Skip to content Skip to navigation

Connexions

You are here: Home » Content » Method of Active Noise Jamming

Navigation

Content Actions
  • Download module PDF
  • Add to ...
    Add the module to:
    • My Favorites
    • A lens
    • An external social bookmarking service
    • My Favorites (What is 'My Favorites'?)
      'My Favorites' is a special kind of lens which you can use to bookmark modules and collections directly in Connexions. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need a Connexions account to use 'My Favorites'.
    • A lens (What is a lens?)

      Definition of a lens

      Lenses

      A lens is a custom view of Connexions content. You can think of it as a fancy kind of list that will let you see Connexions through the eyes of organizations and people you trust.

      What is in a lens?

      Lens makers point to Connexions materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

      Who can create a lens?

      Any individual Connexions member, a community, or a respected organization.

      What are tags? tag icon

      Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

    • External bookmarks
  • E-mail the author
  • Rate this module (How does the rating system work?)

    Rating system

    Ratings

    Ratings allow you to judge the quality of modules. If other users have ranked the module then its average rating is displayed below. Ratings are calculated on a scale from one star (Poor) to five stars (Excellent).

    How to rate a module

    Hover over the star that corresponds to the rating you wish to assign. Click on the star to add your rating. Your rating should be based on the quality of the content. You must have an account and be logged in to rate content.

    		(0 ratings)

Lenses

What is a lens?

Definition of a lens

Lenses

A lens is a custom view of Connexions content. You can think of it as a fancy kind of list that will let you see Connexions through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to Connexions materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual Connexions member, a community, or a respected organization.

What are tags? tag icon

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

This content is ...

Affiliated with (What does "Affiliated with" mean?)

This content is either by members of the organizations listed or about topics related to the organizations listed. Click each link to see a list of all content affiliated with the organization.
  • Rice University ELEC 301 Projects

    This module is included inLens: Rice University ELEC 301 Project Lens
    By: Rice University ELEC 301As a part of collection:"ELEC 301 Projects Fall 2004"

    Click the "Rice University ELEC 301 Projects" link to see all content affiliated with them.

Recently Viewed

This feature requires Javascript to be enabled.

Method of Active Noise Jamming

Module by: Lynn Le

Summary: This module describes the method of Active Noise Jamming and what happens when it is detected by a radar.

There are several different methods of jamming available, all with their own strengths and weaknesses. One of these is active noise jamming explained below.

Active, Continuous Noise Jamming:

Continuously broadcasts white noise of high amplitude, causing radar guns to read random numbers, preventing a reading of the actual speed of the car. The radar gun takes about 8 measurements of speed, and only outputs a speed if the 8 measurements agree.

Advantages

  • Always works except sometimes at VERY close range
  • Very easy to build and operate, since it is always on

Disadvantages

  • 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:

This is a variation on how the Active Noise Jammer is used. This is not continually on, as the implementation above is. Instead, a radar detector detects radar, and then triggers the active jammer described above for several seconds while the driver slows down to a legal speed. The jammer then shuts off.

Note: this requires that the jammer operate faster than the radar gun, so that the jamming signal is outputted before the reading is complete.

Advantages

  • 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.

Disadvantages

  • 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

Example

Both jammers above work the same but differ in when and how long they are broadcast. Now we output tons of noise at all frequencies, filling the spectrum up like this:

Figure 1
Figure 1 (continuousjam.gif)
As is easily seen, the true peaks are completely lost in a noisy haze. This causes the radar gun’s matched filter to look something like this:
Figure 2
Figure 2 (continuousresult.gif)
Thus, the radar gun outputs go crazy, and no believable result is found. Since a radar gun requires 8 subsequent readings to all output the same velocity before making a measurement, this prevents the guns from making any measurement whatsoever.

Comments, questions, feedback, criticisms?

Send feedback