CHAPTER 1 4.1 Impedance matching ratio of coax balun

Dissipation Factor Indicates energy loss in a capacitor

Quality Factor Indicates energy loss in an inductor

Because of the size of the waveguides

Why is it impossible to use a waveguide at low radio freq?

Losses in the conducting walls of the guide

What causes the attenuation present in waveguides?

Ground Tx lines are either balanced or unbalanced with respect to ___

Spectral Analysis Method of determining the BW of any processing system

50W Average power rating of RG-58 C/u

50 ohms RG-8A/u impedance

RG-211A Coax used for high temperatures

300 ohms 214-056 twin lead characteristic impedance (used in TV lead-in)

AWG#19 Commonly used telephone wire

Quarter wave line Impedance inversion can be obtained in ______

1.2 to 2.8 Dielectric constants of materials commonly used in Tx lines

0.6 to 0.9 Velocity factor of the materials used in Tx lines

Facsimile The transmission of printed material over telephone lines;Emission designation is F3C and A3E

Call waiting tone A continuous tine generated by the combination of 2 frequencies of 350Hz and 440Hz used in telephone lines

10 pulses/sec Pulse dialing rate

VF repeaters Are unidirectional amplifiers having 20-25dB gain placed about 75km apart used to compensate for losses along the telephone line

MTSO Central switching office coordinating element for all cell sites that has cellular processor and cellular switch. It interfaces with telephone company zone offices, control call processing and handle billing activities

Base station Performs radio-related functions for cellular sites in cellular systems

3700Hz Out of band signaling between toll central offices (Bell system standard)

Purely reactive Of SWR = infinite, what type of load the Tx line has?

WATS Standard tariff for flat rate telephone service beyond the normal flat rate in that area

Tariff The published rates, regulations and descriptions governing the provisions of communications services for public use

Varistor A component in the telephone set that has the primary fxn

of compensating for the local loop length

Electromagnetic receiver

Type of receiver used in a conventional telephone handset

0 to 4KHz Ideal passband of a voice-grade circuit using PTN

4KHz Nominal voice channel BW

300 – 3400Hz Telephone channel band pass characteristic

Basic voice-grade The minimum quality circuit available using the PTN

Tie trunk Connects 2 private branch exchanges (PBX)

Trunk line Connects 2 central offices (CO)

3dB Power loss of a telephone hybrid

1897 First Strowger Step-by-Step switch was used in ________

G.122 CCITT recommendation for a preparation of loss plan, a variable loss plan and a fixed loss plan.

1.7x10^-8 ohm-m Copper wire resistivity (ρ)

Umbrella cells Kind of ells appropriate for load management, fast moving mobiles and low usage areas

Adaptive array In cellular networks, standard base station antennas are replaced by _________

Completed The call is _____ when the calling party hears a busy tine on his telephone.

Liable to radiate Short-circuited stubs are preferred to open-circuit stubs because the latter are ______

Quarter wave matching

One method of determining antenna impedance

Quarter wavelength line

It is used as an impedance transformer

The line behaves as a parallel tuned circuit in relation to the generator

If λ/4 Tx line is shorted at one end, ____

Parallel resonant circuit

A shorted λ/4 line at the operating frequency acts like a ____

Series resonant circuit

A shorted λ/2 at the operating frequency acts like a _____

Infinite or an open circuit

The input impedance if a λ/4 short circuited transmission line at its resonant frequency is _____

A high value of resistance

A λ/4 line is connected to an RF generator and is shorted out at the far end. What is the input impedance at the line generator?

Infinite transmission line

Its feature is that its Zin is equal to the line’s surge impedance

Nitrogen Used to keep waveguide dry

Above 3Ghz Waveguides becomes compulsory above _____

50ms Echo suppressors are used on all communication systems

when the round trip time exceeds _____

Insertion of E and H probes into the waveguide

Ways of coupling in and out of a waveguide

Guide wavelength λg (in rectangular waveguides) it is the distance between 2 instantaneous consecutive positions of maximum field intensity;It is always greater then the λo at the same frequency

Waveguides Are Tx lines which can convey electromagnetic waves only in higher order modes;Are hollow structures that has no center conductor but allows waves to propagate down its length;Used mainly for microwave Transmissions because no generators are powerful enough to excite them

At the beginning and at the end of the cable

The outer conductor of the coax cable is usually grounded

Entropy Amount of uncertainty in a system of symbols

Reduced electromagnetic interference

The twists in twisted wire pairs

Inductance Loading means the addition of _____

Coaxial Most commonly used Tx line for high frequencies;Medium least susceptible to noise;Most commonly used Tx line in TV systems

Twisted Pair Medium most widely used in LAN

120 ohms Not a common Tx line impedance

Standing waves A pattern of V and I variations along a Tx line not terminated in its characteristic impedance

antennas At very high frequencies, Tx lines act as ____

DC Blocks It is used in coaxial Tx line to prevent AC power supple voltage from being shorted by a balun or band splitter

Dithering (in TVRO communications) means reducing the effects of noise on the TVRO signal

Freq and Voltage Important quantities in describing waveforms

dNp Known as 1/10 of a Neper

Low attenuation Advantage of a balanced transmission line

Parallel wire line Type of Tx line employed where balanced properties are required

Absorption coefficient

The ration between the energy absorbed by a surface to the total energy received by the surface

The higher the Resistance and The smaller the

The higher the gauge number of a conductor, _______

diameter

λ/4 transformer A short length Tx line used to reduce/eliminate standing waves

Reflectance Ration of reflected power to incident power

CHAPTER 2Sound level meter Instrument used to measure a weighted value of the SPL

(sound pressure level)

Sound An aural sensation by pressure variations in the air which are always produced by some source of vibrations

Noy Unit of noisiness related to the perceived noise level

Phon The unit of loudness level of a sound

Mel Unit of pitch

1000 mels At a sensation level of 40dB, 1000 Hz tone is _____

Sone Unit of perceived loudness

Decibel Measure of the intensity of sound in comparison to another sound intensity

