Scanning with a DMR Radio

Why you cannot scan four talkgroups the way you scan four analog repeaters — and the four methods that do work instead. Part of the N6JET Digital Voice Guides.

Almost every analog and digital radio on the market has a scan feature, and on a DMR radio you program it from the CPS just like everything else. So the natural question, once your code plug is working, is: can I set the radio scanning across my talkgroups the way I would across a few analog repeaters?

The honest answer is not simply yes or no, so it deserves a proper look.

One scope note before anything else: this page is about BrandMeister.

How you set up scanning depends on which DMR network you are using. The methods described here are possible on BrandMeister. They will not work on TGIF, which is designed differently — and the same goes for FreeDMR, AmComm and QuadNet. Do not assume any of this carries across.

The difference is not a quirk, it is architectural. BrandMeister gives you statics and dynamics, and this page is built entirely on statics. TGIF does not work that way at all — it has no dynamic talkgroups and no inactivity timeout; you simply stay parked on the last talkgroup you keyed up until you switch. A model with no statics to set is a model where the methods below have nothing to stand on.

Learn more at N6JET.com: Talkgroups & Time Slots — the BrandMeister and TGIF models side by side · BrandMeister vs. TGIF

The Thing That Does Not Work

Where it is possible to set "scan" to scan and monitor four analog repeaters for activity on your radio, the same cannot be done for four DMR talkgroups.

This catches people out, and it should — it is a perfectly reasonable thing to expect. On analog you build a scan list of four repeaters, hit scan, and the radio sweeps across them and stops on whichever one is busy. Four talkgroups ought to work the same way. They do not.

Why not

Two reasons. Everything else on this page follows from them, so they repay a minute of attention.

First, a DMR talkgroup only exists on your radio if your hotspot is carrying it. Analog repeaters transmit whether or not anybody is listening — the signal is simply out there, and a scan sweeps across and finds it. A talkgroup your hotspot has not linked produces nothing at all. There is no signal on the air to find.

Second, they all arrive on the same frequency. Your hotspot has one frequency. Every talkgroup it carries comes down that one frequency. So there is nothing for the radio to sweep across — four DMR channels in a scan list are four looks at the same place.

Which gives the rule that explains everything below:

A scan list works across FREQUENCIES. It does not work across TALKGROUPS.

Every method that follows either works around that, plays to it, or defeats it.

First, the Requirement Everything Else Depends On

Only talkgroups that have been activated as STATIC talkgroups on your hotspot — and on BrandMeister, in your SelfCare account — can be scanned or group monitored.

This is not a detail, it is the gate. Go back to the first reason on this page: a talkgroup only exists on your radio if your hotspot is carrying it. A static talkgroup is one you have attached permanently, so the hotspot carries it all the time, whether or not anything is happening on it. Being carried is precisely what makes it available to monitor.

You cannot scan dynamic talkgroups. Not with any of these methods, not at all.

A dynamic talkgroup can never be scanned or monitored. This is not a limitation of your radio or a setting you have got wrong — it is impossible by the nature of what a dynamic talkgroup is.

Follow the reasoning once and you will never wonder about it again.

A dynamic talkgroup is created by your own transmission. It is not sitting there waiting. You key up on that talkgroup, and that act is what links it to your hotspot. Until you transmit, it does not exist on your system at all.

Scanning never transmits. Scanning is a purely receiving activity — the radio sweeps, listens, and stops on whatever it finds. It has no mechanism to key up, and no reason to.

So there is the impossibility, in one line:

A dynamic talkgroup requires a transmission to bring it into existence. A scan only ever listens. A scan can therefore never bring one up — there is nothing on the air for it to find.

And two more things stack on top of that, in case the first is not enough:

You only get one at a time. Key up a different talkgroup and it replaces the one before it. So four dynamics running together — the very thing you would want to scan — is not a state your hotspot can be in.
It drops on its own. After roughly fifteen minutes of inactivity on BrandMeister, the dynamic link goes away. Even the single one you established will quietly disappear while you are sitting there listening to a scan find nothing.

So before any of the methods below will do anything for you, set the talkgroups you want to monitor as statics. On BrandMeister that is done in SelfCare. Without that step, the RX group list in Method 1 will faithfully pass four talkgroups that are never carried — and you will hear silence, and conclude the radio is broken.

The short version: a static talkgroup is brought to you and stays there, so there is something to monitor. A dynamic talkgroup is fetched by you, one at a time, and expires. Monitoring needs the first kind. Static is the only kind you can scan.

