1. A very low-loss coaxial transmission line has 30 pF/ft of distributed capacitance and 75 nH/ft of inductance. What is its characteristic impedance? - 50 ohms 2. The characteristic impedance of a transmission line does not depend upon its -length 3. What must be the ratio of outer conductor diameter to central conductor diamter, for a 75 ohms. Teflon coaxial transmission line? -6.12 4. What is the voltage reflection coefficient for a 75 ohms line with a terminating imepedance of 50 ohms - -0.2 5.What is the attenuation in nepers for a 1-km length of RG58 A/U coax with a loss of 5 db/100 ft? - 18.88 Np 6. Find the input impedance in ohms, for a 50 ohms lossless transmisiion line, 3.5 long, if the load is 20 + j75 ohms. - 20 + j75ohms 7. A type of transmission line whose conductors experience the same electrical capacitance relative to the ground. - Balanced Line 8. A type of transmission line consising of an inner conductor surrounded by, but insulated from an outer conductor. - coaxial cable 9. Power loss due to increased effective resistance of a conductor at microwave frequencies due to skin effect. - conduction loss 10. The ratio of incident and reflected voltage waves representing transmission and reflection coefficients used to chracterize a linear microwave device. - S Parameter 11. What is a short length of transmission line, shorted at one end and attached at the appropriate distance from the load for the purpose of matching a complex load to the transmission line? - stub 12. The ratio of the maximum to minimum voltage on a transmission line is called - SWR

13. When does a transmission line have ab SWR equal to 1 ? - Zd = Zo 14. When does a transmission line termited in a short look like a short to the source? - at quarter-wavelength 15. When does an open transmission line look like a short to the source? - at quarter-wavelength 16. How many cycles of a 1-MHz wave can a 6-mile transmission line accommodate? -32.26 cycles 17. A transmission line has a capacitance of 25 pF/ ft and an inductance of 0.15 uH/ft. Determine the characteristic impedance of the line. - 77.5 ohms 18. For a transmission line giving a maximum rms voltage reading of 50 V at one point and a maximum rms voltage reading 25 V at another point. What is the VSWR of the line? - 2 19. What would be the SWR of a transmission line if power is being delivered to a 100 ohms load by a line with a chracteristic impedance of 50 ohms? - 2 20. A transmission line consisting of two conductors that have equal resistance per unit length. - Balanced Line 21. Which of the following is not a common transmission line impedance? -120 ohms 22. Name a use for a ciccular waveguide - radar 23. In a waveguide , the TM mode means that the: - magnetic field is perpendicular to the direction of wave propagation 24. The mode at which a waveguide operates is determined by the: - method used to couple the signal into the waveguide 25. In waveguide, the TE mode means that the - electric field is perpendicular to the direction of wave propagation

26. What is the guide wavelength if m = 1 for a 6-cm x 3-cm waveguide with a fequency of 12 GHz? - 2.55 cm 27. A 5-GHz signal to be propagated along a waveguide with a width of 3 cm. What is the largest value of m that can be accommodated by the waveguide? - m=1 28. A type of transmission line where the two conductors carry equal current. - balanced 29. The standing wave ratio is euqal to ____ if the load is properly matched with the transmission. - 1 30. What is the chracteristic impedance of twin lead? - 300 ohms 31. Transmission line must be matched to the load to - transfer maximum power to the load 32. A type of transmission line used in gamma match. - coaxial 33. Would it be possible to produce a 70 ohms twin lead? - yes 34. A flat transmission line delivers 5 kW at 10 A. What is its impedance? - 50 ohms 35. What type of coupling is used between helical resonators? - slot 36. A major and basic advantage for the used of a klystron. - high power 37. What should be the SWR into a dummy antenna? - 1:1 38. How wide must a waveguide be? - over lamda/2 39. What is the name of the microwave transmission line that is used with printed circuits? - microstrip

