Beltronics STi-R - Manual (Page 11)

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Technical Details
How Radar Works
Traffic radar, which consists of
microwaves, travels in straight lines and is
easily reflected by objects such as cars,
trucks, even guardrails and overpasses.
Radar works by directing its microwave
beam down the road. As your vehicle
travels into range, the microwave beam
bounces off your car, and the radar
antenna looks for the reflections. Using
the Doppler Principle, the radar
equipment then calculates your speed by
comparing the frequency of the reflection
of your car to the original frequency of the
beam sent out.
Traffic radar has limitations, the most
significant of these being that it typically
can monitor only one target at a time. If
there is more than one vehicle within
range, it is up to the radar operator to
decide which target is producing the
strongest reflection. Since the strength of
the reflection is affected by both the size
of the vehicle and its proximity to the
antenna, it is difficult for the radar
operator to determine if the signal is from
a sports car nearby or a semi-truck
several hundred feet away.
Radar range also depends on the
power of the radar equipment itself. The
strength of the radar unit’s beam
diminishes with distance. The farther the
radar has to travel, the less energy it has
for speed detection.
Because intrusion alarms and motion
sensors often operate on the same
frequency as X-Band or K-band radar, your
STi-R will occasionally receive non-police
radar signals. Since these transmitters are
usually contained inside of a building, or
aimed toward the ground, they will
generally produce much weaker readings
than will a true radar encounter. As you
become familiar with the sources of these
pseudo alarms in your daily driving, they
will serve as confirmation that your STi-R’s
radar detection abilities are fully
operational.
How “POP” Works
“POP” mode is a relatively new feature for
radar gun manufacturers. It works by
transmitting an extremely short burst,
within the allocated band, to identify
speeding vehicles in traffic. Once the
target is identified, or “POPPED,” the gun
is then turned to its normal operating
mode to provide a vehicle tracking history,
(required by law).
How Laser (Lidar) Works
Laser speed detection is actually LIDAR
(Light Detection and Ranging). LIDAR
guns project a beam of invisible infrared
light. The signal is a series of very short
infrared light energy pulses, which move,
in a straight line, reflecting off your car
and returning to the gun. LIDAR uses
these light pulses to measure the distance
to a vehicle. Speed is then calculated by
measuring how quickly these pulses are
reflected given the known speed of light.
LIDAR (or laser) is a newer technology
and is not as widespread as conventional
radar, therefore, you may not encounter
laser on a daily basis. And unlike radar
detection, laser detection is not prone to
false alarms. Because LIDAR transmits a
much narrower beam than does radar, it is
much more accurate in its ability to
distinguish between targets and is also
more difficult to detect.
AS A RESULT,
EVEN THE BRIEFEST LASER ALERT
SHOULD BE TAKEN SERIOUSLY.
There are limitations to LIDAR
equipment. LIDAR is much more sensitive
to weather conditions than RADAR, and a
LIDAR gun’s range will be decreased by
anything affecting visibility such as rain,
fog, or smoke. A LIDAR gun cannot
operate through glass and it must be
stationary in order to get an accurate
reading. Because LIDAR must have a clear
line of sight and is subject to cosine error
(an inaccuracy, which increases as the
angle between the gun and the vehicle,
increases) police typically use LIDAR
equipment parallel to the road or from an
overpass. LIDAR can be used day or night.