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I have read the definition about the term "Hertz" at the address: http://compnetworking.about.com/od/wirelessfaqs/g/ghz.htm

But I am not quite sure I got through that.

Can anyone have other explanations, any picture would be highly appreciated?

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My question deserves vote downs??superuser is not a place for such beginner questions? You guys are IT guru, so you can easily understand the definition at the link I've given. But I am not. I did not understand. If you could not give me an answer or find this question ridiculous, why didn't you just leave this question? –  gonnabe May 13 '12 at 12:47
    
It's not ridiculous. This question simply does not show research effort. You read the article, okay, but what exactly didn't you understand about it? Apart from that, what computer problem are you trying to solve? This is barely related to computer hardware (and software) and there's a plethora of resources covering what a "Hertz" is already. Users are encouraged to vote on questions, so please don't take a downvote personally. –  slhck May 13 '12 at 15:03

3 Answers 3

up vote 1 down vote accepted

Hertz (abbreviated Hz) is a unit of measure of the frequency of an oscillating phenomenon such as an electromagnetic wave, the electricity that powers your home or a guitar string. It means the same as cycles per second, which was the term used until some time in the 1950s or 1960s.

Consider a pendulum or a swing. If you move it away from its rest position and let go, it will swing toward that rest position, move through it to some distance on the other side, then stop, reverse direction, and come back almost to the point where you released it. That is one cycle. If that cycle took 2 seconds, its frequency would be 0.5 cycles per second or 0.5 Hz. A guitar string oscillates much faster than that. A string sounding A above middle C, for example, is oscillating at 440 Hz. In the case of radio waves, the thing that is oscillating is an electromagnetic field, and the oscillation frequencies are higher, from Very Low Frequencies of 3 kHz to 30 kHz through about 300 GHz (3 x 1011 Hz).

Radio waves interact with their environment and behave differently at different frequencies because the nature of the interactions change with frequency. For example, Very Low Frequecy and Low Frequency waves (3 kHz to 300 kHz) are able to penetrate ocean water so they can be used to communicate with submarines. High Frequency waves (3 MHz to 30 MHz) are reflected by the ionosphere so they can be used for communications around the world. Microwaves (300 MHz to 300 GHz) interact strongly with water and other molecules and can be used to heat food.

A more complete listing of radio frequencies and their applications can be found here.

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Very simply, Hertz is a measure of frequency, and in the case of wireless, refers to the frequency of the electromagnetic waves used for communication. In a very simple sense, its a little like hearing - humans have a range between 20 Hz and 20KHz in terms of audio, and we can't hear anything above or below that. In this case your equipment talks to each other at 2.4 GHz or 5 GHz. The antenna and other gear need to be tuned to that frequency, and can't hear anything outside the frequency they are set to.

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Hertz is the unit used to measure frequency. In wireless communications, it means the radio signal frequencies used to transmit/receive data by wireless equipment (routers, mobile phones etc...).

Equipment is designed to use a certain range of frequencies in the radio spectrum; those frequencies are allocated by international bodies, which define standards on how data is transmitted over them.

Most communication is done on the ISM (Industrial, Scientific & Medical) band which is exempt from the regulations that exist for other bands. Also, the high frequencies used allow for the usage of smaller, lighter antennas.

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