1.04 UTF-8 J 0 0 1243588 E9A01 Which of the following describes an isotropic radiator? 0 A grounded radiator used to measure earth conductivity 0 A horizontal radiator used to compare Yagi antennas 0 A theoretical radiator used to compare other antennas 1 A spacecraft radiator used to direct signals toward the earth 0 E9A02 When is it useful to refer to an isotropic radiator? 0 When comparing the gains of directional antennas 1 When testing a transmission line for standing-wave ratio 0 When directing a transmission toward the tropical latitudes 0 When using a dummy load to tune a transmitter 0 E9A03 How much gain does a 1/2-wavelength dipole have over an isotropic radiator? 0 About 1.5 dB 0 About 2.1 dB 1 About 3.0 dB 0 About 6.0 dB 0 E9A04 Which of the following antennas has no gain in any direction? 0 Quarter-wave vertical 0 Yagi 0 Half-wave dipole 0 Isotropic radiator 1 E9A05 Which of the following describes the radiation pattern of an isotropic radiator? 0 A teardrop in the vertical plane 0 A circle in the horizontal plane 0 A sphere with the antenna in the center 1 Crossed polarized with a spiral shape 0 E9A06 Why would one need to know the feed point impedance of an antenna? 0 To match impedances for maximum power transfer 1 To measure the near-field radiation density from a transmitting antenna 0 To calculate the front-to-side ratio of the antenna 0 To calculate the front-to-back ratio of the antenna 0 E9A07 What factors determine the radiation resistance of an antenna? 0 Transmission-line length and antenna height 0 Antenna location with respect to nearby objects and the conductors' length/diameter ratio 1 It is a physical constant and is the same for all antennas 0 Sunspot activity and time of day 0 E9A08 What is the term for the ratio of the radiation resistance of an antenna to the total resistance of the system? 0 Effective radiated power 0 Radiation conversion loss 0 Antenna efficiency 1 Beamwidth 0 E9A09 What is included in the total resistance of an antenna system? 0 Radiation resistance plus space impedance 0 Radiation resistance plus transmission resistance 0 Transmission-line resistance plus radiation resistance 0 Radiation resistance plus ohmic resistance 1 E9A10 What is a folded dipole antenna? 0 A dipole one-quarter wavelength long 0 A type of ground-plane antenna 0 A dipole whose ends are connected by a one-half wavelength piece of wire 1 A hypothetical antenna used in theoretical discussions to replace the radiation resistance 0 E9A11 What is meant by antenna gain? 0 The numerical ratio relating the radiated signal strength of an antenna to that of another antenna 1 The numerical ratio of the signal in the forward direction to the signal in the back direction 0 The numerical ratio of the amount of power radiated by an antenna compared to the transmitter output power 0 The final amplifier gain minus the transmission-line losses (including any phasing lines present) 0 E9A12 What is meant by antenna bandwidth? 0 Antenna length divided by the number of elements 0 The frequency range over which an antenna can be expected to perform well 1 The angle between the half-power radiation points 0 The angle formed between two imaginary lines drawn through the ends of the elements 0 E9A13 How can the approximate beamwidth of a beam antenna be determined? 0 Note the two points where the signal strength of the antenna is down 3 dB from the maximum signal point and compute the angular difference 1 Measure the ratio of the signal strengths of the radiated power lobes from the front and rear of the antenna 0 Draw two imaginary lines through the ends of the elements and measure the angle between the lines 0 Measure the ratio of the signal strengths of the radiated power lobes from the front and side of the antenna 0 E9A14 How is antenna efficiency calculated? 0 (radiation resistance / transmission resistance) x 100% 0 (radiation resistance / total resistance) x 100% 1 (total resistance / radiation resistance) x 100% 0 (effective radiated power / transmitter output) x 100% 0 E9A15 How can the efficiency of an HF grounded vertical antenna be made comparable to that of a half-wave dipole antenna? 