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A mammography service 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?
A type of luminescence where the visible light is
emitted only during the stimulation of the phosphor.
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?
Radiation doses in the range of approximately200 to
1000 rad produce the
Hematologic syndrome
Ratio of incident to transmitted radiation through a
grid ratio of patient dose with and without grid
A radiographic single-phase unit installed in a private
office has a maximum capacity of 100 milliseconds of
120kVp and 500mA. What is the power rating?
Bucky factor
Who completes the development of first computed
tomographic (CT) scanner (EMI, Ltd.) in 1973?
It is the study of the response of an image receptor to
Ratio of radiographic contrast with a grid to that
without a grid.
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
ECG recording requires a bandwidth of 0.05 to ____
Find the potential generated if blood flowing in a
vessel with radius 0.9 cm cuts a magnetic field of 250
G. Assume a volume flow rate of 175 cubic cm per
Period during which heart contracts.
Apparatus for measuring blood pressure
42 kW
contrast improvement factor
600 rad
309 uV
Given the energy level of 6.624x10^-18 J imparted to
an electron stream by an X-ray device, calculate the
frequency in MHz.
10^10 MHz
10^10 MHz
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.
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).
Photoelectric effect
An optical electronic device that measures the color
concentration of a substance in solution.
Recording of heart sounds
Recorder for measuring galvanic skin resistance
It consists of 36 unique codes representing the 10
digits and 26 uppercase letters.
The first fixed- length character code developed for
machines rather than for people
The early pioneer in the development of errordetection and correction procedures
The most reliable convolutional coding scheme for
error detection
For the given 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
code 39
A signal at the input to a mu-law compressor is
positive with its voltage one-half the maximum value.
What proportion of the maximum output voltage is
Inaccuracies caused by the representation of a
continuously varying quantity as one of a number of
discrete values.
quantizing errors
Baudot Code
Richard W. Hamming
22.2 dB
Circuit for digitizing voice at a low data rate by using
knowledge of the way in which voice sounds are
A coding scheme that records the change in signal
level since the precious sample
Distortion created by using too low a sampling rate
when coding an analog signal for digital transmission
A network with bandwidth of 10 Mbps can pass only
an average of 12000 frames per minute with each
frame carrying an average of 10000 bits. What is the
throughput of this network?
A telephone subscriber line must have an SNRdB
above 40. What is the minimum number of bits?
delta modulation
either a or b
a. aliasing
2 Mbps
b. foldover distortion
= 2 Mbps
SNRdB = 6.02nb + 1.76 = 40
n = 6.35
The thick coaxial cable implementation of standard
A bit pattern or a character added to the beginning
and the end of a frame to separate the frames
An IPv4 has an address space of how many?
10 Base 5
232 = 4294967296
What is the bit rate of STS – 1?
A block coding technique in which four bits are
encoded into a five bit code
A national standards organization that defines
standards in the United States
In asynchronous transmission, one or more bits to
indicate the end of transmission
What is the overhead (number of extra bits) in the DS3 service?
The minimum sampling rate according to Nyquist
It is used in wireless applications in which stations
must be able to share the medium without interception
by an eavesdropper and without being subject to
jamming from a malicious intruder
An error detection method which uses one’s
complement arithmetic
It is a connecting device between two internetworks
that use different models
It is an undesired shift or width change in digital bits of
data due to circuitry action which causes bits to arrive
at different times
In PCM system, it is the ratio of the maximum input
voltage level to the smallest voltage level that can be
A multiplexer combines four 100-kbps channels using
a time slot of 2 bits, determine the frame duration.
51.84 Mbps
4B/5B Encoding
stop bit
1.368 Mbps
twice the highest frequency of a signal
spread spectrum
Dynamic range
The link carries 50,000 frames /sec
The frame duration = 1/50,000 = 20s
Determine the Hamming distance for the codewords Two
(10101, 11001)
10101 XOR 11001 = 01100 ( presence of two 1)
An address space is the total number of addresses
used by the protocol, such as IPv4 and IPv6. What 2128
is the address space of IPv6?
It is a standard designed by ITU to allow telephones in H.323
the public telephone
network to talk to computers/terminals connected to
the internet
A computer monitor has a resolution of 1200 by 1000 12 Megabits
pixels. If each pixel uses 1024 colors, how many bits
are needed to send the complete contents of a
1,200 times 1000 pixels x 10 bits = 12 Mb
Combination of compression at the transmitter and
expansion at the receiver of communications system.
A device launches or receives a wave in a
transmission line or waveguide in one direction only.
A type of linear-beam microwave tube that uses
velocity modulation of the electron beam
A series of pulses in which the amplitude of each
pulse represents the amplitude of the information
signal at a given time.
_______________ is used to position samples of the
different message signals in non-overlapping time
A ___________ is similar to a phasor diagram except
that the entire phasor is not drawn.
It was the first fixed length character code.
It involves transmitting each character twice.
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 variable, at a particular instant of
time, is the result of a large number of individual
random events.
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.
A series of pulses, in which the timing of each pulse
represents the ampltitude of the information signal at
a given time.
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?
1024 colors requires 10 bits , 2 10 = 1024
directional coupler
constellation diagram
Baudot Code
Central Limit Theorem
Asynchronous transfer mode (ATM)
Pulse Position Modulation
R = 11.6m
Variation in received field strength over time due to
changes in propagation conditions.
The atomic weight of an element is approximately
determined by
Of the following substances the worst conductor is
The volt is the standard unit of
Which of the following antenna types is not designed
for transmitting at 10 Ghz
The type of radio wave responsible for long distance
communications by multiple skips is the:
Line of sight communications is not a factor in which
frequency range?
It refers to the rate of change of a signal on the
transmission medium after encoding and modulation
have occurred.
It was the first fixed-length character code developed
for machines rather than people.
