NEET 2022 | Class 12

NEET Important Chapter - Communication Systems

Get plus subscription and access unlimited live and recorded courses
Communication Systems - An Important Topic of NEET

Communication Systems - An Important Topic of NEET

The term communication means the transferring, receiving and processing of information by electronic means. There are basically two communication modes : point to point and broadcast. In point to point mode of communication, the information is transferred from single transmitter to single receiver whereas in broadcast mode of communication, there are a large number of receivers corresponding to single transmitter.

In this chapter, students will learn about the basic communication system and different terms used in communication. Going further in this chapter, students will also learn about the meaning and need of modulation and demodulation.

In this article, we will cover the important concepts and topics that will help students to revise and boost their preparations for NEET.

Important Topics of Communication Systems

  • Basic Elements of Communication System

  • Important Terms Used in Communication Systems

  • Line Communication

  • Optical Communication

  • Optical Fiber

  • Modulation

  • Demodulation

  • Propagation of Electromagnetic waves

  • Satellite Communication


Important Concepts of Communication Systems

Sl.No

Name of the Concept

Key Points

1.

Basic Elements of a Communication Systems

  • Transmitter converts the message signal produced by the information source into an electrical signal which can be carried through the channel to the receiver. 

  • Communication channel carries the modulated wave from transmitter to receiver. 

  • Receiver receives the signal from the communication channel and converts it into original form.

(image will be uploaded soon)

2.

Important Terms Used in Communication systems

  • Analog signal: Signal which varies Continuously w.r.t time.

(image will be uploaded soon)

  • Digital signal: Signal which has two levels of voltage usually in the form of pulses,  represented by 0 or 1.

(image will be uploaded soon)

  • Transducer: It converts one form of energy into another. 

  • Noise: It refers to the unwanted signal that tends to disturb the transmission. 

  • Bandwidth refers to the range over which the frequencies in a signal vary. 

  • Amplification is the process of increasing the amplitude and thus strength of electrical signal. 

3.

Line Communication

  • In line communication, there is a physical connection between source and the destination. The wired connections between two connections are known as transmission lines. 

4.

Optical Communication

  • Optical communication uses light waves in the frequency range 1012 to 1016 Hz as the guided wave medium for the propagation of audio frequency signals.  

5.

Modulation

  • The phenomenon of superposition of an information signal over a high frequency carrier wave is called modulation. 

  • Digital and analog signals to be transmitted are usually of low frequency and hence, cannot be transmitted as such. 

6.

Amplitude Modulation (AM)

  • Amplitude Modulation is the process of changing the amplitude (Ac) of a carrier wave linearly in accordance with the amplitude of the message signal (Am). 

  • Modulation index (μ): $\frac{A_m}{A_c}= \frac{A_{max}-A_{min}}{A_{max}+A_{min}}$

7.

Frequency Modulation(FM)

  • Frequency Modulation is the process of changing the frequency of a carrier wave (𝛎c) in accordance with the frequency of the message signal (𝛎m). 

  • Modulation index (μf) = $\frac{\delta}{\nu_m}$

where, δ = maximum frequency of deviation

8. 

Demodulation

  • The process of recovering the original audio signal from the modulated signal. 

9.

Propagation of Electromagnetic Waves

  • Ground Wave Propagation: In this type of communication, transmitting and receiving antennas are close to the surface of earth. 

  • Sky Wave Propagation: Sky wave is the type of radio wave which is directed towards the sky and  reflected back from the ionosphere towards the desired location of earth. 

  • Space Wave Propagation: The transmitted signal is received by the direct interception of the signal by the receiving antenna. The maximum range of this transmission is given by, 

$d = \sqrt{2Rh}$

where, R = radius of earth and h = height of antenna


List of Important Formulae of Communication Systems

Sl. No

Name of the Concept

Formulae

1. 

Modulation index (μ)

$\frac{A_m}{A_c}= \frac{A_{max}-A_{min}}{A_{max}+A_{min}}$


2.

Voltage equation of Amplitude Modulated wave (e)

$e = E_c \sin\omega_ct+\frac{\mu E_c}{2}\cos (\omega_c-\omega_m)t-\frac{\mu E_c}{2}\cos (\omega_c+\omega_m)t$

3.

Modulation index (μf


$\frac{\delta}{\nu_m}$

where, δ = maximum frequency of deviation

4.

Height of Antenna

$d = \sqrt{2Rh}$


If the height of receiving antenna is also given, then maximum line of sight distance (dM)

$d_M = \sqrt{2Rh_T}+\sqrt{2Rh_R}$


The minimum height of antenna (not of antenna tower) should be λ/4 where λ is wavelength of modulating sig-

nal.


Solved Examples of Communication Systems

1. A TV tower has a height of 60 m. What is the maximum distance and area up to which TV transmission can be received? (Take the radius of earth as $6.4 \times10^6 $m.)

