First and foremost I highly encourage you to read the manual of qdmr. It is written very well and describes things in detail, without making it complex.

Here I will make my own little abstract of the most important concepts, to make things clearer for me. If it helps someone else, even better!

Concepts

  1. DMR-ID
  2. Talk group
  3. Time slot
  4. Color code
  5. Calling and talk group subscription
  6. Reflector
  7. Roaming

DMR-ID

The DMR-ID is the digital version of your call sign. Nowadays there is one radio id for all digital standards (C4FM, DMR, D-Star). In order to get a radio id you need to register at radioid.net.

Talk Group (TG)

When you send and receive in DMR you need to address a specific talk group (or Private ID). Every talk group (expect for TG8-Regional and TG9-Local) is unique. So if you call CQ in the TG123 in Tokyo, and someone in London is listening TG123 he’ll hear you. The fact, that you don’t need to care about the repeater is called transparency.

If the repeater you’re connected to isn’t subscribed to a certain talk group, you simply have to make a call to that group and the repeater will subscribe for about 10-30min.

Time Slot (TS)

DMR is designed in such a way, that two calls can be made on the same frequency.

Usually time slots are:

  • TS1: Trans regional
  • TS2: Local

Color Code

Color Code is another way to differentiate between calls. It is used in dense areas, but not in my home QTH.

Calling and TG subscription

You have three options to place a call with DMR.

  1. Simplex private call
  2. Simplex group call
  3. All Call

The first is a private call. Here you call the Radio ID assigned to a specific person. It’s equivalent to calling the phone number of a person. Bear in mind, that during this call the time slot is blocked and others cannot here, what you are saying (exceptions exist). So keep these calls short.

Note: A private call is only possible, when the two parties are in the same network (e.g. Brandmeister, IPSC2,…).

The second option is a group call. Here a Group ID is used and everybody who is subscribed to that group can here the call. Bear in mind, that the repeater has to also be subscribed to that talk group. This can be done in two ways:

  1. The Sys OP of the repeater has the talk group in its default subscriptions
  2. You placed a short call using that group id. Then the repeater is subscribed for a certain time

Lastly, you can call everybody, by using the special All Call Number (16777215). Note, that you should use this number responsibly.

Reflector

Another way to communicate is to use reflectors. Here you can make your repeater broadcast your call onto a specific set of repeaters, who will send your call via TS2/TG9.

For that you need to do following

  1. Choose TS2/TG9 on a repeater
  2. Dial the reflector number you want to use (as private number, not TG) and briefly push the PTT button. You should hear a confimation
  3. Now simply make your call

A list of reflector can be found in the cheat sheet. Reflectors are only used in the IPSC2 network.

Roaming

Roaming works, by linking repeaters of one region to the same talk groups. This way you accomplish repeater transparency.

A list (Roaming Zone) of repeaters in one region with the same TG needs to be created.

Roaming is used, when you move from one repeater to the next. When the signal drops below threshold, or when the PTT is pressed, the radio pics the repeater from the list with the same TG automatically.