Technical Details
20
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 radar, your Pro300
will occasionally receive non-police radar
signals. Since these X-Band 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
Pro300’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).
21
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 distin-
guish 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 equip-
ment. 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.
