Decatur Electronics SI-3 - Fan Interference; Electromagnetic Interference (EMI); Feedback Interference; Multi-Path Beam Cancellation

SI-3
™
User’s Manual
18
Small angles (less than 10°) have little eect on accuracy. As the
angle increases, the displayed speed decreases. At 90°, the target
speed is 0—grossly incorrect.
5.2.2 Fan Interference
Fan interference is one of the most common forms of interference
that you are likely to experience. It is caused when the radar
measures the speed of a blower fan that is with in the beam path of
the radar. If the SI-3™ is used inside of a building keep in mind that
furnace and air conditioner fans can cause interference. To correct
this, relocate the radar so it does not display spurious speeds or
turn o the fan motor.
5.2.3 Electromagnetic Interference (EMI)
Operating electric motors can produce EMI. EMI from power seats
or windshield wipers can also produce spurious target speeds. To
correct the interference, simply turn o its source.
5.2.4 Feedback Interference
When the radar beam is directed at computer screens, streetlights,
and other electronic devices, it can display spurious speeds. To
correct the interference, relocate the SI-3™.
5.2.5 Multi-Path Beam Cancellation
If multi-path beam cancellation occurs, the target vehicle speed
sporadically blinks and reappears at semi-random intervals. This
type of interference occurs when the radar loses track of a target
because the target is reecting two or more signals, which are
interfering with each other. The SI-3™ is immune from multi-path
cancellation.
5.2.6 Radio Frequency Interference (RFI)
The system can inadvertently process radio energy as Doppler
speeds, including that from 2-way radios, airport radar, microwave
transmission towers, CB radio transmitters, and AM/FM
transmission towers. For this type of interference to occur, the SI-3™
must be operating very close to the radio transmitter.