40. Which of the following is not a method of coupling into or out of a waveguide? - Slot 41. A type of semiconductor bolometer is called - Thermistor 42. Which of the following is not a mocrowave vacuum tube? - Gunn 43. A convenient method of dtermining antenna impedance. - Smith Chart 44. A waveguide acts as a - HPF 45. Characteristic impedance of a transmission line is the impedance measued at the _____ when its length is infinite. - input 46. What is the length in centimeters of a quarter-wave stub, in free space at 4 Ghz - 1.875 cm 47. What quarterwave transformer will match a 100 ohms line to an antenna whose value is 175 ohms? - 132.29 ohms 48. A quarter-wave stub shorted at the end has high impedance: - lamda/4 back from the short 49. Two 2-mm-diameter wires held 6 cm apart center to center has a characteristic impedance of -491 ohms 50. To connect coaxial line to a paraller-wire, _______ is the best to use. -balun 51. What is the impedance of most waveguide? - 50 ohms 52. What is the function of a resistive pyramid or vane at the end of a waveguide section? -dummy load 53. When a transmission line uses ground return, it is called _____ line. - unbalanced

54. What is meant by a voltage node? - voltage minima 55. Why is impedance matching of a transmission line to the antenna important? - for maximum power transfer 56. What is meant by SWR of a transmission line? - Standing Wave Ratio 57. Does minimum or maximum VSWR indicate best matching of antenna to transmission line? - minimum 58. How can SWR be minimized? - using-stubs 59. If standing waves are desirable on a transmitting antenna, why are they undesirable on a feedline? - it increases power loss 60. If two towers of a 1100-khz array are seperated by 120, what is the tower seperation in feet? - 298

61. In a transmission line, if the maximum current to minimum current ratio is 2:1, what is the ratio of the maximum voltage to minimum voltage? - 2:1 62 Skin effect describes the tendency of: -ac conductrors to carry the circuit current on their surface. 63. A wire conductor experiences the following characteristics: - a and b 64. A 50 ohms circuited line is 0.1 in length, at a frquency of 500 MHz. What is its equivalent inductive reactance? - j36.33 ohms 65. A 300 ohms line is terminated in a load impedance of 100 + j200 ohms. What is the reflection coefficient for this line? - 0.632< 108 deg 66. In a transmission line, the characteristic impedance equals

-

67. What is the distance between a voltage maximum and adjacent current maximum on a transmission line with standing waves? - lamda/4 68. For a transmission line terminated with a load equal to its characteristic impedance the reflection coefficient is - 0 69. A matching stub should be placed - nearest to the load 70. The use of stub-matching network eliminates standing waves on - transmittes side of stub 71. What is the input impednce of a shorted lossless line of length lamda/4 - infinity 72. The characteristic impedance will ______, if the spacing between the wires of a balanced transmission line is increased. -increase 73. Transmission lines when connected to antenna have - resistive load at the resonant frequency 74. In a coaxial cable, the characteristic impedance depends on the diameter of - both a and b 75. What is the reflection coefficient if an open-circuited transmission line? - 1 76. One of the following microwave diodes is suitable for very low power oscillator only. - tunnel 78. The reflection coefficient on a transmission line is 1/3, what is the SWR? - 2 79. Indicate the false statement. The SWR on a transmission line is infinity: the line is terminated in a(n) - complex impedance 80. if transmission line is terminated with a resistance equal to its characteristic impedance. - the standing wave ratio will be minimum

