General Questions about DMR Systems

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Just a couple questions on DMR in general.

Did the "Color" code start out being designated in actual color names at some point or was it always just the numbers 0 - 15?

I have started out putting all my known DMR freqs in conventional mode. Some are showing up with a TG designation. Does that mean that particular freq is really part of a trunk system, or do TG's sometimes show up on conventional single channels?

Can you tell what commercial system (brand name) is in use in any way?

Some of these single freqs seem like they might be some sort of LTR system. What would that be called and is there a way to determine LCN from what is shown on the TRX-1 screen?

Thanks.
 

AggieCon

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Talkgroups are used in all DMR modes, conventional and trunked.

Trunked systems would be some version of MotoTRBO (capacity plus, connect plus, etc.).

I don't think the TRX-1 cares about the LCN order for DMR. I'm pretty sure it uses a check and move on method for each channel, comparing it to the talkgroup list.

Whistler does not have a LCN finder. I think Uniden has a live patent for that.
 
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Thanks Aggie.

How does a TG work in a conventional system?

How can one tell the difference in the type of MotoTRBO trunk systems?

Are these Moto systems similar to analog LTR's in the way they operate?

So far I have only scanned the DMR's in my area on the TRX-1 in conventional mode which seems to work fine for discovery of users and settings.
 

WA0CBW

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Talk groups would be similar to different PL codes on analog. Users in each talk group don't hear each other but only one talk group at a time can talk.
BB
 

AggieCon

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Each call is assigned to a talkgroup. So just because there is activity on the frequency, user radios don't necessarily hear the call. They hear only what they are subscribed to, just like with a trunked system. Additionally, Digital Mobile Radio uses time division multiple access (TDMA) with two timeslots (TS), so there are often two calls occurring on the same frequencies. Without a talkgroup system, the radios wouldn't know which call to receive.

I am not sure if there is a good way to tell the difference between the trunked systems with the TRX-1 (and it doesn't really change its operation either way). If you are hearing the same talkgroups and people on multiple frequencies, then you know it is some sort of trunked system. If you travel some distance and hear the same people and talkgroups on a different set of frequencies, it's likely a connect plus system.

I'm not sure exactly how the trunked systems assign the traffic. I'm not sure if they rotate through the control channels or "stack" them, using some of the frequencies only during very busy times. It seems to me like the TRX-1 does not trunk track DMR though. I think it is just decoding each frequency that breaks the squelch and seeing if the traffic matches any of the talkgroups you have programmed. If I am wrong on this, someone please correct me.

There's not too much benefit to program as a "Trunked" system unless you have a lot of talkgroups for the frequency or system. Once you have perhaps 3 talkgroups, it probably starts making sense to enter it as a trunked system (as conventional it is spending time looking for just one talkgroup -- so if talkgroup 20 is on but it's looking for the talkgroup 10 entry, it wouldn't pickup the call). On the other hand, if programmed as "trunked," it would pickup any call that you have a talkgroup programmed for.

Keep in mind that both conventional and trunked DMR can be programmed as conventional objecsts, and both conventional and trunked systems can be programmed as "trunked" systems.
 

AggieCon

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The color code is more like a private line tone. The color code keeps you from receiving someone else's system that might be on the same frequency (i.e. separate Justin's Talkgroup 1 from Redland's Talkgroup 1). Since there are two timeslots, there can be more than one simultaneous call on a frequency.
 
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Thanks to both of you on this.

I'm in a semi rural area so there isn't a lot of DMR, at least yet. One thing I have noticed is that each of the DMR freqs I have found seem to have only one talkgroup on them and they stay on that single frequency. Some seem to have the same TG on both TS1 and TS2, in some cases calling them CH-1 and CH-2.

I have listened to both the DMR and FM modes at the same time and have noticed there is a lot of digital traffic that doesn't correspond to the voice calls. I presume this is network overhead of some kind or even some sort of data traffic.

About the color codes, any idea why they called them colors? Did at one time they refer to them by color names?
 

AggieCon

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You are welcome.

The data noise you are hearing could be:

  • A control channel
  • Data only information for computers, location data, equipment, etc.
  • Voice traffic that the radio is failing to decode
I tried to look up about the color codes but couldn't find much. Unfortunately, I don't think any Motorola engineers participate on the forum. EDACS, however, does actually use color names for their color codes.
 
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Thanks much, very enlightening.

I too tried to look up the color codes before making the first post and didn't have much luck finding them.
 

