QUESTION ANSWER KENNEDY

1. In a communication system, noise is most likely to effect the

signal.

Ans – In the channel

2. Indicate the false statement. Fourier analysis shows that a

sawtooth wave consists of.

Ans – A fundamental sine wave and an infinite number of

harmonics

3. Indicate the false statement. Modulation is used to.

Ans – Reduce the bandwidth used.

4. One of the following types of noise becomes of great importance at

high frequencies. It is the.

Ans – Transit-time noise

5. Indicate the false statement.

Ans – Impulse noise voltage is independent of bandwidth.

6. The value of a resistor creating thermal noise is doubled. The

noise power generated is therefore.

Ans – Unchanged

7. One of the following is not a useful quantity for comparing the

noise performance of receivers.

Ans – Input noise voltage

8. Indicate the noise whose source is in a category different from that

of the other three.

Ans – Atmospheric noise

9. Indicate the false statement. The square of the thermal noise

voltage generated by a resistor is proportional to.

Ans – Its temperature

10. If the plate supply voltage for a plate-modulated class C amplifier
is V. the maximum plate-cathode voltage could be almost as high as.

Ans – 4V

11. In a low level AM system amplifiers following the modulated stage

must be.

Ans – Linear devices

12. If the carrier of a 100 percent modulated AM wave is suppressed.

The percentage power saving will be.

Ans – 66.66

13. Leak type bias is used in a plate modulated class C amplifier to.

Ans – Prevent excessive grid current

14. The output stage of a television transmitter is most likely to be a

Ans – Grid modulated class C amplifier

15. The modulation index of an AM wave is changed from 0 to 1. The

transmitted power is.

Ans – Increased by 50 percent

16. One of the advantages of base modulation over collector

modulation of a transistor class C amplifier is.

Ans – The lower modulating power required

17. A carrier is simultaneously modulated by two sine waves with

modulation indices of 0.3 and 0.4, the total modulation index.

Ans – 0.5

18. Amplitude modulation is used for broadcasting because.

Ans – Its use avoids receiver complexity

19. Indicate the false statement regarding the advantages of SSB over
double sideband, full carrier AM.
Ans – Transmitter circuits must be stable, giving better reception

20. When the modulation index of an AM wave is doubled, the

antenna current is also doubled. The AM system being used is.

Ans – Single-sideband, suppressed carrier (J3E)

21. Indicate which one of the following advantages of the phase

cancellation method of obtaining SSB over the filter method is false:

Ans – There are more balanced modulators: therefore the carrier is

suppressed better.

22. The most commonly used filters in SSB generation are

Ans – Mechanical

23. In an SSB transmitter, one is most likely to find a

Ans – Class B RF amplifier

24. Indicate in which one of the following only one sideband is

transmitted:

Ans – H3E

25. One of the following cannot be used to remove the unwanted

sideband in SSB. This is the.

Ans – Balanced modulator

26. R3E modulation is sometimes used to.

Ans – Simplify the frequency stability problem in reception

27. To provide two or more voice circuits with the same carrier. It is
necessary to use.

Ans – ISB

28. Vestigial sideband modulation (C3F) is normally used for.

Ans – HF point-to-point communications

29. In the stabilized reactance modulator AFC system

Ans – The discriminator frequency must not be too low, or the

system will fail

30. In the spectrum of a frequency-modulated wave.

Ans – The amplitude of any sideband depends on the modulation

index

31. The difference between phase and frequency modulation.

Ans – Lies in the different definitions of the modulation index.

32. Indicate the false statement regarding the Armstrong modulation

system.

Ans – Equalization is unnecessary

33. An FM signal with a modulation index Mf is passed through a

frequency tripler. The wave in the output of the tripler will have a
modulation index of.