81. Coaxial Lines are used on those systems operationg - below 2 GHz 82. The ratio of the largest rms value to the smallest rms value of the standing voltage along a transmission line is called - SWR 83. What is the SWR along a transmission line having a characteristic impedance of 75 ohms and a load impedance of 300 ohms? - 4 84. The ____ is a measure of the mismatch between a load and the transmission line. - SWR 85. A waveguide can be considered as a - HPF 86. What is the dominant mode in a rectangular waveguide? - TE 10 87. Which tester is used to measure SWR? - Reflectometer 88. The aspect ratio of a standard rectangular waveguide is - 2:1 89. Referred to the dielectric constant of a transmissio ine material. - Velocity factor 90. Referred to as a ferrite device that can be used in lieu of a duplexer to isolate a microwave transmitter and receiver when both are connected to the same antenna. - Circulator 91. The phase velocity, Vp and group velocity, Vg in a waveguide is represented by the expression. - C= (VpVg)^1/2 92. A transmission line capable of handling high-powered signal is -waveguide 93. Determine the dB gain of a receiving antenna which delivers a microvolt signal to a tansmission line over that of an antenna that delivers a 2 microvolt signal under identical circumstances. - 6 db

94. The cut-off frequency in a waveguide signifies - longer wave will not propagate signifiacantly 95. The transmission line parameter that represents the decrease in the signal strength is - attenuation constant 96. The graphical solution of transmission line problems involve the use of - Smith Chart 97. Who developed the Smith Chart? - Philip H. Smith 98. A 50 lossless transmission line is terminated with a load impedance of 25 + j75. What is the input impedance at a distance of 0.5 from the load? - 25 + j75 ohms 99. Transmission lines are either balanced or unbalanced with respect to - ground 100. What is the velocity factor of non-foam 50 or 75 ohm flexible coaxial cable such as RG 8, 11, 58 and 59? -0.66 101. A shorted transmission line less than lamda/4 in length will exhibit _____ reactance. - inductive 102. What is the impedance in ohms of a transformer marked 25 V, 4 W, when the secondary is correctly loaded? - 156 ohms 103. An open circuited line greater than lamda/4 but less than lamda/2 in length will exhibit _____ reactance. - inductive 104. What is the longest waelength that a 2.5 cm wide waveguide will support in the dominant mode - 5 cm 105. What determines the velocity factor in transmission line? - dielectrics in the line 106. What physical length corresponds to 0.25 lamda at 500 MHz for cable with a propagation velocity of 0.68C? -0.102 m

107. What is the SWR for a 100 omhs characteristic line and a 300 ohms load? - 3 108. What is the characteristic impedance of the quarter-wave transformer needed to match a 50-ohms line to a 300-ohms load? - 122 ohms 109. For a coplex impedance z=150 j50 ohms with Zo of 50 ohms, what is the normalized value of Z? - 3 j1 110. A single conductor running from the transmitter to the antenna. - Single line wire 111. What is the effect of standing waves on a transmission line? - decrease in the power fed to antenna 112. Best choice of transmission line component to couple a coaxial line to a parallel wire line. - Balun 113. What is the main frequency determining element of a klystron? - resonant cavity 114. Energy that has neither been radiated into space nor completely transmitted. - Standing waves 115. To couple a coaxial line to parallel line, it is better to use a - balun 116. An electronic equipment used to measure standing wave ratio. - Reflectometer 117. What is the meaning of the term velocity factor of a transmission line? - the velocity of the waves on the transmission line divided by the velocity of light in a vacuum 118. Which of the following determine the characteristics of a transmission line? -Physical dimensions 119. For an ideal transmission line, the best possible conductor to use is - Silver 120. A flat line is also called _____ because it is terminated in its characteristic impedance - Non-resonant

121. What is the phase shift corresponding to lamda/4 in standing wave pattern? - 90 deg 122. For a parallel- resonant circuit, a lamda/4 stub must be at the ends - shorted 123. What is the cutoff wavelength of a 6-cm x 3-cm wave guide? -12 cm 124. Distance traveled by a wave in the time of one cycle. - Wavelength 125. Termination means - load connected to the output edn of a transmission line PART VI: WAVE PROPAGATION AND ANTENNA

1. What is the resistance of a lossless Hertz antenna in free space? 73 ohms

2. A form of unwanted radiation working against the main beam caused by

feeding a parabolic reflector with an isotropic source. Backlobe Radiation

3. The angle measured between the 3 dB down points on the major lobe of an

antennas radiation pattern. Beamwidth

4. It is an array of simple dipoles fed in phase and having a radiation pattern

whose maximum directivity is along the axis normal to the plane of the array.

