CLARITY ON THE CONCEPT OF SKY WAVE PROPAGATION

Sky wave propagation belongs to the domain of radio wave propagation that generates electromagnetic waves. As the overall process of sky wave propagation goes through the ionosphere, it is also popular as ionospheric wave propagation. In the case of sky wave propagation, the frequency range lies between 3 MHz to 30 MHz respectively. On a primary note, the ionosphere is capable of reflecting electromagnetic waves ranging between 3 to 30 MHz. Additionally, electromagnetic signals with more than 30 MHz frequency mostly get penetrated instead of undergoing reflection. Therefore, the sky wave propagation is appropriate in terms of the particular range of mentioned frequency. 

Importance of sky wave propagation

The idea of sky wave propagation has been generated to negotiate two major disadvantages related to ground wave propagation. It helps to avoid obligations related to short distance propagation and low-frequency signal transmission efficiently. The notion of sky wave propagation allows the propagation of higher frequency of electromagnetic waves from one particular end to another, particularly in terms of a larger distance than the ground wave propagation. The overall process has been done by the wave reflections from the ionosphere. However, as it is not restricted to the Earth’s curvature, the concept of sky wave propagation can be used for communicating beyond the horizon, particularly in the context of intercontinental distances. Therefore, it is mainly utilized in different short wave frequency bands. 

Difference between local and distant sky wave propagation

Both the concept of local and distant skywave propagation can be used for long distance communications. In the context of local sky wave propagation, waves directed at a low angle have been utilized to communicate locally with the help of vertically directed waves. On the other hand, the distant sky wave propagation is broadly used for radio communication due to its capacity of reflecting or reflecting back towards Earth’s surface from different atmospheric levels, ionosphere to be precise. Ionospheric reflection is closely associated with the concept of distant sky wave propagation as it is seen as an electrically charged level of earth’s atmosphere. 

Applications of sky wave propagation

The notion of sky wave propagation is capable of propagating over large distances, therefore used extensively in the context of long-distance communication. Additionally, it is also used for satellite communications as it depends solely on the conditions of upper atmospheric levels. It is also broadly used for mobile communication that provides a better service. 

Key benefits of sky wave propagation

In the first place, a strategic application of sky wave propagation is beneficial in terms of supporting long distance propagation. Additionally, the range of frequency is considerably high in terms of sky wave propagation, thereby providing additional benefits to this context. Furthermore, it ensures attenuation because of less atmospheric conditions. 

Major disadvantages of sky wave propagation

There are several disadvantages related to the sky wave propagation restricting its functions deliberately. In the first palace, as the notion is related to long distance communication, it demands large-sized antennas and other infrastructures. On the other hand, because of the presence of atmosphere near and away during day and night respectively, the existence of variation in signal transmission can be found in day and night. Moreover, sky wave propagation demands a large amount or power for transmission along with a restricted frequency range of propagation that limits its functions. 

Critical frequency of sky wave propagation

The framework of critical frequency can be elaborated as the highest frequency at which the entire internal reflection happens from the atmospheric levels, ionosphere to be precise. The mathematical depiction of critical frequency is as follows:

ƒc=9 √Nmax

In the given equation, 

Ƒc stands for critical frequency in Hz and Nmax stands as the maximum electron density/m3.

On the other hand, the mathematical equation of critical frequency as a function  of MUF is as follows:

ƒc= MUF/secθ

Here, Ƒc stands for critical frequency in Hz, MUF stands for maximum usable frequency, and Ө stands as angle of incidence. 

In this context, critical frequency can be varied in terms of different atmospheric conditions along with particular time of a day and the specific angle of fire of the radio waves captured by the antenna.

Conclusion

It can be concluded from the previous discussion that sky wave propagation is closely associated with electromagnetic waves that are either refracted from or reflected through the ionosphere.  Therefore, propagating guided waves between earth’s surface and ionosphere. On the other hand, it is quite transparent to propagate waves with a higher frequency than those critical frequencies. However, Sky wave propagation is used extensively in long-distance communications that are satellite communications, and mobile communications.