Radio Waves : The Cold War between AM and FM broadcasting

3년 전

I was pretty bored and I decided to switch on my radio just to kill time, and it really did help me to annihilate and to murder boredom.

I was switching and tuning from one local FM station to another with sheer aplomb like I was flexing and cruising in a Ferrari and I even went further, in tuning to the AM bandwidth, where I listened to foreign radio stations like the BBC World Service and VOA etc. I was pretty much on top of the world and it felt like the whole world was in my hands … quite a number of radio stations were pleading and begging for me to select them.

Just like A-B-C, life was so easy while I was chilling, sipping some juice, with some shades on, tuning and switching stations on my radio device like I ran the world.

It was such an amazing feeling, flexing and doing all that and I’m not going to deny one thing. Also, it got me into real deep thoughts and I was pretty confused, curious, and also eager to know how the radio worked. Why FM sounded way better and why AM covered more area.


CC0 Creative Commons: Radio

So please stay with me and don’t change the dial.


For you to listen to the radio, a couple of things must happen. First of all, modulation must occur, which is such that the radio station needs to encode some sort of information into a radio wave. After which the station needs to broadcast these radio waves on a particular frequency. The antenna of your radio picks up the broadcast based on the frequency your radio dial is turned to. Information from the radio wave is then decoded by the radio which plays the information via the speakers as sounds. Now, you must wonder where the information comes from.

AM and FM explained

When I say AM and FM, I'm sure you know I don't mean ante meridian and football manager respectively. AM means amplitude modulation, which implies that to encode information the amplitude (height of wave) of the radio signal is used. FM stands for frequency modulation. Here, a change in frequency (number of waves that passes per second) is used in encoding information. We can see that both use modulation in encoding. So what exactly is Modulation?

Modulation may be defined as the variation of some property of the radio carrier in a manner that conveys information.

Modulation debugged

To fully understand why modulation is important I will use the semaphore flag analogy. Stop looking at me that way. Semaphore is a way of conveying messages by holding two flags. Different positioning of the flags mean different letters or numbers. Now, If you are trying to convey a message and you hold the flags in the same position, the messages are the same. The person you are trying to relay the message to won't be able to understand the message as he will see no difference in meaning.

In semaphore, outstretching your arms would mean the letter “R”, while if you outstretch your right arm and place the left arm above your head you are representing the letter “P”.

With the analogy delivered, the concept of radio modulation should be easy to understand. If a simple sine wave is to be transmitted by a radio station, to encode the information wouldn't be possible as the message would always look the same. To send out any useful information, the radio station must find a way to manipulate the shape of the radio waves, which is done using either form of modulation. Let's start alphabetically.

AM - Amplitude Modulation

I'm sure you are still wondering how exactly the information is encoded. The first thing you need is the carrier signal (a simple unmodulated sine wave), a wave that has no change in amplitude or frequency. Next, you need a wave that resembles the information you want to pass out. The amplitude of the wave will change based on the message send out.

For the sake of simplicity, let's assume we want to send out letters instead of sounds, letter A will be represented by a small amplitude, while Z will be represented by a very big amplitude and other alphabet letters will fall respectively in between. You can think of it as a geometric progression or arithmetic sequence will a positive common ratio and common difference respectively.

Once both the carrier and the message signals are ready, we multiply them together. When this is done, the amplitude of the carrier signal is changed in accordance with the amplitude of the message signal. The actual broadcast signal consists of the combined waves of the carrier and message signals. When your radio antenna picks up the signal, the radio must then determine the difference between the amplitude of both signals and convert these differences in amplitudes back to letters.

In simple terms, if the difference between the amplitude of the waves is 2, that is equal to letter A, if the difference is 4 that's letter B, if the difference is 6 ... well you get the gist. That's simply how amplitude modulation works. Pretty easy, right? Now let's talk about the other form of modulation and learn how it is done and later in the post I will explain which is best and why.

FM - Frequency Modulation

If you understood the concept of AM modulation then you should have no problem understanding this since it's almost the same thing. Again you need a simple sine wave to be the carrier signal and you need to develop the message signal. Now, instead of varying the amplitudes as in AM modulation, you vary the frequency of the carrier signal.

In simple terms, the lowest frequency will represent A while the highest one will represent Z and others fall in accordingly. When your antenna picks up the final signal, the changes in frequency will be used in decoding the actual broadcast message.

Why FM radio stations sound better

If you are a radio enthusiast like myself, you must have noticed that the FM radio stations sound way better than the AM radio stations. Did you ever find out why? If not, then today is your lucky day. I will fill you in on the details why FM radio stations sounds better than the AM radio stations. The three main reasons responsible for this are: the signal strength, interference, and frequency range. Let's start with interference.