Broadside Array

5. A type of microwave antenna in which the feed-point is located at the vertex

of the parabola and is directed against a secondary hyperbolic reflector.

Cassegrain Antenna

6. A microwave antenna formed from a circular waveguide. Conical Horn

Antenna

7. What is the bridge circuit used in conjunction with a turnstile antenna for the

purpose of feeding two separate signals to a single antenna? Diplexer

8. A type of antenna array consisting of a linear arrangement of simple dipoles

fed 90 degrees out of phase and having a radiation pattern of maximum

directivity in the plane of the array. End-Fire Array

9. Used to measure the absolute signal strength defined as the voltage induced

in a one-meter antenna by a radiated TEM wave. Field Strength

10. A type of antenna capable of transmitting (receiving) a TEM wave polarized

in any direction. Helical Antenna

11. What is the electromagnetic field that surrounds an antenna but does not

radiate? Induction Field

12. It is a non-resonant antenna several wavelengths long, but not cut to any

particular wavelength. Long-Wire Antenna

13. The region within the influence of the induction field of an antenna. Near

Field

14. A measure of the distribution of radiated power over a given area is called

____. Power Density

15. Any finite, usually small, local area of a spherical wavefront is called ____.

Plane Wave

16. What is the orientation of the electric field of an antenna relative to the

earths surface and antenna structure? Polarization

17. What makes an antenna physically long but electrically short? Adding C in

series

18. A type of antenna whose resonant properties cause standing waves to exist

along the antenna elements. Resonant Antenna

19. It is a condition of excessive illumination caused by feeding a parabolic

reflector with an omnidirectional source. Spillover

20. Is an example of a parasitic array. Yagi-Uda

21. The structure made of plastic-like material used to enclose the complete

antenna assembly to protect the antenna from the weather and to reduce

wind or snow loading. Radome

22. A short horizontal section to the top of a Marconi antenna to add inductance,

thereby increasing its effective length. Top Loading

23. A type of dielectric lens shape used to reduce excess weight and attenuation

is called Zoned Lens

24. What is a dummy load? Simulates the transmitting antenna but doesnt

transmit any signal

25. It is the ratio of the antenna transmitting frequency to its bandwidth. Q

26. For an antenna with a radiation resistance of 50 ohms, how much power will

be radiated if the antenna current is 50 A? 125Kw

27. Determine the Q of an antenna with the bandwidth of 0.5 MHz that is cut to a

frequency of 20 MHz. 40

28. What should be the height of a Marconi antenna to transmit a 200 MHz

signal? Note: Use 95% rule 0.35625 m

29. What is the dB gain of an antenna that delivers a 100 microvolts signal over

that of an antenna that delivers 75 microvolts. 2.5 dB

30. What is meant by antenna gain? The numeric ratio relating the radiated

signal strength of an antenna to that of another antenna

31. To install an antenna with a line-of-sight transmission at a distance of 75

miles, determine the height of a receiving antenna if the transmitting antenna

is 250 ft. 1,385 ft.

32. Which radiowave is primarily transmitted along the surface of the earth?

Ground Wave

33. The major mode of propagation for antenna that are line of sight starts at

about what frequency? 30 MHz

34. A dipole antenna requires to be feed with 20 kW of power to produce a given

signal strength to a particular distant point. If the addition of a reflector

makes the same field strength with an input power if 11 kW. What is the gain

in dB obtain by the use of the reflector? 2.6

35. Which ionospheric layer is present at night? F

36. A ____ antenna is essentially an extension of the end of a waveguide. Horn

37. The antenna used at microwave frequencies to focus its wave is a(n) ____

antenna. Parabolic

38. What is another term used for dummy antenna? Phantom

39. At height about 180 km above the earth exist only during daylight. F1 Layer

40. Radiation characteristics of a dipole. Bidirectional

41. Determine the gain of a 6-ft. parabolic dish operating at 1800 MHz. 28.17 dB

42. An electromagnetic wave is ____ polarized when the electric field lies wholly

in one plane containing the direction of propagation. Linearly

43. The electrical field lies in a plane parallel to the earths surface. Horizontal

Polarization

44. The product of the power supplied to the antenna and its gain relative to a

half-wave dipole in a given direction. ERP

45. Width measured in degrees of a major lobe between end of the lobe at which

the relative power is one half (-3db) its value from the peak of the lobe.

