MCQ in Microwave Communications Part 9 | ECE Board Exam

This is the Multiples Choice Questions Part 9 of the Series in Microwave Communications 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 Basic Principles of Microwave Communications
• MCQ in Electro-Optics
• MCQ in Photonics
• MCQ in Optoelectronics
• MCQ in Electromagnetics
• MCQ in Avionics, Aerospace, Navigational and Military Applications
• MCQ in Medical Electronics
• MCQ in Cybernetics
• MCQ in Biometrics

Continue Practice Exam Test Questions Part 9 of the Series

401. What is used to carry RF energy from magnetron to antenna in a radar set?

a) helix

b) parallel wire line

c) coax

d) waveguide

402. What is the method of illuminating a parabolic reflector with RF?

a) horn

b) cassegrain

c) helix

d) coax

403. How would a radar reflector be parabolic-shaped

a) circularly

b) vertically

c) horizontally

d) none of these

404. In what way are radar emissions similar to microwave ovens?

a) can transmit

b) can receive

c) can cook

d) can transceiver

405. To what tube is a dc keep-alive voltage applied?

a) Oscillator

b) Transmit-Receive Mixer

c) Circulator

d) Isolator

406. In radar, if the mixer diode burns out, what are replaced?

a) tube

b) mixer

c) antenna

d) diode

407. What is the cavity between magnetron and mixer cavity called?

a) ATR

b) TR

c) Transmit

d) Receive

408. Radar receivers use what Ifs

a) 20 MHz and lower

b) 10 MHz and higher

c) 30 MHz or higher

d) 10 MHz and lower

409. What kind of local oscillators does a radar receiver use?

a) klystron

b) magnetron

c) LSA

d) TWT

410. What solid-state types might be used as a radar receiver?

a) Gunn diode

b) Tunnel diode

c) Hot carrier diode

d) Step recovery diode

411. What does an ATR tube aid?

a) transmitting

b) receiving

c) both transmitting and receiving

d) neither transmitting and receiving

412. To what is the AFC voltage applied in a klystron?

a) cathode

b) grid

c) plate

d) any of these

413. Sea return is the control that desentisizes a radar receiver for _____

a) 5 – 10 microseconds

b) 15 – 20 microseconds

c) 10 – 15 microseconds

d) 20 – 25 microseconds

414. In radars, how is blooming prevented?

a) limit modulation

b) video signal

c) limit the carrier signal

d) limit the audio signal

415. How is brilliance controlled in radars?

a) audio gain

b) IF gain

c) RF gain

d) video gain

416. How is sensitivity limited in radars?

a) RF gain

b) video gain

c) audio gain

d) IF gain

417. How much intensifying pulse is used in radars?

a) Just enough to produce light flicker on screen

b) should be high to produce light flicker on screen

c) should be low to produce light flicker on screen

d) any amount of intensifying pulse will do

418. If echo signals are developed as negative pulses, to what part of the CRT would they be fed in radar?

a) anode

b) grid

c) cathode

d) 2nd grid

419. What starts the range-marker circuit ringing in radars?

a) intensifying pulse

b) IF gain

c) AC signal

d) Carrier signal

420. Why is a selsyn pair not too successful for radar antenna synchronization?

a) constant lead angle

b) variable lag angle

c) constant lag angle

d) variable lead angle

421. What is fed to the rotor of a selsyn motor?

a) power-line AC

b) DC source

c) A pulsating DC

d) None

422. What is fed to the rotor selsyn generator?

a) none

b) power-line AC

c) DC source

d) A pulsating DC

423. What is fed to a control transformer rotor?

a) A pulsating DC

b) power-line AC

c) DC source

d) none

424. What is used to indicate the bow of the ship on the CRT?

a) tail flash

b) body flash

c) heading flash

d) none

425. When is an echo box used on ships?

a) testing only

b) direction finding

c) auto alarm

d) ship detection

426. What qualification must a person have before he is eligible to make repairs to a radar set?

a) NTC endorsement

b) repair license

c) repair endorsement

d) radar endorsement