Octaves Much of music is generally referred to in _______

Interval Ratio of frequencies is termed as _______

Pitch and loudness Sound wave’s 2 main characteristics

Pitch A subjective term which is dependent mainly on the frequency and also affected by the intensity

Loudness Or Intensity;Is a subjective effect which is a function of the ear and brain;Loudness depends upon the energy of motion imparted to the vibrating molecules of the medium transmitting the sound;Affected by the distance between the listener and the source and its intensity varies inversely with the square of this distance

Frequency The intensity needed to produce an audible sound varies with ________;The number of vibration or pressure fluctuations per second

Hump and notch Two ways in which the frequency response of a loudspeaker can be varied when it is positioned near a wall

Noise rating values An agreed set of empirical curves relating octave-band SPL to the center freq of the octave bands

Natural freq The freq of a free vibration

Flanking transmission

The transmission of sound from one room to an adjacent room, via common walls, floors and ceilings

Hearing Level A measure of threshold of hearing, expressed in dB relative to a specified standard of normal hearing

330 m/s Velocity of sound in air

341.8 m/s Velocity of sound at room temperature (T=17 deg celcius)

5000 ft/sec Sound wave’s speed in water

Microphone transducer

Converts acoustical energy

Diaphragm and Generating element

2 basic components of a microphone

Expense and fidelity;Complexity and ruggedness;Longevity

Kinds of generating elements

Carbon microphone Operates on the principle that the electrical resistance of carbon granules varies as the pressure on the granules vary

Dynamic microphone Operated by electromagnetic induction that generates an output signal voltage

Crystal microphone Will be damaged if exposed to high temp above 52 deg Celsius

Frequency response Most important specification of loudspeakers and microphones

Bass response IS the bypassing of high audio frequencies

Proximity effect A microphone characteristic that results in boost in bass freq for close microphone spacing

Dolby Noise reduction system used for film sound in movies

Sound intensity Is the sound energy per unit area at right angles to the propagation direction per unit time

Supersonic Speed that is faster than speed of sound

Ultrasonic Sound that vibrates at freq too high for the human ear to hear (over 20KHz)

Wavelength Crest to crest distance along the direction of wave travel

Fundamental Lowest freq produced by a musical instrument

Diffraction Tendency of a sound energy to spread

Refraction When waves bend away from a straight line of travel, it is called _________

Distortion An undesired change in waveform as the signal passes through the device

Exciter Distortion enhances intelligibility when an ______ is added;It is a class of signal processors

Reverberation time Required time for any sound to decay to 60 dB;Time taken for the intensity of the sound energy to drop to one millionth of its initial value

Spider A thin springy sheet of bakelite or metal that permits the voice coil in a dynamic loudspeaker to move back and forth along the core of its magnet

10Hz to 20KHz Bass freq range

20Hz to 20KHz Audio freq range

5KHz to 10KHz High freq range of audio signals

65 dB dB SPL of a voice paging in an office

90 to 85 dB SPL in a church with speech reinforcement only

95 to 100 dB dB SPL in an auditorium with contemporary music

25 to 8000 Hz If the sound waves are converted to electrical waves by a microphone, what is the frequency of the electric current?

Flutter echoes Rapid succession of noticeable echoes

WC Sabine Laid the foundations of acoustic theory of buildings

Threshold of hearing Minimum sound intensity that can be heard

CHAPTER 350 dB The maximum sideband suppression value using filter

system

Noise Is primarily high frequency spikes

H3E Transmits only one sideband;Single side band full carrier emission

A3H Transmits LSB and half of USB;

A3E Double sideband Full carrier emission;Standard way of designating AM

R3E Single side band reduced carrier emission

J3E Single side band suppressed carrier emission;AM system where if m is doubled, the antenna current is also doubled

B8E Independent sideband emission

C3F Vestigial sideband emission;Used in televisions

G3E Phase modulation emission

F3E Frequency modulation emission;Used in FM telephony

F3F Television Emission

F3C and A3E Used in facsimile

F3C Type of emission produced when a frequency modulated transmitter is modulated by a facsimile signal

A3C Type of emission produced when an amplitude modulated transmitter is modulated by a facsimile signal

A3F Type of emission when an amplitude modulated transmitter is modulated by a TV signal

LSB The difference between the RF carrier and the modulating signal frequencies

Baseband freq Produces the sidebands on FM;An information signal that is send directly without modulating any carrier

Spectrum analyzer Test instrument that displays the carrier and the sidebands amplitude with freq to freq

Mixer Also called converter

Buffer Stage in radio transmitter that isolates oscillator from the load

Buffer amplifier Protects the crystal oscillator from ‘pulling’

‘Pulling” Refers to the change of the crystal oscillator frequency by loading

Discriminator Circuit used to detect frequency modulated signals

Carrier signal It has a frequency of 20KHz and above;Has constant peak amplitude

Center frequency The freq of the unmodulated carrier in FM system

Armstrong system One method of generating indirect FM

Reactance modulator One method of direct FM

Direct FM Varactor Diode FM Modulator; Reactance Modulator;Linear IC FM Modulator;PLL with VCO

Direct PM Varactor Diode PM Modulator;Transistor Modulator;

Balanced modulator Circuit

Needed to generate a SSB or DSB signal;Outputs LSB and USB;The output is DSB;It suppresses the carrier;Device that is capable of causing freq translation;Can be used as a phase detector;Lattice modulator – widely used balanced modulator;Product detector – a balanced modulator used to demodulate a SSB signal

Crystal Radio receiver First radio receiver

Non linear Any device to be used as a freq multiplier must be _____

Push-Push amplifier Used for frequency doubling

Frequency synthesizer Frequency division is useful in the implementation of _____

Better fidelity Not an advantage of SSB

Interference to other radio services

Effect of overmodulation in AM transmission

Distortion and splatter Result of the gain level being too high for signals entering the modulator

Base modulation and Collector modulation

Modulation method used for CE configuration

Envelope Detector Most commonly used amplitude demodulator

Rectification Envelope detection is concerned with the process of ___

Distortion Diagonal clipping in envelope detection will result in ____

Coherent signal Has the same Frequency and Phase (but not in amplitude)

