Height above average terrain (HAAT), or (less popularly) effective height above average terrain (EHAAT), is the vertical position of an antenna site is above the surrounding landscape. HAAT is used extensively in FM radio and television, as it is more important than effective radiated power (ERP) in determining the range of broadcasts (VHF and UHF in particular, as they are line of sight transmissions). For international coordination, it is officially measured in meters, even by the Federal Communications Commission in the United States, as Canada and Mexico have extensive border zones where stations can be received on either side of the international boundaries. Stations that want to increase above a certain HAAT must reduce their power accordingly, based on the maximum distance their station class is allowed to cover (see List of North American broadcast station classes for more information on this).
The FCC procedure to calculate HAAT is: from the proposed or actual antenna site, either 12 or 16 radials were drawn, and points at 2, 4, 6, 8, and 10 miles (16 km) radius along each radial were used. The entire radial graph could be rotated to achieve the best effect for the station. The altitude of the antenna site, minus the average altitude of all the specified points, is the HAAT. This can create some unusual cases, particularly in mountainous regions—it is possible to have a negative number for HAAT (the transmitter would not be located underground, but rather in a valley, with hills on both sides taller than the transmitter itself, for example).
The FCC has divided the Contiguous United States into three zones for the determination of spacing between FM and TV stations using the same frequencies. FM and TV stations are assigned maximum ERP and HAAT values, depending on their assigned zones, to prevent co-channel interference.
FM broadcast zones in the U.S.
The FCC regulations for ERP and HAAT are listed under Title 47, Part 73 of the Code of Federal Regulations (CFR).
Zone I (the most densely populated zone) consists of the entire land masses of the following states: Connecticut, Delaware, Illinois, Indiana, Maryland, Massachusetts, New Jersey, Ohio, Pennsylvania, Rhode Island, and West Virginia; in addition to the northern and eastern portions of Virginia; the areas of Michigan and southeastern Wisconsin south of 43° 30' north latitude; the coastal strip of Maine; the areas of New Hampshire and Vermont south of 45° north latitude; and the areas of western New York south of 43° 30' north latitude and eastern New York south of 45° north latitude. In addition, Zone I-A (FM only) consists of all of California south of 40° north latitude, Puerto Rico and the U.S. Virgin Islands (If the dividing line between Zones I and II runs through a city, that city is considered to be in Zone I.).
Zones I and I-A have the most "grandfathered" overpowered stations, which are allowed the same extended coverage areas that they had before the zones were established. One of the most powerful of these stations is WBCT in Grand Rapids, Michigan, which operates at 320,000 watts and 238 meters (781 ft) HAAT.
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EHAAT redirects here For the air ambulance service see Essex amp Herts Air Ambulance Height above average terrain HAAT or less popularly effective height above average terrain EHAAT is the vertical position of an antenna site is above the surrounding landscape HAAT is used extensively in FM radio and television as it is more important than effective radiated power ERP in determining the range of broadcasts VHF and UHF in particular as they are line of sight transmissions For international coordination it is officially measured in meters even by the Federal Communications Commission in the United States as Canada and Mexico have extensive border zones where stations can be received on either side of the international boundaries Stations that want to increase above a certain HAAT must reduce their power accordingly based on the maximum distance their station class is allowed to cover see List of North American broadcast station classes for more information on this The FCC procedure to calculate HAAT is from the proposed or actual antenna site either 12 or 16 radials were drawn and points at 2 4 6 8 and 10 miles 16 km radius along each radial were used The entire radial graph could be rotated to achieve the best effect for the station The altitude of the antenna site minus the average altitude of all the specified points is the HAAT This can create some unusual cases particularly in mountainous regions it is possible to have a negative number for HAAT the transmitter would not be located underground but rather in a valley with hills on both sides taller than the transmitter itself for example The FCC has divided the Contiguous United States into three zones for the determination of spacing between FM and TV stations using the same frequencies FM and TV stations are assigned maximum ERP and HAAT values depending on their assigned zones to prevent co channel interference FM broadcast zones in the U S The FCC regulations for ERP and HAAT are listed under Title 47 Part 73 of the Code of Federal Regulations CFR Contents 1 FM 1 1 Zones I and I A 1 2 Zones II and III 2 TV 2 1 Maximum HAAT 2 2 Minimum co channel separation 3 Zone layouts 4 See also 5 External linksFM EditZones I and I A Edit Maximum HAAT 150 metres 492 ft 2 in Maximum ERP 50 kilowatts 47dBW Minimum co channel separation 241 km 150 mi Zones II and III Edit Maximum HAAT 600 metres 1 968 ft 6 in Maximum ERP 100 kilowatts 50dBW Minimum co channel separation 290 km 180 mi TV EditIn all zones maximum ERP for analog TV transmitters is as follows VHF 2 6 100 kilowatts 50dBW analog 45 kilowatts 46 5dBW digital VHF 7 13 316 kilowatts 55dBW analog 160 kilowatts 52dBW digital UHF 5 000 kilowatts 67dBW analog 1 000 kilowatts 60dBW digital Maximum HAAT Edit Zone I 305 metres 1 000 ft 8 in Zones II and III 610 metres 2 001 ft 4 in Minimum co channel separation Edit Band Zone I Zone II Zone IIIVHF 272 7 km 169 5 miles 304 9 km 189 5 miles 353 2 km 219 5 miles UHF 248 6 km 154 5 miles 280 8 km 174 5 miles 329 0 km 204 5 miles Zone layouts EditZone I the most densely populated zone consists of the entire land masses of the following states Connecticut Delaware Illinois Indiana Maryland Massachusetts New Jersey Ohio Pennsylvania Rhode Island and West Virginia in addition to the northern and eastern portions of Virginia the areas of Michigan and southeastern Wisconsin south of 43 30 north latitude the coastal strip of Maine the areas of New Hampshire and Vermont south of 45 north latitude and the areas of western New York south of 43 30 north latitude and eastern New York south of 45 north latitude In addition Zone I A FM only consists of all of California south of 40 north latitude Puerto Rico and the U S Virgin Islands If the dividing line between Zones I and II runs through a city that city is considered to be in Zone I Zones I and I A have the most grandfathered overpowered stations which are allowed the same extended coverage areas that they had before the zones were established One of the most powerful of these stations is WBCT in Grand Rapids Michigan which operates at 320 000 watts and 238 meters 781 ft HAAT Zone III the zone with the flattest terrain consists of all of Florida and the areas of Alabama Georgia Louisiana Mississippi and Texas within approximately 241 4 kilometers 150 0 mi of the Gulf of Mexico Zone II is all the rest of the Continental United States Alaska and Hawaii See also EditAbove mean sea level AMSL Above ground level AGL Canadian Radio television and Telecommunications Commission CRTC List of broadcast station classes Topographic prominence a similar measurement for mountains United States Federal Communications Commission FCC External links Edit47 CFR Part 73 Index 2005 FCC Mass Media Calculated Contours FCC HAAT Calculator Superpower Grandfathered FM stations Retrieved from https en wikipedia org w index php title Height above average terrain amp oldid 1033359314, wikipedia, wiki, book, books, library,
