What is the wavelength of a 100-MHz (“FM 100”) radio signal?

Calculating the wavelength of a certain radio signal is basic physics. Everyone should know how to calculate a radio signal wavelength since we are all surrounded by these types of signals every day. If it weren’t for radios, we wouldn’t have all of the advanced technology devices which we have today.

What is the wavelength of a 100-MHz (“FM 100”) radio signal?

Ans: 3 meters

So, at the beginning of this article, we will be presenting you with basic facts about radio waves, and by the end of this article, you will know that the wavelength of a 100-MHz(“FM 100”) radio signal is three meters ( 9.8 feet). Also, you will learn how to calculate any type of wavelength and know how to do it in the future.

What are radio waves and what is wavelength?

Radio waves are located at the beginning of the electromagnetic spectrum, in front of the microwave region. They extend in the range of wavelengths from a few miles to 0.09 feet, which corresponds to a frequency of less than 109 HZ.

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By their nature, these types of radio waves are similar to the visible light, their main difference is in their wavelength- radio waves are much longer than waves of visible light. They are obtained by an alternating current generator, and they are created in the antenna when a high-frequency current causes an alternating change of the electric and magnetic field in its surroundings. This is also known as radiation. The larger the antenna, the longer will the wavelength be. Also, if the radiation frequency is lower, the wavelength will be greater, and vice versa.

Radio waves, from those with very low frequency to those with ultra-high frequency, are used in communication satellites, mobile telephony, navigation, as well as astronomy. They are transmitters of phones, television, and radio signals, and are also used for communication with submarines and planes.

Related: 11 Best FM Radio Antennas [reviews and buyer’s guide]

How to calculate the wavelength of radio waves

As we have mentioned before, there is a whole physic science standing behind this. But, this is yet a very simple calculation that anyone can learn how to do. The formula is pretty simple and can be remembered quickly.

Of course, before we start with the actual explanation, you will first need to learn and memorize some crucial tags when it comes to describing wavelengths.

Name Mark Measurement Unit
Wave elongation X Meter
Wave amplitude A Meter
Wavelength λ Meter
Wave period T Second
Wave Frequency F Hertz
Wave speed/velocity V/C Meter per second

Now that you recognize the units, we shall begin with the explanation of each one of these so that you can understand the matter better.

We will define the elongation and the amplitude of the wave on an example of the transverse wave. Wave elongation is the instantaneous distance of a selected point on the wave curve from the direction of wave propagation. The amplitude, on the other hand, is the maximum distance from the wave curve to the direction of wave propagation, which means that the amplitude is the maximum value of the elongation.

The wave period is the time during which the wave exceeds one of its wavelengths. On the other hand, the wave frequency is the number of wavelengths that the wave travels in the unit of time, one second. Frequency literally means how frequently the travel of the wave repeats over time.

The wave speed, or velocity, on the other hand, refers to the process of transmitting oscillations from one particle to another, and the oscillation speed is related to the movement of particles around the equilibrium position.

The relationship between the frequency of an electromagnetic wave f (HZ) and the wavelength λ (m) is a fundamental relation in nature. When the frequency and the wavelength are multiplied, we receive the speed of electromagnetic waves in free space and realize that the speed is constant. Each and every part of the frequency spectrum used in telecommunications is studied separately, whether it is the wireless or wired transmission. Telecommunication infrastructure and various transmission technologies are constantly being improved, but they are basically always based on fundamental principles.

Calculating the wavelength of a 100MHz radio signal

As mentioned before, you could easily calculate the wavelength of any type of wave. Here’s how.

  1. Since the frequency is 100MHz, and MHz is not the main unit of frequency, we first must convert it to the Hz. One hundred megahertz is 100 x 106 It’s important to always convert the units into main ones. Of course, have in mind that sometimes, you might have a wave frequency that is already been converted to Hz. In that case, there’s no need to convert it into any bigger unit.
  2. The second step to calculating the wavelength is knowing the speed of the radio signal. Since the speed is usually constant, it is around 3 x 108 m/s. This should be remembered as a constant if some other speed is not familiar to you.
  3. Lastly, the formula for calculating the wavelength is λ= c / f. Again, this is one of the most commonly used, and basically the main formula for calculating any type of signal wavelength if you already know the frequency of the wave and the wave speed.