Frequency deviation A louder sound, when generating the modulating waveform for FM, will cause a greater ____

Foster Seeley Discriminator

A circuit that demodulates the frequency-modulated signal

Quadrature detector Requires that the inputs are coherent

It is less sensitive to noise spikes;It is less sensitive to interference causing AM

Ratio detector is superior to Slope detector because

3 components A single tone amplitude modulated wave has _____

Continuous modulation

A kind of modulation which the modulated wave is always present

Pulse modulation Type of modulation in which no signal is present between pulses

Coef of modulation Decribes the amount of amplitude change present in an AM waveform

Carrier shift Type of amplitude distortion introduced when the + and – alternations in the AM modulated signal are not equal

The oscillator is crystal controlled

Advantage of PM over FM frequency modulation

AFC A disadvantage of direct FM is the need for

Better S/N ratio;Noise immunity;Capture effectEfficiency of utilized power

Advantage of FM over AM

Wider BW needed;Circuit complexity and cost

Disadvantage of FM over AM

AGC Its function is to maintain the sound volume level of a voice receiver nearly constant for a large single strength range

Noise Blanker Reduces impulse noise in receiver

Frequency translation and up-conversion

If the freq of each component in a signal spectrum in increases by the same fixed amount, this is known as _____

Indirect Synthesizer A frequency synthesizer that contains a single crystal is described as a ________

TRF receiver Receiver in which all RF amplifier stages require manual tuning of the desired RF;Disadvantage is that it has BW variations over the tuning range

Superheterodyne Doesn’t have a modulator;

Receiver An RF amplifier will not be found on every superheterodyne receiver

Image rejection ratio Ratio of the superheterodyne receiver response at the desired fc (carrier freq) to that at the fsi (image freq)

Noise floor of the Rx The limiting condition for sensitivity in a communications receiver

Cross modulation interference

Refers to the condition where the signals from a very strong station are superimposed on other signals being received

Cross modulation An effect which, the modulation of an unwanted signal is transferred to the desired carrier;The modulation of an unwanted signal is heard on the desired signalCan be reduced by installing a filter at the receiver

Intermodulation interference

2 AM transmitting antennas are close together, as a result, the 2 modulated signals are mixed in the final RF stage of both transmitters. What is the resultant effect on the other station?

Connecting a C between the B+ and the lead ground

Motorboating (low freq oscillations) can be stopped by ____

Stray coupling is minimized

Leads should be kept as short as possible in radio circuit so that ____

4 The # of voice transmission that can be packed into a given freq band for amplitude compandored SSB systems over conventional FM-phone systems

Neutralization Prevents the generations of spurious oscillations

Blocking dynamic range

Ability of a communications receiver to perform well in the presence of strong signals outside the band of interest

RF amp;IF amp;AF amp;Mixer

Common to both AM and FM receivers

IF amplifier Determines a communication receiver’s sensitivity

Filter ringing Occurs during CW reception if too narrow a filter BW is used in the IF stage of a receiver

Undesired signals will reach the audio stage

The undesirable effect of using too wide a filter BW in the IF stage of the receiver

3000 Hz In a narrow band FM system, the deviation ratio is commonly 1 and the highest audio freq is generally limited to ____

Desensitizing Refers to the reduction of the Rx Gain caused by the signal of a nearby station Tx in the same freq band

Ensuring good RF Reduces Rx desensitizing

shielding between Transmitter

Presence of a strong signal on a nearby frequency

Cause of Rx desensitizing

BW and NF 2 factors the determines the receiver sensitivity

FM receiver Contains limiter stage, discriminator and de-emphasis circuits;The limiter stage prevents any amplitude modulation of the IF signal;The limiter stage rids FM of noise

2.4 KHZ The degree of selectivity desirable in the IF circuitry of a SSB receiver

Resistor Most amp to break down in a radio circuit

AM detector performs rectification and filtering in the receiver

Approx 2.5 to 1 Ratio of PEP-to-average power during a modulation peak in a SSB phone signal

Higher In most mixers, the oscillator freq is higher than the carrier freq on the input signal

BW of emission and Occupied BW

The BW occupied by the carrier, both sideband and the harmonics

Installing resistive spark plugs

A way of eliminating auto interference to radio reception

BFO Generates an output whose freq differs from the IF by 1KHz;Demodulates SSB or CW signal

Am modulation Same as Linear mixing

Linear Summing Mixing for freq conversion is done with a circuit called _____

FM and double side band AM

Suffers most from selective fading

Capture effect Is the reception blockage of 1 FM phone signal by another FM phone signal

Tuned Circuit A negative half of the AM wave is supplied by a ______ in a diode modulator

By having the carrier vary a resistance

Can produce AM

Variable resistance Amplitude modulators that vary the carrier amplitude with the modulation signal by passing it through an attenuator network is the principle of ________

Diode detector Most widely used amplitude modulator

PIN diode Produced AM at very high frequencies

Switch In a diode ring modulator, the diodes acts like a ___

Differential amplifier The principal circuit in the popular 1496/1596 IC

balanced modulator

Class C The AM signals generated at a low level may only be amplified by what type of amplifier?

