Communication Electronics N6 — Memo

August 2021 — N6 — Communication Electronics

N6 2021 Nated Engineering

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🎯 100 marks 📄 11 pages 📝 31 items found 📚 1 topics

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Q1— Section header —

1.1(a) 𝐿𝐿 𝑍𝑍𝑜𝑜 1 = 𝜋𝜋 ( 𝐹𝐹 2 − 𝐹𝐹1 ) 600 = 𝜋𝜋 ( 4 000−1 000 ) 600 =  𝜋𝜋 𝑋𝑋 3 000 63 , 65 𝑚𝑚𝑚𝑚 = �⎯⎯⎯⎯⎯�  (2) (b) 𝐿𝐿 𝑍𝑍 𝑜𝑜 1 1 2 = ( − ) 4𝜋𝜋 𝐹𝐹1 𝐹𝐹2

1.21.2.1 Input

1.2.2Low-pass filter (2 × 1) (2) Copyright reserved Please turn over MARKING GUIDELINE -3- COMMUNICATION-ELECTRONICS N6

1.3• Attenuation does not rise sharply at cut-off. • The characteristic impedance is not constant over the pass band. (2) [14]14

Q2— Section header —

2.1• The size of the conductors • The spacing of the conductors • The dielectric constant of the insulator (3)3

2.2Make use of a stub constructed as shown below: The stub is a short piece of wire that is short-circuited across the transmission line. (4) Copyright reserved Please turn over MARKING GUIDELINE -4- COMMUNICATION-ELECTRONICS N6

2.3I ( in ) N = I out / uit ( ) 3 = 1 = 3  2  N + 1  N  Z 1 = R   − 2 R .R G G L   2 2   N − 1    N − 1   2  3 + 1  3  = 560   − 2 560 × 480    2 2 3 − 1    3 − 1    

2.4No, an attenuator only consists of resistive components, which are not frequency-sensitive. (3) [16] Copyright reserved Please turn over MARKING GUIDELINE -5- COMMUNICATION-ELECTRONICS N616

Q3— Section header —

3.13.1.1 R + ω j L Z O = G + ω j C 3 − 3 30 + j2 × 3,142 × 1,7 × 10 × 0,5 × 10 = − 6 3 − 9 1,9 × 10 + j2 × 3,142 × 1,7 × 10 × 0,045 × 10 30 + j5,341 = − 6 − 9 1,9 × 10 + j480,726 × 10

3.1.2γ = ( R + ω j L ) ( G + ω j C ) 0 − 6 0 = ( 30,47110,1 ) ( 1,96 × 10 14,2 ) − 3 0 = 7,728 × 10 12,2 -3 -3 = 7,553 × 10 + j 1,633 × 10 γ = α + j β -3 ∴ β = 1,633 × 10 rad/km (3) - 3 3.1.3 ∴ α = 7,553 × 10 nepers /km (2)2

3.23.2.1 To tune out reactive components

3.2.2To measure power along a transmission line

3.2.3To match an unbalanced device to a balanced device

3.2.4To determine the position and size of the first voltage maximum from the load (4 × 1) (4) Copyright reserved Please turn over MARKING GUIDELINE -6- COMMUNICATION-ELECTRONICS N6

3.3• Normalise the impedance. R X • Z O = ± j Z Z o o • Plot R on the centre line and X on the circle. • Follow the two lines until they intersect each other and plot this point. • Draw the circle with a radius equal to the centre of the chart and the point

Q4— Section header —

4.1DIODE NOISE GENERATOR RECEIVER UNDER TEST     NOISE FIGURE MEASUREMENT (5)5

4.24.2.1 E n = 4.K.T. F. R ∆ ( 1 + R 2 ) − 23 3 3 3 = 4 × 1,38 × 10 × ( 273 + 25 ) × 20 × 10 × ( 7,2 × 10 + 5 × 10 ) = 2,003 μ V Copyright reserved Please turn over MARKING GUIDELINE -7- COMMUNICATION-ELECTRONICS N6

4.2.2' R out / uit R eq =  R − R  +  eq t  2 A 3 × =  3 3 18 10 7,2 × 10 − 5 × 10  +   2 20 = 2,245 k Ω ' R eq ∴ F = 1 + R a 2245 = 1 + 300 = 8,483 (2 × 3) (6)6

4.34.3.1 R B R C R D R eq = R A + + + 2 2 2 2 2 2 A 1 A 1 .A 2 A 1 .A 2 .A 3 R A = R 1(in) + R 1(eq) = 300 + 1 750 = 2,05 kΩ R 1(out / uit) .R 2(in) R B = + R 2(eq) R 1(out / uit) + R 2(in) 3 3 30 × 10 × 150 × 10 3 = + 35 × 10 3 3 30 × 10 + 150 × 10

4.3.2E n = 4.K.T. f.R ∆ eq − 23 3 3 = 4 × 1,38 × 10 × ( 273 + 25 ) × 9 × 10 × 44,542 × 10 = 2,568 μ V (2) [21] Copyright reserved Please turn over MARKING GUIDELINE -9- COMMUNICATION-ELECTRONICS N621

Q5— Section header —

5.1Sampling is a process whereby parts of a signal are taken at a tempo of t = ½ f seconds and only the sample is transmitted. (6) Copyright reserved Please turn over MARKING GUIDELINE -10- COMMUNICATION-ELECTRONICS N6

5.2(10) [16]16

Q6— Section header —

6.1Path loss = 2 × 100 × 0,002 = 0,4 dB dB Path loss = antilog 10 0,4 = antilog 10 = 1,096 c λ = f 8 3 × 10 = 9 3 × 10 = 0,1 m 3 4 [ 4 π ] . d . P r P t = × 1,096 2 G t . G A . Q . λ 4 3  3   − 18  [ 4 × 3,142 ] × 100 × 10 × 1,8 × 10         = × 1,096 2 20 × 20 × 9 × 0,1

6.26.2.1 It is the ratio of power density radiated in a specific direction to the power density radiated by an isotropic antenna.

6.2.2It is the ratio of power fed to an antenna to the power radiated by the antenna. (2 × 2) (4) [14] TOTAL: 100 Copyright reserved14

Topics Identified

Business Plan

Mark Allocation

Total100 marks

Sections14 + 16 + 19 + 21 + 16 + 14 = 100 marks

Per-question sum100 marks

Paper information

TitleMemo

SubjectCommunication Electronics

LevelN6

Document typeNated Engineering

Year2021

MonthAugust

Pages11

Downloads3

Examination context

Decade2020s

Years ago5y

SeasonWinter (SH)

Start daySunday

Exam periodAugust 2021

Days since exam1,897

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

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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.

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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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