What is a signal jammer?

Answer 1

A signal jammer or jamming transmitter is a small, low-powered transmitter that interfers with receivers in an area around the jammer. The radius of the area will depend on the power of the jammer. The jammer signal will be "seen" by the receiver and it won't then be able to "see" the little signal of the remotely located transmitter that it is trying to "look at" before you turn on your jammer. The jammer transmits a signal (without modulation - it's just the carrier wave) that radiates from the jammer pretty much in all directions (for an omni-directional antenna - which is what is usually on them). This small signal reaches all receivers within the area of its effective range and "swamps" the receivers in that area. Understand that the transmitters reaching out to receivers are generally "high power" units (their power varying depending on what they're designed to do). The jammer is low power. But because the signal from the transmitter is (almost always) a long, long way away from the receivers in the jammer's area, the signal from the transmitter is very tiny in that area. The jammer, on the other hand, has a "large" signal in that area because it's so close to those receivers. It's the amount of signal that gets to a receiver that is important. If a tiny transmitter (a jammer) is "right on top" of a receiver, it will "hit" that receiver hard compared to the tiny signal getting to that receiver from the (high powered) transmitter many miles away. The general rule for power for a transmitter getting to a receiver is that the signal strength is going to be the inverse sqare of the distance from that transmitter. That means that if you have "x" amount of signal at a given spot from a transmitter and them double your distance from the transmitter, the signal will be 1/d2 or 1/22 or 1/4th the amount you had before. Double the distance again and you're down to 1/16th the original amount of signal. A little transmitter works well to jam a receiver if it's right on top of it. It will "blind" the receiver to the "real" signal from the transmitter it is trying to capture. Jammers are generally a no-no, both ethically and legally. Use your head here and think through your options if you are planning some "experimental" electronics. It is the FCC (the Feds) that get down on individuals who interfere with communications. They play hard ball. Imagine interrupting air-to-ground communications and interfering with air traffic. They'd lock you up and throw away the key. Seriously.

Answer 2

A wifi jammer is a device used to block wifi acess from other users in a predetirmined area. they are also expensive and quite possibly illegal