0 By installing a good ground radial system 1 By isolating the coax shield from ground 0 By shortening the vertical 0 By lengthening the vertical 0 E9A16 What theoretical reference antenna provides a comparison for antenna measurements? 0 Quarter-wave vertical 0 Yagi 0 Bobtail curtain 0 Isotropic radiator 1 E9A17 How much gain does an antenna have over a 1/2-wavelength dipole when it has 6 dB gain over an isotropic radiator? 0 About 3.9 dB 1 About 6.0 dB 0 About 8.1 dB 0 About 10.0 dB 0 E9A18 How much gain does an antenna have over a 1/2-wavelength dipole when it has 12 dB gain over an isotropic radiator? 0 About 6.1 dB 0 About 9.9 dB 1 About 12.0 dB 0 About 14.1 dB 0 E9A19 Which of the following describes the directivity of an isotropic radiator? 0 Directivity in the E plane 0 Directivity in the H plane 0 Directivity in the Z plane 0 No directivity at all 1 E9A20 What is meant by the radiation resistance of an antenna? 0 The combined losses of the antenna elements and feed line 0 The specific impedance of the antenna 0 The equivalent resistance that would dissipate the same amount of power as that radiated from an antenna 1 The resistance in the atmosphere that an antenna must overcome to be able to radiate a signal 0 E9B01 What determines the free-space polarization of an antenna? 0 The orientation of its magnetic field (H Field) 0 The orientation of its free-space characteristic impedance 0 The orientation of its electric field (E Field) 1 Its elevation pattern 0 E9B02 In the free-space H-Field radiation pattern shown in Figure E9-1, what is the 3-dB beamwidth? 0 75 degrees 0 50 degrees 1 25 degrees 0 30 degrees 0 E9B03 In the free-space H-Field pattern shown in Figure E9-1, what is the front-to-back ratio? 0 36 dB 0 18 dB 1 24 dB 0 14 dB 0 E9B04 In the free-space H-field pattern shown in Figure E9-1, what is the front-to-side ratio? 0 12 dB 0 14 dB 1 18 dB 0 24 dB 0 E9B05 What information is needed to accurately evaluate the gain of an antenna? 0 Radiation resistance 0 E-Field and H-Field patterns 0 Loss resistance 0 All of these choices 1 E9B06 Which is NOT an important reason to evaluate a gain antenna across the whole frequency band for which it was designed? 0 The gain may fall off rapidly over the whole frequency band 0 The feed-point impedance may change radically with frequency 0 The rearward pattern lobes may vary excessively with frequency 0 The dielectric constant may vary significantly 1 E9B07 What usually occurs if a Yagi antenna is designed solely for maximum forward gain? 0 The front-to-back ratio increases 0 The feed-point impedance becomes very low 1 The frequency response is widened over the whole frequency band 0 The SWR is reduced 0 E9B08 If the boom of a Yagi antenna is lengthened and the elements are properly retuned, what usually occurs? 0 The gain increases 1 The SWR decreases 0 The front-to-back ratio increases 0 The gain bandwidth decreases rapidly 0 E9B09 What type of computer program is commonly used for modeling antennas? 0 Graphical analysis 0 Method of Moments 1 Mutual impedance analysis 0 Calculus differentiation with respect to physical properties 0 E9B10 What is the principle of a Method of Moments analysis? 0 A wire is modeled as a series of segments, each having a distinct value of current 1 A wire is modeled as a single sine-wave current generator 0 A wire is modeled as a series of points, each having a distinct location in space 0 A wire is modeled as a series of segments, each having a distinct value of voltage across it 0 E9C01 What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed 180 degrees out of phase? 0 Unidirectional cardioid 0 Omnidirectional 0 Figure-8 broadside to the antennas 0 Figure-8 end-fire in line with the antennas 1 E9C02 What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 90 degrees out of phase? 0 Unidirectional cardioid 1 Figure-8 end-fire 0 Figure-8 broadside 0 Omnidirectional 0 E9C03 What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed in phase? 