Crystals Most commonly used filter in SSB generators

CHAPTER 4PCM Quantizing noise happens in _____

Quantization noise Due to the approximation of the quantized signals

Quantizing noise Noise occurring in the presence of signal resulting from a mismatch between the exact value of an analog signal and the closest available quantizing step in a digital decoder

Thermal Noise /White Noise/ Gaussian Noise/ Johnson Noise

Noise from random acoustic or electric noise that has an equal energy per cycle over a specified total freq band

White noise Is measured on a circuit when it is correctly terminated but does not have any traffic

Thermal Noise An electric noice produced by the thermal agitation of electrons in conductors and semiconductors;Most internal noise comes from this type of noise

Atmospheric noise Noise produced by lightning discharges in thunderstorms;Also known as static noise;Not a great problem above 30MHz;Primary cause is lightning;

Transit time noise Type of noise that becomes a great importance/concern at high frequencies

Impulse noise Noise consisting of irregular pulses of short duration and relatively high amplitude

Man-made noise Is usually from transmission over power lines and by ground waves

Cosmic Noise Noise originating from outside the solar system

Space noise Noise coming from stars and sun

Crosstalk noise Noise that occurs via capacitive or inductive coupling in a cable

Miscellaneous noise Crosstalk due to incomplete suppression of sidebands or to intermodulation of 2 or more freq-multiplexed channels which is unintelligible is classified as ____

Solar flare Large emission of hydrogen from the sun that affects communications

Noise density The total noise power present in a 1Hz BW

Increasing channel BW Not a way of reducing noise

Precipitation static Form of interference caused by rain or dust storms

15 to 160 MHz Industrial noise freq

17 deg Celsius / 290 K Reference noise temp

-90 dBm Reference noise level (relative to 10^-12)

CCIT G. 151 Standard for crosstalk limits

CCITT Rec. G. 172 Standard for intermodulation rates on PCM audio channels

800 Hz Reference freq of CCITT phospohometric noise measurement

Psophometer A device that measures the internal VOC of an equivalent noise generator having an impedance of 600 ohms and delivering a noise power to a 600 ohm load

pWp Unit noise power of psophometer

Nif Noise-improvement-factor

Peak values External noise fields are measured in terms of ____

Level The difference between signal strength at a given point and a reference level

Positive A practical dBrn measurement will almost always be a ____ number

Narrowing the BW Noise can be reduced by ____

uV Noise at the input of the receiver can be as high as ____

Mixer Contributes most of the noise in a receiver

MESFET Transistor with the lowest noise figure in the microwave region;Most commonly used in the microwave freq due to its low noise char

11 years The solar cycle repeats the period of great electrical disturbance approx every ___

CHAPTER 5Field strength Amount of voltage induced in a wave by an

electromagnetic wave

James clerk Maxwell Profounded electromagnetic radiation theory

Transequatorial propagation

Is best during afternoon or early evening

UHF and VHF Most affected by knife edge refraction

Kennely-Heaviside Layers

D,E,F layers

D layer Layer that reflects very low freq waves and absorbs medium freq waves (RL,AM)

E layer Layer used for high-freq day time propagation;Layer that aids MF surface-wave propagation a little and reflects some HF waves in daytime

F2 layer Layer that does not appear at night;Reaches a height of 255 km at night

Band Different grouping of electromagnetic spectrum

Reflection Multipath Fading due to interference between direct and reflected rays

Critical freq The highest freq that can be sent straight upward and be returned back to earth

Scatter angle In troposhepric scatter propagation, the attenuation is dependent on ___

Fading Applies to troposcatter propagation;Defined as the fluctuations in the signal strength at the Rx

UHF Tropospheric scatter is used with freq in the following range

Troposcatter propagation

Means of beyond the LOS propagation of UHF signals;It is where 2 directional antennas are pointed so that their beams intersect at the troposphere

Ducting Super refraction; Occurs in troposphere

Duct Layer of warm air trapped above cool air

Shadow zone Absence of reception

SID Sudden ionic disturbances

Lengthen the skip distance

If the Tx power remains constant, an increase in the freq of the sky wave will

Plane wave Radiowave that is far from its sources is called ____

Wavefront A fixed point in an electromagnetic wave

1W VHF ship station transmitters must have the capability of reducing carrier power to ____

It is more pronounced at wider BW

How does the BW of the transmitted signal affect selective fading

Spread spectrum communication

A wide-BW communications systems in which the RF carrier varies according to some predetermined sequence

Approx 300M m/s Speed of electromagnetic waves travel in freespace

VLF waves Are very reliable and are used for some types of services

Affected by the solar cycle

High freq waves

Freq diversity Best solution to ship to ship fading;2 or more Rx are used using a single antenna;

Space diversity 2 or more antennas are used separated by several wavelengths;Best solution to fading

Window Range of microwave freq more easily passed by the atmosphere than the others

Their freq The absorption of a radio wave by the atmosphere depends on _____

Frequency When a beam of light enters one medium from another, a quality that never changes is its

Attenuation As electromagnetic waves travels in free space, this can happen to them

X-rays Highest freq can be found here

Blue Shortest wavelength

Pitch Quality in sound that corresponds to color in light

Dispersion Is the splitting of white light into its component colors in refraction

8000 lx Minimum illumination recommended for reading

Direct wave Microwave signals propagate by way of the ____

Refracted Ionosphere causes radio signals to be ___

2∏ sr The solid angle subtended by a hemisphere about its center is ____

ELF, VLF, MF Uses surface wave propagation

Sky wave The type of radio wave responsible for long-distance communication by multiple skips is the _______;____ gets in contact with ionosphere and reflected by it

HF (3 Mhz to 30 Mhz) LOS communications is not a factor here;Ionosphere has the greatest effects on this range of freq

MF (300Khz to 3 Mhz)

Ground wave is most effective in _____

CHAPTER 6Discone antenna Has vertical polarization;

Radiation pattern is omnidirectional

Bay A section which would be a complete antenna by itself

UHF and VHF Range of freq where most omnidirectional horizontally polarized antennas are used

Critical phased array It is where the current ratios of 2 or more elements must be held at 5% and the phase angle at 3%

Antenna Device that converts high freq current into electromagnetic wave

Antenna array An antenna with a number of λ/2 antennas on it;An underground antenna near the ground acts as a ______

Dipole antenna Radiation pattern in bidirectional;Antenna that is not grounded at one end

Yagi Uda Antenna that doesn’t use the ground

Elementary doublet Antenna which is 1/10 wavelegth long

Broadside antenna An antenna array which is highly directional at right angles to the plane of the array

Marconi antenna Antenna that radiates an omnidirectional pattern in the horizontal plane with vertical polarization;Length = λ/4;Maximum current is found at the base of the antenna;Not a wideband

