North Carolina RADAR State Practice Exam

What phenomenon produces RADAR blind spots, making speed measurements disappear temporarily?

1. Multi-path beam cancellation effect

2. Moving angular effect

3. Doppler shift

4. False target effect

The correct answer is: Multi-path beam cancellation effect

The phenomenon that produces RADAR blind spots, causing speed measurements to disappear temporarily, is known as the multi-path beam cancellation effect. This occurs when the radar waves reflect off multiple surfaces, such as buildings, vehicles, or terrain, before they reach the target. When these reflected signals combine, they can cancel each other out at certain angles or locations, creating zones where the radar cannot accurately detect speed or distance. This effect is especially prominent in urban environments or areas with a lot of reflective surfaces, leading to the temporary loss of speed readings. Understanding this concept is crucial for interpreting RADAR data accurately because it highlights the limitations of RADAR technology in certain conditions, influencing how an officer might conduct speed enforcement in those areas. The other options, while related to radar technology, describe different phenomena. The moving angular effect pertains to the angle at which a vehicle approaches or leaves the radar, affecting readings but not causing blind spots. Doppler shift describes how the frequency of the RADAR signal changes in relation to the speed of the target but does not lead to blind spots. Lastly, the false target effect refers to scenarios where additional, unintended echoes may appear on the radar screen, but this is distinct from the inherent blind spots caused by multi-path cancellations.