427. What is the advantage of using Doppler radar?

a) shows only moving target

b) shows stationary target

c) shows both moving and stationary target

d) produce blips with stationary targets

428. How would Doppler radar give speed indications?

a) adjust output burst

b) correct RF carrier output

c) switch amplitude detector

d) calibrate discriminator output

429. What is another application of Doppler radar?

a) distance between radar and stationary target

b) ground speed indicator

c) ground missile indicator

d) enemy base station

430. Why are signal nulls used in Radio Direction Finders work?

a) sharper than maximums

b) sharper than minimums

c) duller than maximums

d) duller than minimums

431. How many are signal nulls in one loop rotation Radio Direction Finders?

a) 3

b) 4

c) 5

d) 2

432. Under what conditions do the horizontal portions of a loop pick up difference currents in RDF?

a) ground waves

b) sky waves

c) space waves

d) direct waves

433. The method of balancing a loop used in RDF?

a) Capacitor to ground

b) Capacitor to sense antenna

c) Sense antenna to one side of loop

d) Any of these

434. For what are unidirectional readings used in loops for RDF?

a) resolve a 180 degrees ambiguity

b) resolve a 90 degrees ambiguity

c) resolve a 360 degrees ambiguity

d) resolve a 270 degrees ambiguity

435. What kind of antenna is a sense antenna used in RDF?

a) circular

b) vertical

c) horizontal

d) any of these

436. In RDF, what happens to a radio wave path as it moves outward across a coastline as less than 90 degrees?

a) bends away from the shore

b) travels along the shore

c) bends towards shore

d) travels across the shore

437. What is the result of antenna effect in RDF?

a) rotated 90 degrees

b) nulls shift

c) decreases land effect

d) coastline refraction

438. What is the result of re-radiation of signals in RDF?

a) great circle error

b) non-opposite minimums

c) polarization errors

d) nulls shifted

439. What causes night effect in direction finding?

a) ground plus space wave

b) sky plus space wave

c) ground plus sky waves

d) ground wave alone

440. At what time of the day is direction finder bearings least accurate

a) sunset

b) sunrise

c) mid-day

d) sunset and sunrise

441. At what angles are quadrantal errors maximum in direction finding

a) 45 degrees

b) 90 degrees

c) 180 degrees

d) 270 degrees

442. How are quadrantal errors corrected?

a) 330 degrees

b) 360 degrees

c) 315 degrees

d) 215 degrees

443. How is it that none of the 120-550 kHz ADF circuits are tuned to the desired station?

a) narrowband amplifiers

b) broadband amplifiers

c) IF amplifiers

d) Mixers

444. What is the only hand-tuned circuit in the ADF?

a) 3125-kHz signal local oscillator

b) 4125-kHz signal local oscillator

c) 2182-kHz signal local oscillator

d) 2230-kHz signal local oscillator

445. What forms the error signal that actuates the ADF servo-motor?

a) 75-Hz carrier

b) 114-Hz carrier

c) 114-Hz sideband

d) 75-Hz sideband

446. Which ADF antenna is used for manual operation?

a) parabolic antenna

b) loop antenna

c) half-wave dipole

d) helical antenna

447. Which ADF antenna is used for simple receive operation?

a) loop antenna

b) sense antenna

c) quarter wave antenna

d) parabolic antenna

448. What is heard by earphones in the ADF?

a) 3 kHz beat

b) 1 kHz beat

c) 2 kHz beat

d) 5 kHz beat

449. If two bearing are determined from a radio beacon or station over a period of a few minutes, what else must be known to determine the ship’s position?

a) speed

b) elapses time

c) ship’s course

d) any of these

450. What important point regarding-loop RDF system maintenance?

a) insulation at top of loop

b) clean moving contacts

c) oil bearing of loop

d) any of these

Questions and Answers in Microwave Communications and Principles Series

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

Complete List of MCQ in Communications Engineering per topic