  • Interference
    The sun, yes that one up there produces a lot of AM radio waves and most radios are not able to distinguish between the natural AM waves and the ones broadcast by your favorite AM radio station. This is why your AM radio seems to sound better at night. This interference is one of the reasons why the FM radio stations sound more sonorous than the AM radio stations.
  • Signal strength
    Another reason for this is the signal strength at which these two forms of radio broadcast. The FM radio stations can transmit their broadcast at up to 100 kilowatts of power while AM radio stations can only broadcast not exceeding 50 kilowatts, this is due to national regulations like the Federal Communication Commission in the United States and the Nigerian Communications Commission in Nigeria.

Also, by altering the amplitude of broadcast signal for AM radio, the power at which the signal is transmitted is also affected, as the amplitude is the strength of the signal. Whereas in FM radio the amplitude doesn't change, therefore the strength of the signal doesn't change.

  • Frequency range
    Lastly, one other advantage the FM radio has over the AM radio is that it can broadcast over a higher frequency range. The FM stereo operates between 88 MHz and 108 Mhz with an increment every 200 kHz, while one the other hand, the AM radio operates between 535 kHz and 1605 kHz, and when you change the dial on the AM radio it's number changes by 10 kHz each time.

This means the stations have 10 kHz of bandwidth each to broadcast on. Although due to NCC and FCC regulations, FM stations can only use 150 kHz of bandwidth, it is still 15 times that of the AM stations. Simply put, the FM radio stations can transmit 15 times as much information as the AM radio stations can.

Why AM covers more area

With all I’ve said above you may be wondering why anyone still uses AM radio. But if you noticed earlier in my introduction I was curious as to why AM radio covers more area which is the only advantage it has over FM radio. Now, let me explain to you why it is so. I'm going to paint a scenario so you can understand.

Imagine you are traveling from Kano (north) to Ibadan (south west) by land, you will have to pass through several cities. So, let's say flooding occurred in one of the cities you are supposed to pass - let's assume Benin city (east) and you are not sure whether you will be able to pass through. It would do you well to know ahead of time so you can plan your route accordingly. Wouldn't it be nice if you could have a station broadcasting Benin city traffic reports while you are still in Kano? Is this even possible? The answer is yes, it's possible.

Since AM radio broadcasts at a lower frequency, it has a larger wavelength (frequency of a wave is indirectly proportional to its wavelength). Larger wavelengths are able to travel farther as they can travel through solid matter. FM radio, however, has shorter wavelengths and doesn't travel well through solid objects.

To paint a clearer picture, a girl can run in the rain, but a mosquito can't since it's almost the same size with a raindrop. The wavelength of AM radio is are much bigger than the atoms of the solids that's why they can easily travel through them (just like the girl in the rain). FM wavelengths are smaller when compared with the atoms of solids. Therefore can't travel easily through it (just like a mosquito can't fly in the rain).

AM radio waves are also reflected off the ionosphere which is another reason why we can hear them from far away. Lower frequency waves are easily reflected than high frequency waves.


I personally enjoy listening to radio, it's liberating unlike the television that I always have to look at the screen. I can keep radio in my pocket and listen to it as I walk around in hot sun. It will be a cold day in hell the day I stop listening to radio.

Although, over the past decades, the usage rate of radio has dropped significantly due to advancements in technology. Radio used to be a lifesaver, my dad told me he listened to the whole of the 1978 World Cup on the radio.

Now that you have understood the that radio reception depends on some many factors ranging from geological location to type of modulation, I guess you now know why you can't find your favorite AM station at a particular time of the day or why you can't listen to your beloved FM station when you are out of town.


J.J Carr. “Elements of Electronic Communications.” Reston, Virginia: Reston Publishing Company, Inc., 1978.

R.S. Carson. “Radio Communications Concepts: Analog.” New York: John Wiley & Sons, 1990.

Editors and Engineers The "Radio" Handbook. Los Angeles: Editors and Engineers, 1942.

FM broadcasting

AM broadcasting

AM vs FM; differences and comparison

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When I say AM and FM, I'm sure you know I don't mean ante meridian and football manager respectively.

Rofl! This is a good one. I will definitely reuse it.

Are AM radios popular in Nigeria? It seems that yes from your post. In France, most the good stuff is on the FM bandwidth. I have actually never tried the AM one even if I could access it. I admit that Nigeria is much larger, but not that larger than France, isn't it?


When I was younger, I listen to BBC Radio for live commentary on arsenal matches, live from the UK. That was possible because of the AM. AM allows listening to other countries, I even listen to some French music from time to via the AM. For me the best stuffs are on AM due to larger coverage.

