Question Answer

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?

1.1%

A type of luminescence where the visible light is emitted only during the stimulation of the phosphor.

Fluorescence

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?

1.18

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

Bucky factor

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?

42 kW

Who completes the development of first computed tomographic (CT) scanner (EMI, Ltd.) in 1973?

Hounsfield

It is the study of the response of an image receptor to x-rays

Sensitometry

Ratio of radiographic contrast with a grid to that without a grid.

contrast improvement factor

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

600 rad

ECG recording requires a bandwidth of 0.05 to ____ Hz

100

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 second.

309 uV

Period during which heart contracts. Systole

Apparatus for measuring blood pressure Sphygmomanometer

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.

Photoelectric effect

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).

Roentgen

An optical electronic device that measures the color concentration of a substance in solution.

colorimeter

Recording of heart sounds phonocardiography

Recorder for measuring galvanic skin resistance

electrodermograph

It consists of 36 unique codes representing the 10 digits and 26 uppercase letters.

code 39

The first fixed- length character code developed for machines rather than for people

Baudot Code

The early pioneer in the development of error-detection and correction procedures

Richard W. Hamming

The most reliable convolutional coding scheme for error detection

CRC

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

22.2 dB

;

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 produced?

0.876Vmax

Inaccuracies caused by the representation of a continuously varying quantity as one of a number of discrete values.

quantizing errors

Circuit for digitizing voice at a low data rate by using knowledge of the way in which voice sounds are produced

vocoder

A coding scheme that records the change in signal level since the precious sample

delta modulation

Distortion created by using too low a sampling rate when coding an analog signal for digital transmission

either a or b

a. aliasing b. foldover distortion

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?

2 Mbps

= 2 Mbps

A telephone subscriber line must have an SNRdB above 40. What is the minimum number of bits?

6.35

SNRdB = 6.02nb + 1.76 = 40 n = 6.35

The thick coaxial cable implementation of standard Ethernet

10 Base 5

A bit pattern or a character added to the beginning and the end of a frame to separate the frames

Flag

An IPv4 has an address space of how many? 4294967296

232 = 4294967296

What is the bit rate of STS – 1? 51.84 Mbps

A block coding technique in which four bits are encoded into a five bit code

4B/5B Encoding

A national standards organization that defines standards in the United States

ANSI

In asynchronous transmission, one or more bits to indicate the end of transmission

stop bit

What is the overhead (number of extra bits) in the DS-3 service?

1.368 Mbps

The minimum sampling rate according to Nyquist Theorem

twice the highest frequency of a signal

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

spread spectrum

An error detection method which uses one’s complement arithmetic

Checksum

It is a connecting device between two internetworks that use different models

Gateway

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

Jitter

In PCM system, it is the ratio of the maximum input voltage level to the smallest voltage level that can be quantized

Dynamic range

A multiplexer combines four 100-kbps channels using a time slot of 2 bits, determine the frame duration.

20s

The link carries 50,000 frames /sec

The frame duration = 1/50,000 = 20s

Determine the Hamming distance for the codewords (10101, 11001)

Two 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 is the address space of IPv6?

2128

It is a standard designed by ITU to allow telephones in the public telephone network to talk to computers/terminals connected to the internet

H.323

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?

12 Megabits 1,200 times 1000 pixels x 10 bits = 12 Mb 1024 colors requires 10 bits , 210 = 1024

Combination of compression at the transmitter and expansion at the receiver of communications system.

Companding

A device launches or receives a wave in a transmission line or waveguide in one direction only.

directional coupler

A type of linear-beam microwave tube that uses velocity modulation of the electron beam

Klystron

A series of pulses in which the amplitude of each pulse represents the amplitude of the information signal at a given time.

PAM

_______________ is used to position samples of the different message signals in non-overlapping time slots.

TDM

A ___________ is similar to a phasor diagram except that the entire phasor is not drawn.

constellation diagram

It was the first fixed length character code. Baudot Code

It involves transmitting each character twice. Redundancy

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.

Central Limit Theorem

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.

Asynchronous transfer mode (ATM)

A series of pulses, in which the timing of each pulse represents the ampltitude of the information signal at a given time.

Pulse Position Modulation

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?

11.6m

R = 11.6m

Variation in received field strength over time due to changes in propagation conditions.

