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Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 What is the major advantage of the A. Medium (Ans.) A. Air telegraph over earlier methods of B. Source...

Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 What is the major advantage of the A. Medium (Ans.) A. Air telegraph over earlier methods of B. Source B. Sound (Ans.) communication? C. Detector C. Radio D. Receiver D. Light A. Range B. Speed (Ans.) Which of the following is NOT an What are the three audible frequency C. Security element necessary to propagate sound? ranges? D. Reliability A. Medium A. Subsonic, sonic, and supersonic The spreading out of radio waves is B. Source B. Infrasonic, sonic, and ultrasonic referred to as propagation and is used in C. Detector (Ans.) which of the following Navy equipment? D. Reference (Ans.) C. Infrasonic, subsonic, and ultrasonic D. Infrasonic, subsonic, and supersonic A. Detection If a wave has a velocity of 4,800 feet per B. Communication (Ans.) second and a wave-length of 5 feet, what If a bell is placed in a jar and the air in the C. Radar and navigation is the frequency of the wave? jar is replaced with a gas of a higher D. Each of the above density, what is the effect, if any, on the A. 9.6 Hz speed of the sound when the bell is rung? Radio-frequency waves CANNOT be B. 96 Hz seen for which of the following reasons? C. 960 Hz (Ans.) A. The sound stops D. 9,600 Hz B. The sound travels faster A. Because radio-frequency energy is C. The sound travels slower (Ans.) low powered Which of the following statements about a D. The sound is not affected B. Because radio-frequency waves are wave is the law of reflection? below the sensitivity range of the Varying which of the following wave human eye (Ans.) A. The angle of incidence is equal to the characteristics will cause the length of C. Because the human eye detects only refracted wave sound waves to vary? magnetic energy B. The angle of incidence is not equal to D. Because radio-frequency waves are the refracted wave A. Phase above the sensitivity range of the C. The angle of incidence is equal to the B. Quality human eye angle of reflection(Ans.) C. Amplitude D. The angle of incidence is not equal to D. Frequency (Ans.) Radio waves travel at what speed? the angle of reflection What are the three basic characteristics of A. Speed of sound If a wave passes first through a dense sound? B. Speed of light (Ans.) medium and then through a less dense C. Speed of the Earth's rotation medium, which of the following angle- A. Amplitude, intensity, and quality D. Speed of the Earth's orbit around the of-refraction conditions exists? B. Amplitude, pitch, and tone Sun C. Pitch, intensity, and quality (Ans.) A. The angle of refraction is greater than D. Pitch, frequency, and quality Which of the following types of energy the angle of incidence (Ans.) CANNOT be seen, heard, or felt? B. The angle of refraction is less than If several musical instruments are playing the angle of incidence the same note, you should be able to A. Radio waves (Ans.) C. The angle of refraction is equal to the distinguish one instrument from another B. Sound waves angle of incidence because of which of the following C. Heat waves D. The wave will pass through in a characteristics of sound? D. Light waves straight line A. Quality (Ans.) A stone dropped into water creates a The reception of an AM-band radio B. Overtones series of expanding circles on the surface signal over mountains can be explained C. Frequency of the water. This is an example of which by which of the following principles of D. Intensity of the following types of wave motion? wave propagation? Through which of the following mediums A. Transverse (Ans.) A. Reflection will sound travel fastest, at the indicated B. Concentric B. Refraction temperature? C. Longitudinal C. Diffraction (Ans.) D. Compression D. Doppler effect A. Air at 68º F B. Lead at 20º C A sound wave that moves back and forth What wave propagation principle C. Steel at 32º F in the direction of propagation is an accounts for the apparent increase in D. Steel at 20º C (Ans.) example of which of the following types frequency as a train whistle approaches of wave motion? and the apparent decrease in frequency as In sound terminology, which of the it moves away? following terms is the same as a wave A. Composite reflection? B. Concentric A. Refraction C. Transverse B. Reflection A. Echo (Ans.) D. Longitudinal (Ans.) C. Diffraction B. Image D. Doppler’s effect (Ans.) C. Acoustics Which of the following terms is used for D. Refraction the vehicle through which a wave travels Longitudinal wave disturbances that from point to point? travel through a medium are known as Multiple reflections of sound waves are what type of waves? referred to as 1 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 A. noise B. Magenta, yellow, and cyan (Ans.) C. density B. acoustics C. Purple, yellow, and black D. complexity C. interference D. Red, white, and blue D. reverberation (Ans.) In a comparison of waves of light and What causes sunlight to separate into sound as they travel from an air into Two out-of-phase waves of the same different wavelengths and display a water, how is the speed of (a) light waves frequency that are moving through the rainbow of colors when passed through a and (b) sound waves affected? same medium are said to present which of prism? the following types of interference? A. (a) Increased (b) increased A. Refraction B. (a) Increased (b) decreased A. Additive B. Reflection C. (a) Decreased (b) decreased B. Constructive C. Dispersion (Ans.) D. (a) Decreased (b) increased (Ans.) C. Both A and B above D. Diffraction D. Subtractive (Ans.) Which of the following waves are NOT a The sun, gas flames, and electric light form of electromagnetic energy? A cavity that vibrates at its own natural filaments are visible because they are frequency and produces a sound that is A. Heat waves louder than at other frequencies is A. opaque B. Sound waves (Ans.) demonstrating which of the following B. transparent C. Light waves sound characteristics? C. nonluminous D. Radio waves D. self-luminous (Ans.) A. Noise The electromagnetic spectrum represents B. Quality Substances that transmit almost all of the the entire range of electromagnetic waves C. Resonance (Ans.) light waves falling upon them possess arranged in the order of their D. Reverberation which of the following properties? A. color Energy in the form of light can be A. Opaqueness B. frequency (Ans.) produced through which of the following B. Transparence (Ans.) C. visibility means? C. Translucence D. application D. Self-lumination A. Chemical Which of the following portions of the B. Electrical Some substances are able to transmit light frequency spectrum contains the highest C. Mechanical waves but objects cannot be seen through frequency? D. Each of the above (Ans.) them. Which of the following properties does this statement describe? A. X-ray (Ans.) The scientist, J. C. Maxwell, developed B. Radar the theory that small packets of A. Opaqueness C. Light electromagnetic energy called photons B. Transparence D. Cosmic produce C. Translucence (Ans.) D. Self-lumination Which of the following electronic devices A. sound is used to radiate and/or collect B. noise The speed of light