est qustion

Area of

Specialization

Biomedical Technology

QUESTION:

A mammography serv ice examined 327

patients during the third calendar quarter of

1996. 719 films were exposed during this

period, eight of which were repeats. What is

the repeat rate?

ANSWER:

c. 1.1%

SOLUTION ( IF PROBLEM -SOLVING)

QUESTION:

A type of luminescence where the visible

light is emitted only during the stimulation of

the phosphor.

ANSWER:

a. fluorescence

QUESTION:

If a heart measures 12.5 cm from side to

side at its widest point, and its image on

chest radiograph measures 14.7 cm, what is

the magnification factor?

ANSWER:

b. 1.18


QUESTION:

Radiation doses in the range of

approximately200 to 1000 rad produce the

ANSWER:

c. Hematologic syndrome

QUESTION:

Ratio of incident to transmitted radiation

through a grid ratio of patient dose with

and without grid

ANSWER:

a. Bucky factor

QUESTION:

A radiographic single-phase unit installed in

a priv ate office has a maximum capacity of

100 milliseconds of 120kVp and 500mA.

What is the power rating?

ANSWER:

a. 42 kW


( )

( ) ( )( )

QUESTION:

Who completes the dev elopment of first

computed tomographic (CT) scanner (EMI,

Ltd.) in 1973?

ANSWER:

a. Hounsfield

QUESTION:

It is the study of the response of an image

receptor to x-rays

ANSWER:

a. sensitometry

QUESTION:

Ratio of radiographic contrast with a grid to

that without a grid

ANSWER:

b. contrast improv ement factor

QUESTION:

Analysis of persons irradiated

therapeutically with superficial x-rays has

shown that the skin erythema dose required

to affect 50% of persons so irradiated is

about

ANSWER:

c. 600 rad

QUESTION:

ECG recording requires a bandwidth of 0.05

to ____ Hz

ANSWER:

c. 100

QUESTION:

Find the potential generated if blood

flowing in a v essel with radius 0.9 cm cuts a

magnetic field of 250 G. Assume a v olume

flow rate of 175 cubic cm per second.

ANSWER:

b. 309 uV


( )( )

( )

QUESTION:

Period during which heart contracts.

ANSWER:

b. Systole

QUESTION:

Apparatus for measuring blood pressure

ANSWER:

d. sphygmomanometer

QUESTION:

Giv en the energy level of 6.624x10^-18 J

imparted to an electron stream by an X-ray

dev ice, calculate the frequency in MHz.

ANSWER:

c. 10^10 MHz


10^10 MHz

QUESTION:

It was first noted by Heinrich Hertz in 1887

and won Albert Einstein the Nobel Prize in

1905. It refers to the emission of electrons

from a clean metallic surface (phototube)

when electromagnetic radiation (light

waves or X-rays) falls onto that surface.

ANSWER:

a. Photoelectric effect

QUESTION:

Unit of radiation exposure or amount of X-

ray radiation that will produce 2.08x10^9

ion pairs per cubic centimetre of air at

standard temperature and pressure (STP).

ANSWER:

b. Roentgen

QUESTION:

An optical electronic dev ice that measures

the color concentration of a substance in

solution.

ANSWER:

a. colorimeter

QUESTION:

Recording of heart sounds

ANSWER:

d. phonocardiography

QUESTION:

Recorder for measuring galv anic skin

resistance

ANSWER:

a. electrodermograph

Area of

Specialization

Digital and Data

Communications

QUESTION:

It consists of 36 unique codes representing

the 10 digits and 26 uppercase letters

ANSWER:

b. code 39

QUESTION:

The first fixed- length character code

dev eloped for machines rather than for

people

ANSWER:

d. Baudot Code

QUESTION:

The early pioneer in the dev elopment of

error-detection and correction procedures

ANSWER:

a. Richard W. Hamming

QUESTION:

The most reliable conv olutional coding

scheme for error detection

ANSWER:

c. CRC

QUESTION:

For the giv en parameters, determine the

energy per bit-to noise power density ratio

C = 10e-12 W

fb = 60 kbps

N = 1.2 x 10e-14`W

B = 120 kHz

ANSWER:

d. 22.2 dB


[

] ;

[

]

QUESTION:

A signal at the input to a mu-law

compressor is positiv e with its v oltage one-

half the maximum v alue. What proportion

of the maximum output voltage is

produced?

ANSWER:

b. 0.876Vmax


(

)

( )

(

( )( )

)

( )

QUESTION:

Inaccuracies caused by the representation

of a continuously varying quantity as one of

a number of discrete v alues.

ANSWER:

d. quantizing errors

QUESTION:

Circuit for digitizing v oice at a low data rate

by using knowledge of the way in which

v oice sounds are produced

ANSWER:

a. v ocoder

QUESTION:

A coding scheme that records the change

in signal lev el since the precious sample

ANSWER:

d. delta modulation

QUESTION:

Distortion created by using too low a

sampling rate when coding an analog

signal for digital transmission

ANSWER:

c. either a or b

QUESTION:

A network with bandwidth of 10 Mbps can

pass only an av erage of 12000 frames per

minute with each frame carrying an

av erage of 10000 bits. What is the

throughput of this network?

ANSWER:

b. 2 Mbps


= 2 Mbps

QUESTION:

A telephone subscriber line must have an

SNRdB above 40. What is the minimum

number of bits?

ANSWER:

c. 6.35


SNRdB = 6.02nb + 1.76 = 40

n = 6.35

QUESTION:

The thick coaxial cable implementation of

standard Ethernet

ANSWER:

d. 10 Base 5

QUESTION:

A bit pattern or a character added to the

beginning and the end of a frame to

separate the frames

ANSWER:

a. Flag

QUESTION:

An IPv 4 has an address space of how

many?

ANSWER:

a. 4294967296


232 = 4294967296

QUESTION:

What is the bit rate of STS – 1?

ANSWER:

a. 51.84 Mbps

QUESTION:

A block coding technique in which four bits

are encoded into a fiv e bit code

ANSWER:

c. 4B/5B Encoding

QUESTION:

A national standards organization that

defines standards in the United States

ANSWER:

a. ANSI

QUESTION:

In asynchronous transmission, one or more

bits to indicate the end of transmission

ANSWER:

d. stop bit

QUESTION:

What is the ov erhead (number of extra bits)

in the DS-3 serv ice?

ANSWER:

a. 1.368 Mbps

Area of

Specialization

EST

QUESTION:

The minimum sampling rate according to

Nyquist Theorem

ANSWER:

d twice the highest frequency of

a signal

QUESTION:

It is used in wireless applications in which

stations must be able to share the medium

without interception by an eav esdropper

and without being subject to jamming from

a malicious intruder

ANSWER:

d. spread spectrum

QUESTION:

An error detection method which uses

one’s complement arithmetic

ANSWER:

a. Checksum

QUESTION:

It is a connecting dev ice between two

internetworks that use different models

ANSWER

b. gateway

QUESTION:

It is an undesired shift or width change in

digital bits of data due to circuitry action

which causes bits to arriv e at different times

ANSWER:

c. jitter

QUESTION:

In PCM system, it is the ratio of the

maximum input voltage level to the smallest

v oltage lev el that can be quantized

ANSWER: a. Dynamic range

QUESTION:

A multiplexer combines four 100-kbps

channels using a time slot of 2 bits,

determine the frame duration.

ANSWER: a. 20s


The link carries 50,000 frames /sec

The frame duration = 1/50,000 =

20s

QUESTION:

Determine the Hamming distance for the

codewords ( 10101, 11001)

ANSWER:

b. two


10101 XOR 11001 = 01100 ( presence of two

1)

QUESTION:

An address space is the total number of

addresses used by the protocol, such as

IPv 4 and IPv6. What is the address space of

IPv 6?

ANSWER:

d. 2128

QUESTION:

It is a standard designed by ITU to allow

telephones in the public telephone

network to talk to computers/terminals

connected to the internet

ANSWER:

d. H.323

QUESTION:

A computer monitor has a resolution of 1200

by 1000 pixels. If each pixel uses 1024 colors,

how many bits are needed to send the

complete contents of a screen?

ANSWER:

d. 12 Megabits


1,200 times 1000 pixels x 10 bits = 12 Mb

1024 colors requires 10 bits , 210 = 1024

QUESTION:

Combination of compression at the

transmitter and expansion at the

receiv er of communications system.

ANSWER:

b. Companding

QUESTION:

A dev ice launches or receiv es a wave in a

transmission line or waveguide in one

direction only.

ANSWER:

b. directional coupler

QUESTION:

A type of linear-beam microwave tube that

uses v elocity modulation of the electron

beam

ANSWER:

d. klystron

QUESTION:

A series of pulses in which the amplitude of

each pulse represents the amplitude of the

information signal at a giv en time.

ANSWER:

a. PAM

QUESTION: Combination of

compression at the transmitter and

expansion at the receiver of

communications system.

ANSWER:

b. Companding

QUESTION: A dev ice launches or receiv es a

wave in a transmission line or waveguide in

one direction only.

ANSWER:

b. directional coupler

QUESTION: A type of linear-beam

microwave tube that uses velocity

modulation of the electron beam

ANSWER:

d. klystron

QUESTION:

_______________ is used to position samples

of the different message signals in non-

ov erlapping time slots.

ANSWER:

b. TDM

QUESTION:

A ___________ is similar to a phasor diagram

except that the entire phasor is not drawn.

ANSWER:

b. constellation diagram

QUESTION:

It was the first fixed length character code.

ANSWER:

b. Baudot Code

QUESTION:

It inv olves transmitting each character

twice.

ANSWER:

b. Redundancy

QUESTION:

The __________ provides the mathematical

justification for using a Gaussian Process as

a model for a large number of different

physical phenomena in which the random

v ariable, at a particular instant of time, is

the result of a large number of indiv idual

random ev ents.

ANSWER:

b. Central Limit Theorem

QUESTION:

A set of communication facilities allowing

direct access to 64kpbs data streams (or

multiples of) for drop and insert. A form of

cell relay, supports B-ISDN.

ANSWER:

c. Asynchronous transfer mode (ATM)

QUESTION:

A series of pulses, in which the timing of

each pulse represents the ampltitude of the

information signal at a giv en time.

ANSWER:

d. Pulse Position Modulation

QUESTION:

A line of sight radio link operating at a

frequency of 6GHz has a separation of

40km between antennas. An obstacle in

the path is located 10km form the

transmitting antenna. By how much must

the beam clear the obstacle?

ANSWER:

a.11.6m

`SOLUTION ( IF PROBLEM -SOLVING)

√

( )

√

( )

R = 11.6m

QUESTION:

Variation in receiv ed field strength ov er

time due to changes in propagation

conditions.