Fading

The atomic weight of an element is approximately determined by

the number of protons

Of the following substances the worst conductor is Air

The volt is the standard unit of electromotive force

Which of the following antenna types is not designed for transmitting at 10 Ghz

Zepp antenna

The type of radio wave responsible for long distance communications by multiple skips is the:

Direct Wave

Line of sight communications is not a factor in which frequency range?

HF

It refers to the rate of change of a signal on the transmission medium after encoding and modulation have occurred.

Baud

It was the first fixed-length character code developed for machines rather than people.

Baudot Code

A receiver-transmitter station used to increase the communications range of VHF, UHF and microwave signals is called a(n):

Repeater

It represents the simplest whole number ratio of the various types of atoms in a compound.

empirical formula

It is a term that is often misunderstood and commonly confused with bit rate (bps)

Baud

Defined as the optimum level of a test tone on a channel at same point in a communication system.

transmission level point

Duplicating each data unit for the purpose of detecting errors is a form of error detection called ______.

Redundancy

Determine the wavelength of a 4 Ghz signal. 0.075m

What is the device that converts energy from one form to another?

Transducer

It may be defined as any undesired voltages or currents that ultimately end up appearing in the receiver output.

Electrical noise

The channel capacity of a 5 kHz bandwidth binary system is ____ bits/s. Assuming no noise.

10,000

Microwaves are frequencies above _____ GHz. 1

The government agencies that regulates radio communications in the US is the ________.

FCC

A wave guide acts a/an _______ filter High-pass

Coax is not used beyond frequencies of about ______ GHz.

6

Data Communications refers to the transmission of _______.

all of the above a. voice b. video c. Computer data

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.

1 kHz

It is often used to compare the performance of one digital modulation technique to another.

bandwidth efficiency

It is the process of converting an infinite number of possibilities to a finite number of conditions.

Quantization

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.

Checksum

It is a modulation and multiplexing technique that distributes the signal and its sidebands over a very wide bandwidth.

Spread spectrum

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 network.

Servers

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.

Broadband ISDN

It is the only error-correction scheme that actually detects and corrects transmission errors when they are received without requiring a transmission..

Forward Error Correction

This OSI Layer is responsible for network availability, data storage and processor capacity. It also determines the type of dialogue available.

Session layer

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.

free space path loss

What do you call the accumulation of additional sounds such as wind, street noise, other voices that contribute to what the listener hear?

Ambience

It is a single transmission path from transmitter to receiver with line of sight range.

Hop

It is defined by the average rate at which energy is carried out per unit area.

Intensity

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?

the frequency of the wave stays the same while the wavelength changes.

The process of combining multiple audio signals into one track is called?

audio mixing

The speed of sequence of musical notes is called? Tempo

If the frequency of a sound is increased, what will happen to its pitch?

Increases

A type of microwave protection system where each working channel has a dedicated back up or spare channel.

Hot Standby

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.

signal quality detector

______ which means that 2 or more bits in the data unit have changed.?

burst error

It is a four-wire Gigabit Ethernet implementation. 1000 Base-T

It is a digital process that allows several connections to share the high bandwidth of a link.

TDM

EEE 802.11 is define in which MAC sublayer? (b) and (c) B. PCF C. DCF

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.

Magnetron

A modulation process wherein both frequence and phase remains constant while the amplitude changes.

ASK

It is the most powerful redundancy checking technique which is based on binary division.

cyclic redundancy check

What do you call the element with electrical properties between those of an insulator and a conductor?

Semiconductor

In pulse-code modulation, it translates the quantized samples into digital code words.

Encoder

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.

vertical redundancy check

A local area network topology in which the individual terminal, microcomputers or workstations are connected directly to a central computer.

Star

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

quadrature amplitude modulation

Find the maximum dynamic range for a linear PCM system using 16-bit quantizing.

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 signal.

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

VNL = 0.2t + 0.4dB VNL = 0.2 (2ms) + 0.4 dB VNL = 0.8 dB

Telephone switch that connects only to other switches, and not to individual customers.

tandem office

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.

QAM

The most common circuit used for demodulating binary FSK signals.

PLL

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.

8 KHz

BW = 2 x 4 KHz = 8 KHz

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.

