Technology
GPS Interference and Jamming
Quick fact
A GPS jammer as small as a cigarette pack can disrupt GPS signals across an area of several hundred square kilometers, because GPS signals reaching Earth are weaker than a whisper.
Why this is interesting
Your phone can pinpoint your location anywhere on Earth, but a $50 device the size of a phone can silence that ability for miles. How can such a powerful technology be so easily disrupted?
Read the full explanation
Understanding GPS Interference and Jamming
Imagine trying to hear a friend whisper across a noisy stadium. GPS satellites broadcast a faint radio signal from 20,000 kilometers away. By the time it reaches your device, the signal is incredibly weak—weaker than the background noise in the radio environment. Your GPS receiver works by picking out this whisper from the noise, using a special code. For it to lock on, the signal must be just slightly stronger than the background noise—measured as signal-to-noise ratio. A jammer works by blasting a strong radio signal on the same frequency, drowning out the whisper. Once the noise is too loud, the receiver can no longer distinguish the satellite's signal, and it loses its position lock.
A deeper explanation
The vulnerability lies in the signal-to-noise ratio. The GPS signals are deliberately weak because they must travel huge distances and are broadcast at a limited power, controlled by regulations to avoid interference with other services. The receiver's ability to process these signals is based on its antenna and how it uses spread-spectrum technology, which gives it some resilience—it can even use signals that are below the noise floor by correlating the known code. However, this processing gain is limited. When a jammer transmits a signal on the L1 frequency (1575.42 MHz) that is stronger than the normal signal by a certain threshold, the receiver's correlation cannot overcome the interference. The result is a loss of lock, often causing the receiver to report no position, or worse, an inaccurate one. This matters enormously because GPS is not just for navigation—it synchronizes power grids, financial transactions, and telecommunications. An intentional jamming attack, even a small one, can disrupt critical infrastructure without any physical damage.