Reflector vs talkgroup: what's the difference and why it matters
When you first start getting to grips with DMR, the terms "talkgroup" and "reflector" are often conflated — both in articles and in on-air conversations. In reality they are different things with different histories: one is a group address, the other is a meeting point for nodes. Once you understand the difference, you'll grasp how routing in digital voice networks actually works.
A talkgroup is simply a group address
A talkgroup (TG) is the numeric identifier of a group call in the DMR protocol. When you press PTT, your radio sends that number in the packet header. The master server sees the TG number and forwards the audio to every hotspot and repeater that has an active subscription to that group.
Think of a TG as a mailing-list address: the letter (the voice) reaches everyone subscribed to that address. Your radio doesn't physically "connect" to anyone — it simply sends traffic tagged with the right TG number, and the master delivers it onward.
- A TG is a permanent object in the network; it exists regardless of whether there are any active users right now.
- TG routing is fully managed by the master server — the node doesn't "look for" anything itself.
- A single timeslot can hold several (static) subscriptions to different TGs at once.
A reflector is a "room" that nodes link into
The reflector is an earlier concept that came from D-STAR (where they're called reflectors/REF) and was inherited by some DMR networks. Technically a reflector is a concentrator server: a repeater or hotspot explicitly links to it with a command (usually a DTMF sequence or a special call via a Private Call), after which all traffic from that node goes into the "room" and is distributed from there to every other linked node.
Key traits of the reflector approach:
- At any given moment a node is linked to only one reflector (in classic systems like DMR+).
- To switch "rooms" you have to explicitly unlink and link again.
- Reflectors have historically had numbers in the 4000–4999 range (in BrandMeister).
- Traffic is distributed only between nodes connected to that particular reflector — which saves bandwidth in large networks.
Why reflectors are fading away in BrandMeister
In the early years of amateur DMR, many radios couldn't program arbitrary TGs from the keypad: the contact field could only be set through CPS. Reflectors became a workaround — the user sent a DTMF code and the repeater switched itself to the desired "room", without reflashing the radio.
The situation is different now. Modern radios (AnyTone, OpenGD77 and others) support entering a TG from the keypad in real time. BrandMeister, meanwhile, gives any node access to any talkgroup without prior "linking". As a result, reflectors in BrandMeister have effectively become aliases for TGs — the convenience is gone, but the complexity remains. BrandMeister is officially moving toward fully retiring reflectors in favor of TG-centric routing.
Static and dynamic TG subscriptions
This is an important practical distinction that is often confused with a "reflector".
Static TG
A static subscription is permanent: traffic for the chosen TG is always delivered to the hotspot/repeater, even if none of the local users has spoken on it. It's configured in the hotspot's control panel (Pi-Star/WPSD/RadioStar) or in the network's account dashboard.
Dynamic TG
A dynamic subscription is activated the moment a user goes on the air on that TG themselves. After the last transmission the subscription "lives" for a while longer (in BrandMeister — 15 minutes on most masters), then it expires automatically. This saves bandwidth: the hotspot isn't loaded with groups that no one is listening to locally.
Auto-static on the hotspot
Some systems (WPSD, Pi-Star) support an auto-static mode: as soon as a user goes on the air on a new TG, the hotspot "remembers" it as the current static one — until the next change. Handy for a single hotspot with a single user.
; Example of configuring static TGs in the MMDVM config (RadioStar / Pi-Star)
; Set this in the control panel, not by hand in the file —
; this shows the logic of the hotspot's "Static TalkGroups" field
TS1: 91 ; TG91 — Worldwide (static)
TS2: 250, 2502 ; TG250 (RU) and TG2502 (Regional) — staticThe main comparison table
| Trait | Talkgroup | Reflector |
|---|---|---|
| Essence | A numeric group address in the DMR packet header | A concentrator server that nodes explicitly link to |
| How it's activated | A subscription (static or dynamic) | An explicit link command (DTMF, Private Call) |
| How many at once | Several static TGs per timeslot | Only one reflector per node (in the classic model) |
| Where it's used | BrandMeister, TGIF, private networks | DMR+, early BrandMeister, D-STAR |
| Trend | The mainstream modern approach | Leaving BrandMeister, still alive in DMR+ |
How it works in DMRhub
DMRhub has no reflectors. Routing is built exclusively on the talkgroups of our master server. This is a deliberate decision: a small private network has no need for an extra layer of abstraction. The result is predictable behavior and simple hotspot setup.
When you go on the air, your hotspot sends traffic to our master with the TG specified. The master instantly forwards it to every hotspot with an active subscription to that group. No "linking/unlinking", no DTMF commands — just a programmed channel in your radio.
Set up your hotspot right the first time
DMRhub has no reflectors and no needless complexity — just talkgroups on our master. Download the ready-made RadioStar image for Raspberry Pi, or get the network contact list with all our TGs and operators.
Sources
- DMR terminology for amateur radio (talkgroup, reflector, subscription) — jeffreykopcak.com
- Static and dynamic TGs — BrandMeister Docs — help.brandmeister.network
- DMR Reflectors: the path between networks — 3fs.net.au
- A guide to DMR: routing basics — amateurradionotes.com