40

BW=10x4 = 40 MHz

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

= 7.63 = 8

A network topology in which data circulates from one computer to the next in sequence.

Ring

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 pressed?

852 Hz and 1336 Hz

It is a means of transmitting data by shifting the phase angle of the transmitted signal.

PSK

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.

OSI

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.

Crosstalk

What type of digital modulation scheme uses two or more different output frequencies?

FSK

It is an error-correcting code used for correcting transmission errors in synchronous data streams.

Hamming Code

A suite of protocols that allows a wide variety of computers to share the same network.

TCP/IP

Noise that is primarily caused by lightning. Often called as Static Noise.

atmospheric noise

A modulation technique in which the frequency of the modulated signal varies with the amplitude of the modulating signal

AM

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.

FSK

The highest layer in the hierarchy and is analogous to the general manager of the network by providing access to the OSI environment.

Application layer

What is the equation for Hartley’s Law? I=ktB

Network topology wherein individual terminals, microcomputers and workstations are connected directly to a central computer.

Star

The loss of data that occurs when two stations transmit at the same time on a network

Collision

A term used to describe a telephone instrument whose handset is on its cradle, ready to receive a ring signal.

On hook

The most commonly used digital modulation scheme. PCM

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.

Checksum

Is an eight-bit fixed length character set developed in 1962 by the International Business Machines Corporation.

EBCDIC code

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.

14.1KHz

fa = fs – fm = 44.1KHz – 30KHz = 14.1 KHz

Calculate the capacity of a telephone channel that has a S/N of 1023?

30,000 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

Designed to send characters of the message with the specified bit rate but without any fixed timing relationship from one character to the next.

asynchronous

Token Ring Standard 802.5

It is the process of extracting a phase-coherent reference carrier from a receiver signal.

Carrier Recovery

It is a potential problem whenever two metallic conductors carrying different signals are located in close proximity to each other.

Crosstalk

What is the termed refer as the rapid degradation of output signal quality with channel induced errors?

threshold effect

What was the first fixed-length character code developed for machines rather than for people?

Baudot code

A source whose output satisfies the condition of statistical independence among letters in the sequence is said to be_____.

Memoryless

Calculate the minimum data rate needed to transmit audio with sampling rate of 30 Khz and 14 bits per sample.

420 Kb/s

Handles error recovery, flow control (synchronization), and sequencing (which terminals are sending and which are receiving). It is considered the “media access control layer”.

Data Link Layer

A MAC protocol for LANs, with stations connected topologically or logically in a ring. Or the IEEE 802.5 LAN standard.

Token Ring

A network topology where each device is connected to a centre point and all data is routed through that point.

Star network

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

Liquid Lasers

Codes that have a restriction on the number of consecutive 1s or 0s in a sequence.

Run length limited code

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

Preamble

Every letter was encoded into fixed length of binary code words of length 5.

Baudot Code

The composite signal that modulates the FM carrier. Baseband

It is a simple means of error detection. It involves the addition of one extra bit to the bits that encode a character.

Parity

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.

Huffman coding

Speed at which symbols are transmitted in a digital communication systems.

Baud rate

It is the process of converting an infinite number of possibilities to a finite number of conditions.

Quantization

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 receiver.

Dynamic Range

It is the institution that developed the ASCII (American Standard Code for Information Intertchange).

ANSI

In early 1900s, he showed that any composite signal is a sum of a set of sine waves of different frequencies, phases and amplitudes.

Jean-Baptiste Fourier

Find the binary equivalent of x8+x3+x+1. 100001011

x8+x7+x6+x5+x4+x3+x2+x+k 1 0 0 0 0 1 0 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. 8000 bps

bit rate = baud * 4 2000 * 4 = 8000 bps

It is an electronic device that is used for computer communications through telephone lines.

Modem

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

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

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.

Harry Nyquist

Find the maximum dynamic range for a linear PCM system using 8-bit quantizing.

49.92 dB

DR = 1.76 + 6.02m dB = 1.76 + 6.02(8) dB = 49.92 dB

In operation, many modern codecs achieved compresion by first encoding the signals using a 12-bit 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:

Digital Signal Processing

Sampling of an analog signal using a sample-and-hold circuit such that the sample has the same amplitude for its whole duration.

