Technician Licensing Class.ppt

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1、Technician Licensing Class,Supplement T3, Questions Only Radio Wave Characteristics 3 Exam Questions, 3 Groups,Element 2 Technician Class Question Pool T3 Radio wave characteristics, radio and electromagnetic properties, propagation modes 3 Exam Questions 3 Groups,Valid July 1, 2010 Through June 30,

2、 2014,3,T3A01 What should you do if another operator reports that your stations 2 meter signals were strong just a moment ago, but now they are weak or distorted?,Change the batteries in your radio to a different type Turn on the CTCSS tone Ask the other operator to adjust his squelch control Try mo

3、ving a few feet, as random reflections may be causing multi-path distortion,4,T3A02 Why are UHF signals often more effective from inside buildings than VHF signals?,Change the batteries in your radio to a different type The shorter wavelength allows them to more easily penetrate the structure of bui

4、ldings This is incorrect; VHF works better than UHF inside buildings UHF antennas are more efficient than VHF antennas,5,T3A03 What antenna polarization is normally used for long-distance weak-signal CW and SSB contacts using the VHF and UHF bands?,Right-hand circular Left-hand circular Horizontal V

5、ertical,6,T3A04 What can happen if the antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization?,The modulation sidebands might become inverted Signals could be significantly weaker Signals have an echo effect on voices Nothing significant will happen,7,

6、T3A05 When using a directional antenna, how might your station be able to access a distant repeater if buildings or obstructions are blocking the direct line of sight path?,Change from vertical to horizontal polarization Try to find a path that reflects signals to the repeater Try the long path Incr

7、ease the antenna SWR,8,T3A06 What term is commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting?,Flip-flopping Picket fencing Frequency shifting Pulsing,9,T3A07 What type of wave carries radio signals between transmitting and rec

8、eiving stations?,Electromagnetic Electrostatic Surface acoustic Magnetostrictive,10,T3A08 What is the cause of irregular fading of signals from distant stations during times of generally good reception.,Absorption of signals by the “D“ layer of the ionosphere Absorption of signals by the “E“ layer o

9、f the ionosphere Random combining of signals arriving via different path lengths Intermodulation distortion in the local receiver,11,T3A09 Which of the following is a common effect of “skip“ reflections between the Earth and the ionosphere?,The sidebands become reversed at each reflection The polari

10、zation of the original signal is randomized The apparent frequency of the received signal is shifted by a random amount Signals at frequencies above 30 MHz become stronger with each reflection,12,T3A10 What may occur if VHF or UHF data signals propagate over multiple paths?,Transmission rates can be

11、 increased by a factor equal to the number of separate paths observed Transmission rates must be decreased by a factor equal to the number of separate paths observed No significant changes will occur if the signals are transmitting using FM Error rates are likely to increase,13,T3A11 Which part of t

12、he atmosphere enables the propagation of radio signals around the world?,The stratosphere The troposphere The ionosphere The magnetosphere,14,T3B01 What is the name for the distance a radio wave travels during one complete cycle?,Wave speed Waveform Wavelength Wave spread,15,T3B02 What term describe

13、s the number of times per second that an alternating current reverses direction?,Pulse rate Speed Wavelength Frequency,16,T3B03 What are the two components of a radio wave?,AC and DC Voltage and current Electric and magnetic fields Ionizing and non-ionizing radiation,17,T3B04 How fast does a radio w

14、ave travel through free space?,At the speed of light At the speed of sound Its speed is inversely proportional to its wavelength Its speed increases as the frequency increases,18,T3B05 How does the wavelength of a radio wave relate to its frequency?,The wavelength gets longer as the frequency increa

15、ses The wavelength gets shorter as the frequency increases There is no relationship between wavelength and frequency The wavelength depends on the bandwidth of the signal,19,T3B06 What is the formula for converting frequency to wavelength in meters?,Wavelength in meters equals frequency in hertz mul

16、tiplied by 300 Wavelength in meters equals frequency in hertz divided by 300 Wavelength in meters equals frequency in megahertz divided by 300 Wavelength in meters equals 300 divided by frequency in megahertz,20,T3B07 What property of radio waves is often used to identify the different frequency ban

17、ds?,The approximate wavelength The magnetic intensity of waves The time it takes for waves to travel one mile The voltage standing wave ratio of waves,21,T3B08 What are the frequency limits of the VHF spectrum?,30 to 300 kHz 30 to 300 MHz 300 to 3000 kHz 300 to 3000 MHz,22,T3B09 What are the frequen

18、cy limits of the UHF spectrum?,30 to 300 kHz 30 to 300 MHz 300 to 3000 kHz 300 to 3000 MHz,23,T3B10 What frequency range is referred to as HF?,300 to 3000 MHz 30 to 300 MHz 3 to 30 MHz 300 to 3000 kHz,24,T3B11 What is the approximate velocity of a radio wave as it travels through free space?,3000 ki

19、lometers per second 300,000,000 meters per second 300,000 miles per hour 186,000 miles per hour,25,T3C01 Why are “direct“ (not via a repeater) UHF signals rarely heard from stations outside your local coverage area?,They are too weak to go very far FCC regulations prohibit them from going more than

20、50 miles UHF signals are usually not reflected by the ionosphere They collide with trees and shrubbery and fade out,26,T3C02 Which of the following might be happening when VHF signals are being received from long distances?,Signals are being reflected from outer space Signals are arriving by sub-sur

21、face ducting Signals are being reflected by lightning storms in your area Signals are being refracted from a sporadic E layer,27,T3C03 What is a characteristic of VHF signals received via auroral reflection?,Signals from distances of 10,000 or more miles are common The signals exhibit rapid fluctuat

22、ions of strength and often sound distorted These types of signals occur only during winter nighttime hours These types of signals are generally strongest when your antenna is aimed to the south (for stations in the Northern Hemisphere),28,T3C04 Which of the following propagation types is most common

23、ly associated with occasional strong over-the- horizon signals on the 10, 6, and 2 meter bands?,Backscatter Sporadic E D layer absorption Gray-line propagation,29,T3C05 What is meant by the term “knife-edge“ propagation?,Signals are reflected back toward the originating station at acute angles Signa

24、ls are sliced into several discrete beams and arrive via different paths Signals are partially refracted around solid objects exhibiting sharp edges Signals propagated close to the band edge exhibiting a sharp cutoff,30,T3C06 What mode is responsible for allowing over-the- horizon VHF and UHF commun

25、ications to ranges of approximately 300 miles on a regular basis?,Tropospheric scatter D layer refraction F2 layer refraction Faraday rotation,31,T3C07 What band is best suited to communicating via meteor scatter?,10 meters 6 meters 2 meters 70 cm,32,T3C08 What causes “tropospheric ducting“?,Dischar

26、ges of lightning during electrical storms Sunspots and solar flares Updrafts from hurricanes and tornadoes Temperature inversions in the atmosphere,33,T3C09 What is generally the best time for long- distance 10 meter band propagation?,During daylight hours During nighttime hours When there are coron

27、al mass ejections Whenever the solar flux is low,34,T3C10 What is the radio horizon?,The distance at which radio signals between two points are effectively blocked by the curvature of the Earth The distance from the ground to a horizontally mounted antenna The farthest point you can see when standin

28、g at the base of your antenna tower The shortest distance between two points on the Earths surface,35,T3C11 Why do VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations?,Radio signals move somewhat faster than the speed of light Radio waves are not blocked by dust particles The Earth seems less curved to radio waves than to light Radio waves are blocked by dust particles,