AM and FM Waves: What are the differences?

Waves are indeed a very crucial part of our lives. Waves are used in the transmission of voice, video or any other type of electronic media. However, when we talk about waves, we are faced with two types of waves, i.e., AM and FM.

So to help you understand which one of them is better and their modus operandi, we need to first discuss AM vs FM.

History Of AM And FM Waves

During the mid-1870s, the first audio transmission was launched using the Amplitude Modulation method. This transmission was initially used for audio transmission over radio and telephone lines. In contrast, the Frequency Modulation method of transmission was employed almost a half-century later by Edwin Armstrong in FM radios.

Moreover, the range of AM radio waves ranges from 536 to 1704 kilohertz. In comparison, the FM radio wave’s spectrum range is 87 to 107 megahertz. The FM radio waves can travel with a frequency of 10 kHz, whereas the FM radio can go up to 200 kHz.

What Is Amplitude Modulation

AM is abbreviated as Amplitude Modulation, and it is the method used in broadcasting or transmitting the signals of radio. In the 1870s, it was discovered that audio could be transmitted over a long distance using radio waves. Thus, these AM waves are further modified so that the broadcasting of the audio can be transmitted through a single input.

The amplitude of the carrier signal is modified proportionally, depending on the input. This indicates that the amplitude of the carrier wave signals reduces due to the low amplitude of the input signal, and the same happens when the amplitudes are high of both carrier and input signals.

What Is Frequency Modulation

The abbreviated term of Frequency Modulation is FM. It is the updated modulation method that is usually used in transmitting radio waves. These waves are similar to AM waves, but in FM, there is a modification in the frequency of carrier signals rather than its amplitude.

In the FM method, the frequency of carrier waves is proportionally modified, depending on the amplitude of the input signal. These waves transfer better quality audio, and therefore, many radio stations prefer the FM method over AM.

Difference Between AM And FM

There are several differences between AM and FM waves. Both have their pros and cons with certain distinct features. Let’s see some of the differences between both waves.

Basis	Amplitude Modulation	Frequency Modulation
Abbreviation	Often referred to as AM	Often referred to as FM
Frequency	AM operates between 535 kHz to 1705 kHz.	FM operates between 88 to 108 MHz.
Bandwidth	AM requires a bandwidth of 30kHz	FM waves require at least 180kHz to transmit signals.
Noise	AM waves easily get affected by noise, and their amplitude gets seriously affected by external noise.	As FM uses frequency to transmit signals, it is not very much affected by external noise.
Sound Quality	Although AM has lower sound quality, it can transfer signals to long distances.	FM operates on a high bandwidth, so it offers better sound quality.
Transmission	By differentiating amplitude	By variations in frequency
Cost	AM is expensive	FM is cost-effective

Advantages Of AM Waves

• AM waves are very easy to detect using simple appliances. They can be detected even when there is a poor signal.
• The bandwidth of the AM waves are narrow, and it covers a wide range compared to FM radio waves. Bandwidth is the difference between the lower and the upper limit of frequencies in the ongoing band of frequency.

Disadvantages of AM Waves

• While using AM waves in radio broadcasting, these waves get affected by electrical storms and create a lot of disturbance due to the interferences of different radio frequencies.
• Although the range of frequencies is 15 kHz, the radio transmitters are not able to reflect frequencies over 5kHz.

Advantage Of FM Waves

• FM waves produce better sound quality than AM waves in radio broadcasting.
• FM waves are flexible to noise and do not get disturbed due to interference from other radio signals.
• It provides better connectivity between the receiver and sender even when there are variations in the signal. This is why FM waves are considered ideal for radio transmission and mobile communications.

Disadvantages Of FM waves

• FM signals are suitable for local transmission, but they do not perform well over long-distance transmissions.
• The buildings and land masses act as a barrier to it, which constrains the coverage of these waves, resulting in low-quality audio.
• FM waves are a more complicated and expensive method for transmission than AM waves.

Application Of Amplitude Modulation

Amplitude modulation is indeed an outdated technology, but it is still relevant in certain situations. Some of its major applications are as follows:

Broadcasting

Amplitude modulation is used in broadcasting over small, medium and long-range wavebands. As this kind of modulation is easier to demodulate, this technology requires low-cost demodulators, which are easy to manufacture.

However, most companies nowadays prefer frequency modulation as it is capable of transmitting a higher quality signal.

Airborne Radios

A lot of security agencies still use AM for the transmission of signals. This is because these signals can easily be employed to establish steady communication between the pilot and the ground staff.

In HF Radio Links

AM modulation has a high transmitting power; hence, it is very useful in establishing point to point HF links. Therefore, this technology still finds its use in HF Radio Links.

Applications Of Frequency Modulation

Frequency modulation is the latest way to transmit signals, and hence it finds its application in all major devices that require high-quality transmission. Some uses of FM are as follows –

• FM waves are used in telemetry and to detect seismic activities in the study of earthquakes. Moreover, it is also employed in radar systems and used to monitor babies in the uterus through electroencephalogram (EEG).
• These waves are also used in the transmissions of videos over television or mobile phones. FM is used In magnetic tape recording devices and in the music synthesiser to generate better audio signals.

Now that you have understood the difference between these two types of waves, i.e., AM and FM, you will be able to differentiate between them conveniently. Moreover, you also have to learn the pros and cons and application of these types of waves. Remember these lessons and try to apply them in your examination of these types of waves.

Concluding Remarks

Frequency Modulation in most devices has now replaced amplitude modulation, but still, AM is significant when transmitting signals more quickly. The primary difference between them, which makes FM more preferable, is the superior sound quality of FM. So, if you want to make a rational comparison between the two, don’t forget to examine their pros and cons.

 

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