A receiver-transmitter station used to increase the
communications range of VHF, UHF and microwave
signals is called a(n):
It represents the simplest whole number ratio of the
various types of atoms in a compound.
It is a term that is often misunderstood and commonly
confused with bit rate (bps)
Defined as the optimum level of a test tone on a
channel at same point in a communication system.
Duplicating each data unit for the purpose of detecting
errors is a form of error detection called ______.
Determine the wavelength of a 4 Ghz signal.
What is the device that converts energy from one form
to another?
It may be defined as any undesired voltages or
currents that ultimately end up appearing in the
receiver output.
The channel capacity of a 5 kHz bandwidth binary
system is ____ bits/s. Assuming no noise.
Microwaves are frequencies above _____ GHz.
The government agencies that regulates radio
communications in the US is the ________.
A wave guide acts a/an _______ filter
Coax is not used beyond frequencies of about ______
Data Communications refers to the transmission of
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.
It is often used to compare the performance of one
digital modulation technique to another.
It is the process of converting an infinite number of
possibilities to a finite number of conditions.
the number of protons
electromotive force
Zepp antenna
Direct Wave
Baudot Code
empirical formula
transmission level point
Electrical noise
all of the above
a. voice
1 kHz
b. video
bandwidth efficiency
c. Computer data
For a PCM system with a maximum analog frequency
of 4kHz, determine the minimum sample rate.
8 kHz
It is another relatively simple form of redundancy error
checking where each character has a numerical value
assigned to it.
It is a modulation and multiplexing technique that
distributes the signal and its sidebands over a very
wide bandwidth.
The computers that hold shared files, programs and
the network operating system. They also provide
access to network resources to all the users of the
It is defined by the ITU-T as a service that provides
transmission channels capable of supporting
transmission rates greater than the primary data rate.
It is the only error-correction scheme that actually
detects and corrects transmission errors when they
are received without requiring a transmission..
This OSI Layer is responsible for network availability,
data storage and processor capacity. It also
determines the type of dialogue available.
It is often defined as the loss incurred by an
electromagnetic wave as it propagates in a straight
line through a vacuum with no absorption or reflection
of energy from nearby objects.
What do you call the accumulation of additional
sounds such as wind, street noise, other voices that
contribute to what the listener hear?
It is a single transmission path from transmitter to
receiver with line of sight range.
It is defined by the average rate at which energy is
carried out per unit area.
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
The process of combining multiple audio signals into
one track is called?
The speed of sequence of musical notes is called?
If the frequency of a sound is increased, what will
happen to its pitch?
A type of microwave protection system where each
working channel has a dedicated back up or spare
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
received data due to the quality of the circuit falling
below a predefined level.
Spread spectrum
Broadband ISDN
Forward Error Correction
Session layer
free space path loss
the frequency of the wave stays the same while
the wavelength changes.
audio mixing
Hot Standby
signal quality detector
______ which means that 2 or more bits in the data
unit have changed.?
It is a four-wire Gigabit Ethernet implementation.
It is a digital process that allows several connections
to share the high bandwidth of a link.
EEE 802.11 is define in which MAC sublayer?
It is the oldest microwave tube design which is
commonly used in radar transmitters where they can
generate peak power levels in the megawatt range.
A modulation process wherein both frequence and
phase remains constant while the amplitude changes.
It is the most powerful redundancy checking
technique which is based on binary division.
What do you call the element with electrical properties
between those of an insulator and a conductor?
In pulse-code modulation, it translates the quantized
samples into digital code words.
It is an error detection technique in which a redundant
bit is appended to every data unit so that the total
number of 1s in the unit (including the parity bit)
becomes even.
A local area network topology in which the individual
terminal, microcomputers or workstations are
connected directly to a central computer.
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
Find the maximum dynamic range for a linear PCM
system using 16-bit quantizing.
burst error
1000 Base-T
(b) and (c)
cyclic redundancy check
vertical redundancy check
quadrature amplitude modulation
98.08 dB
DR = 1.76 + 6.02m; dB
DR = 1.76 + 6.02(16)
DR = 98.08 dB
Compute the baud rate for a 72000 bps 64-QAM
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
A telephone signal takes 2ms to reach its destination.
Calculate the via net loss required for an acceptable
amount of echo.
0.8 dB
Telephone switch that connects only to other
switches, and not to individual customers.
tandem office
VNL = 0.2t + 0.4dB
VNL = 0.2 (2ms) + 0.4 dB
VNL = 0.8 dB
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.
The most common circuit used for demodulating
binary FSK signals.
We have 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.
We have an audio signal with a bandwidth of 4 MHz.
what is the bandwidth if we modulate the signal using
FM? Ignore FCC regulations.
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
8 KHz
BW = 2 x 4 KHz
= 8 KHz
= 40 MHz
= 7.63
A network topology in which data circulates from one
computer to the next in sequence.
Find the maximum dynamic range for linear PCM
system using 8-bit quantizing
49.92 dB
DR = 1.76 + 6.02(m)
DR = 1.76 + 6.02(8)
What frequencies would be generated by a telephone
using DTMF signalling, when the number 8 is
It is a means of transmitting data by shifting the phase
angle of the transmitted signal.
The name given for a set of standards for
communicating among computers in which the
primary purpose is to serve as a structural guideline
for exchanging information between computers,
workstations and networks.
852 Hz and 1336 Hz
Any transmission system which conveys 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.
What type of digital modulation scheme uses two or
more different output frequencies?
It is an error-correcting code used for correcting
transmission errors in synchronous data streams.
A suite of protocols that allows a wide variety of
computers to share the same network.
Noise that is primarily caused by lightning. Often
called as Static Noise.
Hamming Code
atmospheric noise
A modulation technique in which the frequency of the
modulated signal varies with the amplitude of the
modulating signal
Is a form of constant –amplitude angle modulation
similar to standard frequency modulation except the
modulating signal is a binary signal that varies
between two discrete voltage levels rather than a
continuously changing analog waveform.
