You can't react to jamming you can't see. By the time a tracker has gone dark and stayed dark, the plant or vehicle may already be on a low-loader. Detection flips that around — it tells you the moment GPS is being jammed, while you can still do something about it. Here's what detection actually involves, and how it differs for a yard full of plant versus a fleet of vehicles.
Why detection matters more than people assume
Most tracking is built to tell you where an asset is. None of it helps once the signal's been deliberately killed — and a thief with a £30 jammer kills it on purpose, precisely so the tracker can't follow. Detection is the missing layer: instead of discovering after the fact that an asset vanished, you get an alert the instant the jamming starts. That early warning is the difference between locking a gate and filing an insurance claim. It also hands you something a silent tracker never will — evidence that jamming occurred, which matters enormously for claims and police.
Two kinds of detection
"Detecting jamming" covers two quite different things, and you may want both:
- On-demand investigation. An RF engineer attends with a spectrum analyser, confirms whether jamming is active, measures it, and uses direction finding to locate the source — a device in a cab, a vehicle parked nearby, or a unit on a machine. This is how you prove a suspicion and find the culprit.
- Continuous monitoring. A device that watches the GNSS band around the clock and reacts the instant jamming begins — sounding an alarm, alerting your team, or calling a monitoring centre. This is the always-on layer for a yard or a high-value asset.
How jamming shows up to a detector
GPS sits at a known frequency — the L1 band near 1575 MHz. When a jammer runs, the noise floor across that band lifts sharply, a signature quite unlike an ordinary dropout in a tunnel or a steel shed. That distinction is the whole skill: ordinary signal loss looks one way, deliberate jamming looks another, and the kit that can tell them apart is RF test equipment, not a tracking app.
Plant and yards vs fleets and vehicles
The principle is identical; the deployment differs. For plant, machinery and depots, detection tends to be fixed — monitoring at the gate or across the yard, plus sweeps of returned hire plant to check nothing's been fitted. For fleets and commercial vehicles, it's mobile — in-cab or in-vehicle monitoring, or investigating a specific vehicle whose tracker keeps cutting out. Either way you end up knowing, rather than guessing.
The tell-tale sign before you call anyone
Did more than one asset lose GPS in the same place at the same time? A single tracker glitching is probably a fault. Several going dark together points hard at jamming — a fault wouldn't hit them all at once. Note the time and what vehicles were on site; that observation is often what turns a hunch into a provable case.
See GPS jammer detection →Detection only — the legal line
Worth being clear: using, supplying or possessing a jammer is a criminal offence in the UK. Everything here is the opposite — lawful, defensive detection. The job is to find jamming, locate it and document it, never to produce it. That's exactly why independent detection evidence carries weight with an insurer or a court.
When to put detection in place
If a yard keeps losing tracker visibility, if high-value plant or vehicles are involved, or if losses keep coinciding with a particular vehicle on site, that's the point to add detection — as a one-off investigation, ongoing monitoring, or both.