A radar speed trap is sending out radar waves all the time. Every vehicle approaching the radar trap or moving away from it is reflecting these waves.
Because of the doppler effect the reflected waves are either upset or stretched, depending of the direction and speed of the car. The radar trap sensors the reflected waves and compares them to the original outgoing waves.
By looking at how strong the reflected waves were upset or stretched in comparison to the original signal, the speed can be calculated.
Since the waves are being sent out all the time, a high quality radar antenna in your vehicle can detect the radar signal already hundreds of meters away from the trap. You get a warning, reduce your speed and get no ticket.
Important to understand: radar speed traps can be detected, but not disturbed.
A laser speed trap works with reflection, too. But with some differences. For example, you're approaching some police officers next to the road, pointing a laser gun in your direction. After selecting your car and deciding to do
a measurement of your speed, the officer aims at your vehicle and pulls the trigger. Your car reflects the guns laser pulses, the gun sensors the reflection and calculates your speed by the difference in running time of multiple
pulses and reflections one after another.
The whole measurement takes just about half a second so you have no chance to hit the brakes in time. Laser jammers send out their own laser pulses as soon as a measurement of your car is detected. The police laser is unable to see a difference in the reflection of it's own pulses and the pulses your laser jammer sends out, so a calculation of your speed can not be done. Continue...
Important to understand: radar speed traps can be detected, but not disturbed. (Well, sure you can detect them but then it's already too late.)
This type of device is by far the cheapest way of getting some protection against speed traps. The installation ist quick and easy, you can do it yourself. The system is simple fixed to the windshield or dashboard with suction cups.
Power is supplied trough the standard 12 volt cigarette lighter.
Radar detection: Depending on the device more or less reliable, but usually pretty good. The warning distance is still quite a bit shorter than with fixed installations.
Laser protection: None. Even tough some manufacturers claim to offer laser protection as well, this ist just impossible. Explained in Detail...
Price: ca. 200 - 600 Euro
Installation price: none
A fixed installation radar detector increases your protection against speeding tickets drastically. The radar detection antenna is mounted in the front bumper, not in the inside of your car as it would be with a portable device.
Radar detection: Very reliable, but depending on device, software and quality of installation.
Laser protection: None, only in combination with laser jammers.
Price: ca. 600 - 1900 Euro (without laser jammers)
Installation price: depending on the quality ca. 200 - 500 Euro
Effective protection against police lasers is only possible by using fixed installation laser jammers. This is why. With high quality laser jammers correctly installed in your car, you're safe in ca. 95% of all cases.
The remaining 5% are actually not the system's fault, but caused by external factors like other cars blocking your sensor for example. Usually you need 2 jammer units to protect the front of a car.
Radar detection: None, only in combination with a radar detector
Laser protection: Reliable, but the quality of protection depends of the quality of the device and installation
Price: ca. 400 - 900 Euro
Installation price: depending on the quality ca. 200-500 Euro, combined with a fixed radar detector installation the price reduces drastically