Beamwidth

46. What is the relation in degrees if the electrostatic and electromagnetic fields

of an antenna? 90 degrees

47. Type of antenna which is normally used for satellite tracking service. Helical

48. What is meant by the term radiation resistance for an antenna? An

equipment resistance that would dissipate the same amount of power

as that radiated from an antenna

49. What happens to the wave velocity as it passes from air to ionosphere?

Increases

50. What wave is the same day or night? Ground wave

51. Scatter transmission Is used at what frequencies? VHF and UHF

52. What polarization is employed in AM broadcasting? Vertical

53. What is the length in feet of an antenna wire for a 4 MHz if the antenna is

3lambda/2 in length? 363 ft.

54. When waves bend away from straight lines of travel, it is called ____

Refraction

55. Highest frequency that can be used for skywave HF communications between

two given points on earth. Maximum Usable Frequency

56. Electromagnetic radiation theory was profounded by ____. James Clark

Maxwell

57. What is the thickest layer of the ionosphere? F2

58. Which region of the ionosphere is mainly responsible for long distance night

time communications? F Layer

59. The polarization of a discone antenna is ____. Vertical

60. ____ is the horizontal pointing angle of an antenna. Azimuth

61. Which is properly terminated antenna? Rhombic

62. How much does the radiated power of an antenna increases if its current

increased by 3.3. 10.89 times

63. When testing transmitter to prevent interfering with other stations, which

type of antenna must be used? Dummy Antenna

64. A device that radiates electromagnetic energy and/or intercepts

electromagnetic radiation. Antenna

65. The frequency of operation of a dipole antenna cut to length of 3.4 m. 42.9

MHz

66. What is the name of antennas that are grounded at one end? Marconi

67. An increase in the effective power radiated by an antenna in a certain desired

direction at the expense of power radiated in other directions. Antenna Gain

68. Where are the maximum voltage points on a half-wavelength antenna? Ends

69. What is the theoretical radiation resistance of a horizontal lambda/2 dipole a

lambda/2 high? 73 ohms

70. Which reactance would a dipole have if it is 0.6lambda long? Inductive

71. How is capacitive reactance compensated in an antenna? Add series

inductance

72. What is the advantage of drooping ground planes? Higher center

impedance

73. Why are small balls attached to whip antennas? To prevent corona

discharge

74. What are beams called if all elements are in line? Colinear

75. What is the phase separation of two antennas 3lambda/8 apart? 135

degrees

76. Which of the following gives more forward gain? Director

77. How much more feed-point impedance does a folded dipole have than a

normal dipole? Four times

78. With similar size, which of the following has the greatest gain? Parabolic

79. In what direction is the null of a small diameter loop in relation to the plane

of the loop? Right Angles

80. In what unit is field intensity measured? mV/m

81. When speaking of antennas, what is a bay? A section which would be a

complete antenna by itself

82. A method used in determining the feed-point impedance of a vertical

antenna. Impedance Bridge

83. What feed requirements must be met to produce a circular radiation pattern

when using two crossed dipoles? Feed 90 degrees apart electrically

84. What is the free space loss, in dB, between two microwave parabolic

antennas 38.9 kilometer apart operating at 7.0 GHz? 140.98 dB

85. Electromagnetic waves travel at ____ in free space. 300,000 km/sec

86. When electromagnetic waves are propagated through a waveguide, they Are

reflected from the walls but do not travel along them

87. How many receiving antenna(s) are used with frequency diversity? 1

88. An antenna ____ is a metal structure that substitute for earth ground.

Counterpoise

89. A horizontal antenna provides a radio wave with ____ polarization.

Horizontal

90. An antenna loading coils is a series inductance used to make the antenna

electrically ____. Longer

91. ____ elements are antenna conductors not directly connected to the

transmission line. Parasitic

92. Radio waves are propagated by ____ through the ionosphere. Sky Waves

93. A horizontal antenna is Horizontally Polarized

94. How often does sunspot (short term) activity repeat? 27 Days

95. Why is a half-wavelength antenna always shorter that that computed by

lambda = v/f? End Effects

96. What antenna placement and feed produces a cardioid radiation pattern? 45

degrees apart and fed at 90 degrees

97. What is an inverted V antenna? Drooping Dipole

98. How must elements of a turnstile antenna be fed? 90 degrees out of phase

99. What is a disadvantage when using round rather than rectangular

waveguide? Polarization may rotate

100. Within what tolerance must antenna currents be held in directive

systems? 5%

101. What must be added between a 50 ohms coaxial line and the base of a

center-loaded vertical whip? L-pad

102. What produces residual signal in a loop antenna? Sky waves

103. EIRP stands for Effective Isotropic Radiated Power

104. What are the two fields that radiate from any antenna? Electric and

Magnetic

105. An antenna that is circularly polarized is the Helical

106. What is meant by radio-path horizon? 4/3 of the optical horizon

107. What are electromagnetic waves? A wave consisting of an electric

field and a magnetic field at right angles to each other.

