As you will discover, the S DSR 2X that you have purchased is extremely sensitive resulting in longer range. If care is not
taken when installing the radar in the vehicle, this extra sensitivity may allow you to pick up Fan Noise when operating the radar from
inside the patrol vehicle. Fan Noise can result in erroneous high-speed readings when operating in Same Lane mode – particularly
with Same Lane Faster mode enabled.
Fan Noise Is Common
Fan Noise is a common Doppler radar problem when aiming the antenna through a window from inside the patrol vehicle. Doppler
radar is designed to detect moving or vibrating objects. A small amount of the radar beam is reflected from the glass back into the
vehicle. This beam reflection may allow the radar to "see" the vibrating defroster vents or the vehicle dash that is vibrating as a result
of the fan blower motor. If the antenna is mounted close to the top surface of the vehicle dash, the radar beam can "see" a portion of
the vehicle dash that is vibrating. We recommend mounting the front antenna as high on the glass windshield as is feasible. Higher
mounting will also result in better patrol speed tracking and longer operational range. Fan Noise can be verified by turning off or
changing the speed of the fan.
Most fans generate speeds of 30 mph or less. As a result, Fan Noise is normally a problem when operating in Stationary mode or
when operating in Moving mode with patrol speeds less than 30 mph or operating in Same Lane mode (particularly Same Lane Faster
Opposite Lane operation: since opposite lane radar only sees Doppler signals above the patrol speed, Fan Noise will not affect an
opposite lane radar operating at patrol speeds above about 15 mph.
Stationary operation: a radar operating in Stationary mode will see Doppler signals from 5 mph to 200 mph. Clearly, a Fan Noise
signal between 5 mph and 30 mph will be seen and result in false readings.
Same Lane operation: a same lane radar adds or subtracts the difference speed (patrol vehicle - target vehicle) to obtain the absolute
target speed. This difference speed is commonly between 5 mph and 30 mph. Clearly, a Fan Noise signal between 5 mph and 30 mph
will be seen and result in false readings.
ALERT: It is critical that you eliminate Fan Noise false readings for the S DSR 2X if you
use the factory defaults with Same Lane Faster mode enabled.
How to check for Fan noise:
1. Operate the S DSR 2X in XMIT mode, Opposite/Same Stationary, and SEn 4.
2. Turn your vehicle fan motor to the "highest" speed.
3. Locate your stationary vehicle so that the radar beam is clear of moving objects or large reflective objects.
4. Fan Noise can be verified by turning off or changing the speed of the fan.
5. Verify that no speed readings are observed – realize that moving trees or grass can result in speed readings corresponding to
the speed of the wind.
6. Move the antenna (as required) until a location is found that results in no Fan Noise readings above about 4 mph – a high
corner of the windshield is usually best.
7. As a last resort, mount the antenna completely outside the vehicle.
8. If a rear antenna is used, repeat the testing for this antenna.
To Eliminate Fan Noise, try the following steps in numerical order:
1. Find a location (by moving the antenna) inside the vehicle that is free of Fan Noise; such as the upper left corner of the
2. Ensure that the antenna beam is not deflected back into the vehicle by anything in its path such as wipers, window trim, or
anything mounted on the dash. Do not mount the counting/display unit or antenna/power cables in front of the antenna on the
3. Locate the antenna as close to the glass surface as possible (preferably less than 1/2 inch).
4. Turn the fan off while operating the radar in stationary mode or moving mode with patrol speed under 30 mph or Same Lane
mode – especially with Same Lane Faster mode enabled.
5. As a last resort, turn Same Lane sensitivity from 4 down to 3 ( SEn 3) or mount the antenna completely outside the vehicle.
AVOIDING FAN NOISE