# MCQ in Transmission Fundamentals Part 10 | ECE Board Exam

(Last Updated On: May 6, 2020) This is the Multiples Choice Questions Part 10 of the Series in Transmission Fundamentals as one of the Communications Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies, Communications Books, Journals and other Communications References.

#### MCQ Topic Outline included in ECE Board Exam Syllabi

• MCQ in Transmission System
• MCQ in Transmission Medium
• MCQ in Velocity and Line Wavelength
• MCQ in Characteristics Impedance
• MCQ in Primary Line Constants and Propagation Constants
• MCQ in Standing Waves
• MCQ in Voltage Standing Wave Ratio
• MCQ in Telephone Lines and Cables
• MCQ in Wave Guides
• MCQ in Balanced and Unbalanced Lines
• MCQ in Twisted pair wire, Coaxial Cable
• MCQ in Decibel
• MCQ in Signal and Noise Fundamentals

#### Continue Practice Exam Test Questions Part 10 of the Series

451. Considering a coaxial transmission line, maximum voltage on the line divided by the minimum voltage equals the

a. Characteristic impedance

b. ISWR

c. VSWR

d. Inductive reactance

Solution:

452. In a transmission line, if the SWR or maximum current to a minimum current ratio of 2:1, the ratio of the maximum voltage to the minimum voltage is

a. 1:4

b. 4:1

c. 1:2

d. 2:1

Solution:

453. Transmission lines are either balanced or unbalanced with respect to

a. Negative terminal

b. Input

c. Ground

d. Positive terminal

Solution:

454. The load is properly matched with the transmission line if the standing wave ratio is equal to

a. 50

b. 10

c. 5

d. 1

Solution:

455. The radiation resistance of a quarter wave antenna is

a. 49 ohms

b. 288 ohms

c. 72 ohms

d. 144 ohms

Solution:

456. A radio transmission line of 500 ohms impedance is to be connected to an antenna having an impedance of 200 ohms. What is the impedance of a quarter wave matching line?

a. 300

b. 316

c. 316.5

d. 361

Solution:

457. The VSWR for a line terminated in its Zo is

a. 0

b. 1

c. 1.5

d. Infinity

Solution:

458. Which of the following is used to measure SWR?

a. Multimeter

b. Reflectometer

c. Spectrum analyzer

d. Oscilloscope

Solution:

459. A 75 – j50 ohm load is connected to a coaxial transmission line of Zo = 75 ohms at 10 GHz. The best method of matching consists in connecting

a. A short circuited stub at the load

b. A capacitance at some specific distance from the load

c. An inductance at the load

d. A short-circuited stub at some specific distance from the load

Solution:

460. For a two-wire line, Zo is higher when

a. The wire size is small with respect to the spacing of the conductors

b. The spacing is varied in accordance with the frequency

c. The D:d ratio is smaller

d. The wire is large with respect to the spacing of the conductors

Solution:

461. A resultant wave due to the combination of incident and reflected wave

a. Electromagnetic wave

b. Sine wave

c. Standing wave

d. Current

Solution:

462. For transmission line load matching over a range of frequencies, it is best to use a

a. Balun

c. Double stub

d. Single stub

Solution:

463. If the load impedance matches the characteristic impedance of the line, there are _____ standing waves.

a. More

b. Less

c. No

d. Ten(10)

Solution:

464. VSWR stands for

a. Voltage sending wave ratio

b. Voltage receiving wave ratio

d. Voltage standing wave ratio

Solution:

465. Reflections on a transmission line can occur when

a. Impedance of the source and load are matched

b. Impedance of the source and the load are mismatched

c. Resonance conditions are obtained

d. Power transfer between source and load is maximum

Solution:

466. A transmission line with characteristic impedance (Zo) of 300 ohms is terminated in a resistance load (RI). If by measurement, the minimum and maximum voltage through the load are 12 and 20 micro volts, respectively, what is the SWR?

a. 1.67

b. 0.6

c. 6.7

d. 3.67

Solution:

467. A measure of the mismatched between line and load impedance is called as

a. Reflection coefficient

b. Standing wave ratio

c. Loss

d. Standing waves

Solution:

468. Transmission lines when connected to antenna have

b. Resistive load whose resistance is less than characteristic impedance

c. Resistive load at the resonant frequency

d. Resistive load whose resistance is greater than the characteristic impedance of the line

Solution:

469. At matched condition, SWR is equal to

a. Zero

b. One

c. 100

d. Infinite

Solution:

470. An HF transmission line has a characteristic impedance of 600 ohms and is terminated by an antenna. The SWR along the line when the antenna impedance is 500 ohms is

a. 1.2:1

b. 1:2.1

c. 2:1

d. 1:2

Solution:

471. A characteristic of an infinite transmission line is that

a. The impedance in equals impedance out

b. It carries waves at the velocity of light

c. It can be connected to mismatched loads

d. The impedance varies with the length of the line

Solution:

472. A quarter wave transmission line shorted at the end:

a. Has the characteristics of parallel tuned circuit

b. Has the characteristics of a series tuned circuit

c. Has a minimum current at the end

d. Reflects a low impedance to the supply

Solution:

473. The outer conductor of a coaxial transmission line is usually grounded at the:

a. Input and output

b. Output only

c. Input only

d. Point of infinite resistance

Solution:

474. A certain feedline has a high SWR. It can be caused by:

a. Matching the load to the line

b. Use of non-resonant line

c. An impedance mismatched

d. Excessive transmitter output

Solution:

475. If the input impedance of an antenna is 300 ohms and it is fed with a 600 ohm balanced transmission line, the SWR on the line is

a. 4

b. 3

c. 2

d. 0.5

Solution:

