Technical data on the Multanova 6F - Ka band (Australia):
If you radar detector is able to pick up the Multanova Speed Camera, its doing pretty well considering that the main radiation jet is angled at 22 degrees to the road direction. Also the fact that it only emits 0.5 mwatts. You would probably get more radiation standing close to your microwave oven. It is interesting to note the ambient radiation that emanates from the device in all other directions.
Radiation plate 6F Multanova Speed Camera
This is the radiation pattern around the speed camera. The central protrusion in the graph is the microwave jet.
So an accurately calibrated "off the shelf" Multanova speed camera is at best accurate to plus or minus 3 km/h below 100km/h. That makes a mockery of the Western Australian Police 1km/h tolerance factor, doesn't it.
Further down in this article you will learn of the "Cosine Effect". This can vary the reading by as much as 4km/h at 60km/h.
The basic method of radar speed measurement is:
- Radar device sends out radio signal
- Signal strikes a solid object, e.g. an automobile, and is reflected (bounced) back towards the radar receiver.
- If there is a relative motion between the object and the radar transmitter, the reflected signal will be different from the transmitted signal in frequency
- The amount of difference (frequency or Doppler shift) indicates the speed of the relative motion
- On the X-band, for every 1 mph difference in speed there is a 31.4Hz difference in frequency
On the K band, for every 1 mph difference in speed there is a 72.0Hz difference in frequency .
Radar is usually known by letter-band nomenclature, e.g., k-band. speed camera radar is unlike traditional hand-held radar in two important respects, all of which increase its accuracy and make it almost impossible for violators to detect the beam before their violation has been registered. These differences are its low output, which at maximum strength is only twenty-five milliwatts, and its cross-the-road beam, rather than the traditional hand-held down-the-road beam.
The accuracy of the unit is greatly enhanced by these two differences, the low output and the beam direction. The speed camera radar unit beam cuts across the road, and can thus detect the vehicle exceeding the set speed limit at a closer range to the patrol vehicle. Furthermore, with a maximum output of only twenty-five milliwatts, the farthest an object's velocity has been measured is across 5 lanes of highway. These two differences also result in making the radar beam almost impossible for radar detectors to identify until they have already been recorded by the unit.
Speed camera radar systems usually operate on the K-band at 24.15 GHz. In Western Australia they operate on the Ka-band which is at a higher frequency. This is important because this is designated by the FCC as one of only two bandwidths permanently assigned for use by police radar.
As a car passes through the beam emitted by the radar antenna, the radar antenna makes a series of measurements of the vehicle's speed. Upon identification of a speeder from these measurements a signal is sent to the central processing unit, which in turn directs the high speed camera to take a photograph of the violator.
Certification of Speed Cameras
Radar units by their nature are sophisticated instrumentation. As such great care is given to the accuracy of various products prior to being put into public use. This is usually by a method called type certification. Several agencies throughout the world specify the requirements for and actually test radar units prior to allowing the sale. The Organization Internationale de Mï'trologie Lïgale (OIML), the Nederlands Meetinstituut (NMI) and the British Home Office are three such organizations.
In Western Australia, the police prefer to use a single camera that takes photographs of the front of the speeding. This has the advantage of identiying the driver at the same time.
Speed cameras in other states of Australia, are setup to take photographs of the rear of the offending vehicles or is some cases, like Victoria both front and back at the same time. This has the advantage of identifying motorbike licence plates that are currently not obtainable with the Western Australian system setup.
In other countries speed cameras are setup to take photographs of the front and or, the rear of a speeding vehicle.
Upon on determining that a violator has been identified, the unit's internal computer calculates the timing delay for the second camera, based on the speed of the offending vehicle, the length of the patrol car, and the angle of the cameras. The second camera, which is aimed out the front window of the photo-radar vehicle, then takes a photograph. This second image captures the rear of the offending vehicle as it drives away from the unit. This photograph is used to identify the vehicle when no front plate is visible on the first photograph. As with the first photograph, this second violation photograph contains encrypted data pertaining to the time, date and speed of the violation.
Cameras used in photo-radar are usually high-speed, industrial cameras. Unlike other cameras, Photo radar speed cameras are designed for traffic enforcement photography. A high speed flash system is integrated into the photographic unit, allowing for enforcement on a 24-hour basis. The flash unit is usually synchronized at 1/1000 of a second, and is used for both day and night deployments. The flash bulb is sealed within a water-resistant housing, and is located on the outside of the unit. The high-speed of the camera flash allows for the units safe operation during both day and night deployments.
Radar Emission and Detection
Fundamental to the operation of a speed camera system is the emission of a microwave beam and the detection of the reflected signal.