Parabolic Dish antenna

An antenna with very high gain and very narrow BW

Notch antenna An open-ended slot antenna

Rhombic antenna Non resonant antenna;A properly terminated antenna;Used primarily for skywave propagation

Horn antenna Antenna that is best excited from a waveguide

Resonant antenna Antenna that is not properly terminated

Helix antenna Must have minimum of 3 number of turns

Vertical loop antenna

Has a bidirectional radiation pattern in the horizontal plane

Vertical λ/4 antenna Antenna that provides maximum radiation to all surrounding points in the horizontal plane

Half wave antenna Voltage nodes are located at the feedpoints;Current nodes are located at the ends

Long-wire antenna Antenna made up of a number of full wavelenths

Good grounding A must for vertical antennas

Azimuth Is the horizontal pointing angle of an antenna

Null Very low signal strength in antennas

BEAMWIDTH Measurement of a unilateral antenna properties of directivity;Is the angle between the half power radiation points

Top loading Used in antennas to increase effective height;Improves radiation efficiency

Collinear All elements in a beam ________ antennas are in line

Lightning Rods Must be mounted on top of a structure not les than 30 cm above the highest point

200 kph Estimated medium wind loading in the Phil for antenna tower design

Parasitic element Improves antenna directivity;Gives the antenna unidirectional properties;Increases the antenna’s power gain (for a Hertz Dipole)

FB ratio Comparing the signal strength arriving at the driven element from the desired direction to the signal strength reaching the driver from the opposite direction

End effect Shortening effect of an antenna that makes it appear as it were 5% longer

Low pass filter Are harmonic suppressors connected to an antenna

Increases antenna’s effective length

Add inductor in series

Decreases antenna’s effective length

Add capacitor in series

Stacking antenna elements

______ in a transmitting system will increase field strength at the Rx and increase the directivity of the Tx antenna;Increases sensitivity to weak signals

Driven element The element fed by the transmission line;λ/2 is its electrical length in an HF beam antenna

BW increases If the antenna is shortened through the use of loading coils

Wave straps in the antenna circuitry

Eliminates strong interference from one particular station by the use of this

Trap antennas Disadvantage is that it will radiate harmonics

300 ohms The input terminal impedance at the center of a folded dipole

Antenna efficiency = (radiation resistance / total resistance ) x 100%

Directivity gain Ratio of max radiation intensity to average radiation intensity

Location of antenna wrt to nearby objects

Factors that determine the radiation resistance of an antenna

Protection of personnel working underneath

Reason for using metal counterpoise when antenna is false

Prevent re-radiation of the LO

Reason for using antenna coupler

Diplexer Antenna coupling unit

Long periodic Useful as a multiband HF receiving antenna

CHAPTER 710 to 1000uW Typical speech power

1000 to 3000 HZ Max intelligibility for voice freq is located between

250 to 500 Hz Max voice energy is located between

Volt unit meter Device used to measure speech volume

300 to 3400 Hz Standard freq BW for voice transmission

4000 Hz Standard voice channel spacing

1300 ohms Resistance limit for #2 crossbar exchange in US

0.51 dB/1000ft AWG#26

Loss: 3dB/15ft RG-58 cable

-42 to -52 volts Telephone set voltage sent by CO

3W Typical power output of a cellular phone

825 to 845 MHz Cellular phones transmit in the band from ______

870 to 890 MHz Cellular phones receives in the band from ______

890 – 915 MHz The mobile-to-base frequency assignment for GSM System

45 MHz Frequency separation between the transmit/receive channels

30 KHz Frequency separation between the recieve/receive channels

825.015/870.015 MHz

Channel 1 Transmit/Receive frequency

666 # of transmit/receive channels in the cellular system

80 km The transmission range of cellular telephony

13 miles Range of cellular CDMA System

50 dB Sensitivity of a cellular receiver

± 12KHz Freq deviation of cellular telephone system

Large service area Not an advantage of cellular telephony

Full duplex A cellular phone operates in FD

Half duplex Radio communications between points using a single share freq

Radiotelephony Type of communication when the human voice and music are transmitted

Singing Caused by excessive + feedback;Echo that is completely out of control

Roaming The signal quality of the calls is constantly monitored by the base station, when the quality if the calls drops below a certain specified level, the base requests the MTSO to try and find a better cell site

25 second Time it takes a facsimile to transmit a standard page

Electrolytic recording

A kind of recording used by facsimile

Skewing Distortion in facsimile

Crosstalk Causes a herringbone pattern in facsimile

Acoustic coupler Converts electric signals to audio signals

Hybrid circuit Converts 2wire to 4wire

2wire circuit A circuit usually in the subscriber loop, between the telephone set and the CO

4wire circuit Is used between serving CO for long distance connections with one paro being used for each direction of transmission

Local loop A 2wire or 4wire communication circuit between the customer’s premise and the CO

Subscriber’s loop Physical connection between the tel set and the switching equipment

Trunk line Connects 2 COs

MTSO Linking point between a cell phone and a regular telephone;All of the base stations are linked together by _____ which serves as the CO and management node for the group;Master control center for cellular telephone system;Controls the power of a cellular radio

Cell site Provides interface between the mobile tel switching office and the mobile units

Janyes maximum entropy principle

____ of a data reduction says that when reducing a set of data into the form of an underlying mode, one should be maximally non-committal wrt the missing data

Discrete channel Combination of modulator, channel and detector

1.88 – 1.90 GHz Freq of DECT

12 # of simultaneous calls DECT system can support

120 # of simultaneous calls DECT radio transceiver can assess at a given time

1983 Cellular mobile system was first operated in ______

1000 TACS is a cellular system with ____ channels

6000 Hz SAT (Supervisory Audio Tone) freq is _____

100,000 System capacity of AMPS

Digital-AMPS (D-AMPS)

The voted cellular digital standard

416 # of channels for Band A and for Band B in D-AMPS

Numeric Assignment Module

NAM

Private Automatic Branch Exchange

PABX

Pilot carrier signals Signals designed to keep the receivers and transmitters aligned

Loop extender A device that increases the battery voltage on a loop and extends its signaling range

