Weird DMR Issues

Since I've been playing with DMR, I've noticed a few strange problems that seem to appear with some of the TRBO systems I've been monitoring. I will occasionally get an already-saved (and text tagged) TGID as a new TGID when the system is set to "ID Search". Also, I entered one DMR frequency as a conventional channel, and the scanner will stop on the frequency for two to three seconds, show all zeroes in the TGID/Slot/Color Code readout, and then resume scanning. I know this particular frequency (for the local school busses) can be monitored, and the scanner will occasionally decode the signal (briefly), but most of the time it'll come up as dead air with the data showing all zeroes.

mfn002 said:

Since I've been playing with DMR, I've noticed a few strange problems that seem to appear with some of the TRBO systems I've been monitoring. I will occasionally get an already-saved (and text tagged) TGID as a new TGID when the system is set to "ID Search". Also, I entered one DMR frequency as a conventional channel, and the scanner will stop on the frequency for two to three seconds, show all zeroes in the TGID/Slot/Color Code readout, and then resume scanning. I know this particular frequency (for the local school busses) can be monitored, and the scanner will occasionally decode the signal (briefly), but most of the time it'll come up as dead air with the data showing all zeroes.

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I've been having similar problems with my 436HP, mainly on CAP+ systems. I can lock out all the known talkgroups and then set the scanner to ID search, and sometimes it will come up with a talkgroup (same radio id's and conversations) of a different talkgroup number of one I know I locked out. It's like it is simulcasting it on several talkgroups at once. BUT, my TRX-1 does not pick up the new talkgroup, just the old one. Same story with DSD+. Something is still not right with the DMR firmware, I'm using V1.11.17.

I've also had all zero readouts in conventional, but I think it's mainly due to a weak signal at times. Digital is very picky about the signal strength to decode correctly.

mfn002 said:

Also, I entered one DMR frequency as a conventional channel, and the scanner will stop on the frequency for two to three seconds, show all zeroes in the TGID/Slot/Color Code readout, and then resume scanning. I know this particular frequency (for the local school busses) can be monitored, and the scanner will occasionally decode the signal (briefly), but most of the time it'll come up as dead air with the data showing all zeroes.

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You left out the bit where you explain how you know that the "dead air" is actually voice calls. Why can't it be data calls (AVL, for example) ?

On recording playback, I have had several episodes where the radio is displaying a system name, the talk group tag that would be associated with that TG if it was on that system, and a unit ID. The TG and unit ID belong to a totally different system. I have seen this happen with my connect plus systems. In almost all cases, there is no such TG on the system it is displaying. In all cases the unit ID showing up belongs with that TG on a different system. The radio traffic also matches the correct system for the TG. Can't say I have seen this happen with live scanning.

While using Proscan for logging I have seen several false talk groups show up. In almost every case there is no audio associated with it. This happens with Capacity Plus systems. I am generally not in good coverage of a capacity plus system at home, so I cannot say I have seen this during live scanning.

On recording and live scanning the unit ID displayed may not change with every new transmission. At times the same for the whole time. Other times it does change with every new transmission. This is true even on systems I have a very good signal. Not so good that it would overload though.

LCN finder performance on capacity plus is a 50/50 proposition at best. I was at The Paint Bucket (PPG Paints Arena) tonight. LCN finder stayed on 0/4 when I had it on for over 10 minutes. There was a lot of traffic on the system. Just for the heck of it I ran this experiment with the attenuator on, and off.

Set digital threshold mode to manual and then raise the threshold level to a higher value until false decodes are gone in those sites or systems.

/Ubbe

slicerwizard said:

You left out the bit where you explain how you know that the "dead air" is actually voice calls. Why can't it be data calls (AVL, for example) ?

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Well, I don't know exactly what to call it, but the scanner will stop on the channel for a few seconds but there will be no audio. I don't think it has anything to do with data calls or something like that because it seems to happen all the time, even late at night. I forgot to mention that the frequency I'm talking about is VHF. I tried entering it in as a trunked system, but I don't pick up anything at all if I monitor it that way. I think I forgot to mention that the scanner I'm referring to here is a 536.


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If it is a frequency on a Capacity Plus system, that is pretty normal. It is typical for there to be a periodic data burst on CAP+ frequencies.

Here's a photo of what I'm talking about.

I noticed that the "S" value will fluctuate between 0 and 3.


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UPMan said:

If it is a frequency on a Capacity Plus system, that is pretty normal. It is typical for there to be a periodic data burst on CAP+ frequencies.

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I was thinking that, and I noticed on the FCC license for this system that there are two frequencies. When I entered it in as a CAP+ system, I used the LCN finder to figure out what the LCNs were. Unfortunately, it only was able to get an LCN for one of the frequencies, despite leaving the LCN finder on the system for at least two hours straight. I entered in the other frequency as a conventional channel, and I got the same pause as the first.


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Capacity + system will only find the LCN for a freq when it gets voice traffic. The voice frequency will only change if there are 2 simultaneous calls on the system. Otherwise, the VC just flips back and forth between the 2 slots on the current frequency.

