AM Radio: A Cornerstone of Communication in Rural America
What is AM Radio? How does it work? And how is it different from FM radio? Let’s dig into the details!
Right now in America, the viability of AM radio is in jeopardy. Companies like Ford are choosing to remove the technology from their cars, due to the high costs associated with harnessing that somewhat antiquated technology and the decrease in its use. It’s also not included in many new-model electric vehicles.
Do people even use AM Radio anymore? The answer is YES! It’s a very important form of communication and technology used in rural America that can’t be retired until a viable replacement is available to those that still rely on it.
Why is AM Radio being left in the dust? While not every car or truck owner regularly tunes into AM radio, the ones that do likely live and work in areas where they have limited access to the reach of FM stations. And what about satellite radio? While it’s available across America, it doesn’t provide local access to emergency communication, weather alerts, agriculture news, and high school or regional college sports broadcasts. Think about it, when you’re in the middle of nowhere in a bad storm and need information, you probably turn on AM radio!
Radio: Sound v. Light Waves
Did you know radio waves are floating all around you, in every direction, totally undetectable to the human eye?
Wait, don’t you mean ears?
Nope! Radio waves are technically a long-wave form of electromagnetic energy within the spectrum of light -- not SOUND!
However, sound and light waves are interconnected but travel at different speeds and are perceived in different ways. (Like when you see a lightning strike, and then a few seconds later hear the thunder it creates.)
Sound waves are mechanical. They need a medium (like air or water) to travel. Say, you are playing a musical instrument. You can exert more energy as you play, making the sound louder; or amplifying the instrument so it can be heard from farther away. But the distance the sound can travel is relatively small because it can only travel as far as its medium can take it. The further away from the source of the sound and the more physical barriers (like walls) between the listener and the origin of the sound, the less you will hear the sound.
Back in the 1920s, scientists wanted to figure out a way to transfer sound over much greater distances as a way to communicate. They were able to accomplish this — in a simplistic sense, by converting sound into light.
So, how is this possible? The answer is radio waves!
Unlike sound waves, radio waves are a form of electromagnetic light. Light doesn’t need a medium to travel. That’s why radio signals can travel through physical barriers and even through space! However, radio waves cannot be “heard” unless a process called “modulation” occurs. That is the modification or variation of one or more properties of the wave.
“Radio,” as we know it today, was discovered when scientists realized you could capture the energy of a sound (with microphones) and convert that energy into electricity.
A radio station’s transmitter emits an electromagnetic wave that doesn’t change until a sound is applied (aka “radio silence”). When a sound is captured by a microphone, it is converted into electricity, which can be carried through wires.
The electricity is converted (or “modulated”) into an electromagnetic signal that can be received by radio antennae. When that electricity is joined with a “carrier wave,” or signal, it can be transmitted from one place and received in another far away.
Once received, your radio then converts (or “demodulates”) the electrical signal back into sound waves and produces the noises you hear through your speakers.
SOUND EMITTED -> CAPTURED BY A MICROPHONE -> TRANSMITTER (ELECTRICITY + CARRIER WAVE) -> RECEIVER -> SPEAKER -> SOUND HEARD
Modulation of a radio wave can occur in two different ways, and it explains the difference between AM radio and FM radio.
What’s the difference between AM radio and FM radio?
AM radio and FM radio differ in the way they manipulate the carrier signal during transmission. Changing either the amplitude (the height of the wave) or frequency (the speed of the waves) of the carrier signal. [Another important thing to know is that amplitude and frequency are indirectly proportional, meaning as one increases the other decreases or must be held constant.]
AM and FM radios also operate in different frequency ranges and require different bandwidths (which determines how much information can be transmitted at once.)
What is AM Radio? What does AM Radio stand for?
AM Radio stands for “amplitude modulation.” Simply put, in AM radio, the amplitude is modulated. Amplitude affects the loudness or softness of the sound. So when the amplitude of a radio wave is increased, the loudness increases.
However, increasing the amplitude of a radio wave also decreases the frequency, so the sound heard on the other side of the transmission might be fuzzy or contain static on the other side of the transmission. This is also largely because AM radio is sent over a “medium frequency” and is prone to sound interference.
AM radio operates at a low frequency, between 535 kiloHertz and 1650 kHz, and a smaller bandwidth (10 kHz). As you adjust your dial, it changes by 10 kHz each time, so each station has that much bandwidth with which to broadcast.
What is FM Radio? What does FM Radio stand for?
In FM radio, the frequency of the carrier signal is changed. Frequency affects the pitch, or clarity, of a sound. As the frequency increases so does the quality of the sound. But, while the clarity of a sound increases at higher frequencies, the amplitude remains constant, so it travels a shorter distance than waves where the amplitude is modulated.
FM radio operates at a higher frequency than AM, between 88 megaHertz (mHz) and 108 mHz, and each station is allowed 150 kHz of bandwidth -- which means they can transmit 15 times more information at once than an AM station. That’s why music typically sounds much clearer on FM radio than on AM.
So, what’s better: AM radio or FM radio?
The real answer? It depends on what you’re trying to accomplish.
FM Radio is great for transmitting music because it sends a clear sound. However, since the amplitude remains constant, the broadcast can’t travel quite as far and is more easily obstructed by physical barriers, so it may not reach as many people.
AM radio is the better choice if you want your broadcast to reach as many people as possible, over a greater distance, and stay intact as it hits barriers like buildings or mountains. That’s why it’s such an important means of communication in rural America.
Until a more modern form of technology and communication (like broadband or fiber internet) is as widely accessible as AM radio, that technology must be still usable and accessible to all. Specifically, for the transmission and receiving of news, weather, and emergency communication.