108. What antenna has omnidirectional characteristics? Discone

109. What is meant by a driven element of an array? Directly connected

to the transmitter

110. A 500-kHz transmitter produces a field strength of 100 microvolts per

meter at 100 mi. What is the theoretical strength at 200 mi? 50 microvolts

per meter

111. Best description of a collinear and broadside antenna radiation

pattern. Bidirectional

112. A field of 25 mV/m develops 2V in a certain antenna. What is its

effective height? 80 m

113. What is an isotropic radiator? All of the above

114. The lowest layer in the ionosphere. D

115. What is the ERP if the output of a transmitter is 50 kW, the coax line

loss is 300 W, and antenna power gain is 3 dB? 99.4kW

116. When the transmitting and receiving antennas are in line-of-sight

with each other, the mode of propagation is ____ wave. Space or direct

117. The frequency normally used for ionospheric transmission is known

as ____. Optimum Working Frequency

118. The virtual height of an ionospheric layer is ____ as the height a wave

actually penetrates. More

119. The number of lobes on each side of a 4lambda resonant antenna is 8

120. Whereas resonant antenna is bidirectional, non-resonant antenna is

Unidirectional

121. A parasitic element of an array is one which Is not connected to the

transmitter output

122. What is the radiation resistance of a half-wave folded dipole? 292

ohms

123. Where does the maximum current and minimum voltage values on a

resonant Hertz dipole exist? Center of the antenna

124. What is meant by the term antenna efficiency? Efficiency = radiation

resistance / total resistance x 100%

125. Which of the following is not true about an end-fire array? It has a

dipole spacing of lambda

126. The ____ in a Yagi antenna is longer than the radiating element.

Reflector

127. Lens antenna used for microwaves are usually made of Polystyrene

128. A parabolic antenna is commonly used at 3000 MHz

129. Gain of an isotropic antenna 0 dB

130. What is an application of loop antenna? Direction Finding

131. The polarization of a helical antenna is ____ Circular

132. Which of the following is a low gain but omnidirectional antenna?

Discone

133. Which is not a wide-band antenna? Marconi

134. The use of top-loading is to Increase its effective height

135. The main advantage of dielectric lens antennas over a parabolic

reflector is that they ____ Have no primary antenna mount to obstruct

radiation

136. Which is not a characteristic of a discone antenna? Unidirectional

137. Production of radiation by a radio transmitting station. Emission

138. What is the impedance of free space? 377 ohms

139. Any small element of space in the path of a wave may be considered as

a source of secondary wavelet. Huygens Principle

140. The electric field intensity of a dipole at a remote point varies as 1/r

141. An electromagnetic wave consists of Both electric and magnetic

field

142. _____ is the upper portion of the earths atmosphere, which absorbs

large quantities of suns radiation. Ionosphere

143. Which layer of the ionosphere mostly reflects the high-frequency

radiowaves? F2

144. The radio horizon for space waves is about ____ as far as the optical

horizon. 4/3

145. What is the gain of four identically polarized antennas stacked one

