Online Questions and Answers Topic Outline
- MCQs in Electromagnetic Radiation
- MCQs in Radio Spectrum
- MCQs in Wave Propagation
- MCQs in Radiation Patterns
- MCQs in Wavelength Calculations
- MCQs in Radiation Resistance
- MCQs in Diversity Systems
MCQs in Radiation and Wave Propagation Series
Following is the list of multiple choice questions in this brand new series:
Continue Practice Exam Test Questions Part VI of the Series
251. The curvature of the Earth presents a horizon to space wave propagation commonly called _________.
- a. Optical horizon
- b. Radio horizon
- c. Horizontal horizon
- d. Vertical horizon
252. Electromagnetic waves that are directed above the horizon level is called _________.
- a. direct waves
- b. sky waves
- c. space waves
- d. surface waves
253. The refracting and reflecting action of the ionosphere and the ground is called
- a. sliding
- b. skipping
- c. hopping
- d. boosting
254. An electrical energy that is escaped in free space
- a. Electrical signal
- b. Electromagnetic waves
- c. Magnetic waves
- d. Electromagnetism
255. The layer of the ionosphere which farthest from the sun
- a. D layer
- b. E layer
- c. F1 layer
- d. F2 layer
256. A condition which manifest itself in the form of double-image distortion
- a. running
- b. fading
- c. ghosting
- d. snowing
257. The D layer of the ionosphere absorbs _________ waves.
- a. LF and MF
- b. MF and HF
- c. HF and VHF
- d. VHF and UHF
258. The E layer of the ionosphere is sometimes called _________
- a. Kennely-Heavisides
- b. Sporadic-E layer
- c. E-densed layer
- d. Kennely layer
259. It is defined as the higher frequency that can be propagated directly upward and still be returned to earth by the ionosphere
- a. critical angle
- b. maximum usable frequency
- c. critical frequency
- d. virtual height
260. The maximum vertical angle at which electromagnetic waves can be propagated and still be reflected back by the ionosphere
- a. numerical aperture
- b. incident angle
- c. critical angle
- d. refracted angle
261. It is defined as the plane joining all points of equal phase
- a. rays
- b. electromagnetic wave
- c. wavefront
- d. isotropic source
262. It is the height above Earth’s surface from which a reflected wave appears to have been reflected.
- a. virtual height
- b. maximum height
- c. vertical height
- d. horizontal height
263. It is the highest frequency that can be used for sky wave propagation between two specific points on Earth’s surface
- a. optimum working frequency
- b. maximum usable frequency
- c. critical frequency
- d. maximum frequency
264. The polarization of electromagnetic waves can be determined by the direction of the
- a. E field
- b. H field
- c. propagation
- d. both E and H field
265. 85 percent of the maximum usable frequency (MUF) is called _________.
- a. maximum usable frequency
- b. optimum working frequency
- c. critical frequency
- d. maximum frequency
266. It is defined as the minimum distance from the transmit antenna that a sky wave at a given frequency will be returned to earth.
- a. skip distance
- b. skip zone
- c. skip frequency distance
- d. skip zone frequency
267. At distance greater than the skip distance, two rays can take different paths and still be returned to the same point on Earth. The two rays are called lower rays and _________.
- a. Pedersen ray
- b. Light ray
- c. Huygen’s ray
- d. Miller’s ray
268. Undesired radiated energy from a radio transmitter or in another source.
- a. ESD
- b. EMI
- c. RFI
- d. ESI
269. The area between where the surface waves are completely dissipated and the point where the first sky wave returns to earth is called _________.
- a. skip distance
- b. skip distance zone
- c. optical horizon
- d. quiet zone
270. The undesired radiated energy that may cause interference with other electronic equipment in the vicinity.
- a. ESD
- b. EMI
- c. RFI
- d. ESI
271. It is defined as the loss incurred by an electromagnetic wave as it propagates in a straight line through a vacuum with no absorption or reflection of energy from nearby objects.