Ans – 3mf
34. An FM signal with a deviation ∂ is passed through a mixer, and has
its frequency reduced fivefold. The deviation in the output of the mixer is

Ans – ∂

35. A pre-emphasis circuit provides extra noise immunity by

Ans – Amplifying the higher audio frequencies

36. Since noise phase modulates the FM wave. As the noise sideband
frequency approaches the carrier frequency, the noise amplitude

Ans – Is decreased

37. When the modulating frequency is doubled, the modulation index

is halved, and the modulating voltage remains constant. The modulation
system is

Ans – Frequency modulation

38. Indicate which one of the following is not an advantage of FM over
AM.

Ans – Lower bandwidth is required

39. One of the following is an indirect way of generating FM. This is

the.

Ans – Armstrong modulator

40. In an FM stereo multiplex transmission, the

Ans – Difference signal modulates the 38 Khz subcarrier

41. Indicate which of the following statements about the advantages of

the phase discriminator over the slope detector is false.

Ans – Greater limiting

42. Show which of the following statements about the amplitude limiter
is untrue.

Ans – The circuit is always biased in class C, by virtue of the leak-

type bias

43. In a radio receiver with simple AGC

Ans – an increase in signal strength produces more AGC

44. In a broadcast superheterodyne receiver, the

Ans – Mixer input must be tuned to the signal frequency

45. To prevent overloading of the lasts IF amplifier in a receiver, one

should use

Ans – Variable sensitivity

46. A superheterodyne receiver with an IF of 450khz is tuned to a

signal at 1200Khz. The image frequency is.

Ans – 2100 Khz

47. In a ratio detector

Ans – The linearity is worse than in a phase discriminator

48. The typical squelch circuit

Ans – Cuts off an audio amplifier when the carrier is absent.

49. Indicate the false statement in connection with communications

receivers.

Ans – Variable sensitivity is used to eliminate selective fading.

50. The controlled oscillator synthesizer is sometimes preferred to the

direct one because.

Ans – It is relatively free of spurious frequencies

51. The frequency generated by each decade in a direct frequency

synthesizer is much higher than the frequency shown : This is done to

Ans – Reduce the spurious frequency problem

52. Indicate which of the following circuits could not demodulate SSB

Ans – Phase discriminator

53. If an FET is used as the first AF amplifier in a transistor receiver,

this will have the effect of.

Ans – Reducing the effect of negative-peak clipping

54. Indicate the false statement the superheterodyne receiver replaced

the TRF receiver because the latter suffered from.

Ans – Insufficient gain and sensitivity

55. The image frequency of a superheterodyne receiver.

Ans – Is not rejected by the IF tuned circuits

56. One of the main functions of the RF amplifier in a superheterodyne

receiver is to.

Ans – Improve the rejection of the image frequency

57. A receiver has poor IF selectivity. It will therefore also have poor

Ans – Blocking
58. Three point tracking is achieved with

Ans – The padder capacitor

59. The local oscillator of a broadcast receiver is tuned to a frequency

higher than the incoming frequency.

Ans – To allow adequate frequency coverage without switching

60. If the intermediate frequency is very high (Indicate false statement)

Ans – Tracking will be improved

61. A low ratio of the ac to the dc load impedance of a diode detector

results in.

Ans – Negative-peak clipping.

62. One of the following cannot be used to demodulate SSB.

Ans – Bipolar transistor balanced modulator

63. Indicate the false statement. Noting that no carrier is transmitted

with J3E, we see that.

Ans – Adjacent-channel rejection is more difficult

64. When a receiver has a good blocking performance, this means

that.

Ans – It is unaffected by AGC derived from nearby transmissions

65. An AM receiver uses a diode detector for demodulation. This

enables it satisfactory to receive.

Ans – Single side band, full carrier

66. Indicate the false statement. The SWR on a transmission line is

infinity, the line is terminated in.

Ans – A complex impedance

67. A (75 – j50) Ω load is connected to a coaxial transmission line of Z 0
= 75 Ω at 10 Ghz. The best method of matching consists in connecting.

Ans – A short circuited stub at some specific distance from the

load.

68. The velocity of a transmission line

Ans – Depends on the dielectric constant of the material used

69. Impedance inversion may be obtained with

Ans – A quarter wave line

70. Short-circuited stubs are preferred to open-circuited stubs because

the latter are.

