Radar Terms GlossaryAbsorption - the process, in which incident radiated energy is retained by the medium without being reflected or transmitted on passing through a medium.
Directional Antenna - an antenna that transmits or receives signals only in a narrow angle. Decatur offers police radar w/ K-Band Directional Antenna, such as Decatur Speed Trak Moving Police Radar and Decatur GVP-D Genesis VersaPak Directional Radar Handheld Cordless Police Radar Gun.
Doppler Radar - A radar that detects and interprets the Doppler effect in terms of the radial velocity of a target. The signal received by radar from a moving target differs in frequency from the transmitted frequency by an amount that is proportional to the radial component of the velocity relative to the radar gun. Example of Doppler Radar - Decatur Police Radar Guns. A lot of sports radar guns, such as Bushnell Velocity Speed Gun, are Doppler Radars as well.
Fast Speed Tracking - Track both the strongest and the next faster vehicle at the same time, both in the moving and stationary mode of operation. For example: Track the sports car passing the 18-Wheeler. Most of Decatur Police Radars offer Fast Speed Tracking.
Ghost Effect - Sometimes when a radar signal hits a valid target, clutter may originate from multipath echoes created due to signal reflection from the ground, atmospheric particles or due to ionospheric reflection and/or refraction. The clutter is very bothersome because it appears to move and behave just like another normal target, thereby creating a "ghost". Using a ground map of radar 's surrounding and eliminating all echoes that appear to originate from below the ground may help solve the "ghost" problem.
Half-Power Point - the region of the radar beam where the signal strength drops to 1/2 of that strength measured at the main axis.
K-Band, Ka-Band, K-Bands - Police Traffic radar has been assigned specific frequencies by Federal Communication Commission (FCC). These frequencies are designated by the letters -S, X, K and Ka and are referred to as bands. Older radar guns used S-band frequency, but this frequency is no longer in use. Ka band is the newest frequency used in police radars. Ka band is a wide band which allows police radar guns to operate on a multitude of frequencies. Ka-band: (Frequency 33.4 -36.0 GHz; Wavelength .344 inches)
LASER - Laser is light, so this is not a microwave radar band. The laser radar guns operate in the infrared region, which is invisible to your eye. The infrared region is extremely high in frequency, so it is typically described in terms of wavelength.
LIDAR, also is known as Laser Radar , LADAR - Acronym for Light Detection And Ranging. With a Lidar device, one can measure speed, distance, rotation, chemical composition and concentration of a remote target, such as a vehicle.
Moving Radar - is radar that clocks vehicles while the patrol vehicle is moving. Typically, the targets are those approaching in the opposite lane of traffic but, depending on the radar model, can sometimes be used to clock vehicles going away from the patrol vehicle in the opposite lane or even moving in the same direction (for example, Decatur Genesis II Directional Police Radar or its newest incornation - Decatur Speed Trak Police Radar w/ K-band Directional Antenna). These moving radars also "clock" the patrol vehicle by measuring the speed of the ground passing beneath the patrol car and interpreting this as the patrol speed. This speed is deducted from the closing speed of the target thereby giving its speed.
Pacing means the patrol car matches the suspected violator's speed. This is done with a calibrated speedometer or radar inside the patrol vehicle. When speed radar is used in this manner it is actually reading out the patrol vehicle's speed rather than the target speed and it is up to the officer to ensure that he is indeed matching the suspect's speed. Some jurisdictions may specify a minimum distance over which the pace must take place before it will be admitted into evidence.
Pulse Radar - a refinement of the original K-band radar gun. Pulse Radar can be used from a moving vehicle as well as from a stationary position. Pulse Radar Guns transmit a burst of energy every two seconds.
Radar - Radio Detecting and Ranging
Radar Detector - an electronic device used to find any radar operating in the vicinity.
Radio Wave - Any electromagnetic wave at a frequency between approximately 10 kilohertz and 300,000 megahertz (a radio frequency range).
Reflection - the return of all or part of a sound beam when it encounters the boundary between two media. The most important rule of reflection is that the angle of incidence is equal to the angle of reflection, where both these angles are measured relative to an imaginary line which is perpendicular to the boundary.
Refraction - the process by which a wave is bent or turned from its original direction.
Radar Zone of Influence - the area outside the main power beam or outside the beam width.
Same Direction Tracking - Tracking vehicles from behind or in front of the Patrol vehicle going the same direction while the Patrol vehicle is moving. All Decatur Police Moving Radars and Decatur Polie Radar Guns offer Same Direction Tracking mode.
Same Lane Radar - Uses dual antenna moving radar to clock vehicles ahead or behind a rolling cruiser. Example: Decatur Genesis I Moving Police Radar w/ Dual K-Band Antenna.
Selectable Direction Tracking - this mode of radar operation allows the operator to monitor targets that are only going toward the patrol vehicle, away from it, or in both directions. Example: Decatur GVP-D Police Radar Gun w/ K-Band Directional Antenna
Selectivity - A radar detector 's ability to differentiate between non-police radar signals and the real thing.
Speed of Light - 186282.4 miles/sec or 299,792,458 meters/sec.
Stationary Radar - is operated from a stationary position. Virtually all radars work in this mode and some will also work in the moving mode. Most of sports radar guns and handheld police radar guns are stationary radars.
VASCAR - an acronym for Visual Average Speed Computer and Recorder. This is little more than a glorified stopwatch, whereby the vehicle is timed over a set distance (for example over two white markings in the road surface or over two bridges) an average speed is then automatically calculated. No radio waves or beams of light are emitted and thus this system is unable to be detected by any form of electronic detector.
VG2 - A VG2 Gun is a special device used by law enforcement to identify the presence of a radar detector. It looks like a radar gun, but it does not measure speed. It tells the officer if you are using a radar detector. It works because all radar detectors leak a small amount of signal. Radar detectors are currently illegal in Virginia, the District of Columbia, and most parts of Canada. Radar detectors are also illegal in all 50 states for commercial drivers (truck drivers, bus drivers, taxis and limos). If the above does not apply to you, then you don't have to worry about VG-2. All current Cobra Radar Detectors incorporate special circuitry so that they are invisible to the VG2 Gun.
Wave - transmission of energy through medium. Waves travel in repeating cycles of identical wavelength.
Wave Frequency - the number of cycle of waves that passes a point in one second. Frequency is measure in Hertz (Hz). Wave frequency is inversely proportional to wavelength.
Wavelength - a distance from one point in the wave cycle to the next equivalent point in the same direction as the first. Wavelength is inversely proportional to wave frequency.
Wave Velocity - the speed at which the wave travels. All radio waves and light waves travel at a constant speed, the speed of light (186282.4 miles/sec).
X-band Radar - Radar Frequency tolerance 10.525 GHz25 MHz Frequency range 10.500-10.550 GHz. X-band Radars have been around since the 1960s and operate on a single frequency. Typically their operational range was 20 mph- 90 mph or more. U.K. and Australia ceased using X-band Radar many years ago when the frequency was licensed out to other industries that required access to microwave transmitters (alarm systems etc.).
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