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