Question

In which frequency range, space waves are normally propagated ? (A) HF (B) VHF (C) UHF (D) SHF

Short answer

Space waves are typically propagated in the VHF and UHF frequency ranges, so the correct options are (B) VHF and (C) UHF.

Step-by-step solution

Understand Space Waves

Space waves are a type of electromagnetic waves that travel through the atmosphere, directly from the transmitter to the receiver. They don't rely on reflection from the Earth's surface or the ionosphere and are mainly used for line-of-sight communication between antennas.

Identify the Frequency Range for Space Waves

Space waves typically propagate in the VHF (Very High Frequency) and UHF (Ultra High Frequency) frequency ranges. In these ranges, the antennas are smaller and more affordable, the signals are less affected by the Earth's surface and buildings, and the waves can penetrate through walls and other obstacles more effectively.

Choose the Correct Option

As space waves are typically propagated in the VHF and UHF frequency ranges, the correct option is (B) VHF and (C) UHF.

Key concepts

VHF (Very High Frequency)

VHF, or Very High Frequency, refers to the section of the electromagnetic spectrum with frequencies ranging from 30 MHz to 300 MHz. This frequency band is widely used for various communication applications due to its advantageous properties. VHF waves are known for their ability to travel long distances and penetrate obstacles such as buildings, which makes them ideal for line-of-sight communication.

• VHF is commonly utilized in FM radio broadcasting, television transmissions, and two-way radio communications, like those used by police and fire departments.
• In aviation and marine communication, VHF ensures reliable connections, vital for safety and coordination on air and sea.

Despite their utility, VHF signals can be obstructed by large natural formations such as mountains or dense urban buildings, which emphasizes the necessity of clear lines of sight for optimal transmission. Additionally, environmental factors like weather can sometimes affect the clarity and reach of VHF communications.

UHF (Ultra High Frequency)

Ultra High Frequency (UHF) is the band of electromagnetic frequencies ranging from 300 MHz to 3 GHz. It is known for supporting high-quality signal transmissions, allowing it to carry a wider bandwidth compared to VHF. Because of this, UHF has become a popular choice for a wide array of communication technologies.

• UHF is extensively used in television broadcasting, leading to better picture and sound quality due to its ability to provide greater data throughput.
• The frequency band is also crucial in mobile phone communications, Wi-Fi networks, and Bluetooth technology, enabling fast and reliable data exchange.

UHF waves are slightly more capable of penetrating through buildings than VHF, but can still suffer from obstructions like metallic objects or concrete walls. Urban settings, with their dense infrastructure, can sometimes cause signal disruptions. However, technological advancements continue to mitigate these challenges to ensure steady UHF communication performance in various environments.

Line-of-sight communication

Line-of-sight communication involves transmitting signals in a straight path between a transmitter and receiver, without significant obstruction. This method is crucial for both VHF and UHF frequencies. It ensures that the communication link remains effective and uninterrupted.

• Typical examples include satellite communication, microwave links, and optical communications like laser transmitters.
• The principle is widely utilized in both military and civilian telecom networks, owing to its reliability and direct transmission.

For successful line-of-sight communication, the antennas of the transmitter and receiver typically need to be elevated to avoid obstacles. The curvature of the Earth can hinder this type of communication over very long distances, requiring repeaters or satellites to maintain the connection. As technology evolves, devices and systems are continually improved to overcome these limitations, ensuring effective and expansive coverage.