Now that you know the basic steps to calculating any wavelength, let’s see how to do it for a 100MHz radio signal. Of course, we will follow the steps.

Frequency (f)= 100Mhz= 100 x 106 Hz

C (the speed of the wavelength) = 3 x 108 m/s


λ= c /f

λ= 3 x 10 8

       100 x 106

λ= 3 meters


λ = C/f


λ (Lambda) = Wavelength in meters

c = Speed of Light (299,792,458 m/s)

f = Frequency

therefore 100 Mhz = nearly 3 meters.

It’s pretty simple, don’t you think so?

Wavelength Chart (Frequency)

Frequency Wavelength




1 MHz 300 meters 75 meters 15 meters 3 meters
10 MHz 30 meters 7.5 meters 1.5 meters 30 cm
50 MHZ 6.0 meters 1.5 meters 30 cm 6.0 cm
100 MHz 3.0 meters 0.75 meters 15 cm 3.0 cm
200 MHz 1.5 meters 37.5 cm 7.5 cm 1.5 cm
300 MHz 1.0 meter 25 cm 5.0 cm 1.0 cm
400 MHz 0.75 meters 18.8 cm 3.75 cm 7.5 mm
500 MHz 0.6 meters 15 cm 3.0 cm 6.0 mm
600 MHz 0.5 meters 12.5 cm 2.5 cm 5.0 mm
700 MHz 42.9 cm 10.7 cm 2.15 cm 4.29 mm
800 MHz 37.5 cm 9.38 cm 1.88 cm 3.75 mm
900 MHz 33.3 cm 8.33 cm 1.67 cm 3.33 mm
1.0 GHz 30 cm 7.5 cm 1.5 cm 3.0 mm
1.2 GHz 25 cm 6.25 cm 1.25 cm 2.5 mm
1.4 GHz 21.4 cm 5.36 cm 1.07 cm 2.14 mm
1.6 GHz 18.8 cm 4.7 cm 9.4 mm 1.88 mm
1.8 GHz 16.7 cm 4.18 cm 8.35 mm 1.67 mm
2.0 GHz 15 cm 3.75 cm 7.5 mm 1.5 mm
2.5 GHz 12 cm 3.0 cm 6.0 mm 1.2 mm
3.0 GHz 10 cm 2.5 cm 5.0 mm 1.0 mm
4.0 GHz 7.5 cm 1.88 cm 3.75 mm 0.75 mm
5.0 GHz 6.0 cm 1.5 cm 3.0 mm 0.6 mm
10 GHz 3.0 cm 7.5 mm 1.5 mm

0.3 mm

Final thoughts- what is the wavelength of a 100 MHz radio signal

As you can see, the whole process of calculating the wavelength of any radio signal is pretty simple. All that you have to do is to remember one simple formula and focus on calculating the numbers right.

Today, we have come to the conclusion that the wavelength of a 100MHz radio signal is three meters. By using this method, you will surely be able to easily calculate the wavelength of any signal. We hope that we were able to help you understand the process right and that you will be able to do it in the future by yourself too.

what is the wavelength of a 100 MHz radio signal

Thanks for joining us today, until next time!


  1. What is the wavelength of a 100 MHz radio wave?

We have explained how to calculate the wavelength of a 100 MHz radio wave and came to the conclusion that the answer is three meters or 9.8 feet.

  1. How far can 400 MHz reach?

Using the simple physics formula to calculate the wavelength of a 100 MHz wave, you can also calculate the wavelength of any type of radio wave. In this case, the wavelength of 400 MHz is around 12 meters, or 39.3 feet.

  1. What is wavelength measured in?

The wavelength is measured in meters. However, you can easily convert this unit to feet.

  1. Is MHz bigger than kHz?

The frequency is usually measured in Hz. However, MHz and kHz are bigger units than Hz. To be more precise, kilohertz is smaller than megahertz.

  1. Does higher frequency mean shorter wavelength?

We have mentioned somewhere in this article that frequency is actually inversely proportional t the wavelength of the signal. In other words, the wave with a lower frequency is going to have a longer wavelength.


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