T3 – RADIO WAVE PROPAGATION – [3 Exam Questions - 3 Groups] Flashcards
“Why do VHF signal strengths sometimes vary greatly when the antenna is moved only a few feet?”
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
D. All these choices are correct
C. Multipath propagation cancels or reinforces signals
“What is the effect of vegetation on UHF and microwave signals?”
A. Knife-edge diffraction
B. Absorption
C. Amplification
D. Polarization rotation
B. Absorption
“What antenna polarization is normally used for long-distance CW and SSB contacts on the VHF and UHF bands?”
A. Right-hand circular
B. Left-hand circular
C. Horizontal
D. Vertical
C. Horizontal
“What happens when antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization?”
A. The modulation sidebands might become inverted
B. Received signal strength is reduced
C. Signals have an echo effect
D. Nothing significant will happen
B. Received signal strength is reduced
“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?”
A. Change from vertical to horizontal polarization
B. Try to find a path that reflects signals to the repeater
C. Try the long path
D. Increase the antenna SWR
B. Try to find a path that reflects signals to the repeater
“What is the meaning of the term “picket fencing”?”
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
D. Local vs long-distance communications
B. Rapid flutter on mobile signals due to multipath propagation
“What weather condition might decrease range at microwave frequencies?”
A. High winds
B. Low barometric pressure
C. Precipitation
D. Colder temperatures
C. Precipitation
“What is a likely cause of irregular fading of signals propagated by the ionosphere?”
A. Frequency shift due to Faraday rotation
B. Interference from thunderstorms
C. Intermodulation distortion
D. Random combining of signals arriving via different paths
D. Random combining of signals arriving via different paths
“Which of the following results from the fact that signals propagated by the ionosphere are elliptically polarized?”
A. Digital modes are unusable
B. Either vertically or horizontally polarized antennas may be used for transmission or reception
C. FM voice is unusable
D. Both the transmitting and receiving antennas must be of the same polarization
B. Either vertically or horizontally polarized antennas may be used for transmission or reception
“What effect does multi-path propagation have on data transmissions?”
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
D. Error rates are likely to increase
D. Error rates are likely to increase
“Which region of the atmosphere can refract or bend HF and VHF radio waves?”
A. The stratosphere
B. The troposphere
C. The ionosphere
D. The mesosphere
C. The ionosphere
“What is the effect of fog and rain on signals in the 10 meter and 6 meter bands?”
A. Absorption
B. There is little effect
C. Deflection
D. Range increase
B. There is little effect
“What is the relationship between the electric and magnetic fields of an electromagnetic wave?”
A. They travel at different speeds
B. They are in parallel
C. They revolve in opposite directions
D. They are at right angles
D. They are at right angles
“What property of a radio wave defines its polarization?”
A. The orientation of the electric field
B. The orientation of the magnetic field
C. The ratio of the energy in the magnetic field to the energy in the electric field
D. The ratio of the velocity to the wavelength
A. The orientation of the electric field
“What are the two components of a radio wave?”
A. Impedance and reactance
B. Voltage and current
C. Electric and magnetic fields
D. Ionizing and non-ionizing radiation
C. Electric and magnetic fields