Sol: 

Given, 

Height of the tower (h) = 60 m,

Radius of the earth (R) =  $6.4 \times10^6 $m, 

Maximum distance upto which TV transmission (d) can be received is given by:

$d = \sqrt{2Rh}$

$d = \sqrt{2\times60\times6.4\times10^6}$

$d = 27.7 km$ 

Now, area (A) upto which transmission can be received will be: 

A = ℼd2 = $\pi\times (6.4 \times10^6)^{2}$

A = 2411 km2    

Therefore, distance and area upto which transmission can be received is 27.7 km and 2411 km2, respectively. 

Key Point: If the height of receiving antenna is also given, then maximum line of sight distance (dM), $d_M = \sqrt{2Rh_T}+\sqrt{2Rh_R}$

2. What is the purpose of modulating a signal in transmission?

Sol:

A low frequency signal cannot be transmitted to long distances because of many practical difficulties. On the other hand, effective transmission is possible at high frequencies. So, modulation is always done in communication systems.

Key Point: The phenomenon of superposition of an information signal over a high frequency carrier wave is called modulation.

Previous Year Questions of Communication Systems

1. A TV transmission tower has a height of 140 m and the height of the receiving antenna is 40 m. What is the maximum distance upto which signals can be broadcasted from this tower in LOS (Line of Sight) mode? (Given: radius of earth =$6.4 \times10^6 $m )  

  1. 65 km

  2. 48 km

  3. 40 km

  4. 80 km

Sol: 

Given, 

Height of transmission tower (hT) = 140 m, 

Height of receiving tower (hR) = 40 m,

Radius of earth (R) =$6.4 \times10^6 $m, 

In this question, the height of the transmission tower and height of the receiving antenna both are given. So, we will apply the formula: 

$d_M = \sqrt{2Rh_T}+\sqrt{2Rh_R}$

$d_M = \sqrt{2 \times 6.4 \times10^6 \times 140}+\sqrt{2 \times 6.4 \times10^6 \times 40}$

$d_M = 65 km$

So, Option - (a) is the correct answer.

Trick: If the height of receiving antenna is also given, then maximum line of sight distance (dM), $d_M = \sqrt{2R h_T}+\sqrt{2R h_R}$

2. A signal of frequency 20 kHz and peak voltage of 5 volts is used to modulate a carrier wave of frequency 1.2 MHz and peak voltage 25 volts. Choose the correct statement : 

  1. Modulation index = 5, side frequency bands are at 1400 kHz and 1000 kHz

  2. Modulation index = 0.2, side frequency bands are at 1220 kHz and 1180 kHz

  3. Modulation index = 0.8, side frequency bands are at 1180 kHz and 1220 kHz

  4. Modulation index = 5, side frequency bands are at 21.2 kHz and 18.8 kHz

Sol:

Given, 

Frequency of signal (fm) = 20 kHz, 

Peak voltage of signal (Vm) = 5 V, 

Frequency of carrier wave (fc) = 1.2 MHz = 1200 kHz, 

Peak voltage of signal (Vm) = 25 V,

Now, Modulation index (μ) is given by, $\frac{V_m}{V_c}$

Therefore, μ = $\frac{5V}{25V}$ = 0.2 

Value of modulation index is 0.2

Side bands are given by:

$f_1 = f_c-f_m$ = 1200 kHz - 20 kHz = 1180 kHz, 

$f_1 = f_c+f_m$ = 1200 kHz + 20 kHz = 1220 kHz,

Therefore, the right answer is option b.

Trick: Questions based on similar formulae will be asked in exams. So, be prepared for it. 

Practice Questions

1. The maximum amplitude of an AM wave is found to be 15 V while its minimum amplitude is found to be 3V. What is the modulation index?

Ans: 0.667

2. A TV transmission tower antenna is at a height of 20 m. How much service area can it cover if the receiving antenna is (i) at ground level, (ii) at a height of 25 m? Calculate the percentage increase in area covered in case (ii) relative to case (i) 

Ans: (i) 804 km2 (ii) 3608 km2 (iii) 349 %

Conclusion

In this article we have provided important information regarding the chapter Electromagnetic Induction such as important concepts, formulae, etc.. Students should work on more solved examples for securing good grades in the NEET exam.

See More
NEET Important Dates

NEET Important Dates

View All Dates
NEET 2022 exam date and revised schedule have been announced by the NTA. NEET 2022 will now be conducted on 17-July-2022, and the exam registration closes on 20-May-2022. You can check the complete schedule on our site. Furthermore, you can check NEET 2022 dates for application, admit card, exam, answer key, result, counselling, etc along with other relevant information.
See More
View All Dates
NEET Information

