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Speedometer use for Doppler Radar Testing

Speedometer use for Doppler Radar Testing

Change and innovation are cornerstones of today’s law enforcement environment, and one area experiencing new adaptation is speed enforcement. At the encouragement of Stalker Radar, an alternative method of verifying the accuracy of Doppler radar units has gained attention: using a certified patrol car speedometer as an external reference in place of traditional certified tuning forks.

A patrol vehicle’s speedometer, when used as a reference signal for radar comparison, must be periodically certified, just as tuning forks are. Although a speedometer is generally accurate when the vehicle is new, it can drift out of calibration for a variety of reasons. As a result, courts increasingly require documented proof that a speedometer remains accurate if it is used as the external reference for radar verification.

Traditionally, Doppler radar accuracy is verified using tuning forks of known speeds. The forks are activated and positioned so the radar antenna receives the externally generated signal and processes it internally, producing a displayed speed that should match the tuning fork’s certified value. This process relies on an external, known reference signal to confirm that the radar correctly processes and displays the expected speed.

Because all traffic monitored by a radar device originates externally, the reference signal used for verification must also come from an external source. That source may be a tuning fork or a speedometer—provided that either device is periodically tested and verified for accuracy according to accepted traceability and calibration standards.

Under normal practice, tuning forks are certified annually and used daily to verify radar accuracy. A speedometer used as the reference signal must follow a similar certification schedule to ensure its reliability and legal defensibility.

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1601 S. Grove, Wichita, KS 67211

Phone 1-800-337-7291 FAX 1-316-263-5302

www.radarservice.com

WAS YOUR ANTENNA FREQUENCY CHECKED DURING YOUR LAST CERTIFICAITON?

MOST AREN’T !

AI assisted legal analysis is teaching attorneys that the most straight forward challenge to radar evidence today is a certification that lacks a documented, measured antenna frequency.

This critical omission is now one of the most frequently cited grounds for challenging radar evidence. Studies show frequency measurement is skipped in the majority of field calibration checks due to the certification company’s lack of proper equipment – leaving departments exposed!

If you see any of the following exact numbers on your certification certificate this is simply the manufacturer’s “label frequency” on the side of your antenna such as:

K Band 24.15 GHz
MPH Radar Ka Band 33.8 GHz
Stalker Ka Band 34.7 GHz
Kustom and Decatur Ka Band 35.5 GHz

This indicates that the antenna frequency was not actually measured during that certification.

Three ruling authorities require traceable frequency verification for a valid Doppler radar certification –

FCC – Radar units must operate within licensed band limits; frequency drift is a primary violation.
NIST – Speed measuring devices require calibration to the National standards; frequency is the root measurement.
IACP – Recommends annual frequency verification to keep evidence admissible.

Why?

Because of Drift and Aging. Temperature and Aging shift oscillator frequency – only regular frequency verification catches drift.

Frequency meters are expensive—and we use them. You can watch your radar’s frequency measurement in real time as our technician checks it directly from your unit. This is one of the reasons legitimate certifications cost more.
We do it right – Because it’s your reputation on the line.

Speedometer use for Doppler Radar Testing