DMR Talk Groups

[KK4MC]

This is more of a technical question, in general, for educational purposes.

I’m a ham who frequents ham DMR. I also have a Uniden DMR scanner.

Programming my ham DMR to work is a specific set of task (in addition to frequency….specific Talk Group, Time Slot, etc.).

My question is, how does the Uniden scanner (or any brand for that matter), know which TG, Color Code, and Time Slot necessary to load into software to open up and monitor a police or fire DMR channel? I’m monitoring a DMR county system, and of course it works, but I’m curous from a technical standpoint with thousands of combinations to chose from/set to, how the DMR scanners know without human intervention to program that specific information into the radio?

Wondering if anyone out there understands this level of technical detail.

Thanks.

 

[Gadgeteer2000]

Which scanner are you talking about? I would think the scanner as such knows nothing.
One can load frequencies, DMR TG, Color Code etc. data - after which the scanner will be able to scan. Now if you have a database based scanner - this info would come from the database. Or you can "search" for new channels and find these details for yourself. But the scanner as such does not know anything by itself...
In a way this is very similar to any analogue frequency: if you (the user) programs the frequency for the Police -then the scanner will know to listen on that frequency. If you do not know the frequency you can search for it. But by itself the scanner would not know the frequency (again -exception is database etc. scanners - but for those as well the frequencies if they are not in the database will not "exist" for the scanner, unless you search)
Not sure if this helps?

 

[Markb]

The scanner doesn't program the info, it detects it in the DMR data stream and displays the info on the screen. Programming freq, CC, Slot and TG into the radio in simple terms creates a filter so you only hear what you want.

 

[KK4MC]

It does h

Which scanner are you talking about? I would think the scanner as such knows nothing.
One can load frequencies, DMR TG, Color Code etc. data - after which the scanner will be able to scan. Now if you have a database based scanner - this info would come from the database. Or you can "search" for new channels and find these details for yourself. But the scanner as such does not know anything by itself...
In a way this is very similar to any analogue frequency: if you (the user) programs the frequency for the Police -then the scanner will know to listen on that frequency. If you do not know the frequency you can search for it. But by itself the scanner would not know the frequency (again -exception is database etc. scanners - but for those as well the frequencies if they are not in the database will not "exist" for the scanner, unless you search)
Not sure if this helps?

It does help. Made me realize the info is coming from the database (it’s a database scanner), so if I thought about it long enough I would have figured that out. So I’m now assuming the Talk Group, color code, Time Slot info must all be public information coming from the FCC database? Sounds like I need to find that database online and look at it if I want to know the programming details. I’m assuming it’s available to the general public for free?

 

[Gadgeteer2000]

I would think that the database comes from right here - radioreference.com. You can view it for free. RadioReference.com - Scanner Frequencies and Radio Frequency Reference Database

 

[RoninJoliet]

The data stream must be the correct answer to this as the 996p2 scanner shows you the DMR type, CC and Slot , then you can program it in to your liking.....Some systems have multiple CC

 

[sallen07]

So I’m now assuming the Talk Group, color code, Time Slot info must all be public information coming from the FCC database?

You won't find *any* of that information in the FCC license database. You'll just see a listing that shows DMR as an accepted emission type for the frequency.

 

[sallen07]

Programming my ham DMR to work is a specific set of task (in addition to frequency….specific Talk Group, Time Slot, etc.).

My question is, how does the Uniden scanner (or any brand for that matter), know which TG, Color Code, and Time Slot necessary to load into software to open up and monitor a police or fire DMR channel?

To answer your original question, it's called promiscuous mode. Many (most?) DMR ham radios have that too, although they may call it "digital monitor" or something else. That's what a scanner will do, unless you specify otherwise. Promiscuous mode just means, "listen to any DMR traffic on this frequency, ignoring CC, TS, TG". (Actually I'm not 100% about CC.) You don't really *need* the correct CC, TS, TG unless you want to transmit.

 

[KK4MC]

I did not know that. I will look into that on my ham DMR radio. Just want to monitor public service without need to carry scanner, no interest in transmitting of course. Thank you for this info.

 

[Gadgeteer2000]

I did not know that. I will look into that on my ham DMR radio. Just want to monitor public service without need to carry scanner, no interest in transmitting of course. Thank you for this info.

