Ever since the introduction of radar gun technology, law enforcement officials have been able to use speed guns to assess whether a vehicle is within the speed limit.
Radar technology was first used in World War II, but its history with traffic enforcement started when John L. Barker was asked to develop a radar for the military. The purpose was to solve the specific problem of landing gear damage on PBY Catalina amphibious aircraft.
John Barker, along with Bernard Midlock, upgraded a Doppler radar unit using coffee cans soldered shut to make microwave resonators. The radar unit was installed at the end of the runway (at Grumman’s Bethpage, NY facility), and aimed at landing PBYs.
After the war ended, Barker and Midlock adapted this radar device for auto traffic use, then Barker filed his patent #2629865 in June 1946 and worked with Connecticut State Police by March 1947.
But speed guns as we know them were first used in Chicago, Illinois in April 1954 and invented by Bryce K. Brown. The first officer to issue a speeding ticket using the device was Patrolman Leonard Baldy.
How do they work?
Radar stands for Radio Detection And Ranging; when the radio waves from the officer’s device strike a vehicle, some of the signals are reflected and bounced back towards the gun. Using what is known as the Doppler Effect, the device can calculate the speed of the vehicle based on changes in the value of the returning signal.
A speed radar gun operates on several types of frequency bands, which are designed to detect the electromagnetic waves. The police radar frequencies are split into four main bands: X, K, Ka, and Ku. Each band has certain features and benefits.
X Band
(Image source: missiledefenseadvocacy.org – an image of the largest sea-based X band radar)
X band radar waves are generally 8-12 GHz, though most police speed guns work on 10.5 – 10.550 GHz. This was the original law enforcement radar and, by the mid 1950s, agencies all over the U.S. were using this technology. Although its original actual use was in controlling shipping traffic and navigation.
But why were they wildly popular? because experience proved that one radar device could replace as many as 30 traffic enforcement motorcycles; they eliminated the danger of following people speeding in hazardous chases, and they could detect speeding vehicles from as far as 2-4 miles.
Even though it’s no longer the most used speed gun, its main advantage over K and KA band is that it ́s less affected by poor weather conditions. However, this advantage is outweighed by several significant cons: X band radar guns require a larger antenna and is easy for radar detectors to pick up at long distance. Most of the X band radar guns that are still in service are bulky and frustrating to use.
K Band
In the 1970s, the lower frequency K band radar gun was introduced and still remains the most used type of speed gun. It comprises of frequencies between 18 – 27 GHz, though most police speed guns operate on 24.050 – 24.250 GHz.
The K band operates at a lower power output and higher frequency compared to the X band, hence being harder to detect by jamming devices. Modern speed guns can be used by both a stationary and moving car and track multiple targets.
Ka band
In Europe, the Ka band started being used in the 1980s and this is among the latest band frequencies for police radar guns. It comprises of waves between 33.4 – 36.0 GHz and takes a photo as well as measuring speed.
Though slightly complicated to operate, Ka-bands can work as many as five frequencies compared to the one or two on K and X bands. With its low power output and narrow beam pattern, the Ka-band is the hardest to detect at a long distance and is hence the least likely for drivers to jam.
Ku Band
Even though not very popular with U.S. police forces, the Ku band is commonly used in European countries. It uses a frequency band that is centered on 13.45 GHz but also ranges between 12 – 18 GHz. Ku band is one of the hardest to detect and rarely affected by false alarms.