depends on the medium electromagnetic waves? C. echoes through which light travels. For which of D. light (Ans.) the following reasons does light travel A. Antenna (Ans.) through empty space faster than through B. Receiver A large volume of light radiating in a an object such as glass? C. Transmitter given direction is referred to as a D. Transmission line A. Space is less dense than glass (Ans.) A. ray B. Space is more dense than glass The electric field and magnetic field B. beam (Ans.) C. Glass reflects the light back to the combine to form which of the following C. shaft source types of waves? D. pencil D. Glass refracts the light, causing the light to travel in all directions A. Spherical Which of the following units of B. Elliptical measurement is/are used to measure very If a light wave strikes a sheet of glass at a C. Electromagnetic (Ans.) short wavelengths of light? perpendicular angle, what is the effect, if D. Each of the above any, on the light wave? A. Angstrom (Ans.) The magnetic field radiated from an B. Millimicron A. The wave is completely absorbed antenna is produced by what electrical C. Both A and B above B. The wave is reflected back toward the property? D. Millimeter source (Ans.) C. The wave is refracted as it passes A. Voltage What are the primary colors of light? through the glass B. Current (Ans.) D. The wave is unchanged and continues C. Reactance A. Red, blue, and yellow in a straight line D. Resistance B. Red, blue, and green (Ans.) C. Red, violet, and indigo The amount of absorption of the light that The electric field radiated from an D. Blue, green, and violet strikes an object is determined by the antenna is produced by what electrical object’s property? What are the secondary colors of light? A. Color (Ans.) A. Voltage (Ans.) A. Orange, yellow, and blue-green B. purity B. Current 2 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 C. Reactance following frequencies is NOT a A. (a) Electric (b) earth (Ans.) D. Resistance harmonic? B. (a) Electric (b) antenna C. (a) Magnetic (b) antenna Applying RF energy to the elements of an A. 6,000 kHz D. (a) Magnetic (b) earth antenna results in what phase relationship B. 5,000 kHz (Ans.) between voltage and current? C. 3,000 kHz Energy radiated from an antenna is D. 4,000 kHz (Ans.) considered horizontally polarized under A. Voltage lags current by 90 degrees which of the following conditions? (Ans.) A radio wave with a frequency of 32 kHz B. Voltage leads current by 90 degrees is part of which of the following A. If the wavefront is in the horizontal C. Voltage and current are 180 degrees frequency bands? plane out of phase B. If the magnetic field is in the D. Voltage and current are in phase A. The IF band (Ans.) horizontal plane B. The MF band C. If the electric field is in the horizontal What field exists close to the conductor C. The HF band plane (Ans.) of an antenna and carries the current? D. The VHF band D. If the induction field is in the horizontal plane A. Electric A frequency of 3.5 GHz falls into what B. Magnetic RF band? The ability of a reflecting surface to C. Induction (Ans.) reflect a specific radio wave depends on D. Radiation A. High which of the following factors? B. Very high What field travels through space after C. Super high (Ans.) A. Striking angle being detached from the current-carrying D. Extremely high B. Wavelength of the wave rod of an antenna? C. Size of the reflecting area A radio wavelength expressed as 250 D. All of the above (Ans.) A. Electric meters may also be expressed as how B. Magnetic many feet? If the two reflected radio waves shown in C. Induction the figure are received at the same instant D. Radiation (Ans.) A. 410 at the receiving site, what will be the B. 820 (Ans.) effect, if any, on signal quality? Electric and magnetic fields on an antenna C. 1,230 reach their maximum intensity at which of D. 1,640 A. A stronger signal will be produced the following times? B. A weak or fading signal will be An increase in the frequency of a radio produced (Ans.) A. When they are a full cycle apart wave will have what effect, if any, on the C. The signal will be completely B. When they are three-quarter cycle velocity of the radio wave? canceled out apart D. None of the above C. When they are a half-cycle apart A. Increase (Ans.) D. When they are a quarter-cycle apart B. Decrease The bending of a radio wave because of a (Ans.) C. None change in its velocity through a medium is D. Either increase or decrease known as The induction field is made up of which of the following fields? An increase in frequency of a radio wave A. refraction (Ans.) will have what effect, if any, on the B. reflection A. E field only wavelength of the radio wave? C. deflection B. H field only D. diffraction C. Both E and H fields (Ans.) A. Increase D. None of the above B. Decrease (Ans.) Radio communications can be diffracted C. Either to exceptionally long distances through After the radiation field leaves an antenna, D. None of the above the use of (a) what frequency band at (b) what is the relationship between the E and what relative power level? H fields with respect to (a) phase and (b) What is the frequency, in kHz, of a radio physical displacement in space? wave that is 40 meters long? A. (a) Very low frequency (b) Low power A. (a) In phase (b) 90 degrees (Ans.) A. 75 B. (a) Very high frequency (b) Low B. (a) Out of phase (b) 90 degrees B. 750 power C. (a) In phase (b) 180 degrees C. 7,500 (Ans.) C. (a) Very low frequency (b) High D. (a) Out of phase (b) 180 degrees D. 75,000 power (Ans.) D. (a) Very high frequency (b) High What is the first harmonic of a radio wave What is the approximate wavelength, in power that has a fundamental frequency of 2,000 feet, of a radio wave with a frequency of kHz? 5,000 kHz? Electrically charged particles that affect the propagation of radio waves are found A. 6,000 kHz A. 197 feet in what atmospheric layer? B. 2,000 kHz (Ans.) B. 1,970 feet C. 3,000 kHz C. 19,700 feet A. Troposphere (Ans.) D. 4,000 kHz D. 197,000 feet (Ans.) B. Ionosphere C. Chronosphere In a radio wave with a fundamental The polarity of a radio wave is determined D. Stratosphere frequency of 1.5 kHz, which of the by the orientation of (a) what moving field with respect to (b) what reference? 