Flat-topped Sampling

The basic building block of the FDM hierarchy. Message Channel

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.

135.4165kHz

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

For Ethernet system with a length of 2.5km on coaxial cable with a velocity factor of 0.66. What is the propagation delay?

12.6µs

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?

0.876 Vo

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

A telephone signal take 2ms to reach its destination. Calculate the via net loss required for an acceptable amount of echo.

0.8 dB

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

Who invented the telegraph? Samuel F.B Morse

The simplest modulation technique, where a binary information signal modulates the amplitude of an analog carrier.

Amplitude-Shift Keying

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.

Physical Layer

Error-correction scheme that actually detect and corrects transmission errors when they are received without requiring a retransmission.

Forward Error Correction

It allows the overall complexity of the system to be broken down into individual function –layers- that operate essentially by themselves.

Transparency

This are very useful pictorial representations that clearly show the protocol operations such as words or convetional drawings.

State Transition Diagram

Pair of wires that connects the central office to the users phone

Local loop

How long does it take to dial the number 784-3745 using pulse dialing with .5s inter digit time?

6.8s 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

LAN

In operation, many modern codecs achieved compresion by first encoding the signals using a 12-bit 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:

Digital Signal Processing

A balanced modulator that will used in conjuction with a microwave generator, power amplifier, and band-pass filter, up-converts the IF carrier to an RF carrier and amplifies the RF to the desired output power.

Transmit Modulator

What is the equation for Hartley’s Law? I=ktB

The loss of data that occurs when two stations transmit at the same time on a network

Collision

We have an audio signal with a bandwidth of 5 HHz. What is the bandwidth modulate the signal using FM? Ignore FCC regulation.

50 MHz BW= 10 x 5MHz =50MHZ

Used to established a point to point connection across a network.

TCP

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?

19.1kHz

fa = fs - fm

= 44.1kHz – 25kHz = 19.1kHz

Defines the rules of the conversation the message passing among the network users

network protocol

Responsible for providing signals to the loop sensing activity and sending phone signals at the end of the loop

SLIC

The typical amount of voltage in dc use in the battery of the central office with respect to ground

-48

A network that is composed of a smaller lan that are closely link. It is needed for areas spread out geographically

WAN

How many central office allotted for each exchange? 1

It is a method of switching that provides a separate physical path for each symbol

space switching

The central office detects a request for service from a telephone by:

a flow of loop current

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.

Transport

It is used on long – distance circuits, in an effort to overcome echoes caused by circuit imbalances.

Echo Suppresors

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?

23 dBm

dBm for 200 mW = 10 log (200mW/1mW) = 23 dBm

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 system.

3.6 dB

modulation index of an AM radio station is 0.75. If the carrier power is 500W, what is the total transmitted power?

641 W

21

2mPcPt

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?

72

A/an _______ is a range of frequency in which the upper frequency is double the lower frequency.

Octave

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.

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

A small variable capacitance in parallel with each section of ganged capacitor is called _______.

Trimmer

How many wavelengths long are required for a pair of conductors to be considered as a transmission line?

1/10λ

Determine the time taken for a signal to travel down a 10 m transmission line, if its velocity factor is 0.7.

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?

26%

At exactly one-quarter wavelength, the short-circuited transmission line behaves as a(an) ________ circuit.

parallel-resonant

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.

108 degrees

Θ = 360 td / T T =1/f = 1 / 4MHz = 250 ns Θ = 360 (75) / 250 = 108 degrees

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?

Microstrip

One complete revolution around a Smith Chart represents _________ wavelengths.

½ λ

A mismatched transmission line is also referred to as a ___________ line.

Resonant

It is the ratio of the speed of propagation on a line to that of light in free-space.

velocity factor

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?

CAT 5

The modulated peak value of a signal is 125V and the unmodulated carrier value is 85V. What is the modulation index?

0.47

m = Em/ Ec Emax = Ec + Em ; Em = Emax – Ec = 125 – 85 = 40 V m = 40V/ 85V = 0.47

The total transmitted power of an AM broadcast transmitter with a carrier power of 50kW when modulated 80 percent is:

66kW

Pt = Pc ( 1 + m2/2) Pt = 50,000 ( 1 + 0.82 /2) Pt = 66,000 W Pt = 66kW

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?

the signal is difficult to demodulate

If the input in a transmitter is collector-modulated, the system is called a _______________________.

high-level modulator

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?

