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Earth–ionosphere waveguide
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The Earth–ionosphere waveguide is the phenomenon in which certain radio waves can propagate in the space between the ground and the boundary of the ionosphere. Because the ionosphere contains charged
Figure 1. Geometry of ray propagation within the Earth–ionosphere waveguide. The ground wave and two sky waves are displayed
Figure 1. Geometry of ray propagation within the Earth–ionosphere waveguide. The ground wave and two sky waves are displayed
Figure 2. Real and virtual reflection height
Figure 2. Real and virtual reflection height
Figure 3. Normalized vertical field strength Ez vs. distance ρ in magnitude (solid line, left ordinate) and phase (dashed line, right ordinate).
Figure 3. Normalized vertical field strength Ez vs. distance ρ in magnitude (solid line, left ordinate) and phase (dashed line, right ordinate).
Figure 4. Magnitude of transfer functions of the zeroth mode and the first mode versus frequency at distances 1000, 3000, and 10000 km using day time
Figure 4. Magnitude of transfer functions of the zeroth mode and the first mode versus frequency at distances 1000, 3000, and 10000 km using day time conditions.
Extremely low frequency
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Extremely low frequency is the ITU designation for electromagnetic radiation with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospher
Earth–ionosphere waveguide
…contains charged particles, it can behave as a conductor. The earth operates as a ground plane, and the resulting cavity behaves as a large waveguide. Extremely low frequency (ELF) (< 3 kHz) and very low frequency (VLF) (3–30 kHz) signals can propagate efficiently in this waveguide. For instance, lightning strikes launch a…
1982 aerial view of the U.S. Navy Clam Lake, Wisconsin, ELF transmitter facility, used to communicate with deeply submerged submarines. The rights of
1982 aerial view of the U.S. Navy Clam Lake, Wisconsin, ELF transmitter facility, used to communicate with deeply submerged submarines. The rights of way of the two perpendicular 14 mile (23 km) overhead transmission lines, which constituted the ground dipole antenna, and which radiated the ELF waves, can be seen at the lower left.