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hi i want to know  how i connect two or more office located at different places with radio or wireless communication.

Hello Amalngg,

Wifi was specifically designed for this application.   You want to look at 802.11A devices between buildings.  This protocal operates at 5.8GHz and is very line of sight...so you will not get a lot of interference as long as you use a directional antenna.

For access to the wireless network within your building you want to use 802.11G or N devices to get the maximum bandwidth and user access.

I hope this helps.

Chris Pinter

Sir,

     I have an issue deciding the value of speed while calculating the wavelength of a signal. The formula I am using is lambda = c/f where 'f' is the frequency and 'c' is the speed. The issue is, while calculating the wavelength of a signal with frequency, say, 10KHz, what should be the value of speed that I should consider? So far I have read in many books and also on the internet that the speed I should consider is the speed of light which I find as wierd because the speed of signals in the frequency range 20Hz to 20KHz is about 340 m/s in air since these are sound waves. So considering the speed of light for finding the wavelength of a much slower signal is something I dont understand.

It depends on your detector.

10KHz is just about the lowest frequency anyone ever calls "radio frequency." (Yes, some Navys use far lower frequencies, even in the single digits, for underwater, around the world, submarine communications, but that is rather, um, "special."

But 10KHz is also within the range of human hearing. That begs the question...

What method are you using to create and detect these frequencies? If you create it with an audio transducer ("a speaker" (a fairly small one)), then you are creating a mechanical wave ("a sound wave" in this case) which will travel at roughly 340 m/s in air (dependent on temperature, etc.) and you will detect it with something like a microphone. On the other hand, if you are creating your wave with an antenna then you will be creating a electromagnetic wave which will travel at 3x10^8 m/s and you will receive it with another antenna (another very long one).

The general equation relating speed of a wave and wavelength is lambda = v / f. This is altered slightly into the form you provided, lambda = c / f for the special case of electromagnetic radiation (radio waves, microwaves, light, x-rays, gamma rays). In this case c (speed of light = 3x10^8 m/s) replaces the more general "v." But when dealing with mechanical waves, for example, sound, you set v equal to the speed of sound in the medium being analyzed. Note that speed of sound in air and water are much different.

It depends on your detector.

10KHz is just about the lowest frequency anyone ever calls "radio frequency." (Yes, some Navys use far lower frequencies, even in the single digits, for underwater, around the world, submarine communications, but that is rather, um, "special."

But 10KHz is also within the range of human hearing. That begs the question...

What method are you using to create and detect these frequencies? If you create it with an audio transducer ("a speaker" (a fairly small one)), then you are creating a mechanical wave ("a sound wave" in this case) which will travel at roughly 340 m/s in air (dependent on temperature, etc.) and you will detect it with something like a microphone. On the other hand, if you are creating your wave with an antenna then you will be creating a electromagnetic wave which will travel at 3x10^8 m/s and you will receive it with another antenna (another very long one).

The general equation relating speed of a wave and wavelength is lambda = v / f. This is altered slightly into the form you provided, lambda = c / f for the special case of electromagnetic radiation (radio waves, microwaves, light, x-rays, gamma rays). In this case c (speed of light = 3x10^8 m/s) replaces the more general "v." But when dealing with mechanical waves, for example, sound, you set v equal to the speed of sound in the medium being analyzed. Note that speed of sound in air and water are much different.