above the other and fed in phase? 6 dB over the gain of one antenna

146. Virtual height of an ionospheric layer is always ____ its actual height.

Greater than

147. Radio wave concentration in the direction of the signal emitted by a

directional antenna. Major lobe radiation

148. ____ waves can propagate on piezoelectric substrates. Surface

149. Refers to a type of beam antenna which uses two or more straight

elements arranged in line with each other. Yagi Antenna

150. Anomalous propagation of radiowaves is caused by Metereological

Factors

151. The skip distance is the ____ distance up to which ionospheric

reflection is possible. Minimum

152. A V-antenna is a ____ antenna. Non-resonant

153. What is the power gain of a half-wave dipole with respect to an

isotropic radiator? 2.15 dB

154. In a turnstile antenna, the crossed dipoles are excited with voltages

90 degrees out of phase with each other

155. The approximate impedance of a half-wave folded dipole antenna is

300

156. During night time, the D-layer in the ionosphere Disappears

157. The beamwidth angle of a parabolic dish antenna ____ the dish

diameter. Decreases with increase in

158. Tropospheric scatter may be used in what frequency range? UHF

159. A helical antenna is used for satellite tracking because of ____. Circular

Polarization

160. VHF radio signals are propagated Through the troposphere

161. The type of wave propagation in the UHF band Space Wave

162. A folded-dipole has ____ bandwidth than a single-dipole arrangement.

Greater

163. The lowest resistance grounding on earth. Surface loam soil

164. Tropospheric scatter uses the frequencies in the ____ band. UHF

165. The relative permittivity of air is much ____ that of empty space.

Greater than

166. The critical frequency is ____ the maximum usable frequency. Lower

than

167. The advantage of using cassegrain feed in a parabolic reflector is It

allows the feed to be placed at a convenient point

168. Top loading is used in an antenna to increase its ____ Effective height

169. Which of the following is not true abour parabolic reflector?

Omnidirectional Antenna

170. Which of the following has circular polarization? Helical

171. The atmospheric absorption of radiowaves depend on Their

frequency

172. Signals in the UHF range propagate by means of ____ waves. Space

173. When microwave signals follow the curvature of the earth, this is

known as Ducting

174. Antenna side lobes causes Reduction in gain of antenna

175. To increase antenna efficiency, the ____ must be increased. Radiation

resistance

176. For an earths station transmitter with an output power of 40 dB, a

back-off loss of 13 dB, a total branching and feeder loss of 13 dB, and a

transmit antenna gain of 40 dB, determine the EIRP. 54 dBw

177. It is the ability of an antenna to transmit and receive in a specific

direction while discriminating against transmission or reception from all

other directions. Directivity

178. A transmitting antenna is on a 50-ft. tower and the receiving antenna

is on an identical tower. How far apart is the potential distance between

them? 20 mi

179. It consists of a number of dipoles of equal size, equally spaced along a

straight line with all dipoles fed in the same phase from the same source.

