Longwave vs. Shortwave Radio: We Iron out the Confusion
Site Owner & Radio Enthusiast
Radios use radio waves to transmit sound messages and information for communication. These waves are classified as either long or short, resulting in longwave and shortwave radios. Due to their mode of operation, there exists confusion between longwave vs. shortwave radio. What’s the difference, and how do they function?
A longwave radio tunes into longwave radio signals with low frequencies ranging between 30 and 279 kHz. On the other hand, shortwave radios tune into shortwave radio signals with higher frequencies ranging between 3 and 30 MHz (3,000 and 30,000 kHz).
In the rest of this article, I’ll discuss longwave and shortwave radios to clear any confusion. I’ll also talk about longwaves and shortwaves to help you understand the key differences.
Let’s get started!
What Is a Longwave vs. Shortwave Radio?
A longwave radio is a radio broadcasting technology that operates on frequencies between 30 and 279kHz. It’s mainly used for communication over straight lines since these waves can maneuver obstacles.
Longwaves follow the earth’s contour or travel beyond the horizon to reach the target receiver.
The long wavelength means these radios cover a broader distance in a single transmission. Therefore, they can travel several miles from the transmitting antenna to the receiving antenna.
Oppositely, shortwave radio is a radio broadcasting technology that operates on shortwaves and higher frequencies ranging between 3 and 30 MHz (3,000 and 30,000 kHz).
It’s mainly used for international communication over longer distances.
Unlike longwave radios, shortwave radios rely on the principle of bouncing signals off of the earth’s ionosphere before getting to the receiver.
Since the ionosphere contains a high proportion of free electrons, it vibrates and re-radiates the shortwave signals to the earth at the same frequency.
Shortwave radio broadcasts can travel several thousand miles from the transmitting point to receiving antenna due to the ionosphere radiation effect. This makes shortwave radio broadcasts ideal for:
● International news
● Cell phone communications
● Maritime communications
● Amateur radios
What Is the Difference Between Shortwave and Longwave?
The difference between shortwaves and longwave is their frequency ranges in the electromagnetic spectrum.
While shortwaves have higher frequencies ranging between 3,000 and 30,000 kHz, longwaves have lower frequencies, less than 300 kHz.
The best way to differentiate between short and long waves is by considering the relationship between the frequency and wavelength of a wave.
According to the Center for Science Education, frequency and wavelength are inversely proportional.
Therefore, shortwaves have short wavelengths and higher frequencies, while longwaves have longer wavelengths and lower frequencies.
What about the distance coverage between shortwave and longwave? Which one covers larger distances? The answer to this question comes down to a wave’s wavelength definition.
Northwestern University states a wave’s wavelength is the distance between two successive crests.
Therefore, longwaves have a longer distance between crests, while shortwaves have shorter distances between crests, as shown below.
Alt: Shorter and longer wavelengths. Source: Northwestern University
The longer the distance between two successive crests of a wave, the longer the distance it covers and the farther it can travel in a single transmission.
This explains why longwave radio broadcasts can cover longer distances in a single transmission.
However, long waves are unsuitable for international communication since they can only travel over straight lines.
Thus, they must navigate obstacles like tall buildings or mountains, which consumes much power.
Shortwave radio is a better option for international communication because it bounces off the earth’s ionosphere before getting to the receiver.
Longwave vs. Shortwave Radio: How Do They Operate?
Longwave and shortwave radios operate based on the following principles.
● Transmission: A transmitter at one end modulates or encodes messages. It does this by varying the frequency or amplitude of the waves, similar to what happens in Morse code.
● Receiving: A receiver on the other end receives and decodes the message into the desired form like image, data, or sound. For the decoding process to occur, the receiver must be tuned at the same frequency as the transmitter.
Although these radios operate on the above basic principles, they propagate their signals differently.
Longwaves propagate in a straight line, posing the risk of hitting obstacles and losing momentum.
However, although these waves travel in straight lines, they can maneuver barriers to get to the receiver.
For example, they can go over the horizon or follow the earth’s contour to reach their destination.
Shortwaves, on the other hand, propagate by re-radiating from the ionosphere. The transmitter directs the shortwaves at an angle toward the ionosphere for re-radiation.
Once they hit the ionosphere, they are re-radiated towards the receiver, overcoming the horizon obstacle.
Consequently, shortwaves cover longer distances, making them ideal for long-distance and international communication.
Why Are Longwave Radios Used in Maritime Communications?
Longwave radios are used in maritime communications because they excel at sending long-range signals at low power. The power requirement makes them energy-efficient and ideal for ships to communicate with inland utility stations.
Moreover, longwave radios can maneuver obstacles to reach their destination, making them suitable for maritime navigation.
The table below compares longwave vs. shortwave radio.
| Comparison Point | Longwave Radio | Shortwave Radio |
| Type of signal | Tunes to longwave signals | Tunes to shortwave signals |
| Purpose | Daily receiving of signals | Distanced communications |
| How signals travel | In a straight path | Reflection from the ionosphere |
| Best for | Community radio stations | Shortwave radio stations and areas where some broadcasts are prohibited. They are also suitable for emergencies |
| Popularity | Moderately popular across the world | Was popular in the 20th century. It also gained some popularity in 2020 during the Covid-19 pandemic lockdown |
| Frequency | Lower frequency due to the longer wavelengths | Higher frequency due to the shorter wavelengths |
Table 1: Longwave vs. shortwave radio comparison
Summary
Longwave and shortwave radios are radio broadcasting technologies with different operational properties.
Although longwaves travel in a straight path, they can maneuver obstacles to reach the receiver.
Shortwave radios operate by bouncing signals off the earth’s ionosphere to get to the receiver.
Hopefully this clears things up!