547.8 Hz

= fm

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

= (0.3652)(1.5KHz) = 547.8 Hz

What circuit is used to return the frequency response of a signal to its normal, “flat” level?

de-emphasis

It is the most common means of overcoming the problems of quantizing error and noise.

Companding

____ means that the characteristics and performance of an antenna are the same whether the antenna is radiating or intercepting an electromagnetic signal.

antenna reciprocity

Which of the following methods is used to lower the resonant frequency of a shortened vertical antenna?

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

G = 2 D2/ 2

= 3x108/ 4MHz = 0.075 m

G = 0.62(3)2 0.0752 G= 9474.8 G = 10 log 9474.8 G = 39.8 dBi

It is a phenomenon caused by any support insulators used at the ends of the wire antenna.

end effect

Which of the following is not a reason why most half-wave antennas are mounted horizontally at low frequencies?

more cost-effective

The shape of the electromagnetic energy radiated from or received by an antenna is called the

radiation pattern

Antennas that transmit an equal amount of energy in the horizontal direction are called

Omnidirectional

The ability of an antenna to send or receive signals over a narrow horizontal directional range is referred to as

Directivity

A basic antenna connected to a transmission line plus one or more additional conductors that are not connected to the transmission line form a

parasitic array

An antenna made up of a driven element and one or more parasitic elements is generally referred to as a

Yagi antenna

Which antennas usually consist of two or more half-wave dipoles mounted end to end?

Collinear

A stacked collinear antenna consisting of half-wave dipoles spaced from one another by one-half wavelengths is the

broadside array

When the characteristic impedance of the transmission line matches the output impedance of the transmitter and the impedance of the antenna itself,

maximum power transfer will take place

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

a Q section

By how much should two antennas be separated for space diversity in the 11 GHz band?

5.5 m

m

sx

s

mx

f

cd 5.5

1011

103200200

2009

8

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 terrain?

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

TE20

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?

638 mW

mWPP

SWR

SWR

mW

anti

WP

outLOAD

out

35.6381

5.01

1

14.851

10

7.0log

1

2

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?

5.43 x 108 m/s

W

anti

mWP

mWPP

mWPP

SWR

SWR

mW

anti

WP

re tu rne d

outre f le cte d

outLOAD

out

49.534

10

26log

78.212

78.212

35.6381

5.01

1

14.851

10

7.0log

1

2

2

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.

isolator

A metal wrapped around the parabolic antenna aperture to eliminate sidelobes interfering nearby stations is called

Shroud

The wavelength of a wave in a waveguide _________.

is greater than in free space

Geostationary satellites are located at ____ with respect to the equator.

00 latitude

The quality of a space-link is measured in terms of the ______ ratio.

G/T

Why does the downlink frequency appear to vary by several kHz during a low earth orbit satellite pass?

The distance between the satellite and ground station is changing, causing the Doppler effect

The most ambitious LEO constellation to date is ______.

Teledesic

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?

Gain increases by 9.54 dB, beamwidth decreases to 1/3 of its former value.

The moon orbits the earth with a period of approximately 28 days. How far away is it? Assume circular orbit.

384 Mm

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? 14 GHz

To cover all inhabited regions of the earth, the number of polar-orbit satellites required is

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.

93%

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

Two antennas have gains of 5.3 dBi and 4.5 dBd, respectively. Which has a greater gain?

The second antenna has a higher gain.

A half-wave dipole is sometimes called: Hertz antenna

An antenna's beamwidth is measured between half-power points

"Ground Effects" refers to the effects on an antenna's radiation pattern caused by

radio signals reflecting off the ground

An antenna can be matched to a feed line using all of the choices

a. a shorted stub b. an LC network c. a loading coil

As the length of a "long-wire" antenna is increased the number of lobes increases

LPDA stands for Log-Periodic Dipole Array

Field strength at a distance from an antenna is measured with

a field-strength meter

A receiving antenna with a built-in preamplifier active antenna

The height above mean sea level of a satellite in a geosynchronous orbit around Earth is:

35,786 km

The location of a satellite is generally specified in terms of

latitude & longitude

A point in the orbit of an object orbiting the earth that is located closest to Earth.

