Security
Anti-jammer devices: setting the record straight
There is no device that neutralises a GPS jammer. There are trackers that detect one. Here is how a jammer works and what a tracker can actually do about it.
Updated · 6 min read · Runic
Short answer
No product neutralises a jammer. What exists are GPS trackers that detect one and react locally — siren or engine immobiliser — even while transmission is blocked. The last position before the blackout stays in the cloud, and the tracker resumes reporting the moment the jammer is switched off.
Key takeaways
- A jammer is illegal and drowns out GSM, GPS, wifi, 3G and UMTS with a far stronger signal.
- Nothing cancels a jammer; a tracker can detect it and act on board.
- The last position before the blackout is preserved and is what the police work from.
What a jammer is and how it works
A jammer is an illegal electronic device that disrupts wireless communication. It blocks the GSM signal, so the tracker's SIM cannot reach the platform, and the GPS signal the device needs to calculate its own position. It can also disrupt wifi, 3G and UMTS, and needs no technical skill — most are switched on with a single button.
It uses the same frequencies as everything else, but at power levels far above the legal limit. Picture a room of people talking normally when one starts shouting: their voice drowns out every other conversation.
What happens during a theft
Thieves switch the jammer on as they approach the vehicle, blocking nearby GSM and GPS signals. The radius is typically a few tens of metres and varies with the power of the unit and the number of masts in the area.
The effect is not permanent. A jammer only disrupts while it is on — once it is switched off, the tracker and every other device start working again.
What a GPS tracker can still do
A current-generation tracker detects the jammer, but while the jammer is active it cannot send anything out. That does not leave it powerless: its on-board functions keep working.
- An audible alarm triggered on jammer detection
- An engine immobiliser that prevents the vehicle starting
- The last valid position, preserved in the cloud before transmission stopped
Alarm and immobiliser: worth enabling?
There are two schools of thought. Enabling them may scare thieves off, but it also tells them a tracker is fitted — so they look for it and destroy it, which makes recovery far harder.
Leaving them off keeps the tracker invisible: once the jammer goes off, the device reports its position again and the odds of recovery improve. Either way, what matters most is hiding the tracker well — a trusted auto-electrician will fit it somewhere safe and hard to reach.
Frequently asked questions
- Do anti-jammer devices exist?
- No. Nothing on the market neutralises a jammer. What exists are GPS trackers that detect one and trigger an alarm or immobiliser locally.
- Is a tracker still useful if a thief uses a jammer?
- Yes. It preserves the last position before the disruption, can trigger an alarm or immobiliser, and resumes reporting as soon as the jammer is switched off.
- Should I enable the engine immobiliser?
- It depends which risk you prefer. It may drive thieves off, but it reveals that a tracker is fitted. If recovery is the priority, many owners leave it off and hide the device well.