86 lines
3.5 KiB
Markdown
86 lines
3.5 KiB
Markdown
T3A - Radio wave characteristics: how a radio signal travels, fading, multipath, polarization, wavelength vs absorption; Antenna orientation
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- [[T3A01]] (C)
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Why do VHF signal strengths sometimes vary greatly when the antenna is moved only a few feet? #card
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- A. The signal path encounters different concentrations of water vapor
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- B. VHF ionospheric propagation is very sensitive to path length
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- C. Multipath propagation cancels or reinforces signals
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- D. All these choices are correct
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- [[T3A02]] (B)
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What is the effect of vegetation on UHF and microwave signals? #card
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- A. Knife-edge diffraction
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- B. Absorption
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- C. Amplification
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- D. Polarization rotation
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- [[T3A03]] (C)
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What antenna polarization is normally used for long-distance CW and SSB contacts on the VHF and UHF bands? #card
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- A. Right-hand circular
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- B. Left-hand circular
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- C. Horizontal
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- D. Vertical
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- [[T3A04]] (B)
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What happens when antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization? #card
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- A. The modulation sidebands might become inverted
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- B. Received signal strength is reduced
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- C. Signals have an echo effect
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- D. Nothing significant will happen
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- [[T3A05]] (B)
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When using a directional antenna, how might your station be able to communicate with a distant repeater if buildings or obstructions are blocking the direct line of sight path? #card
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- A. Change from vertical to horizontal polarization
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- B. Try to find a path that reflects signals to the repeater
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- C. Try the long path
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- D. Increase the antenna SWR
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- [[T3A06]] (B)
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What is the meaning of the term “picket fencing”? #card
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- A. Alternating transmissions during a net operation
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- B. Rapid flutter on mobile signals due to multipath propagation
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- C. A type of ground system used with vertical antennas
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- D. Local vs long-distance communications
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- [[T3A07]] (C)
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What weather condition might decrease range at microwave frequencies? #card
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- A. High winds
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- B. Low barometric pressure
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- C. Precipitation
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- D. Colder temperatures
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- [[T3A08]] (D)
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What is a likely cause of irregular fading of signals propagated by the ionosphere? #card
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- A. Frequency shift due to Faraday rotation
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- B. Interference from thunderstorms
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- C. Intermodulation distortion
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- D. Random combining of signals arriving via different paths
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- [[T3A09]] (B)
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Which of the following results from the fact that signals propagated by the ionosphere are elliptically polarized? #card
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- A. Digital modes are unusable
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- B. Either vertically or horizontally polarized antennas may be used for transmission or reception
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- C. FM voice is unusable
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- D. Both the transmitting and receiving antennas must be of the same polarization
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- [[T3A10]] (D)
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What effect does multi-path propagation have on data transmissions? #card
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- A. Transmission rates must be increased by a factor equal to the number of separate paths observed
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- B. Transmission rates must be decreased by a factor equal to the number of separate paths observed
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- C. No significant changes will occur if the signals are transmitted using FM
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- D. Error rates are likely to increase
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- [[T3A11]] (C)
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Which region of the atmosphere can refract or bend HF and VHF radio waves? #card
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- A. The stratosphere
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- B. The troposphere
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- C. The ionosphere
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- D. The mesosphere
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- [[T3A12]] (B)
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What is the effect of fog and rain on signals in the 10 meter and 6 meter bands? #card
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- A. Absorption
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- B. There is little effect
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- C. Deflection
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- D. Range increase
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