France is approximately 643,801 sq km, while Nigeria is approximately 923,768 sq km. Meanwhile, the population of France is ~67 million people (119 million more people live in Nigeria).

It's nice have you in my country. Thanks for stopping by.


I have no plan to visit Nigeria in a close future. Namibia and South Africa are my next stops in Africa (I will blog about this soon or later as this is connected to the development of particle physics in Africa). I also turned down an invitation to Egypt. I cannot go everywhere all the time ;)


Nigerian are probably the most intelligent people in Africa, I don't know why you would not want to come over and work with the best minds. ☺ ☺

Have you been to Africa before?

In my first comment, I meant to say "it's nice to have you in my comments "


I have been to South Africa in 2016, as particle physics is well developed there (and they organize some major events once in a while) . This consists of my only trip to Africa for now.


I hope you enjoyed your stay in Africa.


I did :)


I'm glad you did. ☺

One of My professors do say that AM signal can be likened to a man riding a horse. He does not really have anything protecting him and that why AM channels seem more noisy while FM signals are like babies in their mothers womb. They are well protected and that explains clarity in FM channels. Modulation and demodulation are key concepts in radio engineering and telecommunication in general.
Thank you for this informative post. You deserve some accolades


Thanks for the additional information.
You can bring my accolades already.

This kind of post make me wish I had more vp. This is top quality and great simplicity displayed

Would I have ever learnt these concepts in clearer words? I doubt!

The analogies and tone of delivery just got me.

Thanks for this graceful lecture. I have more than learnt.

AM before now always looked like a bad child deserving an isolation. I had even once thought they nonfunctional - more like a dummy, on the radio set

Maybe because I'm not the radio fan, I wouldn't have known channels - even international ones existed on it.

I appreciate this effort. Keep growing..


AM before now always looked like a bad child deserving an isolation.

This got me 😂 😂

Thanks for all of the nice words.

Let's keep growing together.

You've done so well in breaking this radio engineering concept deep down for understanding..I enjoyed the concept of signal modulation and demodulation while in school..I was taught by a brilliant Professor though
Thanks for refreshing my memory of this.


You are welcome bro,
Thanks for the comment.

I have sincerely learnt something today all thanks to you.

The ability of AM signals to travel far is one reason it is still used otherwise, it would have been long gone.


The ability of AM signals to travel far is one reason it is still used otherwise, it would have been long gone.

You are absolutely right.
Thanks for dropping by.

wow!you really dealt with the concept of AM and FM in simple and clear terms that is.


Thanks bro

This is intriguing and informative. Even I was able to grasp your concepts.

This post was selected by the MSP manual curation team. Thank you for not using bid bots.


I am glad you liked it.
Thanks for dropping by.


My pleasure!

I must confess that I only passively knew about AM, until I read this post that is. And just like you pointed out, I've always wondered why there is a space for them in radios. Thank you for this enlightenment.

A question though, is there any similarity between these two and the UHF/VHF in "analog" television broadcasting?


It delights me to know that I have impacted knowledge.

A question though, is there any similarity between these two and the UHF/VHF in "analog" television broadcasting?

I want to believe they are similar. UHF is like the FM band, while VHF is like the AM band.

I like the explicit nature of your write-up. The introduction was compelling and the analogies given in the body made it easy to read.

Personally, I am not a radio listener and I have never taken cognizance of the difference between FM and AM station, say less of asking why. Thanks for the eye opener.


You are most welcome.

Thanks for dropping by

Hello! I find your post valuable for the wafrica community! Thanks for the great post! @wafrica is now following you! ALWAYs follow @wafrica and use the wafrica tag!

No wonder the hausa still manage to pick up their channel all the way from the north to the south.. I always thought there was a special frequency for such.. But they simply use AM on their radio.

Well written.. Thumbs up.


Glad you now know there isn't a special frequency.
Thanks for the kind words.


Yeah.. Feels good to know!

Your knowledge on this topic is kind of amazing, I am so glad your post has been selected by an @minnowsupport member. I hope you will chat more in our discord and meet others interested in STEM topics like you.


Thanks for your comment.

May I message you on discord?

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This is highly enlightening as I got to read more... but little did I know FM is Football manager.

When I say AM and FM, I'm sure you know I don't mean ante meridian and football manager respectively


Thanks for stopping by

To be blunt i never knew there exit a difference between AM and FM. My ideas on both is oxymoronical. I know PM well but no knowledge whatsoever for AM. I used to think AM was just o add to the characteristics of a radio without a function.. I can now boldly say from what i have learnt here how to decipher between the two..
What a post!


I'm glad I could help you with that.

Thanks for stopping by.