Theory of the basic operation
Car Simulation Using Matlab
A police gun radar and how it works
Angle dependencies of speed detection
Method of Active Noise Jamming
Active, Continuous Noise Jamming:
- Always works except sometimes at VERY close range
- Very easy to build and operate, since it is always on
- Very Illegal: Jamming or attempting to jam a police radar gun is a federal felony punishable by fines up to $75,000 and one year in jail.
- Very easy to detect, since you are broadcasting a loud signal to everyone around. Most modern radar guns have detectors for these signals, alerting the cop when he is being jammed in this manner.
- Radar detectors will not work, since your own jammer is constantly broadcasting radar anyhow.
- The cops can shoot an anti-speeder missile which homes in on your jamming signal.
Active, Selective Noise Jamming:
- Works most of the time.
- Less likely to be detected by jammer detectors, since it is on for a shorter period of time, and since it will be on only when the cop’s radar gun is transmitting. Many radar guns’ jammer detectors do not work when the gun is transmitting, because it reads the radar being transmitted by the gun itself.
- The anti-speeder missile described above will not work.
- Just as illegal as continuous active jammers, with the same penalties
- If the radar gun is well built and faster than the jammer device, it can get a reading of a car’s speed before the jammer turns on
- Some more modern DSP radar guns can detect radar jamming even when the gun is transmitting
Method of Active Deceptive Jamming
Active, Deception Jamming:
- It is not detected by the radar gun as jamming.
- Works very well if one knows the frequency which the cops are using (which is a given for the X and K bands). Radar detectors operating in the Ka band can use any number of different frequencies. Some deception jammers are actually sophisticated enough to read a (fixed) Ka frequency and then transmit the appropriate jamming frequency; however, due to constant FCC crackdowns on jammer manufacturers, these are very difficult to find.
- Still just as illegal as all active jammers, with the same penalties
- Once again, if the radar gun is well built and faster than the jammer device, it can get a reading of a car’s speed before the jammer turns on.
- Many modern day Ka band radar guns switch rapidly between many different frequencies, foiling all deception jammers since they cannot determine which frequency to transmit
Method of Passive Jamming
- Legal in most states.
- Certain states (including California, Utah, Minnesota, Ohio, Indiana and Oklahoma) have laws prohibiting any jamming device
- The large antennas required to absorb the incident radar beams can actually increase your car’s visibility to radar detectors, allowing them to get a reading from a larger distance than otherwise possible.
- For this method to work the jammer (distorted signal) power must be as large as or greater than target reflected power -- the jammer antenna would need to capture well over half of all the radar energy striking the target (a very large jammer antenna), and be aligned to the radar antenna. To date all known passive jammers have had no effect on any radar under any circumstances.