Stalker Blog / A Brief History of Police Radar

A Brief History of Police Radar

Radar speed detection capabilities were first developed in 1935 in Great Britain by Sir Robert Watson-Watt and his assistant Arnold Wilkins. They figured out how to use radio waves to detect enemy planes at great distances and also utilized this technology to locate German U-boats. He later helped the United States to expand their radar capabilities in the aftermath of the Pearl Harbor bombing.

Do You Know How Fast You Were Going?

It did not take long for law enforcement agencies to recognize the power of this new radar technology. In 1947, Glastonbury, Connecticut started testing out radar to survey the speed of passing vehicles, debuting the world’s first “speed trap” in February of 1949. Officers would work in pairs, with one officer watching the radar system and collecting visual and printed evidence from passing cars. When the first officer noticed a speeder, he would radio an officer parked a short distance up the road, giving him the offending vehicle’s plate number. The second officer would wait for the car to pass, pull over the driver, and issue them a ticket.

Sizing Up the Problems

There were several issues with this technology that would be solved over the following years. The first was the problem of size. Early radar systems were quite large- starting off weighing hundreds of pounds. As they came into use in war planes, technology was developed that enabled them to be manufactured considerably smaller. Later, they were sized to fit into the trunks of patrol cars, eventually shrinking down to the dash-mounted and hand-held units we see today.

X-Band: Evolution

The second issue was that of frequency or “band.” Initially, police radar operated in the X-band or Ku-band frequencies. These bands required the radar housings to be very long to accommodate the frequencies’ longer wavelengths- so long, in fact, that the antenna had to be mounted on the outside of the patrol vehicle. X-band frequencies are also not able to be used in “direction-sensing” radar, meaning that they are only able to detect differences in speed between the patrol car and the car in question, but aren’t able to determine if that car is moving towards or away from the officer. This can make it difficult for officers to calculate speeds quickly.

Over time, higher-frequency K- and Ka-band radars were introduced. This allowed the antenna to shrink down to something that could be mounted to the dashboard of a patrol car or could fit into a handheld radar gun. But the biggest advantage of these frequencies is that they are directional and have a much higher resolution. Now police radars can have “Fastest” and “Strongest” signal displays, which allow officers to pinpoint speeds of smaller cars and motorcycles even when they are near to larger vehicles that put out a much stronger radar signal.

Going Digital

Changes in radar size were accompanied by changes in the radar’s display. Initially, radar displays were in a dial format, where a needle would point to the speed of the car being observed. While the displayed result was accurate, it would come and go in the blink of an eye- not the most accurate method! In 1969, digital readouts were introduced on the new radar models, making them much easier to read.

Getting In Tune

1969 was also the year that tuning forks started to be widely used to calibrate radars. Prior to this, a radar would be calibrated by having a patrol vehicle driving at a specific speed pass by the radar unit. All speeds measured by the device that day would be calculated relative to this “calibrated” speed. Tuning forks eliminated the inaccuracies and “operator errors” that plagued the “drive-by” method.

Radar Á la Mode

Various “modes” have been developed to make obtaining accurate radar readings much simpler. In 1972, moving mode radar was created. This allowed an officer to calculate traffic speeds while driving. Previously, officers only had the option of stationary mode, meaning their patrol car had to be parked while measuring the speed of passing vehicles. In 1985, same direction radar (aka, “same lane”) radar made it easier to accurately calculate the speed of traffic that was moving in the same direction as the patrol vehicle (while also allowing the officer to easily switch focus to traffic moving towards their vehicle if they desired). In 1993, the IACP allowed manufacturers to add “Fastest” modes to their radars, which allowed the units to display information about the strongest target (usually either the largest or closest vehicle) and the fastest target (which, until the introduction of K- and Ka-band radar, was impossible).

Full Circle

We’d like to conclude with an ironic poem by Sir Robert Watson-Watt, mentioned earlier in this article as the inventor of the radar technology that allowed the British to detect German plans and submarines via radio waves. In 1956, a police officer using a radar gun pulled him over and issued him a speeding ticket. Here were his thoughts on the matter:


“Rough Justice”
by Sir Robert Alexander Watson-Watt

Pity Sir Robert Watson-Watt,
strange target of this radar plot
And thus, with others I can mention,
the victim of his own invention.
His magical all-seeing eye
enabled cloud-bound planes to fly
But now, by some ironic twist
it spots the speeding motorist
and bites, no doubt with legal wit,
the hand that once created it.



Radar Timeline

1935 – Sir Robert Alexander Watson-Watt develop the first radar systems in Great Britain to help detect German planes and U-boats

1949- Glastonbury, Connecticut sets up the first radar speed trap and issues the first radar-derived speeding ticket

1969- The first digital radar with a digital readout was produced

1969- Tuning forks promoted by the NBS for radar calibration

1972- Moving mode radar created

1975- K-band radar introduced

1977- Citizen’s band radio operators in New York figure out that they can detect police radar signals and create the first “speed trap warning system

1985- Same direction (aka, “same lane”) radar introduced

1990- Ka-band radar introduced

1990- Digital Signal Processing (DSP) introduced

1993- Radar with “Fastest” mode approved by IACP and placed on the Conforming Products List (CPL)


About Stalker Radar

Radar and vehicle technology continues to develop, and Stalker Radar is committed to always delivering the most accurate, dependable, and reliable radar products on the market. View our full line of dash-mount and handheld radar products here.

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