What signal jamming is
A signal jammer is a small device that emits radio interference on the same bands GPS and GSM use, drowning out the tracker's ability to receive its location from GPS or transmit it to the control room over GSM. For the few minutes it operates, it tries to make the vehicle invisible.
Jammers are illegal in South Africa but are nonetheless used in organised vehicle theft. A jammer-equipped thief aims to move a vehicle out of normal tracking visibility for long enough to disable the device entirely or reach a stripping location, which is the specific attack anti-jamming is built to counter.
How jamming detection works
Modern trackers detect jamming through signal-pattern analysis. A normal environment shows characteristic noise floors and reception patterns, whereas jamming produces anomalously high interference concentrated on specific bands, a signature the device can recognise.
Crucially, when a tracker detects that pattern it does not simply fall silent. It registers the jamming as an event, transmits an alert over any unaffected channel, and switches into recovery mode on its redundant signals, turning the attack itself into the trigger for a response.
Multi-frequency redundancy is the real defence
The single most important anti-jamming feature is signal redundancy. A jammer typically targets one or two bands, most often GPS and the common GSM frequencies, so a device that also operates on a third channel such as RF can keep reporting as long as one channel stays clear.
This is why approved trackers are predominantly multi-frequency: a single-frequency device is defeated the moment its one band is jammed, while a multi-frequency device forces the attacker to defeat all of its channels at once, which is far harder to achieve in the field.
The jamming alert workflow
The typical sequence when jamming is detected is quick: the tracker raises an internal alert flagging the event, activates its redundant channels to push the alert and current location to the control room, and the control room escalates priority, contacting the owner and, where warranted, deploying recovery resources and coordinating with SAPS.
Often the jamming alert is the first sign of theft at all. The owner may not yet know the vehicle has been taken, but the unusual signal conditions have already flagged it for investigation, which can be the difference between an early recovery and a vanished car.
Can thieves detect or block a tracker?
Sophisticated thieves do try to find and defeat trackers, through jamming as above and by searching for the device to remove it. This is why concealment of the fitment location matters and why no tracker is marketed as completely undetectable; the realistic goal is to make detection slow enough that recovery happens first.
Blocking a tracker with a jammer is possible against a single-frequency device but much harder against a multi-frequency one with detection, because the block itself raises the alert. In practice, a well-concealed, multi-frequency, anti-jamming product is the combination that makes a thief's job slow and risky rather than clean.
Why anti-jamming is now table-stakes
Anti-jamming has shifted from a premium extra to an expectation, and single-frequency products without it are increasingly rare in the approved set. For higher-value vehicles, explicit anti-jamming capability is effectively non-negotiable from an insurer's point of view.
The economics make the case bluntly: a relatively cheap jammer can defeat an expensive tracking arrangement that lacks redundancy, so paying for multi-frequency anti-jamming protects the far larger investment in the vehicle and the cover behind it. Under-specifying here is the costliest saving you can make.
The OneCompare view
Anti-jamming is now table-stakes for vehicle tracking, and for higher-value vehicles explicit anti-jamming capability is non-negotiable. The economics are stark: a relatively cheap jammer can defeat a tracking arrangement that lacks multi-frequency redundancy, so under-specifying here risks the far larger investment in the vehicle.