If you followed the beginner's guide, this is a deliberate change of gear. That guide tells you not to set any statics — and on day one that is right, because a static talkgroup arriving while you are on a different channel is baffling before you know why. This page is where statics start earning their keep. You now know what they do, so you can turn them on for a reason.

Learn more at N6JET.com: Talkgroups & Time Slots — static, dynamic and parked, in full.

Method 1 — Put Several Talkgroups in One RX Group List

Works around the rule.

First — what an RX Group List actually is

Every channel in your code plug has two talkgroup settings, and they do opposite jobs. Getting them straight makes this whole method obvious.

Setting	What it controls
TX Contact	What the channel transmits to. One talkgroup — where your voice goes when you key up.
RX Group List	What the channel listens to. A list of talkgroups — the ones this channel will let you hear.

So the RX Group List is the receiving side. It is a named list of talkgroups attached to a channel, and it acts as a filter: if a talkgroup is not in that channel's RX Group List, the radio stays silent even when traffic for it arrives. The audio reaches your radio and the radio declines to un-mute.

Hold on to that, because it is also the opening. TX Contact holds one talkgroup, but an RX Group List can hold several. Nothing says it has to contain only one.

You have already built these. If you followed the beginner's code plug, you made four RX group lists with exactly one talkgroup in each. That was the simple case. Same screen, same >> button — you just move more talkgroups across.

Now the method

You can listen to more than one talkgroup at a time by expanding the RX Group List for that particular channel — putting every talkgroup you want to monitor into one single RX group.

Choose your talkgroups and add them all to the RX Group. Say you choose TG 91, 93, 3100 and 313136: all four must appear in the RX group used for the channel you will be listening on. That one channel will then pass all four.

And all four must be set as statics on your hotspot, per the requirement above — the RX group list decides what your radio will let through, but the statics decide what actually arrives.

But this is monitoring, not scanning

The difference matters, so be clear about what you are getting:

You cannot pause. On an analog scan you can stop on a channel and sit there listening to a conversation. There is no equivalent here — four talkgroups on one RX group list cannot be paused on.
The audio simply flows as the network sends it. You are not selecting anything. Whatever arrives, you hear.
If two talkgroups are busy at once, only one can use the time slot at a time.

That last point is the whole story. One time slot carries one conversation. Point four talkgroups at it and they are competing for the same single lane — so when two are active together, one gets through and the other does not. Nothing queues, and nothing waits for you to come back to it. Hence no pause: there is no list of channels being swept, just one lane carrying whatever reached it first.

Method 2 — A Scan List Across Different Frequencies

Plays to the rule.

Set up a scan list containing, for example, your hotspot, a local analog repeater, and a simplex channel. That works well — and it works for exactly the reason the four-talkgroup version does not.

Note what that list actually is, though: one digital channel and two analog ones, all mixed together. It works — and it is also a perfect illustration of how messy DMR scanning gets the moment you leave the simple case behind. Read the drawbacks below and you will see why this page keeps insisting on the difference between scanning and monitoring.

These are three different frequencies. Each carries a real signal that is either present or not, so the radio can sweep across them, find one that is active, and stop on it. Exactly the job a scan list was built for.

Same radio, same scan feature. It just has to be pointed at frequencies rather than talkgroups.

The drawbacks of mixing analog and digital in one list

It works — but go in knowing what you are trading, because analog and DMR are different animals at the scanning level.

The two scan stops are not the same amount of work. Analog scan logic is simple: detect a carrier or a tone, stop. A DMR scan stop is doing far more — detecting a TDMA signal, syncing to it, then checking colour code, time slot and talkgroup before it can decide whether to stop at all.
Sluggish scan rates. All that extra evaluation slows the sweep down.
Missed analog activity while the radio is busy evaluating a digital signal — a short analog transmission can come and go while the radio is still deciding about a DMR one.
Stops that feel random, because you cannot see any of the above happening.
The machines themselves behave differently. A hotspot only transmits when network traffic is flowing. An analog repeater has tails, IDs and squelch behaviour that DMR simply does not have — so the two produce very different patterns for a scan to chew on.

The practical answer: keep separate scan lists — analog with analog, DMR with DMR — and switch lists with your zones. A mixed list of one quiet hotspot, one repeater and a simplex channel is the mild end of it and works well enough. The more digital channels you add, the more of the above you get.

Which is rather the point. Method 2 is left in this guide precisely because it shows how quickly DMR scanning turns messy. It is the method most people reach for first, and the one where "it works" and "it works well" turn out to be two different claims.

Learn more at N6JET.com: DMR Guide — "A Word About Scanning" covers this trade-off in full.

Method 3 — One Hotspot Per Frequency

Defeats the rule.

