Communications Engineering Coaching Materials: Section 3 Module 1

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(Last Updated On: December 8, 2017)

Communications Coaching Materials: Section 3 Module 1

This is the Section 3 Module 1 of the compiled Communications Coaching Materials taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies (EST), Communications Books, Journals and other Communications References. This particular Coaching Notes in Communications Engineering has random Questions and Answers in random topics. Make sure to familiarize each questions to increase the chance of passing the ECE Board Exam.

Communications Engineering Coaching: Section 3 Module 1

· ISDN basic rate

Ans: 2B + 2D

· Access B data rate

Ans: 64 kbps

· Maximum diameter of fiber

Ans: rmax = 0.383λ/NA

· V number

Ans: V = πdNA/λo

· Neutralization is

Ans: Elimination of RF signals

· An IC of differential amplifier and on-chip

Ans: NE602

· Distance of microwave repeater of fiber optic

Ans: 6.215 – 18.65 mi

· IF up and down converter

Ans: 70 MHz

· Height of GLONASS

Ans: 19100 km

· Accuracy of GPS

Ans: 2 nautical miles

· Phase shift

Ans: β = √(ωδu/2)

· Negative transmission, medium gray

Ans: 40%

· Negative transmission, tip of sync

Ans: 100%

· Negative transmission, blanking level

Ans: 75%

· Negative transmission, black

Ans: 67.5%

· Negative transmission, maximum white

Ans: 12.5%

· Time for horizontal retrace

Ans: 10.2 us

· Path of telephone line crossing a private property and entering a building

Ans: Service entrance

· Cable within a building of series of buildings

Ans: Building cable

· Circular passage of cable

Ans: Pipe sleeve

· Marine radar communications

Ans: X-band

· Civil aircraft

Ans: 30-100 MHz

· Aircraft long range communications

Ans: 2 – 30 MHz

· Wireless telegraph

Ans: 1895

· Telegraph

Ans: 1844

· Telephone

Ans: 1876

· Radio

Ans: 1887

· Average splice of fiber optic

Ans: 0.15 dB

· Pilot subcarrier frequency

Ans: 19 kHz

· A subcarrier set by music

Ans: 67 kHz

· Travelling wave antenna

Ans: Rhombic antenna

· Brightness or illumination

Ans: contrast

· Amplitude of the signal

Ans: Contrast

· Out of control

Ans: Singing

· Frequency above 300 GHz

Ans: millimeter waves

· Micrwave operates

Ans: above 1 GHz

· Emits heat energy

Ans: Infrared

· A regulatory body whose sole purpose is allocating spectrum space, issuing licenses, setting standards and policing the airwaves.

Ans: FCC

· Government and military communications are coordinated by ___


· The electromagnetic spectrum is managed by

Ans: ITU

· Characteristic impedance of coaxial cable

Ans: 75 Ω

· TDM used

Ans: PCM

· Telemetry data

Ans: PCM

· Frequency difference of color subcarrier and sound

Ans: 0.92 MHz

· Chroma signal

Ans: 3.58 MHz

· LORAN C frequency

Ans: 100 kHz

· Which cannot be used for range and bearing?


· Ceramic resonator at frequency of 200 – 500 kHz

Ans: Ceramic filter

· Multiple resonant disk

Ans: Mechanical bandpass filter

· Doubley balanced modulators and GaAs filters are best mixers for

Ans: VHF, UHF and microwave

· Layer of ionosphere for nighttime communications

Ans: F layer

· Which of the following is true?

Ans: Negative polarity has an amplitude decreases when white.

· Third letter

Ans: Type of information to be transmitted

· Lock range

Ans: PLL

· Critical part of FM receiver

Ans: Front end

· Advantage of superheterodyne receiver

Ans: excellent sensitivity and stability

· Disadvantage of TRF

Ans: Tuning and selectivity

· Ch.4 downlink frequency

Ans: 3.84 MHz

· λ/4 vertical λ/4 spaced and 90 degrees out of phase

Ans: Unidirectional Cardioid

· Discone antenna uses

Ans: Vertical polarization

· No gain antenna

Ans: Isotropic

· Token passing

Ans: IEEE 804.2

· PLL consists of

Ans: FM synthesizer and FM demodulator

· Simplest AM receiver

Ans: TRF

· MF range

Ans: 300 kHz- 3 MHz

· 1 pixel

Ans: 0.125 us

· Folded dipole is ____ the feedpoint of a dipole.