Perigee

Find the velocity of a satellite in a circular orbit 500 km above the earth’s surface.

7.6 km/s

Formula :

v 4x1011

d 6400

Where : v = velocity in meters per second d = distance above earth’s surface in km

v 4x1011

(500 6400) = 7.6 km/s

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 :

C

v

Where : T = orbital period C = circumference v = orbital velocity

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 mins

The outline of a communications satellite antenna pattern on the earth is known as:

Footprint

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 satellite above earth is 36 X 103 km)

39,000 km

d (r h)2 (rcos)2 rsin

A satellite access technique where each earth station transmits a short burst of information during a specific time slot.

TDMA ( Time Division Multiple Access)

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.

nighttime period

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

primary service area

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.

150 ft

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

Vertical

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

36 kHz

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

35 W

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

Class B

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

AM DSB SC

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

19 kHz

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?

19.96 kW

GANT = 6 dB = 4

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

Frequency allocation of FM broadcast in the Philippines…

88 – 108 MHz

What is the color TV system adopted by the Philippines?

NTSC

Exact value of color subcarrier frequency (MHz) is … 3.579545 Mhz

Determine the visual carrier frequency of TV channel 9.

187.25 MHz

186 MHz, low band frequency of channel 9 186 + 1.25 = 187.25 Mhz

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

1 MW

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

525

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

63.556 usec

fH = 15734.264 Hz

H = 1 / fH = 1 / 15734.264

H = 63.556 x 10-6 = 63.556 usec

Nominal RF bandwidth of NTSC TV channel… 6 MHz

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.

TV Pick-up station

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

6 MHz

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

sky wave

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?

0.96 m

Vp = Vf C vf = 1 / sqrt (εr) λ = vP / f = 0.96m

What is the angle of refraction in a Teflon (εr2 = 2) medium of a radio wave from air (εr1 = 1.0) if its angle of incidence is 45°?

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°

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

D

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

Centimetric

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

space diversity

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

frequency diversity

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

13 MHz

Nmax = 2 x 106 per cm

3 = 2 x 10

6 x 10

6 per m

3 = 2 x 10

12 per m

3

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/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 via Secant Law

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

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

Inverse Square law

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.

E

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…

Radiation Pattern

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

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.

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

11-year sunspot

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

increase antenna height

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

All of the choices

a. electrical properties of the terrain b. frequency c. antenna polarization

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

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

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

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

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?

3 W

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.

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 ____.

Repeater

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 ___.

Cluster

In Celluar Telephone Systems, these are transmissions from base stations to mobile units (Downlink)

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?

250 mW PT = -76 dB - PR

Where: PT = transmitted power in dBm PR = received power in dBm PT = -76 dB - PR

= -76 dB – (-100dBm) = 24 dBm = 250 mW

A telephone signal takes 2ms to reach its destination. Calculate the via net loss required for an acceptable amount of echo.

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 is:

48 volts DC

Central offices are connected by:

trunk lines

In telephony, call blocking is: occurs when the central office capacity is exceeded

The cable used for local loops in telephone system is mainly:

twisted-pair copper wire

In DTMF, the four vertical frequencies are ____.

697Hz,770Hz,852Hz,941Hz

In DTMF, the Horizontal frequencies are

1209Hz, 1336Hz,1477Hz,1633Hz

In Celluar Telephone Systems, these are transmissions from mobile units to base stations (Uplink)

reverse links

In DTMF, the horizontal frequencies is also known as

high group frequencies

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:

allow signals to be multiplexed

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.

regional center

In Cellular Radio, AMPS stand for:

Advanced Mobile Phone Service

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…

Reverberation

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?

31.5 Hz f2 = 2x f1 where x = 1/3, fraction of an octave f2 = 21/3 x 25 = 31.5 Hz

+ 26 dBu is how many volts? 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

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

Condenser

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.

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

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?

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

A number from 0 to 1 representing the ability of a surface material to absorb sound energy is known as…

Absorption Coefficient

The difference in dB between the loudest level of sound and the softest passage of sound is known as _

dynamic range

The highest frequency that can be used for skywave propagation between two specific points on earth’s surface.

Critical Frequency

Variation in signal loss caused by natural weather disturbances.