The highest layer in the hierarchy and is analogous to
the general manager of the network by providing
access to the OSI environment.
What is the equation for Hartley’s Law?
Network topology wherein individual terminals,
microcomputers and workstations are connected
directly to a central computer.
The loss of data that occurs when two stations
transmit at the same time on a network
A term used to describe a telephone instrument
whose handset is on its cradle, ready to receive a ring
The most commonly used digital modulation scheme.
Simple form of redundancy error checking where each
character has a numerical value assigned to it. The
characters within a message are combined together
to produce an error checking character.
Is an eight-bit fixed length character set developed in
1962 by the International Business Machines
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.
Calculate the capacity of a telephone channel that has
a S/N of 1023?
30,000 b/s
Application layer
On hook
fa = fs – fm
= 44.1KHz – 30KHz
= 14.1 KHz
The telephone channel has a bandwidth of about
C= BW log2 (1+ S/N)
= 3 x 103 log2 (1+ 1023)
=30000 b/s
Designed to send characters of the message with the
specified bit rate but without any fixed timing
relationship from one character to the next.
Token Ring Standard
It is the process of extracting a phase-coherent
reference carrier from a receiver signal.
It is a potential problem whenever two metallic
conductors carrying different signals are located in
close proximity to each other.
What is the termed refer as the rapid degradation of
output signal quality with channel induced errors?
Carrier Recovery
threshold effect
What was the first fixed-length character code
developed for machines rather than for people?
A source whose output satisfies the condition of
statistical independence among letters in the
sequence is said to be_____.
Calculate the minimum data rate needed to transmit
audio with sampling rate of 30 Khz and 14 bits per
Handles error recovery, flow control (synchronization),
and sequencing (which terminals are sending and
which are receiving). It is considered the “media
access control layer”.
A MAC protocol for LANs, with stations connected
topologically or logically in a ring. Or the IEEE 802.5
LAN standard.
A network topology where each device is connected
to a centre point and all data is routed through that
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
Codes that have a restriction on the number of
consecutive 1s or 0s in a sequence.
Contains seven bytes (56 bits) of alternating 0s and
1s that alert the receiving system to the coming frame
and enable it to synchronize its input timing
Every letter was encoded into fixed length of binary
code words of length 5.
The composite signal that modulates the FM carrier.
It is a simple means of error detection. It involves the
addition of one extra bit to the bits that encode a
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
Speed at which symbols are transmitted in a digital
communication systems.
It is the process of converting an infinite number of
possibilities to a finite number of conditions.
It is the ratio of the largest possible magnitude to the
smallest possible magnitude that can easily be
decoded by the digital to analog converter in the
It is the institution that developed the ASCII (American
Standard Code for Information Intertchange).
In early 1900s, he showed that any composite signal
is a sum of a set of sine waves of different
frequencies, phases and amplitudes.
Find the binary equivalent of x8+x3+x+1.
Baudot code
420 Kb/s
Data Link Layer
Token Ring
Star network
Liquid Lasers
Run length limited code
Baudot Code
Huffman coding
Baud rate
Dynamic Range
Jean-Baptiste Fourier
1 1
Given a bandwidth of 6000 Hz for an ASK signal,
what is the baud rate?
6000 Hz
baud rate = bandwidth
6000 Hz = 6000 Hz
Compute the bit rate for a 2000 baud 16-QAM signal.
It is an electronic device that is used for computer
communications through telephone lines.
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 level code. What is the
maximum theoretical data rate
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.
Find the maximum dynamic range for a linear PCM
system using 8-bit quantizing.
In operation, many modern codecs achieved
compresion by first encoding the signals using a 12bit linear PCM code, then converting the 12-bit linear
code into an 8-bit compressed code by discarding
some of the bits. This is a simple example of:
Sampling of an analog signal using a sample-andhold circuit such that the sample has the same
amplitude for its whole duration.
The basic building block of the FDM hierarchy.
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
For Ethernet system with a length of 2.5km on coaxial
cable with a velocity factor of 0.66. What is the
propagation delay?
8000 bps
bit rate = baud * 4
2000 * 4 = 8000 bps
18 kbps
C = 2Blog2M = 2(4.5x103)log2(4) = 18 kbps
Harry Nyquist
49.92 dB
DR = 1.76 + 6.02m dB
= 1.76 + 6.02(8) dB
= 49.92 dB
Digital Signal Processing
Flat-topped Sampling
Message Channel
T=d/(VfC)=2.5km/(0.66*300000000m/s)=12.6 µs
A signal at the input to a µ-Law compressor is
positive, with its volatage one-half the maximum
value. What proportion of the maximum output voltage
is produced?
A telephone signal take 2ms to reach its destination.
Calculate the via net loss required for an acceptable
amount of echo.
0.876 Vo
Who invented the telegraph?
The simplest modulation technique, where a binary
information signal modulates the amplitude of an
analog carrier.
Samuel F.B Morse
Amplitude-Shift Keying
Vo=Vo(ln(1+(255*0.5)))/ln(1+255)=0.876 Vo
0.8 dB
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.
Error-correction scheme that actually detect and
corrects transmission errors when they are received
without requiring a retransmission.
It allows the overall complexity of the system to be
broken down into individual function –layers- that
operate essentially by themselves.
This are very useful pictorial representations that
clearly show the protocol operations such as words or
convetional drawings.
Pair of wires that connects the central office to the
users phone
How long does it take to dial the number 784-3745
using pulse dialing with .5s inter digit time?
