Private (individual) calls by DMR ID: how it works

Category: BasicsDifficulty: ★★☆~9 minutes

DMR has two types of calls: group (talkgroup — heard by everyone subscribed) and private, also called individual — a targeted call to a single subscriber by their DMR ID. Everyone uses talkgroups, but private calls work poorly or not at all in many networks. Let's figure out why, and how to do them properly.

Group vs. private — what's the difference

Technically the difference comes down to a single header field — FLCO (call type): for a group call it is "group", for a private call it is "individual". And in the address: a group call's address is the talkgroup number, while a private call's is the DMR ID of a specific subscriber. In other words, a private call is "call Smith", not "say it to room №6". For what TG, TS and DMR ID mean, see the DMR glossary.

Why you need it A private conversation without cluttering the shared group, paging the operator on duty, a pinpoint command to a specific operator. In essence — a radio-phone inside your own network.

Why many networks have no private calls

The most common "backend" of amateur networks is XLX reflectors. A reflector is group by its very nature: you link to a module (room), and everything that arrives there is distributed to everyone in that module. Targeted delivery to a single ID simply isn't provided for there — so an individual call is either ignored or "leaks" into the group. This is one of the limitations of reflector-based networks; see also the comparison of digital standards.

How it's done in DMRhub

Since our master is our own, it can do targeted delivery. A private call is addressed by DMR ID and reaches the recipient wherever they are:

radio → radio — the master finds which hotspot the required ID is currently "registered" on and delivers the call there;
radio → app and app → radio — the voice passes through the server-side vocoder and reaches the subscriber on their phone or on the air;
app → app — two operators with smartphones talk directly, without a single radio.

If the subscriber is not on the air right now, the system sees this and does not "broadcast" the call blindly to everyone. That is exactly the difference between true addressing and crude broadcasting.

How to set up a private call on a radio

On the radio side (any DMR model) you need just a little:

in the contact list, create a contact with the type Private Call and a number — the subscriber's DMR ID (not a talkgroup);
add your own DMR ID and the IDs of the subscribers you need to the RX Group so the radio receives calls addressed to you;
select that contact and press PTT — an individual call goes out.

The codeplug logic is the same on TYT, AnyTone, OpenGD77 — only the menu items differ; the setup basics are in the guides and codeplug materials. In the app it's simpler: tap a subscriber in your contacts and the call goes out.

A subtlety with RX Group If you don't add the required IDs to the receive group, the radio "won't hear" a private call addressed to it — a frequent cause of "people are calling me but it's silent on my end". On the hotspot it matters that it lets individual streams into the correct timeslot.

Bottom line A private call is a targeted call by DMR ID, not to a room. It's almost out of reach for reflectors, but easy on your own network with a proper master. Related topics: DMR-SMS (text to the same subscriber) and how the network is built.