Fading

Determine the radio horizon for a transmit antenna that is 200 m high and a receiving antenna that is 100 m high

99.5 km D = √ 17ht + √ 17hr = √ 17(200) + √ 17(100) = 99.5 km

The height above the earth’s surface from which a refracted wave appears to have been reflected…

virtual height

Electromagnetic waves that are directed above the horizon level.

sky waves

The most common light used in fiber-optic links is Infrared

In the telecommunications industry, the most commonly used fiber(s) are

50 and 62.5 micron

The abrupt change in refractive index from core to cladding of fiber-optic cable is called the

Step index

A technique that is used to minimize the pulse dispersion effect is to

Minimize the core diameter

Which is not an important characteristic of a light detector?

Power consumption

The dispersion of light in fiber-optic cable caused by a portion of the light energy traveling in the cladding is called

Waveguide dispersion

Recent laser developments for fiber-optic communication include

Distributed feedback (DFB) and vertical cavity surface emitting (VCSEL)

Which of the following considerations is important when deciding between using a diode laser or an LED?

Response time

In 1815, the correct explanation of diffraction was given by

Fresnel

It is the central part of the optical communication system

Optical Fiber

The light energy that is always emitted or absorbed in discrete units

Quanta

Which of the following Ethernet fiber optic standard uses synchronous, Centralized Clock?

10 Base-FB (Backbone)

It is a mixed, multiple-service standard to allow the transmission of voice and video over an FDDJ network.

FDDI – II

It is a layer of plastic that surrounds a fiber or group of fibers

Buffer Tube

The angular separation between the two half-power points on the power density radiation pattern.

Beamwidth

Refers to the direction in space of electric vector of the electromagnetic wave radiated from an antenna and is parallel to the antenna itself.

Polarization

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?

Top loading

What principle that states that the properties of an antenna are independent of whether it is used for transmission or reception.

Principle of reciprocity

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.

3.50

Φ0=

Φ0=3.50

This is often used to cure the problem of great thickness required of lenses used at lower microwave frequencies or for strong curved wavefronts.

Zoning

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.

Antenna

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.

Directive gain

Any array that is directional at right angles to the plane of the array is said, by inference, to have ____.

Broadside action

The ratio of the focal length to the mouth diameter is called __________ of the parabola, just as in camera lenses.

Aperture

Corresponds to a resonant transmission line, and the dipole antennas describe so far have been resonant.

Resonant antenna

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?

0.352

∆=(n1-n2)/n1 =(1.55-1.51)/1.55 =0.0258 NA=n1√(2∆) =1.55√[(2)(0.0258)] = 0.352

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?

20.6

∆=(n1-n2)/n1 =(1.55-1.51)/1.55 =0.0258 NA=n1√(2∆) =1.55√[(2)(0.0258)] = 0.352 Θ0(max)=sin-1NA= sin-10.352=20.6

For a single-mode optical cable with 0.25-dB/km loss, determine the optical power 100km from a 0.1-mW light source.

-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

For an optical fiber 10km long with a pulse-spreading constant of 5ns/km, determine the maximum digital transmission rates for return-to-zero.

20Mbps

Fb= =20Mbps

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

Responsivity

A phenomenon also called stress corrosion resulting if the glass fiber is exposed to long periods of high humidity?

Static fatigue

The theory which states that when visible light or high-frequency electromagnetic radiation illuminates a metallic surface, electrons are emitted.

Planck’s law

The science of measuring only light waves that are visible to the human eye

Photometry

The process of constructing an ILD that is similar to LED except that the ends are highly polished.

Lasing

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.

Pulse spreading

For an electronic device operating at a temperature of 17°C with a bandwidth of 10 kHz, determine the thermal noise power in dBm .

-134dBm N = KTB N(dBm) = 10log (4 x 10-17) = -134 dBm 0.001

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.

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

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?

3

(S/N)p = 100µW = 100 1µW (S/N)o = 1W = 33.3 0.03W NF (ratio) = 100 = 3 33.5

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.

-98dBm

S = Sensitivity = -74dBm + NF + 10log∆f + desired S/N S = -174 + 8 + 10log(200,000) + 15 S = -98 dBm

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?

