Keep radar units accurate and court acceptable.

Certification of radar units that use FCC approved radar frequencies for X, K, and KA-bands with the Vocar Pro-Tect system.

Police Radar Accuracy - Is It Guaranteed?

Traffic radar is a common tool of law enforcement in all areas of the United States. Officers
routinely dispense speeding citations based on the readings they receive from these devices, and
seldom question their accuracy - assuming that any periodic certification of each unit guarantees
it is working correctly.

Unfortunately, these assumptions may be entirely false - particularly if a radar unit’s
certification did not include a simple procedure known as a Center Frequency Test.
Consider for a moment the basic operating principle of a police radar unit. The unit projects a
frequency beam, which strikes a moving object and bounces back. A physical effect known as
Doppler Shift causes the return signal to be a slightly different frequency than the original signal.
The difference is proportional to the speed of the moving object, allowing the radar unit to
determine the speed of the object with various mathematical methods.

The math used in the computation relies upon the fact that the outgoing signal is a known, preset
frequency. Now, consider what happens to the equation if this “known” value is in fact different
than what the radar unit is expecting it to be. Obviously, the result of the calculation will not be
correct, and the unit will display an inaccurate speed.

Performing a Center Frequency Test is the only way to guarantee that a radar unit is
displaying correct speed results as supported by the radar manufacturers and the International
Association of Chiefs of Police (IACP). So why do so many certifications not include this critical
test?

Some may argue that modern technology eliminates the possibility of inaccurate frequencies, but
this is simply not true. Two parts of a radar unit determine its output frequency; a microwave
diode, and the size and shape of the cavity in which the diode is placed. Like any electronic
component, a small percentage of these diodes will drift due to aging and long-term exposure to
temperature extremes. And, like any other container, a small percentage of antenna bodies will
leak - which means they can become contaminated with dirt and moisture, and it takes only a
small amount of either to change the characteristics. Some cavities even have a tuning screw that
can be moved to adjust the frequency.

It is also a fact that many radar units simply do not receive the proper care or attention during
normal use. And checking the speed-reading ability of a radar unit with a Tuning Fork or an audio
tone is not enough - those tests only confirm that the unit can measure the Doppler Shift itself,
which is meaningless if the output frequency it bases its speed calculations on is incorrect in the
first place.

So how does a police agency guarantee that the transmitting frequency of a radar unit, upon
which all speed readings are based, is in fact accurate? Simple: perform a Center Frequency
Test as part of a periodic, comprehensive certification process, and document the results.
And if they don’t? Then they should be prepared to have citations overturned in court - because
without the results of a Center Frequency Test, the accuracy of the unit will always be suspect.

Contact us today to get started. Use our contact form or call 330.495.9115.

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Hall Public Safety Co. • 13940 Gopp Ave. • Hartville, Ohio 44632
phone: 330.495.9115 fax: 330.877.8574