Broadside array

180. A type of array antenna which consists of one half-wave driven dipole,

one reflector and one director Yagi-uda

181. What is the FSL in dB at 300 MHz between the earth station and a

satellite at 37,000 km? 173.4 dB

182. An antenna which is not resonant at particular frequencies and so can

be used over a wide band of frequencies is called ____. Periodic

183. ____ occurs when the microwave beam is at point of gazing over an

obstacle. Diffraction

184. What is the term for the ratio of the radiation resistance of an antenna

to the total resistance of the antenna system? Antenna efficiency

185. What is the length of the director in a three-element Yagi for 100-MHz

operation using a 0.2lambda interelement spacing? 1.425 m

186. What is the gain of a dish antenna with D = 2lambda? 33.8 dB

187. It is the bending of radiowaves as they pass over the upper edge of a

hill or mountain. Knife-edge diffraction

188. ____ of a directional antenna patter are those in which radiation is

maximum. Major lobes

189. In a half-wave antenna, the center impedance is equal to ____. 73 ohms

190. Theoretical gain of a Hertzian dipole. 1.76 dB

191. What will happen if a sky wave meets a ground wave at a receiver and

they are appreciably out of phase? Fading

192. Antenna which is not properly terminated Resonant

193. What is the ability of an antenna to concentrate radiated energy in a

desired direction? Directivity

194. It is a measure of the microwave power radiated from an antenna as a

function of angular direction from the antenna axis. Beamwidth

195. What is the driven element of an antenna? The element fed by the

transmission line

196. What do you mean by the outward flow of an energy from any source

in the form of radio waves? Radiation

197. Which of the following is an example of a travelling wave antenna?

Rhombic

198. What is the unit of magnetic field strength? Ampere/meter

199. An antenna structure consisting of three end-fed lambda/2 dipoles

coupled in series. Franklin Antenna

200. The electric field lies in a plane perpendicular to the earths surface.

Vertical Polarization

201. A type of antenna designed to receive or radiate electromagnetic

waves with orthogonal polarizations. Dual Polarized Antenna

202. Radiation pattern of a discone. Omnidirectional

203. Unity gain antenna Isotropic

204. It is an array of metallic conductors buried beneath the antenna,

which is used to improve the conductivity of the natural earth. Earth Mat

205. Which is the non-resonant antenna? Rhombic Antenna

206. It is described as the MUF factor. Sec theta

207. Known as the technique for adding a series inductor at or near the

center of an antenna element in order to cancel the capacitive reactance of an

antenna. Loading coil

208. What is meant by the term antenna bandwidth? The frequency

range over which an antenna can be expected to perform well

209. Where does the voltage node of a half-wave antenna exists? At center

210. ____ is a major cause if the sporadic-E condition. Sunspot

211. Ground waves will propagate best over ____. Saltwater

212. At the ends of a half-wave antenna, what values of current and voltage

exist compared to the remainder of the antenna? Maximum voltage and

minimum current

213. What is meant by referring to electromagnetic waves as horizontally

polarized? The electric field is parallel to the earth

214. A dipole antenna is used to receive a horizontally polarized

transmission. What should be the antenna orientation for maximum

reception? Horizontal

215. Calculate the exact length of a typical dipole antenna to receive a 108-

MHz FM transmission. 1.32 m

216. The standard reference antenna for the directive gain is ____. Isotropic

Antenna

217. If a receiver could use an ideal isotropic antenna, it could receive -40

dBm. How much could be received if an ideal half-wave dipole were used?

164 nW

218. In what region of the world is sporadic-E most prevalent? The

equatorial regions

219. The input current to a well-designed Marconi is 10 Arms. Determine

the input power. 3.7 kW

220. The 3dB beamwidth of a 70% efficient microwave dish antenna is 0.1

degrees at 4 GHz. Compute the gain in dB. 65.3 dB

221. How high must a receiving antenna be to receive a signal directly from

an over-the-horizon transmitter whose antenna is 30 ft. high? The distance

between antennas is 15 mi. 26.3 ft

222. What layer of the ionosphere occurs only during daytime? D

223. The reflector and director of an antenna array are considered as

Parasitic Elements

224. What type of HF antennas are usually used on small vessels? Base-

loaded

225. What is the minimum recommended distance for antenna separation

in a 2-GHz space-diversity receiving system? 0.9 m