In Digital Mobile Radio (DMR) systems (like those used in amateur radio on networks such as BrandMeister, DMR-MARC, or others), a talkgroup (often abbreviated TG) is a virtual grouping identifier — essentially a number (e.g., TG 91 for worldwide, TG 3100 for North America regional, TG 3116 for a specific local group) that organizes and directs voice communications.
Think of a talkgroup as a dedicated conversation channel within the DMR network. Multiple users can join the same talkgroup to talk to each other, even if they’re using different repeaters, hotspots, or locations worldwide.
1. Filtering Transmissions (Similar to Tone Squelch on Analog)
A talkgroup acts very much like a CTCSS (PL tone) or DCS on analog FM radios:
- On analog FM:
- You set a receive tone (CTCSS/DCS) on your radio.
- The radio’s squelch stays closed (silent) unless the incoming transmission includes that exact tone.
- This filters out all other traffic on the same frequency, so you only hear transmissions intended for your group.
- On DMR (digital):
- Every digital transmission includes a talkgroup number in its data header (along with your radio’s DMR ID, timeslot, color code, etc.).
- Your radio is programmed to only unmute and play audio for transmissions where the talkgroup number matches:
- The currently selected talkgroup (the one you’re transmitting on), or
- One of the talkgroups in the TG List assigned to that channel (if using OpenGD77-style multi-TG channels).
- If a transmission arrives on the same frequency and timeslot but with a different talkgroup, your radio ignores it completely — no audio is played, even though the signal is strong and the frequency is the same.
This filtering happens at the radio level (receive side), so users not “subscribed” to that talkgroup won’t hear the conversation, even if they’re tuned to the exact same repeater/hotspot frequency.
Key difference from analog tones:
- CTCSS/DCS is a simple sub-audible tone carried in the audio path.
- DMR talkgroups are digital metadata in the protocol header — much more precise and flexible (thousands of talkgroups possible vs. ~100 CTCSS tones).
2. Routing Through the Internet (Like “Internet Chatrooms”)
This is where DMR becomes truly powerful — talkgroups are routable over the internet, turning local radio repeaters into part of a global network.
- How routing works:
- When you transmit on a talkgroup (e.g., TG 91 Worldwide), your radio sends the voice packets to the local repeater or hotspot.
- The repeater/hotspot forwards those packets over the internet to the network server (e.g., BrandMeister master server).
- The server looks at the talkgroup number and routes the audio to every other repeater/hotspot worldwide that has that talkgroup active (either statically configured or dynamically linked via PTT).
- Those repeaters/hotspots then rebroadcast the audio on their local RF frequency (on the correct timeslot).
- Anyone listening on that talkgroup anywhere in the world hears you.
- Static vs. Dynamic talkgroups:
- Static — The talkgroup is always “linked” to the repeater/hotspot (e.g., a local repeater always carries TG 2 for regional traffic).
- Dynamic (PTT-based) — The repeater only links to the talkgroup temporarily when someone keys up on it (common on BrandMeister for worldwide TGs like 91, to avoid tying up the repeater with constant global traffic).
This routing makes talkgroups function like internet chatrooms or Discord voice channels:
- Worldwide communication — Users in New York, London, Tokyo, and Sydney can all talk on the same TG 91 using their local repeaters or hotspots.
- No need for everyone to be on the same frequency — The internet bridges everything.
- Scalable — Thousands of talkgroups exist (local, regional, worldwide, special interest like TAC310, emergency, etc.).
Summary Comparison Table
| Feature | Analog CTCSS/PL Tone | DMR Talkgroup |
|---|---|---|
| Filters unwanted traffic | Yes (tone must match) | Yes (TG number must match) |
| Works on same frequency | Yes | Yes (same freq + timeslot) |
| Routing over internet | No (local only) | Yes (global via networks like BrandMeister) |
| Number of “channels” | ~50-100 tones | Thousands of talkgroups |
| Global reach | Local repeater only | Worldwide (via internet linking) |
| How it feels | Local group on one repeater | Virtual chatroom spanning the planet |
In short: Talkgroups give you the privacy/filtering of tone squelch on analog, but add the magic of global, internet-routed conversations — allowing hams worldwide to chat as if they were all on the same local repeater, no matter where they physically are.