Also known as: trunk-tracking scanner, trunk tracker
A trunking scanner is a scanner that can follow a trunked-radio system — it reads the system’s control channel, learns which voice channel each talkgroup has just been assigned, and jumps there automatically.1 Without that ability, a scanner catches only disconnected scraps of the conversation, which is why an ordinary scanner misses most modern public-safety traffic.
Key takeaways Trunking scanners follow talkgroups across channels. They decode the control channel, read each channel grant, and hop to the assigned voice channel so a call sounds continuous. Most modern police/fire are trunked — a non-trunking scanner hears only fragments. Trunking ≠ digital: a system can be analog-trunked or digital-trunked. No scanner decodes encryption. The free path is an SDR + GopherTrunk.
What makes a scanner a trunking scanner
On a conventional system, an agency owns a fixed frequency and you just tune to it. On a trunked system, a pool of voice channels is shared among many talkgroups, and a computer hands out channels on demand. When a unit keys up, the system picks any free channel and announces the assignment on a dedicated control channel.
A trunking scanner is defined by one behavior: it monitors that control channel. It continuously decodes the stream of channel grants — “talkgroup 1234 is now on voice channel 7” — and when it sees a grant for a talkgroup you want, it retunes to that voice channel in time to catch the transmission, then returns to the control channel to await the next grant. That tracking is what makes a hopping conversation sound like one continuous call.
A plain scanner can’t do this. Tuned to a single voice channel, it would hear a few seconds of one talkgroup, then a fragment of an unrelated one, then silence — never a coherent conversation.
The systems a trunking scanner follows
- Motorola Type II / SmartNet / SmartZone — the most common US public-safety trunking family, analog and digital.
- APCO Project 25 (P25) — digital trunking, Phase I and II, now dominant for police and fire.
- EDACS — an older GE/Ericsson trunking standard, still in use in places.
- LTR — a lightweight trunking scheme common on business and some public systems.
Each encodes its control channel differently, so a trunking scanner must support the specific format your agency runs. Check your system type on RadioReference.
Trunking vs digital — two separate axes
It is easy to confuse “trunking” with “digital,” but they are independent:
| Conventional | Trunked | |
|---|---|---|
| Analog FM | Any scanner | Needs trunk-tracking (e.g. BearTracker BCT15X) |
| Digital (P25/DMR/NXDN) | Needs a digital scanner | Needs a digital trunk-tracking scanner |
- Trunking = follows talkgroups across channels (control-channel tracking).
- Digital = decodes P25/DMR/NXDN voice.
A system can need one, the other, or both. The BCT15X trunk-tracks but is analog-only; the SDS200 does both.
Which of these models trunk-track
Among the scanners in our field guide:
- Trunk-tracking (digital): Uniden SDS200, Whistler TRX-1, Whistler TRX-2, Whistler WS1065 (legacy P25).
- Trunk-tracking (analog only): BearTracker BCT15X.
- Not trunk-tracking: the analog handhelds Uniden SR30C, BC125AT, and BC75XLT — fine for conventional analog, air, marine, rail, and racing, but they cannot follow a trunked system.
See the full best police scanners ranking to match a model to your area.
What a trunking scanner cannot do
Following a talkgroup is not the same as hearing it. When a talkgroup is encrypted, a trunking scanner still reads the control channel, identifies the talkgroup, and hops to the voice channel — then plays silence, because it has no key. No scanner and no SDR — including GopherTrunk — can decode AES encryption. Trunk-tracking gets you to the conversation; it can’t break the cipher.
The free alternative
A software-defined radio — a ~$30 RTL-SDR — running GopherTrunk is a full trunking receiver: it decodes the control channel, follows talkgroups across P25, DMR, and NXDN systems, and additionally records, logs, and timestamps every call across unlimited talkgroups at once — something no single scanner does. It trades portability and a turnkey experience for zero cost and far more data. The honest head-to-head is in police scanner vs GopherTrunk, and you can download GopherTrunk to try it with a cheap dongle.
Bottom line
A trunking scanner is what lets one radio follow a shared, channel-hopping trunked system as if it were a single channel. If your agencies are trunked — most are — you need trunk-tracking, plus digital decode if they run P25/DMR/NXDN. Encrypted talkgroups stay off-limits to everyone, and a dongle plus GopherTrunk does the same tracking and decoding for free if you have a PC to spare.
Sources
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Trunking Basics — RadioReference Wiki, on control channels, channel grants, and how trunk-tracking scanners follow talkgroups across a trunked system. ↩
Frequently asked questions
What is a trunking scanner?
A trunking scanner is a scanner that can follow a trunked-radio system. Instead of parking on one frequency, it reads the system’s control channel, learns which voice channel each talkgroup has been assigned, and jumps there automatically — so a conversation that hops across many channels sounds continuous.
Do I need a trunking scanner?
If your local police, fire, or EMS use a trunked system — most metro agencies do — then yes. A non-trunking scanner can only catch scattered, disconnected fragments of a trunked conversation. Check your county on RadioReference: if it lists a Motorola, P25, EDACS, or LTR system, you need trunk-tracking.
Is a trunking scanner the same as a digital scanner?
No — they are separate capabilities. Trunking is about following talkgroups across channels; digital is about decoding P25/DMR/NXDN voice. A system can be analog-trunked (needs trunking but not digital), or digital-trunked (needs both). Match the scanner to your system’s combination.
Which scanners are trunk-tracking?
Uniden’s SDS100/SDS200, BCD436HP/BCD536HP, BCD325P2/BCD996P2, and the analog-only BearTracker BCT15X all trunk-track, as do Whistler’s TRX-1 and TRX-2. The cheap analog handhelds (SR30C, BC125AT, BC75XLT) do not.
Can a trunking scanner hear encrypted talkgroups?
No. A trunking scanner will read the control channel, identify the encrypted talkgroup, and follow it to the voice channel — but it plays silence because it lacks the AES key. No scanner and no SDR, including GopherTrunk, can decode encryption.
What is the cheapest way to follow a trunked system?
A ~$30 RTL-SDR plus free, open-source GopherTrunk trunk-tracks P25, DMR, and NXDN systems on a PC, decoding and logging every talkgroup. A dedicated trunking scanner is more portable and turnkey but starts around $380 for digital.