How Does a Police Radar Gun Work?

Police officers in North America have been using radar guns to catch speeders since 1949. This relatively simple technology evolved from military applications before World War II, where long-range installations were the size of a medium-size apartment building. Modern radar guns aren’t quite pocket-sized, but they are easily transportable and can be hand-held or installed permanently in a police vehicle. Let’s look at how a radar gun works.

How Does Speed-Detecting Radar Work?

In simple terms, a radar gun transmits a narrow beam of radio-frequency energy out the front of the gun and looks for that signal to be reflected back to the gun after bouncing off an object. Unlike lidar and laser guns, the speed measurement is calculated by how much the received signal has changed in frequency after reflecting off the moving object. This phenomenon is called a Doppler effect and is the same reason that a car sounds different as it approaches and drives away from you.

Please Explain Doppler Effect to Me!

Imagine that you have a tennis ball machine shooting balls at a stationary object once every second. The balls bounce back to the machine and arrive once per second. If you start to move the object toward the ball launching machine, the balls bounce back faster and faster as the object approaches the machine. This increase in return speed represents an increase in frequency.

If an object is moving away from the tennis ball machine, it will take longer for each ball to bounce back, thus representing a decrease in frequency. The digital signal processor in modern radar guns is configured to analyze the changes in the reflected signal very quickly and display a speed reading in less than a second.

Different Radar Bands

In North America, police officers use radar guns that operate in the X, K and Ka band frequency ranges. X band is the oldest technology and operates between 8 and 12 GHz; the K band is between 18 and 27 GHz; and the Ka band is between 27 and 40 GHz. X band radar is prone to interference from automatic door opening systems. K band (K is short for Kurz, which is the German word for short) and Ka (K-above band) radar are less resistant to atmospheric absorption than X band and less effective over long distances. Most of the new radar guns such as the Stalker II and the Kustom Talon use Ka band signals, so if your detector goes off, you know you need to react right away.

Radar Detectors Provide Early Warnings

Unlike lidar, the radar signal isn’t as precise at long distances, allowing it to spread well beyond the vehicle being measured. The high-sensitivity radar receiver in a radar detector is tuned to pick up extremely low-level signals and alert you that radar is in use. You need to act quickly when a radar detector goes off. Your local specialist mobile enhancement retailer can help you choose the perfect portable or custom-installed radar for your application and ensure that the system is installed cleanly. Drop by and find out what’s available today!

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