Ans – Liable to radiate

71. For transmission-line load matching over a range of frequencies, it

is best to use a.

Ans – Double stub

72. The main disadvantage of the two-hole directional coupler is

Ans – Narrow bandwidth

73. To couple a coaxial line to a parallel wire line, it is best to use a.

Ans – Balun

74. Indicate which one of the following terms applies to troposcatter

propagation.

Ans – Fading

75. VLF waves are used for some types of services because.

Ans – They are very reliable

76. Indicate which of the following frequencies cannot be used for

reliable beyond the horizon terrestrial communications without repeaters.

Ans – 12 Ghz

77. High frequency waves are

Ans – Affected by the solar cycle

78. Distances near the skip distance should be used for sky wave
propagation

Ans – To prevent sky-wave and upper ray interference

79. A ship-to-ship communications system is plagued by fading. The

best solution seems to be the use of

Ans – Frequency diversity

80. A range of microwave frequencies more easily passed by the

atmosphere than are the others is called a

Ans – Window

81. Frequencies in the UHF range normally propagate by means of

Ans – Space waves

82. Tropospheric scatter is used with frequencies in the following

range

Ans – UHF

83. The ground wave eventually disappears, as one moves away from
the transmitter, because of

Ans – Tilting

84. In electromagnetic waves, polarization

Ans – Is due to the tranverse nature of the waves

85. As electromagnetic waves travel in free space, only one of the

following can happen to them.

Ans - Attenuation

86. The absorption of radio waves by the atmosphere depends on.

Ans – Their frequency

87. Electromagnetic waves are refracted when they.

Ans – Pass into a medium of different dielectric constant

88. Diffraction of electromagnetic waves

Ans – May occur around the edge of a sharp obstacle

89. When microwave signals follow the curvature of the earth, this is
known as.

Ans – Ducting

90. Helical antennas are often used for satellite tracking at VHF
because of.

Ans – The faraday effect

91. An ungrounded antenna near the ground

Ans – Acts as an antenna array

92. One of the following consists of nonresonant antennas

Ans – The rhombic antenna

93. One of the following is very useful as a multiband HF receiving

antenna. This is the :

Ans – Log-periodic

94. Which of the following antennas is best excited from a waveguide.

Ans – Horn

95. Indicate which of the following reasons for using a counterpoise

with antennas is false.

Ans – Protection of personnel working underneath

96. One of the following is not a reason for the use of an antenna
coupler.

Ans – To prevent re-radiation of the local oscillator

97. Indicate the antenna that is not wideband

Ans – Marconi

98. Indicate which one of the following reasons for the use of an earth
mat with antennas is false:

Ans – Protection of personnel working underneath

99. Which one of the following terms does not apply to the Yagi-Uda
array.

Ans – High gain

100. An antenna that is circularly polarized is the.

Ans – Helical

101. The standard reference antenna for the directive gain is the

Ans – Isotropic antenna

102. Top loading is sometimes used with an antenna in order to

increase its.

Ans – Effective length

103. Cassegrain feed is used with a parabolic reflector to.

Ans – Allow the feed to be placed at a convenient point

104. Zoning is used with a dielectric antenna in order to

Ans – Reduce the bulk of the lens

105. A Helical antenna is used for satellite tracking because of its

Ans – Circular polarization

106. The discone antenna is

Ans – Useful as a UHF receiving antenna

107. One of the following is not an omni directional antenna

Ans – Log-periodic
108. When electromagnetic waves are propagated in a waveguide

Ans – They are reflected from the walls but do not travel along
them

109. Waveguides are used mainly for microwave signals because

Ans – They would be too bulky at lower frequencies

110. The wavelength of a wave in a waveguide

Ans – Is greater than in free space

111. The main difference between the operation of transmission lines

and waveguides is that.

Ans – Transmission lines use the principal mode of propagation,

and therefore do not suffer from low frequency cutoff

112. Compared with equivalent transmission lines, 3Ghz waveguides

(Indicate the false statement)

Ans – Are less bulky

113. When a particular mode is excited in a waveguide, there appears

an extra electric component, in the direction of propagation. The
resulting mode is.

