Car radar detectors are derived from the same technology that the military uses.
Radar detectors have undergone a lot of change during the perpetual arms race between drivers and law enforcement. Modern radar detectors approach levels of technology that were undreamed of ten years ago, but are illegal in some places.
Radar Guns
The speed checkers used by law enforcement emit a beam of highly-focused radio energy or laser light. When this beam encounters an object, the gun calculates the distance and time it took for the beam to bounce back and extrapolates speed from the data.
Detectors
A radar detector is a passive "listening" device that receives the energy emitted by speed checkers and notifies the driver.
Bands
The most common radar bands used are denoted by letters: X-Band (7.0 to 11.2 GHz), K-Band (20-40 GHz), Ka-Band (any GHz above the K band). The higher wavelength of the X-Band allow for more accuracy and imaging, but shorter range than the other two.
Laser
Many agencies utilize Laser (LIDAR) guns that sense with light instead or radio energy. By the time a detector senses LIDAR, it's probably already too late to slow down.
VG-2 Detectors
Police have equipment that can detect older radar detectors. Modern units use a VG-2 array that senses these "detector detector," triggering an immediate shut-down of the unit to avoid detection.
Tags: radar detectors, radio energy, speed checkers, technology that