3 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 Most weather phenomena take place in A. Alpha radiation The distance between the transmitter and which of the following region of the B. Cosmic radiation the nearest point at which refracted waves atmosphere? C. Infrared radiation return to earth is referred to as the A. Troposphere (Ans.) D. Ultraviolet radiation (Ans.) A. skip distance (Ans.) B. Ionosphere B. return distance C. Chronosphere Ultraviolet waves of higher frequencies C. reception distance D. Stratosphere produce ionized layers at what relative D. ground-wave distance altitude(s)? Radio wave propagation has the least When ground-wave coverage is LESS effect because of its constancy on which A. Lower than the distance between the transmitter of the following atmospheric layers? B. Higher and the nearest point at which the C. Both A and B above (Ans.) refracted waves return to earth, which of A. Troposphere D. None of the above the following reception possibilities B. Ionosphere should you expect? C. Chronosphere The density of ionized layers is normally D. Stratosphere (Ans.) greatest during which of the following A. No sky-wave periods? B. Weak ground wave Long range, surface-wave C. A zone of silence (Ans.) communications are best achieved when A. At night D. Strong ground wave the signal is transmitted over seawater B. Before sunrise with (a) what polarization at (b) what C. Between early morning and late The greatest amount of absorption takes relative frequency? afternoon place in the ionosphere under which of the D. Between afternoon and sunset (Ans.) following conditions? A. (a) Vertical (b) Low B. (a) Vertical (b) High (Ans.) Compared to the other ionospheric layers A. When sky wave intensity is the C. (a) Horizontal (b) High at higher altitudes, the ionization density greatest D. (a) Horizontal (b) Low of the D layer is B. When collision of particles is least C. When the density of the ionized layer The long-range VLF broadcasts are A. about the same is the greatest (Ans.) possible because of the advantages of B. relatively low (Ans.) D. When precipitation is greatest which of the following types of C. relatively high propagation? D. None of the above Which of the following layers provide the greatest amount of absorption to the A. Diffraction What two layers in the ionosphere ionospheric wave? B. Ionospheric refraction (Ans.) recombine and largely disappear at night? C. Repeated reflection and refraction A. D and E (Ans.) D. Both B and C above A. D and F (Ans.) B. D and F1 B. D and E C. E and F1 A space wave (a) is primarily a result of C. E and F2 D. F1 and F2 refraction in what atmospheric layer and D. F1 and F2 (b) extends approximately what distance If the signal strength of an incoming beyond the horizon? For HF-radio communications covering signal is reduced for a prolonged period, long distances, what is the most important what type of fading is most likely A. (a) Ionosphere (b) One-tenth farther layer of the ionosphere? involved? B. (a) Ionosphere (b) One-third farther C. (a) Troposphere (b) One-third farther A. C A. Selective (Ans.) B. D B. Multipath D. (a) Troposphere (b) One-tenth farther C. E C. Absorption (Ans.) D. F (Ans.) D. Polarization The signal of a space wave is sometimes significantly reduced at the receiving site Refraction of a sky wave in the Radio waves that arrive at a receiving site because of which of the following ionosphere is influenced by which of the along different paths can cause signal interactions? following factors? fading if these waves have different A. Space-wave refraction A. Ionospheric density A. velocities B. Space-wave reflections B. Frequency of the wave B. amplitudes C. Ground-wave diffraction C. Angle of incidence of the wave C. phase relationships (Ans.) D. Ground-wave reflections (Ans.) D. All of the above (Ans.) D. modulation percentages For long-range communications in the HF A 10-MHz wave entering the ionosphere The technique of reducing multipath band, which of the following types of at an angle greater than its critical angle fading by using several receiving antennas waves is most satisfactory? will pass through the ionosphere and be at different locations is known as what lost in space unless which of the type of diversity? A. Sky wave (Ans.) following actions is taken? B. Space wave A. Space (Ans.) C. Surface wave A. The ground wave is canceled B. Receiver D. Reflected ground wave B. The frequency of the wave is C. Frequency increased (Ans.) D. Modulation Ionization in the atmosphere is produced C. The frequency of the wave is chiefly by which of the following types of decreased The amount of RF energy lost because of radiation? D. The ground wave is reinforced ground reflections depends on which of the following factors? 4 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 A. Angle of incidence D. Each of the above (Ans.) At frequencies above 100 MHz, the B. Ground irregularities greatest attenuation of RF energy from C. Frequency of the wave A sudden and intense burst of ultraviolet raindrops is caused by which of the D. Each of the above (Ans.) light is especially disruptive to following factors? communications in which of the following A. Ducting Receiving sites located near industrial frequency bands? B. Heat loss areas can expect to have exceptionally C. Scattering (Ans.) large losses in signal quality as a result of A. HF D. Absorption which of the following propagation B. MF (Ans.) situations? C. LF Under certain conditions, such as ducting, D. VLF line-of-sight radio waves often propagate A. Absorption for distances far beyond their normal B. Multihop refraction The density of what ionosphere layer ranges because of which of the following C. Natural interference increases because of a violent eruption on factors? D. Man-made interference (Ans.) the surface of the sun? A. Low cloud masses Which of the following ionospheric A. D (Ans.) B. Ionospheric storms variation causes densities to vary with the B. E C. Temperature inversions (Ans.) axial rotation of the sun? C. F1 D. Frequency fluctuations D. F2 A. Daily variation (Ans.) When ducting is present in the B. Seasonal variation Which irregular variation in ionospheric atmosphere, multihop refraction of line- C. 27-day sunspot cycle conditions can cause a waiting period of of-sight transmission can occur because of D. 11-year sunspot cycle several days before communications which of the following factors? return to normal? Which of the following ionospheric A. Operating frequency of the variation causes densities to vary with the A. Sporadic E transmitter position of the earth in its orbit around the B. Ionospheric storms B. Height of the transmitting antenna sun? C. Sudden ionospheric disturbance C. Angle of incidence of the radio wave (Ans.) D. Each of the above (Ans.) A. Daily variation D. Each of the above B. Seasonal variation (Ans.) A propagation technique used to extend C. 27-day sunspot cycle For a radio wave entering the atmosphere UHF transmission range beyond the D. 411-year sunspot cycle of the earth at a given angle, the highest horizon uses which of the following frequency at which refraction will occur is propagation characteristics? Which of the following ionospheric known by which of the following terms? variation causes densities to vary with the A. Ground reflection time of the day? A. Usable frequency B. Ionospheric scatter B. Refraction frequency C. Tropospheric scatter (Ans.) A. Daily variation (Ans.) C. Maximum usable frequency (Ans.) D. Atmospheric refraction B. Seasonal variation D. Optimum working frequency C. 27-day sunspot cycle Communications by tropospheric scatter D. 11-year sunspot cycle The most consistent communications can can be affected by which of the following be expected at which of the following conditions? What relative range of operating frequencies? frequencies is required during periods of A. Sunspot activity maximum sunspot activity? A. Critical frequency B. Atmospheric conditions (Ans.) B. Maximum usable frequency C. Ionospheric disturbances A. Lower C. Maximum working frequency D. All of the above B. Medium D. Optimum working frequency (Ans.) C. Higher (Ans.) What effect, if any, does the radiation D. None of the above If the optimum working frequency for a angle of a transmitting antenna have on communications link is 4,250 kHz, what the reception of communications