Physical Layer
Forward Error Correction
State Transition Diagram
Local loop
0.7 + 0.8 + 0.4 + 0.3 + 0.7 + 0.4 + 0.5 (6x0.5) = 6.8s
Network that connects users who are in the same
general location
In operation, many modern codecs achieved
compresion by first encoding the signals using a 12bit linear PCM code, then converting the 12-bit linear
code into an 8-bit compressed code by discarding
some of the bits. This is a simple example of:
A balanced modulator that will used in conjuction with
a microwave generator, power amplifier, and bandpass filter, up-converts the IF carrier to an RF carrier
and amplifies the RF to the desired output power.
What is the equation for Hartley’s Law?
The loss of data that occurs when two stations
transmit at the same time on a network
We have an audio signal with a bandwidth of 5 HHz.
What is the bandwidth modulate the signal using FM?
Ignore FCC regulation.
Used to established a point to point connection across
a network.
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
Defines the rules of the conversation the message
passing among the network users
Responsible for providing signals to the loop sensing
activity and sending phone signals at the end of the
The typical amount of voltage in dc use in the battery
of the central office with respect to ground
Digital Signal Processing
Transmit Modulator
50 MHz
BW= 10 x 5MHz
f a = f s - fm
= 44.1kHz – 25kHz
= 19.1kHz
network protocol
A network that is composed of a smaller lan that are
closely link. It is needed for areas spread out
How many central office allotted for each exchange?
It is a method of switching that provides a separate
physical path for each symbol
The central office detects a request for service from a
telephone by:
The OSI Layer responsible for data tracking as it
moves through a network. It controls and ensures the
end – to – end integrity of the data message
propagated through the network between two devices.
It is used on long – distance circuits, in an effort to
overcome echoes caused by circuit imbalances.
The sensitivity of a radio receiver is given in terms of
dBm. If the receiver is receiving 200 mW, what is the
corresponding dBm of this signal?
An antenna with a noise temperature of 75 Kelvin is
connected to a receiver input with a noise
temperature of 300 K. Given the reference
temperature T0 = 290 K, find the noise figure of the
modulation index of an AM radio station is 0.75. If the
carrier power is 500W, what is the total transmitted
An FM transmitter system is using a 1MHz crystal
oscillator to generate a very 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 value?
A/an _______ is a range of frequency in which the
upper frequency is double the lower frequency.
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.
A small variable capacitance in parallel with each
section of ganged capacitor is called _______.
How many wavelengths long are required for a pair of
conductors to be considered as a transmission line?
Determine the time taken for a signal to travel down a
10 m transmission line, if its velocity factor is 0.7.
space switching
a flow of loop current
Echo Suppresors
23 dBm
dBm for 200 mW = 10 log (200mW/1mW) = 23 dBm
3.6 dB
641 W
 m2 
Pt  Pc1 
2 
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
47.6 ns
T= L/ (Vf x Vc)
T= 10 m/ (0.7)(3x108 m/s)
T= 47.6 ns
The maximum voltage standing wave of an RG-11/U
foam coaxial cable is 52 V and its minimum voltage is
17 V. How many percent of the incident power is the
reflected power?
At exactly one-quarter wavelength, the short-circuited
transmission line behaves as a(an) ________ circuit.
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.
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?
One complete revolution around a Smith Chart
represents _________ wavelengths.
A mismatched transmission line is also referred to as
a ___________ line.
It is the ratio of the speed of propagation on a line to
that of light in free-space.
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?
The modulated peak value of a signal is 125V and the
unmodulated carrier value is 85V. What is the
modulation index?
The total transmitted power of an AM broadcast
transmitter with a carrier power of 50kW when
modulated 80 percent is:
One of the advantages of DSB is the savings of great
deal of power. Which of the following is the reason
why it is not widely used?
If the input in a transmitter is collector-modulated, the
system is called a _______________________.
The input to an FM receiver has a S/N of 2.8. What is
the frequency deviation caused by the noise if the
modulating frequency is 1.5KHz and the permitted
deviation is 4KHz?
What circuit is used to return the frequency response
of a signal to its normal, “flat” level?
It is the most common means of overcoming the
problems of quantizing error and noise.
____ means that the characteristics and performance
of an antenna are the same whether the antenna is
radiating or intercepting an electromagnetic signal.
Which of the following methods is used to lower the
resonant frequency of a shortened vertical antenna?
108 degrees
Θ = 360 td / T
T =1/f = 1 / 4MHz = 250 ns
Θ = 360 (75) / 250 = 108 degrees
velocity factor
m = Em/ Ec
Emax = Ec + Em ; Em = Emax – Ec = 125 – 85 = 40 V
m = 40V/ 85V = 0.47
Pt = Pc ( 1 + m2/2)
Pt = 50,000 ( 1 + 0.82 /2)
Pt = 66,000 W
Pt = 66kW
the signal is difficult to demodulate
high-level modulator
547.8 Hz
 =  fm
 = sin -1 N/S = sin -1 1/2.8 = 0.3652
 = (0.3652)(1.5KHz) = 547.8 Hz
antenna reciprocity
top hat loading
Calculate the gain (isotropic) of a parabolic antenna
that has a diameter of 3 m, an efficiency of 60% and
operates at a frequency of 4 GHz.
39.8 dBi
It is a phenomenon caused by any support insulators
used at the ends of the wire antenna.
Which of the following is not a reason why most halfwave antennas are mounted horizontally at low
The shape of the electromagnetic energy radiated
from or received by an antenna is called the
Antennas that transmit an equal amount of energy in
the horizontal direction are called
The ability of an antenna to send or receive signals
over a narrow horizontal directional range is referred
to as
A basic antenna connected to a transmission line plus
one or more additional conductors that are not
connected to the transmission line form a
An antenna made up of a driven element and one or
more parasitic elements is generally referred to as a
Which antennas usually consist of two or more halfwave dipoles mounted end to end?
