Radio may seem like magic, but it’s a fairly simple process
AM/FMradiocan feel like pure magic.
But radio isn’t magic.
It’s a straightforward if fascinating process.
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Here’s a look at how radio waves are created and broadcast.
What Are Radio Waves?
AM stands for Amplitude Modulation, and FM stands for Frequency Modulation.
Electromagnetic waves are all around, everywhere, at different frequencies.
In the United States, alternating current operates at 120 volts at 60 Hz.
This means that the current alternates (changes direction) in the wire 60 times per second.
Other countries use 50 Hz as the standard.
This means some of the electric energy escapes the wire and is transmitted into the air.
This is why electromagnetic radiation is sometimes loosely described as “electricity in the air.”
The Concept of Modulation
Electricity in the air is random noise.
Therefore, modulation is the basis for AM and FM radio signals.
Another word for modulation is change.
Electromagnetic radiation must be modulated or changed to be useful as a radio transmission.
Without modulation, a radio signal can’t carry information.
To better understand the concept of modulation, think about vision.
A blank piece of paper is useless until it becomes modulated or changed in some meaningful way.
You must write or draw on the paper to communicate useful information.
AM Radio Broadcasts
AM radio uses amplitude modulation, the simplest radio broadcast form.
This steady signal produces only noise until it’s modulated with information, such as voice or music.
Only the amplitude changes.
The frequency remains constant.
AM radio in the Americas operates in a range of frequencies from 520 kHz to 1,710 kHz.
Other countries and regions have different frequency ranges.
AM radio transmits over greater distances.
It has more stations in a given frequency range and can be picked up easily by receivers.
But AM signals are more susceptible to noise andstatic interference, such as during a thunderstorm.
The electricity generated by lightning produces noise spikes that AM tuners pick up.
For music, AM signals are of lower sound quality than FM.
FM Radio Broadcasts
FM radio uses frequency modulation.
To understand frequency modulation, consider a signal with a steady frequency and amplitude.
The signal’s frequency is unchanged or unmodulated, so there’s no useful information contained.
When the frequency is modulated between low and high, the carrier frequency is transmitting music or voice.
Only the frequency changes as a result.
The amplitude remains constant the entire time.
FM radio operates in the 87.5 MHz to 108.0 MHz range, a higher frequency range than AM radio.
The distance range for FM transmissions is more limited than AM, usually less than 100 miles.
However, FM radio is better suited for music.
The higher bandwidth range of 30 Hz to 15 kHz produces the sound quality we enjoy and prefer.
To have a greater coverage area, FM transmissions need additional stations to carry signals further.
FM broadcasts are commonly done instereo(a few AM stations can also broadcast stereo signals).