As a car passes through the beam emitted by the radar antenna, the unit additionally undergoes a self-test to verify its accuracy. If it is not operating properly, then the unit automatically enters standby mode. If the self-check is successfully completed, the radar antenna takes a series of measurements of the vehicle's speed. These figures are then averaged, and if any deviates from the mean by more than 2% the photograph is not taken. Always giving the driver the benefit of the doubt, the radar antenna takes additional measurements of the speeding car passing through its beam. These measurements are then compared to the average speed calculated from the first set of measurements. If any of these deviate, then the vehicle is not photographed.
The system may also come equipped with an internal or external Tuning Fork which is used to independently check the vibration at the beginning and end of each deployment. Since standard tuning forks do not create a histogram similar to that created by a vehicle, software capable of distinguishing between actual and simulated vehicle Doppler radar readings must often be employed. This error prevention algorithm must be designed to prevent common mis-reads created by objects found in the urban environment, such as the vibration of electrical substations.
Radar Beam Angle, Width, and Power
Radar antennas emit beams at specific angles and specific power levels depending on the vendor. Using an appropriate angle and low power ensure that radar detectors are incapable of detecting the speed camera until they are in the beam and an accurate speed measurement has already been determined. A 5 degree beam width and an antenna measuring angle of 20 degrees are typical and allows for accurate speed measurements of vehicles on roadways from 1 to 5 lanes in width.
Since it is impractical to place a photo-radar unit in same vector as the vehicle being measured, a correction must be made to account for any displacement. A normal deployment frequently set the radar at a 20 degrees angle relative to the direction of travel. The technique for calculating the correction is called the cosine effect.
The cosine effect is used to determine the actual speed of a vehicle given the indicated speed and the angle of the beam.
This relationship is expressed as: True Speed = Indicated Speed/Cosine q
A Power Source
The radar antenna and radar control unit (CU) are usually powered by an independent battery pack, which contains a minimum of two 26Ah 12V DC sealed lead acid marine type batteries capable of supplying all required power for a full day's operation, and a 240V AC recharging system. The radar antenna and CU can not be operated while the 240V AC recharging system is supplying the battery. This technique complies with all case law requirements regarding a separate power supply for the radar antenna and RDU. These components should not be connected in any way to the vehicle's battery power.
The Camera Unit
The cameras used in photo-radar systems are high speed industrial cameras. Cameras used in photo-radar system are specifically designed for traffic enforcement photography. The front facing camera's usual 90 mm lens is designed for capturing the characters on rear license plates. This is of great importance because the lens is the critical ingredient in the quality of the photograph. Picture quality is a function of camera type - digital vs wet film. If wet film is used, lens length and quality, negative size, film type and processing will impact the image quality.
Illumination - Speed Camera Flash Units
A flash tube and optimized lamp reflector is usually required to properly illuminate a vehicle. It must be capable of providing adequate illumination under all light and weather conditions, including:
- Up to four lanes in one direction
- Varying levels of ambient light conditions from full sunlight to no external light source
The flash system must also be safe for passing motorists. Many citizens are concerned about frontal flash and may claim that it is unsafe to expose a driver to such a bright light. In reality the flash is intense but of very short duration. It is much less distracting than lightning and there are no cases of recorded accidents resulting from flash units used in photo enforcement. In some cases as in Western Australia, red filters are used over the flash units to reduce the affect but these are most frequently used with black and white film since they produce poor color images.
Flash intensity is as critical with photo-radar as it is with other forms of photo enforcement. The lower position of the flash as well as the relative close proximity of the vehicle being photographed aids in obtaining quality photographs. Lighting the interior of a vehicle for purposes of driver identification for those jurisdictions requiring it is equally a problem, however. Cameras are usually pre-adjusted to provide optimum light under the widest range of conditions. However, in the event that an adjustment is required, flash settings can usually be selected on site.
Photograph Rate and Volume
Cameras able to take in excess of two photographs per second are usually used in photo-radar systems. Such cameras are also able to take many thousands of photographs before needing servicing. These cameras far exceed the durability specifications for standard professional 35MM cameras usually seen by professional photographers. Such reliability is very important for high-volume purposes such as traffic photography.
Speed cameras are usually completely automated. This includes automatic camera activation controlled by the radar antenna. The cameras are manually or automatically leveled and pre-aligned with the radar antenna. The film can easily be loaded and unloaded, and any length of film from a standard 36 frame roll to a professional 100 ft. (800 frames) roll can usually be used with the cameras.
"Make your licence plate invisible to photo speed cameras."