DMR Trunking

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DMR Trunking

DMR is Digital Mobile Radio

An open standard created as defined by the European Telecommunications Standards Institute or ETSI

What you need to know

DMR is broken down into 3 tiers.

In Scanner School Session 55 we discussed Tier I and Tier II.  This week we talk Tier III.

DMR Tier III – we will talk about this more next week.

Licensed Trunking Radio

Covers 66Mhz – 960Mhz in the EU Spectrum

Uses two slot TDMA

Offers advanced voice features

Offers Short messaging limited to 128 characters

Also 288bits for data in various formats


Types of DMR Trunking:

There are 3 flavors we are interested in:

Connect Plus, Capacity Plus, and Capacity Max.

Usually shown as Con +, Cap + on scanners.


Capacity plus

Can be single Site capacity plus or linked capacity plus with multiple sites

Up to 15 linked sites

Up to 12 repeaters per site.  Of these 12, only 8 can be voice & Data.  And of these 12, 11 can be data revert. But they can’t be more than 12 repeaters total

Has a rest channel for idle traffic.   


The Rest Channel sends out a data burst every x number of seconds, which is programmable for the system.  

When a radio requests a channel, the current rest channel becomes the active channel.

All idle radios move to the next rest channel.  One the active radios are done, they then move to the new rest channel with the rest of the idle radios.

System will increase rest channels until it gets to the last one, and then falls back to the first rest channel.

Supports Dynamic Trunking and does not require a controller.

Connect Plus:

Connect Plus is a multi Site Network

Upto 250 sites and 15 repeaters per site

Has a fixed control channel

Supports GPS, Text Messages, and man down alerting.

Operates with Dynamic Site Assignment, so only the only voice resources you use are on the local site you are operating on (and where the other units are registered to)

Has been discontinued by Motorola and replaced by MotoTRBO Capacity Max

Capacity max

Fully compliant with DMR Tier III standards

A system can support up to 250 sites and 15 repeaters per site

Voice & Data communication up to 15 sites at a time plus up to 6 data revert repeaters per site

Dedicated Control Channel Time Slot per repeater

Second Control Channel may be added for added capacity

Supports GPS, Text Messages, Etc



So what information do we need when programming DMR conventional into our scanners?

A radio capable of picking up DMR

We need the Logical Channel Number (LCN) of all the frequencies on the site we want to monitor.
Usually the LCN’s are paired for each TDMA channel. Ex, Ch 1 & 2 are the same freq, Ch 3 & 4, so on and so forth.

The Talk Group


Scanners that support DMR:

If you pay for the Whistler Offical Upgrade:

GRE PSR-800, Radio Shack PRO-668, and PRO-18


Via  a Free Whister Upgrade:

WS1080, WS1088, WS1095, and WS1098


Out of the Box:

Whistler TRX-1 and TRX-2

With paid upgrades:

Uniden BCD436HP, BCD536HP, SDS100, BCD325P2, BCD996P2


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Links and Sources from this session:


ETSI TS 102 361-1 v 2.4.1

DMR Association

Radio Reference Wiki:

Motorola Connect Plus Product Brochure

Motorola Connect Plus Overview:

MotoTRBO Systems at a glance:


Bonus Material:

Are you looking for your first scanner radio?

Download our new e-guide, “5 Thinks You Need to Know Before Buying Your First Scanner”.   This free PDF is about 30 pages long and has 5 things you should look for, plus a few extra bonus items to make sure you make an educated purchase.

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Podcast Transcription:

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