Whether you are listening to the radio, watching television, cooking dinner in a microwave or having an x-ray taken, you are dealing with electromagnetic waves. AM and FM waves are among the lower frequencies of electromagnetic waves, while x-rays and gamma rays rank among the highest.

AM Waves

AM (Amplitude Modification) radio waves are among the lowest frequencies of electromagnetic waves transmitted. They can be imagined in terms an undulating line with peaks and troughs. A lower frequency of electromagnetic wave has a much greater distance between its peaks and troughs. When traveling through the air, an AM wave has roughly the length of a soccer field between its peak and trough depending on what is being transmitted. AM works by adjusting the height (strength) of the electromagnetic waves depending on the sound being transmitted. An AM radio receives these radio waves and amplifies them with a speaker.

AM Quality

The basic nature of AM technology meant that the first radios could easily be mass produced. AM waves are easily affected by weather and large objects between the radio receiver and the transmitter. This means listeners experience different levels of quality on a daily basis while situated in the same place. AM's main advantage is its ability to follow the curve of the Earth and be received over long distances.

FM Waves

FM (Frequency Modulated) waves act differently than AM waves. They are a higher frequency of electromagnetic wave similar to VHF television signals. FM waves do not change their frequency or strength like AM waves, instead they adjust the gap between their peaks and troughs to transmit signal. They can be imagined as waves with varying gaps but uniform height traveling through the air. An FM radio can detect the varying gaps between waves and turn the signal into sound.

FM Quality

Unlike AM waves, FM waves do not deteriorate linearly with distance. This means that the quality remains the same regardless of the distance the listener is from the transmitter. Another advantage over AM radio is that FM can be broadcast in stereo, making it ideal for music. Because FM waves travel in a straight line, the transmitters are usually located on mountain tops or tall buildings in order for signals to be better received. The reason you eventually lose signal from an FM station as you move away from a transmitter is because the FM waves cannot follow the curve of the Earth.

Uses

Today both AM and FM radio waves are still in use as a form of transmitting sound. AM is preferred for transmitting over long distances because the waves follow the curve of the Earth, though it is subject to interference. AM's ability to be received over long distances means it can be used in aviation to communicate with aircraft. FM is chosen over AM for radio stations wishing to transmit in high quality to a smaller area because of its stereo capabilities.

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Radio Waves: AM Vs. FM

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