A stacked collinear antenna consisting of half-wave
dipoles spaced from one another by one-half
wavelengths is the
When the characteristic impedance of the
transmission line matches the output impedance of
the transmitter and the impedance of the antenna
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
end effect
By how much should two antennas be separated for
space diversity in the 11 GHz band?
5.5 m
G =  2 D2/ 2
 = 3x108/ 4MHz = 0.075 m
G = 0.62(3)2
G= 9474.8
G = 10 log 9474.8
G = 39.8 dBi
more cost-effective
radiation pattern
parasitic array
Yagi antenna
broadside array
maximum power transfer will take place
a Q section
200  3 x 108 
200 c
d  200  
 5.5 m
11x 10
What is the phase velocity of a rectangular waveguide
with a wall separation of 3 cm and a desired
frequency of operation of 6 GHz?
5.43 x 108 m/s
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
avoid diffraction at a frequency of 11 GHz?
10.51 m
How far from the transmitter could a signal be
received if the transmitting and receiving antennas
where 40 m and 20 m, respectively, above level
44.5 km
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
An isolator has a forward loss of 0.7 dB and a return
loss of 26 dB. A source provides 1 W to the isolator,
and the load is resistive with an SWR of 3. How much
power is dissipated in the load?
An isolator has a forward loss of 0.7 dB and a return
loss of 26 dB. A source provides 1 W to the isolator,
and the load is resistive with an SWR of 3. How much
power returns to the source?
638 mW
Po u t 
0. 7
anti log
SWR  1
 0 .5
SWR  1
 851.14 mW
PLOAD  Po u t 1  2   638.35 mW
5.43 x 108 m/s
Po u t 
anti log
 851.14 mW
SWR  1
 0.5
SWR  1
PLOAD  Po u t 1  2   638.35 mW
Pre f le cte d  Po u t  2  212.78 mW
Pre tu rn e d
212.78 mW
 534.49 W
anti log
It is a microwave device that allows RF energy to
pass through in one direction with very little loss, but
absorbs RF power in the opposite direction.
A metal wrapped around the parabolic antenna
aperture to eliminate sidelobes interfering nearby
stations is called
The wavelength of a wave in a waveguide
Geostationary satellites are located at ____ with
respect to the equator.
The quality of a space-link is measured in terms of the
______ ratio.
Why does the downlink frequency appear to vary by
several kHz during a low earth orbit satellite pass?
The most ambitious LEO constellation to date is
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
The moon orbits the earth with a period of
approximately 28 days. How far away is it? Assume
circular orbit.
What is the length of the path to a geostationary
satellite from an Earth station if the angle of elevation
is 300?
39000 km
What is the nominal uplink frequency for the Ku band?
To cover all inhabited regions of the earth, the number
of polar-orbit satellites required is
A dipole antenna has a radiation resistance of 67
ohms and a loss resistance of 5 ohms, measured at
the feedpoint. Calculate the efficiency.
Two antennas have gains of 5.3 dBi and 4.5 dBd,
respectively. Which has a greater gain?
A half-wave dipole is sometimes called:
An antenna's beamwidth is measured
"Ground Effects" refers to the effects on an antenna's
radiation pattern caused by
An antenna can be matched to a feed line using
14 GHz
As the length of a "long-wire" antenna is increased
is greater than in free space
00 latitude
The distance between the satellite and ground
station is changing, causing the Doppler effect
Gain increases by 9.54 dB, beamwidth decreases
to 1/3 of its former value.
384 Mm
Efficiency = Rr / Rt = 67 / (67 + 5) = 93%
The second antenna has a higher gain.
Hertz antenna
between half-power points
radio signals reflecting off the ground
all of the choices
a. a shorted stub
b. an LC network
c. a loading coil
the number of lobes increases
LPDA stands for
Field strength at a distance from an antenna is
measured with
A receiving antenna with a built-in preamplifier
The height above mean sea level of a satellite in a
geosynchronous orbit around Earth is:
The location of a satellite is generally specified in
terms of
A point in the orbit of an object orbiting the earth that
is located closest to Earth.
Find the velocity of a satellite in a circular orbit 500 km
above the earth’s surface.
Log-Periodic Dipole Array
a field-strength meter
active antenna
35,786 km
latitude & longitude
7.6 km/s
Formula : v 
d  6400
Where : v = velocity in meters per second
d = distance above earth’s surface in km
= 7.6 km/s
(500  6400)
Find the orbital period of a satellite in a circular orbit
36,000 km above the earth’s surface if the earth’s
radius is 6400 km.
1440 mins
Formula :  
Where :
T = orbital period
C = circumference
v = orbital velocity
C = 2r
= 2 ( 6400 + 36,000 ) = 266.4 x 10 6 m
4 x1011
 3.07km/s
(36,000  6400)
C 266.4 x106 m
T 
 24hrs or 1440 mins
v 3.07x103 m /s
The outline of a communications satellite antenna
pattern on the earth is known as:
39,000 km
Calculate the length of the path to a geostationary
satellite from an earth station where the angle of
elevation is 30.(earth’s radius = 6400 km, height of
d  (r  h) 2  (r cos ) 2  r sin 
satellite above earth is 36 X 103 km)
A satellite access technique where each earth station TDMA ( Time Division Multiple Access)
transmits a short burst of information during a specific
time slot.
An earth station antenna look angle is determined by : azimuth & elevation
An ITU radiocommunication standards for satellite
services which provides information on the range of
frequencies that can be used by fixed satellite service
systems for emergency and disaster relief operations.
ITU-R S.1001-2
As per Philippine standard, frequency allocation of AM
Radio Broadcasting is from…
526.5 to 1705 kHz
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.
An AM broadcast service area in which groundwave
field of 1mV/m (60dBu) is not subject to objectionable
interference or objectionable fading.
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 level.
Regarding the design of AM antenna, what should be
the polarization of the radiator?
As per Phillipine standard, what is the minimum
frequency separation in any service area for adjacent
AM radio stations?