Ans – Transverse magnetic

114. When electromagnetic waves are reflected at an angle from a wall,

their wave length along the wall is.

Ans – Greater than in the actual direction of propagation

115. As a result of reflections from a plane conducting wall,

electromagnetic waves acquire an apparent velocity grater than the
velocity of light in space. This is called the.

Ans – Phase velocity

116. Indicate the false statement. When the free space wavelength of a
signal equals the cutoff wavelength of the guide.

Ans – The characteristic impedance of the guide becomes infinite.

117. A signal propagated in a waveguide has a full wave of electric
intensity change between the two further walls. And no component of the
electric field in the direction of propagation. This mode is

Ans – TE2.0

118. The dominant mode of propagation is preferred with rectangular

waveguides because (Indicate false statement)

Ans – The resulting impedance can be matched directly to coaxial

lines.

119. A choke flange may be used to couple two waveguides

Ans – To compensate for discontinuities at the join.

120. In order to couple two generators to a waveguide system without

coupling them to each other, one could not use a

Ans – E- plane T

121. Which one of the following waveguide tuning components is not

easily adjustable.

Ans – Iris

122. A piston attenuator is a

Ans – Waveguide below cutoff

123. Cylindrical cavity resonators are not used with klystrons because
they have

Ans – Harmonically related resonant frequencies

124. A directional coupler with three or more holes is sometimes used

in preference to the two hole coupler

Ans – To increase the bandwidth of the system

125. A ferrite is

Ans – A nonconductor with magnetic properties

126. Manganese ferrite may be used as a (Indicate false answer)

Ans – Garnet
127. The maximum power that may be handled by a ferrite component
is limited by the

Ans – Curie Temperature

128. A PIN diode is

Ans – Suitable for use as a microwave switch

129. A duplexer is used

Ans – To allow the one antenna to be used for reception or

transmission without mutual interference

130. For some applications. Circular waveguides may be preferred to

rectangular ones because of

Ans – Lower attenuation

131. Indicate which of the flowing cannot be followed by the word

“Waveguide”

Ans – Coaxial

132. In order to reduce cross-sectional dimensions, the waveguide to

use is

Ans – Ridged

133. For low attenuation, the best transmission medium is

Ans – Rectangular waveguide

134. A microwave tube amplifier uses an axial magnetic fields and a

radial electric field. This is the

Ans – CFA

135. One of the following is unlikely to be used as a pulsed device. It is

the

Ans – BWO
136. One of the reasons why vacuum tubes eventually fail at microwave
frequencies is that their

Ans – Noise figure increases

137. Indicate the false statement. Transit time in microwave tubes will
be reduced if

Ans – Multiple or coaxial leads are used

138. The multicavity klystron

Ans – Is not a good low-level amplifier because of noise

139. Indicate the false statement. Klystron amplifiers may use

intermediate cavities to

Ans – Prevent the oscillations that occur in two-cavity klystrons

140. The TWT is sometimes preferred to the mulitcavity klystron

amplifier, because the former.