ANSWER:

b. Fading

QUESTION:

The atomic weight of an element is

approximately determined by

ANSWER:

C. the number of protons and neutrons

QUESTION:

Of the following substances the most

conductor is

Choices:

a. air b copper

c. iron d. salt water

ANSWER:

A

QUESTION:

The v olt is the standard unit of

Choices:

a. currrent b. charge

c. electromotiv e force d. resistance

ANSWER:

C

QUESTION:

Which of the following antenna types is not

designed for transmitting at 10 Ghz

Choices:

a. horn antenna b dish antenna

c. Zepp antenna d. helical antenna

ANSWER:

C

QUESTION:

The type of radio wave responsible for long

distance communications by multiple skips

is the:

ANSWER:

b. Direct Wave

QUESTION:

Line of sight communications is not a factor

in which frequency range?

Choices:

a. VHF b. UHF c. HF d. Microwave

ANSWER:

c. HF

QUESTION:

It refers to the rate of change of a signal on

the transmission medium after encoding

and modulation have occurred.

ANSWER:

b. Baud

QUESTION:

It was the first fixed-length character code

dev eloped for machines rather than

people.

ANSWER:

b. Baudot Code

QUESTION:

A receiv er-transmitter station used to

increase the communications range of VHF,

UHF and microwave signals is called a(n):

ANSWER:

C. Repeater

QUESTION:

It represents the simplest whole number

ratio of the v arious types of atoms in a

compound.

Choices:

a. molecular formula

b. chemical formula

c. reactants

d. empirical formula

ANSWER:

D

QUESTION:

It is a term that is often misunderstood and

commonly confused with bit rate (bps)

Choices:

a. Bandwidth b ASK

c. Baud d. FSK

ANSWER:

C

QUESTION:

Defined as the optimum lev el of a test tone

on a channel at same point in a

communication system.

Choices:

a. transmission lev el point

b. transmission lev el

c. data level point

d. error detecion

ANSWER:

A

QUESTION:

Duplicating each data unit for the purpose

of detecting errors is a form of error

detection called ___________.

Choices:

a. burst b. redundancy

c. error correction d. error detection

ANSWER:

B

QUESTION:

Determine the wavelength of a 4 Ghz

signal.

ANSWER:

d. 0.075m

QUESTION:

What is the dev ice that converts energy

from one form to another?

ANSWER:

a. transducer

QUESTION:

It may be defined as any undesired

v oltages or currents that ultimately end up

appearing in the receiv er output.

ANSWER:

b. Electrical noise

QUESTION:

The channel capacity of a 5 kHz

bandwidth binary system is ____ bits/s.

Assuming no noise.

ANSWER:

c. 10,000

QUESTION:

Microwaves are frequencies above _____

GHz.

ANSWER:

c.1

QUESTION:

The gov ernment agencies that regulates

radio communications in the US is the

________.

ANSWER:

b. FCC

QUESTION:

A wave guide acts a/an _______ filter

ANSWER:

a. High-pass

QUESTION:

Coax is not used beyond frequencies of

about ______ GHz.

ANSWER:

a. 6

QUESTION:

Data Communications refers to the

transmission of ________.

ANSWER:

d. all of the above

Question:

Determine the peak frequency deviation

for a binary FSK signal with a mark

frequency of 49 kHz, space frequency of

51kHz and an input bit rate of 2kbps

ANSWER:

a. 1 kHz


|

|

|

|

QUESTION:

It is often used to compare the

performance of one digital modulation

technique to another.

ANSWER:

a. bandwidth efficiency

QUESTION:

It is the process of conv erting an infinite

number of possibilities to a finite number of

conditions.

ANSWER:

a. quantization

QUESTION:

For a PCM system with a maximum analog

frequency of 4kHz, determine the minimum

sample rate.

ANSWER:

a. 8 kHz

SOLUTION ( IF PROBLEM-SOLVING)

( )

QUESTION:

It is another relatively simple form of

redundancy error checking where each

character has a numerical value assigned

to it.

ANSWER:

a. Checksum

QUESTION:

It is a modulation and multiplexing

technique that distributes the signal and its

sidebands over a very wide bandwidth.

ANSWER:

a. Spread spectrum

QUESTION:

The computers that hold shared files,

programs and the network operating

system. They also prov ide access to network

resources to all the users of the network.

ANSWER:

a. Serv ers

QUESTION:

It is defined by the ITU-T as a service that

prov ides transmission channels capable of

supporting transmission rates greater than

the primary data rate.

ANSWER:

a. Broadband ISDN

QUESTION:

It is the only error-correction scheme that

actually detects and corrects transmission

errors when they are receiv ed without

requiring a transmission..

ANSWER:

a. Forward Error Correction

QUESTION:

This OSI Layer is responsible for network

av ailability, data storage and processor

capacity. It also determines the type of

dialogue av ailable.

ANSWER:

a. Session layer

QUESTION: What do you call the accumulation

of additional sounds such as wind, street noise,

other v oices that contribute to what the listener

hear?

ANSWER: b. Ambience

QUESTION:

It is a single transmission path from transmitter to

receiv er with line of sight range.

ANSWER:

D. hop

QUESTION:

It is defined by the av erage rate at which

energy is carried out per unit area.

ANSWER:

b. intensity

QUESTION: Also known as Pin 21 of the RS-232

interface on D connector, this connection

allows signals to be transmitted from the DCE to

the attached DTE whenever there is a high

probability of an error in the receiv ed data due

to the quality of the circuit falling below a

predefined lev el.

ANSWER:

c. signal quality detector

QUESTION: It is the electrostatic forces of

attraction between oppositely charged ions.

ANSWER:

A. ionic bonding

QUESTION: What is the process in which the

system adapts to the incoming audio level to

keep the signal large enough to fill the systems

dynamic range?

QUESTION:

______ which means that 2 or more bits in the

data unit have changed.?

ANSWER:

C) burst error

QUESTION:

It is a four-wire Gigabit Ethernet

implementation.

ANSWER:

c. 1000 Base-T

QUESTION:

It is a digital process that allows several

connections to share the high bandwidth of a

link.

ANSWER:

a. TDM

QUESTION:

IEEE 802.11 is define in which MAC sublayer?

ANSWER:

d. (b) and (c)

QUESTION:

It is the oldest microwav e tube design which is

commonly used in radar transmitters where

they can generate peak power levels in the

megawatt range.

ANSWER:

b. Magnetron

QUESTION:

A modulation process wherein both frequency

and phase remains constant while the

amplitude changes.

ANSWER:

b. ASK

QUESTION:

It is the most powerful redundancy checking

technique which is based on binary division.

ANSWER:

c. cyclic redundancy check

QUESTION:

What do you call the element with electrical

properties between those of an insulator and a

conductor?

ANSWER:

a. Semiconductor

QUESTION:

It is the term applied to any method of

extinguishing a debt, principal and interest, by

a series of payments, usually at equal intervals.

ANSWER:

a. amortization

QUESTION:

In pulse-code modulation, it translates the

quantized samples into digital code words.

ANSWER:

c. encoder

QUESTION:

It is an error detection technique in which a

redundant bit is appended to ev ery data

unit so that the total number of 1s in the unit

(including the parity bit) becomes ev en.

ANSWER:

a. v ertical redundancy check

QUESTION:

A local area network topology in which the

indiv idual terminal, microcomputers or

workstations are connected directly to a

central computer.

ANSWER:

a. Star

QUESTION:

The only way to achieve high data rates

with a narrowband channel is to increase

the number of bits per symbol, the most

reliable way to do this is to use a

combination of amplitude and phase

modulation known as _________.

ANSWER:

a. quadrature amplitude modulation

QUESTION:

Find the maximum dynamic range for a

linear PCM system using 16-bit quantizing.

ANSWER:

d. 98.08 dB


DR = 1.76 + 6.02m; dB

DR = 1.76 + 6.02(16)

DR = 98.08 dB

QUESTION:

Compute the baud rate for a 72000 bps 64-

QAM signal.

ANSWER:

a. 12000 baud


A 64-QAM signal means that there are 6 bits

per signal element since 26 = 64.

Therefore, baud rate = 72000/6

baud rate = 12000 baud

QUESTION:

A telephone signal takes 2ms to reach its

destination. Calculate the via net loss

required for an acceptable amount of

echo.

ANSWER:

d. 0.8 dB


VNL = 0.2t + 0.4dB

VNL = 0.2 (2ms) + 0.4 dB

VNL = 0.8 dB

QUESTION:

Telephone switch that connects only to

other switches, and not to individual

customers.

ANSWER:

c. tandem office

QUESTION:

It is a form of digital modulation similar to

PSK except the digital information is

contained in both amplitude and the

phase of the transmitted carrier.

ANSWER:

c. QAM

QUESTION:

The most common circuit used for

demodulating binary FSK signals.

ANSWER:

b. PLL

QUESTION:

We hav e an audio signal with a bandwidth of

4KHz.What is the bandwidth needed if we

modulate the signal using AM? Ignore FCC

regulations for now.

ANSWER:

a. 8 KHz

SOLUTION (IF PROBLEM – SOLVING)

BW = 2 x 4 KHz

= 8 KHz

QUESTION:

We hav e an audio signal with a bandwidth

of 4 MHz. what is the bandwidth if we

modulate the signal using FM? Ignore FCC

regulations.

Choices:

a. 8 b. 6

c. 36 d. 40

ANSWER:

D


An FM signal requires 10 times the

bandwidth of the original signal.

BW=10x4

= 40 MHz

QUESTION:

We hav e an audio signal with a bandwidth

of 4 MHz. what is the bandwidth if we

modulate the signal using FM? Ignore FCC

regulations.

ANSWER:

D.40


An FM signal requires 10 times the

bandwidth of the original signal.

BW=10x4 = 40 MHz

QUESTION:

For PCM system with the following

parameters determine the minimum

number of bits used.

Maximum analog frequency= 4 khz,

maximum decoded voltage=±2.55,

Minimum dynamic range= 199.5

ANSWER:

C.8


( )

= 7.63

= 8

QUESTION:

A network topology in which data

circulates from one computer to the next in

sequence.

ANSWER:

a. ring

QUESTION:

Find the maximum dynamic range for linear

PCM system using 8-bit quantizing

ANSWER:

c. 49.92 dB


DR = 1.76 + 6.02(m)

DR = 1.76 + 6.02(8)

QUESTION:

What frequencies would be generated by

a telephone using DTMF signalling, when

the number 8 is pressed?

ANSWER:

c. 852 Hz and 1336 Hz

QUESTION:

It is a means of transmitting data by shifting

the phase angle of the transmitted signal.

ANSWER:

b. PSK

QUESTION:

The name giv en for a set of standards for

communicating among computers in which

the primary purpose is to serv e as a

structural guideline for exchanging

information between computers,

workstations and networks.

ANSWER:

a. OSI

QUESTION:

Any transmission system which conv eys

more than one signal simultaneously can

experience this type of interference due to

the reception of portions of a signal from

one channel in another channel.

