Police Radar Basics – Hardware

Categories: Uncategorized | Posted on Mar 27, 2018

 

POLICE RADAR BASICS – HARDWARE Police radars come in 2 basic configurations or styles… and have 1 to 3 speed windows. Antenna alignment is critical, especially in moving mode. There are several optional features, not all radars have all options. Electrical noise is a concern for units powered by the car battery. Last, but not least, record keeping. Police radars come in a hand-held configuration, a radar gun, … or a multiple unit system mounted to the patrol car. Hand held radars are single piece units shaped like an over sized pistol and aimed in a similar manner. These radars can be used from inside or outside the patrol car. Multi-unit radars are mounted to the patrol car. All mounted radars have a front antenna. Here, a front view of the front antenna is shown. Many radars have an additional rear antenna. Here a side view of the second antenna is shown. The Computer Processor, or Counter, is a separate unit. Some models have the Speed Display attached to the Computer, some have the display as a separate unit. Some hand-held radars, and all mounted radars, have a remote control. Some remotes are wired and some are wireless. All microwave sport and police radars can be tested with tuning forks.

All police radars come with tuning forks that are specifically tuned for that radar. Tuning forks are used to check radar accuracy on a daily basis. Two forks are required to test moving mode. All police radars have speakers for the target tone, the higher the tone the higher the target speed. [ Frequency Sweep ] [ 65 MPH Target Tone ] [ 80 MPH Target Tone ] Speed window arrangement varies with manufacturer and model.

All radars have a target speed window, it displays the strongest target reflection, usually the closest vehicle in the beam. [ 67 MPH Target Tone ] [ 65 MPH Target Tone ] [ 78 MPH Target Tone ] [ 67 MPH Target Tone ] All moving mode radars have a dedicated patrol speed window. Moving mode radar measures ground speed to calculated target speed. Radars do not emit an audio tone for patrol speed. Most radars can save a target speed in a separate “Lock” speed window. [ Fast Forward ] [ BEEP } Some radars can measure 2 targets at the same time, the “Strongest” and the “Fastest” targets. Fastest target speeds are usually displayed in the “Lock” window. [ 52 MPH Target Tone ] [ 59 MPH Target Tone ] The radar antenna beam must be aimed at “Down-the-Road” traffic. In this example the radar has a 12 degree beam angled 6 degrees to traffic — optimum alignment. Moving mode operation requires the radar antenna be mounted straight and level. Examples of correct alignment and incorrect alignment. A misaligned antenna causes a low patrol speed reading in all moving modes, and a high target speed reading for on-coming traffic. The greater the misalignment, to the right or left, the greater the speed error.

 

All mounted radars have a front antenna. Many also have a rear antenna. Some radars are connected to the patrol car speedometer. This makes for more reliable readings and lessons operator workload in moving mode. Some radars send data to a dash camera or a recording system. Data includes, radar mode, target and patrol speeds, and active antenna, front or rear. Hand held radars are powered by an internal battery or the patrol car DC plug Most mounted radars are powered by the patrol car battery. The most basic connection is the radar gets power from the patrol car DC plug. A noisy electrical system may cause interference. Sometimes a filter installed in the passenger compartment can fix the problem. The best connection is a shielded cable directly to the battery. In extreme cases a separate battery pack, isolated from the car electrical system, is required.

Radar records should be available, accurate, complete, and up to date. All radars come with an “Operator’s Manual”, and factory certificates of calibration for the radar and tuning forks. Police should maintain installation and maintenance records, including repair orders, date and vehicle radar installed, and all electrical and electronic interfaces. The radar operator or an administration should maintain calibration records, tuning fork test records, and event logs and notes. Information to look for on the factory radar certificate includes… radar serial number, the tuning fork serial numbers that are tuned for and supplied with the radar… and the radar transmit frequency. Test documents should be traceable to the factory radar certificates. Tuning fork documents should include the radar transmit frequency used to calibrate the tuning forks. The speed a tuning fork registers on a radar depends on fork resonance and radar frequency.

To determined registered speed, in miles per hour, multiply 0.3353 by the fork resonance in Hertz, then divide that by the radar transmit frequency in gigahertz..

As found on Youtube