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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]
In these cases shields made of high magnetic permeability metal alloys can be used, such as sheets of permalloy and mu-metal [9] [10] or with nanocrystalline grain structure ferromagnetic metal coatings. [11] These materials do not block the magnetic field, as with electric shielding, but rather draw the field into themselves, providing a path ...
Radio wave diffraction is the scattering of radio frequency or lower frequencies from the Earth's ionosphere, resulting in the ability to achieve greater distance radio broadcasting. Sound wave diffraction is the bending of sound waves, as the sound travels around edges of geometric objects. This produces the effect of being able to hear even ...
A cavity resonator is one in which waves exist in a hollow space inside the device. In electronics and radio, microwave cavities consisting of hollow metal boxes are used in microwave transmitters, receivers and test equipment to control frequency, in place of the tuned circuits which are used at lower frequencies.
Radio waves can be shielded against by a conductive metal sheet or screen, an enclosure of sheet or screen is called a Faraday cage. A metal screen shields against radio waves as well as a solid sheet as long as the holes in the screen are smaller than about 1 ⁄ 20 of wavelength of the waves. [25]
Mysterious fast radio bursts, or millisecond-long bright flashes of radio waves from space, have intrigued astronomers since the first detection of the phenomenon in 2007. The enigmatic signals ...
Radio noise near in frequency to a received radio signal (in the receiver's passband) interferes (RFI) with the operation of the receiver's circuitry.The level of noise determines the maximum sensitivity and reception range of a radio receiver; if no noise were picked up with radio signals, even weak transmissions could be received at virtually any distance by making a radio receiver that had ...
Some magnetars exist below what is called a “death line,” which means their magnetic fields are too weak to release energetic emissions of radio waves. That doesn’t seem to apply to the ...