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Radar Repair: False Readings
Posted by: | CommentsIf you are like most law enforcement agencies, you probably have a few speed detection devices in need of a radar repair service. Maybe you have been putting-off calling a provider thinking that it may be too expensive to get your units repaired. If this is the case, I’d like to share with you a few techniques that could save you time and money. These techniques are only valid for mobile radar units with remote antennas.
The idea is to isolate the problematic part of the radar such as an antenna, cable, counter, etc. Then simply call your local radar repair company or the manufacturer and order a new part.
Obviously, the difficult part of this is to identify the failing device.
False Readings (Ghosting)
Problem: The radar is reporting erratic speeds when there is no target in range.
Action: Assuming the radar is not receiving a non-vehicle target like your heating/cooling fan or radio transmissions from a local transmitter, the problem is likely the antenna. The receiver diode has aged and has become unstable. Replace suspected antenna with a known good antenna. If the problem goes away, order a new antenna or send the antenna in to the radar repair facility to get the receiver diode replace. This way you do not have to remove all of the cables.
If this action does not solve the problem, you probably have a defective antenna cable. Place suspected antenna back in original position. Now on the rear of the counter, place the front antenna cable in the rear antenna port and rear antenna cable in the fwd antenna port. If the problem goes away, order another antenna cable.
It is very rare for this problem to be generated from within the counting unit. But if the above methods do not solve the problem simply try another counting unit to see if the issue gets resolved. If so, contact a reputable radar repair shop or the manufacturer to get the counter repaired.
This is the first of a multi-part article series I will be posting to help you diagnose your radar problems. You can read the next article here: Radar Repair: No Range
Radar Certification: What Is It And Why Is It Required?
Posted by: | CommentsBasically, a police radar certification insures the accuracy of the radar. Electronic component values commonly change their value over time due to age and other environmental factors. For radar’s, this change in component value could vary the way it calculates vehicle velocity. Radars made nowadays use better components and do not exhibit errors related to component value drift. Even so, these new components still have a little drift so an accuracy check is still needed.
A radar certification is normally performed by a third party who has no association with the law enforcement agency. Should a motorist take his speeding violation to court, it is in the proper interest of the agency to have a radar certification from an independent company. Should a speeding offense make it to court, the certification agency is commonly summoned to testify regarding the operation of the radar that was used to write the speeding citation. If called to a court hearing on the speeding ticket, the certification company can only attest to the accuracy of the radar.
The elements of a thorough radar certification or radar calibration include:
Transmitter Frequency Check
The microwave transmitter emits the high frequency towards the target vehicle. This frequency must remain in the range as specified by the manufacturer. Due to high frequencies of these transmitters, highly-sophisticated equipment must be used to measure their output.
Receiver (Antenna(s)) Check
The antennas receive the reflected microwave frequency and compare it to the emitted frequency to create a frequency-difference. To imitate this difference, a known frequency is generated and located in front of the antennas. If the right speed is shown on the display, the antennas are deemed to be accurate.
Radar Functional Check
In addition to the transmitter and receiver check, a extensive functional check should be performed. To complete the certification, the remote control and base unit functions must be checked against the operators manual. Prior to certification, the radar must be functioning per the operators manual with no malfunctions. If a repair is needed the certification company may be able to do the radar repair as well.
Local government generally requires speed detection equipment be certified on a regular schedule. Most court systems like to see a radar certification done once a year. In general, all electronic equipment used for testing should be tested for accuracy each year. This means that the equipment used to certify radar be checked for accuracy also. The National Institute for Standards and Testing (NIST) is the office to which all test equipment accuracy records should be traced. If the is the case, your radar can be deemed accurate to NIST standards.
Click Here For Details On Radar Certification Service From Precision Radar
Traffic Radar: The Basic Idea
Posted by: | CommentsTake the light from a flashlight, this is very much like the unseeable light production from a radar. That’s because microwaves act much like light waves. They move in straight lines and they are easily reflected. Objects like vehicles, signs and bridges are the most effective due to their elevated metallic content.
Unlike light, however, you can’t see the radar beam because microwaves are invisible. But they are very easily received by a radio tuned to microwave frequency. In fact, this is the idea that today’s traffic radars are based upon.
Traffic radar performance is a simple issue of pointing the antenna down the road.
When an approaching target comes into range, the radar beam reflects off the target and gets received by the radar.
How Traffic Radar Measures The Speed of Traffic
The radar reflections seen by the radar determine the speed of the target. The Doppler theory is then used to calculate the true speed of the vehicle. You may be familiar with how the Doppler effect works on sound frequencies. With sound waves, you can experience the Doppler effect at railroad tracks. A constant pitch is heard as a train approaches. You will observe a lower pitch at the second the train passes. The train itself is making the same sound both approaching and going, but a stationary listener, the velocity of the train adds to the pitch of its sound as it approaches, and subtracts as it departs. For the train illustration, the difference in pitch between the real train pitch and the pitch a stationary listener experiences is called Doppler Shift and the train’s speed determines degree of the change.
Traffic radar applies this Doppler theory to microwaves.
Specifically, the Doppler principle compares the originally transmitted frequency to the phase-shifted reflected frequency and calculates speed from this difference assuming the radar is functioning properly. However, in some instances the rader may give incorrect results causing you to seek the services of a radar repair facility.
Referring back to the flashlight/spotlight comparison, the radiated light only shines so far giving us limited sight. The more powerful it is, the further it reaches. Microwave beams are no different.
Traffic radar has relatively limited reach due to its low power consumption. As already mentioned, the farther the beams travel to get to the object the weaker they will be at impact. As an example, say an policeman triggers his radar at a target one mile away. But the reflected signal has to travel that identical mile back to the radar before it’s of any value. If the returned microwaves are too small, the radar’s receiver cannot pick-up the reflected signal to calculate speed. If this is the situation, the vehicle is out of reach.
Radar reach depends upon two things: strength of the radar and reflectivity of the object.
The measure of power is determined by the radar’s designer: to the motorist, it’s not a variable. If you think the range is not sufficient anymore you should have it checked-out by a reputable radar repair shop. But reflectivity varies with each target.
On the freeway, beam reflectivity is largely based on size and shape of the target. The smaller the vehicle, the smaller its reflection, and therefore the shorter the range. Therefore, a radar that cannot detect a small car at close range can detect a large car at a longer range.
It is a common practice to send the unit to a radar repair facility so they can perform a series of tests to guarantee accurate readings.