476. A radio transmission line of 300 ohms impedance to be connected to an antenna having an input impedance of 150 ohms. The impedance if a quarter wave matching line is ___ ohms

a. 212

b. 450

c. 600

d. 150

Solution:

477. The ratio of the reflected voltage to the incident voltage on the transmission line is termed as

a. Standing waves

b. Standing wave ratio

c. Loss

d. Reflection coefficient

Solution:

478. Indicate the three types of transmission line energy losses

a. Radiation, I^2R and dielectric Heating

b. Conductor heating, dielectric heating and radiation resistance

c. I2R, RL and temperature

d. Dielectric separation insulation breakdown and radiation

Solution:

479. Termination means

a. Load connected to the output end of a transmission line

b. Result of disconnecting a line from a transmitter

c. Looking back impedance of a line with no load

d. Result of cutting both ends of a conductor

Solution:

480. When transmission line uses ground return, it is called a/n _____ line.

a. Ungrounded

b. Unbalanced

c. Grounded

d. Balanced

Solution:

481. Permeability is the measure of superiority of a material over a vacuum as a path of magnetic lines of force. The permeability of free space is equal to _____ henry/meter

a. 1.257 x 10^-6

b. 1.527 x 10^-6

c. 7.251 x 10^-6

d. 5.217×10^-6

Solution:

482. The most commonly used transmission line is a

a. Coax

b. Single line

c. Three-wire line

d. Two-wire balanced line

Solution:

483. The characteristic impedance of a transmission line does not depend upon its

a. Length

b. Conductor diameter

c. Conductor spacing

d. Thickness of armor

Solution:

484. What is the impedance of a balance 4-wire with a diameter of 0.25 cm and spaced 2.5 cm apart using an insulator with a dielectric constant of 2.56?

a. 100 ohms

b. 65 ohms

c. 75 ohms

d. 50 ohms

Solution:

485. It is required to match a 73-ohm antenna to a 600 ohm polyethylene coaxial feeder line, with a velocity factor of 0.66 by means of a quarter wave matching a transformer. At a frequency of 150 MHz, the impedance of the matching section is____ ohms.

a. 150.28

b. 310.5

c. 209.28

d. 450.82

Solution:

486. If the terminating impedance is exactly equal to the characteristic impedance of the transmission line, the return loss is____

a. Zero

b. Infinity

c. One

d. Negative

Solution:

487. The characteristic impedance of a transmission line is the impedance measured at the ____ when its length is infinite.

a. Shorted end of the line

b. Midsection

c. Input

d. Output

Solution:

488. The characteristic impedance of a transmission line is 70 ohms and has a load of 35 ohms. The SWR and reflection coefficient are _____ and _____ respectively

a. 1 and 0.333

b. 1 and 0.666

c. 2 and 0.666

d. 2 and 0.333

Solution:

489. It is required to match a 200 ohm load to a 300 ohm transmission line to reduce the SWR and attain resonance. A quarter wave transformer used, directly connected to the load has a Zo of ____ ohms.

a. 245

b. 425

c. 524

d. 254

Solution:

490. What quarter wave transformer will match a 100 ohm-line to an antenna whose value is 175 ohms?

a. 150 ohms

b. 137.5 ohms

c. 132.29 ohms

d. 16.58 ohms

Solution:

491. The mismatch between antenna and transmission line impedance cannot be corrected by

b. Using an LC network

c. Using a balun

d. Adjusting the length of the transmission line

Solution:

492. A pattern of voltage and current variation along a transmission line not terminated in its characteristic impedance is called

a. An electric field

c. Standing waves

d. Magnetic field

Solution:

493. The most desirable value of SWR on a transmission line is

a. 0

b. 1

c. 2

d. Infinity

Solution:

494. In transmission lines, the most desirable reflection coefficient is

a. Zero

b. 0.5

c. 1

d. Infinity

Solution:

495. At very high frequencies, transmission lines are used as _____.

a. Tuned circuits

b. Antennas

c. Insulators

d. Resistors

Solution:

496. What is the reflection coefficient of a 100 ohm characteristic impedance line and a 300 ohm load?

a. 0.25

b. 0.3

c. 0.5

d. 0.75

Solution:

497. The minimum voltage along a transmission line is 260 volts, while the maximum is 390 volts. The SWR is

a. 0.67

b. 1.0

c. 1.2

d. 1.5

Solution:

498. A single conductor running from the transmitter to the antenna

a. RG-8/U

b. Single line wire

d. Microstrip

Solution:

499. What characteristic impedance is needed to match a 50-ohm line to a 300 ohm-load?

a. 221 ohms

b. 122 ohms

c. 212 ohms

d. 112 ohms

Solution:

500. Indicate the false statement. The SWR on a transmission line is infinity; the line is terminated in

a. Short circuit

b. A complex impedance

c. An open circuit

d. A pure reactance

Solution:

#### Questions and Answers in Transmission Fundamentals Series

Following is the list of multiple choice questions in this brand new series:

MCQ in Transmission Fundamentals
PART 1: MCQ from Number 1 – 50                        Answer key: PART 1
PART 2: MCQ from Number 51 – 100                   Answer key: PART 2
PART 3: MCQ from Number 101 – 150                 Answer key: PART 3
PART 4: MCQ from Number 151 – 200                 Answer key: PART 4
PART 5: MCQ from Number 201 – 250                 Answer key: PART 5
PART 6: MCQ from Number 251 – 300                 Answer key: PART 6
PART 7: MCQ from Number 301 – 350                 Answer key: PART 7
PART 8: MCQ from Number 351 – 400                 Answer key: PART 8
PART 9: MCQ from Number 401 – 450                 Answer key: PART 9
PART 10: MCQ from Number 451 – 500                Answer key: PART 10

### Complete List of MCQ in Communications Engineering per topic

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