- a. free-space path loss
- b. free space loss
- c. path loss
- d. any of these
272. To increase the transmission distance of a UHF signal, which of the following should be done?
- a. increase the antenna gain
- b. increase antenna height
- c. increase transmitter power
- d. increase receiver sensitivity
273. For a carrier frequency of 6 GHz and a distance of 50 km, determine the free-space path loss
- a. 132 dB
- b. 123 dB
- c. 142 dB
- d. 152 dB
274. A microwave-transmitting antenna is 550 ft. high. The receiving antenna is 200 ft. high. The maximum transmission distance is
- a. 20 mi
- b. 33.2 mi
- c. 38.7 mi
- d. 53.2 mi
275. Indicate which one of the following term applies to troposcatter propagation
- a. SIDs
- b. Fading
- c. Atmospheric storms
- d. Faraday’s rotation
276. Line-of-sight communications is not a factor in which frequency range?
- a. VHF
- b. UHF
- c. HF
- d. Microwave
277. VLF waves are used for some types of services because
- a. of the low powers required
- b. the transmitting antenna are of convenient size
- c. they are very reliable
- d. affected by the solar cycle
278. Microwave signals propagate by way of the
- a. direct wave
- b. sky wave
- c. surface wave
- d. standing wave
279. Indicate which of the following frequencies cannot be used for reliable beyond-the-horizon terrestrial communications without repeaters:
- a. 20 kHz
- b. 15 MHz
- c. 900 MHz
- d. 12 GHz
280. The type of radio wave responsible for long-distance communications by multiple skips is the
- a. ground wave
- b. direct wave
- c. surface waves
- d. sky wave
281. High-frequency waves are
- a. absorbed by the F2 layer
- b. reflected by the D layer
- c. capable of use for long-distance communications on the moon
- d. affected by the solar cycle
282. The ionosphere has its greatest effect on signals in what frequency range?
- a. 300 kHz to 3 MHz
- b. 3 to 30 MHz
- c. 30 to 300 MHz
- d. above 300 MHz
283. Distances near the skip distance should be used for sky-wave propagation
- a. to avoid tilting
- b. to prevent sky-wave and upper ray interference
- c. to avoid Faraday effect
- d. so as not to exceed the critical frequency
284. Ground-wave communications is most effective in what frequency range?
- a. 300 kHz to 3 MHz
- b. 3 to 30 MHz
- c. 30 to 300 MHz
- d. above 300 MHz
285. The ionosphere causes radio signals to be
- a. diffused
- b. absorbed
- c. refracted
- d. reflected
286. Helical antenna are often used for satellite tracking at VHF because of
- a. troposcatter
- b. superrefraction
- c. ionospheric refraction
- d. the Faraday effect
287. A ship-to-ship communication system is plagued by fading. The best solution seem to use of
- a. a more directional antenna
- b. a broadband antenna
- c. frequency diversity
- d. space diversity
288. It is defined as the ratio of the electric field intensity of the reflected wave to that of the incident wave
- a. refractive index
- b. numerical aperture
- c. reflection coefficient
- d. absorption coefficient
289. It is the measure of energy received per unit time, per unit area, per unit frequency interval.
- a. solar intensity
- b. sunspot
- c. solar flare
- d. solar flux
290. A long period with lack of any solar activity
- a. El Niño
- b. La Niña
- c. Maunder period
- d. Sunspots
291. As a ground-wave signal moves away from the transmitter, the ground wave eventually disappears due to the
- a. absorption
- b. tilting
- c. refraction
- d. diffraction
292. It is the lowest layer of the atmosphere where all weather disturbances takes place
- a. D layer
- b. Stratosphere
- c. Ionosphere
- d. Troposphere
293. It is the lower limit of the range of frequencies that provide useful communication between two given points by the way of the ionosphere.
- a. MUF
- b. LUF
- c. OWF
- d. MMF
294. It is the area that lies between the outer limit of the ground-wave range and the inner edge of energy return from the ionosphere
- a. skip distance
- b. skip zone
- c. virtual height
- d. optical horizon
295. Variations brought about by the rotation of the earth around its axis.
- a. cyclical rotation
- b. seasonal variation
- c. diurnal variation
- d. weather variation
296. Ionospheric irregularity caused by solar flares, which are gigantic emissions of hydrogen from the sun.
- a. Sudden ionospheric disturbances
- b. Dillenger fadeouts
- c. Mogul-Delliger fadeouts
- d. Any of these
297. It is a type of fading caused by so-called Faraday effect or Faraday rotation
- a. interference fading
- b. absorption fading
- c. selective fading
- d. polarization fading
298. Radio horizon is _________ greater than the optical horizon.
- a. one-third
- b. four-third
- c. two-third
- d. twice
299. An increase in temperature with height which gives rise to superrefraction or ducting is known as _________.
- a. height inversion
- b. depth inversion
- c. temperature inversion
- d. ionospheric inversion
300. A region in which superrefraction occurs which is formed in the troposphere when the layer of cool air becomes trapped underneath a layer of warmer air.
- a. duct
- b. dielectric area
- c. gateway
- d. window
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