0 Omnidirectional 0 Cardioid unidirectional 0 Figure-8 broadside to the antennas 1 Figure-8 end-fire in line with the antennas 0 E9C04 What is the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 180 degrees out of phase? 0 Omnidirectional 0 Cardioid unidirectional 0 Figure-8 broadside to the antennas 0 Figure-8 end-fire in line with the antennas 1 E9C05 What is the radiation pattern for two 1/4-wavelength vertical antennas spaced 1/8-wavelength apart and fed 180 degrees out of phase? 0 Omnidirectional 0 Cardioid unidirectional 0 Figure-8 broadside to the antennas 0 Figure-8 end-fire in line with the antennas 1 E9C06 What is the radiation pattern for two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed in phase? 0 Substantially unidirectional 0 Elliptical 1 Cardioid unidirectional 0 Figure-8 end-fire in line with the antennas 0 E9C07 Which of the following is the best description of a resonant rhombic antenna? 0 Unidirectional; four-sided, each side a half-wavelength long; terminated in a resistance equal to its characteristic impedance 0 Bidirectional; four-sided, each side approximately one wavelength long; open at the end opposite the transmission line connection 1 Four-sided; an LC network at each vertex except for the transmission connection; tuned to resonate at the operating frequency 0 Four-sided, each side of a different physical length; traps at each vertex for changing resonance according to band usage 0 E9C08 What are the advantages of a terminated rhombic antenna? 0 Wide frequency range, high gain and high front-to-back ratio 1 High front-to-back ratio, compact size and high gain 0 Unidirectional radiation pattern, high gain and compact size 0 Bidirectional radiation pattern, high gain and wide frequency range 0 E9C09 What are the disadvantages of a terminated rhombic antenna for the HF bands? 0 A large area for proper installation and a narrow bandwidth 0 A large area for proper installation and a low front-to-back ratio 0 A large area and four sturdy supports for proper installation 1 A large amount of aluminum tubing and a low front-to-back ratio 0 E9C10 What is the effect of a terminating resistor on a rhombic antenna? 0 It reflects the standing waves on the antenna elements back to the transmitter 0 It changes the radiation pattern from essentially bidirectional to essentially unidirectional 1 It changes the radiation pattern from horizontal to vertical polarization 0 It decreases the ground loss 0 E9C11 What type of antenna pattern over real ground is shown in Figure E9-2? 0 Elevation pattern 1 Azimuth pattern 0 E-Plane pattern 0 Polarization pattern 0 E9C12 In the H field antenna radiation pattern shown in Figure E9-2, what is the elevation angle of the peak response? 0 45 degrees 0 75 degrees 0 7.5 degrees 1 25 degrees 0 E9C13 In the H field antenna radiation pattern shown in Figure E9-2, what is the front-to-back ratio? 0 15 dB 0 28 dB 1 3 dB 0 24 dB 0 E9C14 In the H field antenna radiation pattern shown in Figure E9-2, how many elevation lobes appear in the forward direction? 0 4 1 3 0 1 0 7 0 E9C15 How is the far-field elevation pattern of a vertically polarized antenna affected by being mounted over seawater versus rocky ground? 0 The low-angle radiation decreases 0 The high-angle radiation increases 0 Both the high- and low-angle radiation decrease 0 The low-angle radiation increases 1 E9C16 If only a modest on-ground radial system can be used with an eighth-wavelength-high, inductively loaded vertical antenna, what would be the best compromise to minimize near-field losses? 0 4 radial wires, 1 wavelength long 0 8 radial wires, a half-wavelength long 0 A wire-mesh screen at the antenna base, an eighth-wavelength square 1 4 radial wires, 2 wavelengths long 0 E9C17 What is one characteristic of a Beverage antenna? 