by What factor significantly affects the is the approximate maximum usable tropospheric scatter? frequency of occurrence of the sporadic-E frequency? layer? A. The lower the angle, the weaker the A. 4,500 kHz signal A. Seasons B. 5,000 kHz (Ans.) B. The lower the angle, the stronger the B. Latitude (Ans.) C. 5,500 kHz signal C. Weather conditions D. 4.6,000 kHz C. The lower the angle, the more D. Ionospheric storms susceptible the signal is to distortion In determining the success of radio D. None of the above (Ans.) What effect can the sporadic-E layer have transmission, which of the following on the propagation of sky waves? factors is the LEAST predictable? Which of the following descriptions of tropospheric scatter signal reception is A. Causes multipath interference A. Antenna capabilities NOT true? B. Permits long distance B. Weather conditions along the path of communications at unusually high communication (Ans.) A. Receiver signal strength decreases as frequencies C. Density of ionized layers the turbulence height is increased C. Permits short-distance D. Presence of ionized layers (Ans.) communications in the normal skip B. The level of reception depends on the zone number of turbulences causing scatter 5 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 C. The energy received is the portion of the wave reradiated by the turbulence Uniform capacitance throughout the A. Expected value of current flow D. Increased communications distance length of the line is an advantage of which through the insulation (Ans.) enables more turbulence to act on the of the following transmission lines? B. Expected value of voltage supplied signal, thereby raising the received A. Coaxial line by the transmitter signal level B. Twisted pair C. Value of the lump and distributed C. Shielded pair (Ans.) constants of the line divided by The tropospheric scatter signal is often D. Two-wire open line impedance characterized by very rapid fading caused D. Value of the lump and distributed by which of the following factors? What is the primary advantage of a rigid constants of the line divided by coaxial line? impedance A. Extreme path lengths B. Multipath propagation (Ans.) A. Low radiation losses (Ans.) Electrical constants in a transmission line C. Turbulence in the atmosphere B. Inexpensive construction are distributed in which of the following D. Angle of the transmitted beam C. Low high-frequency losses ways? D. Each of the above For which of the following A. Into a single device communications situations would Which of the following wave-guides is B. Along the length of the line (Ans.) turbulence in the troposphere scatter seldom used because of its large energy C. According to the thickness of the line transmission? loss characteristics? D. According to the cross-sectional area of the line A. 10 MHz, range 200 miles A. Metallic B. 30 MHz, range 800 miles B. Dielectric (Ans.) Leakage current in a two-wire C. 50 MHz, range 600 miles C. Elliptical transmission line is the current that flows D. 100 MHz, range 400 miles (Ans.) D. Cylindrical through what component? A transmission line is designed to perform To some degree, transmission lines A. The resistor (Ans.) which of the following functions? always exhibit which of the following B. The inductor types of losses? C. The insulator A. Disperse energy in all directions D. The conductor B. Detune a transmitter to match the A. I2 R load B. Inductor Conductance is the reciprocal of what C. Guide electrical energy from point to C. Dielectric electrical property? point (Ans.) D. Each of the above (Ans.) D. Replace the antenna in a A. Inductance communications system Skin effect is classified as which of the B. Resistance (Ans.) following types of loss? C. Capacitance All transmission lines must have two D. Reciprocity ends, the input end and the output end. A. Copper (Ans.) What other name is given to the input B. Voltage A transmission line that has current end? C. Induction flowing through it has which, if any, of D. Dielectric the following fields about it? A. Sending end B. Generator end What transmission-line loss is caused by A. Electric field only C. Transmitter end magnetic lines of force not returning to B. Magnetic field only D. Each of the above (Ans.) the conductor? C. Both electric and magnetic fields (Ans.) A measurement of the voltage to current A. Copper D. None of the above ratio (Ein/Iin) at the input end of a B. Radiation (Ans.) transmission line is called the C. Induction Maximum transfer of energy from the D. Dielectric source to the transmission line takes place A. input-gain rate when what impedance relationship exists B. input impedance (Ans.) What is the electrical wave-length of 1 between the source and the transmission C. output impedance cycle if the frequency is 60 Hz? line? D. voltage-gain ratio A. 125,000 meters A. When the load impedance equals Which of the following lines is NOT a B. 1,250,000 meters source impedance (Ans.) transmission medium? C. 5,000,000 meters (Ans.) B. When the load impedance is twice the D. 20,000,000 meters source impedance A. Load line (Ans.) C. When the load impedance is half the B. Coaxial line A transmission line 10 meters in length is source impedance C. Two-wire line considered to be electrically long at which D. When the load impedance is one- D. Twisted-pair line of the following frequencies? fourth the source impedance Electrical power lines are most often A. 60 kHz (Ans.) The characteristic impedance (Z0) of a made of which of the following types of B. 600 kHz transmission line is calculated by using transmission lines? C. 6 MHz which of the following ratios? D. 60 MHz A. Twin-lead line A. Rs to Rload of the line B. Shielded-pair line The conductance value of a transmission B. Imax to Imin at every point along the C. Two-wire open line (Ans.) line represents which of the following line D. Two-wire ribbon line values? 6 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 C. E to I at every point along the line D. They are evenly distributed along the The total charge on a transmission line is (Ans.) line (Ans.) equal to the current multiplied by which D. Ein to Eo of the line The initial waves that travel from the of the following factors? source to the load of a transmission line For a given voltage, what determines the are referred to as what type of waves? A. Time (Ans.) amount of current that will flow in a B. Power transmission line? A. Incident (Ans.) C. Voltage B. Refracted D. Resistance A. Conductance C. Reflected B. Spacing of the wires D. Diffracted The characteristic impedance for an C. Diameter of the wires infinite transmission line can be figured D. Characteristic impedance (Ans.) Waves that travel from the output end to using which of the following ratios? the input end of a transmission line are When the impedance of a transmission referred to as what type of waves? A. Input current to velocity line is measured, which of the following B. Input voltage to input current (Ans.) values frequently is NOT considered? A. Incident C. Input voltage to line resistance B. Refracted D. Input current to line resistance A. Inductance C. Reflected (Ans.) B. Resistance D. Diffracted If a transmission line is open-ended, C. Conductance (Ans.) which of the following conditions D. Capacitance When a dc voltage is applied