Communication Electronics N4 — Document

April 2021 — N4 — Communication Electronics

N4 2021 Nated Engineering

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Q1— Section header —

1.10in the ANSWER BOOK.

1.1The impedance of series circuit at resonance is a maximum

1.2Radio waves travel at the speed of sound.

1.3A radio antenna is omnidirectional.

1.4The output of a travelling wave tube increases exponentially.

1.5A parabolic reflector is a converter in radio communication.

1.6The function of a ratio detector is to convert IF to audio.

1.7A speaker converts audio to electromagnetic waves.

1.8network designed to stop a certain band of frequencies is known as a filter.

1.9The impedance in any antenna will set up magnetic and electric fields.

1.1010

Q2— Section header —

2.1Define each of the following:

2.1.1theorem

2.1.2

2.2Use the uperposition theorem to find current flowing through resistor R in the network below. (7\ [11]11

Q3— Section header —

3.1Calculate each of the following .1.1 requency at resonance .1.

Q3— Section header —

1.3using any alternative method (2\ [10] 808022410

Q4— Section header —

4.1Make neat sketches of each of the following attenuators

4.1.1Bridge T type

4.1.2

4.2Name the advantages of a ceramic filter over other filters. (2\

4.3.1Draw a circuit diagram of a low pass filter.

4.3.2Draw the basic gain versus frequency graph for the filter in QUESTION

4.3.1[8]8

Q5— Section header —

5.1Name FOUR different modulation types used in communication networks. (4\

5.2Explain THREE advantages and THREE disadvantages of amplitude modulation. (6\ [10]10

Q6— Section header —

6.1Draw fully labelled block diagram of an AM receiver. (9\

6.2A 540 kHz carrier wave with an amplitude of 10 V is modulated by a 9 kHz audio signal with an amplitude of 5 V (AM transmitter\.

6.2.1Determine the TWO main frequencies which will show up in a spectrum analysis of the modulated wave. (2\

6.2.2Draw the audio signal. (2\

6.2.3Draw the carrier signal. (2\

6.2.4Construct the modulated wave. (2\

6.3Draw the circuit diagram of an AM full wave detector. (2\ [19] 808022419

Q7— Section header —

7.1Explain how electromagnetic wave are radiated from an antenna. (2\

7.2Draw block diagram of an FM transmitter and briefly explain the function of each stage. (16\ [18]18

Q8— Section header —

8.1Explain the difference between directional and an omnidirectional antenna. (2\

8.2Define silent zon as applicable to radio wave propagation. (2\

8.3Briefly explain sunspots and the influence they have on radio communication. (2\

8.4Define refraction in the ionosphere (2\

8.5Describe what is meant by beam width regarding antennae. (2\

8.6Make neat labelled diagrams of each of the following antennae:

8.6.1Loop antenna

8.6.214

Mark Allocation

Total100 marks

Sections10 + 11 + 10 + 8 + 10 + 19 + 18 + 14 = 100 marks

Paper information

TitleDocument

SubjectCommunication Electronics

LevelN4

Document typeQuestion paper

Year2021

MonthApril

Pages7

Downloads5

Examination context

Decade2020s

Years ago5y

SeasonAutumn (SH)

Start dayThursday

Exam periodApril 2021

Days since exam2,019

About Communication Electronics examination preparation

This TVET examination resource can be used as part of a structured revision programme. Past papers are most useful when learners attempt questions independently, work within a realistic time limit, and review their answers afterwards.

How to use this resource for revision

A TVET past examination paper is most useful when it is treated as an active revision exercise. Try the questions yourself before checking the corresponding memorandum. Where you make an error, identify the reason — was it a knowledge gap, a calculation mistake, an interpretation issue, or an examination technique problem?

For stronger examination practice, complete the paper without unnecessary interruptions and keep track of the questions that take the most time. Afterwards, review the memorandum and separate knowledge gaps from mistakes caused by interpretation, calculation, structure, or examination technique.

understanding question requirements

applying subject knowledge

working under time constraints

checking answers

identifying revision priorities

A practical revision approach

Start by completing the resource without looking at the memorandum. Review incorrect and incomplete answers afterwards and make a short revision list based on the areas that caused difficulty.

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