ANSWER:

c. Crosstalk

QUESTION:

What type of digital modulation scheme

uses two or more different output

frequencies?

ANSWER:

b. FSK

QUESTION:

It is an error-correcting code used for

correcting transmission errors in synchronous

data streams.

ANSWER:

a. Hamming Code

QUESTION:

A suite of protocols that allows a wide

v ariety of computers to share the same

network.

ANSWER:

a. TCP/IP

Noise that is primarily caused by lightning.

Often called as Static Noise.

ANSWER:

c. atmospheric noise

A modulation technique in which the

frequency of the modulated signal varies

with the amplitude of the modulating signal

ANSWER:

a. AM

QUESTION:

Is a form of constant –amplitude angle

modulation similar to standard frequency

modulation except the modulating signal is

a binary signal that v aries between two

discrete v oltage levels rather than a

continuously changing analog waveform.

ANSWER:

b. FSK

QUESTION:

The highest layer in the hierarchy and is

analogous to the general manager of the

network by prov iding access to the OSI

env ironment.

ANSWER:

a. Application layer

QUESTION:

What is the equation for Hartley’s Law?

Choices:

a. I=ktB b. C=2Blog2M

c. fa=fs-fm d. N=2^m

ANSWER:

a.

QUESTION:

Network topology wherein individual

terminals, microcomputers and workstations

are connected directly to a central

computer.

ANSWER:

d. star

QUESTION:

The loss of data that occurs when two

stations transmit at the same time on a

network

ANSWER:

c.collision

QUESTION:

A term used to describe a telephone

instrument whose handset is on its cradle,

ready to receiv e a ring signal

ANSWER:

a. On hook

QUESTION:

The most commonly used digital

modulation scheme.

ANSWER:

d. PCM

QUESTION:

Simple form of redundancy error checking

where each character has a numerical

v alue assigned to it. The characters within a

message are combined together to

produce an error checking character.

ANSWER:

c. Checksum

QUESTION:

Is an eight-bit fixed length character set

dev eloped in 1962 by the International

Business Machines Corporation.

ANSWER:

c. EBCDIC code

QUESTION:

The most commonly used digital

modulation scheme.

ANSWER:

d. PCM

QUESTION:

An attempt is made to transmit base band

frequency of 30khz using a digital audio

system with a sampling rate of 44.1khz.

What audible frequency would result?

ANSWER:

A.14.1kHz


fa = fs – fm

= 44.1KHz – 30KHz

= 14.1 KHz

QUESTION:

Calculate the capacity of a telephone

channel that has a S/N of 1023?

ANSWER:

B.30000 b/s


The telephone channel has a bandwidth of

about 3KHz

C= BW log2 (1+ S/N)

= 3 x 103 log2 (1+ 1023)

=30000 b/s

QUESTION:

Designed to send characters of the

message with the specified bit rate but

without any fixed timing relationship from

one character to the next.

ANSWER:

A.asynchronous

QUESTION:

Token Ring Standard

ANSWER:

d. 802.5

QUESTION:

It is the process of extracting a phase-

coherent reference carrier from a receiv er

signal.

ANSWER:

a. Carrier Recov ery

QUESTION:

It is a potential problem whenever two

metallic conductors carrying different

signals are located in close proximity to

each other.

ANSWER:

c. Crosstalk

QUESTION:

What is the termed refer as the rapid

degradation of output signal quality with

channel induced errors?

ANSWER:

a threshold effect

QUESTION:

What was the first fixed-length character

code dev eloped for machines rather than

for people?

ANSWER:

d. Baudot code

QUESTION:

A source whose output satisfies the

condition of statistical independence

among letters in the sequence is said to

be_____.

ANSWER:

a. Memoryless

QUESTION: Calculate the minimum data

rate needed to transmit audio with

sampling rate of 30 Khz and 14 bits per

sample.

ANSWER:

420 Kb/s


D = fsm

= 30 x

103 x 14

= 420 x

103 b/s

= 420

Kb/s

QUESTION: Handles error recov ery, flow

control (synchronization), and sequencing

(which terminals are sending and which are

receiv ing). It is considered the “media

access control layer”.

ANSWER:

Data Link Layer

QUESTION: A MAC protocol for LANs, with

stations connected topologically or

logically in a ring. Or the IEEE 802.5 LAN

standard.

ANSWER:

Token Ring

QUESTION:

A network topology where each device is

connected to a centre point and all data is

routed through that point.

ANSWER:

c. Star network

QUESTION:

A lasers use organic dyes enclosed in a

glass tube for an active medium, dye is

circulated into the tube with a pump. A

powerful pulse of light excites the organic

dye.

ANSWER:

d. Liquid Lasers

QUESTION:

Codes that have a restriction on the

number of consecutive 1s or 0s in a

sequence.

ANSWER:

d. Run length limited code

QUESTION:

Contains sev en bytes (56 bits) of alternating

0s and 1s that alert the receiv ing system to

the coming frame and enable it to

synchronize its input timing

ANSWER:

b. preamble

QUESTION:

Ev ery letter was encoded into fixed length

of binary code words of length 5.

ANSWER:

b. Baudot Code

QUESTION:

The composite signal that modulates the FM

carrier.

ANSWER:

b. baseband

QUESTION:

It is a simple means of error detection. It

inv olves the addition of one extra bit to the

bits that encode a character.

ANSWER:

a. parity

QUESTION:

A data compression scheme that uses

fewer bits to represent more frequently

occurring characters or bit patterns and

more bits to represent those occur less

frequently.

ANSWER:

c. Huffman coding

QUESTION:

Speed at which symbols are transmitted in

a digital communication systems.

ANSWER:

b. Baud rate

QUESTION:

It is the process of conv erting an infinite

number of possibilities to a finite number of

conditions.

ANSWER:

d. Quantization

QUESTION:

It is the ratio of the largest possible

magnitude to the smallest possible

magnitude that can easily be decoded by

the digital to analog conv erter in the

receiv er.

ANSWER:

c. Dynamic Range

QUESTION:

It is the institution that developed the ASCII

(American Standard Code for Information

Intertchange).

ANSWER:

b. ANSI

QUESTION:

In early 1900s, he showed that any

composite signal is a sum of a set of sine

waves of different frequencies, phases and

amplitudes.

ANSWER:

c. Jean-Baptiste Fourier

QUESTION:

Find the binary equivalent of x8+x3+x+1.

Choices:

a. 100001011 b. 011110100 c. 010000101 d.

110000101

ANSWER:

a. 100001011


x8+x7+x6+x5+x4+x3+x2+x+k

1 0 0 0 0 1 0 1 1

QUESTION:

Giv en a bandwidth of 6000 Hz for an ASK

signal, what is the baud rate?

ANSWER:

d. 6000 Hz


baud rate = bandwidth

6000 Hz = 6000 Hz

QUESTION:

Compute the bit rate for a 2000 baud 16-

QAM signal.

ANSWER:

a. 8000 bps


bit rate = baud * 4

2000 * 4 = 8000 bps

QUESTION:

It is an electronic dev ice that is used for

computer communications through

telephone lines.

ANSWER:

b. modem

QUESTION:

A telephone line has a bandwidth of 4.5 kHz

and a signal-to-noise ratio of 40dB. A signal

is transmitted down this line using a four

lev el code. What is the maximum

theoretical data rate?

ANSWER:

b. 18 kbps


C = 2Blog2M = 2(4.5x103)log2(4) = 18 kbps

S/N = antilog (40/10) = 10000

C = Blog2(1+S/N) = (4.5x103)log2(1+10000) =

59.795 kbps

Since both results are maxima, we take the

lesser of the two, 18 Kbps...

QUESTION:

Showed mathematically that it is posssible

to reconstruct a band-limited analog signal

from periodic samples, as long as the

sampling rate is at least twice the

frequency of the highest frequency

component of the signal.

ANSWER:

c. Harry Nyquist

QUESTION:

Find the maximum dynamic range for a

linear PCM system using 8-bit quantizing.

ANSWER:

b. 49.92 dB


DR = 1.76 + 6.02m dB

= 1.76 + 6.02(8) dB

= 49.92 dB

QUESTION:

In operation, many modern codecs

achiev ed compresion by first encoding the

signals using a 12-bit linear PCM code, then

conv erting the 12-bit linear code into an 8-

bit compressed code by discarding some

of the bits. This is a simple example of:

ANSWER:

d. Digital Signal Processing

QUESTION:

Sampling of an analog signal using a

sample-and-hold circuit such that the

sample has the same amplitude for its

whole duration.

ANSWER:

a. Flat-topped Sampling

QUESTION:

The basic building block of the FDM

hierarchy.

ANSWER:

b. Message Channel

QUESTION:

The GSM radio system uses GMSK in a

200kHzchannel, with a channel data rate of

270.883 kbps. Calculate the frequency shift

between mark and space.

ANSWER:

a.135.42kHz


Fm-fs=0.5fb=0.5*270.833kHz=135.4165kHz

QUESTION:

For Ethernet system with a length of 2.5km

on coaxial cable with a velocity factor of

0.66. What is the propagation delay?

ANSWER:

a.12,6us


T=d/(VfC)=2.5km/(0.66*300000000m/s)=12.6

µs

QUESTION:

A signal at the input to a µ-Law compressor

is positiv e, with its v olatage one-half the

maximum v alue. What proportion of the

maximum output voltage is produced?

ANSWER:

A0.876Vo


Vo=Vo(ln(1+(255*0.5)))/ln(1+255)=0.876Vo

QUESTION:

A telephone signal take 2ms to reach its

destination. Calculate the via net loss

required for an acceptable amount of

echo

ANSWER:

a.0.8dB


VNL=0.2t+0.4=(0.2*2)+0.4=0.8

QUESTION:

Who inv ented the telegraph?

ANSWER:

b. Samuel F.B Morse

QUESTION:

The simplest modulation technique, where

a binary information signal modulates the

amplitude of an analog carrier.

ANSWER:

a. Amplitude-Shift Keying

QUESTION:

Is the lowest Open System Interconnection

hierarchy and is responsible for the actual

propagation of unstructured data bits (1s

and 0s) through a transmission medium.

ANSWER:

a. Physical Layer

QUESTION:

Error-correction scheme that actually

detect and corrects transmission errors

when they are receiv ed without requiring a

retransmission.

ANSWER: a. Forward Error Correction

QUESTION:

It allows the ov erall complexity of the

system to be broken down into individual

function –layers- that operate essentially by

themselv es.

ANSWER: b. Transparency

QUESTION:

This are v ery useful pictorial representations

that clearly show the protocol operations

such as words or conv etional drawings.

ANSWER:

a. State Transition Diagram

QUESTION:

Pair of wires that connects the central

office to the users phone

ANSWER:

a. Local loop

QUESTION:

How long does it take to dial the number

784-3745 using pulse dialing with .5s inter

digit time?

