Radar speed gun
The radar speed gun was invented by John L. Barker Sr., and Ben Midlock, who developed radar for the military while working for the Automatic Signal Company (later Automatic Signal Division of LFE Corporation) in Norwalk, Connecticut during World War II.
Originally, Automatic Signal was approached by Grumman to solve the specific problem of terrestrial landing gear damage on the Consolidated PBY Catalina amphibious aircraft.
Barker and Midlock cobbled a Doppler radar unit from coffee cans soldered shut to make microwave resonators.
The unit was installed at the end of the runway at Grumman's Bethpage, New York facility, and aimed directly upward to measure the sink rate of landing PBYs.
Radar guns that operate using the X band (8 to 12 GHz) frequency range are becoming less common because they produce a strong and easily detectable beam.
Also, most automatic doors utilize radio waves in the X band range and can possibly affect the readings of police radar.
[citation needed] However, MythBusters did an episode on trying to get the gun to have incorrect readings by changing the surface of the passing object and found no significant effect.
This can occur if the position of the radar is too close to a larger reflective target such as a tractor trailer.
An antenna diameter of less than several feet limits directionality, which can only partly be compensated for by increasing the frequency of the wave.
Size limitations can cause hand-held and mobile radar devices to produce measurements from multiple objects within the field of view of the user.
Side lobe detections can be eliminated using side lobe blanking which narrows the field of view, but the additional antennas and complex circuitry impose size and price constraints that limit this to applications for the military, air traffic control, and weather agencies.
Distance measurements require pulsed operation or cameras when more than one moving object is within the field of view.
Once again falling back on the training and certification requirement for consistent and accurate visual estimation so that operators can be certain which object's speed the device has measured without distance information, which is unavailable with continuous wave radar.
Some sophisticated devices may produce different speed measurements from multiple objects within the field of view.
There may be an unnoticed airplane overhead, particularly if there is an airport nearby, which again emphasizes the importance of proper operator training.
Conventional radar gun limitations can be corrected with a camera aimed along the line of sight.
This can be reliable for traffic in city environments when multiple moving objects are within the field of view.
This is reliable in city traffic because LIDAR has directionality similar to a typical firearm because the beam is shaped more like a pencil that produces measurement only from the object it has been aimed at.
