Properties of radio waves and propagation modes Flashcards
Why are direct (not via a repeater) UHF signals rarely heard from stations outside your local coverage area? (T3C01)
UHF signals are usually not reflected by the ionsosphere
Why do VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations? (T3C11)
The Earth seems less curved to radio waves than to light
What should you do if another operator reports that your station’s 2 meter signals were strong just a moment ago, but now they are weak or distorted? (T3A01)
Try moving a few feet or changing the direction of your antenna, if possible, as reflections may be causing multi-path distortion
What may occur if data signals arrive via multiple paths? (T3A10)
Error rates are likely to increase
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? (T3A05)
Try to find a path that reflects signals to the repeater
Which of the following effects might cause radio signals to be heard despite obstructions between the transmitting and receiving stations? (T3C05)
Knife-edge diffraction
What term is commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting? (T3A06)
Picket fencing
Why might the range of VHF and UHF signals be greater in the winter? (T3A02)
Less absorption by vegetation
What property of a radio wave is used to describe its polarization? (T3B02)
The orientation of the electric field
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? (T3A04)
Signals could be significantly weaker
What antenna polarization is normally used for long-distance weak-signal CW and SSB contacts using the VHF and UHF bands? (T3A03)
Horizontal
Which of the following propagation types is most commonly associated with occasional strong over-the-horizon signals on the 10, 6, and 2 meter bands? (T3C04)
Sporatic E
What is a characteristic of VHF signals received via auroral reflection? (T3C03)
The signals exhibit rapid fluctuations of strength and often sound distroted
What band is best suited to communicating via meteor scatter? (T3C07)
6 meter band
What mode is responsible for allowing over-the-horizon VHF and UHF communications to ranges of approximately 300 miles on a regular basis? (T3C06)
Tropospheric Scatter