ANSWER:

a. 6.8s


0.7 + 0.8 + 0.4 + 0.3 + 0.7 + 0.4 + 0.5 (6x0.5) =

6.8s

QUESTION:

Network that connects users who are in the

same general location

ANSWER:

c. LAN

Please indicate the subject:

( ) General Engineering and Applied

Science

(/) Electronics System & Technologies

QUESTION:

In operation, many modern codecs

achiev ed compresion by first encoding the

signals using a 12-bit linear PCM code, then

conv erting the 12-bit linear code into an 8-

bit compressed code by discarding some

of the bits. This is a simple example of:

ANSWER:

d. Digital Signal Processing

QUESTION:

A balanced modulator that will used in

conjuction with a microwave generator,

power amplifier, and band-pass filter, up-

conv erts the IF carrier to an RF carrier and

amplifies the RF to the desired output

power.

ANSWER:

b. Transmit Modulator

QUESTION:

What is the equation for Hartley’s Law?

Choices:

a. I=ktB b. C=2Blog2M

c. fa=fs-fm d. N=2^m

ANSWER:

a.

ANSWER:

c.collision

QUESTION:

We hav e an audio signal with a bandwidth of 5

HHz. What is the bandwidth modulate the

signal using FM? Ignore FCC regulation.

ANSWER:

a. 50 MHz

QUESTION:

Used to established a point to point

connection across a network.

ANSWER: c. TCP

QUESTION:

An attempt is made to transmit a baseband

frequency of 25kHz using digital audio

system with a sampling rate of 44.1 kHz.

What audible frequency would result?

ANSWER: b. 19.1kHz


fa = fs - fm

= 44.1kHz – 25kHz

= 19.1kHz

QUESTION:

Defines the rules of the conv ersation the

message passing among the network users

ANSWER:

a. network protocol

QUESTION:

Responsible for prov iding signals to the loop

sensing activity and sending phone signals

at the end of the loop

ANSWER:

a. SLIC

QUESTION:

The typical amount of v oltage in dc use in

the battery of the central office with

respect to ground

ANSWER:

a. -48

QUESTION:

A network that is composed of a smaller lan

that are closely link. It is needed for areas

spread out geographically

ANSWER:

c. WAN

QUESTION:

How many central office allotted for each

exchange?

ANSWER:

b. 1

QUESTION:

It is a method of switching that provides a

separate physical path for each symbol

ANSWER:

c. space switching

QUESTION:

The central office detects a request for serv ice

from a telephone by:

ANSWER:

a. a flow of loop current

QUESTION:

The OSI Layer responsible for data tracking as it

mov es through a network. It controls and

ensures the end – to – end integrity of the data

message propagated through the network

between two devices.

ANSWER:

a. Transport

QUESTION:

The OSI Layer responsible for data tracking as it

mov es through a network. It controls and

ensures the end – to – end integrity of the data

message propagated through the network

between two devices.

ANSWER:

b. Transport

QUESTION:

It is used on long – distance circuits, in an effort

to ov ercome echoes caused by circuit

imbalances.

ANSWER:

a. Echo Suppresors

QUESTION:

The sensitiv ity of a radio receiv er is giv en in

terms of dBm. If the receiv er is receiv ing 200

mW, what is the corresponding dBm of this

signal?

ANSWER:

C. 23dBm


dBm for 200 mW = 10 log (200mW/1mW) =

23 dBm

QUESTION:

An antenna with a noise temperature of 75

Kelv in is connected to a receiv er input with

a noise temperature of 300 K. Giv en the

reference temperature T0 = 290 K, find the

noise figure of the system.

ANSWER:B


The total noise temperature of the antenna

and receiv er is NTtot = 75+ 300 = 375.

The noise temperature is giv en by:

10 NRTNT where:

NT – noise temp, NR = Noise ratio

Rearranging the above to find NR giv es:

NR = (375/290) +1 = 2.29

The Noise figure is the decibel equiv alent of

the noise ratio, such that:

NF = 10 log NR = 3.6 dB

QUESTION:The modulation index of an AM

radio station is 0.75. If the carrier power is

500W, what is the total transmitted power?

ANSWER:

C.641W


The modulation index m is related to the

total transmitted power Pt by:

21

2mPcPt where Pt =

total transmitted power, Pc = carrier power

QUESTION:An FM transmitter system is using

a 1MHz crystal oscillator to generate a v ery

stable 108MHz final carrier frequency. The

output of the crystal oscillator is fed to a x36

multiplier circuit then mixed with a 34.5 MHz

signal. The sum output of the mixer is filtered

out, while the difference is fed to another

multiplier in order to generate the final

carrier frequency. What is the multiplier

v alue?

ANSWER: D. 72


Basic Block Diagram of the FM carrier

generator:

1 MHz carrier > x 36 > Mixer > Multiplier >

108MHz carrier

First Multiplier output:

1MHz x 36 = 36 MHz

Mixer output:

36MHz + 34.5 MHz = 70.5MHz (filtered

output)

36MHz – 34.5 MHz = 1.5 MHz (difference

fed to the next multiplier)

Multiplier stage:

Output = 108MHz

Output = 1.5MHz x n

N = 108/1.5

= 72

QUESTION:

A/an _______ is a range of frequency in

which the upper frequency is double the

lower frequency.

ANSWER:

c. octave

UESTION:

Determine the worst-case output S/N for a

narrowband FM receiver with deviation

maximum of 10 kHz and a maximum

intelligence frequency of 3 kHz. The S/N

input is 3:1.

ANSWER:

a. 10


Φ = sin-1 (1/3) = 19.5 or 0.34 rad

δ = Φ x fi

= 0.34 x 3 kHz = 1 kHz

The S/N will be

10 kHz/ 1 kHz = 10

QUESTION:

A small v ariable capacitance in parallel

with each section of ganged capacitor is

called _______.

ANSWER:

a. trimmer

QUESTION: How many wavelengths long

are required for a pair of conductors to be

considered as a transmission line?

ANSWER:

c. 1/10λ

QUESTION: Determine the time taken for a

signal to trav el down a 10 m transmission

line, if its v elocity factor is 0.7.

ANSWER:

d. 47.6 ns


T= L/ (Vf x Vc)

T= 10 m/ (0.7)(3x108 m/s)

T= 47.6 ns

QUESTION: The maximum voltage standing

wave of an RG-11/U foam coaxial cable is

52 V and its minimum v oltage is 17 V. How

many percent of the incident power is the

reflected power?

ANSWER:

b. 26%


Г 2 = Pr/Pi

Г = SWR-1 ; SWR = Vmax/ Vmin = 52/17 =

3.05

SWR+1

Г = 3.05 – 1 = 0.51

3.05 +1

Thus : Г 2 = (0.51)2 = 0.26

The reflected power is 26 % of the incident

power

QUESTION: At exactly one-quarter

wavelength, the short-circuited transmission

line behaves as a(an) ___________ circuit.

ANSWER:

c. parallel-resonant

QUESTION: Determine the phase-shift

represented by a 75 ns delay of a 4 MHz

signal to a 75-ft cable with a dielectric

constant of 2.3.

ANSWER:

a. 108 degrees


Θ = 360 td / T

T =1/f = 1 / 4MHz = 250 ns

Θ = 360 (75) / 250 = 108 degrees

QUESTION: Which of the following is a flat

conductor separated by an insulating

dielectric from a large ground plane that is

usually one-quarter or one-half wavelength

long?

ANSWER:

b. microstrip

QUESTION: One complete revolution

around a Smith Chart represents _________

wavelengths.

ANSWER:

a. ½ λ

QUESTION: A mismatched transmission line

is also referred to as a ___________ line.

ANSWER:

d. resonant

QUESTION: It is the ratio of the speed of

propagation on a line to that of light in free-

space.

ANSWER:

a. v elocity factor

QUESTION: Which of the following is the

most widely used UTP cable that can carry

baseband data at rates up to 100 Mbps at

a range up to 100m?

ANSWER:

b. CAT 5

QUESTION: The modulated peak value of a

signal is 125V and the unmodulated

carrier v alue is 85V. What is the modulation

index?

ANSWER:

a.0.47


m = Em/ Ec

Emax = Ec + Em ; Em = Emax – Ec = 125 –

85 = 40 V

m = 40V/ 85V = 0.47

QUESTION: The total transmitted power of

an AM broadcast transmitter with a carrier

power of 50kW when modulated 80

percent is:

ANSWER:

c. 66kW


Pt = Pc ( 1 + m2/2)

Pt = 50,000 ( 1 + 0.82 /2)

Pt = 66,000 W

Pt = 66kW

QUESTION: One of the advantages of DSB is

the sav ings of great deal of power. Which

of the following is the reason why it is not

widely used?

ANSWER:

d. the signal is difficult to demodulate

QUESTION: If the input in a transmitter is

collector-modulated, the system is called a

_______________________.

ANSWER:

b. high-lev el modulator

QUESTION: The input to an FM receiv er has

a S/N of 2.8. What is the frequency

dev iation caused by the noise if the

modulating frequency is 1.5KHz and the

permitted deviation is 4KHz?

ANSWER:

b. 547.8 Hz


= fm

= sin -1 N/S = sin -1 1/2.8 = 0.3652

= (0.3652)(1.5KHz) = 547.8 Hz

QUESTION: What circuit is used to return the

frequency response of a signal to its normal,

“flat” lev el?

ANSWER:

b. de-emphasis

QUESTION: It is the most common means of

ov ercoming the problems of quantizing

error and noise.

ANSWER:

b. companding

QUESTION: ________________ means that the

characteristics and performance of an

antenna are the same whether the

antenna is radiating or intercepting an

electromagnetic signal.

ANSWER:

a. antenna reciprocity

QUESTION: Which of the following methods

is used to lower the resonant frequency of a

shortened v ertical antenna?

ANSWER:

b. top hat loading

QUESTION: It is a phenomenon caused by

any support insulators used at the ends of

the wire antenna.

ANSWER:

b. end effect

QUESTION: Which of the following is not a

reason why most half-wave antennas are

mounted horizontally at low frequencies?

Choices:

a. physical construction is easier

b. more cost-effectiv e

c. mounting is easier

d. support is easier

ANSWER: B

QUESTION: The shape of the

electromagnetic energy radiated from or

receiv ed by an antenna is called the

Choices:

a. signal shape

b. electromagnetic pattern

c. radiation pattern

d. antenna pattern

ANSWER: C

QUESTION: Antennas that transmit an equal

amount of energy in the horizontal direction

are called

ANSWER: c. omnidirectional

QUESTION: The ability of an antenna to send

or receiv e signals ov er a narrow horizontal

directional range is referred to as

Choices:

a. focal factor

b. permittiv ity

c. directiv ity

d. horizontal range

ANSWER: C

QUESTION: A basic antenna connected to

a transmission line plus one or more

additional conductors that are not

connected to the transmission line form a

ANSWER: a. parasitic array

QUESTION: An antenna made up of a

driv en element and one or more parasitic

elements is generally referred to as a

ANSWER:

d. Yagi antenna

QUESTION: Which antennas usually consist

of two or more half-wave dipoles mounted

end to end?

