end of my driveway... no problem.

 

[racingfan360]

Forts...I think we're both familiar with that phenomenon. The issue with this sample from Dave is that there is no decode at all (I can get DMR decode but with lots of errors by transmitting too close to the receiver).

Dave - are you sure you're on-frequency and also what's the emission type of the channel you're tuned to?

 

[dtscho]

Yes, I thought about being too close to the transmitting radios. But the employees that I observed talking were at least thirty to fifty feet away from me, to say nothing of the employees transmitting from other floors of the hotel. As I mentioned in my original post, I also turned the gain down significantly in FMP.

Yes, I checked several times to make sure I was on-frequency. And I also tried decoding other DMR signals, and was successful. The emission type of the frequencies I was trying to decode is in the license link: 7K60FXE.

Thanks,
Dave

 

[slicerwizard]

The signal looks like typical DMR simplex, but the sync patterns don't match the DMR or dPMR specs.

 

[dtscho]

So we may be seeing a "new" type of DMR simplex. That's kind of what I was thinking after repeated unsuccessful attempts at decoding. Thanks.

DSDPlus, are you able to take a look at the recorded file in the original message and see if this is something you could add to a future release of DSD+?

Dave

 

[Forts]

Could you see what brand of radio they were using?

 

[dtscho]

Almost certain it was a Motorola. It looked sort of like an XPR3000/XPR3500, but the speaker grill was a bit different.

Dave

 

[Forts]

I should have an XPR3500 to play with next week. I'll check it out with DSD+ and see if I have any issues. Perhaps it's something to do with the 2nd gen radios supporting both time slot operation on simplex.

 

[rapidcharger]

The file won't open. Did you delete it again?

 

[racingfan360]

Dave...

>I checked to make sure the program was working on other DMR transmissions
Can you just confirm, have you been able to decode DMR simplex before using your setup?

 

[dtscho]

The file won't open. Did you delete it again?

No, it's still there. I just tried downloading, and it's working for me.

Dave

 

[dtscho]

Dave...

>I checked to make sure the program was working on other DMR transmissions
Can you just confirm, have you been able to decode DMR simplex before using your setup?

Yes, I have received DMR simplex with DSD+.

Dave