DMR advise please.

[Kdu123]

Would I be right in saying that if I receive a signal in DMR mode and identify the user, they may transmit on a different frequency the next time they talk ?
Thank you from Kris

 

[letarotor]

There are different DMR tiers. And if it's a trunk radio system, TRS, DMR Tier 3 is what is being used. And on the DMR TRS/Tier 3, what you said could be very true. Each time there's a transmission they could be on a different frequency on that TRS. But on average, if it's just a single frequency DMR user, also known as a Tier 1 DMR user, then they will be on the same frequency each time they talk. They may have other frequencies they can go to that are still DMR but as long as they're staying on the same talkgroup / channel in a Tier 1 radio traffic setup, they should remain on the same frequency.

I'm foggy headed and just woke up so I'm not even going to try to explain Tier 2 because I don't remember right at the moment exactly what that covers But it is a lot like Tier 1 and I believe it stays on the same frequency. Tier 3 is just the DMR on a multi-frequency TRS I believe.

But if you just keep in mind that a DMR user on a multiple frequency trunk system can be on a different frequency each time they talk, and of course using the same set of frequencies the same frequencies in that TRS get used again at times, most other DMR traffic should remain on the same talkgroup / frequency unless they manually switch over to another talkgroup / frequency.

I hope this helps and wasn't more confusing. I need to wake up before I try answering questions haha...

Brian
COMMSCAN

 

[Kdu123]

Wow, my head is in more of a pickle Lol. I'm new to DMR and I stumbled across our company radio transmission last night then a few minutes later it came through on a different frequency! Things have changed a lot since my last receiver some 20 years ago. Thank you for your explanation, I will get there

 

[WA0CBW]

Look up their license and see how many frequencies they have. That will give you an idea what kind of system they may be using.

 

[Ubbe]

if it's just a single frequency DMR user, also known as a Tier 1 DMR user, then they will be on the same frequency each time they talk.

Actually, I believe Tier1 are dPMR, a type of digital FRS/GMRS type of system that only use cheap simplex radios, and Tier2 are the single frequency DMR systems. Hytera have a single frequency XPT system type where they can use both slots as trunked voice channels in the same system. Then there are single frequency DMR where users can be locked to either slot one or two depending of what talk group they use.

/Ubbe

 

[slicerwizard]

Actually, I believe Tier1 are dPMR

I don't think so.

 

[kg4icg]

Tier 2 is same frequency, different time slots. can have 2 conversations going on at the same time not interfering with one another. For example, same repeater, same frequency, different time slots as you notice in the pic, diffent tg's also

 

[CanesFan95]

Would I be right in saying that if I receive a signal in DMR mode and identify the user, they may transmit on a different frequency the next time they talk ?
Thank you from Kris

Yes. This can happen either because the users agree to simply flip to a different channel on their radios. Or because you're listening to a frequency that is part of a trunking system. A trunking system is basically where you have a block of several frequencies that are computer-controlled where conversations rotate around and change frequencies each time someone keys up and talks, although there can be some hangtime where the conversation stays on the same frequency if the next person to talk keys up fast enough.

If the users are not on a trunked system, then it'll be a conventional frequency which basically means the conversation stays put on the same frequency.

A slot is a period of time where a digital radio signal is transmitted for only a portion of the airtime. DMR has slots 1 and 2 which alternate between 2 different time periods without interfering with each other. This allows 2 different channels (separate conversations) to exist and take place on a single RF frequency. So suppose a conventional DMR frequency of, say, 464.925 for example has slot 1 and slot 2. Slot 1 could be channel A and slot 2 could be called channel B.

A group of users on channel A (slot 1) can be talking and having a conversation at the same time a group of other different users have a conversation on channel B (slot). All on the same frequency 464.925 at the same time without interfering with each other because the radios on each channel only transmit intermittently on the opposite slots. Contrast this to analog where only 1 channel/conversation can take place on a frequency.

 

[Kdu123]

Yes. This can happen either because the users agree to simply flip to a different channel on their radios. Or because you're listening to a frequency that is part of a trunking system. A trunking system is basically where you have a block of several frequencies that are computer-controlled where conversations rotate around and change frequencies each time someone keys up and talks, although there can be some hangtime where the conversation stays on the same frequency if the next person to talk keys up fast enough.

If the users are not on a trunked system, then it'll be a conventional frequency which basically means the conversation stays put on the same frequency.

A slot is a period of time where a digital radio signal is transmitted for only a portion of the airtime. DMR has slots 1 and 2 which alternate between 2 different time periods without interfering with each other. This allows 2 different channels (separate conversations) to exist and take place on a single RF frequency. So suppose a conventional DMR frequency of, say, 464.925 for example has slot 1 and slot 2. Slot 1 could be channel A and slot 2 could be called channel B.

A group of users on channel A (slot 1) can be talking and having a conversation at the same time a group of other different users have a conversation on channel B (slot). All on the same frequency 464.925 at the same time without interfering with each other because the radios on each channel only transmit intermittently on the opposite slots. Contrast this to analog where only 1 channel/conversation can take place on a frequency.

That makes perfect sense, thank you very much

 

[bcgoreme]

From the European Standards organization that defines and manages the DMR technical standards: ETSI - Mobile Radio - DMR, PMR