Radio Frequency and electrical signals

[hasan_researc]

"Radio frequency (RF) is a rate of oscillation in the range of about 30 kHz to 300 GHz, which corresponds to the frequency of electrical signals normally used to produce and detect radio waves." - Quoted from Wikipedia.

How can electrical signals be used to produce and detect radio waves?
What do we need RF for those purposes?
What is a signal anyway?

Thanks in advance for any help!

 

[fss]

How can electrical signals be used to produce and detect radio waves?

http://en.wikipedia.org/wiki/Alternating_current
http://en.wikipedia.org/wiki/Antenna_(radio)

What do we need RF for those purposes?

Err... why do we need RF? RF comes in handy in a lot of situations. Radio, microwaves, satellite communications, ...

What is a signal anyway?

http://en.wikipedia.org/wiki/Signal

You are asking very broad questions, so I'm giving you broad answers.

 

[sparkey]

http://en.wikipedia.org/wiki/Radio_frequency

maybe?

 

[sophiecentaur]

"Radio frequency (RF) is a rate of oscillation in the range of about 30 kHz to 300 GHz, which corresponds to the frequency of electrical signals normally used to produce and detect radio waves." - Quoted from Wikipedia.

How can electrical signals be used to produce and detect radio waves?
What do we need RF for those purposes?
What is a signal anyway?

Thanks in advance for any help!

You don't specify where, in Wikipedia, that quote came from but it is a very loose and confusing statement. Possibly the context would make it better(?).

Electrical signals are not, in face, any different from electromagnetic waves in space. An electrical oscillation (even 50Hz AC) is transmitted along a wire in what is, in fact, a 'guided' electromagnetic wave of very long wavelength. So a transmitter (or receiver, etc. ) is only a device for interfacing between a signal within an electronic circuit (guided waves) and space (free waves), via some form of amplifier / antenna.

A signal, "by the way", is just information (in the most general terms). You can carry information (a signal - the original meaning), written on a paper, via sound / speech or using the variations of an electric current - such as what comes from a microphone. There are many forms of information transmission and, nowadays, the vast majority of information (in terms of sheer quantity) is transferred as electrical signals on wires, radio waves or optically, along fibres.

The reason that RF frequencies are used is that em waves at these frequencies can be launched and retrieved using antennae and generated / processed / detected by available electronic equipment technologies. These days, light is also used, of course.