Ans – Has a greater bandwidth

141. The transit time in the repeller space of a reflex klystron must be n
+ ¾ cycles to ensure that

Ans – Returning electrons give energy to the gap oscillations

142. The cavity magnetron uses strapping to

Ans – Prevent mode jumping

143. A magnetic field is used in the cavity magnetron to

Ans – Ensure that the electrons will orbit around the cathode

144. To avoid difficulties with strapping at high frequencies, the type of

cavity structure used in the magnetron is the

Ans – Rising sun

145. The primary purpose of the helix in a traveling wave tube is to

Ans – Reduce the axial velocity of the RF field

146. The attenuator is used in the traveling wave tube to

Ans – Prevent oscillations

147. Periodic permanent-magnet focusing is used with TWT to

Ans – Avoid the bulk of an electromagnet

148. The TWT is sometimes preferred to the magnetron as a radar

transmitter output tube because it is

Ans – Capable of a longer duty cycle

149. A magnetron whose oscillating frequency is electronically

adjustable over a wide range is called a

Ans – VTM

150. Indicate which of the following is not a TWT slow wave structure

Ans – Periodic permanent magnet

151. The glass tube of a TWT may be coated with aquadag to

Ans – Provide attenuation

152. A backward wave oscillator is based on the

Ans – Traveling wave tube

153. A parametric amplifier must be cooled

Ans – To improve the noise performance

154. A ruby master amplifier must be cooled

Ans – Because it cannot operate at room temperature

155. A disadvantage of microstrip compared with stripline is that

microstrip

Ans – Is more likely to radiate

156. The transmission system using two ground planes is

Ans – Stripline
157. Indicate the false statement, An advantage of stripline over
waveguide is its

Ans – Higher power handling capability

158. Indicate the false statement. An advantage of stripline over

microstrip is its

Ans – Easier integration with semiconductor devices

159. Surface acoustic waves propagate in

Ans – Quartz crystal

160. SAW devices may be used as

Ans – Filters

161. Indicate the false statement. FETs are preferred to bipolar

transistors at the highest frequencies because they

Ans – Lend themselves more readily to integration

162. For best low-level noise performance in the X band, an amplifier

should use

Ans – A step recovery diode

163. The biggest advantage of the TRAPATT diode over the IMPATT
diode is its

Ans – Higher efficiency

164. Indicate which of the following diodes will produce the highest
pulsed power output

Ans – RIMPATT

165. Indicate which of the following diodes does not use negative
resistance in its operation

Ans – Backward

166. One of the following is not used as a microwave mixer or detector

Ans – PIN diode

167. One of the following microwave diodes is suitable for very low-
power oscillators only

Ans – Tunnel

168. The transferred electron bulk effect occurs in

Ans – Gallium arsenide

169. The gain bandwidth frequency of microwave transistor fT is the

frequency at which the

Ans – Beta of the transistor falls to unity

170. For a microwave transistor to operate at the highest frequencies,

the (indicate the false answer)

Ans – Emitter area must be large

171. A varactor diode may be useful at microwave frequencies,

(indicate the false answer)

Ans – As an oscillator

172. If high order frequency multiplication is required from a diode

multiplier

Ans – A step recovery diode must be used

173. A parametric amplifier has an input and output frequency of 2.25

Ghz, and is pumped at 4.5Ghz. It is a

Ans – Degenerate amplifier

174. A non degenerate parametric amplifier has an input frequency fi

and a pump frequency fp. The idler frequency is

Ans – fp - fi

175. Traveling wave parametric amplifiers are used to

Ans – Provide a greater bandwidth

176. A parametric amplifier sometimes uses a circulator to

Ans – Prevent noise feedback

177. The nondegenerate one port parametric amplifier should have a
high ratio of pump to signal frequency because this

Ans – Yields a low noise figure

178. The tunnel diode

Ans – Uses a high doping level to provide a narrow junction

179. Tunnel diode is loosely coupled to its cavity in order to

Ans – Increase the frequency stability

180. The negative resistance in a tunnel diode

Ans – Is available between the peak and valley points

181. The biggest advantage of gallium antimonide over germanium for

tunnel diode use is that the former has a

Ans – Larger voltage swing

182. Negative resistance is obtained with a Gunn diode because of

Ans – Electron transfer to a less mobile energy level

183. For Gunn diodes, gallium arsenide is preferred to silicon because

the former

Ans – Has a suitable empty energy band, which silicon does not
have

184. The biggest advantage of the IMPATT diode is its

Ans – High noise

185. The magnetic field is used with a ruby master to

Ans – Provide frequency adjustment

186. The ruby master has been preferred to the ammonia master for
microwave amplification, because of the former has.

Ans – A much grater bandwidth

187. Parametric amplifiers and masters are similar to each other in that
both (Indicate false statement)
Ans – Must be cooled down to a few kelvins