to the describes its terminating impedance? equivalent infinite line in the figure, The characteristic impedance of a long which of the following conditions occurs A. Finite transmission line may be determined by along the length of the line? B. Infinitely large (Ans.) using which of the following methods? C. Equal to load impedance A. Standing waves of voltage form D. Equal to source impedance A. Trial and error B. Standing waves of current form B. Calculating the impedance of the C. Current flows indefinitely (Ans.) When a transmission line is not entire line D. Voltage appears for a short time terminated in its characteristic impedance C. Calculating the impedances at each (Z0), what happens to the incident energy end of the line Compared to a dc input, what relative that is NOT transferred to the load? D. Adding the impedances of successive amount of time is required for an ac input short sections (Ans.) voltage to travel the length of the line A. It is returned along the transmission shown in the circuit? line (Ans.) When should lumped values for B. It is radiated into space transmission-line constants be used to A. Less C. It is absorbed by the line calculate characteristic impedance? B. Same (Ans.) D. It is converted to heat energy C. More A. When the line is short compared to D. None of the above When the dc voltage reaches the open end one wavelength (Ans.) of the transmission line in the figure and B. When the line is long compared to The instantaneous voltage on an infinite is reflected, it has which, if any, of the one wavelength transmission line can be plotted against following changes? C. When the line is infinitely long time by using which of the following D. None of the above instruments? A. Increased amplitude B. Decreased amplitude In actual practice, the characteristic A. A wavemeter C. The opposite polarity impedance of a transmission line is B. A multimeter D. None of the above (Ans.) usually within which of the following C. An oscilloscope (Ans.) resistance ranges? D. A spectrum analyzer When the dc current reaches the open end of the transmission line and is reflected, it A. 0 to 0.9 ohm On an infinite transmission line with an ac has which, if any, of the following B. 1 to 49 ohms voltage applied, which of the following is changes? C. 50 to 600 ohms (Ans.) an accurate description of the effective D. 601 to 1,000 ohms voltage distribution along the line? A. Increased amplitude B. Decreased amplitude The input impedance of a transmission A. Voltage is 0 at all points C. The opposite polarity (Ans.) line is affected by which of the following B. Voltage is constant at all points D. None of the above properties? C. Voltage varies at a sine-wave rate (Ans.) When the dc voltage reaches the shorted A. Radiation loss D. Voltage varies at double the sine- end of the transmission line, it is reflected. B. Series inductance wave rate It has which, if any, of the following C. Parallel capacitance changes? D. Each of the above (Ans.) The velocity of propagation on a transmission line is controlled by which A. Increased amplitude When a dc voltage is applied to a of the following line characteristics? B. Decreased amplitude transmission line and the load absorbs all C. The opposite polarity (Ans.) the energy, what is the resulting A. Conductance D. None of the above relationship between current and voltage? B. Inductance only C. Capacitance only When the dc current reaches the shorted A. They are in phase with each other D. Capacitance and inductance (Ans.) end of the transmission line, it is reflected. B. They are equal to Z0 of the line It has which, if any, of the following C. They are out of phase with each other changes? 7 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 The resultant waveform obtained by A. Nonresonant A. Decrease amplitude adding the incident wave to the reflected B. Series-resonant B. Increase amplitude wave is referred to as a/an C. Parallel-resonant (Ans.) C. Increased polarity D. Each of the above D. None of the above (Ans.) A. standing wave (Ans.) B. negative wave When a series-resonant circuit is resonant In an open-ended transmission line with C. algebraic wave at a frequency above the generator an ac signal applied, what is the phase D. concentrated wave frequency, it acts as what type of circuit? relationship between the incident and reflected voltage waves? On an open-ended transmission line, what A. Open is the phase relationship between the B. Resistive A. In phase standing waves of voltage and current? C. Inductive B. 45 degrees out of phase D. Capacitive (Ans.) C. 90 degrees out of phase A. In phase D. 180 degrees out of phase (Ans.) B. 45 degrees out of phase Which of the following sections of C. 90 degrees out of phase (Ans.) transmission line can be used as a The resultant of the incident and reflected D. 180 degrees out of phase parallel-resonant circuit? voltage waves is called the standing wave. Its value is figured by using which of the Which of the following conditions exist at A. A shorted 1/4-wavelength section following procedures? the end of a shorted transmission line? (Ans.) B. An open 1/4-wavelength section A. Adding the effective values of the A. Maximum voltage and minimum C. A shorted 1/2-wavelength section two waveforms current D. An open 3/4-wavelength section B. Algebraically adding the B. Maximum voltage and maximum instantaneous values of the two current A generator connected to an open-ended waveforms (Ans.) C. Minimum voltage and maximum line greater than 1/4 wave-length but less C. Algebraically subtracting the current (Ans.) than 1/2 wave-length senses which of the instantaneous values of the two D. Minimum voltage and minimum following circuit component waveforms current characteristics? D. Taking the square root of the product of the incident and reflected voltages Transmission line is considered to be A. Zero reactance nonresonant (flat) when it is terminated in B. Low resistance On an open-ended transmission line that which of the following ways? C. Inductive reactance is carrying an ac signal, what is the total D. Capacitive reactance (Ans.) number of moving voltage waves? A. In an impedance equal to Z0 (Ans.) B. In an impedance that is infinite Which of the following conditions of A. One C. In an inductive reactance greater than current (I) and impedance (Z) exist at B. Two (Ans.) Z0 even quarter-wave points on a shorted C. Three D. In a capacitive reactance greater than transmission line? D. Four Z0 A. Low I, low Z At the end of an open-ended transmission Of the following terms, which one is used B. Low I, high Z line, which, if any, of the following for the nonresonant transmission line? C. High I, high Z voltage waves is at its maximum value? D. High I, low Z (Ans.) A. A tuned line A. Incident (Ans.) B. A shorted line What is the maximum distance, in B. Reflected C. An untuned line (Ans.) wavelengths (), between adjacent zero- C. Resultant D. A terminated line current points on an open-circuited line? D. None of the above A transmission line that is resonant is A. 1 On a transmission line that is carrying an sometimes referred to as which of the B. 1/2  (Ans.) ac signal, what is the relative value of the following types of lines? C. 1/4  resultant voltage wave 1/4 wavelength D. 1/8  from the open end? A. Tuned (Ans.) B. Matched When