What is the maximum power allowable for remote
pick-up stations used as broadcast auxillary services
for AM and FM broadcast stations?
What is the classification of an FM station having an
ERP not exceeding 30kW?
What is the modulation used for the stereophonic
subcarrier of FM composite baseband signal?
What is the pilot subcarrier frequency used in FM
stereophonic transmission?
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?
Frequency allocation of FM broadcast in the
What is the color TV system adopted by the
Exact value of color subcarrier frequency (MHz) is …
Determine the visual carrier frequency of TV channel
What is the maximum allowable ERPs for channels 7
– 13 in Metro Manila and Metro Cebu?
At NTSC standard, the number of lines per frame =
________ lines/frame
At NTSC standard, line frequency = 15734.264 Hz.
What is the equivalent line period?
nighttime period
primary service area
150 ft
36 kHz
35 W
Class B
19 kHz
19.96 kW
GANT = 6 dB = 4
ERP = (5000 – 10) x 4 = 4990 x 4 = 19,960 W or
19.96 kW
88 – 108 MHz
3.579545 Mhz
187.25 MHz
186 MHz, low band frequency of channel 9
186 + 1.25 = 187.25 Mhz
1 MW
63.556 usec
fH = 15734.264 Hz
H = 1 / fH = 1 / 15734.264
Nominal RF bandwidth of NTSC TV channel…
A land mobile station used for the transmission of TV
program materials and related communications from
the scenes of events occuring at remote points from
TV broadcast station studios to TV broadcast station.
For a total capacity of 36 Mbps and 64-QAM of digital
modulation, what is the ideal RF bandwidth?
H = 63.556 x 10-6 = 63.556 usec
6 MHz
TV Pick-up station
6 MHz
What is the mode of radio wave propagation that
utilized ionosphere as a medium of transmission and /
or reception of radio signals?
What is the wavelength of a radio signal travelling at a
frequency of 220 MHz in a coaxial line having Teflon
foam as its dielectric, εr = 2?
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°?
An ionosphere layer also termed as “absorption layer”
because it absorbs most of the frequencies above 100
kHz is known as the … layer.
As per ITU-R Recc. V.431-6 Tables 1 & 2 Wavelength
Classifications, what is the classification of Super
High Frequency?
What is a diversity scheme that uses two (2) separate
antennas and receivers for each single transmitter?
What is a diversity scheme that uses two (2) different
frequencies in a simplex path?
What is the critical frequency of a layer if the
maximum value of electron density is 2 x 10 6 per cm3?
sky wave
0.96 m
Vp = Vf C
vf = 1 / sqrt (εr)
λ = vP / f = 0.96m
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°
space diversity
frequency diversity
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.
A radio communication link is to be established via 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 value for the
optimum working frequency? Use flat terrain analysis.
8.4 MHz
For flat terrain analysis, tan i = d/2h v
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 via Secant Law
The power density is inversely proportional to the
square of the distance from the source. This law is
known as…
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.
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…
OWF = 0.85 x MUF = 0.85 (9.932) = 8.4422 MHz or
8.4 MHz approx.
Inverse Square law
Radiation Pattern
The efficiency of an antenna is 82 %. Its radiation
resistance is 30 Ω. What is the value of its loss
A phenomenon on the surface of the sun with
appearance and disappearance of dark irregularly
shaped areas.
What should be done to increase the transmission
distance at frequencies higher than HF bands?
Which of the following factors must be considered in
the transmission of a surface wave to reduce
A radio station operates at 11 meter wavelength.
What is the designated band of station’s frequency?
What is the total radio horizon distance between an
80 ft transmitting station and a 20 ft receiving station?
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
6.58 Ω
η = Rd/(Rd + Rloss)
0.82 = 30/(30 + Rloss)
0.82 (30 + Rloss) = 30 = 24.6 + 0.82 Rloss
Rloss = (30 – 24.6) / 0.82 = 6.5854 Ω or 6.58 Ω approx.
11-year sunspot
increase antenna height
All of the choices
a. electrical properties of the terrain
b. frequency
c. antenna polarization
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
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
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
PFED = PR / GANT = 4.93 / 1.64 = 3.007 W or
3 W approx.
Identical telephone numbers in different parts of a
country are distinguished by their ___.
area codes
Telephone traffic is measured ____.
in erlangs
In a cellular telephone system, each cell site contains
a ____.
When the signal from a mobile cellular unit drops
below a certain level, what action occurs?
the unit is “handed off” to a closer cell
In a cellular telephone system, group of cells is called
In Celluar Telephone Systems, these are
transmissions from base stations to mobile units
forward links
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?
A telephone signal takes 2ms to reach its destination.
Calculate the via net loss required for an acceptable
amount of echo.
250 mW
PT = -76 dB - PR
PT = transmitted power in dBm
PR = received power in dBm
PT = -76 dB - PR
= -76 dB – (-100dBm)
= 24 dBm
= 250 mW
0.8 dB
VNL = 0.2t + 0.4 dB
= 0.2 X 2 + 0.4
= 0.8 dB
The typical voltage across a telephone when on-hook
Central offices are connected by:
48 volts DC
In telephony, call blocking is:
occurs when the central office capacity is
The cable used for local loops in telephone system is
In DTMF, the four vertical frequencies are ____.
twisted-pair copper wire
In DTMF, the Horizontal frequencies are
1209Hz, 1336Hz,1477Hz,1633Hz
In Celluar Telephone Systems, these are
transmissions from mobile units to base stations
In DTMF, the horizontal frequencies is also known as
reverse links
In DTMF, the Vertical frequencies is also known as
low group frequencies
The bandwidth of voice-grade signals on a telephone
system is restricted in order to:
This is the highest-ranking office in the DDD network
in telephony in terms of the size of the geographical
area served and the trunking options available.
