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The actual process involved in determining a vehicle`s speed is basically a simple one. It involves directing a beam of microwave energy at an approaching or receding target vehicle. A portion of this beam is reflected by the target and is received by the Radar Unit that originally transmitted the signal. The reflected signal is shifted in frequency by an amount proportional to the speed of the target vehicle. This phenomenon is known as the Doppler Effect. The Radar Unit determines the target vehicle speed from the difference in the frequency between the reflected signal and the original signal.
Heated windscreens currently available as an option on some Ford (Instaclear) or GM (Electriclear) vehicles act as an impenetrable barrier to radar signals. You should therefore consider this when mounting the detector.
Currently there are three microwave frequencies that have been allocated and are used for traffic radar in Europe. They are:
Both X and K bands are well known to drivers who have travelled with Radar Detectors. Introduced first was X band radar which became common during the 1960's. In the mid 1970's the lower powered, more difficult to detect K band radar followed. In the 1980's a third frequency, Ka band, was introduced in Europe and in particular Germany where radar photographic traps were pioneered. This type of radar has recently been approved for use in the U.K. and its widespread use throughout Europe is to be expected.
X, K and Ka band signals can be transmitted in a number of ways. They include:
This designation refers to Radar systems that transmit a continuous, uninterrupted signal. These systems are commonly found in both fixed and mobile installations and are designed to transmit either X.K or Ka band signals.
This type of radar is more difficult to detect than continuous wave transmission because it is 'off' or on standby until activated to measure the speed of a target vehicle. 'Instant On' is found in mobile gun applications.
All radar is limited in range to line of sight. A radar gun operator must be able to see the target vehicle if he is to be able to identify it. However the range of the radar itself may well be far greater than the operator can see. A detector however can pick up and identify very small particles of this radar scatter and therefore can detect a radar source before the operator can see the target. In addition most of the radar beam directed at a target vehicle will pass around the target and continue travelling away from the source. It can be reflected by most solid objects and will therefore continue to 'bounce' down the road until eventually it exhausts itself and is too weak to detect. However a sensitive detector such as a Snooper can still receive very weak signals and accurately determine the source often at distances in excess of 2 to 3 miles. This is the reason a Snooper can detect all types of gun radar - even 'Instant On' or Pulsed Radar.
Range on gun radar is determined by a number of factors including the position of the gun, its power and to an extent how it's is being used, i.e. front or rear detection. However camera devices such as Gatso present an entirely different set of problems. They tend to operate "across" rather than "down" the road which in turn means the signal or scatter disappears very quickly. In addition the signal itself is very low powered in order that it can determine the speed of just one vehicle at a time. Cameras can operate on K or Ka band which presents a further problem in detection. Detectors have traditionally been manufactured with a single mixer tuned to X band and merely used harmonics of that mixer to pick up K and Ka bands. Although sensitive enough for establishing the presence of radar guns, harmonics on K and Ka bands provide very little if any realistic range on cameras. Independent tests on a number of detectors provided startling statistics with distances as low as 50 feet being recorded.
The answer to the problem lies in the ability to provide a mixer for each of the three bands. All Snoopers provide just such a patented system enabling the range on K and Ka band cameras to be extended to over a third of a mile, a significant advantage over all others detectors.
In certain countries a new radar based system has been added to the armoury. The 'Super Wideband' Gun. This new device has been designed to foil radar detectors by changing the frequency on which it operates. Traditionally radar systems operated on fixed frequencies within the band. However these new devices can be tuned anywhere between 33.4GHz and 36.0GHz on the Ka band. To detect its presence therefore a detector must be capable of 'sweeping' the full 2.6GHz spectrum on a very regular basis. Snooper Super Wideband Ka models can effectively monitor the entire Ka band by sweeping it six times every second ensuring that it will be detected in good time, whatever frequency the gun has been set to.
Recently, authority has been given for the use of 'Laser Guns' as a method of determining a vehicle`s speed. A laser gun projects a short pulse of invisible, intense, infrared laser light (as opposed to radar microwaves) at a specific vehicle. In order to measure the speed of the vehicle the gun uses the known speed of light to determine the range of the target by timing the flight if the pulse from the gun to the vehicle and back. By taking a series of ranges over a known time, normally just a few nanoseconds, and comparing the distance the target has travelled between the pulses, the speed of the vehicle can be determined. Although the laser beam is relatively narrow in comparison with radar beams it can still scatter due to atmospheric conditions and reflections.
Snooper laser detection technology is lifted directly from military applications and as a result the detectors can monitor a laser gun at up to 10 times the gun`s effective range. In addition they are sensitive enough to be able to detect 'off-axis energy' or scatter of the main beam.
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