NEET Information

Application Form
Eligibility Criteria
Reservation Policy
Admit Card
NTA has announced the NEET 2022 application form release date on the official website https://neet.nta.nic.in/. NEET 2022 Application Form is available on the official website for online registration. Besides NEET 2022 application form release date, learn about the application process, steps to fill the form, how to submit, exam date sheet etc online. Check our website for more details.
NEET 2022 applicants should be aware of the eligibility criteria before applying to the exam. NTA has released all the relevant information on the official website, i.e. https://neet.nta.nic.in/. NEET 2022 aspirants should have passed Class 12th or any other equivalent qualifying examination in 2021, 2020, or students appearing in the Class 12th final exam in 2022 can also apply. For further details, visit our website.
As per the union government’s norms, NTA has released the NEET 2022 reservation criteria for different candidates’ categories (SC/ST/OBC/PwD), All India Quota, State Government Quota, Deemed Universities, and more. You can check more details on Vedantu website.
NEET 2022 Admit Card will be released by the NTA in the month of June 2022. Candidates can download the NEET admit card and hall ticket from the NEET official website i.e. https://neet.nta.nic.in/. For more details on the NEET admit card 2022, candidates can check Vedantu official website.
NEET 2022 Study Material

NEET 2022 Study Material

View NEET Syllabus in Detail
Download full syllabus
Download full syllabus
View NEET Syllabus in Detail
NEET 2022 Study Material

NEET 2022 Study Material

View all study material for NEET
All
Physics
Chemistry
Biology
See All
NEET Question Papers

NEET Question Papers

NEET 2022 Book Solutions and PDF Download

NEET 2022 Book Solutions and PDF Download

View all NEET Important Books
Biology
NCERT Book for Class 12 Biology
Physics
NCERT Book for Class 12 Physics
Chemistry
NCERT Book for Class 12 Chemistry
Physics
H. C. Verma Solutions
See All
NEET Mock Tests

NEET Mock Tests

View all mock tests
"NEET 2022 free online mock test series for exam preparation are available on the Vedantu website for free download. Practising these mock test papers of Physics, Chemistry and Biology prepared by expert teachers at Vedantu will help you to boost your confidence to face the NEET 2022 examination without any worries. The NEET test series for Physics, Chemistry and Biology that is based on the latest syllabus of NEET and also the Previous Year Question Papers."
See More
NEET 2022 Cut Off

NEET 2022 Cut Off

NEET Cut Off
NTA is responsible for the release of the NEET 2022 cut off score. The qualifying percentile score might remain the same for different categories. According to the latest trends, the expected cut off mark for NEET 2022 is 50% for general category candidates, 45% for physically challenged candidates, and 40% for candidates from reserved categories. For the general category, NEET qualifying marks for 2021 ranged from 720-138 general category, while for OBC/SC/ST categories, they ranged from 137-108 for OBC, 137-108 for SC and 137-108 for ST category.
See More
NEET 2022 Results

NEET 2022 Results

The NEET 2022 result is published by NTA on https://neet.nta.nic.in/ in the form of a scorecard on 7-Sep-2022. The scorecard will include the roll number, application number, candidate's personal details, and the percentile, marks, and rank of the candidate. Only those candidates who achieve the NEET cut-off will be considered qualified for the exam.
See More
Rank List
Counselling
Cutoff
NEET 2022 state rank lists will be released by the state counselling committees for admissions to the 85% state quota and to all seats in private medical and dental colleges. NEET 2022 state rank lists are based on the marks obtained in entrance exams. Candidates can check the NEET 2022 state rank list on the official website or on our site.
The NTA will conduct NEET 2022 counselling at https://www.mcc.nic.in/. There will be two rounds of counselling for admission under All India Quota (AIQ), deemed and central universities, AIIMS, JIPMER, ESIC, and AFMC. A mop-up round of NEET counselling will be conducted excluding 15% AIQ seats, while the dates of NEET 2022 counselling for 85% state quota seats will be announced by the respective state authorities.
NTA is responsible for the release of the NEET 2022 cut off score. The qualifying percentile score might remain the same for different categories. According to the latest trends, the expected cut off mark for NEET 2022 is 50% for general category candidates, 45% for physically challenged candidates, and 40% for candidates from reserved categories. For the general category, NEET qualifying marks for 2021 ranged from 720-138 general category, while for OBC/SC/ST categories, they ranged from 137-108 for OBC, 137-108 for SC and 137-108 for ST category.
Want to know which Engineering colleges in India accept the NEET 2022 scores for admission to Engineering? Find the list of Engineering colleges accepting NEET scores in India, compiled by Vedantu. There are 1622 Colleges that are accepting NEET. Also find more details on Fees, Ranking, Admission, and Placement.
See More
question-image

FAQs on NEET Important Chapter - Communication Systems

FAQ

1. What is the weightage of the Communication Systems in NEET?

Nearly 1-2 questions arise in the exam from this chapter.

2. What are the key points that need to be practiced for solving questions from Communication Systems?

Students should concentrate more on frequently asked questions and formulas as this is a short chapter. Similar kinds of questions can repeat. 

3. Are previous year questions enough for NEET?

To score 190+ in NEET, NCERT (both 11th and 12th) and previous year NEET Mains papers are sufficient. Solving previous 10-year NEET examinations offers us a tremendous advantage because 6-7 questions with the identical alternatives are guaranteed to be repeated every year.