8 Most VSAQ’s of Communication Systems Chapter in Inter 2nd Year Physics (TS/AP)

2 Marks

VSAQ-1 : Define modulation. Why is it necessary?

Modulation is the process of superimposing a low-frequency audio signal (like voice or music) onto a high-frequency carrier signal for transmission. It is necessary for various reasons:

  1. Efficient transmission: Modulation allows the transmission of audio signals over long distances using high-frequency carriers, which are more efficient in terms of power and antenna size.
  2. Bandwidth efficiency: Modulation enables the utilization of the available bandwidth more efficiently, allowing multiple signals to be transmitted simultaneously without interference.
  3. Signal integrity: Modulation helps maintain the integrity of the original signal during transmission and reception, reducing signal distortion and noise.
  4. Signal identification: Different modulation techniques help identify and separate signals from various sources, preventing signal mixing and ensuring clear communication.

VSAQ-2 : Mention the basic methods of modulation.

The basic methods of modulation are:

  1. Amplitude Modulation (AM): In AM, the amplitude or intensity of the carrier signal is varied in proportion to the amplitude of the modulating signal. This results in the variation of the carrier signal’s strength, allowing it to carry the information.
  2. Frequency Modulation (FM): FM involves varying the frequency of the carrier signal according to the amplitude of the modulating signal. This results in a change in the carrier signal’s frequency, which carries the information.
  3. Phase Modulation (PM): In PM, the phase of the carrier signal is changed in response to the amplitude of the modulating signal. This alters the position of the carrier signal’s waveform, encoding the information.

VSAQ-3 : Which type of communication is employed in mobile phones?

In mobile phones, radio waves are used for communication, specifically employing a combination of different modes of propagation. The main modes of propagation used in mobile communication are:

  1. Space Wave (Line-of-Sight): In densely populated areas or urban environments, space wave propagation is dominant. The signals travel in a straight line between the transmitter (mobile phone tower) and the receiver (mobile phone).
  2. Ground Wave: In less populated or rural areas, ground wave propagation is significant. The signals follow the curvature of the Earth and travel along the ground to reach the receiver.
  3. Sky Wave (Ionospheric Propagation): In long-distance communications, especially for international calls, sky wave propagation is utilized. The signals are reflected by the ionosphere and return to the Earth’s surface, allowing long-range communication.

VSAQ-4 : What is sky wave propagation?

Sky wave propagation is a type of radio wave propagation where radio waves are transmitted into the Earth’s atmosphere and are reflected back to the Earth’s surface by the ionosphere, a region of charged particles in the upper atmosphere. This reflection allows the radio waves to travel long distances beyond the line-of-sight, making it suitable for long-range radio communication. Sky wave propagation is particularly important for medium and high-frequency radio communication, enabling long-distance radio broadcasts, international broadcasting, and long-range communication in certain areas.

VSAQ-5 : What are the basic blocks of a communication system?

The basic blocks of a communication system include the transmitter, which encodes the message into a suitable signal for transmission, the channel, which serves as the physical medium for signal transmission, and the receiver, responsible for capturing and decoding the transmitted signal to retrieve the original message.

VSAQ-6 : What is “world wide web” (www)?

The World Wide Web (WWW) is a system of interconnected documents and resources accessible via the internet. It relies on a set of protocols for sharing and retrieving information through web pages. Users access this information using web browsers, and web servers store and serve web content. The WWW operates on a client-server model, and hyperlinks interconnect web pages, creating a vast network of information and services.

VSAQ-7 : Mention the frequency range of speech signals.

The frequency range of speech signals typically falls between 300 Hz to 3100 Hz. This range encompasses the essential frequencies required for clear and intelligible human speech, with lower frequencies contributing to voice richness and higher frequencies ensuring speech clarity.

VSAQ-8 : Mention the various parts of the ionosphere?

The ionosphere is composed of several layers, including the D Region (located at about 65-70 km altitude during the day), the E Region (around 100 km altitude during the day), the F1 Region (in the mesosphere, between 170 km to 190 km), and the F2 Region (in the thermosphere, varying from 250 km to 400 km during the day and approximately 300 km at night). Each of these layers has specific properties and effects on radio wave propagation.