12 Under ordinary circumstances, the CCIITT recommends that the # of circuits in tandem must not exceed _____

First selector Responds to the request if a subscriber by sending a dial tone

Section The other name of class2 office in the NA switching plan

Small area A cell in the cellular tel system means ____

Cell splitting Single cell subdivided into smaller cells

Circle First cell shape

Repeater Each cell contains a ____

60 degrees Beamwidth of the reflector of the Rx antenna in the base station

Hailing channel Or Calling channel

Erlang Is equal to the # of simultaneous calls originated during a specific hourly period

Erlang B The traffic model about blocked calls clear condition specified blocking probability

Erlang C The traffic model about blocked calls delay condition specified delay probability

Poisson The traffic model about blocked calls held condition specified the held probability at the a time period equal to an average holding time

Volume A method of expressing the amplitudes of complex non-periodic signals such as speech

Echo suppressors ___ is a voice operated device that inserts a high loss in the opposite direction of transmission of the talking party

Double spotting ___ is the picking up of the same station at 2 nearby points on the receiver dial

TPS The type of connector arrangement wherein a customer may move to another location and still retain the same tel number

CCD Most commonly used light sensor in modern fax machines

1500 and 2300 HZ In FM Fax, the frequencies for B&W are ____ respectively

Vestigial sideband AM

Modulation used by Group2 Fax

QAM Modulation used by Group3 Fax

56 Kbps Transmission speed of Group4 Fax

Group3 Fax Most widely used fax standard

Thermal Most fax printers are of which type?

CCITT The one who set up facsimile standards

Satellite weather photos

Type of graphics commonly transmitted by radio fax

Modified GSM The system used by PCN (Pesonal Communications Network)

Termination Refers to - load connected to the output end of a transmission line

CHAPTER 8Optical Fiber Not suitable for CSMA Operation

Transducer Used to convert time varying electrical quantity to an appropriate form

2520 KHz U600 BW

2728 KHz L600 BW

600 AT&T Master Group

300 CCITT Master Group

Hybrid Data Refers to the combined digitally encoded signals transmitted with FDM signals as one composite baseband signal

L carrier system Transmit frequency-division-multiplexed VB signals over a coax up to 4000miles

56KHZ Guard Band between supergroup 18 and supergroup D25

1800 VB Channels A radio channel is composed of ___

Zero bit insertion The transparency mechanism used with SDLC is called ____

2B + D Equation that defines the composition of an ISDN basic access line

64 Kbps Data rate of ISDN basic B Channel

16 Kbps Data rate of ISDN basic D Channel

3 # of channels on which different operations can occur simultaneously on one ISDN basic access line

SDH (Synchronous Digital Hierarchy)

A digital network where voice, video, text and data are multiplexed into a single network for processing and are transmitted prior to use

Terminal Adapters Non-ISDN equivalent can be connected to ISDN line by the

use of ____

213 to 552 KHz;BW = 240 KHz

Baseband freq of standard FDM basic supergroup

Bipolar What is the Transmission signal coding for T1 carrier?

Interfaces the Digital Terminal Equipment to analog communications channel

Purpose of the data modem

DTE (Data Terminal Equipment)

The LCU (Line control Unit) operates on the data in digital form and is therefore called ____;A system that performs // to serial and serial to // conversion of data link;

10Mbps Ethernet is baseband system using CSMA/CD operating at ____

CSMA/CD Before attempting to transmit data, each station has to listen to the channel;With ____, a station monitors the line to determine if the line is busy

Manchester A type of digital encoding technique used to detect collision in CSMA/CD

Channel Accessing Mechanism used by the station to gain access to LAN

Common Channel Signaling

Signaling method relating to a multiplicity of circuits is conveyed over a single channel by labeled messages

LAN Is data communications network designed to provide 2-way communications between a large variety of data communications terminal equipment within a relatively small geographic area

Bridge Interconnects LAN having identical protocols at the physical and data link layers

Router Interconnects LAN having identical protocols at the physical and network layers

Gateway Interconnects LAN that has totally different protocols and format

Parallel Data All bits in a character can be sent/received simultaneously.

Serial Data The bits in a character which are send/received one at a time

Parallel transmission Also called parallel by bit;Also called serial-by-character;

1500m Use of coax cables in interconnecting networks is limited to an overall length of ____

Packet Switching Hold and forward network

Message Switching Store and forward network

Baseband Tx Uses TDM;Transmission where the data are inputted directly on the

cable (data on cable);Medium is a single channel;

Broadband Tx Uses FDM;Transmission where the data are inputted inside the carrier wave (data on carrier);Medium is a multiple channel

Noise is amplified with voice when an FDM system is used

Reason why FDM is being replaced by TDM

Quadrature multiplexing

The process that uses the orthogonality of sines and cosines that makes possible to transmit and receive to different signals simultaneously on the same carrier freq

Start/stop mode Is the mode of transmission in public data network in which data are transferred from source to the network then to the destination in an asynchronous data format

On/Off Keying Amplitude shift keying is also known as _____

Source Coding Circuit the performs the inverse mapping and delivers to the user destination, a reproduction of the original digital source output

2B1Q Encoding The type of encoding used in the Tx of data on an ISDN line between a customer’s premises and a carrier’s central office

Huffman Code A source code whose average word length approaches the fundamental set by the entropy of a discrete memory source

Morse code Code that used three unequal length symbols, dot, dash and space to encode a character

Emile Baudot Developed the fixed-length binary code for telegraphy

Alex Reeves Inventor of the PCM for digital encoding of speech signals

1950 Year where computers and terminals start communication with each other over long distances

1983 Year ISO (International Standardization Organization) adopted the 7layer OSI (Open System Inteconnection) model

ISO 7809 A standard that combines previous standards 6159 and 6256 and outlines the class of operation necessary to establish the link level protocol

PRNET Store and forward Multiple Access Network

TMS Digital switching concepts that can handle more channels

DCA Who promulgated communications-related military standards (MIL-STD)

ARQ Error control used in high freq radio data transmission

EIA Electronic industry association

PDN (Public Data Network)