a line is terminated in a A. Maximum positive C. Untuned capacitance, the capacitor performs B. Maximum negative D. Unmatched which, if any, of the following circuit C. Zero (Ans.) actions? D. Infintiy A short-circuited section of transmission line that is an odd number of quarter- A. It absorbs all the energy In an open-ended transmission line, the wavelengths long shows the same B. It reflects all the energy (Ans.) resultant ac current waveform is always characteristics as which of the following C. It reacts as if it were a short zero at what point(s)? devices? D. None of the above A. At the open end only A. A series-resonant circuit When a transmission line is terminated in B. 1/2 wavelength from the open-end B. A parallel-resonant circuit (Ans.) an inductive reactance, which, if any, of only C. An inductive reactance equal to Z0 the following phase shifts takes place with C. At the open end and 1/2 wavelength D. A capacitive reactance equal to Z0 respect to the current and voltage? from the open-end(Ans.) D. None of the above Which of the following circuits appears as A. Only voltage is phase-shifted a very high resistance at resonance? B. Only current is phase-shifted 8 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 C. Both voltage and current are phase- A device used to radiate or receive B. 1/2 cycle shifted (Ans.) electromagnetic wave energy is referred C. 1/4 cycle (Ans.) D. None of the above to as a/an D. 1/8 cycle When a transmission line is terminated in A. feeder On a standing wave, the points of high a resistance greater than Z0, which of the B. antenna (Ans.) current and voltage are identified by following conditions exist? C. transmitter which of the following terms? The end of the line appears as an open D. coupling device A. Peaks (Ans.) circuit (Ans.) B. Nodes A. Standing waves appear on the line An antenna that can be mounted to radiate C. Poles B. Voltage is maximum and current is rf energy either vertically or horizontally D. Loops minimum at the end of the line is classified as which of the following C. Each of the above types? The presence of standing waves indicates which of the following conditions of an On a transmission line, reflections begin A. Hertz (Ans.) antenna? at which of the following locations? B. Marconi C. Quarter-wave A. Resonance (Ans.) A. At the load (Ans.) D. Both B and C above B. Saturation B. At the source C. Nonresonance C. At the middle A complete antenna system consists of D. Minimum efficiency D. At the half-wavelength point which of the following components? The antenna property that allows the same The ratio of maximum voltage to A. A feeder, a coupling device, and a antenna to both transmit and receive minimum voltage on a transmission line is transmitter energy is referred to as the B. A feeder line, a coupling device, and an antenna (Ans.) A. gain A. RSWR C. An antenna, a transmission line, and a B. resonance B. PSWR receiver C. reciprocity (Ans.) C. VSWR (Ans.) D. An impedance-matching device, a D. directivity D. ISWR feeder, and a transmission line What component in an antenna system There is a ratio between the amount of Which of the following ratios samples the transfers energy from the transmitter to energy propagated in certain directions by magnetic field along a line? the antenna? a directional antenna compared to the energy that would be propagated in these A. VSWR A. A feeder (Ans.) directions if the antenna were not B. PSWR B. A delay line directional. This ratio is known as which C. ISWR (Ans.) C. A choke joint of the following antenna characteristics? D. RSWR D. A rotating joint A. Gain (Ans.) Radio energy is transmitted through The type, size, and shape of an antenna B. Directivity which of the following mediums? are determined by which of the following C. Reciprocity factors? D. Polarization A. Rock B. Soil A. Power output of the transmitter The polarization plane of the radiation C. Water B. Transmitter frequency field is determined by which of the D. Space (Ans.) C. Direction to the receiver following fields? D. Each of the above (Ans.) Energy is transmitted from a transmitter A. Electric field only into space using which of the following Moving electric and magnetic fields in B. Magnetic field only devices? space have what (a) phase and (b) angular C. Electromagnetic field (Ans.) relationships? D. None of the above A. A receiver B. A delay line A. (a) In phase (b) Perpendicular For best reception of a signal from a C. A receiving antenna B. (a) In phase (b) Displaced 45º horizontally polarized antenna, the D. A transmitting antenna (Ans.) C. (a) Out of phase (b) Displaced 45º receiving antenna should be mounted so D. (a) Out of phase (b) Perpendicular that it has what relationship with the Transmitted RFenergy takes what form as (Ans.) transmitting antenna? it is sent into space? What is the length of each half of the wire A. 0 degrees (Ans.) A. A magnetic field only for a dipole antenna? B. 45 degrees B. An electric field only C. 90 degrees C. An electromagnetic field (Ans.) A. Wavelength D. 135 degrees D. A static dielectric field B. 3/4 wavelength C. 1/2 wavelength An electric field that rotates as it travels The dimensions of a transmitting antenna D. 1/4 wavelength (Ans.) through space exhibits what type of are determined by which of the following polarization? factors? On a dipole antenna, the sinusoidal variation in charge magnitude lags the A. Vertical A. Transmitted power sinusoidal variation in current by what B. Spherical B. Transmitted frequency (Ans.) amount? C. Elliptical (Ans.) C. Distance to the receiver D. Horizontal D. Antenna height above the ground A. 1 cycle 9 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 For ground-wave transmissions, what type D. Omnidirectional (Ans.) C. Both A and B above (Ans.) of polarization is required? D. Spherical in all planes An ordinary flashlight is an example of A. Vertical (Ans.) what type of radiator? A method of feeding energy to a half- B. Spherical wave antenna is to connect one end C. Elliptical A. Isotropic through a capacitor to the output stage. D. Horizontal B. Polarized What is this method of feeding called? For high-frequency operation, which of C. Anisotropic (Ans.) the following antenna polarization D. Stroboscopic A. End feed patterns is preferred? B. Voltage feed How many points on the graph can C. Both A and B above (Ans.) A. Vertically polarized represent the value of 7 radiation units at D. Current feed B. Spherically polarized position 2 of the circle? C. Elliptically polarized An antenna supplied by the center-feed D. Horizontally polarized (Ans.) A. One (Ans.) method is fed at what point? B. Two Omnidirectional transmission is obtained C. Three A. Low voltage and low current from which of the following antennas? D. Four B. Low voltage and high current (Ans.) C. High voltage and low current A. Elliptically polarized Compared with the rectangular-coordinate D. High voltage and high current B. Horizontal half-wave graph, the polar-coordinate graph has the C. Vertical half-wave (Ans.) advantage of showing which of the The basic Marconi antenna has which of D. Each of the above following antenna characteristics? the following characteristics? With an antenna height of 40 feet and a A. Polarization A. One-quarter wavelength and transmitter frequency of 90 