0 For best performance it must not exceed 1/4 wavelength in length at the desired frequency 0 For best performance it must be mounted more than 1 wavelength above ground at the desired frequency 0 For best performance it should be configured as a four-sided loop 0 For best performance it should be longer than one wavelength 1 E9C18 How would the electric field be oriented for a Yagi with three elements mounted parallel to the ground? 0 Vertically 0 Horizontally 1 Right-hand elliptically 0 Left-hand elliptically 0 E9C19 What strongly affects the shape of the far-field, low-angle elevation pattern of a vertically polarized antenna? 0 The conductivity and dielectric constant of the soil 1 The radiation resistance of the antenna 0 The SWR on the transmission line 0 The transmitter output power 0 E9C20 Why are elevated-radial counterpoises popular with vertically polarized antennas? 0 They reduce the far-field ground losses 0 They reduce the near-field ground losses, compared to on-ground radial systems using more radials 1 They reduce the radiation angle 0 None of these choices is correct 0 E9C21 What is a terminated rhombic antenna? 0 An antenna resonant at approximately double the frequency of the intended band of operation 0 An open-ended bidirectional antenna 0 A unidirectional antenna terminated in a resistance equal to its characteristic impedance 1 A horizontal triangular antenna consisting of two adjacent sides and the long diagonal of a resonant rhombic antenna 0 E9D01 What factors determine the receiving antenna gain required at an amateur satellite station in earth operation? 0 Height, transmitter power and antennas of satellite 1 Length of transmission line and impedance match between receiver and transmission line 0 Preamplifier location on transmission line and presence or absence of RF amplifier stages 0 Height of earth antenna and satellite orbit 0 E9D02 What factors determine the EIRP required by an amateur satellite station in earth operation? 0 Satellite antennas and height, satellite receiver sensitivity 1 Path loss, earth antenna gain, signal-to-noise ratio 0 Satellite transmitter power and orientation of ground receiving antenna 0 Elevation of satellite above horizon, signal-to-noise ratio, satellite transmitter power 0 E9D03 What is the approximate beamwidth of a symmetrical pattern antenna with a gain of 20 dB as compared to an isotropic radiator? 0 10 degrees 0 20 degrees 1 45 degrees 0 60 degrees 0 E9D04 How does the gain of a parabolic dish antenna change when the operating frequency is doubled? 0 Gain does not change 0 Gain is multiplied by 0.707 0 Gain increases 6 dB 1 Gain increases 3 dB 0 E9D05 How is circular polarization produced using linearly polarized antennas? 0 Stack two Yagis, fed 90 degrees out of phase, to form an array with the respective elements in parallel planes 0 Stack two Yagis, fed in phase, to form an array with the respective elements in parallel planes 0 Arrange two Yagis perpendicular to each other, with the driven elements in the same plane, fed 90 degrees out of phase 1 Arrange two Yagis perpendicular to each other, with the driven elements in the same plane, fed in phase 0 E9D06 How does the beamwidth of an antenna vary as the gain is increased? 0 It increases geometrically 0 It increases arithmetically 0 It is essentially unaffected 0 It decreases 1 E9D07 Why does a satellite communications antenna system for earth operation need to have rotators for both azimuth and elevation control? 0 In order to track the satellite as it orbits the earth 1 Because the antennas are large and heavy 0 In order to point the antenna above the horizon to avoid terrestrial interference 0 To rotate antenna polarization along the azimuth and elevate the system towards the satellite 0 E9D08 For a shortened vertical antenna, where should a loading coil be placed to minimize losses and produce the most effective performance? 0 Near the center of the vertical radiator 1 As low as possible on the vertical radiator 0 As close to the transmitter as possible 0 At a voltage node 0 E9D09 Why should an HF mobile antenna loading coil have a high ratio of reactance to resistance? 0 To swamp out harmonics 0 To maximize losses 0 To minimize losses 1 To minimize the Q 0 E9D10 What is a disadvantage of using a trap antenna? 