A communications network designed for transferring data from one point to another

20 Kbps RS-232 is normally an interface between DTE and DCE, what is its signal rate?

Smart mOdems Accepts commands from the terminal via RS-232 interface

FSK Used by slow speed modems

25 Rs-232 has ____ number of PINS

Flexible size Most significant advantage of modular switch over time-and-space switch

Aliasing The overlapping of the original spectrum and the first translated component

Folding freq The highest theoretical freq that can be processed at a sampling rate without aliasing

64 Kbps Basic speed of a digital system

Large BW is required;Requires ADC, DAC;Incompatible with existing analog facilities

Disadvantage of PCM systems and digital transmission systems in general

PCM System A digital transmission system

Quantizing noise Present in PCM systems;The difference between the original and reconstructed signal

Sampling;Quantizing;Coding

Steps to follow to produce a PCM signal

1200 Kbps CCITT V.26 Modems has a modulation rate of ____

Data in video Not a hybrid data

Much better noise immunity

Advantage of PTM over PAM

Dynamic range The ratio of the largest possible magnitude to the smallest possible magnitude that can be decoded by the DAC

Polling A transmission system for a multidrop system;When one station is designates as a master and the rest of the stations are considered as slaves, message handling is _____;Is an invitation by the primary to the secondary equipment to transmit a message;

Echoplex Mode of transmission that achieves less than Full duplex but more than half duplex

Line protocol Rules governing the transmission of digital information

Agreed upon in advance between

Codes must be ___

sender and receiver

ASCII Has 132 chars including 32 control chars;Has 7 bits;Means terminals using asynchronous transmission in ASCII;Most widely used data communications code

EBCDIC Character code that is used without parity;8 bit character code

32H SYN Character of EBCDIC code

Baudot code Fixed length 5 char code;Requires shift characters to provide sufficient combinations;

Framing Is concerned with the boundaries between characters

The end of packet framing

A packet format has an error detecting code at the ____

Asynchronous Transmission

Is less efficient but simpler

Modem Hardware used when the host computer and the terminal are in separate locations;Referred to as a DCE (digital communications equipment);Equipment that interfaces the DTE to the analog Tx line

Null modem A device that connects 2 DTEs directly by emulating the physical connections of a DCE

Low speed modems 2400 bps

Medium speed modems

2400 – 4800 bps

High speed modems 9600 bps

Front end processor Is the data communications hardware that assists the host computer in handling input and output tasks

Equalizer D to A synchronous modems send signals to the ____;The D to A converter in a synchronous modem sends signal to the ____;

Adaptive equalizers Provides post equalizations to the received analog signal;The receive equalizer in a synchronous modem is called ____;The D to A converted in a synchronous modem is called ___;

Amplitude delay Compromise in equalizer settings typically affect ____

Line equalizing A means of improving the quality of a private line ckt by adding amplifiers and equalizers to it

D to A converter Input for a PCM decoder circuit is a series of bits;Output for a PCM decoder circuit is a parallel output of binary coded signals

Gray code Binary codes are transformed in modems into ____

Protocol Analyzer Best type of data communications test equipment

Intelligent terminal Which computer terminal can be programmed to perform

new functions

Unknown The # of bits that are zeros on each symbol when one is transmitting odd-parity coded symbols

FSK A digital modulation technique that results in 2 different frequencies representing binary 1 and 0;Used by Bell 103/113 series for full duplex, 2 transmission speeds of 1 to 300 bps

H-factor Defined as the figure of merit to express degree of modulation in an FSK modulator

Novell Netware ___ is a network operation system with several buildings in compound

Delta modulation Alternative way of digitizing analog signals

3.32 dits 1 bit = ____

Bit rate Rate of change at the input of the modulator

Serial printer Prints 1 char at a time

Impact printer Strikes a ribbon against the paper to produce character images

Bisync Character oriented protocol

STX Start of bisync

X.75 Protocol for packet switching network

Isosynchronous transmission

When asynchronous data are used with synchronous modems

Asynchronous data With _____, each character is framed between a start and stop bit;0 – start bit;1 – stop bit;It is a character oriented protocol

Synchronous data With ___, rather than frame each character independently with a start and stop bit, a unique synchronizing char called SYN is transmitted at the beginning of each message

Overhead Characters that must be transmitted other than the data are called ____

Flag field Used to achieve character synchronization in SDLC

Flag Denotes the start and end of a data link frame

01111111 Go ahead sequence

CRC-16 In USA, it is the most common CRC cocde

Activate RLSD Training sequence (a bit pattern used to synchronize the receive modem) accomplishes one of the ff fxns

low band channel Channel in the 103 modem that occupies a passband from 300 to 1650 Hz

DISC A command that places a secondary station in the normal disconnect mode

Start/stop mode A mode of Tx in public data network in which data are transferred from source to the network to the destination in

an asynchronous data format

IEEE 802.3 CSMA/CD

IEEE 802.4 CSMA/CA

IEEE 802.5 Token passing for Bus Topology

3 How many OSI layers are converted under the X.25 standard

Handshaking Technique involving signaling by both ends of a link to ensure correct data transfer

Scrambler Found in the Tx section in a synchronous modem

XON/XOFF Is a method of flow control

CTS An example of outband signaling is _____

I series CCITT standards that refer to various aspects of ISDN

I.120 I-series that describes what an ISDN is

V series CCITT standard concentrating on data communications over the telephone network

V.14 A recommendation which allows a synchronous modem to be used to transmit asynchronous characters without error control

V.24 A CCITT recommendation which gives definition for the interchange circuits of DTE and DCE

V.26bis Defines a 2400-bps, PSK, half duplex, modem operating at 1200 bauds

V.100 Describes the interconnection between PDNs and PSTNs

X.200 Standard for the 7layer model of OSI

RS-232, RS-350, RS-449, V.21, V.24

Examples of standards for interfaces between terminals and modems

1800 Hz Western Electric 2911 modem operates with a carrier frequency of

Bipolar Violation Occurs when 2 successive pulses have the same polarity and are separated by a zero level