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

Equivalent temperature of a passive system having the same noise power output of a given system.

noise temperature

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

2.24µV

VN =

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

= 2.24µV

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

30

ᵟ = φ x fi = 0.5 x 5 kHz = 2.5 kHz 75 kHz = 30 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

DPSK

A special digital modulation technique that achieves high data rates in limited-bandwidth channels is called

Quadrature amplitude modulation (QAM)

FSK systems are much superior to two-tone amplitude-modulation systems with respect to

Ionospheric fading characteristics

Using an oscilloscope to display overlayed received data bits that provide information on noise, jitter, and linearity is called a(n)

Eye pattern

The type of radio transmission that uses pseudorandomly switched transmissions is known as

Spread spectrum

The acronym CDMA refers to ________. 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

Radio telemetry

The acronym for the form of data transmission in which the modulating wave shifts the output between two predetermined frequencies is _____.

FSK

Pseudorandom implies a sequence that can be _____ but has the properties of randomness.

re-created

______ implies that both analog and digital signals share the same channel bandwidth.

Hybrid

Telemetry may be defined as _____ metering. Remote

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

Line control

The major difficulty faced by delta modulators is Slope overload

The AT&T T1 lines Use 8-bit PCM code and include 24 voice channels

The ground wire in a USB cable is ______. Brown

A(n) ________ is used to allow a digital signal to be transmitted on an analog channel.

Modem

The bit ________ is the amount of power in a digital bit for a given amount of time.

Energy

The relationship for bit rate to ________ bandwidth is defined by the Shannon-Hartley theorem.

Channel

In an S/H circuit, the time that it must hold the sampled voltage is

Aperture time

Error signals associated with the sampling process are called

Foldover distortion and aliasing

A(n) ________ is a single LSI chip containing both the ADC and DAC circuitry.

Codec

The NRZ digital signal-encoding format has a ________ component in the waveform.

Dc

Reed–Solomon codes utilize a technique called ________ to rearrange the data into a nonlinear ordering scheme to improve the chance of data correction.

Interleaving

The electric field intensity is measured in: V/m

It is a result of an increase in the charge density in dielectric materials.

Polarization

It refers to the maximum antenna gain. Directivity

The maximum horizontal distance between the transmitter and the receiver for line of sight propagation is known as:

radio horizon

Typical mode of radiation of helical antenna is: end fire

The electric field is perpendicular to the earth’s surface, the polarization is:

Vertical

In what major RF band is ground wave basically applied?

MF (Medium Frequency)

A measure of mismatch in a transmission line standing wave ratio

The highest frequency that can be set back to earth by the ionosphere, if wave is sent vertically upward.

critical frequency

Travel in a straight line from the transmitting antenna to the receiving antenna.

space wave

VLF waves are for some types of services because they are very reliable

It is the distance between two wave fronts having the same phase at any given instant.

Wavelength

It is a piece of transmission line which is normally short-circuited at the far end.

Stub

A 50 ohms transmission line is connected to a 30 ohm resistive load. Calculate the reflection coefficient.

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

The characteristic impedance of a transmission line does not depend upon its

Length

Characteristic impedance of a transmission line is the impedance measured at the _______ when its length is infinite.

Input

Which region of the ionosphere is mainly responsible for long-distance night time communications?

F layer

Which is properly terminated antenna? Rhombic

Occurs when the radio beam is at point of grazing over an obstacle.

diffraction

A microwave communications system, space loss calculation formula is

92.4 + 20log F + 20 log D

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.

Dynamic range

Is a PCM system which uses a single bit PCM code to achieve digital transmission of analog signals.

Delta modulation

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.

Longitudinal redundancy check

Is an n-bit data register inside the UART that keeps track of the UART’s transmit and receive buffer registers.

Status Word register

Is an access method used primarily with LANs configured in a bus topology.

CSMA/CD

IP version 4 address length is 32 bits

Is a multiport bridge that provides bridging function. Switch

Is a device which operates in the Network layer and it makes forwarding decisions on the basis of network addresses.

Router

OC-1 (STS-1) line rate is 51.84 Mbps

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 channels

Channel service unit

Modulation which combines encoding and modulation to reduce the probability of error.

TCM

Is an empirical record of a system’s actual bit error performance

BER

Is an error-correcting code used for correcting transmission errors in synchronous data streams.

Hamming code