megahertz, B. Radiation pattern (Ans.) ungrounded which of the following antenna radiation C. Phase relationship B. One-half wavelength and grounded at patterns is best for transmitting over D. Gain versus directivity one end bodies of water? C. One-half wavelength and insulated The area enclosed by the radiation pattern from ground A. Vertically polarized (Ans.) is the D. One-quarter wavelength and B. Spherically polarized grounded at one end (Ans.) C. Elliptically polarized A. lobe (Ans.) D. Horizontally polarized B. null The Marconi antenna behaves as a dipole C. axis for which of the following reasons? To select a desired signal and discriminate D. coordinate against interfering signals from strong vhf A. It is fed at one end and uhf broadcast transmissions, which of Inserting an inductor or capacitor in series B. An image antenna is formed by the following actions should you take? with an antenna is one method of reflections from the ground (Ans.) electrically changing the electrical length C. A quarter-wavelength of conductor is A. Increase receiver gain (Ans.) of an antenna. What is this method buried in the ground and forms the B. Make the transmitting antenna bi- called? rest of the dipole directional D. The applied signal is rectified so that C. Use a vertically polarized receiving A. Loading (Ans.) only half the signal will appear on the antenna B. Inserting quarter-wave antenna D. Use narrowly directional arrays as C. Unloading receiving antennas D. Decoupling A series of conductors arranged in a radial pattern and buried in the ground beneath A vertically mounted transmission line is Many complex antennas are constructed the antenna is referred to as a LEAST affected by which of the from what basic antenna? following antenna radiation patterns? A. ground spur A. The Marconi antenna (Ans.) B. counterpoise (Ans.) A. Vertically polarized B. The full-wave antenna C. ground screen B. Spherically polarized C. The half-wave antenna D. ground reflector C. Horizontally polarized (Ans.) D. The quarter-wave antenna D. Elliptically polarized A folded dipole can be used instead of a On an energized half-wave antenna, simple, center-fed dipole for which of the An antenna with which of the following which of the following electrical following purposes? radiation resistance values will exhibit conditions exist? reduced efficiency? A. Matching voltage A. Voltage is maximum at the ends B. Matching impedance (Ans.) A. 39 ohms B. Voltage is minimum at the ends C. Increasing directivity B. 82 ohms (Ans.) (Ans.) D. Decreasing directivity C. 107 ohms C. Current is maximum at the ends D. 150 ohms D. Impedance is minimum at the center An antenna arrangement that has elements aligned in a straight line is referred to as An isotropic radiator radiates energy in Which of the following radiation patterns what type array? which of the following patterns? is/are exhibited by a simple vertical doublet antenna? A. Isotropic A. Vertical B. Collinear (Ans.) B. Bi-directional A. Nondirectional in the horizontal plane C. Line-of-sight C. Unidirectional B. Directional in the vertical plane D. Unidirectional 10 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 elements is which of the following C. Spacing between parasitic and driven To have current in two adjoining collinear distances? elements half-wave elements in proper phase, they D. Each of the above (Ans.) must be connected by which of the A. One-half wavelength following stubs? B. One-quarter wavelength The advantages of unidirectivity and C. Greater than one-half wavelength increased gain can best be obtained by A. A shorted half-wave stub (Ans.) (Ans.) using which of the following elements in B. An open quarter-wave stub D. Slightly less than one-quarter a parasitic array? C. A shorted eighth-wave stub D. A shorted quarter-wave stub An end-fire array physically resembles the A. Driven elements only collinear array except that it is more B. Reflector and director elements only To select a desired signal and discriminate compact. What disadvantage does the (Ans.) against interfering signals, the receiving endfire array possess? C. Reflector, director, and driven antenna should have which of the elements following characteristics? A. It has lower gain D. Driven and director elements only B. It has low radiation resistance (Ans.) A. Be omnidirectional C. It has loose coupling The ratio of energy radiated by an array in B. Be highly directional (Ans.) D. Each of the above the principal direction of radiation to the C. Be vertically polarized energy radiated in the opposite direction D. Be horizontally polarized What is the range of electrical spacing describes which of the following between the elements of an end-fire relationships? Adding more elements to a collinear array? antenna array produces which of the A. Side-to-side ratio following effects? A. 3/4 to 1 wavelength B. Front-to-back ratio (Ans.) B. 1/2 to 3/4 wavelength C. Driven-to-parasitic ratio A. Increased gain (Ans.) C. 1/4 to 1/2 wavelength D. Reflector-to-director ratio B. Decreased gain D. 1/8 to 1/4 wavelength (Ans.) C. Decreased directivity The Yagi antenna is an example of what D. Mismatched impedances The end-fire array produces what type of type of antenna array? lobes, if any, along the axis of the array? What is the maximum number of A. Driven elements ordinarily used in a collinear A. Minor lobes (Ans.) B. End-fire array? B. Major lobes C. Multielement parasitic (Ans.) C. Nulls D. Single-element parasitic A. One D. None of the above B. Two The addition of parasitic elements to the C. Three Assuming that the elements are correctly Yagi antenna has which of the following D. Four (Ans.) spaced, the directivity of an end-fire array effects on antenna characteristics? may be increased by which of the Constructing a collinear array with following actions? A. Increased gain elements longer than 1/2 wavelength has B. Narrower beam width which of the following effects on antenna A. Increasing the frequency C. Narrower frequency response characteristics? B. Decreasing the frequency D. Each of the above (Ans.) C. Decreasing the number of elements A. Increased gain D. Increasing the number of elements An antenna which is designed especially B. Decreased gain (Ans.) for vertically-polarized ground waves at C. Increased frequency range (Ans.) low frequencies is the D. Decreased frequency range A unidirectional pattern can be obtained from an end-fire array by using what A. Yagi antenna In a two-element collinear array, phase relationship between the energy fed B. Marconi antenna maximum gain is obtained when the to adjacent elements? C. Beverage antenna (Ans.) center-to-center spacing between the ends D. V antenna of the elements is approximately what A. 0º electrical distance? B. 45º What is the phase relationship of the C. 90º (Ans.) signals that feed the V antenna? A. Wavelength D. 180º B. 0.15 wavelength A. 0º C. 0.5 wavelength Energy is fed to a parasitic element using B. 45º D. 0.75 wavelength (Ans.) what method? C. 90º D. 180º (Ans.) Compared with collinear arrays, broadside A. Direct coupling arrays have which of the following B. Inductive coupling (Ans.) A rhombic antenna is essentially a advantages? C. Capacitive coupling combination of which of the following D. Transmission-line coupling antennas? A. Sharper tuning (Ans.) B. Broader