0 It will radiate harmonics 1 It can only be used for single-band operation 0 It is too sharply directional at lower frequencies 0 It must be neutralized 0 E9D11 How must the driven element in a 3-element Yagi be tuned to use a hairpin matching system? 0 The driven element reactance is capacitive 1 The driven element reactance is inductive 0 The driven element resonance is lower than the operating frequency 0 The driven element radiation resistance is higher than the characteristic impedance of the transmission line 0 E9D12 What is the equivalent lumped-constant network for a hairpin matching system on a 3-element Yagi? 0 Pi network 0 Pi-L network 0 L network 1 Parallel-resonant tank 0 E9D13 What happens to the bandwidth of an antenna as it is shortened through the use of loading coils? 0 It is increased 0 It is decreased 1 No change occurs 0 It becomes flat 0 E9D14 What is an advantage of using top loading in a shortened HF vertical antenna? 0 Lower Q 0 Greater structural strength 0 Higher losses 0 Improved radiation efficiency 1 E9D15 What is the approximate input terminal impedance at the center of a folded dipole antenna? 0 300 ohms 1 72 ohms 0 50 ohms 0 450 ohms 0 E9D16 Why is a loading coil often used with an HF mobile antenna? 0 To improve reception 0 To lower the losses 0 To lower the Q 0 To tune out the capacitive reactance 1 E9D17 What is an advantage of using a trap antenna? 0 It has high directivity in the higher-frequency bands 0 It has high gain 0 It minimizes harmonic radiation 0 It may be used for multi-band operation 1 E9D18 What happens at the base feed-point of a fixed length HF mobile antenna as the frequency of operation is lowered? 0 The resistance decreases and the capacitive reactance decreases 0 The resistance decreases and the capacitive reactance increases 1 The resistance increases and the capacitive reactance decreases 0 The resistance increases and the capacitive reactance increases 0 E9D19 What is the beamwidth of a symmetrical pattern antenna with a gain of 30 dB as compared to an isotropic radiator? 0 3.2 degrees 0 6.4 degrees 1 37 degrees 0 60 degrees 0 E9D20 What is the beamwidth of a symmetrical pattern antenna with a gain of 15 dB as compared to an isotropic radiator? 0 72 degrees 0 52 degrees 0 36 degrees 1 3.6 degrees 0 E9D21 What is the beamwidth of a symmetrical pattern antenna with a gain of 12 dB as compared to an isotropic radiator? 0 34 degrees 0 45 degrees 0 58 degrees 0 51 degrees 1 E9E01 What system matches a high-impedance transmission line to a lower impedance antenna by connecting the line to the driven element in two places, spaced a fraction of a wavelength each side of element center? 0 The gamma matching system 0 The delta matching system 1 The omega matching system 0 The stub matching system 0 E9E02 What system matches an unbalanced feed line to an antenna by feeding the driven element both at the center of the element and at a fraction of a wavelength to one side of center? 0 The gamma matching system 1 The delta matching system 0 The omega matching system 0 The stub matching system 0 E9E03 What impedance matching system uses a short perpendicular section of transmission line connected to the feed line near the antenna? 0 The gamma matching system 0 The delta matching system 0 The omega matching system 0 The stub matching system 1 E9E04 What should be the approximate capacitance of the resonating capacitor in a gamma matching circuit on a Yagi beam antenna for the 20-meter band? 0 14 pF 0 140 pF 1 1400 pF 0 0.14 pF 0 E9E05 What should be the approximate capacitance of the resonating capacitor in a gamma matching circuit on a Yagi beam antenna for the 10-meter band? 0 0.2 pF 0 0.7 pF 0 700 pF 0 70 pF 1 E9E06 What is the velocity factor of a transmission line? 0 The ratio of the characteristic impedance of the line to the terminating impedance 0 The index of shielding for coaxial cable 0 The velocity of the wave on the transmission line multiplied by the velocity of light in a vacuum 0 The velocity of the wave on the transmission line divided by the velocity of light in a vacuum 1 E9E07 What determines the velocity factor in a transmission line? 0 The termination impedance 0 The line length 0 Dielectrics in the line 1 The center conductor resistivity 0 E9E08 Why is the physical length of a coaxial cable transmission line shorter than its electrical length? 