N1GTL

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I could swear when I first started on MotoTRBO systems, the color codes were actually color names (red, blue, orange, etc) instead of numbers.
 

N1GTL

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I'm not sure exactly how the trunked systems assign the traffic. I'm not sure if they rotate through the control channels or "stack" them, using some of the frequencies only during very busy times.

Capacity Plus (CP) is "trunked" in that time slots can be used and shared by multiple talk groups. The default beacon time is 1.9 seconds so if you hear a data burst in that time frame, that's what you may be hearing. There is no control channel. (IPSC beacons are usually 30 seconds and conventional systems do not beacon)

If you have a CP system with a single repeater, you will always hear that beacon on the one frequency. However, a single site CP system can have multiple repeaters. That means 2 frequencies and 4 time slots. The beacon is typically referred to as the rest channel. When there is no activity, every radio and talk group is listening to the rest channel (lets say repeater 1, slot 1). Now, someone keys up one of those talk groups. Any radio on that talk group will unmute and begin receiving the transmission. All the radios NOT on that talk group will drop down to the new rest channel (repeater 1, slot 2). When the next talk group is keyed up, again, all radios part of that talk group will unmute and receive and all radios NOT on that talk group will drop to the next rest channel (repeater 2, slot 1).

This rotates continuously..... Repeater 1, slot 1. Repeater 1, slot 2. Repeater 2, slot 1. Repeater 2, slot 2. Then it goes back up to repeater 1, slot 1. If there are third and forth repeaters, it uses them too then goes back up to one. There are settings where you can pick a preferred repeater as the beacon and after a certain amount of inactivity, the beacon will move back to that preferred repeater.

So there is really no control channel in Capacity Plus, it is more of a rotating beacon that the subscribers follow. Once a talk group is done with the conversation, they will go find the new rest channel and wait for the next call.

Connect Plus uses a control channel however in this part of the country I do not think there are many, if any, control channels available so I have no experience with Connect Plus
 
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AggieCon

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Man, that's a great explanation. Thanks!

So I'm still vague on this aspect:

Does it always rotate through all of the frequencies/channels, or does it try to revert back to the default rest channel when it is open?

So if channel 1 is the default rest, does the system go back to channel 1 as soon as the call on channel 1 is over, or does it continue to rotate through the rest of the channels till it gets back to 1?

There isn't enough activity on my local Cap+ systems to figure this out myself.
 

slicerwizard

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I could swear when I first started on MotoTRBO systems, the color codes were actually color names (red, blue, orange, etc) instead of numbers.
Unlikely. Digital color codes have always been that - numbers.


This rotates continuously..... Repeater 1, slot 1. Repeater 1, slot 2. Repeater 2, slot 1. Repeater 2, slot 2. Then it goes back up to repeater 1, slot 1. If there are third and forth repeaters, it uses them too then goes back up to one.
Definitely not always the case. Plenty of Cap+ systems will leave the rest channel on the same repeater during periods of light use. Each call just pushes the rest channel to the other slot. On these systems, it takes two simultaneous calls to bump the rest channel off the repeater.


So there is really no control channel in Capacity Plus, it is more of a rotating beacon that the subscribers follow.
The rest channel acts very much like a control channel. It announces all of the active voice calls on the site. It just rotates quickly.


Once a talk group is done with the conversation, they will go find the new rest channel and wait for the next call.
No, their traffic channel tells them where the rest channel is.


Does it always rotate through all of the frequencies/channels, or does it try to revert back to the default rest channel when it is open?

So if channel 1 is the default rest, does the system go back to channel 1 as soon as the call on channel 1 is over, or does it continue to rotate through the rest of the channels till it gets back to 1?

There isn't enough activity on my local Cap+ systems to figure this out myself.
I'd say it would just keep rotating, or during light activity, it might just bounce between two slots on one repeater. Generally, it's after being idle (no calls) for a while that it'll flip back to the default/preferred channel. I haven't noticed Cap+ systems flip the rest channel back to the preferred repeater as soon as a timeslot opens up on it.
 
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All very enlightening guys. Ive had the TRX-1 for about a week now and have used it mainly in conventional mode on all of my suspected DMR freqs locally, which is actually not very many.

Interesting about the "beacons" because I do hear some freqs have regular short bursts of non voice and other with regular longer bursts.