bandwidth The directivity pattern resulting from the A. Two stacked long-wire radiators C. Broader frequency response action of parasitic elements depends on B. Two V antennas placed side by side D. Less coupling between dipole which of the following element (Ans.) characteristics? C. Two collinear arrays in parallel Optimum gain is obtained from a D. Four parallel half-wave radiators broadside array when the spacing of its A. Length of the element B. Diameter of the element 11 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 A rhombic antenna has which of the go aloft until which of the following Which of the following dielectrics is used following advantages? requirements are met? in waveguides? A. Simple construction A. A safety harness has been issued to A. Air (Ans.) B. Wide frequency range you B. Mica C. Noncritical adjustment B. All transmitters are secured and C. Insulating oil D. Each of the above (Ans.) tagged D. Insulating foam C. A working aloft "chit" has been filled The principal disadvantage of the rhombic out and signed by proper authority Which of the following characteristics of antenna is its (Ans.) a waveguide causes the lower-frequency D. Each of the above limitation? A. poor directivity B. large antenna site The portion of the electromagnetic A. I2R loss C. low antenna voltage (Ans.) spectrum which falls between 1,000 and B. Physical size (Ans.) D. high-frequency inefficiency 100,000 MHz is referred to as which of C. Wall thickness the following regions? D. Dielectric loss The unidirectional radiation pattern of the rhombic antenna is caused by which of A. X-ray At very high frequencies, ordinary the following antenna characteristics? B. Infrared insulators in a two-wire transmission line C. Microwave (Ans.) display the characteristics of what A. Size D. Ultra-violet electrical component? B. Shape C. Termination resistance (Ans.) Microwave theory is based on the action A. An inductor D. Frequency of the input energy of which of the following fields? B. A resistor C. A capacitor (Ans.) Horizontal half-wave antennas mounted at A. Electric field only D. A transformer right angles to each other in the same B. Magnetic field only horizontal plane make up which of the C. Electromagnetic field (Ans.) At very high frequencies, which of the following antennas? D. None of the above following devices works best as an insulator? A. Rhombic Coaxial lines are more efficient than two- B. Flat-top wire lines at microwave frequencies for A. Open half-wave section C. Turnstile (Ans.) which of the following reasons? B. Open quarter-wave section D. Ground-plane C. Shorted half-wave section A. Because electromagnetic fields are D. Shorted quarter-wave section (Ans.) The most common means of obtaining a completely confined in coaxial lines low-radiation angle from a vertical (Ans.) The range of operating frequencies is quarter-wave antenna is by what B. Because electromagnetic fields are determined by which of the following procedure? not completely confined in coaxial wave-guide dimensions? lines A. Decreasing power C. Because coaxial lines have less A. The widest (Ans.) B. Increasing frequency resistance to current flow than two- B. The longest C. Adding a ground plane (Ans.) wire transmission lines C. The shortest D. Rotating the antenna to a horizontal D. Each of the above D. The narrowest plane The most efficient transfer of If frequency is decreased, what change, if A corner reflector antenna is used for electromagnetic energy can be provided any, will be required in the dimensions of which of the following purposes? by which of the following mediums? the wave-guide bus bar? A. To decrease frequency range A. Waveguides (Ans.) A. Decrease in dimensions (Ans.) B. To increase frequency range B. Twin-lead flat lines B. Increase in dimensions C. To produce a unidirectional pattern C. Single-conductor lines C. Either A or B (Ans.) D. Coaxial transmission lines D. Neither A nor B D. To produce an omnidirectional pattern Copper (I2R) losses are reduced by what The cutoff frequency for a wave-guide is physical property of waveguides? controlled by the physical dimensions of If a corner-reflector antenna is the wave-guide and is defined as the horizontally polarized, its radiation A. Small surface area frequency at which two quarter- pattern will take on what shape? B. Large surface area (Ans.) wavelengths are C. Shape of the waveguide A. A narrow beam in the horizontal D. Waveguide material used A. shorter than the "a" dimension plane B. shorter than the "b" dimension B. A narrow beam in the vertical plane In a coaxial line, the current-carrying area C. longer than the "b" dimension (Ans.) of the inner conductor is restricted to a D. longer than the "a" dimension (Ans.) C. A beam similar to a half-wave dipole small surface layer because of which of in the horizontal plane the following properties? In practical applications, which of the D. A beam similar to a half-wave dipole following dimensions describes the wide with a reflector in the vertical plane A. Skin effect (Ans.) dimension of the wave-guide at the B. Copper loss operating frequency? When radio or radar antennas are C. Conductor density energized by transmitters, you must not D. Temperature effect A. 0.1 wavelength B. 0.2 wavelength 12 Excel Review Center ECE Refresher/Coaching Course EST TH 2-Part 1 C. 0.5 wavelength D. Angle of penetration With the mode description, TE1, 1, what D. 0.7 wavelength (Ans.) maximum number of half-wave patterns How does the group velocity of an exist across the diameter of a circular Which of the following fields is/are electromagnetic field in a waveguide waveguide? present in wave guides? compare to the velocity of a wavefront through free space? A. One (Ans.) A. E field only B. Two B. H field only A. Group velocity is faster C. Three C. E and H fields (Ans.) B. Group velocity is slower (Ans.) D. Four D. Stationary field C. Their velocities are the same D. None of the above To inject or remove energy from a A difference in potential across a waveguide, which of the following dielectric causes which of the following The group velocity of a wavefront in a devices could you use? fields to develop? waveguide may be increased by which of A. Electric field only the following actions? A. Slot B. Magnetic field only A. Decreasing the frequency of the input B. Loop C. Electromagnetic field (Ans.) energy C. Probe D. None of the above B. Increasing the frequency of the input D. Each of the above (Ans.) energy (Ans.) What information is indicated by the C. Increasing the power of the input Loose coupling is a method used to number of arrows between the plates of energy reduce the amount of energy being the capacitor? D. Decreasing the power of the input transferred from a waveguide. How is energy loose coupling achieved when using a A. The amount of capacitance probe? B. The amount of current flow The various field configurations that can C. The strength of the electric field exist in a waveguide are referred to as A. By doubling the size of the probe (Ans.) B. By increasing the length of the probe D. The strength of the magnetic field A. wavefronts C. By decreasing the length of the probe B. modes of operation (Ans.) (Ans.) H lines have which of the following C. fields of operation D. By placing the probe directly in the distin