In Cellular Radio, AMPS stand for:
allow signals to be multiplexed
In Cellular Radio, BSC stands for:
Base Station Controller
In Cellular Radio, MSC stands for:
Mobile Switching Center
In GSM, voice channels are called:
traffic channels
In Mobile Communications, GSM uses:
frequency hopping
In Mobile Communications, IMSI stands for:
International Mobile Subscriber Identification
An acoustical phenomenon wherein the sound
continues to persist after the cause of sound has
stopped resulting in repeated reflections is called…
trunk lines
high group frequencies
regional center
Advanced Mobile Phone Service
A group of filters has 1/3 octave of spacing. If the
initial frequency is 25 Hz, what is the next frequency
available for the filter?
+ 26 dBu is how many volts?
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
Determine the sound power in Watts produced by the
bank’s alarm if a by-stander heard the alarm at a
sound pressure level of 100 dB-SPL. The by-stander
is 100 ft away from the bank.
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?
A number from 0 to 1 representing the ability of a
surface material to absorb sound energy is known
The difference in dB between the loudest level of
sound and the softest passage of sound is known as
The highest frequency that can be used for skywave
propagation between two specific points on earth’s
Variation in signal loss caused by natural weather
Determine the radio horizon for a transmit antenna
that is 200 m high and a receiving antenna that is 100
m high
The height above the earth’s surface from which a
refracted wave appears to have been reflected…
Electromagnetic waves that are directed above the
horizon level.
The most common light used in fiber-optic links is
In the telecommunications industry, the most
commonly used fiber(s) are
The abrupt change in refractive index from core to
cladding of fiber-optic cable is called the
A technique that is used to minimize the pulse
dispersion effect is to
31.5 Hz
f2 = 2x f1 where x = 1/3, fraction of an octave
f2 = 21/3 x 25 = 31.5 Hz
15.5 V
V (dBu) = 20 log [ voltage in Volts / 0.775 Volts ]
26 = 20 log [ voltage in Volts / 0.775 V ]
26 / 20 = log [ voltage in Volts / 0.775 V ] = 1.3
Voltage = log-1 (1.3) x 0.775 V
Voltage = 15.5 V
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
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 dBSPL
Absorption Coefficient
dynamic range
Critical Frequency
99.5 km
D = √ 17ht + √ 17hr
= √ 17(200) + √ 17(100)
= 99.5 km
virtual height
sky waves
50 and 62.5 micron
Step index
Minimize the core diameter
Which is not an important characteristic of a light
The dispersion of light in fiber-optic cable caused by a
portion of the light energy traveling in the cladding is
Recent laser developments for fiber-optic
communication include
Which of the following considerations is important
when deciding between using a diode laser or an
In 1815, the correct explanation of diffraction was
given by
It is the central part of the optical communication
The light energy that is always emitted or absorbed in
discrete units
Which of the following Ethernet fiber optic standard
uses synchronous, Centralized Clock?
It is a mixed, multiple-service standard to allow the
transmission of voice and video over an FDDJ
It is a layer of plastic that surrounds a fiber or group of
The angular separation between the two half-power
points on the power density radiation pattern.
Refers to the direction in space of electric vector of
the electromagnetic wave radiated from an antenna
and is parallel to the antenna itself.
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?
What principle that states that the properties of an
antenna are independent of whether it is used for
transmission or reception.
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
This is often used to cure the problem of great
thickness required of lenses used at lower microwave
frequencies or for strong curved wavefronts.
A structure-generally metallic and sometimes very
complex-designed to provide an efficient coupling
between space and the output of a transmitter or input
to a receiver.
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.
Any array that is directional at right angles to the
plane of the array is said, by inference, to have ____.
The ratio of the focal length to the mouth diameter is
called __________ of the parabola, just as in camera
Power consumption
Waveguide dispersion
Distributed feedback (DFB) and vertical cavity
surface emitting (VCSEL)
Response time
Optical Fiber
10 Base-FB (Backbone)
Buffer Tube
Top loading
Principle of reciprocity
Directive gain
Broadside action
Corresponds to a resonant transmission line, and the
dipole antennas describe so far have been resonant.
An optic fiber is made of glass with a refractive index
of 1.55 and is clad with another glass with a refractive
index of 1.51. Launching takes place from air. What
numerical aperture does the fiber have?
An optic fiber is made of glass with a refractive index
of 1.55 and is clad with another glass with a refractive
index of 1.51. Launching takes place from air. What is
the acceptance angle?
For a single-mode optical cable with 0.25-dB/km loss,
determine the optical power 100km from a 0.1-mW
light source.
For an optical fiber 10km long with a pulse-spreading
constant of 5ns/km, determine the maximum digital
transmission rates for return-to-zero.
In fiber optics, it is a measure of the conversion
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
A phenomenon also called stress corrosion resulting if
the glass fiber is exposed to long periods of high
The theory which states that when visible light or highfrequency electromagnetic radiation illuminates a
metallic surface, electrons are emitted.
The science of measuring only light waves that are
visible to the human eye
The process of constructing an ILD that is similar to
LED except that the ends are highly polished.
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.
For an electronic device operating at a temperature of
17°C with a bandwidth of 10 kHz, determine the
thermal noise power in dBm .
Resonant antenna
= 0.352
= 0.352
Θ0(max)=sin-1NA= sin-10.352=20.6◦
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)
P(dBm)= 10log
= -35dBm
Static fatigue
Planck’s law
Pulse spreading
N(dBm) = 10log (4 x 10-17) = -134 dBm
A 300Ω resistor is connected across the 300Ω
antenna input of a television receiver. The bandwidth
of the receiver is 6MHz, and the resistor is at room
temperature .Find the noise voltage applied to the
receiver input.
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?
