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Automated Maritime Telecommunications System
Automated Maritime Telecommunications System (AMTS) is a commercial mobile radio service used within the United States. It operates within the VHF frequency range, just above the North American Band III television range, and offers both voice and data communications to maritime customers. The system is operated by a network of private carriers across the country, with coverage primarily including coastal and inland waterways. History In 1981, the FCC proposed the Inland Waterways Communication System (IWCS), a commercial maritime radio service with the proposed purpose of expanding private maritime communication and that was to operate from 216 to 220 MHz.R. Eckert: ''Guidance for Evaluating the Potential for Interference to TV From Stations of Inland Waterways Communications Systems'', Federal Communications Commission Office of Science and Technology, 1982 Earlier reports had studied the feasibility of using this frequency band, but warned of the high probability of adjacen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Very High Frequency
Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves ( radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF). VHF radio waves propagate mainly by line-of-sight, so they are blocked by hills and mountains, although due to refraction they can travel somewhat beyond the visual horizon out to about 160 km (100 miles). Common uses for radio waves in the VHF band are Digital Audio Broadcasting (DAB) and FM radio broadcasting, television broadcasting, two-way land mobile radio systems (emergency, business, private use and military), long range data communication up to several tens of kilometers with radio modems, amateur radio, and marine communications. Air traffic control communications and air navigation systems (e.g. VOR and ILS) wo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Band III
Band III is the name of the range of radio frequencies within the very high frequency (VHF) part of the electromagnetic spectrum from 174 to 240 megahertz (MHz). It is primarily used for radio and television broadcasting. It is also called high-band VHF, in contrast to Bands I and II. Broadcast Television North America The band is subdivided into seven channels for television broadcasting, each occupying 6 MHz. Europe European Band III allocations vary from country to country, with channel widths of 7 or 8 MHz. The standard channel allocations for European countries that use System B with 7 MHz channel spacing are as follows: The Irish (8 MHz) system is shown below. Oceania Australia has allocated 8 channels in Band III for digital television, each with 7 MHz bandwidth. Russia and other former members of OIRT Russian analog television is transmitted using System D with 8 MHz channel bandwidth. Radio The band came into use for radio broa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adjacent-channel Interference
Adjacent-channel interference (ACI) is interference caused by extraneous power from a signal in an adjacent channel. ACI may be caused by inadequate filtering (such as incomplete filtering of unwanted modulation products in FM systems), improper tuning or poor frequency control (in the reference channel, the interfering channel or both). ACI is distinguished from crosstalk.Federal Standard 1037Accessed: 2011-10-19. (Archived by WebCite at http://webcitation.org/62Z8qe0pC)/ref> Origin The adjacent-channel interference which receiver A experiences from a transmitter B is the sum of the power that B emits into A's channel—known as the "unwanted emission", and represented by the ACLR (Adjacent Channel Leakage Ratio)—and the power that A picks up from B's channel, which is represented by the ACS (Adjacent Channel Selectivity). B emitting power into A's channel is called adjacent-channel leakage (unwanted emissions). It occurs for two reasons. First, because RF filters require a rol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Television Channel Frequencies
The following tables show the frequencies assigned to broadcast television channels in various regions of the world, along with the ITU letter designator for the system used. The frequencies shown are for the analogue video and audio carriers. The channel itself occupies several megahertz of bandwidth. For example, North American channel 1 occupies the spectrum from 44 to 50 MHz. See Broadcast television systems for a table of signal characteristics, including bandwidth, by ITU letter designator. VHF Americas (most countries), South Korea, Taiwan, Burma (Myanmar) and the Philippines During World War II, the frequencies originally assigned as channels 13 to 18 were appropriated by the U.S. military, which still uses them to this day. It was also decided to move the allocation for FM radio from the 42-50 MHz band to a larger 88-106 MHz band (later extended to the current 88-108 MHz FM band). This required a reassignment of the VHF channels to the plan curre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Balanced Budget Act Of 1997
The Balanced Budget Act of 1997 () was an omnibus legislative package enacted by the United States Congress, using the budget Reconciliation (U.S. Congress), reconciliation process, and designed to balance the federal budget by 2002. This act was enacted during Bill Clinton's second term as president. According to the Congressional Budget Office, the act was to result in $160 billion in spending reductions between 1998 and 2002. After taking into account an increase in spending on Welfare and Children's Healthcare, the savings totaled $127 billion. Medicare cuts were responsible for $112 billion, and hospital inpatient and outpatient payments covered $44 billion. In order to reduce Medicare (United States), Medicare spending, the act reduced payments to health service providers. However, some of those changes to payments were reversed by subsequent legislation in 1999 and 2000. Overview The Balanced Budget Act was introduced on June 24, 1997, by Republican Party (United State ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Effective Radiated Power
Effective radiated power (ERP), synonymous with equivalent radiated power, is an IEEE standardized definition of directional radio frequency (RF) power, such as that emitted by a radio transmitter. It is the total power in watts that would have to be radiated by a half-wave dipole antenna to give the same radiation intensity (signal strength or power flux density in watts per square meter) as the actual source antenna at a distant receiver located in the direction of the antenna's strongest beam (main lobe). ERP measures the combination of the power emitted by the transmitter and the ability of the antenna to direct that power in a given direction. It is equal to the input power to the antenna multiplied by the gain of the antenna. It is used in electronics and telecommunications, particularly in broadcasting to quantify the apparent power of a broadcasting station experienced by listeners in its reception area. An alternate parameter that measures the same thing is effec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Force Space Surveillance System
The AN/FPS-133 Air Force Space Surveillance System, colloquially known as the Space Fence, was a U.S. government multistatic radar system built to detect orbital objects passing over America. It is a component of the U.S. space surveillance network, and according to the U.S. Navy was able to detect basketball sized () objects at heights up to . The system ceased operation in September 2013. Plans for a new space fence are underway with sites at the Kwajalein Atoll in the Marshall Islands, along with an option for another radar site in Western Australia. The operation's headquarters were at Dahlgren, Virginia, and radar stations were spread out across the continental United States at roughly the level of the 33rd parallel north. Description There were three transmitter sites in the system: * 216.983 MHz at Lake Kickapoo, Texas () (Master transmitter) * 216.970 MHz at Gila River, Arizona () * 216.990 MHz at Jordan Lake, Alabama () The master transmitter at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