Ans: 4

· Resonant frequency tuned to the resonant circuit tuned to the multiple input of the signal

Ans: Frequency multiplier

· Time constant for pre-emphasis and de-emphasis network

Ans: 75 us

· To compress voice signal dynamic range

Ans: Companding

· Amplifier for PCM

Ans: Sample and Hold circuit

· Cut off

Ans: Class B

· 90 degrees to 150 degrees

Ans: Class C

· Benefits of multiplexing

Ans: Economy

· TV picture tube

Ans: kinescope

· Phase angle in TV

Ans: hue

· Linear amplifier

Ans: Class A

· Transmission range

Ans: TR = (2h)/(tan β)

· Frequency of reverberation chamber

Ans: f = 125 3√(180/V)

· Advantage of FM over AM

Ans: Noise immunity

· Disadvantage of FM

Ans: Wider bandwidth

· Floor area within a building that is usable and rentable

Ans: Rentable Floor Area

· Code for touch tone dialing

Ans: two-to-seven

· Increasing the amplitude level of higher frequency on modulating frequency

Ans: Pre-emphasis network

· Cable that is entering the building

Ans: Entrance Cable

· Comprises of telephone equipment; transmitter/receiver, etc.

Ans: Station.

· A telephone line that do not serve exchange

Ans: Private Line

· It is used to connect private branch exchange and central office

Ans: Trunk Line

· Most widely used fiber optic cable

Ans: Single mode step index.

· Most widely used RF transformer

Ans: Toroid

· Advantages of toroidal core

Ans: Fewer turns, Higher Q, and no shielding

· Refers to the general (whole) telephone company that serves communications

Ans: Plant

· It is used to increase the power level of AM and other sidebands

Ans: Class A or B

· It does not affect by the RF carrier

Ans: Phase modulated emission

· Time required for the horizontal scanning line

Ans: 63.6 us

· It must be on during horizontal flyback time

Ans: Burst separator

· Controls the phase angle of modulated color signal in TV

Ans: Tint

· Non-resonant antenna

Ans: V-antenna

· Information on altitude, etc. of an aircraft

Ans: Air data

· End line of communication

Ans: Station wiring

· Holds wires, they are conduits

Ans: Raceway

· It contains PBX

Ans: Equipment room

· Line of sight frequency

Ans: VHF and UHF

· An antenna used for VHF and higher frequency

Ans: Omnidirectional antenna

· Frequency conversion and translation

Ans: Heterodyning

· Cable connected to a cross connect terminal and not directly connected to the local exchange

Ans: Home cable

· Maximum propagation delay of GEO

Ans: 278 us

· Velocity factor of open-wire line

Ans: 0.9

· Velecoity factor of coaxial line

Ans: 0.8

· Most widely used modulator

Ans: Balanced modulator

· Multielement system for control

Ans: Key system

· Narrowband still picture

Ans: Slow scan TV

· Average power emitted by laser

Ans: pulse energy x repetition rate

· PCM system used in telephone network and uses TDM technique

Ans: Bell T1

· Sampling interval of T1 system

Ans: 25 us

· Widely used TV modulator

Ans: Quadrature detector

· Cut-off audio output to prevent annoying noise

Ans: Squelch

· Permits selective signaling

Ans: CTCS – continuous tone control squelch

· Cut-off frequency of pre-emphasis and de-emphasis network

Ans: 2122 Hz

· Feedback system used to correct the frequency drift of VHF, UHF and microwave frequency receivers

Ans: AFC (automatic frequency control)

· Produces excellent deviation FM for frequencies below 1 MHz


· Period of visible H

Ans: 12.5 us

· Period of equalizing pulse

Ans: 2.29 us

· Delay of geosynchronous satellite

Ans: 278 us

· A VCO in which frequency is varied in proportion to the amplitude of modulating DC or AC signal

Ans: Subcarrier oscillator

· All plants which are “out of doors” not inside the building

Ans: Outside plant

· All plants located inside the telephone public exchange building

Ans: Inside plant

· Used to terminate telephone wire cable

Ans: Distrubution frame

· It is used to terminate floor distribution cable

Ans: Floor Distribution Terminal

· Portion of a floor service by the floor distribution terminal

Ans: Floor terminal distribution area

· Branch cable of various floor used to connect floor distribution terminal to the riser cable

Ans: Floor distribution cable

· Upstream signal frequency of two wire cable

Ans: 5- 30 MHz

· It is found at the BPA of the TV

Ans: color level control

· 2 main barrier of communications

Ans: language and distance

· Raceway of rectangular cross section

Ans: header or feeder duct

· Terminate cables of telephone services

Ans: Satellite closet

· Station to private exchange

Ans: Local station

· Amplitude demodulator

Ans: Diode detector

· Maximum FM deviation audio modulation for TV

Ans: 25 kHz

Complete List of Communications Engineering Coaching Materials

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