Before this:What is trunked radio?The FFT & reading a waterfall
Finding & identifying systems
Key takeaways To monitor a trunked system you first need its control- channel frequency. The fastest route is an online database (like RadioReference) that lists systems, control channels, talkgroups, and types by location. Cross-check on the waterfall by spotting the steady, always-on control channel. For unknown systems, GopherTrunk’s Hunt sweeps a band to discover active control channels. Then add or import the system and GopherTrunk locks on and follows calls.
Module 6 puts the whole path to work. The very first practical task is finding something to listen to — specifically, a system’s control channel, the key that unlocks everything else.
Online databases — start here
The easiest way to find systems is to look them up. RadioReference (and similar regional databases) catalogue known systems by location, listing:
- the system type (P25, DMR, etc.),
- the control-channel frequencies,
- the talkgroups and what they’re used for,
- and often radio IDs and notes.
For most populated areas, your local systems are already documented. Grab the control-channel frequency and system details, and you’re 90% of the way there. This beats blind scanning almost every time.
Scanning a band for control channels
When a system isn’t documented, or you want to confirm one, look on the waterfall. In the band the system uses, hunt for the tell-tale control-channel footprint:
- continuous — it’s always transmitting, unlike voice channels that flicker on/off;
- fixed width — a narrow, consistent digital signal;
- steady strength — it doesn’t come and go.
That always-on stripe among intermittent voice bursts is your candidate.
Using GopherTrunk Hunt
Scanning by eye is slow. Hunt automates it: point it at a frequency range and it sweeps for active control channels, surfacing candidates for you to identify and add. This is the tool for unknown or undocumented systems — it turns “is there anything here?” into a list of real signals to investigate.
Identifying a system from its control channel
Once you’ve locked a candidate control channel, the signalling identifies the system. GopherTrunk reads the control-channel data to determine the protocol and system parameters (system ID, etc.), so you can confirm what you’ve found and match it against a database entry. The protocol landscape lesson helps you interpret what you’re seeing.
Adding a system to your configuration
With a confirmed control channel (and ideally its talkgroup list), you bring it into GopherTrunk:
- Add the system and its control-channel frequency to your configuration.
- Import talkgroups and details in bulk from CSV or a database export, rather than typing them.
- Bookmark frequencies and systems you’ve found for later.
GopherTrunk then locks the control channel, reads its running commentary, and begins following calls — exactly the antenna-to-audio flow, now pointed at a real system you found. If the control channel won’t hold a clean lock, the next two lessons — tuning with scopes and calibration & troubleshooting — are where you go.
Quick check: what's the single most important frequency to find for a trunked system?
Recap
- You need a system’s control-channel frequency above all.
- Databases (RadioReference) are the fastest source of systems, control channels, and talkgroups.
- Confirm on the waterfall by the control channel’s steady, always-on footprint.
- Hunt discovers undocumented systems automatically.
- Add or import the system, then GopherTrunk locks on and follows calls.
Next: when a control channel is marginal, how to read the scopes and dial in a clean lock.
Frequently asked questions
How do I find trunked radio systems near me?
Start with an online database such as RadioReference, which lists known systems, their control-channel frequencies, talkgroups, and types by location. Cross-check by looking at the waterfall for a steady control-channel signal in the listed band. If a system isn’t in a database, you can scan the band yourself or use GopherTrunk’s Hunt feature to discover active control channels.
What is a control channel frequency and where do I get it?
A trunked system’s control channel is the always-on data frequency that coordinates it. You get it from a database listing for the system, or by finding the steady, fixed-width digital signal on the waterfall in the system’s band. GopherTrunk needs at least one working control-channel frequency to start following a system.
What does GopherTrunk's Hunt feature do?
Hunt sweeps a frequency range looking for active control channels, helping you discover systems you don’t already have frequencies for. It surfaces candidate control channels so you can identify and add them, which is especially useful for unknown or undocumented systems in your area.
How do I add a found system to GopherTrunk?
Once you have a system’s control-channel frequency (and ideally its type and talkgroup list), you add it to your GopherTrunk configuration, or import details from CSV or a database export. GopherTrunk then locks the control channel, reads the system parameters, and starts following calls.