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Near vertical incidence skywave, or NVIS, is a skywave radio-wave propagation path that provides usable signals in the medium distances range — usually 0–650 km (0–400 miles). It is used for military and paramilitary communications, broadcasting, [ 1 ] especially in the tropics, and by radio amateurs for nearby contacts circumventing line ...
Lying approximately halfway between 80 m (3.5 MHz) and 40 m (7 MHz), the 60-meter (5 MHz) band forms a communication bridge when propagation effects make use of 80 or 40 m impossible for local-to-medium distance communications – usually between 0–650 km (0–400 miles), often needed in emergency communication scenarios where there is no ...
Radio waves (black) reflecting off the ionosphere (red) during skywave propagation. Line altitude in this image is significantly exaggerated and not to scale. In radio communication, skywave or skip refers to the propagation of radio waves reflected or refracted back toward Earth from the ionosphere, an electrically charged layer of the upper atmosphere.
In radio propagation, horizontal plane is used to plot an antenna's relative field strength in relation to the ground (which directly affects a station's coverage area) on a polar graph. Normally the maximum of 1.000 or 0 dB is at the top, which is labeled 0 o, running clockwise back around to the top at 360°. Other field strengths are ...
The aurora is expected to be bright and visible in multiple northern U.S. states Oct. 3 through Oct. 5 as well as from the lower Midwest to Oregon.
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. [1]: 26‑1 As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. [2]
VOACAP (Voice of America Coverage Analysis Program) [1] is a radio propagation model that uses empirical data to predict the point-to-point path loss and coverage of a given transceiver if given as inputs: two antennas (configuration and position), solar weather, and time/date.
This enables near vertical incidence skywave (NVIS) communication up to 300 km (190 miles) in mountainous regions. For NVIS, a typical radiation efficiency of around 1% is acceptable, because signal paths can be established with 1 W of radiated power or less – feasible when a 100 W transmitter is used.