If you have more than one hotspot, you can put each hotspot's frequency in the scan list as a separate channel to monitor.

This is the method that genuinely answers the question the page opened with. Each hotspot sits on its own frequency carrying its own talkgroup — so those talkgroups have become separate frequencies, and separate frequencies are precisely what a scan list can sweep. You have not beaten the rule so much as arranged your station to satisfy it.

And because these really are separate channels now, the behaviour Method 1 could not give you comes back: the radio stops on activity, the way an analog scan does, instead of taking whatever happens to arrive down a single lane.

The honest trade-off: this is the method that costs the most — a whole hotspot per frequency. What you buy for it is the closest thing to the analog scanning experience, across as many talkgroups as you have hotspots. Each one needs its own frequency, chosen by the usual rules: listen first, never 435–438 MHz, and do not sit on the input of a coordinated repeater.

Method 4 — A Duplex Hotspot, Using Both Time Slots

Removes the bottleneck instead of working around it.

Every method so far has accepted one limitation: your hotspot has a single time slot, so however many talkgroups you point at it, only one conversation can come through at a time. Method 4 is the one that changes that.

Why a duplex hotspot has two slots and a simplex one does not

DMR splits a channel into two time slots, TS1 and TS2. Whether you get both depends on the hardware.

A simplex hotspot receives and transmits on the same single frequency. With no repeater to supply the timing reference that two-slot TDMA needs, it runs one slot only — TS2 by convention. The beginner's guide builds exactly that hotspot, which is why everything above ends up sharing one lane.

A duplex hotspot listens on one frequency and transmits on another, exactly as a repeater does. That gives it both slots — and two slots means two completely separate talkgroups carried at the same moment, one on TS1 and one on TS2.

This is the only method that increases how much can actually arrive. Methods 1, 2 and 3 rearrange what you do with the traffic you can receive. A duplex hotspot doubles it — when two talkgroups are busy together, both get through, because they are no longer competing for the same lane.

How you set it up

For Method 4 to work you need two separate channels in the scan list — one for Time Slot 1 and one for Time Slot 2.

The whole trick sits in that one line, and it is less exotic than it sounds. You are not asking the radio to do anything clever with time slots. You are giving it two ordinary channels and a scan list, exactly as in Method 2 or Method 3. The radio scans channels; it does not need to know or care that what distinguishes these two is the slot setting rather than the frequency.

So:

Set one talkgroup static on TS1 and another static on TS2.
Build two channels in your code plug — identical in every respect except that one is set to Slot 1 and the other to Slot 2, each carrying its own talkgroup and its own RX group list.
Put both channels in a scan list.

Now the radio sweeps between them and stops on whichever slot is carrying traffic — and because the two slots are genuinely independent, both talkgroups can be busy at the same time without either being lost.

You can also combine this with Method 1: several talkgroups in the RX group list on each slot, which gives you breadth on both lanes rather than one.

Where this sits on cost. Method 3 buys a whole second hotspot for a second frequency. Method 4 buys a duplex board instead of a simplex one and gets a second lane out of the hardware you were already going to build. It is the cheaper step up — but note it is different hardware, not an upgrade you bolt on: the beginner's guide specifies a simplex board and a case cut for it, so this is a decision made at purchase.

Which One Do You Want?

Method	What it gives you	What it costs
1. One RX group list	Hear several talkgroups on one channel	No pausing; busy talkgroups collide on one time slot
2. Frequency scan list	True scanning across a hotspot, a repeater and simplex	Does not separate talkgroups — only frequencies
3. One hotspot each	True scanning across talkgroups, stops on activity	A hotspot per frequency
4. Duplex hotspot	Two talkgroups live at once — one per time slot	A duplex board rather than simplex, decided at purchase

Methods 1 and 2 cost nothing but accept the single lane. Methods 3 and 4 spend money to get more lanes — Method 4 more cheaply, Method 3 more flexibly.

If You Are New — Leave This Alone for Now

My advice: if you are a beginner, set scanning aside for now. Get to know how DMR functions first.

Nothing on this page is difficult, but all of it assumes you already have a working mental picture of what your hotspot is doing, what a static talkgroup is, and where the audio actually comes from. Without that, scanning is where the gaps in the picture show up, and the fault looks like the radio.

Get a station working. Make some contacts on one talkgroup at a time. Once the ordinary case is second nature and you find yourself genuinely wanting to hear two conversations at once, come back — it will read as obvious rather than as a wall.

Learn more at N6JET.com: DMR Guide · Success with DMR · The Codeplug · Talkgroups & Time Slots · Hotspots