Example:

Frequency 1, Slot 1 (F1S1): Rest Channel
F1S2: idle
F2Sx: idle

One voice comm comes in:
F1S1: Voice traffic
F1S2: Rest Channel
F2Sx: idle

Voice comm ends:
F1S1: idle
F1S2: Rest Channel
F2Sx: idle

Next voice comm starts:

F1S1: Rest Channel
F1S2: Voice traffic
F2Sx: idle

This can go on for many hours until, finally, while there is already some voice traffic a new call begins at which point:

F1S1: Voice Traffic (existing call)
F1S2: Voice Traffic (new call)
F2S1: Rest Channel
F2S2: idle

LCN finder is still not working very well for the capacity plus systems. I was at PPG Paints arena. Placed the 436 in LCN finder. The radio remained on 0/4 after 10 minutes. I know I had good signal. The system sis for the facility only. I tried this with attenuator on and off. The radio failed to find a single LCN. There was active traffic on the system. There was a hockey game that night. I was receiving the system quite well, with decoded audio, TG and Unit ID info.

Why doesn't the LCN finder use the data on the data blip? This is a question for both DMR and analog LTR systems.

k3fs said:

LCN finder is still not working very well for the capacity plus systems. I was at PPG Paints arena. Placed the 436 in LCN finder. The radio remained on 0/4 after 10 minutes. I know I had good signal. The system sis for the facility only. I tried this with attenuator on and off. The radio failed to find a single LCN. There was active traffic on the system. There was a hockey game that night. I was receiving the system quite well, with decoded audio, TG and Unit ID info.

Why doesn't the LCN finder use the data on the data blip? This is a question for both DMR and analog LTR systems.

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That's the same problem I'm having here. I left the 536 on LCN Finder for over 6 hours yesterday and got only one LCN identified.

As for using the data blip, if I recall correctly, my RS PRO-97 used that to ID LCNs on LTR systems.

I seem to be having the same issue with Connect Plus systems displaying an incorrect TGID, and the same issue with One Frequency systems as well. This is the first I've heard of anyone else having this issue, so I'm glad that I'm not just losing my mind. I've also been having similar issues with the LCN finder on Cap+ systems, but the explanation that UPMan gave fits with what I know about the systems.

Was the incorrect TGID it was giving 2000? If so, that's the issue I'm having. I noticed that it will do it even with TGs that have already been identified.

I haven't gotten 2000, I get TGIDs both already added and unknown. For example, TGID 137 is a taxi company and 140 is security for a condo complex. 137 has already been entered into my favorites list whereas 140 is not. Occasionally I'll hear conversation that is clearly coming from 137, but the scanner is displaying TGID 140 on the screen and vice versa.

...Which would be another issue I've had.

From what I saw, it looks like you are trying to monitor the system in conventional mode instead of DMR One frequency or MotoTRBO. I don't believe LCN Finder will work unless it's programmed as a MotoTRBO system, not conventional. This will cause the issues you are seeing. I also have one of my MotoTRBO systems in a separate FL key to search for new talkgroups, but for primary listening, I have it programmed as MotoTRBO.

If you're programming a MotoTRBO system, try to first program the LCN by lowest to highest frequency and see how that works. Make sure it's in ID Search mode unless you know the Talkgroups for certain.

werinshades said:

From what I saw, it looks like you are trying to monitor the system in conventional mode instead of DMR One frequency or MotoTRBO. I don't believe LCN Finder will work unless it's programmed as a MotoTRBO system, not conventional. This will cause the issues you are seeing. I also have one of my MotoTRBO systems in a separate FL key to search for new talkgroups, but for primary listening, I have it programmed as MotoTRBO.

If you're programming a MotoTRBO system, try to first program the LCN by lowest to highest frequency and see how that works. Make sure it's in ID Search mode unless you know the Talkgroups for certain.

Click to expand...

I have it entered as a CAP+ system and have it on ID Search. I only had it entered as conventional because that was the only way I could (sort of) monitor it. I'm having the same LCN Finder issues that k3fs mentioned earlier.

LCN finder will only go to systems that you have programmed as a trunked system. It will not allow you to attempt to analyze a conventional system.

The systems I have been trying with little success are capacity plus. There is activity on the frequencies. The LCN finder fails to find ANY LCNs after several minutes to hours.

There is a one channel DMR capacity plus system, that it has failed to find the LCN as well.

Guessing will only lead to you receiving those frequencies you guessed correctly. Since the 436 does not show frequency information, it can be very difficult figuring out which ones you got right. Proscan has been very helpful, since it shows frequency info. I have also resorted to setting up different sites for the same system, with the frequencies given different LCN values. Again, without frequency information to help, figuring it out this way still remains difficult.

Attempting to monitor a capacity plus system as conventional would likely lock the scanner on the active frequency, if there is any delay set on the channel. The active channel on a capacity plus system sends out a data burst about every second.

In addition the promised advanced analysis features for P25 are still undelivered. The radio also lacks IF output or control channel output that would allow the use of additional software.

When there is a problem, admit it as soon as possible.

Customers are not stupid. Ignoring or denying a legitimate problem is not the way to handle it.

I don't think I made myself crystal clear, but I am NOT monitoring it as a conventional channel. I have the system set up as a Capacity Plus system, and have been running the LCN finder on it. So far, I have been only able to identify one of the LCNs, despite running the LCN finder multiple times for extended periods of time.