Flow control Process of starting and stopping the terminal output to avoid loss of characters by the receiving stage

Buffering Temporarily storing data to allow for small variations in device speeds

XMODEM Popular PC protocol

ZMODEM Protocol that adjusts its block size based on the lone error rate

DEREP-RB Not a common DNA Repeater

Computer data Data communications refers to the transmission of ____

Bus Fastest LAN topology

Application-independent interfaces

Characteristic of LAN

Cable TV system Not a LAN

Fiber optic Tx Cannot be provided in a broadband LAN

PBX A small telephone switching system that can be used as a LAN

Digital PBX A LAN architecture that can be expanded to the greatest total system BW

Telephone Not primarily a type of data communications

1,0 Mark frequency, space frequency

Noise Cause of errors in data transmission

VRC Other name for parity

LRC Produces BCC (block check char)

QAM Combination of ASK and QPSK

XNOR Not a part of QAM modulator

Redundancy Not commonly used method of error detection

Balanced demodulators

A basic modulator/demodulator circuit in PSK

30 stations per segment

Limitations of 10Base2 network

Logical Not an important char of the physical layer

CHAPTER 9RADAR Radio detection and ranging

ADF Automatic direction finder

DME Aircraft navigation system that determines the time-to-station (TTS) or time-to-go (TTG)

EADI Electronic altitude and director indicator

SONAR A shipboard equipment which measures the distance between the ship’s bottoma dn the ocean floor

Terrestrial Flight Telephone system

An inflight system that allows passengers to make tel calls, send faxes, and play computer games etc

1300 HZ RF carrier of the middle marker is ____

43,500 MHz Freq a radio altimeter operates on

K x 4000 miles Re used in communications design

The pulse width IF Bandwidth is inversely proportional to ____

Space diversity Method applied to reflective path to reduce fading;____ transmission means transmitting and receiving on 2 or more antennas operation on the same frequencies

Freq diversity Method applied to overcome multipath fading of microwave system over water;Method where the signal in transmitted on 2 different freq over the same path;

Litz wire Wire used to reduce skin effect

TWT (traveling wave tube)

Consists of electron gun, helix and collector;Advantage over Klystron for microwave amplification is wider BW;Used at freq in the order of 8000 MHz

Helix The electron beam in a TWT is density modulated by the _____

Wide BW Major advantage of a helix traveling wave tube

Prevents oscillations Attenuator’s purpose in TWT

Klystrons Replaces TWTs in high power amplifiers

At the cathode end of the helix

At what position is the input signal inserted into a TWT

Maintain the desired klystron frequency

In radar set receivers, an AC AFC system may be used to ______

Magnetron Most widely used radar transmitter component;Most common application is in radar;Is only used as a oscillator;A high power microwave pulse of the order of MW can be generated by a _____

Reflex klystron Used as a oscillator;Low power Gunn diodes are replacing _____

Catcher cavity In a klystron amplifier, velocity modulation of the electron beam is produced by the ____

Cavity resonators Sets up the operating frequency of klystrons and magnetrons;A half wavelength, close section of a waveguide that acts as a // resonant circuit is knows as a ____;Is equivalent to an LC resonant circuit

CRT Not a microwave tube (TWT, Klystron and Magnetron)

Tunnel Diode Does not ordinarily operate with reverse bias

Gunn diode Low power radar transmitters and receivers use which component?;A popular microwave oscillator

Varactor and step recovery diode

Widely used in frequency multipliers

Hot carrier diode A popular microwave mixer diode

Attenuation due to water vapor and oxygen

Considered as atmospheric attenuation

60 GHz Freq where oxygen causes excessive attenuation

183 GHz Freq where water causes excessive attenuation

10 GHz Rainfall becomes an important factor in fading of radio waves at frequencies above ___

Slow fading Attenuation that occurs over many different wavelengths of the carrier;Not due to multipath;

Large reflector Causes multipath or frequency selective fading

Delayed Spreading Causes intersymbol interference (in microwave Tx that uses digital radio)

6th Theoretically, electromagnetic radiation field strength

varies in inverse proportion to the square of the distance but when the atmospheric attenuation effects and the absorption of the terrain are taken into account, the attenuation can be as high as the inverse ____ power of the distance

54 The CCIR hypothetical reference circuit covering a distance of 2500 km consists of how many hops

Waveguides Are transmission lines which convey electromagnetic waves in highest freq;They act as a highpass

The cut-off freq if a waveguide

The lowest frequency the waveguide operates

Probe Introduces magnetic field into the waveguide

Periscope antenna Advantage is that it shortens the waveguide’s length

Flattening of equivalent’s curvature (EC)

As the value of k increases, ____ happens

Towards the earth If k-factor is greater then 1, the array beam is bent ____

Phased array A radar antenna using multiple dipoles or slot antennas in a matrix with variable phase shifters is called an ____

PPI Most common radar display;Has an aquadag coating on the inside of the tube (to act as a second anode)

Both lower antenna rotation speed and higher pulse repetition

The display on the PPI scope of a radar set will have greater intensity under the following conditions:

Horn and parabolic reflector

Most radar antennas use ____

Horn antenna Most widely used microwave antenna

Antenna directivity The ability of a radar to determine the bearing of a target

Spark gap Component in a duplexer that protects the receiver from the higher transmitter output

Doppler effect Measures speed;The freq changes;

0.6 The optimum clearance from an obstacle in a microwave system is accepted as ____ of the first fresnel zone radius

Infinity The microwave beam curves the same than that of the earth when the value of the correction factor k equals ____

Baseband repeaters An active microwave radio repeater that can provide drops and inserts

Decrease in resonant frequency

Decreasing the volume of a cavity causes a __________

PCBs Stripline and microstrip transmission lines are usually made

with ____

High loss Coax cable is not used for long microwave Tx because of its ____

Mobile radio Not a common microwave application

1GHz to 100GHz Range of microwave frequencies

Higher cost equipment

Not a disadvantage of microwave

Greater Tx distances A main advantage of microwave

LF band LORAN-C operating freq lies on the ____