Two ideas that are easiest to learn together — what a time slot is, what a talkgroup is, and the difference between a static and a dynamic talkgroup, including why BrandMeister and TGIF handle it so differently. Part of the N6JET Digital Voice Guides.
In DMR, a single channel in your radio is really three things stacked together: a repeater or hotspot, a talkgroup, and a time slot. Two of those — talkgroups and time slots — are so closely linked that they make the most sense side by side. This page walks through the time slot first (the lane your signal travels in), then the talkgroup (the conversation you route into it), and finally the piece that trips up most newcomers: whether a talkgroup is static or dynamic.
DMR takes a single 12.5 kHz channel and, using a technique called TDMA, splits it into two time slots — TS1 and TS2 — that behave as two independent conversations sharing one frequency. Picture one frequency carrying two separate lanes of traffic that never collide, because each lane is handed alternating slices of time. That is the whole reason DMR can fit two simultaneous contacts where analog fits one.
On a duplex repeater — which listens on one frequency and transmits on another — both slots are available. A repeater can carry two completely separate talkgroups at the same moment, one on TS1 and one on TS2. When you program a channel for a repeater, part of the setup is choosing which slot that channel uses.
A simplex hotspot works differently. Because it receives and transmits on the same single frequency, with no repeater to supply the timing reference that two-slot TDMA needs, a simplex hotspot runs on one slot only — and by convention that slot is TS2. On a typical hotspot, TS1 is effectively disabled and everything happens on time slot 2. It is a convention of the hotspot software rather than a rule of the DMR standard, but it is close to universal, so on your hotspot you can safely assume TS2.
If the time slot is the lane, the talkgroup is the specific conversation you steer your voice into. You do not tune to a talkgroup the way you would dial up a frequency — you link to it, and you only hear the talkgroups your radio and hotspot are set up to carry. Which raises the question that causes most of the early confusion: there are two different ways that linking happens.
A static talkgroup is one you attach permanently to a time slot, so it is always linked and you always hear it. You set these yourself in BrandMeister's SelfCare portal (or, on a repeater, the repeater keeper sets them), assigning each one to a slot. On BrandMeister you can hold several static talkgroups on a single slot at once — a small, always-on list of the groups you care about most.
A dynamic talkgroup is a temporary connection you activate on the fly by keying it up (a quick press-to-talk to that talkgroup number). It stays linked while there is activity, then automatically drops after about 15 minutes of inactivity. Dynamic linking is how you visit a talkgroup you have not set static — you call it up, use it, and let it fall away on its own.
One important special case: the TAC channels (talkgroups 310–319) are dynamic-only. BrandMeister does not let you make them static, so they always behave dynamically and always time out — which is exactly what keeps them clear and available for the next pair who need somewhere to move a conversation.
TGIF does not use dynamic talkgroups the way BrandMeister does. There is no inactivity timeout and nothing auto-drops. Instead, you stay parked on the last talkgroup you keyed up — one per time slot — and you switch simply by keying up a different one. So the BrandMeister mental model of “a few statics that stay, plus a dynamic that times out” does not carry over: on TGIF you are always on a single talkgroup per slot until you deliberately change it. If you run both networks, this is the difference worth keeping straight.
A handful of low talkgroup numbers do special jobs, and these are the ones worth knowing by name — the examples that come up most often:
| Talkgroup | What it does |
|---|---|
| TG 1 | Local — repeater range only. Your signal is DMR but stays on the repeater and is not linked to any network or talkgroup. |
| TG 2 | Cluster — links a defined group of repeaters (for example, a club), so a call reaches every repeater in that cluster but no further. |
| TG 9 | On slot 2, the Dial-a-TG gateway — private-call a talkgroup number to link it on the fly, then talk through TG 9 (see the note below). |
| TG 91 | Worldwide. |
| TG 99 | Simplex — the convention for radio-to-radio contacts, off the network entirely (it pairs with the simplex hotspot idea above). |
| TG 9990 | Parrot (echo) — plays your audio back so you can hear how you sound and confirm you are getting in. |