0 Skin effect is less pronounced in the coaxial cable 0 The characteristic impedance is higher in a parallel feed line 0 The surge impedance is higher in a parallel feed line 0 RF energy moves slower along the coaxial cable 1 E9E09 What is the typical velocity factor for a coaxial cable with polyethylene dielectric? 0 2.70 0 0.66 1 0.30 0 0.10 0 E9E10 What would be the physical length of a typical coaxial transmission line that is electrically one-quarter wavelength long at 14.1 MHz? (Assume a velocity factor of 0.66.) 0 20 meters 0 2.3 meters 0 3.5 meters 1 0.2 meters 0 E9E11 What is the physical length of a parallel conductor feed line that is electrically one-half wavelength long at 14.10 MHz? (Assume a velocity factor of 0.95.) 0 15 meters 0 20 meters 0 10 meters 1 71 meters 0 E9E12 What parameter best describes the interactions at the load end of a mismatched transmission line? 0 Characteristic impedance 0 Reflection coefficient 1 Velocity factor 0 Dielectric Constant 0 E9E13 Which of the following measurements describes a mismatched transmission line? 0 An SWR less than 1:1 0 A reflection coefficient greater than 1 0 A dielectric constant greater than 1 0 An SWR greater than 1:1 1 E9E14 What characteristic will 450-ohm ladder line have at 50 MHz, as compared to 0.195-inch-diameter coaxial cable (such as RG-58)? 0 Lower loss in dB/100 feet 1 Higher SWR 0 Smaller reflection coefficient 0 Lower velocity factor 0 E9E15 What is the term for the ratio of the actual velocity at which a signal travels through a transmission line to the speed of light in a vacuum? 0 Velocity factor 1 Characteristic impedance 0 Surge impedance 0 Standing wave ratio 0 E9E16 What would be the physical length of a typical coaxial transmission line that is electrically one-quarter wavelength long at 7.2 MHz? (Assume a velocity factor of 0.66.) 0 10 meters 0 6.9 meters 1 24 meters 0 50 meters 0 E9E17 What kind of impedance does a 1/8-wavelength transmission line present to a generator when the line is shorted at the far end? 0 A capacitive reactance 0 The same as the characteristic impedance of the line 0 An inductive reactance 1 The same as the input impedance to the final generator stage 0 E9E18 What kind of impedance does a 1/8-wavelength transmission line present to a generator when the line is open at the far end? 0 The same as the characteristic impedance of the line 0 An inductive reactance 0 A capacitive reactance 1 The same as the input impedance of the final generator stage 0 E9E19 What kind of impedance does a 1/4-wavelength transmission line present to a generator when the line is open at the far end? 0 A very high impedance 0 A very low impedance 1 The same as the characteristic impedance of the line 0 The same as the input impedance to the final generator stage 0 E9E20 What kind of impedance does a 1/4-wavelength transmission line present to a generator when the line is shorted at the far end? 0 A very high impedance 1 A very low impedance 0 The same as the characteristic impedance of the transmission line 0 The same as the generator output impedance 0 E9E21 What kind of impedance does a 1/2-wavelength transmission line present to a generator when the line is shorted at the far end? 0 A very high impedance 0 A very low impedance 1 The same as the characteristic impedance of the line 0 The same as the output impedance of the generator 0 E9E22 What kind of impedance does a 1/2-wavelength transmission line present to a generator when the line is open at the far end? 0 A very high impedance 1 A very low impedance 0 The same as the characteristic impedance of the line 0 The same as the output impedance of the generator 0