The challenge I see (for myself) that to use DMR on a ham radio (strictly for receiving) one needs to have a call sign, even if you never transmit. I also would like to do what you mention ( do not have call sign yet - studying now to take test) - use a DMR HAM radio (which I have) to receive only. But AFAIK you need a DMR handle, which you can get only with a valid call sign.

Or is there maybe a "receive only" DMR handle (which is accessible without a valid HAM Callsign) one can use for monitoring?

Any insights related to that would be truly appreciated!

 

[dave3825]

You don't really *need* the correct CC, TS, TG unless you want to transmit.

You need color code if there are other users that use the same frequency.

The challenge I see (for myself) that to use DMR on a ham radio (strictly for receiving) one needs to have a call sign, even if you never transmit.

Or is there maybe a "receive only" DMR handle (which is accessible without a valid HAM Callsign) one can use for monitoring?

If you are only receiving, you do not need a call sign. You can own as many ham radios as you want without a call sign if you are never going to transmit.

If you are going to transmit, than legally you would need a call sign.

 

[Gadgeteer2000]

You need color code if there are other users that use the same frequency.





If you are only receiving, you do not need a call sign. You can own as many ham radios as you want without a call sign if you are never going to transmit.

If you are going to transmit, than legally you would need a call sign.

Thank you, all is clear now.

What I understand is that I can monitor local repeaters (without ID) - but in order to monitor for example Brandmeister I need an ID.

Time to speed up my learning to take the Ham test !

 

[JoeBearcat]

The scanner does not need an ID to receive a DMR system/frequency. Just use ID SEARCH to monitor all TGIDs and RIDs.

 

[Gadgeteer2000]

The scanner does not need an ID to receive a DMR system/frequency. Just use ID SEARCH to monitor all TGIDs and RIDs.

Thank you. But you cannot use the scanner to monitor Brandmeister groups, or can you? How? As far as I understand the main benefit of DMR (for ham users) is the various globally used talk groups - like those from Brandmeister. And those groups require an ID to monitor. But I may be wrong, so please correct me if that is the case. Thank you!

 

[sallen07]

Thank you. But you cannot use the scanner to monitor Brandmeister groups, or can you? How? As far as I understand the main benefit of DMR (for ham users) is the various globally used talk groups - like those from Brandmeister. And those groups require an ID to monitor. But I may be wrong, so please correct me if that is the case. Thank you!

You can certainly use a scanner to monitor Brandmeister groups ... but there has to be something that is transmitting that traffic.

If there is a DMR repeater nearby that has a particular group set up as static, then any traffic on that TG will be transmitted by the repeater and you can use a scanner (or DMR radio) to listen to it. If that repeater allows dynamic TGs, then if someone else keys up a particular TG, then the repeater will transmit any traffic on that TG until it times out. But if you are looking to monitor one of the worldwide talk groups then you probably won't be able to do that, since most DMR repeater owners don't allow those groups since they would tie up the repeater for hours.

Many (most?) hams who use DMR have a hot spot, which can be thought of as a tiny low-power repeater. (That's an oversimplification, but for the purposes of this discussion will work.) Same principle applies ... if I put a TG in as "static" on my hot spot, then any traffic on that TG will be transmitted by the hot spot and can be monitored using either a DMR radio or a scanner with DMR. If I want to talk on (or listen to) another TG, I can key up my radio and that will instruct the hot spot to add that TG as a dynamic group and I'll hear the traffic until it times out.

In order to use a hot spot in that fashion, you need an amateur radio license and a DMR ID. Even if you just listen to static TGs (and don't transmit) you must have a license to get a DMR ID and add your hot spot to Brandmeister.

Hopefully that all makes sense.

Oh and I would disagree that global TGs are the main benefit of DMR. Some people enjoy using them to talk to folks all over the world, but you can just as easily use DMR to talk to folks who are local to you using a repeater.

 

[dave3825]

Thank you. But you cannot use the scanner to monitor Brandmeister groups, or can you? How?

You program the frequency and listen to the talk group. Do you have a link to what you want to listen to? Like the webpage that lists the Brandmeister talk groups?

 

[Gadgeteer2000]

Thank you all for the input. Will monitor my local repeater for now and will work on getting my HAM license so I can use a hotspot to monitor (and participate in the) various global groups (using my Anytone DMR radio). I appreciate the guidance and explanations.