Scanning & Monitoring — the practical craft of listening to the radio spectrum

The Digital & Trunked Radio module explains how these systems work on the inside; this one is about actually listening to them. Scanning is the decades- old hobby of monitoring the radio spectrum — public safety, utilities, aviation, business — and this module is the practical craft of doing it well and legally. Start with what scanning is and what you can and can't hear today, build a real listening station out of a scanner or SDR and a decent antenna, learn to find and identify systems in the field, follow trunked calls across a system, and log, record, and share what you hear. It finishes by turning GopherTrunk into an always-on monitoring post. Pairs with the RF & SDR and Digital & Trunked Radio modules; it assumes only curiosity, and everything here stays firmly on the right side of the law.

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The Digital & Trunked Radio module explains how these systems work on the inside. This one is about actually listening to them. Scanning is the decades-old hobby of monitoring the live radio spectrum — public safety, utilities, aviation, business, and more — and it’s a craft with its own skills: building a station, finding what’s out there, following a call the instant a radio keys up, and capturing it all so you can come back to it.

Who this is for. Anyone curious about what’s on the air above them — new to the hobby or a longtime listener who wants the trunked, software-defined side to click. It assumes no background beyond curiosity. It pairs with the RF & SDR module (how radio and SDR work) and the Digital & Trunked Radio module (how the systems you’ll follow are built). Everything here stays firmly on the right side of the law.

How the module works. Six units take you from switching on a receiver to running an unattended monitoring post. The first two cover the hobby and the station — what you can hear, and the receiver and antenna that let you hear it. The middle two are the core skills: finding and identifying systems, and following trunked systems in the field. The last two cover logging, recording, and sharing what you hear, and doing all of it with real software — turning GopherTrunk into an always-on monitoring post. Mark lessons complete as you go — your progress is saved in your browser. New here? Start with lesson 1: What radio scanning is

Unit 1 — The Scanning Hobby

What radio scanning is and the ground rules: a short history, conventional versus trunked, what's listenable today, and the legal and ethical lines.

  1. What radio scanning is The hobby of monitoring live radio traffic — who's on the air, why people listen, and what a modern scanning setup actually does. beginner 8 min
  2. A short history of scanners From crystal-controlled boxes to SDR — how scanners evolved alongside the radio systems they follow, and why that history still shapes the hobby. beginner 8 min
  3. Conventional vs. trunked, in the field The one distinction that changes how you scan — a fixed channel you can park on versus a trunked system you have to follow — from the listener's chair. beginner 8 min
  4. What you can (and can't) hear today A realistic tour of the spectrum — the analog and unencrypted traffic still open, and the encrypted systems that have gone dark. beginner 9 min
  5. Legal & ethical scanning The rules that keep the hobby healthy — what's legal to receive, what's not legal to do with it, and the etiquette of responsible monitoring. beginner 9 min

Unit 2 — Your Listening Station

The gear that puts signals in front of you: scanners versus SDR, choosing hardware, antennas and feedlines, station setup, and beating noise.

  1. Hardware scanners vs. SDR The two roads into the hobby — a dedicated scanner you switch on versus an SDR and software like GopherTrunk — and what each is best at. beginner 9 min
  2. Choosing a scanner or SDR Matching hardware to what you want to hear — bands, trunking support, and budget — so you buy the right receiver the first time. beginner 9 min
  3. Antennas for scanning The single biggest upgrade to what you can hear — discones, verticals, and the difference the right antenna makes over the stock whip. intermediate 10 min
  4. Feedlines, connectors & grounding The unglamorous parts that quietly cost you signal — coax loss, connectors, and grounding your station safely. intermediate 9 min
  5. Setting up your station Putting it together — receiver, antenna, and computer — into a working monitoring setup, indoors or on a rooftop. intermediate 9 min
  6. Reducing noise & interference Why the city is loud on the radio — where local noise comes from, how to hunt it down, and the filters and habits that cut it. intermediate 9 min

Unit 3 — Finding What to Listen To

Turning a quiet radio into a busy one: system databases, band plans, searching and discovery, identifying unknown signals, and keeping records.

