How far does a jammer reach?

Set a jammer’s power and distance and see when a receiver loses lock. Free-space maths with illustrative figures.

LIVE DEMO · JAMMING RANGE

LOCK LOST

Diagram of a distant satellite, a nearby in-car jammer and a receiver, next to a power scale showing the jammer far above the noise floor and the satellite signal below it.
  • jammer at receiver
  • GNSS signal
  • lock-loss threshold

Illustrative

CONTROLS

10 mW
200 m
JAMMER AT RECEIVER
−72 dBm
J/S RATIO
+56 dB
LOCK
Lost
PATH LOSS
82 dB
LOCK LOST WITHIN
1.2 km

Simulated, with illustrative figures. Runs in your browser; nothing is uploaded.

Assumptions behind the figures
  • GNSS signal at the receiver: −128 dBm
  • Frequency: 1575.42 MHz; antenna gain 0 dBi
  • Standard receiver: degraded at J/S 30 dB, lock lost at 40 dB
  • Robust receiver: degraded at J/S 40 dB, lock lost at 50 dB
  • Antenna nulling removes 20 dB of jammer power

HOW IT WORKS

Why a small transmitter wins

  1. Path loss

    Signals weaken with distance, the jammer’s and the satellites’ alike.

  2. Compare

    The receiver weighs the jammer against satellite signals that are already below the noise.

  3. Lock

    Once jamming exceeds what the receiver’s processing can absorb, it loses lock.

TRY THIS

Things to try

  • Halve the distance and watch the J/S ratio rise by 6 dB
  • Find the distance where a 10 mW jammer stops mattering
  • Turn on antenna nulling and compare the range
  • Compare a car-charger jammer with a 1 W unit

MORE

Other demos

LIVE DEMO

Spot the spoof

Watch a position get dragged away, and which checks catch it.