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how does a radio wave carry sound?

a) how does a carrier wave work?

b) signal strength

Radio waves are electromagnetic radiation. It is called radiation only because it doesn't require a medium in which to travel. A changing electric field generates a changing magnetic field which generates a changing electric field which generates a changing magnetic field which generates.....you get the picture. All this propagation travels approximately 186,000 miles/sec or 300 million meters/sec. This is the speed regardless of how fast the fields change.

The electric or magnetic field goes through a positive and negative change. This is called a cycle. The number of cycles per second the field goes through is called frequency measured in Hertz. The wavelength of the radio signal is inversely proportional to the frequency. Picture a 1 MHz radio signal traveling for one second. Chop up that 300 million meter long signal into 1 million parts. Each part would be a cycle 300 meters long.

wavelength (in meters) = 300 / frequency (in MHz)

So every frequency has a different wavelength and visa versa.

Information is placed on a radio signal in two basic ways; amplitude modulation (AM) and frequency modulation (FM). Both modulate a single radio signal at a certain frequency, called a carrier. AM superimposes a voice signal onto the carrier. The amplitude of the radio frequency (RF) signal at any moment in time is the same as the signal coming from the microphone. With FM, the amplitude changes are converted into frequency changes and that is superimposed onto the carrier instead.

On the receiving end, a combination of electronic coils and capacitors conduct differently to different carrier frequencies. These are tuned to pass a signal of the right frequency. The signal is then demodulated and the original voice signal recovered.

This is all an over-simplification of how radio works, but it's close. Signals through wires are similar but you are only dealing with movements of electrons vs RF and changing electromagnetic waves. when those moving electrons go into an antenna, they create a changing magnetic field which creates a changing electric.......

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AM 과 FM 이 있죠.

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