  1. RadioReference & system databases The scanning community's shared map of the airwaves — how databases like RadioReference tell you what's on the air near you. beginner 9 min
  2. Band plans & where services live The spectrum has a floor plan — the bands where public safety, business, aviation, and the rest live, so you know where to look. intermediate 9 min
  3. Search, scan & discovery Finding what the databases don't list — searching a band, spotting active channels, and close-call techniques for catching nearby transmitters. intermediate 9 min
  4. Identifying an unknown signal You found a signal — now what is it? — using the waterfall, bandwidth, and modulation to name a mystery transmission. intermediate 10 min
  5. Building your frequency records Turning what you find into a reusable log — organising frequencies, talkgroups, and notes so your setup gets smarter over time. beginner 8 min

Unit 4 — Following Trunked Systems

The heart of modern scanning: programming a trunked system, working with talkgroups and scan lists, following a call, multisite and roaming, and troubleshooting.

  1. Programming a trunked system Getting a scanner or SDR to follow a trunked system — the control channel, system parameters, and what you actually enter to track it. intermediate 10 min
  2. Talkgroups, scan lists & priorities Deciding what you hear — organising talkgroups into scan lists, locking out the noise, and setting priorities so you never miss the calls you care about. intermediate 9 min
  3. Following a call across the system What happens in the seconds after a radio keys up — how your setup follows a grant from the control channel to the voice channel and back. intermediate 9 min
  4. Multisite, simulcast & roaming Big systems have many sites — picking the right one to monitor, what simulcast does to your signal, and following units as they roam. advanced 10 min
  5. When decoding fails The field troubleshooting guide — no control-channel lock, garbled voice, missed calls — and how to tell a signal problem from a setup problem. advanced 10 min

Unit 5 — Logging, Recording & Sharing

Getting value out of what you hear: logging and recording calls, tagging them, streaming feeds, alerting on what matters, and building an always-on post.

  1. Logging & recording calls Capturing traffic so you can review it later — call logging, per-call recording, and the storage that a busy system quickly demands. intermediate 9 min
  2. Metadata, tagging & searchability A recording is only useful if you can find it — tagging calls with talkgroup, time, and system so a month of audio stays searchable. intermediate 8 min
  3. Audio feeds & streaming Sharing what you hear — how live scanner feeds like Broadcastify work, and what it takes to put one on the air responsibly. intermediate 9 min
  4. Alerting on the calls you care about Letting the setup watch for you — triggers and alerts on specific talkgroups or keywords so you're notified when something happens. intermediate 9 min
  5. Building an always-on monitoring post Going from "switch it on when I'm home" to a setup that runs unattended — the hardware, software, and reliability of a 24/7 post. advanced 10 min

Unit 6 — Scanning With GopherTrunk

Everything applied with real software: SDR scanning tools, GopherTrunk as a scanner, a full worked setup, the community, and where to go next.

  1. Scanning with SDR software The software side of SDR scanning — the tools that turn a raw receiver into a trunk-tracking scanner, and where GopherTrunk fits among them. intermediate 9 min
  2. GopherTrunk as a scanner Using GopherTrunk to follow and decode a real system — the control channel, the calls it grants, and the audio that comes out. advanced 10 min
  3. A worked end-to-end monitoring setup Start to finish — antenna, SDR, GopherTrunk, logging, and a dashboard — assembled into a complete, always-on monitoring station. advanced 11 min
  4. The community & contributing data The hobby runs on shared knowledge — the forums, databases, and open-source projects, and how to give back the systems and fixes you find. beginner 8 min
  5. Where to go next Where the hobby leads — decoding data modes, digging into protocols, or writing your own decoder — and the modules that take you there. beginner 8 min
  1. Glossary of scanning terms Plain-language definitions for every term in the module — scanner, SDR, control channel, talkgroup, scan list, lockout, simulcast, multisite, roaming, feed, discone, squelch, close call, and more — cross-linked to the lessons.