Choices:

a. Hertz

b. Marconi

d. Yagi

ANSWER: c. collinear

QUESTION: A stacked collinear antenna

consisting of half-wave dipoles spaced from

one another by one-half wavelengths is the

Choices:

a. broadside array

b. end-fire array

c. wide-bandwidth array

d. parasitic array

ANSWER: A

QUESTION: When the characteristic

impedance of the transmission line matches

the output impedance of the transmitter

and the impedance of the antenna itself,

ANSWER:

d. maximum power transfer will take place

QUESTION: A one-quarter wavelength of

coaxial or balanced transmission line of a

specific impedance connected between a

load and a source in order to match

impedances is

ANSWER:

c. a Q section

QUESTION:

By how much should two antennas be

separated for space diversity in the 11 GHz

band?

ANSWER:

A. 5.5 m


m

sx

s

mx

f

cd 5.5

1011

103200200

2009

8

QUESTION:

What is the phase v elocity of a rectangular

waveguide with a wall separation of 3 cm

and a desired frequency of operation of 6

GHz?

ANSWER:

D. 5.43 x 108 m/s


( )

√ ( )

√ (

)

QUESTION:

A transmitter and a receiver is 45 km apart.

Suppose that there is an obstacle midway

between the transmitter and receiver. By

how much must the path between the

towers clear the obstacle in order to av oid

diffraction at a frequency of 11 GHz?

ANSWER:

B. 10.51 m


√

√ ( )

( )

QUESTION:

How far from the transmitter could a signal

be receiv ed if the transmitting and

receiv ing antennas where 40 m and 20 m,

respectiv ely, above level terrain?

ANSWER:

A. 44.5 km


√ √ √ ( ) √ ( )

QUESTION:

A signal propagated in a waveguide has a

full wave of electric intensity change

between two further walls, and no

component of the electric field in the

direction of propagation. The mode is

ANSWER:

D. TE20

QUESTION:

An isolator has a forward loss of 0.7 dB and

a return loss of 26 dB. A source prov ides 1 W

to the isolator, and the load is resistiv e with

an SWR of 3. How much power is dissipated

in the load

ANSWER:

D. 638 mW


mWPP

SWR

SWR

mW

anti

WP

outLOAD

out

35.6381

5.01

1

14.851

10

7.0log

1

2

QUESTION:

An isolator has a forward loss of 0.7 dB and

a return loss of 26 dB. A source prov ides 1 W

to the isolator, and the load is resistiv e with

an SWR of 3. How much power returns to

the source?

ANSWER:

D. 5.43 x 108 m/s


W

anti

mWP

mWPP

mWPP

SWR

SWR

mW

anti

WP

returned

outreflected

outLOAD

out

49.534

10

26log

78.212

78.212

35.6381

5.01

1

14.851

10

7.0log

1

2

2

QUESTION:

It is a microwav e device that allows RF

energy to pass through in one direction with

v ery little loss, but absorbs RF power in the

opposite direction.

Choices:

a. multiplexer b. circulator c. isolator d.

wave trap

ANSWER:

C. isolator

QUESTION:

A metal wrapped around the parabolic

antenna aperture to eliminate sidelobes

interfering nearby stations is called

ANSWER:

C. shroud

QUESTION:

The wavelength of a wave in a waveguide

_________.

ANSWER:

A. is greater than in free space

QUESTION:

Geostationary satellites are located at ____

with respect to the equator.

ANSWER:

B. 00 latitude

QUESTION:

The quality of a space-link is measured in

terms of the ______ ratio.

ANSWER:

B. G/T

QUESTION:

Why does the downlink frequency appear

to v ary by several kHz during a low earth

orbit satellite pass?

ANSWER:

D. The distance between the satellite and

ground station is changing, causing the

Doppler effect

QUESTION:

The most ambitious LEO constellation to

date is ______.

ANSWER:

C. Teledesic

QUESTION:

A satellite-dish owner has a 3 meter dish

designed for C-band (4 GHz) operation. The

owner wants to use the same dish with a

new feedhorn, for Ku-band (12 GHz)

satellites. What effect will the change in

frequency have on the gain and

beamwidth of the antenna?

ANSWER:

A. Gain increases by 9.54 dB, beamwidth

decreases to 1/3 of its former v alue.

QUESTION:

The moon orbits the earth with a period of

approximately 28 days. How far away is it?

Assume circular orbit.

ANSWER:

c. 384 Mm


( )

√

( )

QUESTION:

What is the length of the path to a

geostationary satellite from an Earth station

if the angle of elev ation is 300?

ANSWER:

B. 39000 km


√( ) ( )

√( ) ( )

QUESTION:

What is the nominal uplink frequency for the

Ku band?

ANSWER:

C. 14 GHz

QUESTION:

To cov er all inhabited regions of the earth,

the number of polar-orbit satellites required

is

ANSWER:

A. 1

A dipole antenna has a radiation resistance

of 67 ohms and a loss resistance of 5 ohms,

measured at the feedpoint. Calculate the

efficiency.

ANSWER: d. 93%

SOLUTION:

Efficiency = Rr / Rt = 67 / (67 + 5) = 93%

Two antennas have gains of 5.3 dBi and 4.5

dBd, respectiv ely. Which has a greater

gain?

Choices:

a. The first antenna has a higher gain.

b. The second antenna has a higher gain.

c. Both antennas have the same gain

d. Cannot be determined

ANSWER: B

A half-wave dipole is sometimes called:

Choices:

a. Marconi antenna

b. Yagi antenna

c. Hertz antenna

d. none of the choices

ANSWER: C

An antenna's beamwidth is measured

Choices:

a. from +90° to –90°

b. between half-power points

c. from front to back

d. between the minor side-lobes

ANSWER: B

QUESTION: "Ground Effects" refers to the

effects on an antenna's radiation pattern

caused by

Choices:

a. radio signals reflecting off the ground

b. buildings and other structures on the

ground

c. fading

d. faulty connection of the feed cable

ground

ANSWER: A

QUESTION: An antenna can be matched to

a feed line using

Choices:

a. a shorted stub

b. an LC network

c. a loading coil

d. all of the choices

ANSWER: D

QUESTION: As the length of a "long-wire"

antenna is increased

Choices:

a. the number of lobes increases

b. efficiency decreases

c. the number of nodes decreases

d. none of the abov e

ANSWER: A

QUESTION: Field strength at a distance from

an antenna is measured with

ANSWER:

d. a field-strength meter

QUESTION: A receiv ing antenna with a built-

in preamplifier

Choices:

a. activ e antenna

b. passiv e antenna

c. coil

d. LC antenna

ANSWER: A

QUESTION:

The height above mean sea level of a

satellite in a geosynchronous orbit around

Earth is:

ANSWER:

d. 35,786 km

QUESTION:

The location of a satellite is generally

specified in terms of

ANSWER:

b. latitude & longitude

QUESTION:

A point in the orbit of an object orbiting the

earth that is located closest to Earth.

ANSWER:

a. perigee

QUESTION:

Find the v elocity of a satellite in a circular

orbit 500 km abov e the earth’s surface.

ANSWER:

c. 7.6 km/s


Formula :

v 4x1011

d 6400

Where : v = v elocity in meters per second

d = distance above earth’s

surface in km

v 4x1011

(500 6400)

= 7.6 km/s

QUESTION:

Find the orbital period of a satellite in a

circular orbit 36,000 km abov e the earth’s

surface if the earth’s radius is 6400 km.

ANSWER:

a. 1440 mins


Formula :

C

v

Where : T = orbital period

C = circumference

v = orbital v elocity

C = 2r

= 2 ( 6400 + 36,000 ) = 266.4 x 106

m

v 4x1011

(36,000 6400) 3.07km/s

T C

v266.4x106m

3.07x103m /s 24hrs or

1440 minutes

QUESTION:

The outline of a communications satellite

antenna pattern on the earth is known as:

ANSWER:

d. footprint

QUESTION:

Calculate the length of the path to a

geostationary satellite from an earth station

where the angle of elev ation is 30.

(earth’s radius = 6400 km, height of satellite

above earth is 36 X 103 km)

ANSWER:

c. 39,000 km


Formula :

d (r h)2 (rcos)2 rsin

d = distance to the satellite in

km

r = radius of the earth in km

(6400 km)

h = height of satellite above

equator ( 36 x 103 km)

= angle of elev ation to

satellite at antenna site

Solution :

d (6400 36x103)2 (6400cos30)2 6400sin30

= 39,000 km

QUESTION:

A satellite access technique where each

earth station transmits a short burst of

information during a specific time slot.

ANSWER:

c. TDMA ( Time Div ision Multiple Access)

QUESTION:

An earth station antenna look angle is

determined by :

ANSWER:

a. azimuth & elev ation

QUESTION:

An ITU radiocommunication standards for

satellite serv ices which provides information

on the range of frequencies that can be

used by fixed satellite serv ice systems for

emergency and disaster relief operations.

ANSWER:

c. ITU-R S.1001-2

QUESTION:

As per Philippine standard, frequency allocation of AM Radio Broadcasting is from…

ANSWER:

d. 526.5 to 1705 kHz

QUESTION:

Part of broadcasting in a day that refers to that period of time between 1000 UTC to 2200 UTC. UTC stands for Universal

Time Coordinates.

ANSWER:

b. nighttime period

QUESTION:

An AM broadcast service area in which groundwave field of 1mV/m (60dBu) is not subject to objectionable interference

or objectionable fading.

ANSWER:

a. primary serv ice area

QUESTION:

In antenna mast or tower construction, the required obstruction painting and/or lighting must be imposed on mast or

tower more than … from the ground lev el.

Choices:

a. 100 ft

b. 150 ft

c. 200 ft

d. 250 ft

QUESTION:

Regarding the design of AM antenna, what should be the polarization of the radiator?

ANSWER:

b. v ertical

QUESTION:

As per Phillipine standard, what is the minimum frequency separation in any service area for adjacent AM radio stations?

ANSWER:

c. 36 kHz

QUESTION:

What is the maximum power allowable for remote pick-up stations used as broadcast auxillary serv ices for AM and FM

broadcast stations?

ANSWER:

c. 35 W

QUESTION:

What is the classification of an FM station having an ERP not exceeding 30kW?

ANSWER:

b. Class B

QUESTION:

What is the modulation used for the stereophonic subcarrier of FM composite baseband signal?

ANSWER:

b. AM DSB SC

QUESTION:

What is the pilot subcarrier frequency used in FM stereophonic transmission?

ANSWER:

b. 19 kHz

QUESTION:

The output power of an FM transmitter is 5 kW. If the power loss in transmission line is around 10 W and the antenna has a

power gain of 6 dB, what is the ERP of the station in kW?