188. A master RF amplifier is not really suitable for

Ans – Radar

189. The ruby laser differs form the ruby maser in that the former

Ans – IS an oscillator

190. The output from a laser is monochromatic, this means that it is

Ans – Single frequency

191. For a given average power, the peak output power of a ruby laser
may be increased by

Ans – Using Q spoiling

192. Communications lasers are used with optical fibers, rather that in
open links to

Ans – Prevent atmospheric interference

193. Indicate the false statement. The advantages of semiconductor

lasers over LEDs include

Ans – Lower cost

194. Indicate which of the following is not a binary code

Ans – Morse

195. To permit the selection of 1 out of 16 equiprobable events, the

number of bits required is

Ans – 4

196. A signaling system in which each letter of the alphabet is

represented by a different symbol is not used because

Ans – Noise would introduce too many errors

197. The Hartley law states that

Ans – The maximum rate of information transmission depends on

the channel bandwidth

198. Indicate the false statement. In order to combat noise.

Ans – The channel bandwidth may be increased

199. The most common modulation system used for telegraphy is

Ans – Frequency shift keying

200. Pulse width modulation may be generated

Ans – With a monostable multivibrator

201. Indicate which of the following systems is digital

Ans – Pulse code modulation

202. Quantizing noise occurs in

Ans – Pulse code modulation

203. The modulation system inherently most noise resistant is

Ans – Pulse code modulation

204. In order to reduce quantizing noise, one must

Ans – Increase the number of standard amplitudes

205. The Hartley-Shannon theorem sets a limit on the

Ans – Maximum capacity of a channel with a given noise level

206. Indicate which of the following pulse modulation system is analog

Ans – PWM

207. Companding is used

Ans – To protect small signals in PCM from quantizing distortion

208. The biggest disadvantage of PCM is

Ans – The large bandwidth that are required for it

209. Digital signals

Ans – All of the above

210. The event which marked the start of the modern computer age
was

Ans - Development of the transistor

211. The baud rate

Ans – Is equal to twice the bandwidth of an idea channel

212. The Shannon-Hartley law

Ans – Refers to noise

213. The code which provides for parity check is

Ans – ASCII

214. A forward error-correcting code corrects errors by

Ans – Requiring no part of the signal to be re-transmitted

215. Full duplex operation

Ans – All of the above

216. The RS – 232 interface

Ans – Interconnects data sets and transmission circuits

217. Switching systems

Ans – Improve the efficiency of data transfer

218. Broadband long distance communications were originally made

possible by the advent of

Ans – Repeater amplifiers

219. A scheme in which several channels are interleaved and then
transmitted together is known as

Ans – Frequency division multiplex

220. A basic group B

Ans – Occupies the frequency range from 60 to 108 Khz

221. Time division multiplex

Ans – Interleaves pulses belonging to different transmissions

222. The number of repeaters along a coaxial cable link depends on

Ans – The bandwidth of the system

223. A supergroup pilot is

Ans – Fed in at a GTE

224. Microwave link repeaters are typically 50 Km apart

Ans – Because of the Earth’s curvature

225. Microwave links are generally preferred to coaxial cable for

television transmission because

Ans – They have less overall phase distortion

226. Armored submarine cable is used

Ans – For the shallow shore ends of the cable

227. A submarine cable repeater contains, among other equipment

Ans – Filters for the two directions of transmission

228. A geostationary satellite

Ans – Is not really stationary at all, but orbits the Earth within a 24
hr period

229. Indicate the correct statement regarding satellite communication

Ans – A satellite earth station must have as many receive chains as

there are carriers transmitted to it.
230. Satellites used for intercontinental communications are known as

Ans – Intelsat

231. Identical telephone numbers in different parts of a country are

distinguished by their

Ans – Area codes

232. Telephone traffic is measured

Ans – In erlangs

233. In order to separate channels in a TDM receiver, it is necessary to

use

Ans – AND gates

234. To separate channels in an FDM receiver, it is necessary to use

Ans – Bandpass filters

235. Higher order TDM levels are obtained by

Ans – Dividing pulse widths

236. Losses in optical fibers can be caused by (Indicate ht false

statement)

