This is the Miscellaneous Multiples Choice Questions Part 7 of the Series in Communications Engineering. 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 past Board Questions in Communications Engineering field (Electronics Systems and Technologies). In the actual board, you have to answer 100 items in Electronic Systems and Technologies within 5 hours. You have to get at least 70% to pass the subject. Electronic Systems and Technologies is 30% of the total 100% Board Rating along with Mathematics (20%), General Engineering and Applied Sciences (20%) and Electronics Engineering (30%).
Practice Exam Test Questions
Following is the list of multiple choice questions in this brand new series:
Continue with Part VII of the Series
Choose the letter of the best answer in each questions.
301. In reducing the voltage by ½, there is a decrease of _____.
- a. 2
- b. 3
- c. 4
- d. 6
302. A measure if mismatch in a transmission line.
- a. Reflection coefficient
- b. Propagation delay
- c. Standing wave ratio
- d. All of these
303. Which type of transmission line has the least velocity factor?
- a. Air-insulated parallel line
- b. Air insulated coaxial line
- c. Polyethylene parallel line
- d. Polyethylene coaxial line
304. It is required to match a 73 ohm antenna to a 600 ohm transmission line, with a velocity factor of 0.66, by means of a quarter-wave matching transformer. At a frequency of 150 MHz, calculate the length of matching section, in feet.
- a. 2,2
- b. 0.8
- c. 1.0
- d. 1.8
305. A transmitter radiates 5 kW with unmodulated carrier but when the carrier is sinusoidally modulated, it radiates 6.5 kW. Now, another sine wave corresponding to 40% modulation is transmitted simultaneously. Determine the total radiated power.
- a. 6.9 kW
- b. 6.5 kW
- c. 6.4 kW
- d. 7.6 kW
306. A circuit which is used to keep the signal levels approximately constant in the RF stage and the mixer of an FM receiver.
- a. AGC
- b. AFC
- c. Local oscillator
- d. Limiter
307. The highest frequency that can be set back to earth by the ionosphere, if the wave is sent vertically upward.
- a. Maximum Usable Frequency (MUF)
- b. Critical frequency
- c. Propagating frequency
- d. Cut-off frequency
308. The difference between the farthest point the direct wave extend and the nearest point the sky wave reflected to ground.
- a. Skip distance
- b. Radio horizon distance
- c. Dead zone
- d. Fresnel zone
309. Power density is defined as radiated power per unit area, it follows that power density is reduced to ¼ of its value when distance from the source is____.
- a. Double
- b. Three-fold
- c. Four-fold
- d. Five fold
310. If the clearance above the obstruction is equal to the second Fresnel zone, the path of the reflection wave is physically _____ wavelength longer than the direct wave.
- a. One-half
- b. One
- c. Two
- d. three
311. Attached around the rim of the parabolic antenna to eliminate side-lobes causing interference to nearby microwave station.
- a. Radome
- b. Feed-horn
- c. Reflector
- d. shroud
312. It is polar diagram representing field strengths or power densities at various angular positions
- a. Lobe
- b. Radiation pattern
- c. Beamwidth
- d. All of these
313. The gain of a Hertzian dipole with respect to an isotropic antenna.
- a. 4.15 dB
- b. 2.15 dB
- c. 1.76 dB
- d. 5.15 dB
314. A kind of noise in the form of randomly occurring spikes.
- a. White noise
- b. Impulse noise
- c. Johnson noise
- d. Thermal noise
315. Sound intensity varies directly to square of
- a. Velocity
- b. Density
- c. Pressure
- d. frequency
316. Rarefraction produces
- a. crest
- b. sound
- c. vibration
- d. trough
317. What are the basic components of a microphone?
- a. Coil and magnet
- b. Ceramic and crystal
- c. Diaphragm and generating element
- d. Wired and body
318. A cause for ghost and smears
- a. Multipath reception
- b. Open transmission line
- c. Improperly positioned antenna
- d. All of these
319. An FM broadcast station with an ERP of not more than 35 kW.
- a. Clear channel
- b. Class A
- c. Class B
- d. Regional Channel
320. In television-receiver, the alignment of all these colors guns to a common point is referred to as _____.
- a. Confetti
- b. Convergence
- c. Demodulation
- d. blooming
321. It is a form of digital modulation where the digital information is contained in both the amplitude and phase of the transmitted carrier.
- a. QAM
- b. FSK
- c. PCM
- d. PSK
322. An error detection scheme that uses parity to determine if transmission error has occurred in a message.
- a. CRC
- b. VRC
- c. HRC
- d. All of the above
323. Synchronization modem usually contains a
- a. Scrambler
- b. Descrambler
- c. Adaptive equalizers
- d. All of the above
324. For a standard voice band communications channel with a S/N of 30 dB and a bandwidth of 2.7 kHz, the Shannon limit for information capacity is _______.