ANSWER:

d. 19.96 kW

SOLUTION (IF PROBLEM SOLVING):

GANT = 6 dB = 4

ERP = (5000 – 10) x 4 = 4990 x 4 = 19,960 W or 19.96 kW

QUESTION:

Frequency allocation of FM broadcast in the Philippines…

ANSWER:

b. 88 – 108 MHz

QUESTION:

What is the color TV system adopted by the Philippines?

ANSWER:

a. NTSC

QUESTION:

Exact v alue of color subcarrier frequency (MHz) is …

ANSWER:

d. 3.579545

QUESTION:

Determine the v isual carrier frequency of TV channel 9.

ANSWER:

b. 187.25 MHz


fNLB = 174 + (N – 7)6, using Arithmetic Progression

f9LB = 174 + (9 – 7)6 = 174 + (2)6 = 174 + 12 = 186 MHz, low band frequency of channel 9

fVC = 186 + 1.25 = 187.25 MHz, visual carrier frequency of channel 9

QUESTION:

What is the maximum allowable ERPs for channels 7 – 13 in Metro Manila and Metro Cebu?

ANSWER:

d. 1 MW

QUESTION:

At NTSC standard, the number of lines per frame = ________ lines/frame

ANSWER:

b. 525

QUESTION:

At NTSC standard, line frequency = 15734.264 Hz. What is the equivalent line period?

ANSWER:

c. 63.556 usec


fH = 15734.264 Hz

H = 1 / fH = 1 / 15734.264

H = 63.556 x 10-6 = 63.556 usec

QUESTION:

Nominal RF bandwidth of NTSC TV channel…

ANSWER:

c. 6 MHz

QUESTION:

A land mobile station used for the transmission of TV program materials and related communications from the scenes of

ev ents occuring at remote points from TV broadcast station studios to TV broadcast station.

ANSWER:

a. TV Pick-up station

QUESTION:

For a total capacity of 36 Mbps and 64-QAM of digital modulation, what is the ideal RF bandwidth?

ANSWER:

c. 6 MHz


For a 64-QAM, the total number of symbol combinations is 64 symbols and the number of bits to produce this

is…

n = log2 64 = 6 bits per symbol

Therefore the ideal RF bandwidth is…

BW = fB / n = 36 Mbps / 6 bits

BW = 6 MHz

QUESTION:

What is the mode of radio wave propagation that utilized ionosphere as a medium of transmission and / or reception of

radio signals?

ANSWER:

b. sky wave

QUESTION:

What is the wavelength of a radio signal trav elling at a frequency of 220 MHz in a coaxial line having Teflon foam as its

dielectric, εr = 2?

ANSWER:

c. 0.96 m


c = 3 x 108 m/sec = 300 x 106 m/sec

v elocity factor v f = 1 / sqrt (εr) = 1 / sqrt (2) = 0.707 = v P / c

Therefore the v elocity of the radio signal in the coaxial line is …

v P = 0.707c = 0.707 (300 x 106) = 212,132,034.36 m/sec (or 212 x 106 m/sec approx.)

so that the wavelength of the signal is …

λ = v P / f = 212 x 106 / 220 x 106 = 0.963636… m or 0.96 m approx.

QUESTION:

What is the angle of refraction in a Teflon (ε r2 = 2) medium of a radio wave from air (ε r1 = 1.0) if its angle of incidence is

45°?

ANSWER:

d. 30°


Using Snell’s Law…

Sqrt (εr1) sin θi = Sqrt (εr2) sin θr

Sqrt (1) sin 45° = Sqrt (2) sin θr

θr = sin-1 [(Sqrt (1) sin 45°) / Sqrt (2)] = sin-1 (0.5) = 30°

QUESTION:

An ionosphere layer also termed as “absorption layer” because it absorbs most of the frequencies above 100 kHz is

known as the … layer.

ANSWER:

a. D


The D layer has a critical frequency in the order of 100 kHz. Ev en MF band frequencies are absorbed by this

layer during sky wave propagation particularly in AM and SW radio broadcasting.

QUESTION:

As per ITU-R Recc. V.431-6 Tables 1 & 2 Wav elength Classifications, what is the classification of Super High Frequency?

ANSWER:

c. centimetric


SHF band: 3 GHz – 30 GHz

λmax = 3 x 108 / 3 x 109 = 0.1 m = 100 cm

λmin = 3 x 108 / 30 x 109 = 0.01 m = 1 cm

SHF band wavelength classification is ranging from 1 cm to 100 cm. Therefore it is centimetric wave.

QUESTION:

What is a div ersity scheme that uses two (2) separate antennas and receivers for each single transmitter?

ANSWER:

b. space div ersity

QUESTION:

What is a div ersity scheme that uses two (2) different frequencies in a simplex path?

ANSWER:

a. frequency div ersity

QUESTION:

What is the critical frequency of a layer if the maximum v alue of electron density is 2 x 106 per cm3?

ANSWER:

c. 13 MHz


Nmax = 2 x 106 per cm3 = 2 x 106 x 106 per m3 = 2 x 1012 per m3

fc = 9 x sqrt (Nmax) = 9 x sqrt (2 x 1012)

fc = 12.73 MHz or 13 MHz approx.

QUESTION:

A radio communication link is to be established v ia the ionosphere. The maximum virtual height of the layer is 110 km. at

the midpoint of the path and the critical frequency is 4 MHz. If the distance between the radio stations is 500 km, what is

the suitable v alue for the optimum working frequency? Use flat terrain analysis.

ANSWER:

c. 8.4 MHz


For flat terrain analysis, tan i = d/2hv

i = tan-1 [d/2hv] = tan-1 [500/2(110)] = tan-1 [2.273] = 66.25° angle of incidence

MUF = fc x sec i = fc / cos i = 4 / cos 66.25° = 4 / 0.40275 = 9.932 MHz v ia Secant Law

OWF = 0.85 x MUF = 0.85 (9.932) = 8.4422 MHz or 8.4 MHz approx.

QUESTION:

The power density is inv ersely proportional to the square of the distance from the source. This law is known as…

ANSWER:

c. Inv erse Square law

QUESTION:

The lowest portion of the ionosphere that is useful for long-distance communication by amateurs; about 100 to 115 km

above the earth is known as the… layer. This is often termed as the Kennely-Heavyside layer.

ANSWER:

b. E

QUESTION:

A graph which shows the radiation in actual field strength of electromagnetic fields at all points which are at equal

distance from the antenna is known as…

ANSWER:

b. Radiation Pattern

QUESTION:

The efficiency of an antenna is 82 %. Its radiation resistance is 30 Ω. What is the v alue of its loss resistance?

ANSWER:

d. 6.58 Ω


η = Rd/(Rd + Rloss)

0.82 = 30/(30 + R loss)

0.82 (30 + Rloss) = 30 = 24.6 + 0.82 R loss

Rloss = (30 – 24.6) / 0.82 = 6.5854 Ω or 6.58 Ω approx.

QUESTION:

A phenomenon on the surface of the sun with appearance and disappearance of dark irregularly shaped areas.

ANSWER:

b. 11-year sunspot

QUESTION:

What should be done to increase the transmission distance at frequencies higher than HF bands?

ANSWER:

b. increase antenna height

QUESTION:

Which of the following factors must be considered in the transmission of a surface wave to reduce attenuation?

ANSWER:

d. all choices

QUESTION:

A radio station operates at 11 meter wavelength. What is the designated band of station’s frequency?

ANSWER:

b. HF


c = 3 x 108 m/sec

λ = 11 m = c / f

f = 3 x 108 / 11 = 27 MHz approx., which is within 3 – 30 MHz range designated as HF band

QUESTION:

What is the total radio horizon distance between an 80 ft transmitting station and a 20 ft receiv ing station?

ANSWER:

d. 18.97 mi


dRH (TOT) = sqrt (2 x hT) + sqrt (2 x hR)

dRH (TOT) = sqrt (2 x 80) + sqrt (2 x 20)

dRH (TOT) = 18.97 mi

QUESTION:

A power density of 1.57 x 10-4 W/m2 is measured 50 meters from a test antenna whose directive gain is 2.15 dB. How

much power was fed into the test antenna?

ANSWER:

c. 3 W


From Inv erse Square Law, PD = PR/4πd2

PR = PD x 4πd2 = 1.57 x 10-4 x 4π(50)2 = 4.93 W approx. is the radiated power

GANT = log-1 [2.15 dB/10] = 1.64

PR = PFED x GANT

PFED = PR / GANT = 4.93 / 1.64 = 3.007 W or 3 W approx.

QUESTION: Identical telephone numbers

in different parts of a country are

distinguished by their ___.

ANSWER:

b. area codes

QUESTION: Telephone traffic is

measured ____.

ANSWER:

a. in erlangs

QUESTION: In a cellular telephone

system, each cell site contains a ____.

ANSWER:

a. repeater

QUESTION: When the signal from a

mobile cellular unit drops below a

certain lev el, what action occurs?

ANSWER:

c. the unit is “handed off” to a closer

cell

QUESTION: In a cellular telephone

system, group of cells is called ___.

ANSWER:

b. cluster

QUESTION: In Celluar Telephone

Systems, these are transmissions from

base stations to mobile units (Downlink)

ANSWER:

a. forward links

QUESTION: A CDMA mobile measures

the signal strength from the base as -100

dBm. What should the mobile

transmitter power be set to as a first

approximation, considering - 76 dB at

mobile power contol?

ANSWER:

c. 250 mW


PT = -76 dB - PR

Where:

PT = transmitted power in dBm

PR = receiv ed power in dBm

PT = -76 dB - PR

= -76 dB – (-100dBm)

= 24 dBm

= 250 mW

QUESTION: A telephone signal takes 2ms

to reach its destination. Calculate the

v ia net loss required for an acceptable

amount of echo.

ANSWER:

d. 0.8 dB


VNL = 0.2t + 0.4 dB

Where:

VNL = minimum required v ia net loss in

dB

t = time delay in ms for propagation

one way along line

VNL = 0.2t + 0.4 dB

= 0.2 X 2 + 0.4

= 0.8 dB

QUESTION:

The typical v oltage across a telephone

when on-hook is:

ANSWER:

a. 48 v olts DC

QUESTION:

Central offices are connected

by:

ANSWER:

b. trunk lines

QUESTION:

In telephony,

call blocking is:

ANSWER:

b. occurs when the central office

capacity is exceeded

QUESTION:

The cable used for

local loops in

telephone system is

mainly:

ANSWER:

a. twisted-pair copper wire

QUESTION:

In DTMF, the four

v ertical frequencies

are ____.

ANSWER:

b.