Please comment on my presumptions below:

One of my systems is the local transit authority. It operates on one freq with TS1-CC1-TG1 as "CH-1" and TS2-CC2-TG2 as "CH-2". I presume this would be considered a conventional system. There is quite a lot of non voice data bursts on this freq that I presume to be AVL on the buses and maybe some sort of CAD or alerting data.

Another system I have is some sort of materials trucking. They appear on one freq only but the conversations occur on both TS1-CC1-TG42 and TS2-CC1-TG42 which appears to be only one "channel". Nobody else appears to be on this freq except this company. I presume this would be an example of a single frequency trunk.

Another system I have appears to be the local university. (There are two expired licenses for them on two freqs.) One of the freqs has 99% of the traffic, namely TS1-CC1-TG100 which seems to be housing maintenance. All of this traffic appears on this one freq. I have seen very quick unidentified use on TS1-CC6-TG102 only once. On the second of their freqs I have seen only one quick indication of TS1-CC1-T104, otherwise that freq seems inactive. Would this be an example of two conventional channels?

Then finally, these is what appears to be a commercial radio provider trunk system that I have seen using only two freqs. There appears to be only two users on this system locally. One is another materials trucking company. Its comms move back and forth between TS1-CC1-TG3001 on one of the freqs and TS2-CC1-TG3001 on the second freq. I presume this to be a classic wide area trunk system since the FCC license for these two freqs include several other freqs locally and at locations outside my local area. This same provider is licensed for many freqs in my area that seem to not be in use at all, or are still in use in analog radio systems.

Other than these, that's about it for DMR in my local semi-rural area. These are all 450/460 Mhz systems.

I don't think there is much, if any, NXDN in my area at this time, but I heard that another local provider is planning an 800Mhz NXDN trunk system to replace its current analog LTR system.
 
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AggieCon

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Sounds like a decent amount of activity. A lot more than what many are hearing.

The channel is determined by Time Slot and Frequency, not by talkgroup.

Single Frequency Trunked or whatever isn't a real thing. That's something Uniden and Whistler invented because their firmware is incomplete and they wanted to patch DMR on instead of starting from the beginning and implementing it fully. For instance, with Uniden, when programmed conventionally, the scanner will receive both DMR and P25 on the frequency. Whistler will not. On the other hand, Whistler supports talkgroups and talkgroup display when programmed as conventional, yet Uniden doesn't have this. It's the bare minimum to get the sale.

I suppose different talkgroups can be assigned to different resting and voice channels. But, otherwise, talk groups are unrelated to the channels.
 

Heidi750

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DMR Noise

so after hearing that ...
What I'm hearing then could be control channel bursts?

Is there a way (TGs?) to only hear the audio?
This is a small department with not a lot of radio traffic.
More noise than audio

Do I need a special setting to see the TGs?

The data noise you are hearing could be:

  • A control channel
  • Data only information for computers, location data, equipment, etc.
  • Voice traffic that the radio is failing to decode
I tried to look up about the color codes but couldn't find much. Unfortunately, I don't think any Motorola engineers participate on the forum. EDACS, however, does actually use color names for their color codes.
 

kayn1n32008

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Thanks Aggie.



How does a TG work in a conventional system?

The same as they do on a trunk system. If you do not have a talkgroup programmed in your radio on the correct slot or colour code, you will not hear traffic.



How can one tell the difference in the type of MotoTRBO trunk systems?

One Motorola system has a dedicated, constant control channel, the other type is much like LTR, in that it has a home or 'rest' channel that beacons like a LTR system.



Are these Moto systems similar to analog LTR's in the way they operate?

See above for my last answer.


Talk groups would be similar to different PL codes on analog. Users in each talk group don't hear each other but only one talk group at a time can talk.
BB


Good analogy, but if you have one talkgroup on slot 1 and another talkgroup on slot 2, you can hold two concurrent transmissions.
 

AggieCon

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To clarify: Both Uniden and Whistler scanners will receive DMR calls if programmed as conventional set to any timeslot, any color code, any talkgroup. On Uniden, it will automatically play any talkgroup and you just have to make sure you are on Color Colde/NAC search.

Capacity plus uses rest channels.

Connect plus has a control channel. Connect plus is the multi-site wide area system.

I'm not quite sure why you are hearing noise. The Whistler scanner should only play digital voice if you have the object properly programmed. Are you sure someone on a tractor isn't keying up? If it really is digital noise, make sure you don't have the same frequency programmed for a mode of Auto or FM.
 
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