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Ground wave is important for radio signals below 30 MHz, but is generally insignificant at higher frequencies where line-of-sight propagation dominates. AM and longwave broadcasting, navigation systems such as LORAN , low-frequency time signals , non-directional beacons , and short-range HF communications all make use of it.
Harike Wetland is a Ramsar site in India Map of Ramsar sites Archipel Bolama-Bijagos Ramsar site in Guinea-Bissau Walkway in Zuvintas Biosphere Reserve. A Ramsar site is a wetland site designated to be of international importance under the Ramsar Convention, [1] also known as "The Convention on Wetlands", an international environmental treaty signed on 2 February 1971 in Ramsar, Iran, under ...
Slotted array UHF television broadcasting antenna. As shown by H. G. Booker in 1946, from Babinet's principle in optics a slot in a metal plate or waveguide has the same radiation pattern as a driven rod antenna whose rod is the same shape as the slot, with the exception that the electric field and magnetic field directions are interchanged; the antenna is a magnetic dipole instead of an ...
Also called a beam antenna [4] and parasitic array, the Yagi is widely used as a directional antenna on the HF, VHF and UHF bands. [3] [4] It has moderate to high gain of up to 20 dBi, [3] depending on the number of elements used, and a front-to-back ratio of up to 20 dB.
The Ramsar Convention on Wetlands of International Importance Especially as Waterfowl Habitat is an international treaty for the conservation and sustainable use of Ramsar sites . [2] It is also known as the Convention on Wetlands .
RWR systems can be installed in all kind of airborne, sea-based, and ground-based assets such as aircraft, ships, automobiles, military bases. Depending on the market the RWR system is designed for, it can be as simple as detecting the presence of energy in a specific radar band, such as the frequencies of known surface-to-air missile systems.
Palustrine wetlands include any inland wetland that contains ocean-derived salts in concentrations of less than 0.5 parts per thousand, and is non-tidal. [1] The word palustrine comes from the Latin word palus or marsh. [2] Wetlands within this category include inland marshes and swamps as well as bogs, fens, pocosins, tundra and floodplains.
A high perimeter to volume ratio, such as in small wetlands, means that the surface area through which water can infiltrate into the groundwater is high. [8] Groundwater recharge is typical in small wetlands such as prairie potholes, which can contribute significantly to recharge of regional groundwater resources. [8]