697Hz,770Hz,852Hz,941Hz

QUESTION:

In DTMF, the Horizontal

frequencies are

ANSWER:

a. 1209Hz,

1336Hz,1477Hz,1633Hz

QUESTION: In Celluar Telephone

Systems, these are transmissions from

mobile units to base stations (Uplink)

ANSWER:

b. rev erse links

QUESTION:

In DTMF, the

horizontal

frequencies is also

known as

ANSWER:

b. high group frequencies

QUESTION:

In DTMF, the Vertical

frequencies is also known as

ANSWER:

a. low group frequencies

QUESTION:

The bandwidth of v oice-grade signals

on a telephone system is restricted in

order to:

ANSWER:

c. allow signals to be multiplexed

QUESTION:

11. This is the highest-ranking office in

the DDD network in telephony in terms

of the size of the geographical area

serv ed and the trunking options

av ailable.

ANSWER:

b. regional center

QUESTION:

In Cellular Radio, AMPS stand for:

ANSWER:

d. Adv anced Mobile Phone Service

QUESTION:

In Cellular Radio, BSC stands for:

ANSWER:

a. Base Station Controller

QUESTION:

In Cellular Radio, MSC stands for:

ANSWER:

a. Mobile Switching Center

QUESTION:

In GSM, voice channels are called:

ANSWER:

a. traffic channels

QUESTION:

In Mobile Communications, GSM uses:

ANSWER:

a. frequency

hopping

QUESTION:

In Mobile Communications, IMSI stands

for:

ANSWER:

b. International Mobile Subscriber

Identification

QUESTION:

An acoustical phenomenon wherein the

sound continues to persist after the cause

of sound has stopped resulting in repeated

reflections is called…

ANSWER:

b. rev erberation

QUESTION:

A group of filters has 1/3 octav e of spacing.

If the initial frequency is 25 Hz, what is the

next frequency available for the filter?

ANSWER: d. 31.5 Hz


f2 = 2x f1 where x = 1/3, fraction of

an octave

f2 = 21/3 x 25 = 31.5 Hz

QUESTION:

+ 26 dBu is how many v olts?

ANSWER: b. 15.5 V


V (dBu) = 20 log [ v oltage in Volts /

0.775 Volts ]

26 = 20 log [ v oltage in Volts /

0.775 V ]

26 / 20 = log [ v oltage in Volts /

0.775 V ] = 1.3

Voltage = log-1 (1.3) x 0.775 V

Voltage = 15.5 V

QUESTION:

A type of microphone that uses the

principle of a capacitor as a means of

transduction. It uses a polarizing voltage of

between 9 and 48 V of DC supply applied

to its diaphragm by an external power

supply.

ANSWER:

b. Condenser

QUESTION:

Determine the sound power in Watts

produced by the bank’s alarm if a by-

stander heard the alarm at a sound

pressure lev el of 100 dB-SPL. The by-stander

is 100 ft away from the bank.

ANSWER: d. 58.65 W


PWL = SPL + 20 log D(m) + 8

PWL = 100 + 20 log (100/3.28) + 8 =

137.68 dB-PWL

137.68 = 10 log W + 120

W = log-1 [(137.68 – 120)/10]

W = 58.65 Watts

QUESTION:

A loudspeaker produces an SPL of 85dB-SPL

at 1 meter distance and input electrical

power of 1 W. How loud is the SPL at

distance of 20 meters if this speaker is driven

to 10 W of electrical power?

ANSWER: b. 69 dB-SPL


SPL@1m/1W = 85 dB-SPL (given)

SPL@20m/1W = 85 - 20 log

(20m/1m) = 59 dB-SPL

SPL@20m/10W = 59 + 10 log

(10W/1W) = 69 dB-SPL

QUESTION:

A number from 0 to 1 representing the

ability of a surface material to absorb

sound energy is known as…

ANSWER:

c. Absorption Coefficient

QUESTION:

The difference in dB between the loudest

lev el of sound and the softest passage of

sound is known as _

ANSWER:

d. dynamic range

QUESTION:

The highest frequency that can be used

for skywave propagation between two

specific points on earth’s surface.

Choices:

a. Critical Frequency b. MUF c.

Cut-off frequency d. mid frequency

ANSWER: a

QUESTION:

Variation in signal loss caused by

natural weather disturbances.

Choices:

a. attenuation b. fading

c. spreading loss d. weather loss

ANSWER: b

QUESTION:

Determine the radio horizon for a

transmit antenna that is 200 m high and

a receiv ing antenna that is 100 m high

Choices:

a. 99.5km b. 96.5 km c. 95.87

km d. 97.5 km

ANSWER: a


D = √ 17ht + √ 17hr

= √ 17(200) + √ 17(100)

= 99.5 km

QUESTION:

The height above the earth’s surface

from which a refracted wave appears

to have been reflected…

Choices:

a. actual height b. v irtual height

c. av erage height d. mean height

ANSWER: b

QUESTION:

The highest frequency that can be used

for skywave propagation between two

specific points on earth’s surface.

Choices:

a. Critical Frequency b. MUF c.

Cut-off frequency d. center

frequency

ANSWER: a

QUESTION:

The angular separation between the

two half-power points on the power

density radiation pattern.

Choices:

a. Bandwidth b Beamwidth c.

Footprint d. Azimuth

ANSWER:

Beamwidth

QUESTION:

Refers to the direction in space of

electric v ector of the electromagnetic

wave radiated from an antenna and is

parallel to the antenna itself.

ANSWER:

Polarization

QUESTION:

Electromagnetic waves that are directed

above the horizon level.

Choices:

a. ground waves b. surface waves c.

sky waves d. space waves

ANSWER: c

QUESTION:

Placing a metallic array on the antenna

effects to increase the current at the

base of the antenna, and also to make

the current distribution more uniform.

What is this called?

ANSWER:

Top loading

QUESTION:

What principle that states that the

properties of an antenna are

independent of whether it is used for

transmission or reception.

ANSWER:

Principle of reciprocity

QUESTION:

Calculate the beam width between

nulls of a 2-m paraboloid reflector used

at 6GHz. Note: such reflectors are often

used at that frequency as antennas

outside broadcast television microwave

links.

ANSWER:

3.50 (c)


Φ0=

Φ0=3.50

QUESTION:

This is often used to cure the problem of

great thickness required of lenses used

at lower microwave frequencies or for

strong curv ed wavefronts.

ANSWER:

Zoning

QUESTION:

A structure-generally metallic and

sometimes v ery complex-designed to

prov ide an efficient coupling between

space and the output of a transmitter or

input to a receiv er.

ANSWER:

Antenna

QUESTION:

The ratio comparing the power density

generated by a practical antenna in

some direction, with that due to an

isotopic antenna radiating the same

total power.

ANSWER:

Directiv e gain(b)

QUESTION:

Any array that is directional at right

angles to the plane of the array is said,

by inference, to hav e __________.

ANSWER:

Broadside action

QUESTION:

The ratio of the focal length to the

mouth diameter is called __________ of

the parabola, just as in camera lenses.

ANSWER:

Aperture

QUESTION:

Corresponds to a resonant transmission

line, and the dipole antennas describe

so far hav e been resonant.

ANSWER:

Resonant antenna (b)

QUESTION:

An optic fiber is made of glass with a

refractiv e index of 1.55 and is clad with

another glass with a refractiv e index of

1.51. Launching takes place from air.

What numerical aperture does the fiber

hav e?

Choices:

a. 0.852 b. 0.352

c. 1.032 d. 0.235

ANSWER:

b. 0.352


By equation (20.10), the fractional

difference between the indexes is:

∆=(n1-n2)/n1

=(1.55-1.51)/1.55

=0.0258

By equation (20.11), the numerical

aperture is found to be:

NA=n1√(2∆)

=1.55√[(2)(0.0258)]

= 0.352

QUESTION:

An optic fiber is made of glass with a

refractiv e index of 1.55 and is clad with

another glass with a refractiv e index of

1.51. Launching takes place from air.

What is the acceptance angle?

ANSWER:

c. 20.6


By equation (20.10), the fractional

difference between the indexes is:

∆=(n1-n2)/n1

=(1.55-1.51)/1.55

=0.0258

By equation (20.11), the numerical

aperture is found to be:

NA=n1√(2∆)

=1.55√[(2)(0.0258)]

= 0.352

By equation (20.8), the acceptance

angle is:

Θ0(max)=sin-1NA= sin-10.352=20.6

QUESTION:

For a single-mode optical cable with

0.25-dB/km loss, determine the optical

power 100km from a 0.1-mW light

source.

ANSWER:

-35dBm


P=0.1mW x 10-[(0.25)(100)]/(10)

=1 x 10-4 x 10[(0.25)(100)]/(10)]

=(1 x 10-4)(1 x 10-25)

=0.316µW

P(dBm)= 10log( )

= -35dBm

QUESTION:

For an optical fiber 10km long with a

pulse-spreading constant of 5ns/km,

determine the maximum digital

transmission rates for return-to-zero.

ANSWER:

20Mbps


Fb=

=20Mbps

QUESTION:

In fiber optics, it is a measure of the

conv ersion efficiency of a

photodetector. It is the ratio of the

output current of a photodiode to the

input optical power and has the unit of

amperes per watt

ANSWER:

Responsiv ity

QUESTION:

A phenomenon also called

stress corrosion resulting if the

glass fiber is exposed to long

periods of high humidity?

ANSWER A. Static fatigue:

QUESTION:

The theory which states that

when v isible light or high-

frequency electromagnetic

radiation illuminates a metallic

surface, electrons are emitted.

ANSWER:

B. Planck’s law

QUESTION:

The science of measuring only light

waves that are visible to the human eye

ANSWER:

B. Photometry

QUESTION:

The process of constructing an ILD that

is similar to LED except that the ends

are highly polished.

ANSWER:

C. Lasing

QUESTION:

A phenomenon in optical fibers

communication system that is caused

by the difference in the propagation

times of light rays that take different

paths down the fiber.

ANSWER:

A. Pulse spreading

Question:

For an electronic dev ice operating at a temperature of 17°C with a bandwidth of 10 kHz, determine the thermal noise

power in dBm .

ANSWER:

c. -134dBm

SOLUTION (IF PROBLEM-SOLVING)

N = KTB T(kelv in) = 17°C + 273° = 290 K B = 1 x 104 Hz

= (1.38 x 10-23)(290)(1 x 104) = 4 x 10-17 W

N(dBm) = 10log (4 x 10-17) = -134 dBm

0.001

Question:

A 300Ω resistor is connected across the 300Ω antenna input of a telev ision receiver. The bandwidth of the receiv er is

6MHz, and the resistor is at room temperature .Find the noise v oltage applied to the receiver input.

ANSWER:

a. 5.4 µV


VN = √

= 4(1.38 x 10-23 J/K)(293 K)(6 x 106 Hz)(300 Ω)

= 5.4 x 10-6 V

= 5.4 µV

Question:

The signal power at the input to an amplifier is 100µW and the noise power is 1 µW. At the output, the signal power is 1W

and the noise power is 30mW. What is the amplifier noise figure, as a ratio?