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
(S/N)p = 100µW
(S/N)o = 1W
NF (ratio) = 100
It is desired to operate a receiver with NF = 8dB at
S/N = 15 dB over a 200-KHz bandwidth at ambient
temperature. Calculate the receiver’s sensitivity.
A Satellite receiving 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 receiver’s input
over a 1-MHz frequency range?
Equivalent temperature of a passive system having
the same noise power output of a given system.
The noise voltage produced across a 50Ω is input
resistance at a temperature of 302°C with a
bandwidth of 6 MHz is ______.
1.75 x 10-15
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
= 33.3
S = Sensitivity = -74dBm + NF + 10log∆f + desired
S = -174 + 8 + 10log(200,000) + 15
S = -98 dBm
PN = KT∆f
= 1.38 x 10-23 J/K (35 + 40 + 52)K (1MHz)
= 1.75 x 10-15 W
noise temperature
VN =
= 4(1.38 x 10-23)(302)(6 x 106)(50)
= 2.24µV
ᵟ = φ x fi
= 0.5 x 5 kHz = 2.5 kHz
75 kHz
2.5 kHz
The technique that uses the BPSK vector relationship
to generate an output with logical 0s and 1s
determined by comparing the phase of two
successive data bits is
A special digital modulation technique that achieves
high data rates in limited-bandwidth channels is called
FSK systems are much superior to two-tone
amplitude-modulation systems with respect to
Using an oscilloscope to display overlayed received
data bits that provide information on noise, jitter, and
linearity is called a(n)
The type of radio transmission that uses
pseudorandomly switched transmissions is known as
The acronym CDMA refers to ________.
= 100
= 30
Quadrature amplitude modulation (QAM)
Ionospheric fading characteristics
Eye pattern
Spread spectrum
Code-division multiple-access systems
The acronym OFDM refers to ________.
Orthogonal Frequency Division Multiplexing
Using radio to transmit gathered data on some
particular phenomenon without human monitors is
known as
The acronym for the form of data transmission in
which the modulating wave shifts the output between
two predetermined frequencies is _____.
Pseudorandom implies a sequence that can be _____
but has the properties of randomness.
______ implies that both analog and digital signals
share the same channel bandwidth.
Telemetry may be defined as _____ metering.
Radio telemetry
Which is not a type of pulse modulation?
Pulse-frequency modulation (PFM)
PPM and PWM are superior to PAM systems in
Noise characteristics
A procedure that decides which device has
permission to transmit at a given time is called
The major difficulty faced by delta modulators is
Line control
The AT&T T1 lines
Use 8-bit PCM code and include 24 voice channels
The ground wire in a USB cable is ______.
A(n) ________ is used to allow a digital signal to be
transmitted on an analog channel.
The bit ________ is the amount of power in a digital
bit for a given amount of time.
The relationship for bit rate to ________ bandwidth is
defined by the Shannon-Hartley theorem.
In an S/H circuit, the time that it must hold the
sampled voltage is
Error signals associated with the sampling process
are called
A(n) ________ is a single LSI chip containing both the
ADC and DAC circuitry.
The NRZ digital signal-encoding format has a
________ component in the waveform.
Reed–Solomon codes utilize a technique called
________ to rearrange the data into a nonlinear
ordering scheme to improve the chance of data
The electric field intensity is measured in:
It is a result of an increase in the charge density in
dielectric materials.
It refers to the maximum antenna gain.
The maximum horizontal distance between the
transmitter and the receiver for line of sight
propagation is known as:
Typical mode of radiation of helical antenna is:
radio horizon
Slope overload
Aperture time
Foldover distortion and aliasing
end fire
The electric field is perpendicular to the earth’s
surface, the polarization is:
In what major RF band is ground wave basically
A measure of mismatch in a transmission line
The highest frequency that can be set back to earth
by the ionosphere, if wave is sent vertically upward.
Travel in a straight line from the transmitting antenna
to the receiving antenna.
VLF waves are for some types of services because
critical frequency
It is the distance between two wave fronts having the
same phase at any given instant.
It is a piece of transmission line which is normally
short-circuited at the far end.
A 50 ohms transmission line is connected to a 30 ohm
resistive load. Calculate the reflection coefficient.
The characteristic impedance of a transmission line
does not depend upon its
Characteristic impedance of a transmission line is the
impedance measured at the _______ when its length
is infinite.
Which region of the ionosphere is mainly responsible
for long-distance night time communications?
Which is properly terminated antenna?
MF (Medium Frequency)
standing wave ratio
space wave
they are very reliable
Ref Coeff = (30 – 50)/(30 + 50) = 0.25
F layer
Occurs when the radio beam is at point of grazing
over an obstacle.
A microwave communications system, space loss
calculation formula is
Is an OSI Layer which is responsible for providing
error-free communications across the physical link
connecting primary and secondary stations (nodes)
Data Link layer
Is the ratio of the largest possible magnitude to the
smallest possible magnitude that can be decoded by
the digital-to-analog converter.
Is a PCM system which uses a single bit PCM code to
achieve digital transmission of analog signals.
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.
Is an n-bit data register inside the UART that keeps
track of the UART’s transmit and receive buffer
Is an access method used primarily with LANs
configured in a bus topology.
IP version 4 address length is
Dynamic range
Is a multiport bridge that provides bridging function.
92.4 + 20log F + 20 log D
Delta modulation
Longitudinal redundancy check
Status Word register
32 bits
Is a device which operates in the Network layer and it
makes forwarding decisions on the basis of network
OC-1 (STS-1) line rate is
Is one in which all computers share their resources
with all the other computers on the network.
Peer-to-peer client/server network
Is used to interface DTEs to digital transmission
Channel service unit
Modulation which combines encoding and modulation
to reduce the probability of error.
Is an empirical record of a system’s actual bit error
Is an error-correcting code used for correcting
transmission errors in synchronous data streams.
Hamming code
51.84 Mbps