Ans – Stepped index operation

237. The 1.55µm “window” is not yet in use with fibre optic systems
because

Ans – Suitable laser devices have not yet been developed

238. Indicate which of the following is not a submarine cable

Ans – INTELSAT V

239. Indicate which of the following is an American domsat system

Ans – TELSTAR
240. If the peak transmitted power in a radar system is increased by a
factor of 16. the maximum range will be increased by a factor of

Ans – 2

241. If the antenna diameter in a radar system is increased by a factor

of 4, the maximum range will be increased by a factor of

Ans – 4

242. If the ratio of the antenna diameter to the wavelength in a radar

system is high this will result in (Indicate false statement)

Ans - Increase capture area

243. The radar cross section of a target (Indicate the false statement)

Ans – Is equal to the actual cross sectional area for small targets

244. Flat topped rectangular pulses must be transmitted in radar to

(Indicate false statement)

Ans – Make the returned echoes easier to distinguish from noise

245. A high PRF will (Indicate false statement)

Ans – Increase the maximum range

246. The IF bandwidth of a radar receiver is inversely proportional to

the

Ans – Pulse width

247. If a return echo arrives after the allocated pulse interval

Ans – The target will appear closer than it really is

248. After a target has been acquired, the best scanning system for
tracking is

Ans – Conical

249. If the target cross section is changing, the best system for accurate
tracking is

Ans – Conical scanning

250. The biggest disadvantage of CW Doppler radar is that

Ans – It does not gives the target range

251. The A scope displays

Ans – The target range, but not position

252. The Doppler effect is used in (Indicate false statement)

Ans – Moving target plotting on the PPI

253. The coho in MTI radar operates at the

Ans – Intermediate frequency

254. The function of the quartz delay line in an MTI radar is to

Ans – Help in subtracting a complete scan from the previous scan

255. A solution to the “blind speed” problem is to

Ans – Vary the PRF

256. Indicate which one of the following applications or advantages of

radar beacons is false

Ans – More accurate tracking of enemy targets

257. Compared with other types of radar, phased array radar has the
following advantages (Indicate false statement)

Ans – Circuit simplicity

258. The number of lines per field in the United States TV system is

Ans – 262 ½

259. The number of frames per second in the United States TV system
is

Ans – 30

260. The number of lines per second in the United States TV system is

Ans – 15.750
261. The channel width in the United States TV system in Mhz is

Ans – 6

262. Interlacing is used in television to

Ans – Avoid flicker

263. The signals send by the TV transmitter to ensure correct scanning

in the receiver are called

Ans – Sync

264. In the United States color television system, the intercarrier

frequency in Mhz is

Ans – 4.5

265. Indicate which voltages are not found in the output of a normal
monochrome receiver video detector

Ans – Sweep

266. The carrier transmitted 1.25 Mhz above the bottom frequency in a
United States TV channel is the

Ans – Picture carrier

267. In television 4 : 3 represents the

Ans – Aspect ratio

268. Equalizing pulses in TV are sent during

Ans – Vertical blanking

269. An odd number of lines per frame forms part of every one of the
word’s TV systems. This is

Ans – Done to assist interlace

270. The function of the serrations in the composite video waveform is

to

Ans – Help horizontal synchronization

271. The width of the vertical sync pulse in the United States TV system
is

Ans – 3H

272. Indicate which of the following frequencies will not be found in the
output of a normal TV receiver tuner :

Ans – 4.5 Mhz

273. The video voltage applied to the picture tube of a television

receiver is fed in

Ans – Between grid and cathode

274. The circuit that separates sync pulses from the composite video
waveform is

Ans – A clipper

275. The output of the vertical amplifier, applied to the yoke in a TV

receiver, consists of

Ans – A sawtooth current

276. The HV anode supply for the horizontal retrace in a TV receiver is

generated in the

Ans – Horizontal output stage

277. Another name for the horizontal retrace in a TV receiver is the

Ans – Flyback

278. Indicate which of the following signals is not transmitted in color TV

Ans – R

279. The shadow mask in a color picture tube is used to

Ans – Ensure that each beam hits only its own dots

280. In a TV receiver, the color killer

Ans – Cuts off the chromo stages during monochrome reception