ANSWER:

c. 3


(S/N)p = 100µW = 100

1µW

(S/N)o = 1W = 33.3

0.03W

NF (ratio) = 100 = 3

33.5

Question:

It is desired to operate a receiv er with NF = 8dB at S/N = 15 dB ov er a 200-KHz bandwidth at ambient temperature.

Calculate the receiver’s sensitivity.

ANSWER:

a. -98dBm


S = Sensitiv ity = -74dBm + NF + 10log∆f + desired S/N

S = -174 + 8 + 10log(200,000) + 15

S = -98 dBm

Question:

A Satellite receiv ing system includes a dish antenna ( Teq = 35 K) connected via a coupling network (Teq= 40 K) to a

microwave receiver (Teq=52 K referred to its input). What is the noise power to the receiv er’s input over a 1-MHz

frequency range?

Choices:

a. 1.75 x 10-15W b. 1.75 x 10-12W c. 1.15 x 10-15W d. 1.15 x 10-12W

ANSWER:

a. 1.75 x 10-15


PN = KT∆f

= 1.38 x 10-23 J/K (35 + 40 + 52)K (1MHz)

= 1.75 x 10-15 W

Question:

Equiv alent temperature of a passiv e system having the same noise power output of a giv en system.

ANSWER:

d. noise temperature

Question:

The noise v oltage produced across a 50Ω is input resistance at a temperature of 302°C with a bandwidth of 6 MHz is

______.

ANSWER:

d. 2.24µV


VN = √

= 4(1.38 x 10-23)(302)(6 x 106)(50)

= 2.24µV

Question:

Determine the worst-case output S/N for a broadcast FM program that has a maximum intelligence frequency of 5 kHz.

The input S/N is 2

ANSWER:

a. 30


ᵟ = φ x fi

= 0.5 x 5 kHz = 2.5 kHz

75 kHz = 30

2.5 kHz

QUESTION:

The technique that uses the BPSK vector relationship to generate an output with logical 0s and 1s determined by

comparing the phase of two successiv e data bits is

ANSWER:

b. DPSK

QUESTION:

A method of nonspontaneous lysing (splitting) of a substance by the input of electrical energy, and is often used to

decompose a compound into its elements.

ANSWER:

b. electrolysis

QUESTION:

A special digital modulation technique

that achieves high data rates in limited-

bandwidth channels is called

ANSWER:

c. Quadrature amplitude

modulation (QAM)

QUESTION:

FSK systems are much superior to two-

tone amplitude-modulation systems

with respect to

ANSWER:

c. Ionospheric fading

characteristics

QUESTION:

Using an oscilloscope to display

ov erlayed received data bits that

prov ide information on noise, jitter, and

linearity is called a(n)

ANSWER:

a. Eye pattern

QUESTION:

The type of radio transmission that uses

pseudorandomly switched transmissions

is known as

a.

ANSWER:

b. Spread spectrum

QUESTION:

The acronym CDMA refers to ________.

a.

ANSWER:

d. Code-division multiple-

access systems

QUESTION:

The acronym OFDM refers to ________.

a.

ANSWER:

Orthogonal Frequency Division

Multiplexing

QUESTION:

Using radio to transmit gathered data

on some particular phenomenon

without human monitors is known as

ANSWER:

Radio telemetry

QUESTION:

The acronym for the form of data

transmission in which the modulating

wave shifts the output between two

predetermined frequencies is _____.

ANSWER:

a. FSK

QUESTION:

Pseudorandom implies a sequence that

can be _____ but has the properties of

randomness.

a.

ANSWER:

re-created

QUESTION:

______ implies that both analog and

digital signals share the same channel

bandwidth.

ANSWER:

Hybrid

QUESTION:

Telemetry may be defined as _____

metering.

ANSWER:

Remote

QUESTION:

Which is not a type of pulse

modulation?

ANSWER:

Pulse-frequency modulation (PFM)

QUESTION:

PPM and PWM are superior to PAM

systems in

ANSWER:

Noise characteristics

QUESTION:

A procedure that decides which device

has permission to transmit at a giv en

time is called

ANSWER:

Line Control

QUESTION:

The major difficulty faced by delta

modulators is

ANSWER:

Slope ov erload

QUESTION:

The AT&T T1 lines

ANSWER:

Use 8-bit PCM code and

include 24 v oice channels

QUESTION:

The ground wire in a USB cable is ____

ANSWER:

Brown

QUESTION:

A(n) ________ is used to allow a digital

signal to be transmitted on an analog

channel.

ANSWER:

modem

QUESTION:

The bit ________ is the amount of power

in a digital bit for a giv en amount of

time.

ANSWER:

energy

QUESTION:

The relationship for bit rate to ________

bandwidth is defined by the Shannon-

Hartley theorem.

ANSWER:

Channel

QUESTION:

In an S/H circuit, the time that it must

hold the sampled v oltage is

ANSWER:

Aperture time

QUESTION:

Error signals associated with the

sampling process are called

ANSWER:

Foldov er distortion and aliasing

QUESTION:

A(n) ________ is a single LSI chip

containing both the ADC and DAC

circuitry.

ANSWER:

codec

QUESTION:

The NRZ digital signal-encoding format

has a ________ component in the

waveform.

ANSWER:

dc

QUESTION:

Reed–Solomon codes utilize a

technique called ________ to rearrange

the data into a nonlinear ordering

scheme to improv e the chance of data

correction.

ANSWER:

interleav ing

QUESTION:

The electric field intensity is measured in:

ANSWER:

a. V/m

QUESTION:

It is a result of an increase in the charge

density in dielectric materials.

ANSWER:

a. polarization

QUESTION:

It refers to the maximum antenna gain.

ANSWER:

a. directiv ity

QUESTION:

The maximum horizontal distance

between the transmitter and the

receiv er for line of sight

propagation is known as:

ANSWER:

a. radio horizon

QUESTION:

Typical mode of radiation of helical

antenna is:

ANSWER:

a. end fire

QUESTION:

The electric field is perpendicular to the

earth’s surface, the polarization

is:

ANSWER:

a. v ertical

QUESTION:

In what major RF band is ground wav e

basically applied?

ANSWER:

a. MF (Medium Frequency)

QUESTION:

A measure of mismatch in a

transmission line

ANSWER:

c. standing wave ratio

QUESTION:

The highest frequency that can be set

back to earth by the ionosphere, if

wav e is sent v ertically upward.

ANSWER:

c. critical frequency

QUESTION:

Trav el in a straight line from the

transmitting antenna to the receiv ing

antenna.

ANSWER:

c. space wave

QUESTION:

VLF wav es are for some types of

serv ices because

ANSWER:

c. they are v ery reliable

QUESTION:

It is the distance between two wav e

fronts hav ing the same phase at any

giv en instant.

ANSWER:

b. wavelength

QUESTION:

It is a piece of transmission line which is

normally short-circuited at the far end.

ANSWER:

b. stub

QUESTION:

A 50 ohms transmission line is

connected to a 30 ohm resistiv e

load. Calculate the reflection

coefficient.

ANSWER:

b. 0.25


Ref Coeff = (30 – 50)/(30 + 50) = 0.25

QUESTION:

The characteristic impedance of a

transmission line does not depend upon

its

ANSWER:

c. length

QUESTION:

Characteristic impedance of a

transmission line is the impedance

measured at the _______ when its

length is infinite.

ANSWER:

a. input

QUESTION:

Which region of the ionosphere is mainly

responsible for long-distance night time

communications?

ANSWER:

d. F layer

QUESTION:

Which is properly terminated antenna?

ANSWER:

a. rhombic

QUESTION:

Occurs when the radio beam is at point

of grazing ov er an obstacle.

ANSWER:

a. diffraction

QUESTION:

A microwav e communications system,

space loss calculation formula is

ANSWER:

c. 92.4 + 20log F + 20 log D

QUESTION: Is an OSI Layer which is

responsible for prov iding error-free

communications across the physical link

connecting primary and secondary

stations (nodes)

ANSWER: a. Data Link layer

QUESTION: Is the ratio of the largest

possible magnitude to the smallest

possible magnitude that can be

decoded by the digital-to-analog

conv erter.

ANSWER: d. Dynamic range

QUESTION: Is a PCM system which uses

a single bit PCM code to achieve digital

transmission of analog signals.

ANSWER: b. Delta modulation

QUESTION: Is a redundancy error

detection scheme that uses parity to

determine if a transmission error has

occurred within a message and is

sometimes called message parity.

ANSWER: a. Longitudinal redundancy

check

QUESTION: Is an n-bit data register inside

the UART that keeps track of the UART’s

transmit and receiv e buffer registers.

ANSWER: b. Status Word register

QUESTION: Is an access method used

primarily with LANs configured in a bus

topology.

ANSWER: a. CSMA/CD

QUESTION: IP version 4 address length is

ANSWER: a. 32 bits

QUESTION: Is a multiport bridge that

prov ides bridging function.

ANSWER: d. Switch

QUESTION: Is a device which operates in

the Network layer and it makes

forwarding decisions on the basis of

network addresses.

ANSWER: c. Router

QUESTION: OC-1 (STS-1) line rate is

ANSWER: a. 51.84 Mbps

QUESTION: Is one in which all computers

share their resources with all the other

computers on the network.

ANSWER: b. Peer-to-peer client/server

network

QUESTION: Is used to interface DTEs to

digital transmission channels

ANSWER: d. Channel service unit

QUESTION: Modulation which combines

encoding and modulation to reduce

the

probability of error.

ANSWER: d. TCM

QUESTION: Is an empirical record of a

system’s actual bit error performance

ANSWER: b. BER

QUESTION: Is an error-correcting code

used for correcting transmission errors in

synchronous data streams.

ANSWER: d. Hamming code

IECEP Manila

QUESTION:

What happens to the frequency of the

wave and to its wavelength when a sound

wave produced in one medium enters

another medium with a different speed?

ANSWER:

c. the frequency of the wave stays the

same while the wavelength changes.

QUESTION: An interest rate of 10%

compounded continuously is desired of an

inv estment of P15,000. How many years will

be required to recov er the capital with the

desired interest if P2,500 is receiv ed each

year?

ANSWER:

c. 9.375 years

SOLUTION (IF PROBLEM SOLVING)

A=Pert

15,000 = 15,000e0.10t-2500t

t = 9.375 years

QUESTION:

What is the pH lev el of toilet soap?

ANSWER:

c.10

QUESTION: The process of combining

multiple audio signals into one track is

called?

ANSWER: a. audio mixing

QUESTION: The speed of sequence of

musical notes is called?

ANSWER: b. Tempo

QUESTION: If the frequency of a sound is

increased, what will happen to its pitch?

ANSWER: b. Increases

QUESTION:

A type of microwave protection system

where each working channel has a

dedicated back up or spare channel.

ANSWER: D. Hot Standby

est qustion

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