- a. 8.1 kbps
- b. 12.4 kbps
- c. 4.03 kbps
- d. 26.9 kbps
325. A T3 carrier time division multiplexes _______ PCM-encoded voice channels.
- a. 692
- b. 672
- c. 96
- d. 4032
326. In this mode, a secondary station can not initiate transmission without first receiving permission from the primary station.
- a. NRM (Normal Response Mode)
- b. ARM (Asynchronous Response Mode)
- c. ABM (Asynchronous Balanced Mode)
- d. LAP (Link Access Protocol)
327. With bit-oriented protocol, a frame starts with a ______.
- a. Pad
- b. Start bit
- c. Flag
- d. header
328. The controller provides
- a. queueing
- b. line querying
- c. companding
- d. buffering
329. A radar equipment located near the runway designed to accurately locate an airplane with 300 ft. of range.
- a. ASR
- b. PAR
- c. ILS
- d. ARSR
330. A circuit in a radar used to allow an antenna to function as a transmitting and a receiving antenna.
- a. Diplexer
- b. Duplexer
- c. Combiner
- d. Matrix
331. Is an electronically steerable antenna.
- a. Yagi-Uda
- b. Log Periodic
- c. Phased Array
- d. None of these
332. The ratio of the focal length to the mouth diameter of the parabola is called _______.
- a. Aperture Number
- b. Aperture diameter
- c. Effective area
- d. Aperture
333. Is an array antenna which has its maximum main beam directed along the axis of the array.
- a. Antenna array
- b. End-fire array
- c. Broadside array
- d. None of these
334. The dish antenna is operating at 10 GHz frequency. What is the directivity if the reflector is 5m at 65% efficiency?
- a. 18.703 dB
- b. 42.67 dB
- c. 13.6 dB
- d. 12.2 dB
335. It uses a hyperboloid secondary reflector.
- a. Double reflector
- b. Waveguide feed horn
- c. Feed horn
- d. Cassegrain feed
336. When a waveguide is terminated by a horn, it is called ______.
- a. Feed antennas
- b. Horn antennas
- c. Feed horn
- d. None of these
337. Radio waves are collected by the large bottom surface which is a slightly curved and are reflected upward at an angle of 45o, upon hitting the top surface which is large hyperbolic cylinder, they are reflected downward to the focal point and collected by the conical horn placed at the focus.
- a. Horn antennas
- b. Helical antennas
- c. Discone antennas
- d. Cass-horn antennas
338. Calculate the effective length of an antenna which has directive gain over an isotropic antenna of 17 dB and a radiation resistance of 350 ohms at a frequency of 144 MHz.
- a. 8 m
- b. 10 m
- c. 5 m
- d. 7 m
339. Calculate the angular aperture for a paraboloid reflector antennas for which the aperture number 0.48.
- a. 37o
- b. 55o
- c. 65o
- d. 28o
340. Is made up of one or more turns of wire on a frame which may be rectangular or circular, and is very much smaller than one wavelength across.
- a. Circular antennas
- b. Helical antennas
- c. Loop antennas
- d. None of these
341. Is the radio-frequency current on the antenna with no modulation.
- a. Carrier current
- b. Antenna current
- c. Current
- d. None of these
342. Channels for FM broadcast station begin at ____ MHz and continue is successive steps of 200 kHz to and including 107.9 MHz
- a. 89.1
- b. 88.1
- c. 89.9
- d. None of these
343. The carrier which is modulated by the chrominance information.
- a. Carrier frequency
- b. IF frequency
- c. Chrominance subcarrier
- d. Color burst
344. The transmission of television signal which can be reproduced is gradations of a single color only.
- a. Monochrome transmission
- b. Negative transmission
- c. Color transmission
- d. Video transmission
345. The carrier frequency allocated by the authority.
- a. Frequency swing
- b. High frequency
- c. Center frequency
- d. IF frequency
346. Serving as a control signal for use in the reception of FM stereophonic broadcast.
- a. IF frequency
- b. Pilot sub-carrier
- c. RF frequency
- d. Carrier frequency
347. The peak difference between the instantaneous frequency of the modulated wave and carrier frequency.
- a. Modulated index
- b. Frequency deviation
- c. Modulating frequency
- d. Percentage modulation
348. AM Broadcast station licensed for aural or _____ transmission intended for direct reception by the general public and operated on a channel in the medium frequency band.
- a. Video
- b. Carrier
- c. Sound
- d. Power
349. Is necessary to bring the main vertical beam tangential to the earth, which is curving away from it.
- a. Radio horizon
- b. Take off angle
- c. Money
- d. Beam tilt
350. In Metro Manila and Metro Cebu, the maximum effective radiated power of 350 kW for channel 2 - 6 and ____ kW for channel 7 – 13 are allowed.
- a. 1,000
- b. 5000
- c. 500
- d. 250
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